Sport Differences in Fat-Free Mass Index Among a Diverse Sample of NCAA Division III Collegiate Athletes

Brandner, CF, Harty, PS, Luedke, JA, Erickson, JL, and Jagim, AR. Sport differences in fat-free mass index among a diverse sample of NCAA Division III collegiate athletes. J Strength Cond Res 36(8): 2212-2217, 2022-Fat-free mass index (FFMI) is becoming a popular metric to determine an athlete's potential for future fat-free mass accrual or to identify athletes who may be at risk for low fat-free mass (FFM). The aim of the current study was to examine sport-specific differences in FFMI among a cohort of collegiate athletes. NCAA Division III male (n = 98; age: 20.1 +/- 1.6 years, height: 1.82 +/- 0.06 m, body mass: 92.7 +/- 17.5 kg, %BF: 15.6 +/- 8.8%) and female (n = 92; age: 19.45 +/- 1.1 years, height: 1.68 +/- 0.06 m, body mass: 65.16 +/- 11.04 kg, %BF: 22.71 +/- 5.9%) athletes completed a body composition assessment using air displacement plethysmography. Fat-free mass index was calculated by dividing FFM by height squared. The mean +/- SD FFMI was significantly higher (p < 0.05) for males (23.37 +/- 2.41 kg center dot m(-2)) compared with females (17.54 +/- 1.8 kg center dot m(-2)). There was a significant main effect for sport category. Post hoc analysis indicated that throwers had a higher (p < 0.001) FFMI (mean difference, 95% confidence interval) compared with sprinters and soccer athletes (4.17, 2.03-6.32 kg center dot m(-2)), endurance and weight-sensitive athletes (4.91, 2.67-7.14 kg center dot m(-2)), and court sport athletes (4.39, 1.97-6.81 kg center dot m(-2)), respectively, among female athletes. Post hoc analysis indicated that football players had a higher (p < 0.01) FFMI than distance runners (3.89, 2.15, 5.62) and wrestlers (2.23, 0.78, 3.68), among male athletes. These findings indicate that sex differences in FFMI exist, with differences identified between sports. These findings can guide strength and nutritional programming decisions by providing sport-specific normative data profiles.