A systematic review of the effects of physical training on load carriage performance.

Soldiers are often required to carry heavy loads during military operations. This article reports on a systematic literature review examining the influence of physical training on load carriage performance. Several literature databases, reference lists, and other sources were explored to find studies that quantitatively examined the effects of physical training on the time taken for individuals to complete a set distance carrying an external load, with the majority of the load contained in a backpack. Effect sizes (Cohen's d statistic) were used in meta-analyses to examine the changes in load carriage performance after various modes of physical training. Effect sizes quantified training-related changes in terms of SD units. Ten original research studies met the review criteria. Meta-analysis indicated that large training effects (≥0.8SD units) were apparent when progressive resistance training was combined with aerobic training and when that training was conducted at least 3 times per week, over at least 4 weeks. When progressive load-carriage exercise was part of the training program, much larger training effects were evident (summary effect size [SES] = 1.7SD units). Field-based training that combined a wide variety of training modes and included progressive load-carriage exercise was also very effective in improving load carriage performance (SES = 1.1SD units). Aerobic training alone or resistance training alone had smaller and more variable effects, depending on the study. This review indicates that combinations of specific modes of physical training can substantially improve load carriage performance.