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Increase in Volitional Muscle Activation from Childhood to Adulthood: A Systematic Review and Meta-analysis
Stacey Woods, Caragh O'Mahoney1, James Maynard1
1Department of Kinesiology, Brock University, St. Catharines, ON, CANADA.
Medicine and Science in Sports and Exercise
|December 30, 2021
Summary
Children exhibit lower volitional muscle activation (VA) than adults, impacting maximal strength. This review confirms that children activate their motor-unit pool less, with differences varying by muscle group.
Area of Science:
- Pediatric Exercise Science
- Neuromuscular Physiology
- Human Performance
Background:
- Children's maximal muscle strength is lower than adults', even when normalized for body size.
- Lower volitional muscle activation (VA) in children is a proposed reason for age-related differences in muscular performance.
- Recent studies present conflicting findings on age-related increases in VA.
Purpose of the Study:
- To systematically review and determine the effect of age on volitional muscle activation (VA) during maximal isometric contractions.
- To synthesize existing literature comparing VA in children and adults.
Main Methods:
- Systematic review of literature examining VA differences using twitch interpolation in children (7-14 yr) and adults (16-28 yr).
- Inclusion of 19 datasets for qualitative analysis and 14 for quantitative meta-analysis (207 children, 193 adults).
Main Results:
- Significantly lower VA in children was reported in 47% of studies.
- Meta-analysis revealed a strong effect of age on VA, with children showing lower VA than adults (Hedges' g = 1.55).
- Muscle group was a significant moderator; publication bias may be present.
Conclusions:
- Children activate their motor-unit pool less compared to adults.
- The increase in VA with age may be influenced by the specific muscle group (upper vs. lower extremity).
- Further research is needed to understand the developmental mechanisms and upper body muscle influences on children's VA.
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