A Strong Core for a Strong Recovery: A Scoping Review of Methods to Improve Trunk Control and Core Stability of People with Different Neurological Conditions

Abstract

Objective: The purpose of this scoping review is to provide valuable insights for clinicians and researchers for designing rehabilitative interventions targeting the trunk and core for individuals who have experienced traumatic events, such as stroke or spinal cord injury, or are grappling with neurological diseases such as multiple sclerosis and Parkinson’s disease. We investigated training methods used to enhance balance, trunk control, and core stability. Methods: We conducted an extensive literature search across several electronic databases, including Web of Science, PubMed, SCOPUS, Google Scholar, and IEEE Xplore. Results: A total of 109 articles met the inclusion criteria and were included in this review. The results shed light on the diversity of rehabilitation methods that target the trunk and core. These methods have demonstrated effectiveness in improving various outcomes, including balance, trunk control, gait, the management of trunk muscles, overall independence, and individuals’ quality of life. Conclusions: Our scoping review provides an overview on the methods and technologies employed in trunk rehabilitation and core strengthening, offering insights into the added value of core training and specific robotic training, focusing on the importance of different types of feedback to enhance training effectiveness.

1. Introduction

Maintaining balance is crucial for daily life and long-term health [1]. Whether we are still or moving, maintaining an upright trunk posture is essential for many activities, such as eating, dressing, and using electronic devices. Postural control is the ability to maintain the body in space and achieve both stability and orientation goals [2]. It is a complex sensorimotor skill [1], which involves the processing of sensory information [3] that also needs to be integrated with the central nervous system to proficiently plan, control, and execute correct movements [4].

To achieve good postural control, proper control of the trunk and core stability are essential. Although the terms “trunk” and “core” are often used interchangeably, they have different meanings [5]. The trunk refers to the human body apart from the head, neck, and limbs, while the core extends from the sternum down to the pubic bone, including every muscle surrounding the lumbar spine and pelvis, such as the abdominal, back, and hip muscles [5].

Core stability refers to the ability to control and stabilize the spine and pelvis during movements [5,6], whereas trunk control refers to the ability to move and control the upper body in relation to the lower body. The former primarily involves the muscles around the lumbar spine and pelvis, whereas the latter involves the entire trunk, including the chest and shoulders. The close connection between trunk control and core stability stems from their dependence on synchronized muscle group activations [7]. Both play a vital role in facilitating functional body movements [5] and maintaining sitting balance [1].

Several factors affect our ability to appropriately control the trunk and core muscles, including neurological diseases, musculoskeletal injuries, and ageing [5]. These factors affect either the central nervous system or peripheral structures or impair the communication between them.

Neurodegenerative disorders are responsible for a gradual, or sometimes rapid, worsening of postural abilities, while traumatic events cause sudden damage affecting these abilities. Traumatic events include spinal cord injuries (SCI) and stroke, both of which affect the central nervous system. The former occurs at the level of the spine, resulting in partial or total loss of sensation and motor functions below the level of the injury, while the latter affects a specific region of the brain, causing impairments in movement and sensation. In contrast, Parkinson’s disease (PD) is primarily caused by the gradual degeneration of the basal ganglia [8]. Specifically, the degeneration of dopaminergic neurons in the substantia nigra pars compacta triggers a cascade of functional changes that affect the whole basal ganglia network, resulting in tremors, body rigidity, and instability [8]. In multiple sclerosis (MS), the gradual demyelination of nerve fibers in the central nervous system, in addition to pain, tingling, and numbness in the limbs, causes a slowdown in the exchange of information between the brain and muscles, resulting in muscle weakness coupled with a range of motor and sensory impairments [9]. Despite different causes, these conditions share common deficits related to core stability and trunk control [10]. These deficits include difficulty in maintaining an upright posture, as well as problems with correctly perceiving the position of the body in space and reacting to self-generated changes or unexpected disturbances, muscle weakness, and difficulty in selectively activating muscles, often leading to body asymmetries, with a direct impact on the functional activities of daily living [11,12,13,14].

Rehabilitation programs that focus on enhancing core stability, trunk control, and sitting balance have the potential to assist individuals in restoring their capacity to sit and engage in activities with enhanced comfort and self-assurance [15,16]. These rehabilitation programs are diverse in terms of the exercises, equipment, and approaches employed to address these impairments. While certain programs concentrate on muscle strengthening, others prioritize motor learning and sensory integration to enhance sitting balance. Furthermore, various equipment options, including stability balls, balance boards, and innovative technological devices, can be used to provide challenges and promote skill improvement in these areas [16].

Rehabilitation programs targeting core stability, trunk control, and sitting balance are key topics in clinical settings, but they have also attracted widespread attention within the research community. Different reviews [15,17,18,19,20] focused on the effect of core stability exercises or their integration into rehabilitation programs for stroke survivors. Van Criekinge et al. [15] investigated the effectiveness of trunk training in trunk control, sitting and standing balance, and mobility. The results of this review highlight the potential benefits of core training in improving trunk control and balance. Similarly, the efficacy of specific trunk mobility exercises has been explored in PD [21].

Despite this topic being of great interest, to the best of our knowledge, there is a lack of studies exploring the methods used to improve core stability, trunk control, and, consequently, sitting balance. Also, most of the existing studies consider a single pathology per time; differently, here we include a set of disorders that can share some common rehabilitative methods when considering trunk and core training. In addition, we believe that exploring technological solutions and devices that fit this context would be highly valuable for scientific and clinical communities.

Herein, we propose a scoping review aimed at mapping the existing literature on sitting balance training, including both conventional and technology-based methods. We aim to gather information on the different types of interventions and equipment designed to improve core stability and trunk control in people following traumatic events or who are suffering from neurological diseases.

2. Methods

This scoping review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis extension for Scoping Reviews (PRISMA-ScR) [22,23]. The research question was formulated using a patient/population, intervention/indicator, comparison/control, and outcome (PICO) framework:

Population: adults following traumatic events, such as stroke or SCI, or suffering from neurological diseases, such as MS and PD;

Intervention: any rehabilitative method specifically targeting core stability, trunk control, and/or sitting balance;

Comparison: no restriction on comparison if the study included at least two assessments—one at the beginning and one at the end of the rehabilitation;

Outcome: evaluation of balance control, trunk control, mobility, quality of life, perceived quality of life, independence, and gait.

2.1. Search Strategy

The literature search was performed using the following electronic databases: PubMed, SCOPUS, Google Scholar, IEEE Xplore, and Web of Science. All electronic databases were searched using a combination of the following keywords: trunk control, core stability, sitting balance, stroke, SCI, MS, PD, rehabilitation, training, exercises, traditional, technology, robotic, wearable, sensors, platform, and IMU. After removing duplicates, the process involved screening potentially relevant articles by first examining their titles and abstracts. Subsequently, the full texts of the remaining studies were carefully screened and compared to the inclusion criteria. Additionally, the reference lists of the selected articles and reviews on similar topics were scanned to uncover other potentially relevant studies.

