March 16, 2021

Hashim Islam, PhD, Postdoctoral Fellow

School of Health and Exercise Sciences, UBC Okanagan

Background

• Low CRF is an independent predictor of cardiovascular disease risk and all-cause mortality
• Traditional sprint interval training (SIT: repeated bouts of “all-out” exercise interspersed with short recovery periods) is an exercise protocol that improves CRF in a time-efficient manner
• A potentially even more appealing, time-efficient, and practical approach to SIT involves performing isolated sprints several hours apart over the course of the day
• Whether this approach – termed “sprint exercise snacks” – is sufficient to improve CRF in sedentary adults when performed regularly over several weeks is unclear

How the study was done

• Healthy inactive males and females (~22 years of age) were randomly assigned to two groups: 1) traditional SIT (9 males, 7 females) or 2) exercise snacks (5 males, 7 females)
• Participants in the traditional SIT group performed three repeated 20-second bouts of “all-out” exercise separated by 3-min recovery periods during a single exercise session, whereas those in the exercise snack group performed three isolated 20-second bouts of “all-out” exercise 1-4 hours apart.
• Both groups exercised 3 days a week (typically on Monday, Wednesday and Friday) on a stationary bike for a 6-week period. All exercise was performed in a university lab setting.
• CRF (determined using expired gas measurements during an incremental cycling test to exhaustion), cycling time-trial performance (time required to complete a set amount of work as quickly as possible), and perceived enjoyment were recorded before and after the 6-week period

What the researchers found

• After 6-weeks, participants improved CRF (~4-6% increase) and cycling time-trial performance (~2-3 min faster) regardless of group.
• Perceived enjoyment over time increased only in the traditional SIT group. This may be due to the inconvenience of exercising in lab three times a day in the exercise snacks group

Conclusion 

• Sprint exercise snacks may be an effective strategy for improving CRF and exercise performance in sedentary young adults
• Future research should examine the effectiveness and feasibility of sprint exercise snacks performed in a “real-world” setting (e.g. home, office) to extend the laboratory-based observations of this study.

Take home message

• Isolated bouts of brief intense exercise over the course of the day – known as “sprint exercise snacks” – can improve cardiorespiratory fitness (CRF) in sedentary young adults
• The improvement in CRF following sprint exercise snacks can be similar to that observed after popular interval exercise protocols such as sprint interval training
• Sprint exercise snacks can be incorporated into activities of daily living, thereby alleviating the need for planning and allocating time for structured physical activity.