Correspondences between continuous and intermittent exercises intensities in healthy prepubescent children

The aim of this article is to determine correspondences between three levels of continuous and intermittent exercise (CE and IE, respectively) in terms of steady-state oxygen uptake \( (\dot{V}{\text{O}}_{{ 2\,{\text{SS}}}} ) \) and heart rate (HR) in children. Fourteen healthy children performed seven exercises on a treadmill: one graded test for the determination of maximal aerobic speed (MAS), three CE at 60, 70 and 80% of MAS (CE60, CE70 and CE80) and three IE (alternating 15 s of exercise intercepted with 15 s of passive recovery) at 90, 100 and 110% of MAS (IE90, IE100 and IE110). Mean \( \dot{V}{\text{O}}_{{ 2\,{\text{SS}}}} \) and mean HR were determined for both continuous and intermittent exercises. For comparison, three associations were designed: CE60 versus IE90, CE70 versus IE100 and CE80 versus IE110. No \( \dot{V}{\text{O}}_{{ 2\,{\text{SS}}}} \) difference was observed for CE60 versus IE90 and CE70 versus IE100 whereas a significant difference (P < 0.01) was found for CE80 versus IE110 (1.36 ± 0.45 vs. 1.19 ± 0.38 L min⁻¹, respectively). Significant linear regressions were found for the three CE versus IE associations for \( \dot{V}{\text{O}}_{{ 2\,{\text{SS}}}} \) (0.60 < r ² < 0.99, P < 0.05). For the three associations, mean HR presented no significant difference. Only one significant relation was found for CE80 versus IE110 association (r² = 0.49, P < 0.05). Correspondences between CE and IE intensities are possible in terms of \( \dot{V}{\text{O}}_{{ 2\,{\text{SS}}}} \) whatever the level of exercise; even if for high intensities, \( \dot{V}{\text{O}}_{{ 2\,{\text{SS}}}} \) was higher during CE. These results demonstrated that it is possible to diversify the exercise modality while conserving exercise individualization.