Volume: 13 Issue: 3 Year: 2016 Factors effecting hamstrings to quadriceps peak torque ratio in volleyball players Ayşegül Yapıcı 1 Abstract The aim of this study was to analyze of hamstring to quadriceps peak torque ratio (H:Q) measured in isokinetic testing with respect to different angular velocities (60, 180, 300°/s), gender, dominant side and mode of contraction (concentric, eccentric) in volleyball players. Twenty male and ten female healthy volleyball players participated in this study. An independent t-test was used to compare the differences between gender. One-way analysis of variance test was conducted to test for differences by effecting factors. There was a statistically significant difference between dominant and non-dominant side in H:Q ratio at 300°/s in males (p<0.05). There was no statistically significant difference between dominant and non-dominant side in H:Q ratio between female and male volleyball players (p>0.05). There was no statistically significant difference between at 60-180-300°/s velocities by H conc :Q conc contractions and at 60°/s by H conc :Q ecc contractions for male and female’s peak torques in dominant side (p>0.05). There was a statistically significant difference between at 60°/s by H conc :Q conc and H conc :Q ecc contractions for male and female’s peak torques in dominant side (p<0.05). There was a statistically significant difference H:Q ratio obtained by concentric contraction between at 60-300°/s and 180-300°/s velocities (p<0.05), whereas there was no statistically significant difference between 60-180°/s in male and female’s peak torques in dominant side (p>0.05). It was found in our study that H:Q ratio increases with increasing angular velocity. The findings of the present study indicated that angular velocity, type of contraction and leg dominance influence isokinetic strength profiles of male and female, consequently, muscular balance that is H:Q at the knee. This implies that isokinetic concentric knee strength plays more role in high intensity contractions and has more effect at high velocities of contraction in maximal performance. Keywords: Hamstring quadriceps strength ratio; angular velocity; gender; dominant side; concentric; eccentric. 1. Introduction Muscle strength is one of the key factors in successful sports performance and is an important indicator of the effectiveness of injury rehabilitation in athletes. One of the most commonly used methods to assess muscle strength balance between antagonist/agonist muscles is isokinetic testing (Holcomb et al., 2007). Isokinetic testing can be used to evaluate quadriceps and hamstrings muscle strength, providing a determination of the magnitude of torque generated, and subsequently, the hamstrings to quadriceps (H:Q) strength ratio (Orchard et al., 1997). H:Q isokinetic strength of agonist to antagonist knee muscles ratio has been used to examine the functional ability, knee joint stability and muscle balance between hamstrings and quadriceps during velocity dependent movements (Orchard et al., 1997; Aagaard et al., 1995). It has been found that athletes with a concentric H:Q ratio closer to 1.0 may have a reduced risk of hamstrings strain 1 Assistant Professor, Ph.D., Pamukkale University, Faculty of Sport Sciences, ayapici@msn.com