Knee strength balance ratios are not affected by aging among male runners

OBJECTIVES: This study aimed to assess thigh muscular strength, conventional and functional strength balance ratios, and muscle quality in well-trained male runners aged 20-70 yr. METHODS: Eighty-nine male runners were divided into five age categories: 20-29, 30-39, 40-49, 50-59, and 60-70 yr. Participants underwent an isokinetic strength test for knee flexor and extensor muscles and a body composition analysis via dual-energy X-ray absorptiometry. RESULTS: No significant difference was observed in concentric peak torque of the knee extensor muscles between the 20-29 and 40-49 age groups. However, the 50-59 age group showed significantly lower strength than the 20-29 age group (p = 0.049), and the 60-70 age group demonstrated significantly lower strength than the 40-49 group (p < 0.001). The conventional and functional balance ratios remain stable across all age groups. CONCLUSION: Knee flexor and extensor strength in male runners decreases significantly after the age of 50, while conventional and functional strength balance ratios remain stable.