The impact of sprint interval training with or without weight loss on substrate oxidation in adults: A secondary analysis of the i-FLEX study
Question
Does sprint interval training change resting and submaximal substrate oxidation differently in adults who lose weight versus those who do not?
Summary
In adults completing 4 weeks of supervised cycling sprint interval training, those who lost any weight showed improved submaximal fat oxidation and lower exercise RER. Resting substrate oxidation did not change, and the weight-loss subgroup differed by sex and work volume.
Methodology
- Adults from the i-FLEX study grouped after training by whether body weight decreased
- 34 participants.
- Cycle ergometer.
- Work intervals: 30 s.
- Recovery: 4 min active recovery at minimum wattage.
- Intensity: Wingate sprints at 7.5% body weight.
- 4 min warm-up, sprint/recovery intervals, 5 min cool-down.
- 3 sessions/week.
- 4 weeks.
- Secondary analysis of a supervised sprint interval training intervention
- Substrate oxidation, Body composition, Cardiorespiratory fitness, and Training work were tracked.
Outcomes
Submax fat oxidation
The weight-loss subgroup increased submaximal fat oxidation.
WL 0.117 +/- 0.224 to 0.249 +/- 0.165 g/min, p = 0.008; group difference p = 0.005; interaction retained after covariate adjustment
Submax RER
Exercise RER fell in the weight-loss subgroup, although the adjusted interaction was weaker.
WL 0.96 +/- 0.08 to 0.92 +/- 0.06, p = 0.030; group difference p = 0.017; adjusted interaction p = 0.081
Resting oxidation
Resting substrate oxidation did not differ meaningfully by weight-loss response.
No significant resting substrate oxidation differences reported
Training work
Weight-loss participants completed higher work volume and had higher relative power.
Work volume 65,267 vs 47,062 kgm, p < 0.001; relative peak power p = 0.039; relative mean power p = 0.018
Insights
- Submaximal substrate changes after SIT may depend on weight change, sex distribution, and total work performed.
- Resting metabolism outcomes should not be inferred from submaximal exercise oxidation.
- Tracking training work volume may help explain heterogeneous responses.
Limitations
- Secondary analysis with post hoc weight-loss grouping
- Small sample
- Weight-loss group was mostly male and non-weight-loss group mostly female
- Baseline and post tests were not time-of-day matched
- Prior training experience was not recorded
Safety
- Sessions were supervised one-on-one; the article did not clearly report adverse-event counts.