Improved Glycemic Control Induced By Evening Activity Breaks Does Not Persist Overnight Amongst Healthy Adults.

PURPOSE: Experimental studies indicate resistance exercise regular activity breaks, performed in the evening, improve acute glycemic control. However, the duration of the persistence of this effect in healthy individuals is unknown. This study aimed to compare the effect of 4 hours of laboratory based regular activity breaks to prolonged sitting, on subsequent 24 h free-living interstitial glucose levels, in a group of healthy adults. METHODS: In this randomized crossover trial, twenty-eight healthy adults (female n = 20, mean ± SD age 25.5 y ± 5.6, BMI 29.2 kg/m2 ± 6.9) completed two, 4-hour laboratory-based interventions commencing at ~1700 h: 1) prolonged sitting (SIT) and 2) prolonged sitting interrupted with 3 min of body weight resistance exercise activity breaks every 30 min (RAB). Upon completion, participants returned to a free-living setting. Interstitial glucose concentrations were monitored via a FreeStyle Libre Pro Continuous Glucose Monitor during and for 24 h after each intervention. Measures of glycemic control [mean glucose and total area under the curve (AUC)] and variability [continuous overall net glycemic action at 1 hour (CONGA-1) and SD glucose] were calculated. RESULTS: During the 4-hour intervention period, RAB lowered mean glucose by 8.3% (-0.47 mmol/L, 95% CI -0.74 to 0.20, p = 0.001) and AUC by 8.9% (-2.01 mmol/L/hour, 95% CI -3.05 to -0.97, p < 0.001) compared to SIT. Measures of glycemic variability were not significantly different during the intervention. There were no significant differences in mean glucose and AUC between conditions during the first nocturnal period and 24 hours post intervention. Compared to SIT, RAB resulted in a 21.7% (0.18 mmol/L 95% CI 0.03 to 0.29, p = 0.018) and 10.1% (0.09 mmol/L 95% CI 0.01, 0.17 p = 0.025) greater CONGA-1 in the first nocturnal period and 24 hours post intervention, however, for the majority of participants variability was maintained within the healthy range. Compared to SIT, SD glucose was 26.2% greater following RAB in the first nocturnal period (95% CI 4.9 to 42.7, p = 0.019) and 14.9% greater in the 24-hours post intervention (95% CI 6.6 to 22.4, p = 0.001). CONCLUSION: Improvements in glycemic control induced by evening regular activity breaks do not appear to persist overnight, or into the 24-hours following the intervention in healthy individuals. Health Research Council of New Zealand