Gordon BR, et al. - Researchers aimed at determining the association of effectiveness of resistance exercise training (RET) with depressive symptoms and assessing the extent to which logical, theoretical, and/or prior empirical variables are linked with depressive symptoms and if the association of effectiveness of RET with depressive symptoms accounts for variability in the overall effect size. They noted significantly reduced depressive symptoms in association with RET among adults regardless of health status, total prescribed volume of RET, or significant improvements in strength.

Methods

• Researchers searched for articles published before August 2017, using Google Scholar, MEDLINE, PsycINFO, PubMed, and Web of Science.
• They selected randomized clinical trials including randomization to RET (n = 947) or a nonactive control condition (n = 930).
• They computed Hedges d effect sizes and used random-effects models for all analyses.
• To quantify the potential moderating influence of participant and trial characteristics, they conducted meta-regression.
• Validated measures of depressive symptoms assessed at baseline and midintervention and/or postintervention were used in the randomized clinical trials.
• They selected 4 primary moderators a priori to provide focused research hypotheses about variation in effect size: total volume of prescribed RET, whether participants were healthy or physically or mentally ill, whether or not allocation and/or assessment were blinded, and whether or not the RET intervention resulted in a significant improvement in strength.

Results

• They got 54 effects from 33 randomized clinical trials involving 1,877 participants.
• Resistance exercise training was noted to be correlated with a significant reduction in depressive symptoms with a moderate-sized mean effect Δ of 0.66 (95% CI, 0.48-0.83; z = 7.35; P < .001).
• Significant heterogeneity was indicated (total Q = 216.92, df = 53; P < .001; I² = 76.0% [95% CI, 72.7%-79.0%]), and sampling error accounted for 32.9% of observed variance.
• In this study, the number needed to treat was four.
• No significant association of total volume of prescribed RET, participant health status, and strength improvements was noted with the antidepressant effect of RET.
• However, with blinded allocation and/or assessment, smaller reductions in depressive symptoms were derived from randomized clinical trials.