Strength-Training Exercise for Enhancement of Physical Function in Older Adults

To the Editor:

Bischoff-Ferrari et al.¹ examined the effects of vitamin D supplementation, Omega-3 fatty acid supplementation, or a strength-training exercise program on various outcome measures in older adults. We commend the authors for conducting such a large trial (n=2,157, 88% completion rate, 3 yrs). However, the conclusion that a “strength-training exercise program did not result in statistically significant differences in improvement in… physical performance” warrants further clarification. We would like to caution readers drawing conclusions about the efficacy of strength training in older adults based on the results of this study. Therefore, we provide three caveats to consider before supporting the authors’ conclusion.

First, the primary outcome for physical function was the short physical performance battery (SPPB). The SPPB uses integer scoring (range 4-12) and has been suggested to be insensitive to small change.² Second, the participants in this study had a high baseline SPPB (median value: 11) and, as such, this outcome measure may not capture change in high functioning individuals because of a ceiling effect. Given this, the authors could have selected secondary outcomes that parsed the SPPB into its individual, continuously measured functional tests to increase sensitivity. Third, the home-based exercise intervention was a “low dose” program (low intensity/volume/duration) that only consisted of sit-to-stands, one-leg stance, elastic band pull backs, elastic band external shoulder rotations, and stepping (3d/wk, 30-min). Unfortunately, this program did not consider the overload principle, which is a compounded problem when one considers that 83% of the participants already engaged in moderate to high physical activity. As such, the drawback of the work is that Bischoff-Ferrari and colleagues failed to acknowledge a decades-old hallmark of exercise prescription. Put simply, muscle adaptation occurs only when the exercise stress is above that normally attained.^3,4 It is well-known that higher intensity, progressive resistance exercise training is associated with improvements in muscle strength, and that increases in muscle mass largely ensure with the volume of resistance exercise.⁵

In closing, we believe their conclusion needs to be interpreted within the context of these caveats and also argue against the authors suggesting that in moderately to highly active older adults “…there may have been little potential for further benefit from additional exercise.” We postulate that if the primary physical function outcome had been a continuous, highly-sensitive outcome that is highly sensitive and the strength-training program followed the overload principle, significant positive adaptations/responses would have been observed in high functioning older adults.