Breaking Prolonged Sitting With Different Physical Activity Protocols And Metabolic Risk

OBJECTIVE: To investigate the effects of breaking prolonged sitting with different physical activity protocols on metabolic risk in sedentary subjects. METHODS: Seven sedentary adult healthy males (BMI: 24.9±5.0 Kg/m2) underwent four 24-h interventions in a randomized cross-over design: SIT-subjects sat for 9h; STAND-subjects stood for 15 min every 30 min during 9h of sitting; MVPA-subjects performed a 30-min moderate-intensity exercise bout (~50% VO2max), after which they sat for the remaining 8h; MVPA+STAND-subjects performed a 30-min moderate-intensity exercise bout and subsequently stood for 15-min every 30 min during the remaining 8h of sitting. On each trial, subjects were assessed for 24-h energy expenditure (Actiheart monitor), ate three standardized meals (55% CHO, 30% fat, 15% protein), and stayed overnight. Blood samples were collected 10 min before, and 30, 60, 120 and 180 min after meals for the postprandial response assessment of plasma glucose, insulin, and lipids (defined as the 9-h cumulative area under the curve). RESULTS: 24-h energy expenditure was lower during SIT (1937±435Kcal) and STAND (1945±425 Kcal) when compared with MVPA (2692±189 Kcal) and MVPA+STAND (2565±589 Kcal) (p<0.05, between-conditions). A tendency towards a higher glucose response was observed during SIT (3075±312 mmol/L) when compared with STAND (2900±174 mmol/L; p=0.07) and MVPA+STAND (2899±180 mmol/L; p=0.07), but not with MVPA (2970±181 mmol/L; p=0.2). A higher insulin response was observed during SIT (206975±109164 pmol/L) when compared with MVPA+STAND (163536±74553 pmol/L; p=0.05), with STAND (183218± 80656 pmol/L; p=0.13) and MVPA (181894±97431 pmol/L; p=0.12), although the latter two comparisons did not reach significance. A lower LDL-chol response was observed during MVPA (1395±573 mmol/L) when compared with SIT (1519±661 mmol/L; p=0.05). CONCLUSION: Preliminary results suggest that breaking sitting with intermittent standing bouts led to lower glucose post-prandial responses regardless of MVPA. On the other hand, a moderate exercise bout led to lower LDL post-prandial responses, regardless of breaking sitting. Finally, both intermittent standing and MVPA led to lower post-prandial insulin responses, although only the combination of the two strategies led to a significantly improved response.