2.2. Eligibility Criteria and Selection

The PICO framework was used to define the inclusion criteria. The identified inclusion criteria were as follows:

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Population: Adult population without sex or ethnicity restrictions, with a clinical diagnosis of PD, MS, stroke, or SCI, as well as with trunk postural control or core stability impairments. There were no limitations on the level of injury or the stage of the pathology.

-

Intervention: Studies that proposed physiotherapy intervention (conventional, non-conventional, or based on technological solutions) oriented to improve trunk and/or core functional impairments. The intervention should last more than one day.

-

Outcome: Rehabilitation studies focused on trunk control, core strengthening, or sitting balance.

The exclusion criteria were also defined as follows:

-

Population: single case studies, studies with less than five subjects, and studies targeting populations other than the defined groups;

-

Intervention: studies with single-day training;

-

Outcome: rehabilitation studies focusing solely on balance or limbs without specific emphasis on trunk control and core stability.

Also, studies still under review (i.e., we excluded the grey literature), studies testing the reliability of systems; and studies solely focused on assessment methods were excluded. Furthermore, studies that proposed protocols aligned with the defined purposes were included.

Databases were searched until May 2023, focusing only on the last 20 years of technological solutions.

3. Results

3.1. Study Selection

The initial literature search across the electronic databases yielded a total of 3514 articles. We removed 458 duplicate articles within and between the databases, resulting in 3056 articles for screening. After reviewing the titles and abstracts, we excluded 2811 articles. In addition, we included ten articles from other sources. The remaining 255 articles were considered eligible for this study. Of these, 13 articles were excluded due to the unavailability of the full text, presentation of reviews, or long abstracts. The remaining 242 full-text articles were independently analyzed by two reviewers based on the inclusion and exclusion criteria. The conflicts were resolved by a third reviewer.

In brief, 12 studies were removed as they tested less than five subjects; 20 did not target PD, MS, SCI, or stroke subjects; 2 tested the reliability of a system; 27 did not present any type of training; 56 did not explicitly target core rehabilitation, trunk control, or sitting balance; 3 presented outdated technologies; 5 presented protocols that also published results; 1 was a single case study; and 7 were single-session studies. As a result, 109 articles met the inclusion criteria and were included in the review (see Figure 1 for more details).

3.2. Study Characteristics

We divided the selected studies into two categories: (i) studies with different designs, including both single-group pre-test/post-test trials and Randomized Clinical Trials (RCTs), and (ii) protocols for RCT (i.e., registered studies that are in progress, whose results have not been published yet).

Table 1. Studies with different designs, including both single-group pre-test/post-test trials and RCT. v: There was an improvement between PRE and POST training. v +: the improvement was larger than that in the other groups. x: no improvement between PRE and POST. SCI: Spinal Cord Injury; PD: Parkinson’s disease, MS: multiple sclerosis, SG: single-group, VRT: virtual reality training, T: training, ES: electrical stimulation, PNF: proprioceptive neuromuscular facilitation.

