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Journal of Strength and Conditioning Research: January 2010 - Volume 24 - Issue - p 1
doi: 10.1097/01.JSC.0000367228.45977.a0
Abstract
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1.) To examine mean percent body fat (BF, %) and Body Mass Index (BMI) values across three American football position groupings, skill (SK), big skill (BSK) and down linemen (LN). 2.) To examine the relationship between BF and BMI and the following performance measures: vertical jump (VJ, in.), 1-RM power clean (PC, lbs.), 1-RM back squat (BS, lbs.), 1-RM bench press (BP, lbs.), 20m sprint (20S, sec.), and pro-agility (PRO, sec.). Body composition data, (BF and BMI) were measured on 54 Division III varsity football players with a minimum of one year of participation in a collegiate strength and conditioning program. Performance measures (VJ, PC, BS, BP, 20S, PRO) were collected on 38 of the 54 athletes over three separate testing sessions within a one week period. The following mean values were found for each body composition variable overall and within each group (n = 54): BF: Overall (17.6% ± 5.6), SK (14.1 ± 3.6), BSK (17.9 ± 3.8), LN (22.4 ± 5.7) BMI: Overall (28.8 ± 3.9), SK (25.9 ± 1.8), BSK (29.4 ± 2.2), LN (32.5 ± 3.8) There was a significant interaction (p < 0.001) across groups for the body composition data (n = 54). A Tukey post-hoc analysis revealed the following results for BF and BMI, respectively: The LN group was significantly higher than the BSK (p = .021; p = .006) and SK (p < 0.001; p < 0.001) groups. The BSK group was significantly higher than the SK (p = .040; p = .001) group. Examination of the performance measures showed significant correlations between BF and BMI and the following values for the group as a whole (n = 38): BF: BP (r = .494; p = .002), 20S (r = .728; p < 0.001), PRO (r = .724; p < 0.001) and VJ (r = −.630; p < 0.001). BMI: BS (r = .393; p = .015), BP (r = .549; p < 0.001), 20S (r = .713; p < 0.001), PRO (r = .735; p < 0.001) and VJ (r = −.713; p < 0.001). Additionally, there was not a significant relationship seen between VJ and PC (r = .133, p = .427). 1.) BMI in this study was lower and percent body fat higher than has been previously reported in studies examining Division I football players (Kaiser et al., 2008) 2.) Literature has documented the increase in the weight of football players over the past two decades (Harp & Hecht, 2005). However, according to the current study this increase in weight does not correlate positively with power, speed or agility variables. Also, according to this study PC was not significantly related to VJ which contradicts results previously reported with competitive Olympic weightlifters (Carlock et al., 2004). Previous research examining the relationship between hang-clean (HC) and VJ in male lacrosse players also found no relationship (Thompson et al., 2008). 1.) Due to the need for explosive power, agility, and speed in football optimal body composition can be critical. This study has shown that body composition can have a negative impact on performance variables possibly giving evidence to the importance of nutrition at all levels. 2.) The finding that significant relationships exist between body structure (BF, BMI) and maximal strength (BP, BS) but not power (PC) indicates alternative methods may be better for assessing power in larger athletes.

© 2010 National Strength and Conditioning Association