# The Feasibility of High-Intensity Interval Training in Patients with Intensive Care Unit-Acquired Weakness Syndrome Following Long-Term Invasive Ventilation

PMID: 33527199
Journal: Sports medicine - open
Published: 2021-02-01
Authors: Wernhart S, Hedderich J, Wunderlich S, Schauerte K, Weihe E, Dellweg D, Siemon K

## Question

Is a HIIT bicycle-ergometer protocol feasible and safe in early rehabilitation patients with ICU-acquired weakness after long-term invasive ventilation, and how do outcomes compare with moderate continuous training?

## Summary

This retrospective rehabilitation study compared two bicycle-ergometer training protocols in patients recovering from long invasive ventilation with ICU-acquired weakness. Patients trained five days per week for three weeks in an early rehabilitation facility. The HIIT-style protocol used five cycles inside a 14-minute session with hard phases rated 7/10 and active recovery rated 4/10 on the Borg CR10 scale. No major adverse events were observed, and both HIIT and moderate continuous training improved walking distance, lung function, inspiratory pressure, and functional status. HIIT showed a trend toward greater six-minute-walk improvement, but group assignment was not randomized and the authors caution that the protocol may have been moderate rather than truly high intensity.

## Population

- Post-ICU patients with ICU-acquired weakness after at least 7 days of invasive ventilation.
- Sample size: 46
- Age: HIIT mean 63.6 years; MCT mean 70.3 years
- Sex: HIIT 59.1% male; MCT 70.8% male
- Fitness level: Severely deconditioned early rehabilitation patients
- Health status: ICU-acquired weakness with substantial cardiopulmonary comorbidity burden

## Methodology

- Retrospective non-randomized comparison of two established rehabilitation training protocols.
- 3 weeks
- Early rehabilitation facility directly following intensive care unit discharge.
- Controlled study design.

## Protocol

- HIIT bicycle ergometry.
- Modality: Bicycle ergometry.
- Work intervals: High-intensity phases at Borg CR10 7/10; exact interval duration not extracted.
- Recovery: Active recovery/cool-down phases at Borg CR10 4/10; exact duration not extracted.
- Sets or repetitions: Five cycles.
- Intensity: Borg CR10 7/10 hard phases.
- Session duration: 14 min.
- Frequency: 5 days/week.
- Program length: 3 weeks.
- Progression: Percentage of high-intensity training increased over time after run-in.
- Moderate continuous bicycle training.
- Modality: Bicycle ergometry.
- Work intervals: 10 min continuous moderate cycling.
- Recovery: 2 min warmup and 2 min cooldown at Borg CR10 0-1/10.
- Sets or repetitions: One continuous bout.
- Intensity: Borg CR10 4/10 for 10 min.
- Session duration: 14 min.
- Frequency: 5 days/week.
- Program length: 3 weeks.

## Outcomes

### Six-minute walk test
Status: improved
Both groups improved, with a trend toward greater improvement in HIIT.

HIIT +159.5 m (SD 64.9) vs MCT +120.4 m (SD 60.4); p=0.057 by Mann-Whitney, ANCOVA group effect p=0.055.

### Secondary respiratory and functional outcomes
Status: improved
VCmax, FEV1, PImax, FIM/FAM, and Barthel improved in both groups without significant between-group differences.

Between-group p values reported as nonsignificant.

### Safety
Status: mixed
No major adverse events occurred, but five sessions were terminated early for dizziness.

Two dizziness terminations in HIIT and three in MCT.

## Practical Insights

- Clinical HIIT can be feasible even in very fragile populations when intensity is Borg-guided and medically monitored.
- For safety-sensitive users, readiness checks and explicit stop criteria may matter as much as interval structure.
- The HIIT label needs verification: perceived hard intervals may not equal objective high-intensity work in severely deconditioned patients.

## Limitations

- Retrospective non-randomized design.
- Selection bias from clinician-assigned groups.
- No no-exercise control group.
- Semi-quantitative Borg intensity without CPET thresholds.
- Short intervention duration.
- Heterogeneous diagnoses and comorbidities.

## Safety And Adherence

- No major adverse events.
- Five premature exercise terminations due to dizziness; symptoms resolved within minutes.
- Strict session exclusion and termination criteria were used.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/33527199/) (pubmed)
- [DOI](https://doi.org/10.1186/s40798-021-00299-6) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7849616/) (full text)

## Agent Guidance

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