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Neuromuscular adaptations to isoload versus isokinetic eccentric resistance training
Gaël Guilhem1, Christophe Cornu, Nicola A Maffiuletti
1University of Nantes, Laboratory Motricité, Interactions, Performance Nantes, France. gael.guilhem@insep.fr
Medicine and Science in Sports and Exercise
|August 21, 2012
Summary
Isoload (IL) eccentric resistance training was more effective than isokinetic (IK) training for enhancing quadriceps strength and muscle structure. This suggests IL may be superior for optimizing resistance training and rehabilitation outcomes.
Area of Science:
- Exercise Physiology
- Biomechanics
- Sports Science
Background:
- Eccentric resistance training is crucial for muscle adaptation.
- Isoload (IL) and isokinetic (IK) training are distinct modalities for eccentric exercise.
- Understanding the differential effects of IL and IK training is important for optimizing exercise protocols.
Purpose of the Study:
- To compare the neuromuscular adaptations induced by work-matched isoload (IL) versus isokinetic (IK) eccentric resistance training.
- To determine the relative efficacy of IL and IK training on muscle strength, architecture, and neural activation.
Main Methods:
- 31 healthy subjects participated in a 9-week training program (IL, IK, or control).
- Training involved 20 sessions of 3-5 sets of 8 repetitions, with work and mean angular velocity matched between IL and IK groups.
- Neuromuscular assessments included quadriceps strength, muscle architecture (vastus lateralis), EMG activity, and antagonist coactivation, measured pre- and post-training.
Main Results:
- Isoload (IL) eccentric training significantly enhanced eccentric strength at short muscle lengths (+20%) and high velocities (+15%).
- IL training also increased muscle thickness (+10%) and fascicle angle (+11%) compared to baseline and IK training.
- Agonist EMG activity increased similarly in both IL and IK groups, while antagonist coactivation remained unchanged.
Conclusions:
- Isoload (IL) eccentric resistance training demonstrated superior effectiveness compared to isokinetic (IK) training in improving quadriceps muscle strength and structural adaptations.
- The enhanced adaptations with IL are potentially due to greater torque and angular velocities at short muscle lengths during the initial phase of movement.
- These findings have significant implications for tailoring eccentric exercise protocols in resistance training and rehabilitation settings.
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