Search Results (237)

Objectives: Soccer is the most practiced sport around the world. The injury incidence has an estimated rate of up to 70 injuries per 1000 h of play. FIFA 11+ is a program designed to prevent injuries and optimize performance. The purpose of this study was to analyze the acute effects of this program as a warm-up on different functional, physiological, and mechanical properties of various knee tissues and whether there were differences between genders. Methods: The sample included 45 recreational soccer players. Several muscular and tendon mechanical properties, muscular oxygen saturation, electromyography, maximum voluntary contraction, and rate of force development were analyzed, before and after performing the FIFA 11+. Results: Only a moderate significant increase in muscle oxygen saturation in men from pre- to post-test was reported. No other parameters showed statistically significant differences between groups, suggesting that the intervention may lack clinical relevance. The reported effect sizes were mostly trivial, so differences are unlikely to have significant practical relevance. Statistical analyses were performed using a 2 × 2 factorial repeated measures factorial ANOVA with Bonferroni post hoc comparisons. Conclusions: FIFA 11+ warm-up does not provide a sufficient stimulus to elicit mechanical or metabolic responses in the per-knee structures. Other warm-up designs may be more appropriate for finding these effects. Full article

The application of blood flow restriction (BFR) during resistance exercise enhances muscular adaptations under low-load conditions. However, its acute effects on explosive neuromuscular performance, particularly on kinetic variables such as the rate of force development (RFD), impulse, and peak force remain poorly understood in women. Twenty-five participants underwent randomized sessions under three occlusion conditions (0%, 40%, and 80% limb occlusion pressure), followed by isometric mid-thigh pull (IMTP) assessments at five time points (pre-exercise; post-exercise; and 5, 10, and 15 min post-exercise). Peak force, impulse, and RFD were analyzed across early (0–50 ms), mid (51–150 ms), and late (151–250 ms) time intervals. BFR did not result in statistically significant alterations in RFD or isometric force production at any time or pressure. These findings indicate that acute BFR application, even when volitional fatigue is induced, does not substantially impair neuromuscular function in isometric settings. These findings indicate that acute exposure to BFR, even under fatiguing conditions, does not substantially impair isometric force production or explosive performance in young physically active women. These results support the task-specific and temporally dependent nature of neuromuscular responses to BFR, highlighting the need for population-specific approaches in BFR programming. Full article

Introduction: Spinal and bulbar muscular atrophy (SBMA) is an X-linked neuromuscular disorder characterized by progressive muscle weakness, along with muscle cramps, tremors, and sensory neuropathy. Previous research has shown that patients with SBMA have difficulty with dynamic balance and sensory postural control during quiet stance. There have been no reports on automatic postural reactions in SBMA. Objectives: In this study, we aimed (1) to augment previous findings of sensory postural control, (2) to investigate automatic postural reactions in SBMA, and (3) to explore the relationship between strength and balance. Design: A cross-sectional design was used for the analysis. Participants: The participants were fifty male individuals with a confirmed diagnosis of SBMA. Outcome Measures: Balance testing included the NeuroCom modified Clinical Test of Sensory Interaction on Balance (mCTSIB), which measures sway velocity during quiet stance, and the NeuroCom Motor Control Test (MCT), which measures the latency and strength of postural reactions following sudden perturbations. Strength testing included maximal voluntary isometric contractions measured via fixed-frame dynamometry. Results: Forty-seven out of fifty participants were able to complete the mCTSIB test, but only thirty-eight completed the MCT test. Patients who were unable to complete the MCT were significantly weaker in all lower extremity muscles compared to those who were able to complete testing. Compared to normative data, participants showed significantly higher sway velocity during quiet stance across all conditions of the mCTSIB, except when standing on foam with eyes open. They also exhibited significantly slower postural reactions in response to sudden shifts of the force plate on the MCT. Plantarflexor weakness was significantly correlated with poor postural control on the mCTSIB and MCT. Conclusions: This study confirms previously reported abnormalities of sensory postural control in SBMA and highlights patients’ heavy reliance on visual inputs for postural control. Additionally, this study shows that automatic postural corrections are slower than normal in SBMA and provides a unique approach for measuring the combined sensory and motor components of the disease. Both the sensory and automatic balance abnormalities were found to be associated with plantarflexor weakness and may contribute to a higher risk of falls under challenging situations. Therefore, addressing this weakness may be an important step toward fall prevention in this population. Full article

