Intermittent walking, but not standing, improves postprandial insulin and glucose relative to sustained sitting: A randomised cross-over study in inactive middle-aged men.

ABSTRACT

OBJECTIVES: Interrupting prolonged periods of sitting may improve postprandial insulin and glucose although it is unclear whether interruptions need to involve physical activity or simply a change in posture (from sitting to standing) to benefit adults without metabolic impairment. This study examined effects of interrupting sitting with intermittent walking, and intermittent standing on dynamic insulin and glucose responses in men without known metabolic impairment. DESIGN: A randomised three-arm, cross-over experimental study comprising three seven-hour days of sustained sitting. METHODS: Twenty-five inactive men (aged 40.2±12.2 years) took part. The three interventions were; SIT-ONLY (uninterrupted sitting), SIT-STAND (sitting interrupted with 2min standing bouts every 20min) and SIT-WALK (sitting interrupted with 2min light-intensity walking bouts every 20min). An oral glucose tolerance test was administered at baseline and a standardised mixed test meal at hour three. Comparisons of Matsuda Index, and area under the curve (AUC) for insulin and glucose were made between interventions using generalised estimating equation models. RESULTS: Matsuda index was 16% higher (mean difference 1.2 [95%CI 0.1, 2.2] p=0.02), AUC for glucose 9% lower (-2.5mmol/L×7h [-3.7, -1.3mmol/L×7h] p<0.001) and AUC for insulin 21% lower (-546.5pmol/L×7h [-723.6, -369.3pmol/L×7h] p<0.001) in SIT-WALK compared to SIT-ONLY. There were no significant differences between SIT-STAND and SIT-ONLY in any main outcome measure. CONCLUSIONS: Interrupting sustained sitting with brief repeated bouts of light-intensity walking but not standing reduced insulin demand and improved glucose uptake during a simulated sedentary working day. The benefits of such minor behavioural changes could inform future workplace health interventions.