title: Fat-Free Mass Index in NCAA Division I and II Collegiate American Football Players.
abstract: Fat-free mass index (FFMI) is a height-adjusted assessment of fat-free mass (FFM), with previous research suggesting a natural upper limit of 25 kg·m in resistance trained male athletes. 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 2 National Collegiate Athletic Association Division I teams (n = 78, n = 69) and 1 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·m (mean = 23.7 ± 2.1 kg·m; 97.5th percentile = 28.1 kg·m). Differences were observed among position groups (p < 0.001; η = 0.25), with highest values observed in offensive linemen (OL) and defensive linemen (DL) and lowest values observed in offensive and defensive backs. Fat-free mass index was higher in Division I teams than Division II team (24.3 ± 1.8 kg·m vs. 23.4 ± 1.8 kg·m; p < 0.001; d = 0.49). Fat-free mass index did not differ between age groups. Upper limit estimations for FFMI seem to vary by position; although the 97.5th percentile (28.1 kg·m) may represent a more suitable upper limit for the college football population as a whole, this value was exceeded by 6 linemen (3 OL and 3 DL), with a maximal observed value of 31.7 kg·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.
authors.affiliation: 1Human Movement Science Curriculum, Department of Allied Health Sciences, University of North Carolina, Chapel Hill, North Carolina; 2Applied Physiology Laboratory, Department of Exercise and Sport Science, University of North Carolina, Chapel Hill, North Carolina; 3Department of Health and Exercise Science, Truman State University, Kirksville, Missouri; Departments of 4Athletics; and 5Physical Therapy, University of Missouri, Columbia, Missouri; and 6Office of the Chancellor, University of Missouri, Columbia, Missouri.
authors.forename: Eric T
authors.initials: ET
authors.lastname: Trexler
authors.forename: Abbie E
authors.initials: AE
authors.lastname: Smith-Ryan
authors.forename: Malia N M
authors.initials: MNM
authors.lastname: Blue
authors.forename: Richard M
authors.initials: RM
authors.lastname: Schumacher
authors.forename: Jerry L
authors.initials: JL
authors.lastname: Mayhew
authors.forename: J Bryan
authors.initials: JB
authors.lastname: Mann
authors.forename: Pat A
authors.initials: PA
authors.lastname: Ivey
authors.forename: Katie R
authors.initials: KR
authors.lastname: Hirsch
authors.forename: Meredith G
authors.initials: MG
authors.lastname: Mock
mesh_terms: D015502:Absorptiometry, Photon; D056352:Athletes; D001823:Body Composition / Q000502:physiology*; D015992:Body Mass Index; D003430:Cross-Sectional Studies; D005538:Football / Q000502:physiology*; D006801:Humans; D008297:Male; D014481:United States; D014495:Universities; D055815:Young Adult