This study investigated kinetic and physiological load characteristics of Self-Manual Resistance Training (SMRT) lat pulldown. SMRT lat pulldown is a training method in which practitioner generates resistance manually using their own muscular force by gripping a towel with both hands and pulling it outward in a horizontal direction. We analyzed shoulder and elbow joint moments in frontal plane (2D) and muscle activity levels of latissimus dorsi (LD), posterior deltoid (PD), biceps brachii (BB), and triceps brachii (TB) during 10 maximal-effort repetitions of SMRT lat pulldown in 11 resistance-trained men. For comparison, we also measured muscle activity levels during a machine lat pulldown for 10 reps at 75% 1 RM load in same participants. Peak shoulder adduction and elbow extension moments during SMRT lat pulldown were both approximately 70% MVC. Mean rectified EMG of LD was significantly greater during machine lat pulldown than SMRT lat pulldown, whereas that of PD was significantly greater during SMRT than machine version. Mean rectified EMG of TB was high during SMRT, and that of BB was high in machine version. SMRT lat pulldown appears to produce relatively large shoulder adduction and elbow extension moments, increasing PD and TB activation and limiting LD activation. Full article

Background: Three-dimensional skeletal muscle organoids (3D SkMO) are becoming of increasing interest for preclinical studies in Duchenne muscular dystrophy (DMD), provided that the used platform demonstrates the possibility to form functional and reproducible 3D SkMOs, to investigate on potential patient-related phenotypic differences. Methods: In this study, we employed fibrin-based 3D skeletal muscle organoids derived from immortalized myogenic precursors of DMD patients carrying either a stop codon mutation in exon 59 or a 48–50 deletion. We compared dystrophic lines with a healthy wild-type control (HWT) by assessing microtissue formation ability, contractile function at multiple timepoints along with intracellular calcium dynamics via calcium imaging, as well as expression of myogenic markers. Results: We found patient-specific structural and functional differences in the early stages of 3D SkMO development. Contractile force, measured as both single twitch and tetanic responses, was significantly lower in dystrophic 3D SkMOs compared to HWT, with the most pronounced differences observed at day 7 of differentiation. However, these disparities diminished over time under similar culturing conditions and in the absence of continuous nerve-like stimulation, suggesting that the primary deficit lies in delayed myogenic maturation, as also supported by gene expression analysis. Conclusions: Our results underline that, despite the initial maturation delay, DMD muscle precursors retain the capacity to form functional 3D SkMOs once this intrinsic lag is overcome. This suggests a critical role of dystrophin in early myogenic development, while contraction-induced stress and/or an inflammatory microenvironment are essential to fully recapitulate dystrophic phenotypes in 3D SkMOs. Full article

Background: Many studies analyse the effectiveness of the Herbst device in the treatment of dentoskeletal Class II malocclusion due to mandibular retrusion. This fixed device was devised by Emil Herbst for Class II treatment using a bite jumping, i.e., a device that holds the jaw in a forced anterior position. Comparison of the results obtained in numerous studies is difficult because they are often not comparable and not congruent due to a number of variables that prevent standardization. Methods: The purpose of the present study is to report some clinical-level considerations that may be important in order to obtain more predictable therapeutic outcomes. The simplified design of the Herbst device offers better patient comfort and easier cleanability but may show some disadvantages, such as less anchorage. Results: The device was evaluated in conjunction with the multi-bracket phase that preceded Herbst therapy and concluded after the device was removed. The therapy was performed in the absence of skeletal anchorage. Conclusions: In our opinion, standardization of therapy according to precise protocols may positively affect the therapeutic outcomes by achieving faster occlusal stabilization, more proper neuro-muscular balance, less stress on anchor units, and shorter treatment time. Full article

