# Effects of High-Intensity Interval Training Protocols on Liver Enzymes and Wellness in Women

PMID: 34007845
Journal: Journal of sports medicine (Hindawi Publishing Corporation)
Published: 2021
Authors: Rengers TA, Orr SC, Marks CRC, Hew-Butler T, Choi MD, Butcher SJ, Drignei D, Brown EC

## Question

Do rowing HIIT and multimodal resistance-based HIIT differ in effects on liver enzymes, cardiometabolic risk factors, and psychosocial outcomes in healthy young women without obesity?

## Summary

Sixteen recreationally active women without obesity completed 12 weeks of group HIIT using either rowing or a multimodal resistance/conditioning format. Rowing HIIT reduced ALT and AST more than multimodal HIIT, whole-group perceived wellness improved, and other cardiometabolic markers did not clearly change.

## Population

- Recreationally active females without obesity who were not in a regular training program.
- Sample size: 16
- Age: 23.0 +/- 5.9 years
- Sex: Women only
- Fitness level: Recreationally active, 1-3 h/week activity, not systematic endurance or weight training
- Health status: BMI <30 kg/m2; exercise-limiting illness/injury and medication affecting exercise responses excluded

## Methodology

- Parallel-group randomized trial comparing two supervised HIIT modalities
- 12 weeks
- University recreation center group exercise setting
- Randomized and controlled study design.

## Protocol

- Rowing or multimodal HIIT.
- Modality: Rowing ergometer or heavy resistance/conditioning circuit.
- Work intervals: 60 seconds maximum-intensity work.
- Recovery: 3 minutes rest.
- Sets or repetitions: 6 sets.
- Intensity: >90% age-estimated maximum heart rate; mean achieved 90.8% R-HIIT and 89.6% MM-HIIT.
- Session duration: 60 minutes including warm-up/instruction and cool-down.
- Frequency: 3 sessions/week.
- Program length: 12 weeks.
- Progression: Eight workouts rotated; intensity/speed increased on repeat workouts; rowing group aimed for more meters each bout.
- Active HIIT modality comparator.
- Modality: The alternate HIIT modality: rowing versus multimodal resistance/conditioning.
- Work intervals: 60 seconds.
- Recovery: 3 minutes.
- Sets or repetitions: 6 sets.
- Intensity: >90% age-estimated maximum heart rate.
- Session duration: 60 minutes including warm-up/instruction and cool-down.
- Frequency: 3 sessions/week.
- Program length: 12 weeks.
- Progression: Progressed by speed, intensity, or meters rowed.

## Outcomes

### ALT
Status: improved
R-HIIT had significantly lower postintervention ALT than MM-HIIT after adjustment; paired tests showed ALT decreased in R-HIIT.

Mean difference 13.16, p=0.013, partial eta squared=0.44, 95% CI 3.40 to 22.92.

### AST
Status: improved
R-HIIT had significantly lower postintervention AST than MM-HIIT after adjustment.

Mean difference 10.79, p=0.024, partial eta squared=0.38, 95% CI 1.67 to 19.90.

### Wellness
Status: improved
Perceived wellness improved for the whole group, with a significant within-group increase in MM-HIIT, but no between-group difference.

Whole group 14.72 +/- 2.6 to 16.89 +/- 2.76, p=0.002.

### Other cardiometabolic markers
Status: no clear change
Resting heart rate, blood pressure, glucose, lipids, BMI, waist circumference, and waist-to-height ratio showed no significant changes.

No significant changes reported.

## Practical Insights

- In this small sample, rowing HIIT was more favorable than multimodal resistance HIIT for liver enzymes.
- Group HIIT with modeling and encouragement may support perceived wellness.
- Heavy multimodal HIIT needs coaching and equipment.

## Limitations

- Small sample
- No no-exercise control group
- Unblinded assessors
- Healthy baseline values reduced room for cardiometabolic improvement
- Groups were not energy-expenditure matched

## Safety And Adherence

- Two participants dropped out from R-HIIT; one due to an unexpected commitment and one due to a concussion outside the study.
- No intervention-related adverse events were reported.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/34007845/) (pubmed)
- [DOI](https://doi.org/10.1155/2021/5554597) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8110421/) (full text)

## Agent Guidance

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