Aim: Few data exist on the effects of vigorous-intensity activity on blood glucose. The study aim was to determine the effects of 2-min and 4-min bouts of vigorous-intensity stair climbing on glucose levels.

Methods: Nine overweight/obese adults with prediabetes (40-64 years, HbA_1C 5.7%-6.4%) participated in a randomized cross-over design with three conditions on consecutive days: control; 2-min bouts of stair climbing once per hour for 8 h; and 4-min bouts of stair climbing once every 2 h for 8 h, with the two activity days randomized in order. Continuous glucose monitoring estimated five-minute average interstitial glucose values.

Results: Total physical activity and 12-h AUC did not differ significantly by condition. The 4-min bout caused a significant decrease in glucose after 30 min (Cohen's d = -0.91) compared to the control condition, while the 2-min bout did not (Cohen's d = -0.13). Post-exercise change in glucose varied by pre-exercise glucose and by condition. No significant change in post-exercise glucose with stair climbing was found when pre-exercise glucose was <90 mg/dl, but when pre-exercise glucose was ≥90 mg/dl, the 4-min condition caused significant reductions in glucose.

Conclusions: These results suggest short, intermittent bouts of vigorous-intensity exercise can be substituted for an equivalent volume of lower-intensity lifestyle activity when glucose is over 90 mg/dl.

Trial registration: Clinical Trials NCT02827383.