The purpose of this study was to examine differences by gender and grade in middle school students’ physical activity and
fitness (PAF) knowledge, physical activity, and sedentary behavior (SB). The study took place at one middle school located in the
Southeastern region of the United States. Boys (n = 136) and girls (n = 166) in 6th (n = 129),
7th (n = 96) and 8th (n = 77) completed a PE Metrics written test to assess PAF knowledge.
They (N = 312) also completed the validated Youth Activity Profile to report physical activity at school (PAS), physical activity
at home (PAH), and SB. Two-way (gender by grade) multivariate analysis of variances (MANOVA) followed by Bonferroni post-hoc multiple comparison
analysis were conducted. Box’s M test of covariance matrices showed no statistical violation (M = 37.78, F = .73,
p > .05). The two-way MANOVA showed significant gender (Wilks’s λ = .94, F = 4.40, p < .01, 𝜂(2/p)= .06) and grade main
effects (Wilks’s λ = .89, F = 4.20, p < .01, 𝜂(2/p) = .05) Subsequent tests of between subjects effect located the
significant gender difference in PAS favoring boys (F = 9.3, p < .01, 𝜂(2/p) = .03). Boys and girls
showed no significant difference on PAF knowledge, PAH, and SB. Significant grade differences were observed for PAS (F = 8.57, p < .01,
𝜂(2/p) =.06), PAH (F = 8.18, p < .01, 𝜂(2/p) =.05), and
SB (F = 4.61, p = .01, 𝜂(2/p) = .03). Sixth grade students showed significantly higher levels of PAS
and PAH than 7th and 8th grade students (p < .05 or < .01). Sixth grade students further showed significantly
lower SB than 7th grade students (p < .05). This study found boys to be more physically active during school hours
than girls, and students in lower grades to be more active than higher grade students. Future school-based interventions should take into account gender
and grade-based differences.