Title	Group	Target Population	Type of Training	Standing Balance	Sitting Balance	Gait	Trunk/Core Control	Trunk Muscle Activity	ADL/QoL
The effects of additional core stability exercises on improving dynamic sitting balance and trunk control for subacute stroke patients: a randomized controlled trial [6]	Experimental	Stroke	Conventional T + core stability T	v +	v +	v +	v +
	Control		Conventional T	v	v	v	v
Effects of trunk control training on dynamic sitting balance and trunk function in hemiplegia patients after acute stroke [24]	Experimental	Stroke	Low-intensity conventional T + high-intensity trunk control T	v	v +				v
	Control		Low-intensity conventional T	v	v				v
Combined effect of virtual reality training (VRT) and conventional therapy on sitting balance in patients with spinal cord injury (SCI): randomized control trial [25]	Experimental	SCI	Conventional T + VRT in sitting		v		v +
	Control		Conventional T		v		v
Effect of acupuncture at Huatuo Jiaji (EX-B2) combined with core muscle training on motor function of lower limbs in patients with hemiplegia after stroke [26]	Experimental	Stroke	Acupuncture + core muscle T	v				v +	v
	Control 1		Core muscle T	v				v	v
	Control 2		Acupuncture	v				v	v
Use of virtual reality and videogames in the physiotherapy treatment of stroke patients: a pilot randomized controlled trial [27]	Experimental	Stroke	Conventional T + VRT	v		x	v
	Control		Conventional T	x		x	x
Effect of task-specific training on trunk control and balance in patients with subacute stroke [28]	Experimental	Stroke	task-specific T	v +			v +
	Control		Conventional T	v			v
Effect of core stability training on trunk function, standing balance, and mobility in stroke patients [29]	Experimental	Stroke	Conventional stability T	v		v	v
	Control		Conventional T	x		x	x
Effects of intensive multiplanar trunk training coupled with dual-task exercises on balance, mobility, and fall risk in patients with stroke: a randomized controlled trial [30]	Experimental	Stroke	High-intensity multiplanar trunk T + dual-task T	v +	v +	v +	v +
	Control		Conventional trunk T	v	v	v	v
Weight-shift training improves trunk control, proprioception, and balance in patients with chronic hemiparetic stroke [31]	Experimental	Stroke	Weight-shift T + conventional T		v +	v +
	Control		Conventional T		x	v
Short-term effects of core stability training on the balance and ambulation function of individuals with chronic spinal cord injury: a pilot randomized controlled trial [32]	Experimental	SCI	Core stability T on an unstable support surface	v +		v +
	Control		Core stability T on a stable support surface	v		v
Core stability exercises yield multiple benefits for patients with chronic stroke: a randomized controlled trial [33]	Experimental 1	Stroke	Core stability T on unstable support surfaces				v	v
	Experimental 2		Core stability T on stable support surfaces				v	v
	Control		Conventional T				x	x
The effect of the rehabilitation program on balance, gait, physical performance, and trunk rotation in Parkinson’s disease [34]	Experimental	PD	Multidisciplinary T	v		v	v
	Control		No T	x		x	x
Effects of trunk exercise on unstable surfaces in persons with stroke: a randomized controlled trial [35]	Experimental	Stroke	Conventional T + trunk T on unstable surfaces		v	v	v
	Control		Conventional T + upper limb T		v	x	x
Comparison of aquatic therapy vs. dry-land therapy to improve mobility of chronic stroke patients [36]	Experimental	Stroke	Ai Chi aquatic T + dry-land T	v		v
	Experimental		Ai Chi aquatic T	v		v
	Control		Dry-land T focused on walking and trunk mobility	v		v
Best core stabilization for anticipatory postural adjustment and falls in hemiparetic stroke [37]	Experimental	Stroke	DNS T	v			v	v +
	Control		Core stability T	v			v	v
Tailored sitting Tai Chi program for subacute stroke survivors: a randomized controlled trial [38]	Experimental	Stroke	Sitting Tai Chi	v	v				v
	Control		Attention control group	x	x				x
Land-based and aquatic trunk exercise program to improve trunk control, balance, and activities of daily living ability in stroke: a randomized clinical trial [39]	Experimental	Stroke	Conventional T + land-based and aquatic trunk T	v +	v +		v +
	Control		Conventional T	v	v		v
Influence of core-stability exercises guided by a telerehabilitation app on trunk performance, balance and gait performance in chronic stroke survivors: a preliminary randomized controlled trial [40]	Experimental	Stroke	Conventional T + home-based core-stability T (including trunk T on unstable surfaces)	v	v		v
	Control		Conventional T	v	x		x
Effect of trunk stabilization exercise on abdominal muscle thickness, balance and gait abilities of patients with hemiplegic stroke: a randomized controlled trial [41]	Experimental 1	Stroke	Conventional T + trunk stability T (hollowing maneuver)	v		v		v
	Experimental 2		Conventional T + trunk stability T (bracing maneuver)	v		v		v
	Control		Conventional T	v		v		x
Effects of dynamic core-postural chain stabilization on diaphragm movement, abdominal muscle thickness, and postural control in patients with subacute stroke: a randomized control trial [42]	Experimental 1	Stroke	Neurodevelopmental T	v				v
	Experimental 2		DNS T	v +				v +
The effects of Bobath-based trunk exercises on trunk control, functional capacity, balance, and gait: a pilot randomized controlled trial [43]	Experimental	Stroke	Personalized T	v		v	v
	Control		Strengthening, stretching, ROM, and mat T	x		v	v
SWEAT2 study: effectiveness of trunk training on muscle activity after stroke. A randomized controlled trial [44]	Experimental	Stroke	Conventional T + trunk T					v
	Control		Conventional T + cognitive T					x
Four-week trunk-specific exercise program decreases forward trunk flexion in Parkinson’s disease: a single-blinded, randomized controlled trial [45]	Experimental	PD	Active self-correction T with visual and proprioceptive feedback, passive, and active trunk stabilization T	v +			v +		v
	Control		Conventional T	v			v		v
Core stability-based balance training and kinesio taping for balance, trunk control, fear of falling, and walking capacity in patients with multiple sclerosis: a randomized single-blind study [46]	Experimental	MS	Core stability balance T + Kinesio taping on global trunk muscles	v		v	v
	Control		Core stability balance T	v		v	v
Dynamic stability and trunk control improvements following robotic balance and core stability training in chronic stroke survivors: a pilot study [16]	Experimental	Stroke	Robotic T (hunova)	v +			v +
	Control		Conventional T	v			v
The effectiveness of driving game on trunk control and gait ability in stroke [47]	Experimental	Stroke	Conventional T + driving-based interactive video games (VRT)		v +	v +
	Control		Conventional T + treadmill		v	v
Sitting balance exercise performed using virtual reality training on a stroke rehabilitation inpatient service: a randomized controlled study [48]	Experimental	Stroke	VRT requiring trunk movements		v
	Control		VRT with trunk restrained		v
Feasibility of dance therapy using telerehabilitation on trunk control and balance training in patients with stroke: a pilot study [49]	Experimental	Stroke	Conventional T + telerehabilitation (zoom) dance T		v	x	v
	Control		Conventional T		x	v	v
Effects of robot-assisted trunk control training on trunk control ability and balance in patients with stroke: a randomized controlled trial [50]	Experimental	Stroke	Conventional trunk stabilization T based on the Bobath concept + robotic T	v +			v +
	Control		Conventional trunk stabilization T based on the Bobath concept + stretching	v			v
Progressive respiratory muscle training for improving trunk stability in chronic stroke survivors: a pilot randomized controlled trial [51]	Experimental	Stroke	Respiratory muscle T + trunk stabilization T				v +
	Control		Trunk stabilization T				v
SWEAT2 study: effectiveness of trunk training on gait and trunk kinematics after stroke: a randomized controlled trial [52]	Experimental	Stroke	Conventional T + trunk T		v	v +	v
	Control		Conventional T + cognitive T		x	v	x
The effects of the three-dimensional active trunk training exercise on trunk control ability, trunk muscle strength, and balance ability in sub-acute stroke patients: a randomized controlled pilot study [53]	Experimental	Stroke	Robotic trunk T	v +			v +	v +
	Control		Trunk T	v			v	v
Effects of trunk rehabilitation with kinesio and placebo taping on static and dynamic sitting postural control in individuals with chronic stroke: a randomized controlled trial [54]	Experimental	Stroke	Trunk T + kinesio taping		v +		v
	Control		Trunk T + placebo taping		v		v
Technology-supported sitting balance therapy versus usual care in the chronic stage after stroke: a pilot randomized controlled trial [55]	Experimental	Stroke	Conventional T + robotic T	v +		v +	v +
	Control		Conventional T	v		v	v
