Hamstring To Quadriceps Timing And Activation Ratios Of High School Athletes During Cutting And Jumping

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This study assessed hamstring and quadriceps timing and hamstring to quadriceps activation ratios (H:Q), and gender differences therein, during jump landings and cutting maneuvers. Subjects included 6 boys (age = 17.1 ± 0.9 years) and 6 girls (age = 15.7 ± 1.2 years). All subjects provided informed and parental consent and the study was approved by the university review board. Subjects performed 2 repetitions each of the drop jump from a height equal to their maximum vertical jump (J) as well as a sprint and cut at a 45 degree angle (C). Electromyographic (EMG) data were collected for the rectus femoris (RF), vastus lateralis (VL), vastus medialis (VM), lateral hamstring (LH), and medial hamstring (MH). Root mean square (RMS) signal processing was used on all EMG data which were analyzed to assess the magnitude and timing of the muscles bursts pre and post landing for the J and C, using the average of 2 trials and normalized to maximal voluntary isometric contraction. The H:Q were calculated from the collective average of the hamstring muscles divided by the collective average of the quadriceps muscles. The timing of the foot contact was synchronized with the EMG system using a switch mat. Data were evaluated using an independent samples t-test to assess differences in muscle timing and H:Q for the pre and post foot contact for the J and C, for all muscles assessed. Significant gender differences were found for the timing of the MH activation (p ≤ 0.05) pre and post contact during the J, with boys demonstrating 24.4% earlier MH activation and a 19.8% longer burst after foot contact. Compared to boys, girls demonstrated 17.2% earlier MH activation during the C (p ≤ 0.05). Significant gender differences were also found in the H:Q activation ratios with boys demonstrating a 56.3% higher H:Q ratio after J landing (p ≤ 0.05). No other significant gender differences in the timing of muscle activation or the H:Q ratios were found. Counter-movement jump height was assessed as a measure of gender difference in training status. Girls demonstrated 73.7% of the jumping ability of the boys. This study confirms the existence of gender differences in the timing and magnitude of activation of MH during movements that are similar to those that cause ACL injuries. Strength and conditioning professionals are encouraged to prescribe hamstring training to their female athletes in an attempt to remediate gender differences in hamstring activation during J landings.