Muscular fitness profiles in relation to the response in body fat during school-based high-intensity intervention.

Abstract

We aimed to assess the equivalence of the muscular fitness (MF) between body fat percentage (BFP) responders (Rs<inf>BFP</inf>) and non-responders (NRs<inf>BFP</inf>) to school-based high-intensity interval training (HIIT). Adolescents aged 16 (N.=73, 42.5% of males) were identified as Rs<inf>BFP</inf> (N.=45) or NRs<inf>BFP</inf> (N.=28). MF was assessed based on hand strength (HS), abdominal muscle strength (ABS), and leg power (VJ). Profile analysis showed distinct patterns of MF changes in both response categories. Despite the presence of parallelism (Wilks' Λ=0.979, Pillai's V=0.212, P=0.473), a gradient of increasing changes (HS-ABS-VJ) was found in the Rs<inf>BFP</inf>, while a gradient of decreasing changes was shown in the NRs<inf>BFP</inf>, and a significant level of inequality (F<inf>(1,71)</inf>=7.823, P=0.047, partial eta-squared [η2<inf>p</inf>] 0.041). One-way analysis showed a significant and moderate effect on VJ (F<inf>(1,71)</inf>=7.080, P=0.010, η2<inf>P</inf>=0.091), a close to significant effect on ABS (F<inf>(1,71)</inf>=3.300, P=0.074, η2<inf>P</inf>=0.044) and lack of an effect on HS (F<inf>(1,71)</inf>=0.699, P=0.406, η2<inf>P</inf>=0.010). The test of equal means across the condition categories (separately for Rs<inf>BFP</inf> and NRs<inf>BFP</inf>) indicated that there was no multivariate statistically significant within-group effect (F<inf>(2, 70)</inf>=0.517, P=0.599). The findings may help teachers assess the potential and indirect changes in muscle performance after employing a body weight intervention (based on the HIIT program). A more targeted approach to treating adolescents with excessive BF, in parallel with improving MF, can be individually tailored.