The Effects Of Interrupting Sedentary Behavior With Hourly Physical Activity On Cardiometabolic Risk Factors In Healthy Adults

PURPOSE: Sedentary behavior is associated with increased risk of cardiometabolic diseases. Breaking up sitting with bouts of physical activity (PA) is associated with improved cardiometabolic profile in clinical populations. Few studies have investigated whether this improvement extends to healthy adults. The aim of this study was to examine whether breaking up sitting with hourly PA bouts improves the postprandial (PP) glucose and insulin responses in healthy adults compared to prolonged sitting. METHODS: Ten sedentary, inactive adults (5 men, 33.4 ± 4.6 years, BMI 25.3 ± 3.9, VO2max 43.7 ± 5.2 ml/kg/min) took part in an experimental crossover study with two randomly assigned 7-hr conditions: 1) prolonged sitting (SIT); and 2) 5 min 25 seconds of walking at 60-65% of VO2max (PA-5) on a treadmill (5.5% inclination) every 60 min. Trial conditions were iso-caloric and the test meals had an average macronutrient content of 34.4 ± 1% fat, 46 ± 4.5% carbohydrates and 20 ± 1.7% protein, respectively. Fasting blood samples were drawn from the antecubital vein at baseline and every 30 minutes throughout the trial. Total area under the curve (tAUC) for PP glucose and PP insulin was calculated using the trapezoidal rule. Net incremental area under the curve (iAUC) was calculated by subtracting the baseline area from tAUC. Differences between conditions were analyzed by two-tailed T-tests for paired observations. RESULTS: Glucose and insulin tAUC were 1.35% (p = 0,35) and 4.47% (p = 0,36) lower in PA-5 min compared to SIT. Insulin iAUC was significantly lower in PA-5 compared to SIT (p = 0.0014). There were no differences for iAUC for glucose (p = 0,24). CONCLUSIONS: Overall, there is limited evidence for an effect of interrupting sitting with PA of moderate intensity for five minutes every hour on glucose metabolism. These findings indicate that moderate intensity PA in hourly 5 min bouts may not be impactful enough to induce favorable change in glucose and insulin response in healthy adults. However, our results should be interpreted with caution due to the low number of participants. Future studies should include larger samples, alternative PA frequencies and higher intensity bouts. GRANT FUNDING: The Norwegian Research Council.