Introduction and Purpose: The effect of concurrent training on the quadriceps and hamstring muscles, particularly through aerobic activities such as walking and running backward, has been less studied. This study aimed to examine the impact of concurrent training on the thickness, strength, and strength ratio of the quadriceps and hamstring muscles in middle-aged men.
Materials and Methods: This semi-experimental study included 48 men aged 50 to 65 years, who were randomly divided into four training groups: (1) strength-aerobic with forward walking, (2) strength-aerobic with backward walking, (3) resistance, and (4) control. The training was performed over eight weeks, with three sessions per week. Assessments of body composition, balance, thickness, strength, and the quadriceps-to-hamstring strength ratio were conducted before and after the training period. The data were analyzed using repeated-measures ANOVA, with a significance level set at P≤0.05.
Results: No significant differences were observed between the exercise groups in weight, body mass index, quadriceps thickness, hamstring strength, and balance (p˃0.05). Fat-free mass and hamstring muscle thickness increased significantly in the exercise groups compared to the control group (p≤0.05). The increase in quadriceps strength was significant only in the resistance training group (p≤0.05). The ratio of quadriceps strength to hamstring strength decreased significantly in the strength–aerobic training groups and increased significantly in the resistance training group (p≤0.05).
Conclusion: Concurrent training, with an emphasis on aerobic activities (walking and running backward), improves body composition, increases hamstring thickness, corrects the quadriceps-to-hamstring strength ratio, enhances muscular balance and motor performance, and reduces the risk of injury in middle-aged men.