# Enjoyment for High-Intensity Interval Exercise Increases during the First Six Weeks of Training: Implications for Promoting Exercise Adherence in Sedentary Adults

PMID: 27973594
Journal: PloS one
Published: 2016
Authors: Heisz JJ, Tejada MG, Paolucci EM, Muir C

## Question

How does enjoyment of high-intensity interval training change across the first six weeks of training compared with moderate continuous training in sedentary young adults?

## Summary

Sedentary young adults did six weeks of supervised cycling HIT or energy-matched moderate continuous cycling. HIT was more strenuous, but enjoyment rose over the six weeks and became higher than MCT by weeks five and six; increases in workload predicted increases in enjoyment.

## Population

- Sedentary healthy young adults from McMaster University
- Sample size: 40
- Age: Analyzed means: HIT 21.4 (2.9), MCT 20.4 (1.3) years
- Sex: Analyzed sample: HIT 12 female/5 male; MCT 13 female/6 male
- Fitness level: No more than 1 hour/week vigorous physical activity
- Health status: Healthy young adults

## Methodology

- Randomized parallel-group training study
- 6 weeks
- University supervised cycle-ergometer training sessions
- Randomized and controlled study design.

## Protocol

- Cycling HIT.
- Modality: Cycle ergometer.
- Work intervals: 1 min at workload to elicit 90-95% peak HR.
- Recovery: 1 min at 30% PPO, minimum 50 W.
- Sets or repetitions: 10 bouts.
- Intensity: 90-95% peak HR; RPE about 15-16.
- Session duration: 25 min including 3-min warm-up and 2-min cool-down.
- Frequency: About 3 sessions/week.
- Program length: 6 weeks.
- Progression: Workload adjusted to elicit target HR.
- MCT.
- Modality: Cycle ergometer.
- Work intervals: Continuous cycling.
- Intensity: 70-75% peak HR; RPE about 11.
- Session duration: 32.5 min including 3-min warm-up, 27.5-min continuous work, and 2-min cool-down.
- Frequency: About 3 sessions/week.
- Program length: 6 weeks.
- Progression: Workload adjusted to target HR.

## Outcomes

### Enjoyment
Status: improved
HIT enjoyment increased over time and exceeded MCT late in training.

Group x week F(5,170)=3.54, p<0.05; week 5 p<0.05, d=0.9; week 6 p<0.01, d>1.

### Workload
Status: improved
Workload increased across training and predicted enjoyment change.

Workload week effect p<0.001; regression DeltaF(1,32)=10.46, p<0.01.

### Fitness
Status: improved
Both protocols improved VO2peak and PPO with no group difference.

VO2peak pre/post F(1,34)=17.93, p<0.001; PPO F(1,34)=57.69, p<0.001; no group interaction.

### RPE
Status: mixed
HIT was more strenuous than MCT but enjoyment still increased.

HIT elicited higher workload, HR, and RPE than MCT, all p<0.001.

### Cortisol
Status: no clear change
Morning cortisol, body mass, and BMI did not significantly change.

All p>0.05.

## Practical Insights

- Enjoyment may improve when users see their interval workload increase.
- Early challenging HIT does not necessarily reduce enjoyment among healthy sedentary young adults.

## Limitations

- Short six-week duration
- Incentivized supervised setting
- No long-term adherence endpoint
- Some missing enjoyment data and HIT exclusions

## Safety And Adherence

- One HIT participant had a noxious response during the first exercise session.
- Another HIT participant did not complete because of scheduling conflict.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/27973594/) (pubmed)
- [DOI](https://doi.org/10.1371/journal.pone.0168534) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5156428/) (full text)

## Agent Guidance

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