Sprint Interval Training: Assessing effectiveness and adherence in a real-world setting

Introduction: Perceived lack of time is an oft-cited reason for not engaging in physical activity. One proposed solution is high-intensity interval training (HIIT), or a more intense version known as sprint interval training (SIT), which involves repeated “all-out” efforts interspersed with short recovery periods. Although convincing evidence demonstrates the efficacy of SIT on cardiorespiratory fitness and other health factors, whether individuals will independently perform and benefit from this type of exercise outside the supervised lab setting is unknown. Purpose: To compare the effectiveness and adherence of performing running SIT and moderate-intensity continuous training (MICT) protocols in a real-world setting. Methods: 20 inactive (<150 min per week) young adults (18-35 y) completed 8-wks of running SIT (6-12 x 15 s “all-out” efforts interspersed with 105 s recovery) or MICT (20-50 min at 55-63% O2max). Pre- and post-experimental measures included: anthropometry, aerobic and anaerobic capacity, as well as psychological perceptions (affect, exercise task self-efficacy, intentions, arousal, and enjoyment). Results: Overall adherence (week 1-8) to both MICT (58.8±26.1% of sessions completed) and SIT (77.5±23.7%) were not different (P=0.855). There were no changes pre- to post-training for any anthropometric measure (P>0.788),O2max (P=0.953), or 30 s running sprint (P>0.086). However, there was a significant positive correlation (r=0.59, p=0.011) that higher adherence lead to greater improvements in O2max. Affect and self-efficacy after the first session were higher for MICT (P<0.040). After the third session both affect and self-efficacy were the same between MICT and SIT (P>0.052). MICT was perceived as more enjoyable than SIT during the first week of training (P<0.045) but there were no further differences. Conclusion: Due to low adherence, both MICT and SIT yield negligible results physiologically when completed independently in a real-world setting. Psychological measures were different but did not seem to alter adherence.