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Updated: Jan 31, 2026
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In vivo Measurement of Knee Extensor Muscle Function in Mice
Published on: March 4, 2021
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Regional and muscle-specific adaptations in knee extensor hypertrophy using flywheel versus conventional weight-stack
Tommy R Lundberg1, Maria T García-Gutiérrez2,3, Mirko Mandić1
1a Division of Clinical Physiology, Department of Laboratory Medicine, Karolinska Institutet, and Unit of Clinical Physiology, Karolinska University Hospital, Huddinge C1 88 14186 Stockholm, Sweden.
Summary
Flywheel (FW) and weight-stack (WS) resistance exercise yield similar knee extensor muscle growth. FW training is a time-efficient alternative, achieving comparable results with fewer repetitions.
Area of Science:
- Exercise Physiology
- Sports Science
- Biomedical Engineering
Background:
- Resistance exercise (RE) protocols vary significantly in their effects on muscle adaptation.
- Flywheel (FW) and weight-stack (WS) training are common methods, but direct comparisons of their muscle-specific adaptations are limited.
- Understanding these differences is crucial for optimizing training programs.
Purpose of the Study:
- To compare the regional and muscle-specific adaptations of knee extensors between FW and WS resistance exercise.
- To evaluate the efficacy of FW training as a time-efficient alternative to WS training.
Main Methods:
- Sixteen participants (8 men, 8 women) underwent an 8-week training program, performing FW RE on one leg and WS RE on the contralateral leg.
- Training involved knee extensions, with FW at 4x7 repetitions and WS at 4x8-12 repetitions.
- Muscle hypertrophy was assessed via magnetic resonance imaging (MRI) for specific quadriceps muscles (vastus lateralis, medialis, intermedius, rectus femoris) and cross-sectional area.
Main Results:
- No significant differences were observed in muscle hypertrophy between FW and WS training for the quadriceps femoris or its individual muscles (ranging from 5-17% increase).
- Muscle hypertrophy showed a trend towards being greater at the distal compared to the proximal thigh, irrespective of exercise modality.
- Increases in maximal strength (1RM) and peak power were comparable between FW and WS, with men showing greater strength gains than women.
Conclusions:
- Both FW and WS resistance exercise induce comparable muscle-specific hypertrophy of the knee extensors.
- FW training offers a time-efficient paradigm, achieving similar muscular adaptations with a significantly lower repetition volume compared to WS training.
- FW technology presents a viable and efficient option for individuals seeking to maximize muscle adaptations.
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