The goal of this study was to construct a mathematical and computational model that accurately represents the complex, flexible movements and mechanics of an elephant’s trunk. Rather than serving as a biological study, the elephant trunk model was used as an application to demonstrate the effectiveness of a proposed rigid–flexible coupling framework. This model has broader applications beyond understanding the mechanics of an elephant trunk, including its potential use in designing flexible robotic systems and prosthetics, as well as contributions to the fields of biomechanics and animal locomotion. An elephant’s trunk, a highly flexible and muscular organ without bones, is best modeled using continuum mechanics to capture the dynamic behavior of its motion. Given the rigid body nature of an elephant’s head movement and the highly flexible nature of the trunk, a robust geometric framework for the rigid–flexible interface is crucial to accurately capture the complex interactions, force transmission, and dynamic behavior arising from their distinct motion characteristics and differing coordinate representations. Under the umbrella of flexible multibody dynamics, this study introduced a hybrid coordinate system, integrating the Natural Coordinates Formulation (NCF) and the Absolute Nodal Coordinates Formulation (ANCF), to establish the geometric constraints governing the interaction between the rigid body (the head) and the highly flexible body (the trunk). Moreover, the model illustrates how forces and moments are transmitted between these components in both direct and inverse scenarios. Various finite elements were evaluated to identify suitable elements for modeling the elephant’s trunk. The model’s accuracy was validated through simulations of bending, twisting, compression, and other characteristic trunk movements. The solution method is presented alongside the simulation analysis for various motion scenarios, providing a comprehensive framework for understanding and replicating the trunk’s complex dynamics. Full article

Background: the validity and reliability of the front plank test (FPT) have been studied in young adults but not in adults aged 34 to 60 years. The aim of this study was to analyze the criterion-related validity and reliability of the front plank test (FPT) for evaluating trunk musculature in adults according to sex and age groups. Methods: a repeated measures design was used to study the reliability of the FPT. A total of 84 adults aged 18–62 years performed trunk muscular force tests and the FPT. Criterion-related validity was assessed using repeated measures ANOVA. Reliability was examined by ICC, error measurements, and Bland–Altman analysis across sex and age groups. Results: significant differences in the activation of the rectus abdominis and external oblique muscles were found compared with the erector spinae and multifidus muscles (p < 0.001). No correlations were found between FPT time and physical activity or rate of perceived exertion at the end (p > 0.05). Low and moderate correlations were found with body fat percentage, trunk fat mass percentage, and external oblique, regardless of sex and age groups (p < 0.05). Extremely high reliability was found regardless of sex and age groups (ICC > 0.98), with low error measurements (RMSE = 11.93–18.73; %CV = 4.91–6.33; SEE = 11.45–16.84). MDC90 values indicated no real change between T1 and T2. Conclusion: FPT is a valid and reliable test for assessing trunk musculature in adults regardless of sex and age groups. Full article

Aim: The aim of this study was to compare balance performance and electromyographic activity in individuals with COPD, with and without sarcopenia. Method: Thirty-five patients with COPD were classified with and without sarcopenia according to EWGSOP criteria. Balance was assessed using a force platform under four conditions: standing with feet apart and eyes opened (FHEO), eyes closed (FHEC), on an unstable surface (US), and on one leg (OLS). The surface electromyography activity of lower limb muscles and trunks was recorded. Additionally, the timed up and go test (TUG) and the Brief Balance Evaluation Systems Test (Brief-BESTest) were also utilized. Results: Under the FHEO, FHEC, and US conditions, individuals with sarcopenia demonstrated increased velocities, larger oscillation amplitudes, and greater center of pressure displacements under the US condition (p ≤ 0.02). They also showed a higher activation of the scalene, sternocleidomastoid, and abdominal muscles during OLS, along with a reduced activation of the tibialis anterior during OLS and US, and a decreased activation of the vastus medialis during FHEC and US (p ≤ 0.04). Furthermore, sarcopenic COPD patients exhibited poorer performance on the TUG and Brief-BESTest compared to their non-sarcopenic counterparts (p ≤ 0.02). Conclusions: Individuals with COPD and sarcopenia demonstrated greater instability in both bipedal stances and on unstable surfaces, as well as poorer performance in both dynamic and static balance assessments. Furthermore, these individuals exhibited reduced muscular activation in the lower limbs compared to those without sarcopenia. Full article

