# Six Sessions of Sprint Interval Training Improves Running Performance in Trained Athletes

PMID: 29076961
Journal: Journal of strength and conditioning research
Published: 2018 Mar
Authors: Koral J, Oranchuk DJ, Herrera R, Millet GY

## Question

Can six sessions of field-based sprint interval training improve running performance in trained athletes?

## Summary

In 16 trained trail runners, six sessions of field-based 30-second all-out shuttle-run sprint interval training over two weeks improved 3000 m time-trial performance, maximal aerobic speed, and time to exhaustion. Because there was no control group, the results are suggestive rather than definitive.

## Population

- Healthy trained trail runners with at least 3 years of running training.
- Sample size: 16
- Age: Men 21.1 +/- 3.6 years; women 22.8 +/- 3.0 years
- Sex: 12 men and 4 women
- Fitness level: Trained runners, at least 50 km/week for at least 3 years
- Health status: Healthy after routine medical screening

## Methodology

- One-group pre/post intervention
- 2 weeks
- Field-based running track protocol

## Protocol

- Field-based sprint interval training.
- Modality: 30 m shuttle running.
- Work intervals: 30 seconds.
- Recovery: 4 minutes rest/walking.
- Sets or repetitions: 4-7 bouts.
- Intensity: Maximal all-out effort.
- Session duration: Sprint block varied by number of bouts; warm-up included light contractions, 5 min aerobic exercise, and 6 progressive 20 m runs.
- Frequency: 3 sessions per week.
- Program length: 2 weeks.
- Progression: Bouts increased from 4 to 7 over first five sessions and reduced to 4 bouts in final session.

## Outcomes

### 3000 m time
Status: improved
3000 m time-trial performance improved after six SIT sessions.

-50.4 s, about -5.7%, p<0.001, d=0.35.

### MAS
Status: improved
Maximal aerobic speed improved modestly.

+0.41 km/h, about +2.8%, p=0.01, d=0.22.

### Time to exhaustion
Status: improved
Time to exhaustion at 90% pre-intervention MAS improved substantially.

+158.9 s, about +42%, p=0.001, d=0.74.

### Sprint output
Status: improved
Peak and mean sprint outputs improved across the intervention.

Peak output +2.4%, p=0.009; mean output +2.9%, p=0.002.

### Fatigue index
Status: no clear change
Fatigue index did not significantly change.

p=0.17.

## Practical Insights

- A short field-based sprint interval block can be practical for trained runners when sprint quality and long recovery are prioritized.
- The protocol is not beginner-oriented because it uses all-out shuttle running and a trained athlete sample.
- The absence of a control group limits causal certainty.

## Limitations

- No control group.
- Small sample.
- Short two-week intervention.
- VO2max was estimated rather than directly measured.
- Field tests are less precise than laboratory measures.
- No muscle biopsy, EMG, or direct VO2 measures were used to confirm mechanisms.

## Safety And Adherence

- Participants underwent routine medical screening.
- No adverse events or dropouts were reported in the extracted text.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/29076961/) (pubmed)
- [DOI](https://doi.org/10.1519/JSC.0000000000002286) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5839711/) (full text)

## Agent Guidance

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