Feasibility, validity and reliability of the plank isometric hold as a field-based assessment of torso muscular endurance for children 8-12 years of age.

This project examined the feasibility, validity, and reliability of the plank isometric hold for children 8-12 years of age. 1502 children (52.5% female) performed partial curl-up and/or plank protocols to assess plank feasibility (n = 823, 52.1% girls), validity (n = 641, 54.1% girls) and reliability (n = 111, 47.8% girls). 12% (n = 52/431) of children could not perform a partial curl-up, but virtually all children (n = 1066/1084) could attain a nonzero score for the plank. Plank performance without time limit was influenced by small effects with age (β = 6.86; p < .001, η(2) = 0.03), flexibility (β = 0.79; p < .001, η(2) = 0.03), and medium effects with cardiovascular endurance (β = 1.07; p < .001, η(2) = 0.08), and waist circumference (β = -0.92; p < .001, η(2) = 0.06). Interrater (ICC = 0.62; CI = 0.50, 0.75), intra-rater (ICC = 0.83; CI = 0.73, 0.90) and test-retest (ICC = 0.63; CI = 0.46, 0.75) reliability were acceptable for the plank without time limit. These data suggest the plank without time limit is a feasible, valid and reliable assessment of torso muscular endurance for children 8-12 years of age.