Sedentary Behavior Impact Cardiometabolic Risk Factors
Ten participants (four men and six women) completed the study. Participants were relatively young (mean ± SD age, 25.2 ± 5.7 yr) and lean (mean ± SD body mass index (BMI), 24.9 ± 4.3 kg·m) (Table 1).
Under the sedentary condition, participants significantly decreased MET-hours (mean Δ, −3.5 MET·h; 95% CI, −4.9 to −2.5), time in MVPA (mean Δ, −52.7 min; 95% CI, −65.8 to −39.6), time in light-intensity activity (mean Δ, −87.6 min; 95% CI, −120.5 to −54.8), and guideline minutes (mean Δ, −41.7 min; 95% CI, −54.4 to-29.1). Total sedentary time (mean Δ, 14.9%; 95% CI, 10.2 to 19.6) and time in sedentary bouts longer than 20, 30, and 60 min significantly increased, whereas the rate of breaks from sedentary time was significantly reduced (Table 2). According to both the activPAL monitor and the Omron pedometer, step count significantly decreased after the sedentary condition (activPAL: mean Δ, −6850.2; 95% CI, −8578.3 to-5122.1; Omron: mean Δ, −6522.9; 95% CI, −8042.1 to −5003.8). Although the decrease in Omron pedometer step count was slightly less, the Omron pedometer estimate was not significantly different from the activPAL estimate. The purpose of the Omron pedometer was only to facilitate condition compliance by providing participants real-time feedback on behavior; thus, all statistical analyses and step data presented in tables and discussed are from the activPAL monitor. Activity and sedentary behavior variables for the baseline period and the sedentary condition are reported in Table 2.
According to diet recalls, total energy [baseline (mean, 1672.7; 95% CI, 1214.6–2130.8); sedentary (mean, 1671.8; 95% CI, 1146.5–2197.0)] and macronutrient content [baseline: CHO (mean, 45.9%; 95% CI, 34.0–57.9), fat (mean, 35.5%; 95% CI, 22.5–48.5), protein (mean, 18.5%; 95% CI, 10.2–26.9); sedentary: CHO (mean, 40.7%; 95% CI, 27.3–54.2), fat (mean, 39.2%; 95% CI, 25.2 –53.3), protein (mean, 20.0%; 95% CI, 12.1–27.9) ] did not differ during the baseline period and the sedentary condition.
Glucose and insulin response. After the sedentary condition, fasting glucose and insulin concentrations did not change from baseline. Glucose concentrations also remained stable in response to glucose load (OGTT). Conversely, 2-h plasma insulin (mean Δ, 38.8 μU·mL; 95% CI, 10.9–66.8) and insulin-AUC (mean Δ, 3074.1 μU·mL per 120 min; 95% CI, 526.0–5622.3) were significantly elevated in response to glucose load (Fig. 1), suggesting that more insulin was needed to dispose of the same amount of glucose. This resulted in a significant 17.2% decrease in C-ISI. Cardiometabolic variables for the baseline period and the sedentary condition are reported in Table 2 and illustrated in Figure 1.
(Enlarge Image)
Figure 1.
OGTT glucose and insulin responses. Mean minute values for glucose (top left) and mean glucose-AUC (top right) show an elevated, but not significant, increase in glucose response after the sedentary condition. Mean minute values for insulin (bottom left) and mean insulin-AUC (bottom right) show a significant increase in 2-h plasma insulin and insulin-AUC after the sedentary condition compared to baseline. *Significantly different from baseline (P < 0.05).
Body Mass, BMI, Waist Circumference, and Fasting Lipids. There were no significant differences in any fasting lipid (TG, total cholesterol, HDL, and LDL) values after the sedentary condition. Body mass, BMI, and waist circumference did not change from baseline to postsedentary condition (Table 2).
Linear regression was used to evaluate the association between change in activity and sedentary behavior variables and change in insulin action. Because 2-h plasma insulin, insulin-AUC, and C-ISI were the only cardiometabolic variables to significantly change after the sedentary condition, data are presented for these variables only. Change in 2-h plasma insulin was negatively associated with change in percent time in light-intensity activity (r = −0.62, P < 0.05) and positively associated with change in time in sedentary bouts longer than 30 min (r = 0.82, P < 0.01) and 60 min (r = 0.83, P < 0.01). When change in time in MVPA was included in the models, the significant associations of time in sedentary bouts longer than 30 and 60 min persisted (P < 0.05), whereas the association with percent time in light-intensity activity was slightly attenuated (P = 0.09). Although not significant, changes in total sedentary time (r = 0.57, P = 0.09) and break rate (−0.57, P = 0.09) were moderately correlated with change in 2-h plasma insulin. Changes in insulin-AUC and C-ISI were not associated with any activity or sedentary behavior variable (Table 3).
