Objective: The aim of this study was to Comparison of the effect of exhaustive resistance exercises with various resistances on local strength of youth muscles. Methodology: This was a semi experimental research with four group design (three experimental groups and one control group). Statistical sample of this research comprised 44 healthy male students with mean age of 16.1 with no history of resistance exercises. After consent and health questionnaire, the subjects were divided into 3 experimental groups (3×11) and one control group (1×11) based on the strength of upper extremity and lower extremity. Then the experimental groups performed chest press and squat press with determined bar for each group (70, 55 and 85% of maximum repetition) until exhaustion for 8 weeks and three exercise sessions per week with 3 minutes of rest time between courses. In 12th, 18th and 24th exercise sessions (after completion of exercise course) local muscle force tests were repeated. Finally, using ANOVA test data were analyzed. Findings: Performing exhaustive resistance exercises with 55, 70 and 85% resistance of a maximum repetition significantly increased the strength of upper and lower extremity muscles(p<0.05). The effect of exhaustive resistance exercises with 55, 70 and 85% resistance of a maximum repetition had a significant difference on strength of upper and lower extremity muscle strengths (p<0.05). Discussion and conclusion: The resistance exercises with average resistance (resistance amounting to 70% of maximum repetition) has the highest effect upon muscle strength of male adolescents compared to other percentages.

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