Comparison of isotonic and isokinetic work induced hypertrophy as evaluated by computed tomography

• Main Author: Pearson, David R.
• Other Authors: Costill, David L.
• Format: Others
• Published: 2011
• Subjects: Hypertrophy.
• Online Access: http://cardinalscholar.bsu.edu/handle/handle/179476; http://liblink.bsu.edu/uhtbin/catkey/487144

Six male subjects (26.0+3.1 years), performed an exercise regimen of repeated knee extension exercises in an attempt to induce size and strength changes in the quadriceps muscle (thigh). Their left thigh was trained using an isotonic (IST) lifting protocol and the right thigh was trained using an isokinetic (ISK) device. The total amount of torque produced by each protocol was the same and knee extensions were performed at a common velocity (120 deg/sec). Training was performed 3 days per week for a period of 8 weeks. Data were presented as means (±SD) for pre-and post-training values with a level of significance set at P<0.05.Girth measurements, corrected for subcutaneous fat and expressed as thigh volumes (cc), showed a significant hypertrophy of the IST thigh (3300.67+526.67) after training as compared to that of the IST thigh (3044.13±448.50) before training. No significant difference was found between pre-and post-training ISK thigh volumes. Computed tomography (CT) data were also obtained but could not be statistically analyzed because of technical errors.The mean IST (36.0+0.0) and ISK repetitions (64.54±13.61) necessary to produce equal work bouts (based on total torque produced) were significantly different, resulting in a greater training intensity for the isotonic training.Strength gains as measured isotonically and isokinetically were specific to the training mode. The IST thigh showed a significant strength (Kg) gain when tested on an IST device; the ISK thigh did not. However, the ISK thigh gained significant strength (Kg-m) at all testing velocities (60,180 and 240 deg/sec) while the IST thigh did not.These data would indicate: 1) IST training is superior to ISK training for producing hypertrophy of the thigh; 2) IST training is more intense than ISK training for equal workbouts; and 3) strength gains are specific to training and to the mode of testing.