Short-Term Sprint Interval Training Increases Maximal Oxygen Uptake Without Changing Maximal Cardiac Output
Bibliographic record
Abstract
Traditional moderate intensity continuous training increases maximal oxygen uptake (VO2max). This effect is primarily attributed to an increased maximal cardiac output (Qmax), as predicted by the Fick principle. Sprint interval training (SIT) increases VO2max similar to MICT, often despite a lower training volume, but the effect on Qmax is unclear. PURPOSE: To determine the effect of 6 sessions of SIT over 2 wk on VO2max, Qmax and exercise performance in healthy, untrained adults [n=12 (9 females); 21±2 y; mean±SD]. METHODS: Training was performed on a cycle ergometer and involved a 2-min warm-up (50 W), 3 x 20-s ‘all-out’ bouts interspersed with 2-min of recovery (50 W), and a 3-min cool-down (50 W). VO2max was determined using a ramp test to exhaustion. Qmax was subsequently determined using inert gas rebreathing (Innocor) over a 2-min period of exercise performed at 90% of the peak work rate attained during the VO2max test. Pilot testing confirmed this protocol elicited VO2max over the 2-min period of Qmax measurement. The performance test was a 2 kJ/kg body weight cycling time trial. All measurements were performed twice at baseline, and reproducibility determined as a coefficient of variation (CV). The CV for VO2max, Qmax and time trial performance was 5.8, 4.7 and 4.2%, respectively. Pre- and post-training measurements were compared using a paired t-test. RESULTS: VO2max increased after SIT from 37.0±7.3 to 40.7±8.3 ml/kg/min (p<0.001), but Qmax was unchanged (17.2±3.8 vs 17.7±4.6 L/min; p>0.05). Exercise performance improved after SIT from 1040±247 to 938±238 s (p<0.001). Absolute VO2max was positively correlated with Qmax (r2 = 0.86, p < 0.001). CONCLUSION: Six sessions of SIT increased VO2max without changing Qmax in previously untrained individuals. These data support previous suggestions that the early increase in VO2max after SIT may be due mainly to peripheral responses (i.e., enhanced oxygen extraction by skeletal muscle), rather than a central change in blood oxygen delivery. Supported by NSERC
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".