# Physiological Responses During High-Intensity Interval Training in Young Swimmers

PMID: 34276394
Journal: Frontiers in Physiology
Published: 2021
Authors: Almeida TAF, Pessôa Filho DM, Espada MC, Reis JF, Sancassani A, Massini DA, Santos FJ, Alves FB

## Question

Do 100 m and 200 m swimming interval protocols at maximal aerobic velocity produce different temporal, perceptual, oxygen-uptake, lactate, and oxygen-deficit responses in young swimmers?

## Summary

Twelve well-trained young swimmers completed two swimming interval protocols at maximal aerobic velocity: repeated 100 m bouts with 15 s rest and repeated 200 m bouts with 30 s rest. Both reached similar near-maximal oxygen uptake, lactate, oxygen-deficit, distance, and time-to-exhaustion responses, but the first 800 m of 100 m repeats felt easier than 200 m repeats.

## Population

- 12 well-trained young competitive swimmers.
- Sample size: 12
- Age: 15.3 +/- 1.4 years
- Sex: 7 males, 5 females
- Fitness level: State or national championship swimmers for at least 3 years
- Health status: No health conditions reported; informed consent/guardian consent obtained

## Methodology

- Randomized-order within-subject acute exercise physiology comparison
- Three testing protocols separated by at least 48 h
- 25 m swimming pool at the beginning of the preparatory period
- Randomized and controlled study design.

## Protocol

- IT100 swimming intervals.
- Modality: Front crawl swimming.
- Work intervals: 100 m.
- Recovery: 15 s rest.
- Sets or repetitions: n repetitions to voluntary exhaustion.
- Intensity: 100% MAV; actual 99.7 +/- 2.6% MAV.
- Session duration: 1034.8 +/- 462.8 s time limit for full IT100.
- Frequency: One acute session.
- Program length: Acute randomized-order comparison.
- Progression: None.
- IT200 swimming intervals.
- Modality: Front crawl swimming.
- Work intervals: 200 m.
- Recovery: 30 s rest.
- Sets or repetitions: n repetitions to voluntary exhaustion.
- Intensity: 100% MAV target; actual 96.8 +/- 2.4% MAV.
- Session duration: 826.1 +/- 302.7 s time limit for full IT200.
- Frequency: One acute session.
- Program length: Acute randomized-order comparison.
- Progression: None.

## Outcomes

### Peak VO2
Status: no clear change
Peak VO2 was similar between 100 m and 200 m protocols and not different from incremental VO2peak.

IT8x100 57.3 +/- 4.9 vs IT4x200 57.2 +/- 4.6 ml/kg/min, p=0.98; comparison with VO2peak p=0.37.

### RPE
Status: mixed
The 100 m protocol felt easier than the 200 m protocol over the first 800 m, but full-protocol RPE did not differ.

IT8x100 7.62 +/- 2.0 vs IT4x200 9.5 +/- 0.7, p=0.012; full IT100 vs IT200 p=0.55.

### Lactate
Status: no clear change
Peak lactate did not significantly differ between full protocols.

IT100 7.9 +/- 3.4 vs IT200 8.7 +/- 1.5 mmol/L, p=0.15.

### Time near VO2peak
Status: no clear change
Time above VT2, 90%, and 95% VO2peak did not differ between interval formats.

IT8x100 vs IT4x200: t@VT2 p=0.72, t@90 p=0.63, t@95 p=1.00; IT100 vs IT200: p=0.22, p=0.29, p=0.16.

## Practical Insights

- For trained swimmers, 100 m repeats with 15 s rest may deliver a similar aerobic stimulus to 200 m repeats with 30 s rest while feeling easier early in the set.
- Interval length can be selected by perceived difficulty even when physiological targets are similar.

## Limitations

- Small sample
- Male and female swimmers combined
- Snorkel and open turns may constrain normal free swimming
- Only 100% MAV was tested
- Acute physiology study only

## Safety And Adherence

- No adverse events or injuries were reported.
- Participants were supervised, familiarized with equipment, and sessions were separated by at least 48 h.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/34276394/) (pubmed)
- [DOI](https://doi.org/10.3389/fphys.2021.662029) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8281220/) (full text)

## Agent Guidance

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