# Improvements in Attention and Cardiac Autonomic Modulation After a 2-Weeks Sprint Interval Training Program: A Fidelity Approach

PMID: 29618979
Journal: Frontiers in Physiology
Published: 2018
Authors: de Sousa AFM, Medeiros AR, Benitez-Flores S, Del Rosso S, Stults-Kolehmainen M, Boullosa DA

## Question

Does a 2-week sprint interval training program improve attention and cardiac autonomic modulation, and do responses differ by protocol fidelity?

## Summary

In healthy university students, a 2-week cycle sprint-interval program improved estimated VO2max, skinfold sum, and some attention/autonomic measures. Participants who reached the target heart-rate fidelity more often showed clearer accuracy and heart-rate-variability changes.

## Population

- Healthy young university students allocated to sprint interval training or control
- Sample size: 91
- Age: Group means about 22-25 years
- Sex: Men and women; exact total sex distribution varied by group
- Fitness level: Healthy students with unspecified sport background
- Health status: No cardiovascular/metabolic disease, attention disorders, pregnancy, tobacco, medications, supplements, or drugs affecting evaluations

## Methodology

- Randomized controlled intervention with post hoc fidelity grouping
- 2 weeks
- Supervised cycle-ergometer sprint interval sessions and laboratory testing
- Randomized and controlled study design.

## Protocol

- Two-week cycle sprint interval training.
- Modality: Cycle ergometer.
- Work intervals: 30 s all-out sprint.
- Recovery: 3-4 min active no-load recovery at 60 rpm.
- Sets or repetitions: 3 sprints in sessions 1 and 6; 4 sprints in sessions 2-5.
- Intensity: All-out at 7.5% body mass; fidelity criterion >90% estimated HRmax.
- Session duration: 12-24 min.
- Frequency: 3 sessions/week.
- Program length: 2 weeks.
- Progression: Recovery shortened from 4 min in week 1 to 3 min in week 2.
- No-training control.
- Modality: No sprint interval training.
- Program length: 2 weeks.

## Outcomes

### VO2max
Status: improved
Both high- and low-fidelity sprint groups improved estimated VO2max versus baseline.

HIGH 36.9 +/- 8.6 to 41.5 +/- 6.4; LOW 38.7 +/- 9.1 to 43.5 +/- 9.7; p < 0.05 time effects

### Skinfolds
Status: improved
Sprint groups, but not control, reduced skinfold sum.

HIGH and LOW improved skinfold sum and mean warm-up HR; control did not

### Attention
Status: improved
Conflict effect improved in both sprint groups; accuracy improved only in the high-fidelity group.

Conflict HIGH 152.5 +/- 63.3 to 121.7 +/- 44.7; LOW 131.2 +/- 48.9 to 106.97 +/- 36.79; accuracy HIGH 96.2 +/- 6.5 to 98.5 +/- 2.6

### HRV
Status: mixed
Autonomic measures changed, with clearer resting complexity and vagal-modulation changes in the high-fidelity group.

Significant HR/HRV time effects; HIGH showed significant HR and HRV complexity changes at rest

## Practical Insights

- Very short all-out cycling sprint programs can move fitness and some cognitive/autonomic markers quickly.
- Protocol fidelity matters: achieving target intensity may change which outcomes improve.
- A low-volume sprint plan still had time and intensity demands that caused some withdrawals for lack of time.

## Limitations

- Aerobic fitness was estimated indirectly
- Incidental physical activity and diet were not controlled
- Training/sport background was not fully described
- Estimated HRmax was used for fidelity classification
- Short intervention

## Safety And Adherence

- The article did not clearly report adverse-event incidence.
- Seventeen intervention participants and one control withdrew because of lack of time.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/29618979/) (pubmed)
- [DOI](https://doi.org/10.3389/fphys.2018.00241) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5871711/) (full text)

## Agent Guidance

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