Graduation Term

Summer 2026

Degree Name

Master of Science (MS)

Department

School of Kinesiology and Recreation

Committee Chair

Kelly Laurson

Committee Member

Michael Torry

Committee Member

Marcel Lopes dos Santos

Abstract

Early-life physical activity is important for building muscular strength, supporting healthy growth and disease prevention, and for establishing physical activity and strength habits that often track into adulthood. Although grip strength asymmetry is a well-documented risk factor in older adults, evidence in children and adolescents is limited and largely based on small, sport-specific samples. PURPOSE: To describe grip and leg extension strength asymmetries in a nationally representative sample of U.S. youth aged 6–15 years using the National Youth Fitness Survey (NNYFS). METHODS: The analysis included 1,214 participants (606 boys, 608 girls) with valid grip or leg extension data. Age, sex, race/ethnicity, handedness, and BMI were collected, and strength percentiles were created. Participants completed three maximal trials of grip and leg extension strength using a handheld dynamometer, and the asymmetry index was calculated as (Max– Min)/Max*100. RESULTS: Among youth aged 6–15 years, 31.9% showed grip strength asymmetry ≥10%, and 45.0% showed leg extension asymmetry ≥10%. Severe asymmetry (≥15%) was more common in the legs than the arms. Children in the lowest strength quartile had the highest prevalence of asymmetry for both grip and leg extension strength (42.2% and 54.1%, respectively). Left-handed children had lower prevalence of grip asymmetry (22.7%) and leg extension asymmetry (37.6%) than right-handed children (33.3% and 46.0%, respectively). In adjusted models, grip asymmetry was predicted by handedness and strength percentile, whereas leg extension asymmetry was also associated with age, race/ethnicity, and weight status. CONCLUSION: Strength asymmetries were common in U.S. youth, particularly in the lower limbs, and predictors differed between grip and leg extension strength. Future work should develop standardized youth lower limb asymmetry protocols, follow children longitudinally, and test whether early identification can guide targeted interventions to support balanced musculoskeletal development.

Access Type

Thesis-Open Access

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