Muscle Strength Differences of Hamstring-to-Quadriceps Ratio in Para-Footballers with Cerebral Palsy

Abstract

The aims of this study were 1) to examine differences in knee flexor and knee extensor muscle strength between lower limbs and 2) to compare the hamstring to quadriceps (H/Q) muscle strength ratio and asymmetries, considering more and less affected legs in para-footballers with cerebral palsy (CP) and unilateral spasticity impairment profile. This cross-sectional design study included nine male para-footballers with CP who participated in this study. Participants performed an isometric knee extension and flexion for 5 seconds, and the force was registered with a load cell. The maximum peak force for the hamstring and quadriceps was registered for the more and less affected leg. The difference between legs, between muscle groups, and the hamstring and quadriceps ratio (H/Q ratio) was calculated. The knee extension of the less affected leg showed significantly greater strength than the more affected leg (p = 0.014, d = 0.63), but there were no differences between knee flexors (p = 0.35, d = 0.13). The H/Q ratio was significantly lower in the less affected leg than in the more affected leg (p = 0.03, d =-0.75). The majority of participants (77%) showed asymmetry in lower limb strength levels by more than 10%. Para-footballers with CP showed asymmetries and strength deficits which could be related to a higher prevalence of injury risk factors. The characteristics of this population should be taken into account, and this type of test should be implemented in order to design appropriate training programs to counteract the neuromuscular consequences of CP and improve physical performance.