Home-based exercise using balance disc and smartphone inclinometer application improves balance and activity of daily living in individuals with stroke: a randomized controlled trial [56]	Experimental	Stroke	Traditional + multidirectional home-based T	v +
	Control		Traditional home-based T	v
Effects of early bedside arm and leg cycle ergometry on sitting and standing ability in hospitalized acute stroke patients: a randomized controlled trial [57]	Experimental	Stroke	Arm and leg cycle ergometry + conventional T	v			v
	Control		Conventional T	v			v
Comparative effect of Liuzijue Qigong and conventional respiratory training on trunk control ability and respiratory muscle function in patients at an early recovery stage from stroke: a randomized controlled trial [58]	Experimental	Stroke	Conventional T + Liuzijue exercise		v +		v	v +	v +
	Control		Conventional T + respiratory T		v		v	v	v
Effects of EMG-triggered FES during trunk pattern in PNF on balance and gait performance in persons with stroke [59]	Experimental	Stroke	Functional ES during PNF trunk pattern	v		v	v
	Control		PNF trunk pattern	v		v	v
Effect of sensory training of the posterior thigh on trunk control and upper extremity functions in stroke patients [60]	Experimental	Stroke	Neurodevelopmental T + sensory T on the posterior thigh (TENS + vibrations + manual passive joints mobilization)	v			v
	Control		Neurodevelopmental T	v			v
Effectiveness of robotic balance training on postural instability in patients with mild Parkinson’s disease: a pilot, single-blind, randomized controlled trial [61]	Experimental	PD	Robotic T	v +		v			v
	Control		Conventional T	v		v			v
Trunk exercises improve balance in Parkinson’s disease: a phase II randomized controlled trial [62]	Experimental	PD	Trunk T	v +
	Control		Education	v
Efficacy of trunk regimes on balance, mobility, physical function, and community reintegration in chronic stroke: a parallel-group randomized trial [63]	Experimental	Stroke	Plinth-based trunk T	v			v
	Experimental		Swiss ball-based trunk T	v			v
	Control		Conventional T	x			x
Effects of diagonally aligned sitting training with a tilted surface on sitting balance for low sitting performance in the early phase after stroke: a randomised controlled trial [64]	Experimental	Stroke	Trunk T on a tileted surface				v +
	Control		Trunk T on an horizontal surface				v
Upper limbs cycle ergometer increases muscle strength, trunk control and independence of acute stroke subjects: a randomized clinical trial [65]	Experimental	Stroke	Conventional T + upper limb cycle ergometer				v +
	Control		Conventional T				v
Does training sitting balance on a platform tilted 10° to the weak side improve trunk control in the acute phase after stroke? A randomized controlled trial [66]	Experimental	Stroke	Trunk T on a tileted surface				v +
	Control		Trunk T on a horizontal surface				v
Smartphone-based visual feedback trunk control training using a gyroscope and mirroring technology for stroke patients: single-blind, randomized clinical trial of efficacy and feasibility [67]	Experimental	Stroke	Conventional T + smartphone-based visual feedback trunk control T	v +		v +	v +
	Control		Conventional T	v		v	v
Effects of a sitting boxing program on upper limb function, balance, gait, and quality of life in stroke patients [68]	Experimental	Stroke	Conventional T + sitting boxing	v +		v +			v +
	Control		Conventional T	v		v			v
The effect of additional neuromuscular electrical stimulation applied to erector spinae muscles on functional capacity, balance, and mobility in post-stroke patients [69]	Experimental	Stroke	Conventional T + neuromuscular ES	v +		v			v
	Control		Conventional T	v		v			v
Effects of dynamic sitting exercise with delayed visual feedback in the early post-stroke phase: a pilot double-blinded randomized controlled trial [70]	Group 1	Stroke	Conventional T + dynamic sitting T with delayed visual feedback	v			v
	Group 2		Conventional T + dynamic sitting T with real-time visual feedback	v			v
Comparison of physio ball and plinth trunk exercises regimens on trunk control and functional balance in patients with acute stroke: a pilot randomized controlled trial [71]	Experimental	Stroke	Task-specific trunk T on an unstable surface	v +			v +
	Control		Task-specific trunk exercises on a stable surface	v			v
The effect of a whole-body vibration therapy on the sitting balance of subacute stroke patients: a randomized controlled trial [72]	Experimental	Stroke	Conventional T + whole-body vibration	v		v
	Control		Conventional T + sitting balance T	v		v
Effect of three-dimensional spine stabilization exercise on trunk muscle strength and gait ability in chronic stroke patients: a randomized controlled trial [73]	Experimental	Stroke	Robotic spine stability T			v +		v +
	Control		Spine stability T throughout the Bridge exercises			v		v
Clinical feasibility of the Nintendo Wii™ for balance training post-stroke: a phase II randomized controlled trial in an inpatient setting [74]	Group 1	Stroke	Balance Group: standing T with the ‘Wii Fit Plus’	v
	Group 2		Upper Limb Group: using the ‘Wii Sports/Sports Resort’ in sitting	x
Comparing routine neurorehabilitation program with trunk exercises based on bobath concept in multiple sclerosis: pilot study [75]	Experimental	MS	Trunk T based on the Bobath concept + balance and coordination T	v			v
	Control		Conventional T + balance and coordination T	v			v
Effects of trunk stabilization exercises using laser pointer visual feedback in patients with chronic stroke: a randomized controlled study [76]	Experimental	Stroke	Conventional T + trunk stabilization T using laser pointer visual feedback	v +		v +
	Control		Conventional T + trunk stabilization T	v		v
Comparing the effects of short-term Liuzijue exercise and core stability training on balance function in patients recovering from stroke: a pilot randomized controlled trial [77]	Experimental	Stroke	Conventional T + Liuzijue Qigong	v +	v +				v +
	Control		Conventional T + core stability T	v	v				v
Group-based individualized comprehensive core stability intervention improves balance in persons with multiple sclerosis: a randomized controlled trial [78]	Experimental	MS	Individualized, group-based, comprehensive core stability T	v +			v +
	Control		Conventional T	v			v
Effects of inspiratory muscle training on respiratory muscle strength, trunk control, balance, and functional capacity in stroke patients: a single-blind randomized controlled study [79]	Experimental	Stroke	Neurodevelopmental T + inspiratory muscle T	v		x	v
	Control		Neurodevelopmental T	v		x	x
Effects of trunk stabilization training robot on postural control and gait in patients with chronic stroke: a randomized controlled trial [80]	Experimental	Stroke	Conventional T + robotic T	v +		v
	Control		Conventional T	v		v
Smartphone-based visual feedback trunk control training for gait ability in stroke patients: a single-blind randomized controlled trial [81]	Experimental	Stroke	Conventional T + visual feedback trunk control T			v +	v +
	Control		Conventional T			v	v
The effects of visual feedback training on sitting balance ability and visual perception of patients with chronic stroke [82]	Experimental	Stroke	Conventional T+ visual feedback T		v
	Control		Conventional T		x
Postural rehabilitation and kinesio taping for axial postural disorders in Parkinson’s disease [83]	Experimental 1	PD	Proprioceptive and tactile stimulation combined with stretching and postural re-education	v		v	v
	Experimental 2		Proprioceptive and tactile stimulation combined with stretching and postural re-education + kinesio taping	v		v	v
	Control		No T	x		x	x
The effects of 10-week core stability training on balance in women with multiple sclerosis according to Expanded Disability Status Scale: a single-blind randomized controlled trial [84]	Experimental	MS	Core stability T	v +				v +
	Control		Conventional T	v				v
The effect of wheelchair Tai Chi on balance control and quality of life among survivors of spinal cord injuries: a randomized controlled trial [85]	Experimental	SCI	Wheelchair Tai Chi	v +			x		v +
	Control		conventional T	v			x		v
Efficacy of a technology-based client-centred training system in neurological rehabilitation: a randomized controlled trial [86]	Experimental	Central nervous system deficits (mainly stroke)	Conventional T + T with kinect				v		v
	Control		Conventional T				v		v
The effects of Mat Pilates and Reformer Pilates in patients with multiple sclerosis: a randomized controlled study [87]	Experimental 1	MS	Mat Pilates	v		v	v	v	v
	Experimental 2		Reformer Pilates	v		v	v	v +	v
	Control		Breathing and relaxation T at home	x		x	x	x	x
Investigating the dose-related effects of video game trunk control training in chronic stroke patients with poor sitting balance [88]	Experimental 1	Stroke	Conventional T + low-dose (5 times/week) robotic T	v		v	v
	Experimental 2		Conventional T + high-dose (10 times/week) robotic T	v		v	v +
