Investigating the Effects of Blood Flow Restriction Exercises on Strength and Cross Section Area of Hamstring Muscles and Tendons: A Case Report

Introduction: Hamstring injuries are one of the most common tendon injuries, especially in sports that require running and jumping. A comprehensive training program can help athletes to prevent this injury. Among suggested exercises, the Nordic eccentric training can reduce the injury rate by up to 50%; however, it is a high-load exercise that cannot be prescribed in the first stages of rehabilitation. Here, we describe a football player who used low-load resistance exercise with blood flow restriction as an alternative method to strengthen their hamstring after nine months of anterior cruciate ligament reconstruction surgery Case Description: A 19-year-old non-professional footballer with a body mass index of 22.18 kg/cm2 was invited to participate in this study. The variables examined included strength and cross-sectional area of the hamstring muscles (mean and maximum strength) and the crosssectional area of the hamstring tendons at their origin. The treatment program included a seated hamstring curl with a load of 30% 1 RM with blood flow restriction for four weeks (thrice a week). Results: The hamstring muscle strength improved by 6.54%, and the cross-sectional area of the muscles and tendons changed as follows: Semimembranosus (tendon=0.07%, muscle=2.57%), semitendinosus (tendon=0.00%, muscle=-4.04%), and biceps-femoris (tendon=5.5%, muscle=4.34%). Conclusion: Low load resistance training with blood flow restriction in this athlete improved the strength and cross-sectional area of the hamstring muscles as well as the cross-sectional area of the tendons. The changes observed in tendon, and muscle cross-sectional areas were more prominent for biceps-femoris. This case showed that a training program with blood flow restriction may be a good alternative for people who cannot tolerate high-load exercises in the early stages of their rehabilitation. Doing more extensive studies with more cases and a control group in the future can help our knowledge in giving the best exercise prescription to our patients.