Semitendinosus and biceps femoris long head activity during the single leg bridge test in healthy individuals

Introduction: The single leg bridge test (SLBT) has been suggested as a clinical test to examine function, screen injury risk, and monitor the effectiveness of rehabilitation programes targeting the hamstring. This study aimed to determine the inter-day reliability and repeatability of both SLBT performance, semitendinosus (ST), and biceps femoris long head (BFlh) surface electromyography (sEMG) responses and characterise the BFlh and ST electrical activity during the SLBT performed until exhaustion in healthy individuals. Methods: Twelve physically active young men without previous hamstring injury were tested for the number of repetitions attained, and sEMG signal median frequency and amplitude in both ST and BFlh of each lower limb, randomly in two sessions, with a seven-day interval between sessions. Results: High reliability [ICC = 0.85] was found for the number of SLBT repetitions attained. Reliability of sEMG outcomes showed better results for ST (ICC = 0.62–0.91) than for BFlh (ICC = 0.39–0.81), and a high to very-high repeatability was found for both ST (ICC = 0.91–0.84) and BFlh (ICC = 0.91–0.85). sEMG median frequency decreased and amplitude increased for both BFlh (p ≤ 0.001) and ST (p ≤ 0.039) at the end of SLBT, suggesting localised fatigue. Conclusions: The SLBT performed by healthy individuals until exhaustion proved to be reliable and to induce fatigue in both BFlh and ST, where the sEMG median frequency and amplitude can be measured on different days with acceptable reliability and high repeatability, suggesting its potential future use in both practical and clinical settings.