Effect of core stabilization exercises in addition to conventional therapy in improving trunk mobility, function, ambulation and quality of life in stroke patients: a randomized controlled trial [89]	Experimental	Stroke	Conventional T + core stability T			v	v +
	Control		Conventional T			v	v
Speed-interactive pedaling training using smartphone virtual reality application for stroke patients: single-blind, randomized clinical trial [90]	Experimental	Stroke	Cycle T with speed-interactive pedaling T + conventional T	v +		v	v +
	Control		Cycle T + conventional T	v		x	v
Audiovisual biofeedback-based trunk stabilization training using a pressure biofeedback system in stroke patients: a randomized, single-blind study [91]	Experimental	Stroke	Audiovisual biofeedback-based trunk stabilization T		v +		v +	v
	Control		Trunk stabilization T		v		v	x
Effects of proprioceptive neuromuscular facilitation neck pattern exercise on the ability to control the trunk and maintain balance in chronic stroke patients [92]	Experimental	Stroke	PNF neck pattern T	v	v		v +
	Control		Conventional T	v	v		v
Effects of three-dimensional lumbar stabilization training for balance in chronic hemiplegic stroke patients: a randomized controlled trial [93]	Experimental	Stroke	Robotic T (3D spine balance system)	v	v	v +	v +	v
	Control		Robotic T (Biodex balance system)	v	v	v	v	v
Therapeutic effects of reaching with forward bending of trunk on postural stability, dynamic balance, and gait in individuals with chronic hemiparetic stroke [94]	Experimental	Stroke	Conventional T + trunk T	v		v
	Control		Conventional T	x		x
The effect of the inspiratory muscle training on functional ability in stroke patients [95]	Experimental	Stroke	Neuro-developmental T + inspiratory T			v	v +
	Control		Neuro-developmental T			x	v
Canoe game-based virtual reality training to improve trunk postural stability, balance, and upper limb motor function in subacute stroke patients: a randomized controlled pilot study [96]	Experimental	Stroke	Conventional T + VRT	v +			v +
	Control		Conventional T	v			v
Effects of pilates and elastic taping on balance and postural control in early stage Parkinson’s disease patients: a pilot randomised controlled trial [97]	Experimental 1	PD	Pilates T	x		v
	Experimental 2		Pilates T + elastic taping	v		v
	Control		Conventional T	x		x
Effects of rehabilitation training of core muscle stability on stroke patients with hemiplegia [98]	Experimental	Stroke	Conventional T + core muscle T	v +				v
	Control		Conventional T	v				x
Role of virtual reality in balance training in patients with spinal cord injury: a prospective comparative pre–post study [99]	Experimental	SCI	Conventional T + semi-immersive VRT (Rhetoric with kinect)	v			v
	Control		Conventional T	v			v
Effects of sling exercise therapy on trunk muscle activation and balance in chronic hemiplegic patients [100]	Experimental	Stroke	Sling exercise T	v				v
	Control		Conventional T on a mat	v				v
Sitting Tai Chi improves the balance control and muscle strength of community-dwelling persons with spinal cord injuries: a pilot study [101]	Experimental	SCI	Sitting Tai Chi T + sitting balance T		v
	Control		Education		x
The additive effects of core muscle strengthening and trunk NMES on trunk balance in stroke patients [102]	Experimental 1	Stroke	Core muscle T	v			v
	Experimental 2		Trunk neuromuscular ES	v			v
	Experimental 3		Core muscle T + trunk neuromuscular ES	v +			v +
Effect of indoor wheelchair curling training on trunk control of person with chronic spinal cord injury: a randomised controlled trial [103]	SG (crossover design)	SCI	Wheelchair curling T				v
Effects of trunk stabilization exercises on different support surfaces on the cross-sectional area of the trunk muscles and balance ability [104]	Experimental 1	stroke	Trunk control T performed on a stable support surface	v			v
	Experimental 2		Trunk control T performed on an unstable support surface	v			v
Effectiveness of pelvic proprioceptive neuromuscular facilitation techniques on balance and gait parameters in chronic stroke patients: a randomized clinical trial [105]	Experimental	Stroke	Pelvic PNF + task-oriented T	v +		v +
	Control		Task-oriented T	v		v
Proprioceptive neuromuscular facilitation neck pattern and trunk specific exercise on trunk control and balance—an experimental study [106]	Experimental	Stroke	PNF trunk-specific T	v +			v +
	Control		Conventional T	v			v
Comparison of the effects of an exergame-based program with conventional physiotherapy protocol based on core areas of the european guideline on postural control, functional mobility, and quality of life in patients with Parkinson’s disease: randomized clinical trial [107]	Experimental	PD	VRT	v					v
	Control		Conventional core T	v					v
Efficacy of core stability versus task oriented trainings on balance in ataxic persons with multiple sclerosis. A single-blind randomized controlled trial [9]	Experimental 1	MS	Conventional balance T + task oriented T	v +
	Experimental 2		Conventional balance T + core stability T	v
	Control		Conventional balance T	v
The effects of clinical pilates training on walking, balance, fall risk, respiratory, and cognitive functions in persons with multiple sclerosis: a randomized controlled trial [108]	Experimental	MS	Pilates T + home T program	v +	v +	v	v +
	Control		Home T reflecting conventional T	v	v		v
Trunk exercises performed on an unstable surface improve trunk muscle activation, postural control, and gait speed in patients with stroke [109]	Experimental	Stroke	Trunk T on a balance pad			v	v	v +
	Control		Trunk T on a stable surface			v	v	v
Effects of trunk control robot training on balance and gait abilities in persons with chronic stroke [110]	Experimental	stroke	Robotic T	v +		v
	Control		Trunk extension t	v		x
Training unsupported sitting in people with chronic spinal cord injuries: a randomized controlled trial [111]	Experimental	SCI	Task-specific unsupported T				v +
	Control		No T				v
Effects on balance and walking with the CoDuSe balance exercise program in people with multiple sclerosis: a multicenter randomized controlled trial [112]	Experimental	MS	Balance T (CoDuSe)	v +		v
	Control		No T	v		x
The effects of core stability strength exercise on muscle activity and trunk impairment scale in stroke patients [113]	Experimental	Stroke	Conventional T + core stability T				v	v
	Control		Conventional T				x	x
Impact of trunk resistance and stretching exercise on fall-related factors in patients with Parkinson’s disease: a randomized controlled pilot study [114]	Experimental	PD	Progressive trunk resistance and stretching T	v		v	v
	Control		No T	x		x	x
Effect of innovative vs. usual care physical therapy in subacute rehabilitation after stroke. A multicenter randomized controlled trial [115]	experimental	Stroke	Comprehensive low-cost physical T, I-CoreDIST	v		v	v
	Control		Conventional T	v		v	v
Efficacy of robot-assisted gait training combined with robotic balance training in subacute stroke patients: a randomized clinical trial [116]	Experimental	Stroke	Robotic T (G-EO + hunova)	v		v	v		v
	Control		Robotic T (G-EO)	v		v	x		v
Balance exercise program reduced falls in people with multiple sclerosis: a single-group, pre-test–post-test trial [117]	SG (Pre/Post-test)	MS	Balance T (CoDuSe)	v
Balance exercise facilitates everyday life for people with multiple sclerosis: a qualitative study [118]	SG (qualitative study)	MS	Balance T (CoDuSe)				v	v	v
Activity-based therapy in a community setting for independence, mobility, and sitting balance for people with spinal cord injuries [119]	SG (observational retrospective)	SCI	Task-specific T, weight-bearing T, and muscle strengthening (with different technologies)		v				v
Combined transcutaneous electrical spinal cord stimulation and task-specific rehabilitation improves trunk and sitting functions in people with chronic tetraplegia [120]	SG (pilot study)	SCI	ES + conventional task-specific T				v	v
A novel assistive therapy chair to improve trunk control during neurorehabilitation: perceptions of physical therapists and patients [121]	SG (observational pilot study)	Stroke	Robotic T (T-Chair) + conventional T				v
Arm crank ergometer spin training improves seated balance and aerobic capacity in people with spinal cord injury [122]	SG (Pret/Post-test)	SCI	Spin T		v (EC)			v
Improving upper extremity strength, function, and trunk stability using wide-pulse functional electrical stimulation in combination with functional task-specific practice [123]	Prospective case series	SCI	Functional ES + functional task-specific practice				v
The effect of functional electrical stimulation and therapeutic exercises on trunk muscle tone and dynamic sitting balance in persons with chronic spinal cord injury: a crossover trial [124]	SG (crossover design)	SCI	Exercises with functional ES		v			v

