Date of Award

1-1-2011

Document Type

Campus Access Thesis

Department

Exercise Science

First Advisor

Matthew C Kostek

Abstract

It is yet to be established when equating for total work performed that isotonic compared to isokinetic eccentric contractions elicits a differential response in regards to surrogate markers of skeletal muscle damage. Purpose: To directly compare between isotonic- and isokinetic-type eccentric contractions for differences in markers of muscle damage. Methods: 24 men were placed into a control (C), isotonic (IT) or isokinetic (IK) group. The IT (110% of maximal isometric torque) and IK (120°/sec) groups performed 200 eccentric contractions of each knee extensor and had serial measurements taken for strength, perceived muscular soreness and creatine kinase activity up to 48-h post exercise. Results: Total work (~1,700 J) and peak torque (~ 265 Nm) significantly decreased over the 200 repetitions (p < 0.01), but was not different between the groups. All surrogate markers of muscle damage were significantly changed 48-h post exercise (p < 0.05): peak isometric torque (-13%), creatine kinase activity (+200%) and self-perceived muscular soreness (+5 unit change), however, significant group × interactions (p < 0.001) indicated that peak isometric torque, plasma creatine kinase activity and self-perceived muscular soreness exhibited a differential response between the two protocols 48-hours post exercise. Conclusion: The current protocol suggests that when equating for total work during distinct modes of muscular contractions that differential outcomes are evident in markers of skeletal muscle damage. These data have implications for appropriateness of protocols to promote muscle damage, exploration of neuromuscular mechanisms associated with distinct contractions types and integration of biomechanical, neurological and physiological parameters to elucidate mechanisms to provide evidence in explaining the observed findings.

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