Isometric muscle strength assessment and hamstring:quadriceps ratio between men trained with free weights vs. machines

Abstract

Introduction: Strength exercises (EF) are effective to enhance strength, power, endurance and muscle hypertrophy. However, there are controversies about the prescription of a PE program with free weights (PL) or machines (MQ) to minimize the risk of injuries and improve physical performance. Objective: The purposes of this study were to assess the isometric muscle strength of the knee extensors and flexors, bilateral asymmetry (BA) and hamstring:quadriceps ratio (H:Q ratio) between dominant leg (DL) vs. non-dominant leg (NDL) of males trained with free-weights vs. machines. Methods: Thirty males were recruited and separated into two groups: Free-weights (n=15) and Machines (n=15) groups. All study participants underwent body composition assessments and then performed the isometric muscle strength (IMS) testing for knee extensors and flexors in the DL and NDL using a commercially available load cell. The highest value obtained from the three trials was used for statistical analysis. No clinical problems occurred during the study. Results: The IMS of quadriceps and hamstring muscles for DL and NDL showed a significant increase to Free-weight group when compared to Machine group. In addition, was observed a significant difference (p<.03) of the IMS of hamstring muscles between DL vs. NDL to machine group. The H:Q ratio on DL (p<.002) and NDL (p<.01) was significantly higher to Free-weight group. Conclusion: This study showed better isometric muscle strength of thigh (hamstring and quadriceps) and H:Q ratio in males trained with Free-weight. In addition, males trained with machines showed bilateral asymmetry of the hamstrings muscles and lower H:Q ratio, consequently, higher risk of knee injuries.