Comparison of physiological and clinical markers for chronic sprint-interval training exercise performed either in the fasted or fed states among healthy adults.

Sprint-interval training (SIT) and intermittent fasting are effective independent methods in achieving clinical health outcomes. However, the impact of both modalities when performed concurrently is unclear. The aim of this study was to compare the effects of 6 weeks of SIT performed in the fasted versus fed state on physiological and clinical health markers in healthy adults. Thirty recreationally-active participants were equally randomised into either the fasted (FAS; 4 males, 11 females) or the fed (FED; 6 males, 9 females) group. For all exercise sessions, FAS participants had to fast ≥10 h prior to exercising while FED participants had to consume food within 3 h to exercise. All participants underwent three sessions of SIT per week for 6 weeks. Each session consists of repeated bouts of 30-s Wingate Anaerobic cycle exercise. Pre- and post-training peak oxygen uptake (VO), isokinetic leg strength, insulin sensitivity, blood pressure and serum lipid levels were assessed. There were no differences in baseline physiological and clinical measures between both groups (all  > 0.05). VO improved by 6.0 ± 8.8% in the FAS group and 5.3 ± 10.6% in the FED group (both  < 0.05), however the difference in improvement between groups was not statistically significant ( > 0.05). A similar pattern of results was seen for knee flexion maximum voluntary contraction at 300°·s. SIT training in either fasted or fed state had no impact on insulin sensitivity (both  > 0.05). There was significant reduction in diastolic blood pressure (8.2 ± 4.2%) and mean arterial pressure (7.0 ± 3.2%) in the FAS group (both  < 0.05) but not FED group (both  > 0.05). VO and leg strength improved with SIT regardless of whether participants trained in the fasted or fed state. Chronic SIT in the fasted state may potentially reduce blood pressure to a greater extent than the same chronic SIT in the fed state.