Human quadriceps cross-sectional area, torque and neural activation during 6 months strength training (original) (raw)

Human quadriceps cross-sectional area, torque and neural activation during 6 months strength training. Acta Physiol Scand 157, 175–186. Received 2 January 1995 accepted 11 December 1995. ISSN 0001–6772. De3 partement de Physiologie, CMU, 1211 Gene9 ve, Switzerland, Department of Anatomy, University of Bern, Switzerland, Servizio di Risonanza Magnetica, Centro S. Pio X, Milano, Italy and Reparto di Fisiologia, Istituto di Tecnologie Biomediche Avanzate, CNR, Milano, Italy. Quadriceps muscle and fibre cross-sectional areas (CSA), torque and neural activation were studied in seven healthy males during 6 months of weight training on alternate days with six series of eight unilateral leg extensions at 80% of one repetition maximum. After training, the quadriceps cross-sectional area increased by 18.8p7.2% (P􏱌0.001) and 19.3p6.7% (P 􏱌 0.001) in the distal and proximal regions respectively, and by 13.0p7.2 % (P 􏱌 0.001) in the central region of the muscle. Hypertrophy was significantly different between and within the four constituents of the quadriceps. Biopsies of the vastus lateralis at mid-thigh did not show any increase in mean fibre cross-sectional area. Maximum isometric voluntary torque increased by 29.6p7.9%–21.1p8.6% (P􏱌0.01k0.05) between 100m and 160m of knee extension, but no change in the optimum angle (110mk120m) for torque generation was found. A 12.0p10.8% (P 􏱌 0.02) increase in torque per unit area together with a right shift in the IEMG-torque relation and no change in maximum IEMG were observed. Time to peak isometric torque decreased by 45.8% (P􏱌0.03) but no change in time to maximum IEMG was observed. In conclusion, strength training of the quadriceps results in a variable hypertrophy of its components without affecting its angle-torque relation. The increase in torque per unit area, in the absence of changes in IEMG, may indicate changes in muscle architecture. An increase in muscle-tendon stiffness may account for the decrease in time to peak torque.