Abstract
Background: Prolonged evening sedentary behaviour may increase cardiovascular disease risk through elevated postprandial triglyceride concentrations. Resistance exercises are a relatively novel method of interrupting prolonged sitting in the laboratory setting, and there is limited research on their effect on the evening triglyceride response.
Objective: To determine whether breaking up prolonged evening sitting with short bouts of bodyweight resistance exercises reduces the postprandial triglyceride response in adults and whether this effect differs by body mass index.
Methods: A randomised crossover study was conducted at the Department of Human Nutrition, University of Otago in Dunedin, New Zealand between March and September 2021. Thirty adults (healthy weight 18.5 – 24.9 kg · m−2, n = 10; overweight 25.0 – 29.9 kg · m−2, n = 10; obese ≥30.0 kg · m−2, n = 10) with a mean ± SD age of 25.3 ± 5.5 years underwent the following four-hour conditions on two separate evenings (with a 6 – 13 day washout period): 1) uninterrupted sitting and 2) sitting interrupted with three-minute bouts of resistance exercises (half squats, calf raises, and single-leg knee raises with gluteal contractions) every 30 minutes. Standardised mixed-macronutrient meals (dinner and dessert) were consumed at 1800 h and 2000 h. Venous blood samples were collected hourly and at 30- and 45- minutes after meals. Triglyceride total and baseline-adjusted area under the curve were compared between conditions.
Results: Overall, compared to uninterrupted sitting, regular activity breaks did not significantly impact triglyceride total area under the curve (mean difference 7.0 mmol · L−1 · 4 h; 95% CI −10.0, 24.5 mmol · L−1 · 4 h; p = 0.433) or baseline-adjusted total area under the curve (mean difference 5.7 mmol · L−1 · 4 h; 95% CI −11.7, 23.0 mmol · L−1 · 4 h; p = 0.520). The interaction between body mass index and intervention was also not statistically significant; however, regular activity breaks respectively increased triglyceride total area under the curve and baseline-adjusted total area under the curve by 7.9% and 2.2% in the healthy weight group, 1.2% and 6.1% in the obese group, and respectively decreased total area under the curve and baseline-adjusted total area under the curve by 1.5% and 3.6% in the overweight group.
Conclusion: Interrupting prolonged evening sitting with brief bouts of bodyweight resistance exercises is unlikely to result in meaningful benefits to the postprandial triglyceride response in adults, regardless of body mass index. Although not the focus of this thesis, this intervention attenuated postprandial glucose and insulin responses.