The Influence of Sprint Duration on the Acute Physiological Responses during Sprint Interval Training Sessions

Abstract

The purpose of this study was to examine the acute physiological responses which occur throughout a sprint interval training (SIT) session and a modified SIT session. Assessment of cardiorespiratory and muscle oxygenation responses and performance were compared. Nine male sport students (age 20 ± 0.6 years; height 1.75 ± 0.1 m; body mass 75.9 ± 5.3 kg; mean ± SD) performed a VO2max test and two SIT sessions on separate days. The SIT session consisted of 6 x 30s ‘all out’ cycling sprints interspersed with 4 minutes recovery. The modified SIT session consisted of 6 x 10s ‘all out’ cycling sprints interspersed with 4 minutes recovery. Cardiorespiratory variables, muscle oxygenation (tissue oxygenation index, TOI) and muscle deoxygenation were recorded at the vastus lateralis using near infrared spectroscopy (NIRS) during both sessions. Participants were unable to complete six 30s sprints during the SIT session and so three consecutive sprints performed during SIT and modified SIT were taken forward for analysis. The SIT session elicited a significantly greater cardiorespiratory response in comparison to modified SIT (44.7 ± 5.5 and 34.4 ± 3.7 ml kg-1 min-1, respectively; P < 0.05). Peak power outputs were greater during modified SIT than in SIT (15.7 ± 2.1 and 13 ± 2.9 W.Kg-1, respectively; P < 0.05) and were maintained throughout sprint trials. No significant difference was observed between muscle oxygenation values (TOI) and muscle deoxygenation for SIT and modified SIT (P > 0.05). The reliability of TOI assessed via NIRS was moderate (r = 0.68). These data indicate that modified SIT elicits similar degrees of peripheral stress in comparison to SIT. It can also be suggested that the attainment of high cardiorespiratory responses is not responsible for previously reported improvements in VO2max. Peak power generation may therefore be a more important stimulus for eliciting physiological adaptations. It can be suggested from the present study that SIT and modified SIT predominantly promote peripheral rather than central adaptations. Modified SIT could therefore be an effective alternative to SIT and moderate intensity continuous training.