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Comparison of concentric vs eccentric contractions to measure exercise induced fatigue
Stenfert Kroese, Sebastian K. Firor, Kaiya M. Corman, Anna C. Feldman, William J. Silverman, Anne K. Knaus, Katie R.
Stenfert Kroese, Sebastian K.
Firor, Kaiya M.
Corman, Anna C.
Feldman, William J.
Silverman, Anne K.
Knaus, Katie R.
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2025-04
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Abstract
Muscular fatigue – a decrease in muscle strength induced by exercise – of the plantarflexors (ankle muscles) is common in various populations, such as the elderly, and may have implications on the biomechanics of functional movements. To investigate these implications, we must quantify fatigue of the plantarflexors to understand if fatigue is induced, how quickly it is induced, and measure recovery time. Our goal was to determine if concentric (muscle shortening) or eccentric (muscle lengthening) isokinetic (constant muscle velocity) contractions are more effective at fatiguing the plantarflexors. Effectiveness was measured by (1) the number of isokinetic sets to reach 75% initial maximum voluntary isometric (constant muscle length) contraction (MVIC) and (2) duration of post-fatigue-recovery to reach 95% initial MVIC. Using an instrumented dynamometer to quantify ankle joint torque, participants followed a fatiguing protocol. First, an MVIC set the participant's maximum torque. In between each MVIC, the participant underwent fatiguing, consisting of sets of 80 eccentric or concentric contractions. Each participant completed eccentric and concentric tests for the right and left legs on separate days. The participants were considered fatigued when their current MVIC was reduced to 75% of their initial MVIC. After fatigue was reached, MVICs were measured every 90 seconds to track post-fatigue recovery. Results show that there is no notable difference between eccentric and concentric fatigue and recovery. Both modes showed the ability to fatigue to 75% initial MVIC and had similar recovery rates. Eccentric fatigue, however, is uncomfortable and unnatural. Therefore, concentric contractions are the suggested fatiguing mechanism to help determine the effects of fatigue on the biomechanics of functional movements in future work.
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