Isokinetic Versus Isotonic Resistance Training: Defining the Mechanisms of Hypertrophy and Exercise Execution Methods

Date of Award

Spring 2-26-2024

Document Type


Degree Name

Doctor of Kinesiology (EdD)



First Advisor

Brian Serrano

Second Advisor

Eder Garavito

Third Advisor

Stephanie Hamilton



Purpose: To determine strength changes and hypertrophy differences at the biceps brachii between an isokinetic bicep curl machine created by C&M Machines and preacher curl exercise with a standard curl bar. The study also aimed to determine the effectiveness of the aforementioned machine and to give insight into this unique method of training.

Methods: A medical clearance form and a Physical Activity Readiness Questionnaire was implemented to evaluate ability to exercise. 10 subjects (n=10) were recruited, were 20.3 years old (20 +/- 2), and were cleared for rigorous exercise. Subjects were randomly assigned to a control group (CG) or experimental group (EX). Subjects completed a 10-week training program consisting of 2 training sessions per week with a minimum of 48 hours between sessions, CG completing 5 sets of 5 reps at 80% 1RM on seated preacher curls, EX completing 5 sets of 5 at 80% estimated max force on the isokinetic machine. Pre and post assessments consisted of biceps brachii circumference measurements.

Results: After 10 weeks of training at the given prescription, the experimental group improved in bicep brachii circumference 3.8 cm (+/- .9cm) and the control group improved 1.6 cm (+/- 1.5cm). These results suggest that the isokinetic curl machine is more effective for promoting muscle hypertrophy than the standard, isotonic preacher curl. Both exercises were considered effective in modest bicep brachii growth (Isotonic t-value (-2.359), Isokinetic t-value (-3.559)), and both groups had a statistically significant improvement (Isotonic p-value (.039), Isokinetic p-value (.012)) (p<.05).

Discussion: These methods of weight training gave a direct comparison between standard resistance training and isokinetic resistance training. With this comparative study, the physiologic factors of weight training can be better understood on which method may be better for muscle development, which method may be more effective for hypertrophy and if there is notable change with the given prescription. The described machine controls time under tension, measures force production consistently and gives continual feedback on subject effort. The increases in hypertrophy were likely due to these factors.

Keywords: Hypertrophy, resistance training, isokinetic, isotonic, kinesiology, time under tension

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