Threshold of Energy Deficit and Lower-Body Performance Declines in Military Personnel: A Meta-Regression
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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.
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.
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).
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.
These data demonstrated that greater total negative EB is associated with declines in lower-body performance during military operations.
The authors wish to acknowledge Dr. Scott Montain for his critical review of this manuscript, as well as the authors of the papers included in this meta-analysis, and the subjects who volunteered their time and effort to further military research.
Compliance with Ethical Standards
The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. The investigators adhered to the policies for protection of human subjects as prescribed in Army Regulation 70-25, and the research was conducted in adherence with the provisions of 32 CFR part 219. The opinions or assertions contained herein are the private views of the authors and are not to be construed as official or as reflecting the views of the Army or the Department of Defense. Any citations of commercial organizations and trade names in this report do not constitute an official Department of the Army endorsement of approval of the products or services of these organizations.
This work was supported by the U.S. Army Medical Research and Material Command.
Conflicts of interest
Nancy Murphy, Christopher Carrigan, J. Philip Karl, Stefan Pasiakos, and Lee Margolis have no conflicts of interest relevant to the content of this article.
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