PMID 19175906

Research
All papers

Extremely short duration high intensity interval training substantially improves insulin action in young healthy males

Babraj JA, Vollaard NB, Keast C, Guppy FM, Cottrell G, Timmons JA

Question

Can an extremely low-volume high-intensity interval cycling program improve insulin action and glycemic control in young sedentary or recreationally active men despite very low total exercise energy expenditure?

Summary

Sixteen young healthy sedentary or recreationally active men completed 6 supervised sprint interval cycling sessions over 2 weeks. Each session used 4 to 6 all-out 30-second Wingate sprints with 4 minutes of recovery, for 2 to 3 minutes of hard work and 17 to 26 minutes total time per session. After training, glucose, insulin, and NEFA responses to an oral glucose tolerance test were lower, insulin sensitivity by Cederholm index improved, and 250-kJ cycling time-trial performance improved. The study supports a time-efficient SIT effect on whole-body insulin action in young men, but it was small, short, male-only, and did not use a conventional exercise control group.

Methodology

  • Young healthy sedentary or recreationally active men, with 16 in the main HIT intervention and 9 in a non-training variability experiment.
  • 25 participants.
  • Cycle ergometer Wingate sprints.
  • Work intervals: 30-second all-out sprint.
  • Recovery: 4 minutes rest on bike or low-cadence unloaded cycling.
  • Intensity: All-out against resistance equivalent to 7.5% body weight.
  • 17-26 minutes total time; 2-3 minutes sprint exercise.
  • 6 sessions over 14 days, with 1 or 2 rest days between sessions.
  • 2 weeks.
  • Short-term supervised pre-post intervention with a separate non-training variability group for repeated OGTT and time-trial measures.
  • Glucose response to OGTT, Insulin response to OGTT, Insulin sensitivity, and NEFA response to OGTT were tracked.

Outcomes

Glucose AUC

Plasma glucose AUC decreased by 12% after 2 weeks of HIT.

AUC pre 664 +/- 103 vs post 585 +/- 65 mmol*min*l-1; P < 0.001.

Improved

Insulin AUC and insulin sensitivity

Insulin AUC decreased by 37% and Cederholm insulin sensitivity improved by 23%.

Insulin AUC pre 4226 +/- 1912 vs post 2654 +/- 1252 mU*min*l-1, P < 0.001; Cederholm index pre 80 +/- 6 vs post 98 +/- 5, P < 0.01.

Improved

NEFA AUC

NEFA AUC decreased by 26% after training, while fasting NEFA showed a non-significant trend lower.

AUC pre 31584 +/- 13205 vs post 23370 +/- 8630 umol*min*l-1; P < 0.001. Fasting NEFA P = 0.058.

Improved

250-kJ cycling time trial

Time-trial performance improved by about 6%, with an average 75-second improvement.

Mean difference 75 s; 95% CI 21-126 s; P < 0.01.

Improved

Fasting glucose and insulin

Fasting plasma glucose and fasting plasma insulin were unaltered after training.

No clear change

Insights

  • A very low total dose of all-out interval work can improve short-term insulin-action markers in selected young men.
  • Long recoveries relative to sprint duration were part of the protocol; the study should not be interpreted as 30-second sprints with minimal rest.
  • The protocol is better translated as supervised or carefully screened SIT than as general beginner HIIT.

Limitations

  • Small sample size.
  • Young healthy male-only population.
  • Short 2-week intervention and no long-term follow-up.
  • No conventional non-exercise randomized control group for the main intervention effect.
  • Whole-body insulin sensitivity only; tissue-specific mechanisms were not measured.
  • Adherence experience and adverse-event details were not reported.

Safety

  • No adverse events or injuries were reported.
  • The article did not provide a detailed adverse-event monitoring protocol.