Results
Ten participants (four men and six women) completed the study. Participants were relatively young (mean ± SD age, 25.2 ± 5.7 yr) and lean (mean ± SD body mass index (BMI), 24.9 ± 4.3 kg·m) (Table 1).
Activity and Sedentary Behavior Variables
Under the sedentary condition, participants significantly decreased MET-hours (mean Δ, −3.5 MET·h; 95% CI, −4.9 to −2.5), time in MVPA (mean Δ, −52.7 min; 95% CI, −65.8 to −39.6), time in light-intensity activity (mean Δ, −87.6 min; 95% CI, −120.5 to −54.8), and guideline minutes (mean Δ, −41.7 min; 95% CI, −54.4 to-29.1). Total sedentary time (mean Δ, 14.9%; 95% CI, 10.2 to 19.6) and time in sedentary bouts longer than 20, 30, and 60 min significantly increased, whereas the rate of breaks from sedentary time was significantly reduced (Table 2). According to both the activPAL monitor and the Omron pedometer, step count significantly decreased after the sedentary condition (activPAL: mean Δ, −6850.2; 95% CI, −8578.3 to-5122.1; Omron: mean Δ, −6522.9; 95% CI, −8042.1 to −5003.8). Although the decrease in Omron pedometer step count was slightly less, the Omron pedometer estimate was not significantly different from the activPAL estimate. The purpose of the Omron pedometer was only to facilitate condition compliance by providing participants real-time feedback on behavior; thus, all statistical analyses and step data presented in tables and discussed are from the activPAL monitor. Activity and sedentary behavior variables for the baseline period and the sedentary condition are reported in Table 2.
Dietary Assessment
According to diet recalls, total energy [baseline (mean, 1672.7; 95% CI, 1214.6–2130.8); sedentary (mean, 1671.8; 95% CI, 1146.5–2197.0)] and macronutrient content [baseline: CHO (mean, 45.9%; 95% CI, 34.0–57.9), fat (mean, 35.5%; 95% CI, 22.5–48.5), protein (mean, 18.5%; 95% CI, 10.2–26.9); sedentary: CHO (mean, 40.7%; 95% CI, 27.3–54.2), fat (mean, 39.2%; 95% CI, 25.2 –53.3), protein (mean, 20.0%; 95% CI, 12.1–27.9) ] did not differ during the baseline period and the sedentary condition.
Markers of Cardiometabolic Health
Glucose and insulin response. After the sedentary condition, fasting glucose and insulin concentrations did not change from baseline. Glucose concentrations also remained stable in response to glucose load (OGTT). Conversely, 2-h plasma insulin (mean Δ, 38.8 μU·mL; 95% CI, 10.9–66.8) and insulin-AUC (mean Δ, 3074.1 μU·mL per 120 min; 95% CI, 526.0–5622.3) were significantly elevated in response to glucose load (Fig. 1), suggesting that more insulin was needed to dispose of the same amount of glucose. This resulted in a significant 17.2% decrease in C-ISI. Cardiometabolic variables for the baseline period and the sedentary condition are reported in Table 2 and illustrated in Figure 1.
(Enlarge Image)
Figure 1.
OGTT glucose and insulin responses. Mean minute values for glucose (top left) and mean glucose-AUC (top right) show an elevated, but not significant, increase in glucose response after the sedentary condition. Mean minute values for insulin (bottom left) and mean insulin-AUC (bottom right) show a significant increase in 2-h plasma insulin and insulin-AUC after the sedentary condition compared to baseline. *Significantly different from baseline (P < 0.05).
Body Mass, BMI, Waist Circumference, and Fasting Lipids. There were no significant differences in any fasting lipid (TG, total cholesterol, HDL, and LDL) values after the sedentary condition. Body mass, BMI, and waist circumference did not change from baseline to postsedentary condition (Table 2).
Secondary Analyses
Linear regression was used to evaluate the association between change in activity and sedentary behavior variables and change in insulin action. Because 2-h plasma insulin, insulin-AUC, and C-ISI were the only cardiometabolic variables to significantly change after the sedentary condition, data are presented for these variables only. Change in 2-h plasma insulin was negatively associated with change in percent time in light-intensity activity (r = −0.62, P < 0.05) and positively associated with change in time in sedentary bouts longer than 30 min (r = 0.82, P < 0.01) and 60 min (r = 0.83, P < 0.01). When change in time in MVPA was included in the models, the significant associations of time in sedentary bouts longer than 30 and 60 min persisted (P < 0.05), whereas the association with percent time in light-intensity activity was slightly attenuated (P = 0.09). Although not significant, changes in total sedentary time (r = 0.57, P = 0.09) and break rate (−0.57, P = 0.09) were moderately correlated with change in 2-h plasma insulin. Changes in insulin-AUC and C-ISI were not associated with any activity or sedentary behavior variable (Table 3).
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