Angle-specific Hamstrings To Quadriceps Ratios: Effects Of Hip Joint Angle And Type Of Muscle Action

BACKGROUND: Hamstrings-to-quadriceps (HQ) ratio is used to assess strength balance of the knee joint for performance enhancement and injury prevention. However, HQ ratio assessment requires an isokinetic dynamometer and is commonly calculated from the peak knee extension and flexion torques attained at different knee angles (conventional HQ ratio). PURPOSE: Τo examine the effect of hip joint angle and type of muscle action on hamstring-to-quadriceps ratios (HQ) across a wide range of motion of the knee joint. METHODS: Twelve healthy athletes performed three maximal concentric flexion-extension efforts on an isokinetic dynamometer at 60 0 s-1 and two isometric efforts in six different knee angles (100, 300, 500, 700, 900, 1100) in the prone (neutral hip angle) and seated positions (900 hip angle), on two different experimental sessions. Conventional HQ ratios were calculated from peak flexion and extension torque values. Also, angle-specific HQ ratios were calculated from flexion and extension torques at each knee angle and were compared between positions (prone and seated) and types of muscle action (isometric vs. isokinetic) using 2-way ANOVA. RESULTS: In the seated position, conventional HQ ratios were similar in isokinetic and isometric measurements (55 ± 8% and 51 ± 10%, p = 0.297). In the prone position, these ratios were significantly lower (p < 0.001), but still similar in isometric and isokinetic measurements (35 ± 6 and 33 ± 6%, p = 0.453). Angle-specific HQ ratios at the knee angles from 700 to 1100 were low and similar, irrespective of the type of muscle action and hip angle (range: 27 ± 19 to 32 ± 8%, p > 0.195). However, HQ ratios increased progressively and were different between the seated and prone positions from the knee angle of 500 (seated: 61 ± 14% vs. prone: 35 ± 7%, p < 0.001) to 100 (seated: 372 ± 163%, vs. prone: 63 ± 22%, p < 0.001). CONCLUSIONS: Conventional HQ ratios are lower in the prone position due to a reduction in muscle length of the hamstrings and an increase in muscle length of rectus femoris. Angle-specific HQ ratios escalate with decreasing knee angle, and this effect is amplified in the seated position. These findings have implications for strength testing in healthy and injured individuals and suggest that HQ imbalances should be evaluated in an angle-specific manner, taking into account hip angle.