• Jonathan P Little, Jodi Langley, Michael Lee, Etienne Myette-Côté, Garett Jackson, Cody Durrer, Martin J Gibala, and Mary E Jung.
• School of Health and Exercise Sciences, University of British Columbia, Okanagan Campus, 1147 Research Road, Kelowna, BC, V1V 1V7, Canada. jonathan.little@ubc.ca.
• Eur. J. Appl. Physiol. 2019 May 1; 119 (5): 1203-1212.

PurposeSprint interval training (SIT), involving brief intermittent bursts of vigorous exercise within a single training session, is a time-efficient way to improve cardiorespiratory fitness (CRF). It is unclear whether performing sprints spread throughout the day with much longer (≥ 1 h) recovery periods can similarly improve CRF, potentially allowing individuals to perform "sprint snacks" throughout the day to gain health benefits.MethodsHealthy, young, inactive adults (~ 22 years, peak oxygen uptake [VO2peak] ~ 35 ml kg- 1 min- 1) were randomly assigned to one of two groups and performed 18 training sessions over 6 wks. Sprint snacks (SS) involved 3 × 20-s 'all out' cycling bouts separated by 1-4-h rest (n = 12, 7 females). Traditional SIT involved 3 × 20-s bouts interspersed with 3-min rest within a 10-min training session (n = 16, 7 females). The primary outcome was CRF determined by a VO2peak test conducted before and after training. Secondary outcomes included a 150 kJ cycling time trial and exercise enjoyment.ResultsAbsolute VO2peak increased by ~ 6% after SIT and ~ 4% for SS (main effect of time P = 0.002) with no difference between groups (group × time interaction, P = 0.52). 150 kJ time trial performance improved by ~ 13% in SIT and ~ 9% in SS (main effect of time, P < 0.001) with no difference between groups (group × time interaction, P = 0.36).ConclusionCRF was similarly increased by a protocol involving sprint snacks spread throughout the day and a traditional SIT protocol in which bouts were separated by short recovery periods within a single training session.

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