Longitudinal Assessment Of Handgrip Isometric Strength During Childhood

Muscle strength, as measured by grip strength (GS), is considered a key component of physical fitness and one of the powerful markers of health in children and adolescents. However, there are limited longitudinal studies assessing grip strength during childhood. PURPOSE: To examine the development of GS during early and middle childhood and its association with height, weight, and body fat (BF). METHODS: First and 2nd grade children (28 boys and 33 girls) were evaluated yearly until their 6th grade of elementary school (age: 6.4 ± 0.5 to 11.4 ± 0.5 y). Right- and left-hand grip strength was determined with an adjustable hand dynamometer. Weight, height, and estimated body fat (BF) (from triceps and calf skinfolds) were measured. A general linear model multivariate analysis with Bonferroni post-hoc was used to determine differences by grade and sex, and Pearson correlations to evaluate associations between variables. RESULTS: Total grip strength (sum of right and left hand) increased yearly from 1st to 6th grade: 21.2 ± 4.9, 26.4 ± 5.2, 29.7 ± 5.0, 33.1 ± 5.8, 37.3 ± 7.1, 41.3 ± 7.7 kg respectively (P < 0.04). Total GS increased 20.1 kg at a rate of 1.6 kg/y in boys, and 1.7 kg/y in girls. Height and weight increased from 1st to 6th grade (P < 0.01), while BF increased from 1st to 4th and 5th grade (P < .03). No sex differences were found in total GS, height, and weight in any grade. Boys had higher left-hand GS than girls only in 2nd grade, and BF was higher in girls compared with boys in all grades (P < 0.05 for all). Moderate to strong direct associations were found between GS and height (r = 0.41 to 0.63; P < 0.001) and weight (r = 0.36 to 0.58; P < 0.02) in all grades. A significant direct association between total GS and BF was only found in 4th and 5th grade (r = .29; P < 0.03). CONCLUSIONS: The results of this longitudinal study suggest that GS increases with height and weight from 1st to 6th grade and is not influenced by sex. The direct association between GS and BF in 4th and 5th grade needs to be further evaluated.