**1. Introduction**

Around the world, populations are ageing [1], leading to an increased incidence of age-related accidental injuries, often caused by falls [2,3]. In recent years, evidence has been building that falls, particularly in older individuals, are to some degree preventable. Specifically, several studies confirmed that exercise programs can be effective in improving balance and in lowering fall rates in older adults, as summarized in recent review papers [4,5]. However, recently, access to exercise programs has been severely limited by the global response to the COVID-19 pandemic: sports facilities were closed, and in some cases, citizens were asked to stay at home, sometimes for periods of several weeks. Since older adults have a higher risk for a difficult progression in case of a COVID-19 infection, this age group is particularly subjected to restrictions. This is unfortunate, since particularly in this age group, exercises have a number of tangible health benefits, including the maintenance of the balance and postural control skills that are needed to prevent falls and accidental injuries.

The concept of detraining has been described in previous literature as "the partial or complete loss of training-induced anatomical, physiological, and performance adaptations, as a consequence of training reduction or cessation" [6], p. 80. Historically, research has mainly focused on the physiological effects of detraining after strength or resistance training, e.g., [7,8], but very little is known about detraining in balance skill [9]. The current study assumes that a sudden stop in balance training might induce detraining effects that could increase the risk of falls in older adults. While the recently experienced lockdowns due to COVID-19 motivated the current study, our research question is of general interest,

**Citation:** Modaberi, S.; Saemi, E.; Federolf, P.A.; van Andel, S. A Systematic Review on Detraining Effects after Balance and Fall Prevention Interventions. *J. Clin. Med.* **2021**, *10*, 4656. https://doi.org/ 10.3390/jcm10204656

Academic Editor: Michele Roccella

Received: 28 July 2021 Accepted: 5 October 2021 Published: 11 October 2021

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since a sudden stop of participation in a regular exercise program can occur for various reasons. As such, the current study will focus on the "performance adaptation" component of detraining to assess the effects of a cessation of balance training for indicators of fall risk.

The aim of the current study was to review the available scientific literature on detraining effects after a sudden stop of an exercise program on outcomes related to fall risk. To operationalize this aim, we shall consider fall risk in two ways. Firstly, as a direct measure of fall risk, studies reporting on fall rates would be accepted into the review. Second, as an indirect measure, studies reporting on fall risk assessments will be accepted. This second definition might pose some methodological challenge, since indirect measures of fall risk are numerous [10] and might not always be easily compared. For these studies, the study characteristics shall be synchronized in one table in an effort to distill common principles from the literature.

#### **2. Materials and Methods**

This systematic review was carried out in accordance with the Preferred Reporting Items for Systematic Reviews guideline [11] and under PROSPERO registration number CRD42020199932.
