Acute and chronic effects of stretching on balance – A systematic review with multilevel meta-analysis

Abstract

Introduction One-third of individuals over the age of 65 fall at least once per year. Lacroix et al. (2017) shows that supervised strength training improves balance and muscle strength, which might beneficially impact the risk of falls. The American Geriatrics Society and the American Academy of Orthopaedic Surgeons recommend resistance training to improve balance (McMurdo, 2002). However, administrative burden such as limited mobility can reduce engagement among older adults for common training routines and call for the development of alternatives, but no review has investigated whether stretching has acute or chronic effects on balance. Purpose Since recent studies pointed out that high volumes of stretch could be used interchangeable with resistance training, but can be safely used without supervision (Warneke et al., 2024), this systematic review with meta-analysis investigate the effects of stretching on balance parameters across the lifespan. Methods PubMed, Web of Science, and Scopus were screened for (randomized) controlled trials (RCTs) on acute and chronic stretching effects, with subgroup analyses for a) stretching types, and b) different balance tasks, e.g., standing as still as possible on a force plate to measure the center of pressure (CoP) with eyes open (EO) and eyes closed, as well as Y-balance and star excursion test were conducted. We assessed risk of bias, while certainty of evidence was assessed in accordance with the GRADE working group guidelines. Statistical calculations were performed with R (version 4.2.3). Effect sizes (ES) were quantified using the packages Robumeta and Meta. Results Out of 18 acute studies, 15 compared acute stretching effects to passive control, while 4 performed comparisons to an active control, resulting in small magnitude effects on CoP/Sway EO (ES: 0.21, p = 0.03). Out of eleven chronic studies, seven had passive control, and 5 an active control group, resulting in moderate balance improvements with ES reaching 0.63, p = 0.04 for CoP/Sway EO. The remaining effects remained unsignificant (p = 0.091 - 1). Discussion While flexibility is commonly performed to enhance flexibility, it can also positively impact balance in some conditions. While our research question was derived via the positive association between strength and balance (Muehlbauer et al., 2015), and the possibility to use high volume stretching to enhance strength (Warneke et al., 2024), neither used included studies stretching durations of sufficient length, nor was strength measured as an outcome. It is noteworthy that most of the included studies did not interpret stretching effects in the light of underlying physiology, but on a more phenomenological basis, making a final conclusion about potential mechanisms complicated. Conclusion Although our results indicated beneficial effects of stretching on balance in some subgroup analyses, underlying mechanisms remain speculative, yet. There is a dearth of high-quality randomized controlled studies, using reasonable stretching times to enhance strength and muscle size via stretch to check whether there is the potential to use stretch-mediated hypertrophy and strength increases as a viable alternative to common resistance training and balance programs when aiming to enhance balance. References Lacroix, A., Hortobágyi, T., Beurskens, R., & Granacher, U. (2017). Effects of supervised vs. unsupervised training programs on balance and muscle strength in older adults: A systematic review and meta-analysis. Sports Medicine, 47(11), 2341–2361. https://doi.org/10.1007/s40279-017-0747-6 McMurdo, M. E. T. (2002). ‘Guideline for the prevention of falls in older persons’: Essential reading. Age and Ageing, 31(1), 13–14. https://doi.org/10.1093/ageing/31.1.13 Muehlbauer, T., Gollhofer, A., & Granacher, U. (2015). Associations between measures of balance and lower-extremity muscle strength/power in healthy individuals across the lifespan: A systematic review and meta-analysis. Sports Medicine, 45(12), 1671–1692. https://doi.org/10.1007/s40279-015-0390-z Warneke, K., Lohmann, L. H., Behm, D. G., Wirth, K., Keiner, M., Schiemann, S., & Wilke, J. (2024). Effects of chronic static stretching on maximal strength and muscle hypertrophy: A systematic review and meta-analysis. Sports Medicine – Open, 10, Article 45. https://doi.org/10.1186/s40798-024-00706-8

Keywords

• postural control
• center of pressure
• sway
• dynamic balance
• static balance