1.
Threshold of Energy Deficit and Lower-Body Performance Declines in Military Personnel: A Meta-Regression.
Murphy, NE, Carrigan, CT, Philip Karl, J, Pasiakos, SM, Margolis, LM
Sports medicine (Auckland, N.Z.). 2018;(9):2169-2178
Abstract
BACKGROUND Negative energy balance (EB) is common during military operations, diminishing body mass and physical performance. However, the magnitude of negative EB where performance would still be maintained is not well defined. OBJECTIVE Our objective was to explore relationships between EB and physical performance during military operations and define an acceptable negative EB threshold where performance may be maintained. METHODS A systematic search was performed for studies that measured EB and physical performance during military training. A total of 632 articles and technical reports were screened. Lower-body power and strength were the most common performance tests across investigations and were used as physical performance outcomes. Data were extracted from nine eligible studies containing 15 independent subgroups. Meta-regression assessed changes in performance in relation to study duration (days), average daily EB, and total EB (daily EB × duration). RESULTS Changes in physical performance were not associated with average daily EB or training duration. Total EB was associated with changes in lower-body power (r2 = 0.764, P < 0.001) and strength (r2 = 0.836, P < 0.001) independently and combined (r2 = 0.454, P = 0.002). Predictive equations generated from the meta-regression indicated that, for a zero to small (2%) decline in performance, total EB should be limited to - 5686 to - 19,109 kcal, for an entire operation, whereas total EB of - 39,243 to - 59,377 kcal will result in moderate (7%) to large (10%) declines in performance. CONCLUSION These data demonstrated that greater total negative EB is associated with declines in lower-body performance during military operations.
2.
Effect of vitamin D supplementation on muscle strength, gait and balance in older adults: a systematic review and meta-analysis.
Muir, SW, Montero-Odasso, M
Journal of the American Geriatrics Society. 2011;(12):2291-300
Abstract
OBJECTIVES To systematically review and quantitatively synthesize the effect of vitamin D supplementation on muscle strength, gait, and balance in older adults. DESIGN Systematic review and meta-analysis. SETTING MEDLINE, EMBASE, Cochrane Library, bibliographies of selected articles, and previous systematic reviews were searched between January 1980 and November 2010 for eligible articles. PARTICIPANTS Older adults (≥60) participating in randomized controlled trials of the effect of supplemental vitamin D without an exercise intervention on muscle strength, gait, and balance. MEASUREMENTS Data were independently extracted, and study quality was evaluated. Meta-analysis using a fixed-effects model was performed and the I(2) statistic was used to assess heterogeneity. RESULTS Of 714 potentially relevant articles, 13 met the inclusion criteria. In the pooled analysis, vitamin D supplementation yielded a standardized mean difference of -0.20 (95% confidence interval (CI) = -0.39 to -0.01, P = .04, I(2) = 0%) for reduced postural sway, -0.19 (95% CI = -0.35 to -0.02, P = .03, I(2) = 0%) for decreased time to complete the Timed Up and Go Test, and 0.05 (95% CI = -0.11 to 0.20, P = .04, I(2) = 0%) for lower extremity strength gain. Regarding dosing frequency regimen, only one study demonstrated a beneficial effect on balance with a single large dose. All studies with daily doses of 800 IU or more demonstrated beneficial effects on balance and muscle strength. CONCLUSION Supplemental vitamin D with daily doses of 800 to 1,000 IU consistently demonstrated beneficial effects on strength and balance. An effect on gait was not demonstrated, although further evaluation is recommended.