# A Comparison of the Gluco-Regulatory Responses to High-Intensity Interval Exercise and Resistance Exercise

PMID: 33401694
Journal: International Journal of Environmental Research and Public Health
Published: 2021
Authors: Gordon BA, Taylor CJ, Church JE, Cousins SD

## Question

Do acute gluco-regulatory and hormonal responses differ between duration-matched high-intensity interval cycling and resistance exercise?

## Summary

In healthy recreationally active adults, one fasted cycling HIIT session caused a larger short-term glucose, cortisol, heart-rate, and lactate response than a duration-matched lower-body resistance session, while insulin and perceived exertion were similar.

## Population

- Healthy recreationally active adults accustomed to both high-intensity interval and resistance exercise
- Sample size: 16
- Age: 22 +/- 7 years
- Sex: 8 male, 8 female
- Fitness level: Regularly performed both high-intensity interval and resistance exercise at least twice weekly
- Health status: Apparently healthy; no recent injuries

## Methodology

- Randomized cross-over trial
- Single acute exercise exposure per condition with at least 7 days washout
- Laboratory exercise testing in the morning after an overnight fast
- Randomized and controlled study design.

## Protocol

- High-intensity interval exercise.
- Modality: Cycle ergometer.
- Work intervals: 30 seconds at 80% predicted peak power.
- Recovery: 90 seconds very light active recovery.
- Sets or repetitions: 12 intervals.
- Intensity: 80% predicted peak power; mean 84 +/- 7.4% HRmax.
- Session duration: 24-minute interval block.
- Frequency: Single session.
- Program length: Acute study.
- Progression: No progression; fixed acute protocol.
- Resistance exercise.
- Modality: Squat, calf raise, and incline leg press.
- Work intervals: 4 sets of 10 repetitions at 80% predicted 1RM for each exercise.
- Recovery: 90 seconds between sets.
- Sets or repetitions: 4 x 10 for three lower-body exercises.
- Intensity: 80% predicted 1RM; mean 71 +/- 7.5% HRmax.
- Session duration: Duration matched to HIE.
- Frequency: Single session.
- Program length: Acute study.
- Progression: No progression.

## Outcomes

### Glucose
Status: mixed
Glucose was higher after cycling HIIT than resistance exercise during early recovery.

Condition x time interaction p=0.026, eta squared=0.23; mean glucose 0.7 mmol/L higher with HIE; higher immediately, 30 minutes, and 90 minutes.

### Insulin
Status: no clear change
Insulin responses did not differ between exercise modes.

No significant condition difference, p=0.275.

### Cortisol
Status: mixed
Cortisol was higher after cycling HIIT than resistance exercise.

Mean cortisol 71 ng/mL higher with HIE, 95% CI 16 to 126, p=0.015; higher from 30 to 120 minutes.

### Heart rate
Status: mixed
HIIT produced a higher heart-rate response than resistance exercise, while RPE was similar.

%HRmax 84 +/- 7.4 for HIE vs 71 +/- 7.5 for RE, p<0.001; RPE 16 +/- 2.8 vs 16 +/- 1.3, p=0.605.

## Practical Insights

- Acute fasted cycling HIIT can produce larger glucose and cortisol perturbations than lower-body resistance exercise.
- Similar RPE does not imply similar cardiometabolic stress across modalities.
- Fasted high-intensity work may provoke nausea or presyncope in some participants.

## Limitations

- Acute study only.
- Young healthy active sample.
- Fasted laboratory condition may not reflect typical training.
- Diet was replicated but not tightly controlled.
- Oxygen consumption was not measured during the trials.
- Menstrual phase was not controlled.

## Safety And Adherence

- Several participants experienced nausea or presyncope in both fasted exercise conditions; one participant stopped HIE after 8 of 12 intervals.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/33401694/) (pubmed)
- [DOI](https://doi.org/10.3390/ijerph18010287) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7795282/) (full text)

## Agent Guidance

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