Muscle quality maintenance or improvement is important for older adults to preserve or enhance physical function and metabolic health. There is conflicting evidence on whether exercise interventions improve morphological muscle quality (structure) and neuromuscular muscle quality (strength) in older adults. Further it is unclear which characteristics of exercise and for which populations, lead to greatest change in muscle quality. This systematic review aimed to estimate the effects of exercise interventions compared to non-active control on muscle quality in older adults.
A protocol that was specified a priori guided the methods. Sensitive searches performed in six databases, three grey literature databases, and citation tracking were used to identify randomised controlled trials that were published in English, Portuguese or Spanish. Participants were older adults (≥60 years) without a chronic condition. Interventions were supervised or unsupervised exercise interventions combined or not with nutritional programs. The comparators were mostly non-active interventions, but also included light physical activity (stretching or walking) or an educational control. The primary outcomes were morphological and neuromuscular muscle quality outcomes of the lower limb.
Two independent reviewers selected trials for inclusion, evaluated risk of bias and extracted data. Any disagreements were resolved by consensus discussions or by a third reviewer. Risk of bias was evaluated using the Cochrane risk of bias tool. Certainty of evidence was not evaluated. Meta-analysis was used to pool the included trials to calculate standardised mean differences and 95% confidence intervals (CI). Six subgroup analyses were conducted when data was available; (1) older adults subgroups (e.g., physically healthy, obese, mobility-limited, sarcopenic, frail); (2) exercise delivery modes (e.g., supervised vs. unsupervised exercise programs); (3) intervention modalities (e.g., resistance exercise, aerobic exercise, combined resistance and aerobic exercise, water-based exercise prescription, exercise plus nutritional supplementation); (4) outcomes assessment (e.g., muscle echo intensity, intermuscular adipose tissue); (5) thigh versus calf muscle outcomes (or knee extensors vs. plantar flexors); and (6) based on risk of bias assessment.
21 trials (973 participants) were included in the meta-analyses. Participants had a median age of 70 years (IQR 67-75), were women (n=651, 67%), had a BMI of 27.5 kg/m2 (IQR 25.5–28.4). Most trials (n=15, 71%) included physically healthy older adults and compared to non-active intervention groups (n=12, 57%). Compared to control, participants in the exercise groups had a small improvement in morphological muscle quality (SMD 0.32; 95% CI 0.13 to 0.51; 10 trials; 387 participants) at follow-up. Compared to control, participants in the exercise groups had a small improvement in neuromuscular muscle quality (SMD 0.49; 95% CI 0.29 to 0.69; 13 trials; 482 participants) at follow-up. Both results varied when investigated in subgroup analyses.
Exercise interventions provide small improvements in both morphological and neuromuscular muscle quality compared to control. It is unclear whether these improvements in muscle quality translate to meaningful changes in patient relevant outcomes.
Radaelli, R., Taaffe, D.R., Newton, R.U. et al. Exercise effects on muscle quality in older adults: a systematic review and meta-analysis. Sci Rep 11, 21085 (2021). https://doi.org/10.1038/s41598-021-00600-3