# Response to Three Weeks of Sprint Interval Training Cannot Be Explained by the Exertional Level

PMID: 32784754
Journal: Medicina
Published: 2020-08-07
Authors: Krusnauskas R, Eimantas N, Baranauskiene N, Venckunas T, Snieckus A, Brazaitis M, Westerblad H, Kamandulis S

## Question

Can different responses to 3 weeks of sprint interval training be explained by exertional level during training?

## Summary

In healthy untrained men, 3 weeks of supervised all-out sprint interval cycling improved VO2peak overall and average sprint power, but people differed in power response. The difference between high and low responders was not explained by heart-rate intensity, lactate response, or acute muscle fatigue measures.

## Population

- Healthy untrained men
- Sample size: 26
- Age: 25.7 +/- 6.03 years
- Sex: Male
- Fitness level: Untrained for aerobic and strength exercise for 6 months
- Health status: Medically screened healthy adults

## Methodology

- Single-arm supervised sprint interval training study with responder subgroup analysis
- 3 weeks
- Supervised laboratory cycle ergometer sessions

## Protocol

- SIT.
- Modality: Cycle ergometer.
- Work intervals: 30 s all-out sprint.
- Recovery: 4 min very low resistance pedaling.
- Sets or repetitions: 4 to 6 per session; 47 total.
- Intensity: All-out against 7.5% body mass resistance.
- Session duration: Varied by bout count.
- Frequency: 3 sessions/week.
- Program length: 3 weeks.
- Progression: Bout count progressed across 9 sessions.
- Responder subgroup.
- Modality: Same SIT protocol.
- Work intervals: 30 s all-out sprint.
- Recovery: 4 min very low resistance pedaling.
- Sets or repetitions: Same prescribed dose.
- Intensity: All-out against 7.5% body mass resistance.
- Session duration: Same as intervention.
- Frequency: 3 sessions/week.
- Program length: 3 weeks.
- Progression: Same bout-count progression.

## Outcomes

### VO2peak
Status: improved
VO2peak increased overall after 3 weeks of SIT.

p=0.03; no group difference p=0.98.

### Sprint power
Status: mixed
Average power increased in both groups but much more in high responders.

High responders +0.80 +/- 0.22 W/kg; low responders +0.22 +/- 0.19 W/kg; group difference p<0.001.

### Exertion
Status: no clear change
Heart-rate intensity and lactate responses did not explain responder status.

Training HR 92.2 +/- 3.6% versus 94.6 +/- 4.6% HRmax, p=0.17; lactate group/test/time interaction p=0.95.

## Practical Insights

- Individual response should be tracked rather than inferred from effort alone.
- All-out cycling SIT is a high-strain protocol needing screening.
- Early sessions may require more recovery than later adapted sessions.

## Limitations

- No control group
- Male-only sample
- Short intervention
- No gas analysis during SIT
- Lactate sampling missed immediate exercise peaks
- Technique and lifestyle factors not assessed

## Safety And Adherence

- No adverse events were reported.
- Medical screening excluded overt cardiovascular, pulmonary, metabolic, and chronic joint pain conditions.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/32784754/) (pubmed)
- [DOI](https://doi.org/10.3390/medicina56080395) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7466197/) (full text)

## Agent Guidance

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