The training effect on the human arm flexor was studied by subjecting 5 healthy males. The training was made by isometric maximum contraction, 3 times (10 seconds/bout) a day, every day except Sunday for 100 days. Ultrasonic photography was employed to estimate the cross-sectional area of the muscle.
The muscle training of 100 days increased the maximum strength by 91.7% and the cross-sectional area of muscle by 23.0%.
The average values of strength per unit cross-sectional area of muscle increased from 6.3 to 10.0 kg/cm2 after 100th day of training at extended position of arm, from 4.7 to 7.5 kg/cm2 at flexed position of arm.
The increase of maximum strength was associated with the increase in cross-sectional area and the increase in strength per unit cross-sectional area.
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Ikai, M., Fukunaga, T. A study on training effect on strength per unit cross-sectional area of muscle by means of ultrasonic measurement. Int. Z. Angew. Physiol. Einschl. Arbeitsphysiol. 28, 173–180 (1970). https://doi.org/10.1007/BF00696025
- Muscle Strength
- Cross Section