Thigh anthropometric changes in response to six weeks of voluntary and electromyostimulation-superimposed voluntary training in young men (Book chapter)
Zhou, S, Bezerra, P, Crowley, Z & Hooper A 2009, 'Thigh anthropometric changes in response to six weeks of voluntary and electromyostimulation-superimposed voluntary training in young men', in PA Hume & AD Stewart (eds), Kinanthropometry XI: 2008 Pre-Olympic Congress Anthropometry Research, Sport Performance Research Institute New Zealand, Auckland University of Technology, Auckland, New Zealand, pp. 50-68.
The aims of this study were to determine the cross sectional area (CSA) of the quadriceps muscle using MRI technique, and the relationships between muscle CSA, thigh circumference and skinfold, and strength gain, in the exercised limb and unexercised contralateral limb, in response to six weeks of unilateral voluntary knee extension (VC) or electromyostimulation (EMS)-superimposedon-VC (EV) training. Thirty-one healthy young men were randomly assigned into control, VC and EV training groups. The training program was applied to the right leg and included three sets of 10 maximal isometric knee extension contractions (MVC) per session, with (EV) or without EMS (VC), three sessions per week. The MVC was measured pre and post the six-week period and the anthropometric variables were measured at the middle-thigh, and 5 cm proximal and 5 cm distal to the middle-thigh levels for both legs. Results demonstrated that the training significantly improved muscular strength of the trained limb in both VC (19.6%) and EV (34.5%), while the EV also caused strength gain in the contralateral limb (36%, p<0.01). The CSA of the quadriceps in the trained leg increased significantly at all three locations (4.6-7.5%, p<0.01), and the relative strength gain of the trained limb showed a moderate correlation with the increase of CSA-quadriceps at the middle-thigh level (r=0.44, p<0.05). The CSA of the thigh did not change significantly because the CSA of the thigh muscles increased while the CSA of the adipose tissues decreased. The thigh circumferences did not change significantly at any locations, nor in any leg or group, although circumferences taken at the middle-thigh and 5 cm proximal to the mid-thigh levels demonstrated moderate correlations to the strength variation (r=0.43 and 0.53, p<0.01). Skinfolds showed high correlations with thigh circumference (r=0.74-0.87, p<0.01) and CSA-adipose (r=0.84-0.93, p<0.01), however had no significant correlations to relative changes in MVC and CSA-quadriceps. It is evident that the girth and skinfolds measurements did not sensitively reflect hypertrophic change in specific muscles and the locations of measurement must be carefully selected in an attempt to interpret training effects.