# Cardiorespiratory fitness in breast cancer survivors: a randomised controlled trial of home-based smartphone supported high intensity interval training

PMID: 34389552
Journal: BMJ Supportive & Palliative Care
Published: 2022-03-01
Authors: Ochi E, Tsuji K, Narisawa T, Shimizu Y, Kuchiba A, Suto A, Jimbo K, Takayama S, Ueno T, Sakurai N, Matsuoka Y

## Question

Does the 12-week home-based smartphone-supported habit-B HIIT program improve cardiorespiratory fitness in sedentary early-stage breast cancer survivors compared with control?

## Summary

This single-center randomized trial tested a 12-week home-based, smartphone-supported HIIT program using bodyweight exercise in sedentary Japanese women who had survived early-stage breast cancer. Compared with smartwatch-only usual control, the habit-B program improved peak oxygen uptake and leg press strength, had 86% adherence, and reported no serious grade 3 or higher adverse events. The exact exercise menu and work-rest structure were not included in the article text, but the study is important because it supports feasible, remotely supported HIIT in a clinical survivor population.

## Population

- Sedentary women aged 20-59 years with stage I-IIa breast cancer after completion of initial treatment except hormone therapy.
- Sample size: 50
- Age: 20-59 years
- Sex: Female
- Fitness level: Sedentary; baseline VO2peak about 25 mL/kg/min.
- Health status: Early-stage breast cancer survivors.

## Methodology

- Single-center, 12-week, parallel-group, single-blind randomized controlled trial.
- 12 weeks
- Home-based intervention supported by smartphone app, personalized email, push notifications, and smartwatch monitoring; assessments at the National Cancer Center Hospital in Japan.
- Randomized and controlled study design.

## Protocol

- habit-B home-based smartphone-supported HIIT.
- Modality: Bodyweight exercises at home.
- Intensity: Maximum RPE target 18 +/- 2; monitored with RPE and smartwatch heart rate.
- Frequency: 3 times per week.
- Program length: 12 weeks.
- Progression: Three stages according to baseline VO2peak with incremental increases according to individual strength level.
- Control with smartwatch.
- Modality: No HIIT intervention described; smartwatch provided.
- Program length: 12 weeks.
- Progression: All participants were offered habit-B after the study period.

## Outcomes

### VO2peak
Status: improved
VO2peak changed by +0.9 (1.7) mL/kg/min in habit-B and -0.8 (1.6) in control; between-group difference 1.7 (95% CI 0.7 to 2.7), ES 1.06.

p<0.01

### VO2peak in L/min
Status: improved
VO2peak changed by +0.06 (0.11) L/min in habit-B and -0.03 (0.09) in control; between-group difference 0.10 (95% CI 0.03 to 0.16), ES 0.95.

p<0.01

### Leg press 1RM
Status: improved
Leg press 1RM changed by +13.0 (15.9) kg in habit-B and -0.5 (18.1) kg in control; between-group difference 13.5 kg (95% CI 2.9 to 24.1), ES 0.79.

p=0.01

### Other physical function, activity, and quality of life outcomes
Status: no clear change
No significant intervention effects were found for 6MWT, grip strength, chair stand test, physical activity, body composition, or QOL.

6MWT p=0.93, grip strength p=0.53, chair stand p=0.50; other p values not reported in main text.

### Adherence and serious adverse events
Status: mixed
Adherence was 86% (range 19%-100%), and no serious grade 3 or higher adverse events occurred.

## Practical Insights

- For selected sedentary breast cancer survivors, home-based bodyweight HIIT can improve CRF when supported by app guidance, reminders, HR monitoring, RPE targets, and remote safety channels.
- Three sessions per week over 12 weeks is a clinically plausible dose for remote HIIT in this population.
- RPE-based intensity targets and staged progression are important when exact external workload cannot be prescribed at home.

## Limitations

- Exact work/rest structure and exercise menu were not reported in this article.
- Small single-center trial.
- Findings may not generalize to all breast cancer survivors.
- COVID-19 disrupted and postponed face-to-face outcome measurements.
- No long-term maintenance follow-up reported.

## Safety And Adherence

- No serious grade 3 or higher adverse events occurred.
- Safety was assessed through emails, phone calls, and app input.
- Exercise adherence was monitored by app input and smartwatch heart rate.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/34389552/) (pubmed)
- [DOI](https://doi.org/10.1136/bmjspcare-2021-003141) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8862092/) (full text)

## Agent Guidance

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