and

Table 2. Protocols for RCT.

Title	Population	Goal	Control Group	Experimental Group	Assessment
Effect of dynamic neuromuscular stabilization on balance and trunk function in people with multiple sclerosis: protocol for a randomized control trial [125]	MS	To evaluate the effectiveness of dynamic neuromuscular stabilization in comparison to core stability exercises on balance, spasticity, and falling in people with MS	Core stability group: the training focuses on stabilizing muscles, with emphasis on the deep abdominal muscles, with no specific interest in trunk muscle timing and joint positioning	Dynamic neuromuscularstabilization group: the training focuses on postural control, with a specific interest in muscular timing and coordination	Balance, trunk control, falling rate, gait, pain
The Effectiveness of Additional Core Stability Exercises inImproving Dynamic Sitting Balance, Gait and FunctionalRehabilitation for Subacute Stroke Patients (CORE-Trial): Study Protocol for a Randomized Controlled Trial [126]	Stroke	To evaluate the effectiveness of core stability exercises, in addition to conventional physiotherapy, to improve sitting balance, standing balance, gait, risk of falling, ADL, and QoL	Control group: the training includes only conventional physiotherapy	Experimental group: the training includes conventional physiotherapy and core stability exercises	Balance, trunk control, falling rate, gait, pain, QoL
Effectiveness of LiuZiJue Qigong versus traditional core stability training for post-stroke patients complicated with abnormal trunk postural control: study protocol for a single-center randomized controlled trial [127]	Stroke	To compare the clinical efficacy of LiuZiJue Qigong and traditional core stability training in the treatment of stroke patients with abnormaltrunk posture	Control group: traditional core stability training combined with conventional rehabilitation therapy	Experimental group: LiuZiJue Qigong combined with conventional rehabilitation therapy	Standing and sitting balance, trunk control
Effect of Physiotherapy Treatment with Immersive Virtual Reality in Subjects with Stroke: A Protocol for a Randomized Controlled Trial [128]	Stroke	To investigate whether the designed immersive virtual reality training program is better in the short term (15 sessions) and in the medium term (30 sessions) than physiotherapy training with Bayouk, Boucher, and Leroux exercises, with respect to static balance in sitting and standing, dynamic balance and quality of life in patients with balance impairment in stroke survivors	Control group: functionality treatment group in combination with specific balance exercise training according to Bayouk, Boucher, and Leroux	Experimental group: functionality treatment group in combination with a balanced treatment using immersive VR	Balance, gait, QoL
RObotic-Assisted Rehabilitation for balance and gait in Stroke patients (ROAR-S): study protocol for a preliminary randomized controlled trial [129]	Stroke	To evaluate the improvement in balance, fatigue, quality of life, and motor and cognitive performance after combined conventional and robotic balance treatment with hunova® compared with conventional therapy alone	Control group: only conventional treatment, as per daily routine, using the main rehabilitation methods (e.g., neurocognitive theory, Bobath concept, progressive neuromuscular facilitation, etc.)	Experimental group: robotic treatment with hunova (mostly aimed at improving balance both in sitting and standing positions in both static and dynamic conditions, dual-task exercises, and exercises to improve trunk control), in addition to the conventional treatment	Balance, gait, executive functions, independency

show all the included studies. Table 1 summarizes, for each study in the first category, the target population, the number of groups, the type of training performed by each group, and the main outcomes in terms of abilities improved after training.

Table 2 highlights the goal, population, type of rehabilitative interventions, and methods used to evaluate the effectiveness of the interventions for the studies in the second category.

3.2.1. Population

Overall, considering the studies from both categories, we found 11 studies focused on MS subjects, 8 on PD, 12 on SCI, and 79 on stroke. Furthermore, one study included subjects with central nervous system deficits in general, although most subjects were conducted on stroke patients.

3.2.2. Intervention

The studies that we selected differed in terms of group characteristics (depending on the specific goal of the study), number of sessions, duration, and location (i.e., home-based and/or clinical setting). More precisely, the training duration ranged from 12 to 40 sessions with different weekly schedules. For instance, the 12 sessions could be structured as daily sessions from Monday to Saturday over a two-week period, three sessions per week for four weeks, or once weekly for 12 weeks, among other possible combinations. Additionally, the duration of each training session ranged from 30 min to 2 h and could be completed in a single continuous session per day or divided into multiple sessions throughout the day.

3.2.3. Outcome

Although these studies differ in terms of the type of training employed, they all aimed to assess the effectiveness of a given rehabilitative intervention regarding standing or sitting balance, trunk control, quality of life (QoL), and trunk muscle strength (a synthetic summary of results is reported in Table 1). In addition, RCTs have aimed to compare the effectiveness of two different types of training programs.

3.2.4. Rehabilitative Approaches

Figure 2 summarizes our findings on the methods that are used to enhance trunk control and functions in people with neurological conditions. Delving into the different studies, it is worth mentioning that all RCTs compare different types of training. Specifically, 17 studies compared conventional training with trunk control training, core stability training, or task-specific training, which is a therapy technique focused on improving functionalities through repeated activity practice. There is agreement within these studies that training specifically targeting trunk control, core stability, and throughout task-specific training is more beneficial than conventional training alone. Ali et al. [9] compared the effectiveness of conventional balance training alone and when combined with either core stability training or task-oriented training. These findings indicated that incorporating core stability training or task-oriented training alongside conventional balance training in MS seemed beneficial, with a slight preference for the inclusion of task-oriented training, which appeared to be a more favorable approach for enhancing standing balance. Differently, four studies compared a control group that did not perform any training with an experimental group that underwent either multidisciplinary training [34], balance training [112], trunk resistance training [114], or task-specific unsupported training [111]. The other RCTs compared different training programs to determine whether one was superior to the other(s).

