MUSCLE STRENGTH AND MRI DETERMINED THIGH MUSCLE VOLUME IN YOUNG GIRLS980

Abstract

The study examined the relationship between isokinetic leg strength and total thigh muscle volume (TMV), determined by magnetic resonance imaging(MRI). Gravity corrected concentric knee extension and flexion (ROM 90°-180°) of 23 girls (age, 9.9 ± 0.2y; stature, 1.33 ± 0.06m; mass, 31.8 ± 7.6 kg), were determined on the right leg, using a calibrated isokinetic dynamometer, at testing velocities of 0.52, 1.04, 1.56, 2.09, and 3.15 rads.s-1. Highest mean absolute peak extension torque(61.4 ± 13.7 Nm), and peak flexion torque (40.4 ± 10.5 Nm) occurred at 0.52 rads.s-1. MRI scans were taken using a Philips Gyroscan T5 II, over the right thigh. Measurement was from the head to the base of the femur, scanning from medial to lateral in 6 mm contiguous slices. Volumes for each slice were obtained by multiplying the area of each component by the slice thickness. Individual volumes were summed to obtain TMV. Mean TMV was 1.78 ± 0.32 1. Significant correlation coefficients were demonstrated between TMV and right leg absolute peak extension torques at all velocities (range, r = 0.76 to 0.88, P <0.05), and absolute peak flexion torques at all velocities (range, r = 0.65 to 0.74, P <0.05). However, TMV was not significantly related (P <0.05) to peak extension or flexion torques expressed relative to body mass (Nm.kg-1) or as allometric power function ratios (Nm.kg-0.73, extension; Nm.kg-0.83, flexion). In conclusion, TMV in young girls is not significantly correlated with isokinetic leg strength, when the influence of body mass is controlled using either ratio or allometric scaling techniques.