Body Composition, Eicosapentaenoic Acid, and Vitamin D are Associated with Army Combat Fitness Test Performance

ABSTRACT

Background

The Army Combat Fitness Test (ACFT), an updated and newly developed metric to assess combat readiness, may require specialized exercise and nutritional interventions. The purpose of this cross-sectional study was to investigate the relationship between body composition, erythrocyte long-chain omega-3 polyunsaturated fatty acids (LC n-3 PUFA), serum vitamin D (VITD) and ACFT performance.

Methods

Sixty cadets (43 males, 17 females; 20.9 ± 3.8 years; 173.6 ± 10.2 cm; 75.6 ± 13.7 kg) completed the 6-event ACFT (3-repetition maximum trap-bar deadlift [3DL], standing power toss [SPT], hand-release pushups [HRPU], sprint-drag-carry shuttle run [SDC], leg tuck [LTK], or plank [PLK], and 2-mile run [2MR]), body composition analysis via dual-energy x-ray absorptiometry (percent body fat [%BF], lean body mass [LBM], fat-free mass index [FFMI (LBM+bone mineral content)]), and an omega-3 questionnaire. A sub-sample (n = 50) completed blood draws for fatty acid (eicosapentaenoic acid [EPA] and docosahexaenoic acid [DHA]) and VITD analysis. Significance was set at p < .05.

Results

Lower %BF predicted better performance on all ACFT events (p < .05), except the PLK. Higher LBM was predictive of better performance on the 3DL, SPT, and SDC (p < .05), but no other events. Adjusted FFMI was positively correlated with the 3DL, SPT, HRPU, SDC, and ACFT scores (p < .01 for all). Cadet EPA and DHA dietary intake and omega-3 erythrocyte status was well below established recommendations (25.6 ± 33.9 mg, 58.3 ± 78.1 mg, respectively) and an omega-3 index (O3i = %EPA+%DHA in erythrocytes) of 3.96 ± 1.36%, respectively. EPA was associated with better performance on the 3DL (r = 0.280, p = .049), SPT (r = 0.314, p = .027), LTK (r = 0.316, p = .047), and PLK (r = 0.837, p = .003). After adjusting for body composition, erythrocyte EPA only remained predictive of PLK scores (p = .006). Every 0.1% increase in EPA translated into 5.4 (95% CI: 2.1, 8.8) better PLK score. The O3i or DHA were not associated with any performance variables. Cadets’ average serum VITD status was 38.0 ± 14.9 ng∙ml⁻¹. VITD was associated with 3DL (r = 0.305, p = .031), HRPU (r = 0.355, p = .011), 2MR (r = 0.326, p = .021), and total ACFT score (r = 0.359, p = .011). VITD remained predictive of each event after adjustment for body composition. Every 10 ng∙ml⁻¹ increase in VITD was associated with 3-point increase in 3DL, HRPU, 2MR scores, and a 13-point increase in the total ACFT score.

Conclusions

Our data highlight the importance of measures of muscularity, LBM and FFMI, on ACFT performance. Additionally, EPA and VITD status is associated with various strength, power, and muscular and aerobic endurance components of the ACFT. While these results could help professionals better assess and train military personnel, especially since these measures are modifiable through exercise and dietary interventions, they are ultimately hypothesis generating and warrant further exploration.

KEYWORDS:

• Military
• fat-free mass index
• omega-3 index
• 25-hydroxyvitamin D
• sport performance

Acknowledgments

The authors would like to thank the cadets for participating in the study.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Authorship

JLH, JSF, and LKF conceptualized the concept and approach for this study. JLH, JSF, and LKF assisted with funding acquisition. JLH, JSF, JMM, JMM, TJC, RT were involved in data acquisition. JLH and JMM drafted the first manuscript. JLH analyzed the data and prepared the tables and figures. All authors assisted with data interpretation, critically appraised and revised the manuscript, and approved the final version.

Additional information

Funding

This research was supported by Faculty Discretionary Funds” (from Baylor University, ID#: 8000038 under Dr LesLee K. Funderburk);