Another study [105] highlighted that pelvic proprioceptive neuromuscular facilitation (PNF), in addition to task-oriented training, is more effective at improving both standing balance and gait than task-oriented training alone in stroke patients. PNF has positive effects as it improves the functions of muscles and tendons by stimulating the proprioceptive sense, which enhances muscle strength, flexibility, and balance [92]. In addition, PNF has positive effects when applied to the neck [92,106], as resistance during neck exercises also affects body trunk muscles [92].

Alternative rehabilitative approaches include dynamic neuromuscular stabilization (DNS) exercises, which aim to optimize motor function based on developmental kinesiology principles that focus on the maintenance of joints and segments in a central position while coordinating muscle timing along with respiratory training. In this framework, studies [37,42] compared DNS exercises with core stability training and neurodevelopmental training. Their findings demonstrated significant improvements in trunk muscle control in the DNS group. Similarly, studies [51,58,77,79,95] showed that the addition of inspiratory muscle training or Liuzijue training (which also includes respiratory training) to conventional training or trunk training leads to greater improvements in trunk control. Furthermore, other relaxation techniques, such as Pilates and Ai Chi, have shown beneficial effects when combined with conventional training [36,87,97,108].

Other rehabilitative approaches used in the studies included in this review for both stroke and SCI subjects include adapted sports. Sitting Tai Chi seemed beneficial as it had positive effects on standing and sitting balance in stroke [38] and SCI subjects [85,101], while sitting curling training improved trunk control in SCI subjects [103]. In contrast, the addition of sitting boxing to conventional training in stroke subjects led to greater improvements in balance and gait than conventional training alone [68].

Most of the studies selected for this review used tools such as new technologies and/or the typical instruments used in the clinical setting, such as fit balls, unstable platforms with spring resistances, therapeutic stairs, deformable surfaces, and postural mirrors. Unstable surfaces, balance pads, and Swiss balls are tools that have proven useful for the training of balance and trunk control. Although one study on stroke found that core stability training on both stable and unstable surfaces is more beneficial than conventional training, with no differences due to the support surface [33], other studies found that training on unstable surfaces is more beneficial for trunk control and sitting balance [35,40,63,64,66,71], gait [35], and standing balance [71]. In addition, training on unstable surfaces led to greater improvements in balance and gait in people with chronic SCI [32]. Another useful tool commonly found in clinics is the cycle ergometer, which is useful not only for limb rehabilitation but also for improving trunk control following stroke and SCI.

In contrast, within the technologies used in the selected articles, we can distinguish technologies used for electrical stimulation (ES), systems that enhance different types of feedback for improving performance, and robotic training technologies. ES is widely used in SCI, with beneficial effects on trunk control and trunk muscles’ activity [120,123,124]. It has also been proven to be beneficial for stroke patients, as it improves both trunk control and standing balance [69,102]. In addition, Ko et al. [102] showed that the maximal effect was achieved when coupled with core muscle training.

Several studies have highlighted the potential to enhance training effectiveness through the implementation of specialized programs that incorporate diverse forms of feedback. More precisely, training programs that integrated exercises based on visual, audiovisual, and combined visual and proprioceptive feedback demonstrated superior improvements in trunk control, core stability, and balance compared to conventional training approaches. Aphiphaksakul et al. [56] proposed a smartphone app that could also be used from home and not only in clinical settings. Real-time visual feedback was also provided during virtual reality training (VRT). This approach enhances their appreciation of these exercises and increases their motivation. Six articles that were included in the review proposed this approach. Specifically, VRT provides feedback based on the performance of the subject. The studies included here used either Kinect [25,27,48,99] or the Nintendo Wii [96] to monitor the subject’s performance, and only one of them provided a virtual experience with an immersive virtual reality system [27]. Despite the different methods, there is agreement on the effectiveness of adding VRT to conventional training to improve trunk control, sitting balance, standing balance, and gait [47,107].

Finally, some recent studies have evaluated the effectiveness of robotic training in comparison to conventional approaches. The robotic devices used in the studies selected in this review were very diverse. Two studies used the Spine Balance 3D system [73,93], which comprises two wireless ground force plates, a trunk sensor, a visual feedback monitor, and a tilting main body capable of tilting in eight distinct directions [130]. During training, the subjects were securely fastened at the lower part of their bodies, allowing the apparatus to tilt strategically. This controlled tilting prompted the subjects to engage and strengthen their core muscles. Training with this system led to greater improvements in terms of gait and the control of trunk muscles [73,93] and led to results comparable with training performed with the Biodex Balance system in terms of sitting and standing balance [93]. One study used the Space Balance 3D system [53] (which is based on the same concept as the previous device) and proved that after training with such a device, stroke subjects reported higher improvement in standing balance, trunk control, and control of trunk muscles than achieved via conventional training. The other robotic devices included in the studies in this review were based on movable chairs. Two studies used the Trunk Control Robot 3DBT-33 (TCR) [80,110], which includes a sensor-based foot platform, screen, and robotic seat that can be used in static or wobbling mode. TCR can be used both while standing and while sitting and is well suited to sit-to-stand training, as the robotic chair can assist the subject during movement. These studies [80,110] demonstrated that combining robotic training using TCR with conventional training resulted in substantial enhancements in balance and gait [80] and outperformed trunk extension training [110]. Other studies [55,121] used a T-chair device, which consists of a robotic sensorized chair and a screen, to provide visual feedback. A chair represents a support that may be stable or unstable and allows active and passive movements. The seat can move up to ±50 mm in the mediolateral direction and ±42 mm in the anteroposterior direction [121]. When used for training stroke patients, this device led to greater improvements than a conventional training program, particularly in the areas of balance, gait, and trunk control [55]. Similarly, hunova [131], which implemented both a movable chair and a movable base that integrated a computer screen for visual feedback and an inertial sensor to track trunk motion, demonstrated enhanced effectiveness in improving balance and trunk control in stroke subjects [16] and in improving balance in PD subjects [61]. In addition, [116] compared the effectiveness of robotic gait training with robotic gait training plus trunk rehabilitation using hunova in stroke subjects. The authors of this study noted that while both groups showed improvements in balance, the addition of trunk rehabilitation exercises with hunova resulted in a reduction in trunk displacement during dynamic exercises.

4. Discussion

Here, we present a scoping review aimed at presenting the current state of knowledge on core stability and trunk control rehabilitation, focusing on novel technologies that can be employed in this context. The findings of this review suggest that rehabilitation programs targeting trunk and core are effective at improving various outcomes including balance, trunk control, gait, trunk muscle control, independence, and quality of life. Our findings build on the outcomes presented in a previous study by Criekinge et al. [15], in which researchers conducted a meta-analysis and determined that trunk training can enhance trunk control, as well as sitting and standing balance and mobility, among individuals recovering from subacute and chronic strokes. In this review, the authors focused on functional outcomes without giving specific attention to the type of training method used. For this reason, we focused more on the training approaches. Although most of the studies in this review (72%) targeted stroke subjects, we have broadened our scope to include studies targeting people with SCI, MS, and PD, as these types of training are also relevant for these populations within the neurological field.

