# The impact of high-intensity interval exercise training on NK-cell function and circulating myokines for breast cancer prevention among women at high risk for breast cancer

PMID: 33555464
Journal: Breast Cancer Research and Treatment
Published: 2021 Feb 8
Authors: Coletta AM, Agha NH, Baker FL, Niemiro GM, Mylabathula PL, Brewster AM, Bevers TB, Fuentes-Mattei E, Basen-Engquist K, Gilchrist SC, Simpson RJ

## Question

Does 12 weeks of HIIT change resting NK-cell function and circulating myokines more than MICT or usual care in postmenopausal women with obesity at heightened breast-cancer risk?

## Summary

In postmenopausal women with overweight or obesity at elevated breast-cancer risk, 12 weeks of supervised treadmill HIIT did not significantly change resting NK-cell function or circulating myokines compared with moderate continuous training or usual care. The parent trial reported high adherence and compliance, and this paper notes HIIT improved fitness more than comparison groups in prior reporting.

## Population

- Postmenopausal women with overweight or obesity at heightened breast-cancer risk.
- Sample size: 33
- Age: Group means 62.6-66.1 years
- Sex: Female
- Fitness level: Low baseline CRF; VO2peak about 18.8-20.8 ml/kg/min by group
- Health status: Overweight or obesity and elevated breast-cancer risk

## Methodology

- Randomized controlled trial secondary biomarker analysis
- 12 weeks
- Cancer Prevention Center supervised treadmill exercise and usual-care control
- Randomized and controlled study design.

## Protocol

- Supervised treadmill HIIT.
- Modality: Treadmill aerobic exercise.
- Work intervals: Four 4-min intervals at 90-100% peak HR.
- Recovery: 3-min active recovery at 50-70% peak HR after each high-intensity interval.
- Sets or repetitions: 4 intervals.
- Intensity: 90-100% peak HR.
- Session duration: 33 min.
- Frequency: 3 sessions/week.
- Program length: 12 weeks.
- Progression: Individualized HR zones based on cardiopulmonary exercise testing; detailed progression reported elsewhere.
- MICT and usual care.
- Modality: Treadmill continuous exercise or education/phone calls.
- Intensity: MICT 60-70% peak HR; usual care no prescribed exercise session.
- Session duration: MICT 41 min.
- Frequency: MICT 3 sessions/week; usual care monthly calls.
- Program length: 12 weeks.
- Progression: MICT used individualized HR zones; usual care received baseline educational material and monthly calls.

## Outcomes

### NK-cell function
Status: no clear change
No significant within- or between-group changes were observed for NK-cell function variables.

Unadjusted and adjusted models p>0.05 for group changes.

### Myokines
Status: no clear change
No significant between-group changes were observed for circulating myokines.

Change from baseline was not significantly different between groups in unadjusted or adjusted models.

### Fitness correlations
Status: mixed
Lower baseline fitness was associated with larger improvements in selected NK-cell function markers in the total sample.

Specific lysis r=-0.43, p=0.02; hemacytotoxicity r=-0.46, p=0.01.

### Feasibility
Status: improved
The parent trial reported high adherence and protocol compliance for exercise groups.

Adherence 90% HIIT and 89% MICT; compliance 100% to both protocols.

## Practical Insights

- A supervised 4 x 4 min treadmill HIIT format can be feasible for a carefully screened older female clinical-prevention population.
- This paper should not be used to claim resting NK-cell or myokine improvements from HIIT.
- For high-risk users, translate the protocol only with screening, heart-rate monitoring, and conservative supervision assumptions.

## Limitations

- Small sample size
- Biomarker-focused secondary analysis
- Blood collection timing after last workout varied
- Only one cell line was used for NK-cell assays
- Detailed eligibility, progression, attrition, and adverse-event data were reported elsewhere rather than in this paper

## Safety And Adherence

- This article did not report adverse events or injuries.
- Exercise sessions were supervised in a cancer prevention center and prescribed using individualized peak-HR zones.
- The parent trial was described as having low attrition, high adherence, and 100% compliance to HIIT and MICT protocols.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/33555464/) (pubmed)
- [DOI](https://doi.org/10.1007/s10549-021-06111-z) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8189992/) (full text)

## Agent Guidance

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