Exercise Energy Expenditure and Postprandial Lipemia in Girls

Keith Tolfrey; Alex Engstrom; Caoileann Murphy; Alice Thackray; Robert Weaver; Laura A. Barrett

Disclosures

Med Sci Sports Exerc. 2014;46(2):239-246. 

In This Article

Results

Responses to Treadmill Exercise

The treadmill responses for EX30 and EX60 are shown in Table 2. The girls exercised at an average intensity of 55% and 56% in EX30 and EX60, respectively (95% CI = –0.2% to 2.0%, ES = 0.30). As expected, the exercise EE (95% CI = 686 to 832 kJ, ES = 3.59) and absolute fat (95% CI = 8 to 13 g, ES = 2.42) and carbohydrate oxidation (95% CI = 16 to 28 g, ES = 1.95) were greater for EX60 compared with EX30. The only other difference in the exercise responses was a two-unit increase in RPE for EX60 compared with EX30 (95% CI = 1–2, ES = 0.69).

Plasma Volume Changes and Fasting [TAG] and [Glucose]

Average changes in plasma volume between the fasting and the 6-h postprandial samples were small between the conditions (CON = –1.1%, EX30 = –2.4%, EX60 = –1.8%, ES = 0.10–0.18). Therefore, the raw plasma [TAG] and [glucose] were not adjusted before statistical analyses. The fasting plasma [TAG] and [glucose] for each condition are displayed in Table 3. Fasting plasma [TAG] was lower after EX60 compared with CON (95% CI = –0.36 to 0.04 mmol·L−1, ES = 0.41) and EX30 (95% CI = –0.47 to 0.04 mmol·L−1, ES = 0.46), with no difference observed between EX30 and CON (95% CI = –0.22 to 0.34 mmol·L−1, ES = 0.13). However, all group mean concentrations were low (≤0.90 mmol·L−1). Differences in fasting plasma [glucose] between the three conditions were trivial (ES = 0.02–0.21).

Plasma [TAG] and [Glucose] in the Postprandial Period

Plasma [TAG] responses over the postprandial period for each experimental condition are shown in Figure 2. Differences in postprandial plasma [TAG] across the conditions were evident (main effect condition ES = 0.36, main effect time ES = 0.39, condition–time interaction ES = 0.10). The TAUC-TAG (Table 3) was lower after EX60 compared with CON (95% CI = –2.66 to –0.04 mmol·L−1 6 h, ES = 0.40) and EX30 (95% CI = –2.11 to 0.15 mmol·L−1 6 h, ES = 0.30); EX30 and CON were similar (95% CI = –1.44 to 0.71 mmol·L−1 6 h, ES = 0.10). Individual changes (delta) in TAUC-TAG between the exercise conditions and CON are shown in Figure 3. The reductions in TAUC-TAG after EX30 and EX60 were greater than changes in CON for 10 (~56%) and 12 (67%) girls, respectively. Of the 12 girls that responded to EX60, nine also experienced a lower postprandial TAG response after EX30 compared with CON (data not shown). The Pearson's product moment correlation for the individual changes in TAUC-TAG between EX30 and EX60 revealed a moderate effect (r = 0.57). The measured physical and physiological characteristics (Table 1) and exercise responses (Table 2) were not meaningfully correlated with the delta TAUC-TAG values for EX30 and EX60. The differences in iAUC-TAG between EX30 and the other two conditions were trivial (ES ≤ 0.15), and only a small effect was seen between EX60 and CON (ES = 0.30), although the 95% CI suggested this was unlikely to be meaningful (−1.26 to 0.33 mmol·L−1 6 h).

Figure 2.

Fasting (F) and postprandial plasma triacylglycerol (TAG) concentration for the control condition (CON) and the 30-min (EX30) and 60-min (EX60) intermittent exercise conditions (n = 18). Black rectangle signifies consumption of the breakfast meal (0800 h). Main effect for condition (ES = 0.36); main effect for time (ES = 0.39); condition–time interaction (ES = 0.10).

Figure 3.

Individual changes (delta) in the total area under the plasma triacylglycerol (TAG) concentration versus time curve (TAUC) between the 30-min (EX30) and the 60-min (EX60) intermittent exercise conditions and the rest control condition (CON): EX30 minus CON (A); EX60 minus CON (B). Participant data are ordered according to the size of the exercise-induced change in TAUC-TAG; thus, the order of the individual participants is not identical in A and B. A negative response indicates a reduction in TAUC-TAG in the exercise condition compared with CON.

There was no difference in postprandial plasma [glucose] across the conditions (main effect condition ES = 0.06, main effect time ES = 0.50, condition–time interaction ES = 0.09). Similarly, there was little difference in either TAUC-glucose (ES = 0.05–0.13) or iAUC-glucose (ES = 0.08–0.22) between the conditions.

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