Heart Rate and Oxygen Uptake During Recovery from High-Intensity Interval Training: A Retrospective Analysis
Question
How do heart rate and oxygen uptake during active recovery compare with work intervals across low-volume cycling HIIT protocols?
Summary
This retrospective pooled analysis found that active recovery periods during short cycling HIIT maintained heart rate and oxygen uptake at levels similar to the work intervals. Recovery periods therefore contributed substantial cardiovascular load rather than being physiologically idle.
Methodology
- Healthy physically active adults
- 104 participants.
- Cycle ergometer.
- Work intervals: 30 to 60 s.
- Recovery: 10 to 75 s active recovery.
- Intensity: 70-85% Wmax; peak HR about 90.7% HRmax.
- Varied.
- Single-session data.
- Retrospective acute analysis.
- Retrospective pooled analysis of prior within-subject cycling HIIT studies
- Heart rate, Oxygen uptake, and Relative intensity were tracked.
Outcomes
Heart rate
Mean heart rate was similar during exercise and active recovery intervals.
159 +/- 14 versus 160 +/- 15 bpm, p=0.48.
Oxygen uptake
Mean oxygen uptake was similar during exercise and active recovery intervals.
1.97 +/- 0.47 versus 1.98 +/- 0.48 L/min, p=0.82.
Fitness strata
Lower-fitness participants reached higher percentages of VO2max than fitter participants.
Example strata: fit men 66.5% VO2max versus lower-fitness women 86.8% VO2max.
Insights
- Short active recovery can remain a high cardiovascular-load period.
- Rest design should be included in total HIIT dose decisions.
- Lower-fitness users may need easier or longer recovery even when work intervals are the same.
Limitations
- Retrospective pooled analysis
- Different original protocols
- Healthy active young adults
- Cycling only
- Active recovery only
Safety
- No adverse-event or adherence outcomes were reported in the retrospective analysis.