Despite the promising evidence supporting positive effects of high-intensity interval training (HIIT) on the metabolic profile in adults, there is limited research targeting adolescents. Given the rising burden of chronic disease, it is essential to implement strategies to improve the cardiometabolic health in adolescence, as this is a key stage in the development of healthy lifestyle behaviours. This narrative review summarises evidence of the relative efficacy of HIIT regarding the metabolic health of adolescents. Methodological inconsistencies confound our ability to draw conclusions; however, there is meaningful evidence supporting HIIT as a potentially efficacious exercise modality for use in the adolescent cohort. Future research must examine the effects of various HIIT protocols to determine the optimum strategy to deliver cardiometabolic health benefits. Researchers should explicitly show between-group differences for HIIT intervention and steady-state exercise or control groups, as the magnitude of difference between HIIT and other exercise modalities is of key interest to public health. There is scope for research to examine the palatability of HIIT as an exercise modality for adolescents through investigating perceived enjoyment during and after HIIT, and consequent long-term exercise adherence.
Have you ever played a game of tag? Children and adolescents may only “play”, but if you don’t consider that high-intensity interval training then I don’t know what is. Funnily, when you consider the natural “play” of children it is anything but repetitive endurance work. Tag, hide-and-seek, and other games are all stop-and-go at various intensities. Even as we age through adolescence, most sports are interval-based. In this light, the tremendous benefits of HIIT on all health parameters of adults isn’t really surprising, it is simply us getting back to what we are meant to do.
Anyways, on to the review at hand, the topic of adolescence fitness and activity is crucial in today’s world where the majority of youth are inactive, and early development of cardiometabolic risk factors in youth have been associated with increased risk of premature death. Furthermore, although it is not known if this is a natural decline or not, average physical activity of adolescents decreases by 60% on average from age ten to 18. This review sought to summarize the central characteristics of HIIT intervention trials on adolescents, with a focus on metabolic health.
Overall, 11 studies were included in the review, with improvements in aerobic fitness, insulin sensitivity, adiponectin and HDL, and reductions in BMI, percentage body fat, SBP, waist circumference, fasting plasma glucose and insulin, LDL and TAG being common themes throughout the studies. HIIT was also shown to be much more effective than steady-state exercise after a much shorter time, and more importantly it was shown to be much more enjoyable. This last part is critical, as adherence is a determining factor in any fitness or nutrition program. Its official, kids would rather do sprints at 90% their VO2 max than go on a 30-minute jog and this is true of both normal-weight and overweight/obese children.
It’s apparent that any fitness professional working with youth should prioritize HIIT, even if just a game of tag. The kids enjoy it and it is effective at improving health. More importantly, the enjoyment of the experience may be an important piece in promoting lifetime exercise adherence. For those of you who like things more structured, however, the most effective protocols included 4-6 sets of 30-60 second sprints followed by 30 seconds of rest or 1-3 minutes of active recovery.