# High-intensity interval training for 12 weeks improves cardiovascular autonomic function but not somatosensory nerve function and structure in overweight men with type 2 diabetes

PMID: 35275239
Journal: Diabetologia
Published: 2022-03-11
Authors: Bönhof GJ, Strom A, Apostolopoulou M, Karusheva Y, Sarabhai T, Pesta D, Roden M, Ziegler D

## Question

Does 12 weeks of supervised cycling HIIT improve cardiovascular autonomic and somatosensory nerve function in overweight men with type 2 diabetes compared with normal-glucose-tolerant men?

## Summary

In overweight sedentary men, 12 weeks of supervised cycling HIIT improved aerobic fitness. Men with type 2 diabetes also showed improvements in cardiovascular autonomic measures, but peripheral/somatosensory nerve function and intraepidermal nerve fiber density did not change.

## Population

- Overweight sedentary men with type 2 diabetes and overweight normal-glucose-tolerant men.
- Sample size: 43
- Age: 30-65 years eligible
- Sex: Men only
- Fitness level: Sedentary
- Health status: Overweight; type 2 diabetes or normal glucose tolerance

## Methodology

- Controlled before-after exercise intervention
- 12 weeks
- Fully supervised cycle-ergometer training in a clinical research study
- Controlled study design.

## Protocol

- Supervised 4 x 4 cycling HIIT.
- Modality: Cycle ergometer.
- Work intervals: 4 min.
- Recovery: 3 min.
- Sets or repetitions: 4 intervals.
- Intensity: 90% HRmax work, 70% HRmax recovery.
- Session duration: 35 min.
- Frequency: 3 sessions/week.
- Program length: 12 weeks.
- Progression: No separate progression described.
- Normal-glucose-tolerant comparison group.
- Modality: Cycle ergometer.
- Work intervals: 4 min.
- Recovery: 3 min.
- Sets or repetitions: 4 intervals.
- Intensity: 90% HRmax work, 70% HRmax recovery.
- Session duration: 35 min.
- Frequency: 3 sessions/week.
- Program length: 12 weeks.
- Progression: Same as intervention group.

## Outcomes

### VO2max
Status: improved
VO2max increased in both normal-glucose-tolerant and type 2 diabetes groups.

NGT 25.5 to 29.6 ml/kg/min; T2D 23.1 to 27.0 ml/kg/min.

### Baroreflex
Status: improved
Men with type 2 diabetes improved baroreflex sensitivity indices.

BRS-allSeq 8.82 to 14.6, BRS+ 7.19 to 15.4, and BRS- 12.8 to 14.6 ms2/mmHg; all p<0.05.

### Resting HR
Status: improved
Resting heart rate decreased in both groups.

NGT 65.1 to 60.2 bpm; T2D 68.8 to 63.4 bpm.

### Nerve measures
Status: no clear change
Somatosensory nerve function, clinical neuropathy scores, nerve conduction, QST, and IENFD did not change.

No significant change reported across these nerve outcomes.

### HbA1c
Status: no clear change
HbA1c did not change despite improved insulin sensitivity in type 2 diabetes.

HbA1c unaltered; M value increased in T2D.

## Practical Insights

- A supervised 4 x 4-min cycling format can improve aerobic fitness in overweight men with and without type 2 diabetes.
- Autonomic benefits should not be translated into claims of peripheral nerve repair.
- Clinical users need screening before high-intensity HR-targeted training.

## Limitations

- Moderate sample size
- Men only
- Nonrandomized clinical group comparison
- Most participants did not have impaired peripheral or autonomic nerve function at baseline
- Weight-loss and glycemic-change effects were intentionally limited

## Safety And Adherence

- No explicit adverse-event results were reported.
- Participants underwent extensive medical exclusion screening.
- All sessions were fully supervised.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/35275239/) (pubmed)
- [DOI](https://doi.org/10.1007/s00125-022-05674-w) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9076744/) (full text)

## Agent Guidance

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