# High-intensity interval training combining rowing and cycling improves but does not restore beta-cell function in type 2 diabetes

PMID: 38513367
Journal: Endocrine connections
Published: 2024 May 1
Authors: Houborg Petersen M, Stidsen JV, Eisemann de Almeida M, Kleis Wentorf E, Jensen K, Ørtenblad N, Højlund K

## Question

Can 8 weeks of supervised HIIT combining upper- and lower-body exercise restore beta-cell function in men with type 2 diabetes compared with obese and lean glucose-tolerant controls?

## Summary

In sedentary middle-aged men with type 2 diabetes and glucose-tolerant obese or lean controls, 8 weeks of supervised HIIT combining rowing and cycling improved insulin sensitivity in all groups. Beta-cell function adjusted for insulin sensitivity improved substantially but variably in type 2 diabetes, yet remained markedly impaired compared with controls.

## Population

- Sedentary middle-aged men with type 2 diabetes, obese glucose-tolerant controls, and lean glucose-tolerant controls
- Sample size: 48
- Age: 40-65 years
- Sex: Men only
- Fitness level: Sedentary
- Health status: 15 obese men with type 2 diabetes, 15 obese glucose-tolerant men, and 18 lean glucose-tolerant men included before dropouts

## Methodology

- Prespecified secondary analysis of a controlled training study with pre-post within-group comparisons
- 8 weeks
- Supervised laboratory/clinical exercise and metabolic testing
- Controlled study design.

## Protocol

- Rowing and cycling HIIT.
- Modality: Alternating rowing and cycling ergometer intervals.
- Work intervals: 1 min high-intensity interval.
- Recovery: 1 min active or passive recovery between intervals; 4 min break between blocks.
- Sets or repetitions: Blocks of 5 x 1 min intervals; progressed from 2 to 5 blocks/session.
- Intensity: >=85% HRmax during intervals.
- Session duration: 10 min warm-up plus 2-5 training blocks and 4 min breaks.
- Frequency: 3 sessions/week.
- Program length: 8 weeks.
- Progression: 2 blocks in weeks 1-2, then one extra block every second week, ending with 5 blocks in weeks 7-8; one session replaced by midway VO2max test for workload adjustment.
- Group comparisons.
- Modality: All groups performed the same HIIT; comparisons were type 2 diabetes vs obese controls vs lean controls.
- Work intervals: Same intervention.
- Recovery: Same intervention.
- Sets or repetitions: Same intervention.
- Intensity: Same intervention.
- Session duration: Same intervention.
- Frequency: Same intervention.
- Program length: Same intervention.
- Progression: Same intervention.

## Outcomes

### Insulin sensitivity
Status: improved
HIIT increased insulin sensitivity in all groups.

All groups p < 0.01

### Disposition index
Status: improved
Disposition index improved substantially but variably in type 2 diabetes and modestly in controls.

Type 2 diabetes >200% improvement, p < 0.05; controls about 20-30%, p < 0.05

### Beta-cell restoration
Status: no clear change
Despite improvement, disposition index remained markedly lower in type 2 diabetes than controls.

Post-HIIT type 2 diabetes DI remained lower than controls, all p < 0.001

### Second-phase insulin
Status: worse/safety concern
Second-phase insulin responses were reduced after HIIT in all groups.

All groups p < 0.05; authors interpret in context of improved insulin sensitivity

### Adherence
Status: improved
Attendance and achieved interval intensity were high, with no injuries reported.

Attendance >95% in all groups; average HRmax above 85% during intervals; no participants sustained injuries

## Practical Insights

- Combining rowing and cycling can recruit upper and lower body muscle groups in HIIT.
- HIIT can improve insulin sensitivity, but beta-cell dysfunction in established type 2 diabetes may not normalize.
- Clinical metabolic testing occurred about 60 h after the last HIIT session to reduce acute exercise confounding.

## Limitations

- Men only
- No non-exercise randomized control arm in this analysis
- Clinical laboratory protocol with rowing/cycling ergometers
- Secondary analysis
- Beta-cell outcomes require specialized clamp/IVGTT methods

## Safety And Adherence

- No participants sustained injuries; four participants dropped out during the project, including one lean man before training due to a new knee injury and three for lack of time.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/38513367/) (pubmed)
- [DOI](https://doi.org/10.1530/EC-23-0558) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC11046351/) (full text)

## Agent Guidance

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