The effect of 10 weeks of concentric and eccentric strength training on quadriceps muscle distribution

Abstract

Resistance training may stimulate region-specific muscle hypertrophy. It is not presently clear whether training mode impacts on region-specific muscle growth. PURPOSE: To examine the effects of 10 wk of concentric or eccentric knee extensor (KE) training on muscle volume (MV) and distribution. METHODS: Two groups of 10 untrained men and women completed 10 wk of concentric or eccentric isokinetic KE training on an isokinetic dynamometer through a 90° range of motion at 30°s−1. Initial training consisted of 4 sets of 6 maximal repetitions 3.wk−1 (wks 1–3), which was increased to 5 sets (wks 4–7) and then 6 sets (wks 8–10). Quadriceps femoris (QF) MV was determined through magnetic resonance imaging (MRI) before and after training. Anatomical cross-sectional area (ACSA) of each QF muscle was also measured at 25% (proximal), 50% (middle) and 75% (distal) of the distance from greater trochanter to the superior border of the patella. RESULTS: There were no between-group differences in the magnitude of MV increases over the training period; QF MV increased from 1764 ± 405 to 1933 ± 422 mm3 (9.6%). Individual QF muscles increased similarly (6.6% – 13.2%). In absolute terms, there was a trend toward increases in vastus medialis ACSA being greater distally than proximally (distal =11.1 mm2, proximal = 4.07 mm2, p = 0.089), whereas the increases in vastus intermedius were significantly greater distally (8.2 mm2) than proximally (0.2 mm2). Vastus lateralis and rectus femoris increased uniformly. Region-specific changes in whole QF ACSA were highly individual, although increases were greater in the distal region compared to proximal (3-fold) in 75% of subjects. Proportional changes in vastus intermedius were in accordance with absolute increases (distal = 12.7%, proximal 0.0%). There were no other significant differences in the proportional changes in ACSA. CONCLUSION Training resulted in a significant increase in QF with increases being similar among the 4 muscles. There were substantive region-specific increases in ACSA of QF with training, but training mode did not influence these. The greater distal increase in whole QF ACSA of many of the subjects may influence the inertial properties of the thigh, with possible consequences for movement performance. The region-specific difference in proportional increases in vastus intermedius is suggestive of a non-uniform rate of hypertrophy in this muscle.