Progressive resistance exercise training of the hypotrophic quadriceps muscle in man. The effects on morphology, size and function as well as the influence of duration of effort.

The effects of progressive resistance exercise (PRE) training for 4 weeks on the hypotrophic quadriceps muscle were investigated in 23 young healthy male soccer players, who had been immobilized in a plaster cast 4-6 weeks after knee ligament injuries. The subjects were allocated to two training regimes where the injured leg was trained for periods of varying duration, whereas the intensity and frequency of exercise were alike in the two groups. However no significant differences were detected between the two training groups. In the whole material the lean thigh volume of the injured leg increased from 4.09 to 4.47 litres (p less than 0.001), whereas the fat component of the thigh was unchanged. The dynamic strength (1 RM) of the injured leg increased from 14.0 kg to 27.0 kg and amounted to 87% of the control leg after 4 weeks of training. At this time the maximum isometric strength amounted to 114 Nm, which was 63% of strength in the control leg. Succinate dehydrogenase (SDH) in homogenates of muscle biopsy sample increased (i.e. 20%, p less than 0.05) to the same level as found in the control leg. No changes in phosphofructokinase (PFK) were observed. The type I fibre distribution was lower in the immobilized leg than in the control leg. These results indicate that, following muscular hypotrophy resulting from 4-6 weeks of immobilization, dynamic exercise can restore the oxidative potential, whereas the size and strength are only partly recovered.