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), intrarater (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.