Acute physiological and perceptual responses in the FIT FIRST FOR ALL school-based physical activity program.

This study examined acute physiological and perceptual responses to the FIT FIRST FOR ALL program, a structured school-based physical activity intervention designed to promote engagement. In a non-randomized cluster study conducted in the Faroe Islands, 179 pupils aged 7-16 participated in three weekly 40-minute sessions for 10 weeks as part of a school-wide program alongside physical education. Acute responses were assessed in a subsample (n = 53) using heart rate, accelerations, perceived exertion, and enjoyment, with individualized thresholds and stratification based on baseline cardiorespiratory fitness assessed using a shuttle run test. Sessions consistently elicited moderate-to-vigorous intensity, with mean heart rate ranging from 67.2 ± 1.3 to 69.9 ± 1.4% of maximal heart rate. Pupils spent 57.9 ± 3.6 to 64.9 ± 3.3% of session time at moderate-to-vigorous intensity, including up to 31.8 ± 3.0% at vigorous intensity. Despite higher physiological and perceived exertion among pupils in the low fitness group, enjoyment was comparable across fitness groups. Cardiorespiratory fitness improved among the intervention sample (n = 117), with a tendency for greater gains in the lowest fitness tertile, although differences were not statistically significant (p = 0.063, ε² = 0.024). These findings suggest that FIT FIRST FOR ALL can elicit health-promoting intensity and high enjoyment across age and fitness groups when delivered school-wide through teacher-led sessions.