Low-Active Male Adolescents: A Dose Response to High-Intensity Interval Training

Greig Robert Melrose Logan; Nigel Harris; Scott Duncan; Lindsay D. Plank; Fabrice Merien; Grant Schofield

Disclosures

Med Sci Sports Exerc. 2016;48(3):481-490. 

In This Article

Abstract and Introduction

Abstract

Purpose: High-intensity interval training (HIIT) is a potential alternative to traditionally recommended steady state exercise for providing health benefits in adolescents, yet its dose–response relationship in this cohort remains unclear, as does its translatability to real-world, nonclinical settings. The present study adopts a novel dose–response design to investigate the effects of undertaking 8 wk of HIIT on the cardiometabolic health of low-active male adolescents.

Methods: Twenty-six male adolescents (age 16 ± 1 yr), identified as low active by nonparticipation in structured sport and physical education classes, were randomly assigned to one of five treatment groups. Corresponding with their group numbers (1–5), participants completed a number of HIIT "sets," which consisted of 4 repeated bouts of 20-s near-maximal exertion interspersed with 10-s passive recovery. Participants performed two HIIT sessions and one resistance training session each week for 8 wk. Baseline and follow-up health measures consisted of peak oxygen uptake (V̇O2peak) with an incremental ramp test to volitional exhaustion; body composition (including visceral fat mass, body fat, and lean tissue mass) with dual-energy x-ray absorptiometry; and lipid profile, glucose, insulin, and interleukin-6 from blood analysis. All health outcomes were analyzed as percentage changes, and data were modeled using a quadratic function to explore dose-response relationships.

Results: Significant improvements were observed for V̇O2peak (~6%), body fat percentage (~4%), visceral fat mass (~10%), and waist circumference-to-height ratio (~3%), but there was no clear effect of dose across groups.

Conclusions: Low-active adolescent males performing a single HIIT set twice weekly, in addition to one resistance training session, gained meaningful improvements in fitness and body composition. Performing additional HIIT sets provided no additional improvements to those of the lowest dose in this study.

Introduction

The development of healthy lifestyle behaviors, including physical activity, typically begin in childhood and continue into adulthood.[1,37] Preventing the decline of physical activity throughout youth is of key importance in reducing the development of risk factors, which lead to chronic cardiometabolic diseases such as type 2 diabetes, metabolic syndrome, cardiovascular disease, and obesity.[32,40] Public health guidelines suggest that children and adolescents undertake at least 60 min of moderate-to-vigorous intensity activity (MVPA) each day to achieve health benefits;[31] however, more than 80% of adolescents globally fail to achieve this recommended threshold of activity.[22] Given that adolescents report difficulty starting and adhering to traditional exercise programs,[17] there is a need to explore and develop engaging alternatives for youth to achieve the many health benefits related to regular physical activity.

Recent research has indicated that short bouts (<7 min) of vigorous intensity activity may drive the inverse association between physical activity and cardiometabolic risk factors.[14,24] Therefore, higher intensity activities performed in short repeated bouts, interspersed with periods of recovery, may be an achievable and enjoyable alternative to high-volume continuous exercise for adolescents.[28] Adopted as a time-efficient method of achieving the health benefits of physical activity, high-intensity interval training (HIIT) has become a popular alternative to the traditionally recommended steady-state aerobic exercise.[20] The majority of HIIT research has been conducted using adults, but it is widely accepted as an exercise model effective in improving aerobic fitness, body composition, insulin sensitivity, blood lipid profile, blood pressure, and cardiovascular function.[2,12,26] However, research studying the efficacy of HIIT on the health-related outcomes of adolescence has been limited, although initial studies indicate similar or superior health benefits using HIIT when compared with continuous aerobic exercise.[16,28]

Conventionally, HIIT research has been performed in laboratory settings, but to fully investigate its efficacy as an alternative to currently recommended exercise, it should also be considered in a real-world setting. Recently, Buchan et al.[9] reported the efficacy of HIIT on the health and fitness of healthy Scottish adolescents when performed in school physical education (PE) classes. Although it is of interest to understand the feasibility and efficacy of HIIT during PE, it important to understand the effects of HIIT on the health of low-active youth who are disengaged from PE, structured sports, and extracurricular physical activity. Our research adopts the approach of using a nonclinical, school-based setting for inactive adolescents to undertake HIIT outside of PE class.

In view of the uncertainty of the quantity of HIIT needed to improve inactive adolescents' cardiometabolic health, our research attempts to establish a dose–response relationship for the first time. To investigate the efficacy of different treatments, the conventional approach is to conduct a repeated-measures crossover study, whereby each study participant receives all treatments or doses. This study design is impractical when considering many health outcomes, as exercise interventions produce long-lasting effects, thus preventing subjects from receiving more than one treatment.[4] In the current study we have addressed this issue by adopting the novel dose–response design reported by Stepto et al.[35] and Barnes et al..[4] Using this study design, participants receive only one treatment, and individual responses are plotted with the overall dose–response effect represented as a quadratic function.

To our knowledge, no study has yet investigated the dose response of HIIT on the health of adolescents, hence the purpose of this study was to investigate the efficacy of incremental doses of HIIT, in combination with a standardized resistance training protocol, on inactive adolescents' health-related outcomes after an 8-wk school-based exercise intervention. We hypothesize that increasing the dose of HIIT, through the addition of exercise sets (or intervals), will elicit a greater benefit in several key health outcomes in low-active male adolescents.

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