# High Intensity Interval Training Leads to Greater Improvements in Acute Heart Rate Recovery and Anaerobic Power as High Volume Low Intensity Training

PMID: 28824457
Journal: Frontiers in physiology
Published: 2017
Authors: Stöggl TL, Björklund G

## Question

Do different endurance training concepts, especially HIIT and polarized training versus high-volume low-intensity training, change anaerobic power and acute heart-rate recovery in well-trained endurance athletes?

## Summary

In well-trained endurance athletes, a 9-week program emphasizing blocked 4 x 4-minute HIIT improved maximal anaerobic test peak velocity/power and heart-rate recovery more than a high-volume low-intensity control program. Polarized training improved heart-rate recovery but did not clearly improve peak anaerobic test performance.

## Population

- Well-trained competitive endurance athletes from several endurance sports.
- Sample size: 36
- Age: 31 +/- 6 years
- Sex: 33 male, 3 female
- Fitness level: VO2max 61.9 +/- 8.0 mL/kg/min; 10-20 h/week training
- Health status: Healthy athletes

## Methodology

- Controlled parallel-group training intervention
- 9-week intervention plus pre- and post-testing
- Athletes trained in their sport modality and completed laboratory treadmill or cycling tests
- Randomized and controlled study design.

## Protocol

- Blocked 4 x 4 HIIT.
- Modality: Running or cycling.
- Work intervals: 4 minutes.
- Recovery: 3 minutes active recovery.
- Sets or repetitions: 4 intervals.
- Intensity: 90-95% HRmax.
- Session duration: About 63 minutes including warm-up and cool-down.
- Frequency: Block periodized; 27 +/- 1 HIIT sessions over 9 weeks.
- Program length: 9 weeks.
- Progression: Adaptation week, two 16-day interval blocks, recovery weeks.
- Polarized training and HVLIT control.
- Modality: Sport-specific endurance training.
- Work intervals: POL included some 4 x 4 HIIT sessions; HVLIT had no HIIT.
- Recovery: Varied by session.
- Sets or repetitions: POL: mix of HIIT, long LIT, and sprints; HVLIT: high-volume LIT and threshold sessions.
- Intensity: LIT <2 mmol/L lactate; MIT 3-5 mmol/L; HIIT >90% HRmax.
- Session duration: Varied; POL and CG had higher total training hours than HIIT.
- Frequency: About 54 sessions for POL and CG/HVLIT over 9 weeks.
- Program length: 9 weeks.
- Progression: Three 3-week blocks with recovery weeks for POL and CG/HVLIT.

## Outcomes

### Peak power
Status: improved
Only HIIT significantly improved MART/MACT peak velocity or power.

HIIT +6.4%, p<0.001; time x group p=0.001.

### Heart-rate recovery
Status: improved
HIIT and polarized training improved HR recovery, while HVLIT did not.

HIIT +11.2%, p=0.002; POL +7.9%, p=0.023; time x group p=0.011.

### Lactate thresholds
Status: no clear change
Velocity or power at 4, 6, and 10 mmol/L did not improve in any group.

All p>0.05.

### Peak lactate
Status: improved
Peak lactate increased only in the HIIT group.

HIIT +7.3%, p=0.001; time x group p=0.027.

## Practical Insights

- 4 x 4-minute HIIT blocks may improve anaerobic capacity markers in trained athletes.
- HR recovery may be useful for monitoring high-intensity adaptation.
- HVLIT may not maintain or improve all high-intensity performance qualities.

## Limitations

- Mixed endurance sports and testing modes.
- Small female representation.
- No direct neuromuscular measures.
- Competition-performance transfer was not tested.

## Safety And Adherence

- No adverse events were specifically reported in the viewed text.
- Some participants withdrew or were excluded due to illness or competition schedule changes.

## Original Sources

- [PubMed](https://pubmed.ncbi.nlm.nih.gov/28824457/) (pubmed)
- [DOI](https://doi.org/10.3389/fphys.2017.00562) (doi)
- [PMC full text](https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5539186/) (full text)

## Agent Guidance

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