# Feasibility and acceptability of high-intensity interval training and moderate-intensity continuous training in kidney transplant recipients: the PACE-KD study

PMID: 35597974
Journal: Pilot and feasibility studies
Published: 2022 May 21
Authors: Billany RE, Smith AC, Hutchinson GM, Graham-Brown MPM, Nixon DGD, Bishop NC

## Question

Are two cycling HIIT protocols and a moderate continuous cycling protocol feasible, acceptable, and safe for kidney transplant recipients, and what outcomes might inform a larger trial?

## Summary

In kidney transplant recipients, 24 supervised cycling sessions of either HIIT or moderate continuous training were generally safe and well attended, with no major adverse events reported. The main feasibility problem was intensity: only 40% achieved the required power-output intensity, although 75% met a secondary heart-rate intensity criterion. Participants completed 92% of sessions, reported the programs as enjoyable and beneficial, and VO2peak and peak power tended to improve, but this pilot was not powered to test efficacy.

## Population

- Stable adult kidney transplant recipients.
- Sample size: 24
- Age: 48 +/- 13 years in randomized sample.
- Sex: 16 male (67%).
- Fitness level: Low-to-moderate cardiorespiratory fitness; baseline VO2peak 25.28 +/- 7.48 mL/kg/min.
- Health status: Kidney transplant recipients with eGFR 58 +/- 19 mL/min/1.73 m2 and high cardiovascular medication burden.

## Methodology

- Randomized three-arm pilot and feasibility trial.
- 24 supervised sessions intended over about 8 weeks, with assessments at baseline, mid-training, post-training, and 3 months post-training.
- University Hospitals of Leicester NHS Trust, UK, with supervised stationary cycling and clinical assessments.
- Randomized and controlled study design.

## Protocol

- HIIT A / HIIT B cycling.
- Modality: Stationary cycling.
- Work intervals: HIIT A: 4-, 2-, and 1-min intervals; HIIT B: 4 x 4-min intervals.
- Recovery: HIIT A: 2 min active rest; HIIT B: 3 min active rest plus final active stage.
- Sets or repetitions: HIIT A mixed interval sequence; HIIT B 4 intervals.
- Intensity: 80-90% watts at VO2peak, aiming for 85-95% HRpeak.
- Session duration: About 45 min including warm-up/cool-down.
- Frequency: About 3 sessions/week.
- Program length: 24 sessions.
- Progression: 80% progressing to 90% watts at VO2peak over 8 weeks.
- MICT.
- Modality: Stationary cycling.
- Sets or repetitions: Continuous brisk cycling.
- Intensity: 50-60% VO2peak, RPE 12-14.
- Session duration: About 40 min plus warm-up/cool-down.
- Frequency: About 3 sessions/week.
- Program length: 24 sessions.
- Progression: Time adjusted according to intensity to match work.

## Outcomes

### Session adherence
Status: improved
Participants who completed the intervention attended 92% of sessions.

Mean 22/24 sessions; average 10 +/- 3 weeks to complete.

### Intensity feasibility
Status: mixed
Power-output intensity targets were difficult, especially for HIIT A, but heart-rate targets were more often achieved.

Required power achieved by 8/20 completers; secondary HRpeak criteria achieved by 15/20.

### Safety
Status: improved
No major adverse events were reported.

### VO2peak and peak power
Status: improved
VO2peak and peak power increased descriptively in all groups.

VO2peak mL/kg/min pre/post: HIIT A 24.28 to 27.06; HIIT B 24.65 to 27.48; MICT 29.33 to 33.05.

## Practical Insights

- Supervised cycle HIIT can be acceptable to stable kidney transplant recipients but should use achievable intensity targets.
- A familiarization period and shorter hard intervals may improve feasibility.
- Flexible scheduling or partial home-based delivery may improve recruitment and retention.

## Limitations

- Pilot sample size and not powered for efficacy.
- Baseline heterogeneity.
- Intensity target based on watts may not have matched participants' ability to repeat intervals.
- Variable time to complete 24 sessions.
- Follow-up attrition.

## Safety And Adherence

- No major adverse events were reported.
- One abdominal pain session stop was clinically reviewed and considered unrelated to exercise.
- One session stop was due to urinary tract infection pain under clinical treatment.
- Cold/flu symptoms led to many cancelled and rescheduled sessions.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/35597974/) (pubmed)
- [DOI](https://doi.org/10.1186/s40814-022-01067-3) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9123685/) (full text)

## Agent Guidance

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