Abstract
We investigated the effects of pre-meal exercise on postprandial lipemia (PPL) in individuals without injury (CON) and those with paraplegia (PARA). Participants completed two experimental trials in randomized crossover fashion consisting of seated rest (REST) or 60 min of aerobic arm ergometer exercise at 60% aerobic capacity (EX) prior to the consumption of a mixed-meal containing the stable isotope [U-<sup>13</sup>C]palmitate. Frequently sampled blood and breath samples collected during the 400 min postprandial period were analyzed for metabolite and hormone concentrations, [U-<sup>13</sup>C]palmitate enrichment, gas exchange, and <sup>13</sup>CO<sub>2</sub> enrichment. PARA tended to have higher postprandial total triglyceride (TG; 1,297 ± 217 vs 1,079 ± 269 μM) and endogenous TG concentrations and lower exogenous TG concentrations than CON, but these differences failed to reach significance. Compared to CON, PARA had lower rates of energy expenditure (EE; P=.004), total lipid oxidation (Lox; P=.021) and exogenous Lox (P=.006). Group differences in EE and Lox disappeared when these variables were normalized to lean body mass. Pre-meal EX had no effect on PPL in either group, but postprandial EE and total and endogenous Lox were greater in EX vs REST in both groups. Epinephrine and norepinephrine were blunted at all times in all conditions for PARA compared to CON (P=.006 and P=.008, respectively). The influence of exercise on Lox, but not TG concentration suggests that the benefits of this mode of exercise on are transient. Further studies should determine the sources of endogenous TG in SCI and the optimal mode, intensity, and timing of exercise to improve PPL in SCI.</p>