Purpose: Less lean body mass may limit one’s ability to produce adequate muscle forces to safely control landing from a jump, thus increasing the risk for injury. The primary objective of this study was to determine the effect of lower extremity lean mass (LELM) and eccentric muscle strength on lower extremity energy absorption (EA) during a drop jump landing.
Methods: Seventy athletic subjects (35 men and 35 women) were measured for LELM with dual-energy x-ray absorptiometry, maximal eccentric strength of the quadriceps (QuadECC) and hamstrings (HamECC), and lower extremity joint energetics during the initial landing of a drop jump. A mediation analysis examined the extent to which LELM predicted EA at each lower extremity joint (EAHIP, EAKNEE, and EAANK) and subsequently whether these relationships were mediated by each subject’s maximal eccentric strength capabilities.
Results: LELM was a significant predictor of EAKNEE (R2 = 0.22, P < 0.01) in females but not in males (R2 = 0.03, P = 0.16). In females, QuadECC was a significant mediator of the effect of LELM on EA at the knee (ab = 179.72, 95% confidence interval [CI] = 10.43–423.42) and ankle (ab = 1.71, 95% CI = [0.16, 3.94]), whereas HamECC was a significant mediator of the relationship between LELM and EAHIP (ab = 4.89, 95% CI = 2.05–8.40). No significant relationships were observed in males.
Conclusions: LELM was a significant factor in energetic capabilities for females but not males. For females, this relationship was evident secondary to the stronger underlying relationship between maximal strength and EA. Thus, the maximal eccentric strength capabilities may be a more important determinant of energetic behaviors compared with the available quantity of lean mass alone. More work is needed to investigate these relationships and to reveal the underlying sex-specific mechanisms that determine EA capabilities.
1Department of Kinesiology, California State University, Northridge; Northridge, CA; 2Department of Kinesiology, The University of North Carolina at Greensboro, NC; and 3Department of Educational Research Methodology, The University of North Carolina at Greensboro, NC
Address for correspondence: Melissa M. Montgomery, Ph.D., A.T.C., Department of Kinesiology, California State University, Northridge, 18111 Nordhoff Street, Northridge, CA 91330-8287; E-mail: firstname.lastname@example.org.
Submitted for publication February 2012.
Accepted for publication July 2012.
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