# Sprint interval training decreases left-ventricular glucose uptake compared to moderate-intensity continuous training in subjects with type 2 diabetes or prediabetes

PMID: 28874821
Journal: Scientific reports
Published: 2017 Sep 5
Authors: Heiskanen MA, Sjöros TJ, Heinonen IHA, Löyttyniemi E, Koivumäki M, Motiani KK, Eskelinen JJ, Virtanen KA, Knuuti J, Hannukainen JC, Kalliokoski KK

## Question

Are two weeks of sprint interval training more effective than moderate-intensity continuous training for improving left- and right-ventricular glucose and fatty-acid metabolism, cardiac structure, and function in adults with type 2 diabetes or prediabetes?

## Summary

This small randomized trial compared two weeks of supervised all-out sprint interval training with moderate continuous cycling in adults with type 2 diabetes or prediabetes. Sprint training improved VO2peak, while both training styles improved whole-body insulin-stimulated glucose uptake and some hemodynamic measures. Contrary to the authors' hypothesis, sprint training decreased left-ventricular insulin-stimulated glucose uptake compared with moderate training, raising uncertainty about whether very intense all-out intervals are metabolically ideal for the diabetic heart. The study was short, small, and focused on cardiac imaging endpoints rather than consumer-facing performance outcomes.

## Population

- Untrained adults aged 40-55 with type 2 diabetes or prediabetes.
- Sample size: 26
- Age: 40-55 years eligible
- Sex: Men and women; exact distribution not extracted
- Fitness level: Untrained, VO2peak below 40 mL/kg/min
- Health status: 17 participants with T2DM and 9 with prediabetes; HbA1c less than 7.5

## Methodology

- Parallel-group randomized controlled trial.
- 2 weeks
- Supervised laboratory training and imaging at Turku PET Centre, Finland.
- Randomized and controlled study design.

## Protocol

- Sprint interval training.
- Modality: Cycle ergometer.
- Work intervals: 30 seconds all-out.
- Recovery: 4 minutes.
- Sets or repetitions: 4-6 bouts.
- Intensity: All-out with load equal to 10% fat-free mass after 5-second acceleration.
- Session duration: Not explicitly stated; interval/recovery structure implies roughly 14-23 min excluding unreported warmup/cooldown.
- Frequency: 6 sessions in 2 weeks.
- Program length: 2 weeks.
- Progression: 4 bouts initially, then 5, then 6 after every other session.
- Moderate-intensity continuous training.
- Modality: Cycle ergometer.
- Work intervals: Continuous cycling.
- Sets or repetitions: One continuous bout.
- Intensity: 60% peak workload.
- Session duration: 40-60 min.
- Frequency: 6 sessions in 2 weeks.
- Program length: 2 weeks.
- Progression: Duration increased from 40 to 50 to 60 min after every other session.

## Outcomes

### Left-ventricular glucose uptake
Status: worse/safety concern
SIT decreased insulin-stimulated LV glucose uptake compared with MICT.

Reported as significant group difference; exact p value not extracted.

### VO2peak
Status: improved
Only SIT significantly improved VO2peak.

Group*time p=0.0495; SIT time effect p=0.013.

### Whole-body insulin-stimulated glucose uptake
Status: improved
Both SIT and MICT improved whole-body insulin-stimulated glucose uptake.

p=0.001 time effect.

### Free-fatty-acid uptake
Status: no clear change
Fasted fatty-acid uptake in both ventricles remained unchanged by training.

### Completion/tolerability
Status: mixed
Most participants completed, but one SIT participant discontinued due to migraine during the first SIT session.

SIT completers 11/13; MICT completers 10/13.

## Practical Insights

- All-out 30-second SIT can improve VO2peak quickly, but in diabetes/prediabetes it may not be uniformly better than moderate training.
- For users with type 2 diabetes or cardiac risk, prescribed-intensity HIIT may be a safer default than maximal all-out sprinting.
- Long recoveries and low total hard-work time are not enough to remove the need for screening in clinical populations.

## Limitations

- Small sample size.
- Only two weeks of training.
- Cardiac metabolic endpoints do not directly translate to symptoms or long-term outcomes.
- Medication use during scans/trial could not be fully controlled.
- Longer studies are needed to determine whether decreased glucose uptake after SIT is acute or persistent.

## Safety And Adherence

- One SIT participant dropped out due to migraine during the first SIT session.
- Candidates were screened by medical examination, ECG, and OGTT.
- The study raises caution about diabetic cardiac substrate metabolism after all-out SIT.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/28874821/) (pubmed)
- [DOI](https://doi.org/10.1038/s41598-017-10931-9) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5585392/) (full text)

## Agent Guidance

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