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Influence of muscle-tendon unit structure on rate of force development during the squat, countermovement, and drop jumps
Earp, Jacob E. Kraemer, William J. Cormie, Prue Volek, Jeffery S. Maresh, Carl M. Joseph, Michael Newton, Robert U.
Earp, Jacob E.
Kraemer, William J.
Cormie, Prue
Volek, Jeffery S.
Maresh, Carl M.
Joseph, Michael
Newton, Robert U.
Abstract
Previous research has highlighted the importance of muscle and tendon structure to stretch shortening cycle performance. However, the relationships between muscle and tendon structure to performance are highly dependent on the speed and intensity of the movement. The purpose of this study was to determine if muscle and tendon structure is associated with the rate of force development (RFD) throughout static squat jump (SJ), countermovement jump (CMJ), and drop jump (DJ; 30-cm height). Twenty-five strength- and power-trained men participated in the study. Using ultrasonography, vastus lateralis (VL) and gastrocnemius (GAS) pennation (PEN) and fascicle length (FL), and Achilles tendon (AT) thickness and length were measured. Subjects then performed SJ, CMJ, and DJ, during which RFD was calculated over time 5 distinct time intervals. During CMJs, early RFD could be predicted between 0 and 10 milliseconds by both GAS-FL (r2 = 0.213, [beta] = 0.461) and AT-length (r2 = 0.191, [beta] = -0.438). Between 10 and 30 milliseconds GAS-FL was a significant predictor of CMJ-RFD (r2 = 0.218, [beta] = 0.476). During DJ, initial RFD (0-10 milliseconds) could be significantly predicted by GAS-FL (r2 = 0.185, [beta] = -0.434), VL-PEN (r2 = 0.189, [beta] = 0.435), and GAS-PEN (r2 = 0.188, [beta] = 0.434). These findings suggest that longer ATs may have increased elasticity, which can decrease initial RFD during CMJ; thus, their use in talent identification is not recommended. The GAS fascicle length had an intensity-dependent relationship with RFD, serving to positively predict RFD during early CMJs and an inverse predictor during early DJs. During DDJs, subjects with greater PEN were better able to redirected initial impact forces. Although both strength and plyometric training have been shown to increase FL, only heavy strength training has been shown to increase PEN. Thus, when a high eccentric load or multiple jumps are required, heavy strength training might be used to elicit muscular adaptations that are suited to fast force production during jumping.
Keywords
vertical jump, fascicle, pennation, achilles tendon, tendon length, impulse
Date
2011
Type
Journal article
Journal
Journal of Strength and Conditioning Research
Book
Volume
25
Issue
2
Page Range
340-347
Article Number
ACU Department
Centre for Exercise and Nutrition
Faculty of Health Sciences
Faculty of Health Sciences
Collections
Relation URI
Source URL
Event URL
Open Access Status
License
File Access
Controlled