Breaking up prolonged sitting time with walking does not affect appetite or gut hormone concentrations but does induce an energy deficit and suppresses postprandial glycaemia in sedentary adults

Breaking up periods of prolonged sitting can negate harmful metabolic effects but the influence on appetite and gut hormones is not understood and is investigated in this study. Thirteen sedentary (7 female) participants undertook three 5-h trials in random order: (i) uninterrupted sitting (SIT), (ii) seated with 2-min bouts of light-intensity walking every 20 min (SIT + LA), and (iii) seated with 2-min bouts of moderate-intensity walking every 20 min (SIT + MA). A standardised test drink was provided at the start of each trial and an ad libitum pasta test meal provided at the end of each trial. Subjective appetite ratings and plasma acylated ghrelin, peptide YY, insulin, and glucose were measured at regular intervals. Area under the curve (AUC) was calculated for each variable. AUC values for appetite and gut hormone concentrations were unaffected in the activity breaks conditions compared with uninterrupted sitting (linear mixed modelling: p > 0.05). Glucose AUC was lower in SIT + MA than in SIT + LA (p = 0.004) and SIT (p = 0.055). There was no difference in absolute ad libitum energy intake between conditions (p > 0.05); however, relative energy intake was lower in SIT + LA (39%; p = 0.011) and SIT + MA (120%; p < 0.001) than in SIT. In conclusion, breaking up prolonged sitting does not alter appetite and gut hormone responses to a meal over a 5-h period. Increased energy expenditure from activity breaks could promote an energy deficit that is not compensated for in a subsequent meal

Effects of Heat Removal Through the Hand on Metabolism and Performance During Cycling Exercise in the Heat

OBJECTIVE: This two-part study tested the hypotheses that the use of a new cooling device, purported to extract heat from the body core through the palm of the hand, would (a) attenuate core temperature rise during submaximal exercise in the heat, thereby suppressing exercise-associated metabolic changes, and (b) facilitate a higher sustained workload, thus shortening the completion time of a time-trial performance test. METHODS: In Study 1, 8 male triathletes (age 27.9 ± 2.0 yrs, mass 77.2 ± 3.1 kg, VO2peak 59.0 ± 4.1 ml x min-1 x kg-1) cycled for 1 hr at the same absolute workload (~60% VO2peak) in a heated room (31.9 ± 0.1 °C, 24 ± 1% humidity) on two occasions counterbalanced for cooling (C) or noncooling (NC). In Study 2, 8 similar subjects (age 26.9 ± 2.0 yrs, mass 75.2 ± 3.7 kg, VO2peak 54.1 ± 3.1 ml x min-1 x kg-1) performed two 30-km cycling time-trial performance tests under the same conditions (CT, NCT). RESULTS: In Study 1, cooling attenuated the rise in tympanic temperature (TTY) (1.2 ± 0.2 vs. 1.8 ± 0.2 °C; p \u3c 0.01) and lowered mean oxygen consumption (VO2, 2.4 ± 0.1 vs. 2.7 ± 0.1 L x min-1; p \u3c 0.05) and blood lactate (1.7 ± 0.2 vs. 2.2 ± 0.2 mmol x L-1; p \u3c 0.01) during exercise. There were no significant differences in respiratory exchange ratio (RER), blood glucose, heart rate (HR), face temperature (TF), or back temperature (TB) between NC and C. In Study 2, time to complete 30 km was 6 ± 1% less with cooling than without cooling (60.9 ± 2.0 vs. 64.9 ± 2.6 min; p \u3c 0.01). During the last 20% of CT, subjects sustained a workload that was 14 ± 5% (p = 0.06) higher than NCT at the same TTY and HR. CONCLUSIONS: Heat extraction through the hand during cycle ergometer exercise in the heat can (a) lower TTY, lactate concentration, and VO2 during a submaximal set-workload test and (b) reduce the time it takes to complete a 30-km time-trial test