The present study aimed to evaluate the effects of 12-week resistance training (RT) on muscle strength, dynamic balance, glycemic control and the lipid profile. Methods: The Laboratory of Movement Studies in the University of São Paulo, Brazil, developed this longitudinal study between 2021 and 2023. It assessed 62 males with type 2 diabetes mellitus pre and post an RT protocol. The participants, who were 69.8 (±3.9) years old, took part in a 12-week twice-weekly RT program. Three sets of eight to twelve repetitions each were executed for eight exercises targeting the large muscle groups. The intensity was set between 7 and 8 out of 10 for perceived effort, according to the Omni Resistance Exercise Scale. All participants were evaluated pre and post in knee extensor and flexor strength by isokinetic dynamometry, handgrip strength by manual dynamometry and dynamic postural balance by a force platform, as well as blood tests to determine the lipid and glycemic profiles. For comparison, paired t or Wilcoxon tests were used at an alpha of 5%. Results: There was an improvement in muscular strength by handgrip restricted to the non-dominant side (p = 0.033) and for the bilateral knee flexors (p < 0.001) and extensors (p < 0.001), as determined by isokinetic dynamometry. There was no improvement in dynamic postural balance, glycemic control or lipid control. Conclusions: The 12-week RT promoted improved muscle strength in knee extension and flexion and non-dominant grip pressure but did not affect dynamic balance, glycemic control or the lipid profile. Full article

Background: Although a cross-legged sitting (CLS) posture has been commonly practiced as a daily activity, particularly in Arabic, Middle Eastern, and Asian societies, there is no medical study focusing on the effects of cross-legged sitting on body balance and muscular strength. Therefore, this study aimed to investigate the effect of CLS on lower extremity muscular strength, muscular electrical activity, and body balance. Methods: Thirty healthy volunteers participated in this research study by performing CLS for a 20 min duration. The balance tests included a static test, i.e., a single-leg-standing posture with eyes closed, to assess if the centre of the pelvis and centre of the shoulders (CoS) moved, and a dynamic test, i.e., four-square-returning, to assess if the moving speed changed. Regarding the muscular assessment, the electrical activity was assessed depending on the maximal value of activation and rooted mean of squared values, while the muscular strength was assessed according to the maximum force by the lower limbs using a force sensor. The balance and muscular results were statistically compared before and after CLS. Results: The duration of the static balance after CLS decreased by an average of 2.5 s, or approximately 15.64%, compared to before CLS (p < 0.05 *). Further, the Centre of Pelvis moved greater distances in the medial–lateral direction after CLS compared to before, but CoS was not significantly changed in the static balance test. However, in the dynamic balance test, the duration significantly decreased by 0.2 s, or approximately 8.5%, after CLS compared to before, meaning that dynamic balance ability improved. Considering the muscle results, only the lateral gastrocnemius muscle was noticeably electrically activated after CLS, while the hip extensor and knee flexor muscles became significantly stronger after CLS compared to before, roughly by about 14%, and the ankle plantar flexor maximum force increased noticeably, by about 4%, after CLS. Conclusions: CLS had a positive impact on the dynamic balance; the strength of the hip extensor, knee flexor, and ankle plantar flexion; and all lower limb muscles, in terms of electrical stimulation, except for the lateral gastrocnemius post-CLS compared to pre-CLS. Therefore, CLS can be safely included in one’s daily routine and in any rehabilitation programme, except for patients who are suffering from static balance disturbance. Although this posture is commonly used in many societies, because this is the first study focused on the impact of CLS on body balance and muscular status, the results would supply knowledge and new understanding, as well as provide clear insight for sitting posture research. Full article

Muscular strength and explosiveness are generally known as factors that affect physical performance. Physical ability modeling has a profound connection with long-term athlete development and talent identification. The purpose of the current study was to investigate differences in contractile characteristics (maximal isometric force and maximal rate of force development) among various muscle groups in youth elite female team handball players (n = 35, 16.6 ± 1.1 years) compared to a control group (n = 28, 16.7 ± 1.1 years). The following tests were performed: isometric non-dominant hand grip, isometric dominant hand grip, isometric deadlift, isometric standing leg extension, and isometric bilateral ankle extension. For each subject, the maximal isometric force and maximal rate of force development were derived from the isometric strength tests. The research analyzed a total of twenty-four variables, presented in both absolute and relative values. Statistical analysis revealed significant differences among all pairs of variables in the absolute values of maximal isometric force (Λ = 0.531, F = 10.07, p = 0.000) and maximal rate of force development (Λ = 0.692, F = 5.08, p = 0.001) between the two groups. The most significant difference was found in the grip of the dominant hand, where the impact of the difference was 43.6% and 37.0% for the absolute values of force and explosiveness. Conversely, no differences were observed between the pairs of variables representing the relative values across the two subject groups, except for the dominant hand grip relative force (p = 0.006). The results provide information about the contractile potentials of important muscle groups in the game of handball, which could help in adapting strength training according to the specifics of the strength and explosivity development of young female handball players. Full article