4.1. Integrating Conventional Rehabilitatione Approaches

Conventional methods for trunk rehabilitation, sitting balance re-education, and core training involve physiotherapy exercises for muscular strengthening, movement control, coordination, balance, walking, stepping, general mobility, and functional exercises in supported and unsupported sitting. However, this review showed that meaningful improvements can be made by integrating conventional training with respiratory training and/or functional exercises performed under various conditions. The former has been proven to be effective for trunk control, as respiratory training has direct positive effects on the muscles involved in inspiratory and expiratory functions, such as the diaphragm and external intercostal muscles [132,133], which led to indirect benefits in trunk control [79]. Indeed, these exercises are often integrated into rehabilitation protocols for people with MS, PD, and SCI. In contrast, integrating functional activities or adapted sports into rehabilitation programs is beneficial as it is helpful for daily life activities, motivates the person, and forces the person to work on different rehabilitative goals simultaneously. For example, a simple gesture such as reaching for a distant object requires the subjects to control upper limb and trunk movements in different directions; indeed, it implies body weight shifting from an initial position toward the direction of the object, then moving the arm and/or the hand while maintaining the stable position of the trunk, and then stabilizing themselves at the end of the task. A similar combination of goals occurs in adapted sports. However, it is crucial to perform all movements with correct muscle activation to avoid abnormal and suboptimal mechanisms [134].

4.2. The Role of Feedback during Training

To prevent incorrect and unforeseen mechanisms, it is important to consider and provide subjects with feedback regarding their performance. Numerous studies examined in this review have consistently highlighted the critical roles of various feedback mechanisms as they have beneficial effects on the efficacy of training. Various technologies facilitate the continuous monitoring of individual actions while simultaneously offering real-time feedback for the necessary adjustments of movements. These technological solutions encompass options such as Kinect or Nintendo Wii, which can be connected to a computer screen to provide visual feedback; immersive VR systems for VRT; and complex systems such as robotic devices.

4.3. The Added Value of Robotic Technologies in the Rehabilitation Field

Robotic devices typically integrate video screens and speakers to provide visual, auditory, or audio–visual feedback. These rehabilitation devices hold significant promise in the field; however, they exhibit notable diversity in terms of their design and training principles, especially when it comes to robots intended to target trunk control and core strength. Among the devices used in the studies included in this review, Spine Balance 3D and Space Balance 3D train trunk control while standing and moving in a 3D space. The controlled tilting of such devices induces different muscular activations based on the direction of movement. For instance, tilting in the anterior direction activates the back muscles, whereas tilting in the posterior direction targets the abdominal muscles. Furthermore, muscles such as the semispinalis, lumbar, and thoracic multifidi are activated in all tilt directions [130]. However, devices such as hunova, T-chair, and the Trunk Control Robot 3DBT-33 (TCR) adopt entirely distinct approaches to training. All these devices have seat bases that can be active, passive, or static. In addition, hunova includes an additional platform at the foot level, enabling both standing and sitting exercises, as well as exercises in sitting, with both movable base and movable seat. In addition, as a TCR, it can assist the sit-to-stand movements, as the seat can tilt to facilitate motion. In this review, hunova is the only robotic device that has been used for both stroke and PD subjects.

It is worth noting that these devices with movable chairs leverage principles similar to those utilized in clinical practice, where cushions are placed under the base of support (both at the seat and feet levels) or physio balls are employed. However, using robotic devices simplifies the process, as therapists can perform all necessary exercises with a single tool, eliminating the need for frequent changes in location or equipment while ensuring a broad differentiation of tasks. All of that is paired with continuous feedback, as these devices include sensors to monitor online subjects’ performance. In addition, robotic devices allow for the personalization of training regimens to match the user’s specific needs and capabilities, quantitatively monitor training progression, and enhance motivation.

4.4. Devices on the Horizon

Within the scope of this review, it is important to acknowledge additional technologies that hold promise in this field but were not included in our study due to specific inclusion criteria. Notably, no studies within our review used IMUs to monitor training progression or any incorporated body–machine interfaces, which have the potential to be relevant in this context. Furthermore, except for studies that employed Kinect, none integrated human pose estimation algorithms in conjunction with camera-based systems. Given the continuous evolution of this field, it is evident that such systems will likely be integrated into the clinical setting. Similarly, it is worth presenting new robotic devices that are beginning to show evidence in clinical research studies. Among these, AllCore360 promotes the continuous engagement of the trunk muscles while performing rotational plank exercise [135]. Zhang et al. [136] used the ProKin system (Technobody) with a trunk module. The ProKin system is composed of a platform with sensors that can function in either a static or dynamic configuration in either the active or passive mode. In addition, there is an extra separated module that includes a non-motorized seat, which can provide either stable or unstable support, along with a sensor that assesses trunk oscillations. The device is also equipped with a screen that allows players to play games and provides feedback on joint movements or trunk oscillations. Differently, the Trunk Support Trainer (TruST) is a robotic device that includes a belt fastened to the trunk, which is powered and manipulated by four cables linked to it. The device operates by applying active or assistive forces tailored to the individual’s capacity to control their trunk movements. To date, only one pilot study has tested whether it is possible to improve seated postural control with TruST in a participant with SCI [137]. Finally, it is worth mentioning exoskeletons; despite it not being their primary goal, they have an impact on trunk muscles and trunk mobility [15,138].

4.5. Limitation

This scoping review summarizes the existing research on trunk and core training, focusing on the methods adopted for training. However, the studies that we used to build our conclusions exhibit substantial heterogeneity. Within the RCTs, some compared novel approaches with conventional rehabilitation and some with no rehabilitation, and others compared different types of rehabilitation. Furthermore, as emphasized in our findings, diverse training loads were employed across the studies. We made the deliberate choice to incorporate all these training loads (as we are aware that the differences may also arise from the geographical location where the experiments were conducted). However, we were unable to provide insights into the optimal training load for achieving significant results, which could be of relevance for future studies.

5. Conclusions

In conclusion, this scoping review successfully undertook a comprehensive exploration of the existing literature pertaining to the methods and technologies employed in trunk rehabilitation and core strengthening. The studies included in this review allowed us to explore a wide array of rehabilitative approaches and tools, including dynamic neuromuscular stabilization, respiratory training, Pilates, Ai Chi, adapted sports, training on unstable surfaces, electrical stimulation, feedback-based training, and robotic training. This review is intended to serve as a valuable resource for clinicians and researchers, as by presenting together different methodologies, it can be used in the design of rehabilitative interventions aligned with specific rehabilitation objectives.