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Strength and cross-sectional area of knee extensor muscles in children
H Kanehisa1, S Ikegawa, N Tsunoda
1Faculty of Education, Toyama University, Japan.
Insights
Children and women exhibit lower muscle strength relative to muscle size compared to young adults and men, respectively. This difference increases with faster movement speeds, highlighting developmental and sex-based variations in muscle force production capabilities.
Area of Science:
- Biomechanics
- Human Physiology
- Pediatric Exercise Science
Background:
- Understanding age and gender influences on muscle strength is crucial for assessing physical development and performance.
- Previous research indicates differences in muscle strength between sexes and age groups, but the relationship with muscle size across varying contraction speeds requires further investigation.
Purpose of the Study:
- To investigate the impact of age and gender on isokinetic knee extensor strength relative to muscle size (cross-sectional area and thigh length).
- To determine how muscle strength-to-size ratios vary between children and young adults, and between males and females, across different contraction velocities.
Main Methods:
- Measured isokinetic knee extensor strength and quadriceps femoris anatomical cross-sectional area (CSA) in 60 children (6-9 years) and 71 young adults.
- Utilized B-mode ultrasound for CSA measurement and assessed strength at three constant velocities (1.05, 3.14, 5.24 rad.s-1).
- Calculated strength-to-size ratios (ST.CSA-1.TL-1) and analyzed differences based on age and gender.
Main Results:
- Young adults demonstrated significantly higher strength-to-size ratios than children across all velocities.
- The disparity in strength-to-size ratios between children and adults widened with increasing test velocity.
- Men exhibited higher strength-to-size ratios than women within the same age group, except at the slowest velocity in children.
Conclusions:
- The capacity to generate strength proportional to muscle size is less developed in children compared to young adults, irrespective of gender.
- Adult women show a lower relative strength capacity than adult men.
- These findings suggest that developmental maturation and sex influence the efficiency of muscle force production relative to muscle mass, particularly at higher contraction speeds.
Abstract:
Isokinetic strength and cross-sectional area (CSA) of knee extensor muscles were examined in 60 boys and girls, aged 6-9 years, and in 71 young adult men and women to investigate the influences of age and gender on the strength capabilities in relation to muscle size. A single anatomical CSA of quadriceps femoris at the right mid-thigh was measured by using a B-mode ultrasonic apparatus. Isokinetic strength produced at three kinds of constant velocity, 1.05, 3.14, and 5.24 rad.s-1, was significantly correlated to the product of CSA and thigh length (TL) in separate samples by age and gender. In both genders, however, young adults had significantly higher ratios of strength to CSA.TL (ST.CSA-1.TL-1) than children at all measurement velocities. Relative differences in ST.CSA-1.TL-1 between children and young adults became larger with increasing test velocity. Within the same generation, men had significantly higher ST.CSA-1.TL-1 than women at all measurement velocities except for the ratio in children at 1.05 rad.s-1. These results indicate that the ability to produce strength proportional to muscle size is lower in children than in young adults, regardless of gender, and lower in women than in men within the same generation.