Efficacy of progressive resistance training on balance performance in older adults : a systematic review of randomized controlled trials

The serious health, social and economic consequences of falls are well documented. Lower extremity muscle weakness and power as well as balance impairment are major independent intrinsic contributors to falls and amenable to intervention. Progressive resistance training (PRT) is widely accepted as an appropriate modality for treating sarcopenia and has been reported to improve balance. However, other studies affirm no significant effect of PRT on balance. To date, there is no clear, definitive statement or synthesis of studies that has examined the effect of PRT on balance. Therefore, our objective was to systematically review the literature to probe the merit of PRT as a single intervention on balance performance in older adults. We conducted a comprehensive search of major electronic databases to October 2006, with citation searches and bibliographic searches of journal articles and literature/systematic reviews. Two independent reviewers screened for eligibility and assessed the quality of the studies using the Physiotherapy Evidence Database scale for validity assessment. Randomized controlled trials of PRT only, with any balance outcome in participants with a mean age of >/=60 years (individual minimum age >50 years) were included. Trials that contained more than one intervention, providing the PRT and control groups matched the inclusion criteria, were also included. Because of the heterogeneity of interventions and balance outcomes, a meta-analysis was not performed. However, corrected effect sizes with confidence intervals were determined for each study outcome. Twenty-nine studies were compatible with the inclusion/exclusion criteria and were eligible for review. Participants (n = 2174) included healthy, community-dwelling, mobility-limited, frail cohorts and those with chronic comorbidities. Balance outcomes conducted were extensive and were broadly categorized by the authors as: static, dynamic, functional and computerized dynamic posturography. Some studies used more than one balance outcome. The number of balance tests in all totalled 68. Fourteen studies (15 tests representing 22% of all balance tests) reported improvements, significantly greater than controls, in balance performance following PRT. Improvements were not linked to a particular type of balance performance. The inconsistent effect of PRT on balance may be explained by heterogeneity of cohort and balance tests, variability in methodology of the balance test and sample size, inadequate dose of PRT and/or compliance to training, or lack of statistical power. Standardization of balance testing methodology and better reporting of procedures may ensure greater comparability of results in future studies. It is also possible that PRT alone is not a robust intervention for balance control. This is the first systematic synthesis of the literature to examine the effectiveness of PRT alone on balance performance in older adults. The limited evidence presented in currently published data has not consistently shown that the use of PRT in isolation improves balance in this population. However, further research should explore optimal resistance training regimens that: focus on the muscles most pertinent to balance control, best target neuromuscular adaptations that protect against postural challenges and elucidate mechanism(s) by which PRT may affect balance control.