# Safety and Feasibility of Long-Term High-Intensity Interval Training With and Without Peer Support in Cancer Survivors

PMID: 41653429
Journal: Scandinavian journal of medicine & science in sports
Published: 2026 Feb
Authors: Adlard KN, Farley MJ, Boytar AN, Salisbury CE, Bolam KA, Pegg DK, Aitken JF, Chambers SK, Dunn JC, Courneya KS, Jenkins DG, Skinner TL

## Question

Are 12 months of HIIT, with or without peer support, safe and feasible for breast, prostate, and colorectal cancer survivors after a supervised HIIT introduction?

## Summary

In 137 cancer survivors, a 4-week supervised cycling HIIT start followed by 12 months of community gym access was safe by the study's criteria, with no serious adverse events and few minor adverse events. People usually used the prescribed bike mode and completed the intended high-intensity duration, but long-term attendance and intensity targets were hard to maintain, and peer support did not clearly solve that.

## Population

- Breast, prostate, and colorectal cancer survivors not undergoing active cancer therapy
- Sample size: 137
- Age: Adults 18 years or older; mean not prominent in reviewed lines
- Sex: Men and women; majority described as Caucasian female breast cancer survivors
- Fitness level: Cancer survivors entering structured HIIT with supervised onboarding
- Health status: Post-diagnosis cancer survivors not in active therapy

## Methodology

- Randomized controlled feasibility and safety trial with supervised preintervention phase
- 4-week supervised HIIT plus 12-month maintenance phase
- Supervised exercise physiology sessions followed by community gymnasium or adapted home/community settings
- Randomized and controlled study design.

## Protocol

- 4x4 cycling HIIT maintenance.
- Modality: Cycle ergometer/Wattbike.
- Work intervals: 4 minutes at 85-95% HRpeak.
- Recovery: 3 minutes at 50-70% HRpeak.
- Sets or repetitions: 4.
- Intensity: 85-95% HRpeak for intervals.
- Session duration: 38 minutes.
- Frequency: 3 sessions/week prescribed.
- Program length: 4 weeks supervised plus 12 months maintenance.
- Progression: Initial supervised familiarization before community maintenance.
- HIIT-only maintenance.
- Modality: Same cycling HIIT.
- Work intervals: 4 minutes at 85-95% HRpeak.
- Recovery: 3 minutes at 50-70% HRpeak.
- Sets or repetitions: 4.
- Intensity: Same HRpeak prescription.
- Session duration: 38 minutes.
- Frequency: 3 sessions/week prescribed.
- Program length: 12 months maintenance after supervised phase.
- Progression: No peer support.

## Outcomes

### Safety
Status: improved
Long-term HIIT met safety criteria with no serious adverse events and few minor adverse events.

0 SAEs; 7 grade 1/2 AEs, about 0.5%.

### Attendance
Status: worse/safety concern
Attendance criteria were not met during the 12-month maintenance phase.

A priori attendance threshold was not met in either group.

### Intensity
Status: worse/safety concern
Long-term high-intensity zone adherence was below target in both groups.

48% HIIT+PS and 40% HIIT-only achieved prescribed intensity; average HR was 83.4% and 80.7% HRpeak.

### Mode adherence
Status: improved
Participants overwhelmingly used the prescribed cycle ergometer mode.

99.0% of sessions completed on Wattbikes.

### Peer support
Status: mixed
Peer contact frequency was feasible and safe but did not clearly improve overall HIIT feasibility.

0.8 contacts/week, about 40 contacts/participant; no peer-support adverse events.

## Practical Insights

- Safety can be good while long-term adherence still fails on frequency and intensity.
- Track frequency, intensity, duration, and mode separately instead of one adherence score.
- Peer support is not a substitute for feedback, supervision, or intensity calibration.

## Limitations

- Limited demographic and cancer-type diversity.
- COVID-19 disrupted recruitment, delivery, and retention.
- Adverse events were partly self-reported and may be underestimated.
- Peer contact logs were paper-based and incomplete.
- Cycle-based results may not translate to bodyweight HIIT.

## Safety And Adherence

- No serious adverse events were reported.
- Seven grade 1/2 adverse events were reported.
- Postexercise hypotension was the most frequent adverse event.
- Most adverse events occurred during the supervised preintervention phase.
- No adverse events or psychological distress were attributed to peer support.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/41653429/) (pubmed)
- [DOI](https://doi.org/10.1111/sms.70221) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12882783/) (full text)

## Agent Guidance

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