Fat-Free Mass Index in NCAA Division I and II Collegiate American Football Players

ABSTRACTFat-free mass index (FFMI) is a height-adjusted assessment of fat-free mass, with previous research suggesting a natural upper limit of 25 kg[BULLET OPERATOR]m in resistance-trained males. The current study evaluated upper limits for FFMI in collegiate American football players (n=235), and evaluated differences between positions, divisions, and age groups. The sample consisted of two NCAA Division I teams (n=78, n=69), and one Division II team (n=88). Body composition was assessed via dual-energy x-ray absorptiometry and used to calculate FFMI; linear regression was used to normalize values to a height of 180 cm. Sixty-two participants (26.4%) had height-adjusted FFMI values above 25 kg[BULLET OPERATOR]m (mean = 23.7 ± 2.1 kg[BULLET OPERATOR]m; 97.5 percentile = 28.1 kg[BULLET OPERATOR]m). Differences were observed among position groups (p < 0.001; η = 0.25), with highest values observed in offensive and defensive linemen, and lowest values observed in offensive and defensive backs. FFMI was higher in Division I teams than Division II (24.3 ± 1.8 vs. 23.4 ± 1.8 kg[BULLET OPERATOR]m; p < 0.001; d = 0.49). FFMI did not differ between age groups. Upper limit estimations for FFMI appear to vary by position; while the 97.5 percentile (28.1 kg[BULLET OPERATOR]m) may represent a more suitable upper limit for the college football population as a whole, this value was exceeded by six linemen (3 OL, 3 DL), with a maximal observed value of 31.7 kg[BULLET OPERATOR]m. Football practitioners may use FFMI to evaluate an individual’s capacity for additional FFM accretion, suitability for a specific position, potential for switching positions, and overall recruiting assessment.