Lower-limb asymmetry in healthy male athletes

[Purpose] This study aimed to determine lower extremity asymmetry in healthy males when participating in sports where non-contact injuries are common by comparing lower extremity muscle strength, jumping distance, and change of direction speed between the dominant and non-dominant legs. [Participants and Methods] Study participants included 16 healthy males who had been playing a specific sport for at least four years at the time of measurement. We measured the maximal isometric strength of five muscle groups and conducted six performance tests. The lower-limb symmetry index was calculated as follows: (non-dominant leg/dominant leg) × 100. [Results] Significant differences were found in the strength levels of hip flexors, hip abductors, knee flexors, and knee extensor muscles. The lower-limb symmetry index for all muscles, except for the hip flexors, ranged from 91% to 98%. In the performance tests, significant differences were found in the crossover hop test and the 90° change of direction test. The lower-limb symmetry index ranged from 96% to 103% in all the performance tests. [Conclusion] We suggest that leg dominance be considered in assessments for determining return to sports based on the type of tests employed.