Abstract

Seven male strength athletes (MSA), nine physically active males (MPA), and ten physically active females (FPA) volunteered as subjects for measurements of bilateral isometric maximal force, force-time curve,maximal rate of force production (RFD), and maximal rate or relaxation (RR) of the leg extensor muscles. The measurements included also a recording of one repetion maximum (kg) during the bilateral knee extension in the specific knee extension device. The cross-sectional area (CSA) of vastus lateralis (VL) and quadriceps femoris (QF) muscles were measured by means of an ultrasonic apparatus. Muscle fiber area and fiber composition were determined from neddle biopsies taken from the vastus lateralis muscle. Maximal force and one repetition maximum in the MSA group were approximately three times the values of the FPA group. When the force values were related to CSA of the QF, the differences became smaller, but were still highly significant (p<0.001) and the values in the MSA group were almost twice (p<0.001) as high as in the FPA group. The force-time curves indicated that the rate of force development in the FPA group was loweer (p<0.05-0.001) than in the MSA and MPA groups. The mean fiber area of ST, FTa, FTb and the mean area of these fiber types differed significantly (p<0.05-0.001) among the threegroups except for ST fibers between the MPA and FPA groups. It can be concluded that not only maximal absolute force but also the maximal force per CSA differed significantly between male strength athletes, physically active males andfemales. These differences may be explained by the differences in the muscle tissue itself and maximal neural activation of the musles due to specific training and/or by sex.