This study investigated muscle activation, shocks, and vibrations of the upper extremities during tennis serves between junior and adult tennis players. Thirty-five well-trained tennis players (15 juniors and 20 adults) performed 10 maximal successful tennis serves. Two triaxial accelerometers recorded the shock and vibration on the racket and the hand on the dominant side. Eight surface EMG electrodes were also used to measure the arm muscles’ activities. Linear mixed models were used to test the fixed effect of age on muscular activation and vibration. Statistical non-Parametric Mapping was employed to make statistical inferences on the EMG and accelerometer data obtained from the continuous wavelet transform. Comparing EMG parameters between junior and adult players reveals similar upper limb intermuscular coordination. The junior players experienced lower racket and hand vibration amplitudes, which were partially explained by a lower ball velocity. This study revealed that young players showed no difference in EMG parameters in the tennis serve but were as exposed to shocks and vibrations as adults when compared based on a given speed and a given handgrip force. These vibrations apply to an immature skeleton, which can increase the risk of injuries caused by overuse. In addition, differences in the racket vibration frequency provide original knowledge to engineers who need to develop innovative sports equipment for tennis. Full article

Objectives: The objective of this paper is to introduce a method to measure the force or pressure over the carpal tunnel indirectly, using a new device to drive the pointer of a computer system. The measurements were compared with those obtained using an ergonomic mouse. Simultaneously, measurements of muscular stress on the digitorum extensor muscle were performed to correlate the applied force against muscle activity. Methods: An experimental setup was constructed using an infrared static receiver plus two wearable moving light emitters, which can be displaced inside a rectangular projected region. The pointer functions are performed through two finger gestures, while the hand is naturally extended. A microcontroller was used to communicate with the computer, which works as a human interface device and possesses firmware to associate the position of each light source with the pointer functions. Meanwhile, force and electromyography sensing circuits were developed to transmit and measure carpal tunnel strength and muscular stress. The system was tested on five healthy volunteers, who were encouraged to solve the same computational tasks using this new device and a trademark ergonomic mouse. Results: Our results show great differences (greater than one magnitude) between the efforts of the same volunteers performing the same predefined tasks using both pointer controllers. Only when the new device was used did the Pearson’s correlation coefficients show a higher correlation between the effort measured on the carpal tunnel and the muscular activity. Conclusions: The optic pointer driver diminishes the strength on the carpal tunnel, causing slightly increased stress on the digitorum extensor muscle. Full article

Background: Combining pool-based and resistance workouts, both in the pool and on dry land, is a valuable approach to enhancing swimming performance. However, few investigations have been conducted on this topic. Through a randomized controlled trial study, we investigated the effects of a 10-week concurrent resistance training program, which integrated resistance workouts both in the pool and on dry land on tethered force, lower limbs strength, anaerobic critical velocity, and swimming performance, in regional age-group breaststroke swimmers. Methods: Regional age-group swimmers (N = 24, males) were randomly divided into two groups. The experimental group (EG: 15.1 ± 0.5 years old) performed combined pool-based + resistance workouts, both in the pool and on dry land. The control group (CG: 15.1 ± 0.7 years old) performed their usual training regime, i.e., pool-based + resistance workouts on dry land only. The tethered swimming force, muscular strength, anaerobic critical velocity, and swimming performance and technique of the swimmers were evaluated before the training program began and after 10 weeks. Results: Improvements were observed in the EG vs. the CG in terms of the mean force (30.04%, p = 0.02; d = 0.75), one-repetition maximum back squat (20.57%, p = 0.01; d = 2.05), maximal force (19.23%, p = 0.03; d = 0.69), and anaerobic critical velocity (4.2%, p = 0.04; d = 0.61). The 50 and 200 m breaststroke performance times improved (4.3 and 5.4%, p = 0.01, d = 0.88–0.92, respectively) after 10 weeks. Conclusions: With the increasing demands of contemporary swimming competitions, which often include heats, semifinals, and finals, achieving optimal physical fitness to compete at an elite level, in every round, is vital for swimmers. The combination of resistance training workouts both in the pool and on dry land seems to enhance swimming performance in age-group swimmers, particularly in sprint to middle-distance breaststroke swimmers. Full article