Concentric isokinetic resistance training and quadriceps femoris cross-sectional area

The purposes of this study were to determine the effects of unilateral leg extension concentric isokinetic resistance (CIR) training on: (1) hypertrophy at the largest anatomical cross-section of the vastus intermedius, vastus lateralis, vastus medialis, and rectus femoris muscles in the trained and untrained limbs and (2) strength of the quadriceps femoris muscle group in the trained and untrained limbs. Sixteen untrained young adult males [mean age 24.7 ± 5.1 (SD) years] volunteered to serve as subjects. The subjects were divided into two groups: (1) training group (TG, n = 8) and (2) control group (CG, n = 8). The TG performed six sets of ten repetitions of extension of the non-dominant leg at 120°/s three times per week for 8 weeks on a Cybex II isokinetic dynamometer. The CG did not train. Pretraining and post-training leg extension peak torque at 120°/s and the largest anatomical cross-section of each muscle of the quadriceps femoris were determined utilizing a Cybex II dynamometer and magnetic resonance imaging scanner, respectively. The results indicated a significant (P < 0.05) increase (4.6%) in the CSA of the muscles of the non-dominant (trained) quadriceps femoris as well as significant (P < 0.05) increases in both non-dominant (trained) and dominant (untrained) quadriceps femoris strength (17.7 and 9.3%, respectively). There was no hypertrophy of the muscles of the dominant (untrained) limb. These data indicated that leg extension CIR training resulted in significant increases in both CSA and strength of the non-dominant (trained) quadriceps femoris as well as a significant increase in the strength, that was not accompanied by muscular hypertrophy, of the dominant (untrained) limb.