Intra- and Inter-session Reliability of Quadriceps' and Hamstrings' Electromyography During a Standardized Hurdle Jump Test with Single-Leg Landing.

The objective of this study was to develop a standardized test to determine quadriceps and hamstrings muscle activation in a position emulating a non-contact anterior cruciate ligament injury. We assessed the intra- and inter-session reliability of surface electromyography (EMG) of the dominant leg following single-leg landing from a standardized hurdle jump. Eighteen subjects (10 males, 8 females) participated in four repeated sessions. During each session, individuals performed three successful jumps over a hurdle set to 75% of their maximal countermovement jump height and landed on their dominant leg. A jump was only considered successful if the individual could maintain the landing position for longer than two seconds following initial ground contact. In one of the four sessions subjects were tested again following a four-minute rest. The activation of the vastus lateralis (VL), vastus medialis (VM), and biceps femoris (BF), were examined by quantifying the root mean squared (RMS) EMG for two seconds immediately following the initial contact. Data from all three successful jumps were used to generate intraclass correlation coefficients (ICC), which were then used to determine intra and inter-session reliability of surface EMG for each muscle. Intra-session reliability was excellent with ICC values of 0.96, 0.94, and 0.93 for the VL, VM and BF, respectively. Additionally, inter-session ICCs were 0.92 (VL), 0.95 (VM) and 0.94 (BF). The standardized hurdle jump with single-leg landing appeared to be a reliable technique for measuring muscle activation for three muscles that contribute to knee stabilization.