A pilot study to assess the feasibility of a remotely monitored high-intensity interval training program prior to allogeneic hematopoietic stem cell transplantation
Question
Can a home-based, mobile-health-supported HIIT program be feasibly and safely implemented before allogeneic hematopoietic stem cell transplantation, and are there preliminary improvements in cardiorespiratory fitness and physical function?
Summary
This single-arm pilot tested whether adults preparing for allogeneic hematopoietic stem cell transplantation could perform a home-based, remotely monitored HIIT program before transplant. Participants were prescribed three 30-minute sessions per week with 1-minute high-intensity and 1-minute low-intensity intervals tracked by Apple Watch. Among participants who engaged with the program, adherence was high, no HIIT-related adverse events were reported, and cardiorespiratory fitness and functional measures improved, but the study was small, non-randomized, and had substantial missing wearable data.
Methodology
- Adults scheduled for allogeneic hematopoietic stem cell transplantation for malignant or non-malignant hematologic disorders
- 13 participants.
- Self-selected aerobic activity such as walking, jogging, stair climbing, or cycling.
- Work intervals: 1 minute at 80-90% HRR.
- Recovery: 1 minute at 50-60% HRR.
- Intensity: HRR-based, individualized from CPET maximum HR and resting HR; HR captured by Apple Watch.
- 30 minutes.
- 3 sessions/week, non-consecutive when possible.
- Variable pre-HCT period; mean 13.8 +/- 7.5 weeks among adherent participants.
- Single-arm pilot feasibility intervention study
- Feasibility and adherence, VO2peak, Physical function, and Adverse events were tracked.
Outcomes
Retention and session adherence
Nine of 13 participants (69.2%) consistently reported sessions and remained engaged; among these, median session adherence was 100% and average weekly sessions were 3.1 +/- 0.8.
Median adherence 100% (IQR 87-107); entire sample prescribed-session adherence 73 +/- 53%.
Interval/intensity adherence
Adherent participants averaged 9.2 of 10 prescribed intervals and met or exceeded high-intensity HR on most intervals, but low-intensity recovery targets were less consistently achieved and HR data were missing for 27.5% of reported sessions.
Completed intervals 9.2 +/- 2.3/session; high intervals >=80% HRR on 68.8 +/- 34.8% of intervals; high intervals 80-90% HRR on 25.5 +/- 17.8% and >90% HRR on 43.3 +/- 30.4%; low intervals at 50-60% HRR on 33.0 +/- 15.7%; HR data retrieved from 72.5% of reported sessions.
VO2peak
VO2peak increased from baseline to sign-off among participants with post CPET data.
14.6 +/- 3.1 to 17.9 +/- 3.3 mL/kg/min; p<0.001. In adherent participants: 14.9 +/- 3.3 to 18.0 +/- 3.6; p=0.002.
Physical function
Among adherent participants, 30-second sit-to-stand and SPPB chair-stand performance improved; 6MWT improvement exceeded a clinically meaningful threshold used in other populations.
30-second sit-to-stand 13.8 +/- 1.5 to 18.3 +/- 3.3 repetitions; 6MWT 514.4 +/- 43.2 to 564.6 +/- 19.3 m; table/discussion report clinically meaningful 50.1 m mean improvement.
Safety
No HIIT-related adverse events were reported.
One high resting HR episode related to atrial fibrillation was cleared by physician; other missed sessions were attributed to cancer/treatment effects rather than HIIT.
Insights
- Remote HIIT can be made measurable by tracking interval count, high-zone attainment, recovery-zone attainment, and data retrieval, not just attendance.
- A 30-minute session with 10 minutes of hard work may be feasible for selected, medically cleared clinical users when individualized by HRR and supported by coaching.
- Non-participation is a major issue even when adherent users do well; onboarding, fatigue management, and fallback lower-intensity options are important.
- Wearable HR data quality is an operational dependency for remote HIIT fidelity.
Limitations
- Single-arm non-randomized pilot with no comparator.
- Small sample size and trial stopped before planned enrollment because of COVID-19 and funding timeline.
- Only 9 of 13 participants provided analyzable intervention adherence data.
- HR data were missing for 27.5% of reported sessions.
- Intervention length varied according to clinical transplant timing.
- Mostly male sample, limiting generalizability to female patients.
- Prior exercise experience and outside activity were not measured.
- Three enrolled participants did not ultimately undergo HCT due to relapse.
Safety
- No adverse events related to HIIT were reported.
- One participant had abnormally high resting HR related to atrial fibrillation during one week and continued exercising after physician clearance.
- Cancer/treatment-related missed-session causes included chemotherapy fatigue, hospital admission, pain, and blood clot.
- Clinical users required CPET and cardiology clearance before participation.