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Cardiovascular Demand Differences Between Male and Female US Marine Recruits During Progressive Loaded Hikes
Ben Schram1, Robin Orr1, Brenda Niederberger2,3
1Tactical Research Unit, Bond University, Robina, QLD, Australia.
Insights
Female US Marine recruits experienced higher cardiovascular demand during loaded hikes than males, especially with loads over 15 kg. This highlights sex-based differences in physical strain during military load carriage.
Area of Science:
- Exercise Physiology
- Military Science
- Human Performance
Background:
- Female soldiers often have lower body mass than males, yet carry similar occupational loads.
- Understanding sex-based differences in cardiovascular response to load carriage is crucial for military readiness and training.
Purpose of the Study:
- To compare the cardiovascular demand between male and female US Marine recruits during progressive loaded hikes.
- To identify at what load carriage intensity sex-based differences in cardiovascular response become significant.
Main Methods:
- 565 male and 364 female US Marine recruits participated in 6 progressive loaded hikes over 6 weeks.
- Cardiovascular response (average heart rate [HRavg], HR maximum [HRmax]) and pace were measured using wrist-worn monitors.
- Independent samples t-tests were used for sex-based comparisons, with significance adjusted for multiple comparisons (p < 0.008).
Main Results:
- Female recruits had significantly lower body mass, resulting in heavier relative loads (17-33% BM) compared to males.
- No significant differences in pace were observed between sexes across all hikes.
- Female Marines exhibited significantly higher HRavg and HRmax compared to males during hikes with loads exceeding 15 kg (approximately 25% BM).
Conclusions:
- Female Marines experience greater cardiovascular strain than male Marines during load carriage events when carrying loads greater than 15 kg.
- These findings suggest that training and load prescription may need to consider sex-specific physiological responses to optimize performance and mitigate risk in military populations.
Abstract:
Schram, B, Orr, R, Niederberger, B, Givens, A, Bernards, J, and Kelly, KR. Cardiovascular demand differences between male and female US Marine recruits during progressive loaded hikes. J Strength Cond Res 38(8): e454-e458, 2024-Despite having to carry the same occupational load, female soldiers tend to be lighter than male soldiers. The aim of this study was to determine the differences in cardiovascular load between female and male US Marine recruits during progressive load carriage hikes. United States Marine Corps recruits (565 male recruits; 364 female recruits) completed 6 loaded hikes over 6 weeks (1: 10 kg, 30 minutes; 2: 10 kg, 45 minutes; 3: 15 kg, 30 minutes, 4: 15 kg, 45 minutes; 5: 20 kg, 30 minutes; 6: 20 kg, 45 minutes) during which cardiovascular response was measured. Average heart rate (HRavg), HR maximum (HRmax), and pace were measured via a wrist-worn physiological monitor. Independent sample t -tests were conducted to compare between sexes, with significance set at 0.008 after adjusting for multiple comparisons. The average female recruit had significantly lower body mass (BM) compared with the average male recruit ( p < 0.001) and thus carried a significantly heavier relative load. (10 kg ∼17%, 15 kg ∼25%, 20 kg ∼33%, p < 0.001). There were no significant differences in pace in any hike, and no significant differences were found in HRavg or HRmax when comparing female and male Marines during Hike 1. For female Marines, HRavg was significantly higher compared with male Marines during Hike 2 (+6.5 b·min -1 , p < 0.001) and Hike 3 (+7.4 b·min -1 , p < 0.001), and both HRavg and HRmax were significantly higher in Hike 4 (+11.9 b·min -1 , +8.4 b·min -1 , p < 0.001), Hike 5 (+7.7 b·min -1 , +7.9 b·min -1 , p < 0.001), and Hike 6 (+6.9 b·min -1 , +7.1 b·min -1 , p < 0.001), respectively. Female Marines endured greater cardiovascular demand compared with male Marines during load carriage events when carrying loads greater than 15 kg (∼25% BM).
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