Effect of different izotonic quadriceps exercise training on muscle strength, muscle thickness and balance in healthy individuals

Objective: Our study was conducted in order to determine and compare the effects of 8 week progressive resistance concentric and eccentric exercise training specially designed for quadriceps muscle on muscle strength, muscle thickness, single leg balance and hop test in the dominant and non-dominant extremities of the same individual. Method: A total of 20 young individuals (40 lower extremities) with a mean age of 21,05±2,01 years were included in the study. The right and left lower extremities of the participants were divided into two groups as Concentric Exercise Group (CEG) (n=20 lower extremity) and Eccentric Exercise Group (EEG) (n=20 lower extremity) by simple random allocation. One of the lower extremity quadriceps muscle of the participants was given concentric exercise training and the other extremity was given eccentric exercise training in two different positions. Moderate progressive exercises were done 3 days a week, through 8-week. Participants' muscle strength (Hand-held dynamometer and 1-RM), muscle thickness (ultrasound imaging), athlete's single leg test (Biodex) and single leg hop test were measured. Measurements were performed one week before and after the 8-week training. Results: There were improvements in muscle strength, muscle thickness, balance and jump performance at the end of 8-week training in both groups. When the mean differences of CEG and EEG were compared with each other, EEG was more effective in increasing vastus intermedius resting muscle thickness than CEG, no other significant differences were found between groups (p>0.05). Conclusion: In our study, we eliminated the differences based on personal characteristics, and the results showed that the effects of concentric and eccentric exercises on muscle strength, muscle thickness, single leg balance and jump were similar but eccentric exercises could be preferred for hypertrophy for vastus intermedius. Keywords: eccentric training, concentric training, muscle strength, hypertrophy, hop test