# Effects of a 4-week high-intensity interval training on pacing during 5-km running trial

PMID: 29069224
Journal: Brazilian journal of medical and biological research = Revista brasileira de pesquisas medicas e biologicas
Published: 2017 Oct 19
Authors: Silva R, Damasceno M, Cruz R, Silva-Cavalcante MD, Lima-Silva AE, Bishop DJ, Bertuzzi R

## Question

Does 4 weeks of running HIIT alter pacing strategy during a 5-km time trial, and does it improve physiological determinants of endurance performance in recreational runners?

## Summary

In recreational male 5-km runners, adding two weekly supervised running HIIT sessions for 4 weeks improved running economy and peak treadmill speed but did not significantly change VO2max, OBLA, 5-km time-trial performance, or pacing pattern compared with maintaining regular training.

## Population

- Male recreational long-distance runners with recent 5-km race experience.
- Sample size: 16
- Age: HIIT 35 +/- 6 years; control 32 +/- 9 years
- Sex: Men
- Fitness level: Recreational runners, best 5-km under 25 min
- Health status: No clinical condition details reported

## Methodology

- Randomized controlled 4-week training study
- 4 weeks
- Supervised outdoor/track running training and laboratory treadmill testing
- Randomized and controlled study design.

## Protocol

- 4-week running HIIT.
- Modality: Running.
- Work intervals: 50% of individual Tlim at vVO2max.
- Recovery: Equal-duration active recovery at 60% vVO2max.
- Sets or repetitions: 5 intervals.
- Intensity: vVO2max work intervals.
- Session duration: Warm-up plus five work/recovery pairs.
- Frequency: 2 sessions/week.
- Program length: 4 weeks.
- Progression: No explicit progression reported.
- Regular endurance training.
- Modality: Running/endurance training.
- Intensity: Usual low-intensity continuous aerobic training at 50-70% VO2max.
- Frequency: Usual routine.
- Program length: 4 weeks.
- Progression: Maintain regular training.

## Outcomes

### Running economy
Status: improved
Running economy improved more in HIIT than control.

Between-group percent-change comparison p=0.012.

### Peak speed
Status: improved
Peak treadmill speed improved more in HIIT than control.

Between-group percent-change comparison p=0.019.

### VO2max
Status: no clear change
VO2max did not differ significantly between groups after training.

p=0.495.

### 5-km pacing
Status: no clear change
5-km pacing, time, HR, and RPE did not show significant between-group changes.

Reported p>0.05 for 5-km outcomes.

## Practical Insights

- A short two-day-per-week running HIIT block may improve economy and peak speed.
- Do not infer 5-km pacing or time-trial improvement from this 4-week protocol.

## Limitations

- Small sample
- Men only
- Recreational runners only
- Short 4-week duration
- Individual time trial rather than competitive race

## Safety And Adherence

- No adverse events reported in the article.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/29069224/) (pubmed)
- [DOI](https://doi.org/10.1590/1414-431X20176335) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5649866/) (full text)

## Agent Guidance

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