Characterization of Female US Marine Recruits: Workload, Caloric Expenditure, Fitness, Injury Rates, and Menstrual Cycle Disruption during Bootcamp

Abstract

Basic training is centered on developing the physical and tactical skills essential to train a recruit into a Marine. The abrupt increase in activity and energy expenditure in young recruits may contribute to high rates of musculoskeletal injuries, to which females are more susceptible. To date, the total workload of United State Marine Corps (USMC) bootcamp is unknown and should include movement around the military base (e.g., to and from dining facilities, training locations, and classrooms). Thus, the purpose of this effort was to quantify workload and caloric expenditure, as well as qualitatively assess the impact of female reproductive health and injury rates in female recruits. Female recruits (n = 79; age: 19.1 ± 0.2 years, weight: 59.6 ± 0.8 kg, height: 161.6 ± 0.7 cm) wore physiological monitors daily throughout 10 weeks of USMC bootcamp. Physical fitness test scores, physiological metrics from wearables, injury data, and menstrual cycle information were obtained. Female recruits on average expended 3096 ± 9 kcal per day, walked 11.0 ± 0.1 miles per day, and slept 5:43 ± 1:06 h:min per night throughout the 10 weeks of bootcamp. About one-third (35%) of female recruits sustained an injury. In a subset of females that were not taking birth control and had previously been menstruating, 85% experienced cycle dysfunction during boot camp. High levels of physical activity and caloric expenditure, coupled with the stress of a new environment and insufficient sleep, may lead to alterations in female reproductive cycles and musculoskeletal injuries in young USMC recruits.

Cardiovascular Demand Differences Between Male and Female US Marine Recruits During Progressive Loaded Hikes

“…Given this association between elements of fitness, which are generally lower in female service members, and loaded hike performance, a greater focus on conditioning female members before enlistment would be a logical recommendation ( 23 , 33 ). Supporting this approach, research suggests that female personnel tend to make greater improvements in fitness in military training than male recruits due to female recruits entering training at a lower level of their true potential ( 2 , 10 ). Apart from strength and aerobic fitness conditioning, a greater focus on load carriage conditioning should be encouraged for the USMC context before enlistment for female personnel ( 16 ).…”

“…and were worn continuously, except for removal for charging and data downloads by directing staff, which was approximately 4 hours total per week. These devices have used and validated previously within this population ( 10 , 20 ). Anthropometric data were collected by sports medicine and athletic trainer staff at medical intake with height measured with a stadiometer and weight on a scale.…”

“…In the United States Marine Corps (USMC), and in line with global data, injuries are greatest in young Marines during periods of high volumes of intense exercise, such as in initial training ( 16 ). This training period in the USMC is a 13-week program inclusive of 3 weeks of administrative processing and 10 weeks of tactical training ( 10 ). It is an entry-level training that male and female recruits complete to gender-neutral standards before progressing to additional occupational-specific training.…”

“…Given the gender-neutral training standards, which correspond to the gender-neutral occupational requirements within the military, female recruits complete the same progressive loaded hikes as male recruits in USMC basic training. Because female recruits are generally smaller in stature and lighter in mass than male recruits ( 10 , 27 ), this additional load is typically a greater relative load than those carried by their male counterparts. In addition, female recruits, in general, have a lower aerobic capacity than male recruits ( 2 ), which leads to a generally greater cardiovascular workload for the same task ( 13 ).…”

Physical performance and body composition reference values for modern US Marine Corps women

“…Body composition and fitness is evolving as Marine women train harder and differently than they used to and as physique changes with greater intensity and volume of strength and endurance training. 38 With more complete female integration into Marine Corps training and roles, further changes in average physical fitness and physical performance of Marine women can be reason-With current trajectories for obesity in the civilian population, the differences between Marine women and civilian women can also be predicted to increase. For women in this sample, 'lean' is represented by an average 30% BF with a 5th-95th percentile range of 20%-40% BF; for the US civilian population based on NHANES data, the mean is closer to 40% BF.…”