(61) SEX AND BODY COMPOSITION CAN INFLUENCE PLANK PERFORMANCE IN RESERVE OFFICERS’ TRAINING CORPS CADETS

The U.S. Army implemented a maximum plank assessment on their Army Combat Fitness Test (ACFT) and it is the only event graded on a sex-neutral scale. Literature has supported that males and females do not differ on assessments of core performance. However, males and females do differ on anthropometric and body composition measurements. These variables are well known to effect physical performance. Currently, there is conflicting literature identifying sex differences and body composition correlations with plank performance in a tactical population. 

Purpose:  The purpose of this study was to analyze differences in plank performance between the sexes and the relationship between body composition and plank performance in Army Reserve Officers’ Training Corps (ROTC) cadets. 

Methods:  77 ROTC cadets (58 males, 19 females, age=21.49±2.83 years) volunteered to participate. Cadets’ height was recorded via stadiometer, total body mass (TBM) via digital scale, and body fat percentage (BF%) via handheld bioelectrical impedance analysis. A plank was conducted for maximum time per ACFT standards. An independent t-test assessed differences in body composition (TBM; fat mass(FM); fat free mass(FFM); BF%) and plank performance between sexes. Pearson’s correlations assessed relationships between TBM, body composition, and plank performance. A sequential linear regression for plank performance was conducted with BF% and BF% + sex. An independent samples t-test assessed differences in plank performance between 10 male and 10 female cadets who were FM case-matched.  = 0.05 

Results:  Male cadets had significantly greater TBM (78.56±15.34kg vs 67.04±10.28kg, p=0.002) and FFM (65.74±7.77kg vs 50.07±4.71kg, p< 0.001) and significantly less FM (13.76±6.66kg vs 20.55±5.33kg,p< 0.001) and BF% (16.63±5.87 vs 28.72±4.49kg, p< 0.001) than females. Males significantly outperformed females in the plank (170.36±70.57s vs 129.28±42.58s, p=0.012). There was a significant, negative correlation between BF% (R=-0.51, p< 0.01) and FM (R=-0.45, p< 0.01) with plank performance. There were no significant correlations with FFM (R=-0.18, p=0.13) or TBM (R=0.22, p=0.12) and plank performance. In the first linear model (R² = 0.242, p< 0.001), BF% was a significant predictor of plank performance (p< 0.001). The addition of sex in the second model did not explain any more variance (R²=0.231, p< 0.001; ²=-0.011, p=0.605) nor was sex significant (p=0.605). When case-matched, there was no significant difference in plank performance (p=0.057). 

Conclusions:  Contrary to previous research, there was a significant difference in core endurance, as assessed by a maximum plank, between males and females in this sample. The difference in plank performance between the sexes could be due to females having greater BF% and FM. When added to the regression equation, sex did not explain any more variance than BF% alone. This is further supported by there being no difference between the sexes when case-matching for FM. A limitation of the current study was the large sample size difference between males and females but it is similar to that of active duty military populations. PRACTICAL APPLICATIONS: For ROTC cadets to perform well on the plank, regardless of sex, practitioners should emphasize both core endurance training and decreasing body fat. Commanders should be aware that because the ACFT scoring scale for the plank is sex-neutral, females may score fewer points than their male counterparts.


Acknowledgements: None