1991 Volume 18 Issue 4 Pages 397-403
The purposes of this study were two-fold, 1) to evaluate the influence of bed rest on the strength of knee extensor and flexor, and 2) to estimate the effect of muscle strengthening exercise on knee extensor during bed rest. First, in ten patients who underwent orthopaedic surgery for unilateral hip joint disorder, we evaluated the isokinetic peak torques of knee extensor and flexor in their uninvolved legs concentrically at 30°/sec, 120°/sec, 210°/sec and eccentrically at 30°/sec before and after bed rest. Thigh girth and thigh skinfold thickness were also measured at the 5, 10, 15 cm above the superior pole of patella. The mean duration of bed rest was 28.9 ± 15.0 days after surgery. The patients were not exercised for their uninvolved thigh muscles during bed rest. Second, eight patients, who also underwent orthopaedic surgery for unilateral hip joint disorder, took the same evaluation. The mean duration of bed rest was 32.4 ± 11.1 days. The patients were exercised for their quadriceps in the uninvolved leg by straight leg raising (SLR) against manual maximum resistance five times a day during bed rest. Isokinetic peak torques of knee extensor in non-exercised patients showed significant losses after bed rest, but no significant changes in knee flexor peak torques in all conditions. Significant decreases of thigh girth were found after bed rest, whereas thigh skinfold thickness showed no significant change. On the other hand, in exercised group, no effects of SLR were found on increasing in torques of knee extensor and in thigh girth, but SLR could avoid torque reduction of knee extensor only at 30°/sec concentrically. The possible explanation for the selective strength reduction of the quadriceps might be that the loss of weight-bearing stimulus due to bed rest gave more influence on the quadriceps, antigravity muscle, than on the hamstrings. It might be considered that thigh muscle strengthening exercises should include the training with weight-bearing stimulation such as with a condition of closed kinetic chain of lower extremity.
