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


  • The authors are grateful to Dr O.M. Rutherford for her comments on the manuscript. We feel indebted to Dr A. Castagna and to all those who volunteered for the training. The collaboration of Mr Francesco Conti in making the facilities of his Sports Club available for this study was greatly appreciated.

Dr M. V. Narici Département de Physiologie, Faculté de Médicine, Centre Médical Universitaire, 1, rue Michel-Servet, 1211 Genève 4, Switzerland


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 18.8±7.2% (P<0.001) and 19.3±6.7% (P<0.001) in the distal and proximal regions respectively, and by 13.0±7.2% (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 29.6±7.9%–21.1±8.6% (P<0.01-0.05) between 100° and 160° of knee extension, but no change in the optimum angle (110°-120°) for torque generation was found. A 12.0±10.8% (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.