# Six Weeks of Low-Volume Sprint Interval Training Improves Peak Oxygen Uptake Compared to a Non-Exercise Control: A Randomized Controlled Trial

PMID: 40879181
Journal: Scandinavian Journal of Medicine and Science in Sports
Published: 2025-09
Authors: Renwick JRM, Crukley J, Kudsi M, Binet ER, Bone J, Mulkewich NJ, Babir FJ, Gurd BJ, Gibala MJ

## Question

Does 6 weeks of low-volume sprint interval training improve peak oxygen uptake compared with a non-exercise control in insufficiently active young adults?

## Summary

In insufficiently active young adults, 6 weeks of supervised very-low-volume sprint interval cycling on a CAROL Bike improved VO2peak and cycling time-to-exhaustion versus a non-exercise control. The protocol was time-efficient but required specialized cycling equipment and all-out supramaximal efforts.

## Population

- Apparently healthy insufficiently active young adults.
- Sample size: 37
- Age: 18-35 years; mean 22.2 +/- 2.5
- Sex: 13 male, 24 female
- Fitness level: Insufficiently active; baseline VO2peak 33 +/- 7 ml/kg/min.
- Health status: Apparently healthy and cleared by questionnaire.

## Methodology

- Single-centre randomized controlled trial with allocation concealment, outcome assessor blinding, and Bayesian analysis.
- 6 weeks
- McMaster University Human Performance Laboratory.
- Randomized and controlled study design.

## Protocol

- Low-volume sprint interval cycling.
- Modality: CAROL Bike sprint cycling.
- Work intervals: 20 s.
- Recovery: 2 min.
- Sets or repetitions: 3 sprints/session; first session 1 x 10 s plus 2 x 20 s.
- Intensity: All-out; about 190% Wmax mean sprint power.
- Session duration: 10 min.
- Frequency: 3 sessions/week.
- Program length: 6 weeks.
- Progression: Individualized resistance adjusted by bike algorithm.
- Non-exercise control.
- Modality: No prescribed exercise.
- Program length: 6 weeks.

## Outcomes

### Relative VO2peak
Status: improved
LVSIT increased relative VO2peak compared with control.

Group difference +5.6 ml/kg/min, 95% CrI 2.2 to 8.1.

### Absolute VO2peak
Status: improved
Absolute VO2peak increased compared with control.

Group difference +325 ml/min, 95% CrI 101 to 605.

### Time to exhaustion
Status: improved
Cycling time-to-exhaustion improved substantially in LVSIT.

Group difference +133 s, 95% CrI 101 to 160.

### Responder rate
Status: improved
Most LVSIT participants achieved meaningful VO2peak gains while controls rarely did.

>=1 MET: 76% LVSIT vs 0% control; relative VO2peak responders 94% vs 20%.

## Practical Insights

- Bike sprint intervals can be extremely time efficient but are equipment-specific.
- First-session downshifting is a useful safety/onboarding pattern for all-out work.
- Do not conflate supramaximal bike sprint evidence with general no-equipment HIIT.

## Limitations

- Short 6-week intervention
- Young healthy insufficiently active sample
- Specialized bike required
- Habitual physical activity and diet not strictly controlled
- Possible conflict of interest

## Safety And Adherence

- No specific adverse-event data were found in extracted sections.
- Participants were screened and supervised.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/40879181/) (pubmed)
- [DOI](https://doi.org/10.1111/sms.70130) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12395895/) (full text)

## Agent Guidance

Preserve the paper-level scope of this note. Do not generalize beyond the population, protocol, measured outcomes, and limitations above.