External Compressive Force Level Influences Positive Effect Of Blood Flow Restriction On Muscle Weakness

PURPOSE: To examine whether two different external compressive forces for the blood flow restriction influence the attenuation of muscle weakness in lower extremity. METHODS: Seventeen male healthy subjects participated in this study. The left ankle of all subjects was immobilized for two weeks using a cast and they are instructed to use crutches during locomotion. During the experimental period, subjects were divided into three groups as follows: blood flow to the lower extremity was restricted by the application of external high compressive force (HCF) group (200 mmHg), low compressive force (LCF) group (50 mmHg), and control (CON) group (no intervention). Percent changes (from pre to post) in knee extensor-flexor muscle strength of angular speed of 60, 180 and 300 deg/sec under concentric contraction (CC60, 180 and 300) and 60 and 180 deg/sec under eccentric contraction (EC60 and 180) were measured. RESULTS: The percent changes in knee extensor torques after CC60 and EC180 in the HCF group were significantly smaller than those in the LCF and CON groups (CC60: −2.0 ± 6.3%, −16.3 ± 8.5%, and −21.9 ± 7.0%, EC180: 0.1 ± 10.5%, −22.6 ± 7.8%, and −25.7 ± 8.5%, p < 0.01 and 0.05). The percent changes in knee flexor muscle torques after EC60 in the HCF and LCF groups were significantly smaller than that in the CON group (−2.3 ± 5.4%, −3.4 ± 4.7%, and −18.9 ± 9.6%, p < 0.01 and 0.05). CONCLUSIONS: The positive effect of blood flow restriction on the muscle weakness depends on the external compressive force.