The study examined the sensitivity to change of field assessments of handgrip strength and vertical jump following programmatic interventions in physical education settings. Using a naturalistic experimental design, classes of 6th grade students (N = 158) were randomized to receive either an 8-week musculoskeletal strength or plyometric power program in physical education. Two-way repeated measures (program*time) ANOVAs were used to examine pre-post changes in handgrip and vertical jump tests. Results of the two-way ANOVA examining changes in vertical jump scores revealed a statistically significant program*time interaction effect (p < 0.001) with larger gains in the plyometric power group. The parallel analysis on handgrip was not statistically significant, but percent changes in handgrip scores were larger in the musculoskeletal strength group. The results are consistent with the specificity principle and demonstrate that field-based musculoskeletal fitness assessments are sensitive to change if students receive appropriately designed musculoskeletal programming in physical education classes.