Lower-Limb Dominance, Performance, and Fiber Type in Resistance-trained Men

ABSTRACTINTRODUCTIONLarge imbalances between limbs are common and potentially dangerous, yet few studies have simultaneously examined performance and physiological asymmetries. The current study examined the associations between lower limb dominance, drop-jumping kinematics, maximal strength, and myosin heavy chain (MHC) fiber type in the vastus lateralis (VL).METHODSThirteen resistance-trained men (age=24.3±2.7y; height=181.4±6.6cm; mass=87.7±11.3kg) identified their dominant (DOM) and non-dominant (ND) limb, performed drop jumps (30cm) and maximal knee extensions (1RM), and provided biopsies from both VL muscles for single fiber (109±36/limb/person) MHC fiber type identification (FT%).RESULTSAll participants selected "right" as the "preferred kicking limb" (DOM). DOM displayed a trend for a greater eccentric knee angular velocity (EKV) (p=0.083) and a significantly greater concentric KV (CKV) (p=0.002) during drop-jump. DOM also tended to be stronger than ND (64.3±11.3 vs. 61.0±8.8 kg, p=0.063). Slow-twitch (MHC I) fibers were more prevalent in DOM (p5% were present in 6/12 participants for EKV, 2/12 for CKV, 6/13 for 1RM, 12/13 for MHC I, and 11/13 for MHC IIa. However, only a single participant expressed asymmetries of >5% in all dependent variables (EKV, CKV, 1RM, MHC I, and MHC IIa).CONCLUSION: Several statistically and clinically relevant asymmetries were identified. The FT% differences between lower-limbs were large and common. The findings also appear to conclude that DOM was stronger, moved faster, and contained more MHC I. However, only 23% of participants actually displayed that result. This highlights the need to analyze and report both group and individual data; particularly when interpreting findings across multiple related, but not necessarily causal, measurements. INTRODUCTION Large imbalances between limbs are common and potentially dangerous, yet few studies have simultaneously examined performance and physiological asymmetries. The current study examined the associations between lower limb dominance, drop-jumping kinematics, maximal strength, and myosin heavy chain (MHC) fiber type in the vastus lateralis (VL). METHODS Thirteen resistance-trained men (age=24.3±2.7y; height=181.4±6.6cm; mass=87.7±11.3kg) identified their dominant (DOM) and non-dominant (ND) limb, performed drop jumps (30cm) and maximal knee extensions (1RM), and provided biopsies from both VL muscles for single fiber (109±36/limb/person) MHC fiber type identification (FT%). RESULTS All participants selected "right" as the "preferred kicking limb" (DOM). DOM displayed a trend for a greater eccentric knee angular velocity (EKV) (p=0.083) and a significantly greater concentric KV (CKV) (p=0.002) during drop-jump. DOM also tended to be stronger than ND (64.3±11.3 vs. 61.0±8.8 kg, p=0.063). Slow-twitch (MHC I) fibers were more prevalent in DOM (p5% were present in 6/12 participants for EKV, 2/12 for CKV, 6/13 for 1RM, 12/13 for MHC I, and 11/13 for MHC IIa. However, only a single participant expressed asymmetries of >5% in all dependent variables (EKV, CKV, 1RM, MHC I, and MHC IIa). CONCLUSION: Several statistically and clinically relevant asymmetries were identified. The FT% differences between lower-limbs were large and common. The findings also appear to conclude that DOM was stronger, moved faster, and contained more MHC I. However, only 23% of participants actually displayed that result. This highlights the need to analyze and report both group and individual data; particularly when interpreting findings across multiple related, but not necessarily causal, measurements. Corresponding Author: Andrew J. Galpin, Ph.D., Center for Sport Performance, Department of Kinesiology, California State University, Fullerton, Fullerton, CA 92834, E-mail: agalpin@fullerton.edu The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. No financial support was received. The authors have no conflicts of interest to report. The results of this study do no constitute endorsement by the American College of Sports Medicine. Accepted for Publication: 15 December 2017 © 2017 American College of Sports Medicine

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