Heterogeneity of rectus femoris muscle architectural adaptations after two different 14-week resistance training programmes.

Abstract

This study aimed to determine the architectural changes of rectus femoris muscle at distinctive sites of the thigh length after two different 14-week resistance training programmes. Thirty-five untrained men were randomly allocated into three different groups: conventional resistance training (n=12), isokinetic training (n=12) and control (n=11). Rectus femoris cross-sectional area, thickness and fascicle angle at two specific thigh sites (30% and 50% of the length) were assessed before and after 14weeks of unilateral knee extension exercise or control. The isometric peak torque of the knee extensors was estimated as a muscle strength index. Conventional (30%=47·4% versus 50%=14·4%) and isokinetic (30%=31·8% versus 50%=11·4%) training induced significant increases on thickness at both rectus femoris sites. While conventional training resulted in substantial increments on cross-sectional area (30%=62·1%, 50%=19·5%), isokinetic training provoked a significant increase only at the distal site (50%=64·7%). The isometric peak torque increased (22·4 and 29·6%, for conventional and isokinetic groups, respectively) after training independently of the training mode, although no significant changes were observed for any dependent variable in the control group. In general, the training modes resulted in similar changes on rectus femoris architecture, whereas their magnitude depended on the thigh site.