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Training-induced changes in muscle architecture and specific tension
1Department of Life Sciences, University of Tokyo, Japan.
Summary
Resistance training increased elbow extensor muscle size and strength but decreased specific tension. Changes in muscle architecture, like increased fascicle angles, may negatively impact force generation.
Area of Science:
- Exercise Physiology
- Muscle Anatomy
- Biomechanics
Background:
- Skeletal muscle adaptations to resistance training are complex, involving changes in size, architecture, and force production.
- Understanding how resistance training alters muscle architecture, such as fascicle angle and muscle volume, is crucial for interpreting changes in muscle strength and specific tension.
Purpose of the Study:
- To investigate the effects of unilateral resistance training on the triceps brachii muscle's size, architecture, and strength.
- To examine the relationship between changes in muscle architecture (volume, cross-sectional area, fascicle angle) and specific tension following resistance training.
Main Methods:
- Ten weeks of unilateral elbow extensor resistance training in five male participants.
- In vivo B-mode ultrasound to measure muscle thickness and fascicle angles; MRI for muscle volume (Vm) and anatomical cross-sectional area (ACSA).
- Isokinetic dynamometry to assess isometric, concentric, and eccentric elbow extension strength at various velocities; calculation of physiological cross-sectional area (PCSA) and specific tension.
Main Results:
- Significant increases in muscle volume, ACSA, PCSA, muscle layer thickness, and fascicle angles were observed post-training.
- Muscle and fascicle lengths remained unchanged.
- Elbow extension strength increased across all velocities, but specific tension decreased, suggesting altered force-generating capacity per unit of muscle cross-sectional area.
Conclusions:
- Resistance training induces substantial increases in muscle size and strength, accompanied by significant alterations in muscle architecture, specifically increased fascicle angles.
- The observed decrease in specific tension, despite strength gains, suggests that architectural adaptations, such as increased fascicle angles resulting from greater muscle volume and PCSA, may have a detrimental effect on the intrinsic force-generating properties of the muscle.