Low-Intensity Exercise with Blood Flow Restriction Increases Muscle Strength without Altering hsCRP and Fibrinogen Levels in Healthy Subjects

Strengthening exercise combined with blood flow restriction potentially increases muscle strength. This type of exercise does not require heavy weight liftings and is a feasible method to be performed by persons suffering illnesses. However, strengthening exercise may induce inflammatory responses due to muscle and vascular endothelial damage. This study aimed to investigate alterations of high-sensitivity C-reactive protein (hsCRP) and fibrinogen levels in healthy subjects after five weeks of low intensity resistance training (LIRT) with blood flow restriction (BFR) on increasing strength in comparison with high intensity resistance training (HIRT) and LIRT alone, and to evaluate aspects related to the relative safety of LIRT + BFR. Eighteen healthy subjects were randomized into 3 groups. The HIRT group: 70% of One-Repetition Maximum (1-RM); LIRT + BFR group: 30% of 1-RM with BFR (a modified 13-cm wide cuff was used); LIRT group: 30% of 1-RM. The peak torque of isokinetic contraction of the left elbow flexor in each subject was measured before and after 5 weeks of resistance exercises to determine any increases in the left biceps brachii muscle strength. Blood markers of homeostasis (fibrinogen) and inflammation (hsCRP) were also measured before and after five weeks of training. Significant increases of strength were demonstrated between the five weeks of resistance exercises in the HIRT group (P = 0.003) and the LIRT + BFR group (P = 0.001). Peak torque of isokinetic contraction of the left flexor elbow joint at 60 degrees per second angular velocity showed that the LIRT + BFR group produced the greatest peak torque increase than the HIRT group. There were no significant changes in the hsCRP levels in all the groups (P > 0.05) after five weeks of intervention. No significant differences of fibrinogen levels were found in the HIRT group (P = 0.500) and the LIRT + BFR group (P = 0.405), but significant decreases were found in the fibrinogen levels in the LIRT group (P = 0.017). The LIRT + BFR increases in the muscle strength were as significant as in HIRT without altering the fibrinogen and hsCRP levels in the healthy subjects. In this study, LIRT + BFR showed increase muscle strength without any vascular problems.