The Effects of High‐Intensity Treadmill‐Running on Gastric Emptying and Heart Rate Variability in a Rodent Model

Abstract

PURPOSEExercise is well known for the beneficial effects it provides to organs and systems of the body. Proper and consistent exercise has been shown to improve cardiovascular and neural function, reduce adipose tissue, and lower the risk of developing certain metabolic disorders. Patients suffering from gastrointestinal (GI) dysfunction are frequently prescribed exercise to improve their symptoms. Yet, exercise has also been shown to provoke GI disturbances including diarrhea, abdominal pain, and gastroesophageal reflux. These GI disturbances commonly occur after bouts of prolonged or high‐intensity exercise, and the GI disturbance frequency is twice as high during running compared to other endurance sports. The effect of exercise on the upper‐GI tract remains controversial; studies have reported increases, decreases, and no changes in gastric emptying (GE) rate following running. We evaluated the effects of high‐intensity treadmill‐training on GE rate in rats. We hypothesized that exercise will contribute to increased vagal tone leading to an increase in GE rate. By developing an understanding of the relationship between exercise and GI function, exercise may be medicine in treating a number of GI health dysfunctions (e.g. gastroparesis).METHODSIn this study, we evaluated the effects of high‐intensity treadmill‐running on GE rate and heart rate variability (HRV) in Male Wistar rats. Rats (n = 8) ran on a treadmill at 23.0m/min, five days/week, for 4‐weeks; control rat (n = 8) were placed on the powered off treadmill. For GE measurements, fasted rats were placed in collection chambers, baseline air measurements collected, and rats received 1g of pancake containing 5μL of the stable isotope [13C]‐octanoic acid. Exhaled breath was collected and analyzed to determine the [13C]‐ to [12C]‐CO2 ratio. HRV was assessed at baseline and at the conclusion of the study to compare pre‐exercise to post‐exercise differences between exercise and control rats' autonomic activity.RESULTSAfter 4‐weeks, anthropometric factors remained similar between exercise and control: mean energy intake (29.92 ± 0.44 vs 29.59 ± 0.53kcal/100g/day; p>0.05), body mass (85% increase; 325.83 ± 3.30 vs. 330.28 ± 3.48g; p>0.05), food intake (24.38 ± 0.29 vs. 24.48 ± 0.35g; p>0.05). Cumulative percent recovery of the administered [13C]‐octanoic acid dose was reduced in exercise vs control 6‐hours following GE testing (11.70 ± 0.83 vs 13.29 ± 0.60; p>0.05). Peak fractional dose per hour of 13CO2 during the breath test was the same between groups (6.96 ± 0.89 vs 7.61 ± 0.40; p>0.05), but there was a rapid reduction of [13C] values following peak over several time points of the exercise group. HRV data is inconclusive.CONCLUSIONWe previously validated moderate‐intensity treadmill running has no significant effect on gastric emptying. By increasing the intensity of running, we found no significant difference in GE rate in the exercise vs control groups. We believe the duration of the exercise was too acute to elicit physiological changes to gastric emptying. However, further investigation may reveal neuronal changes prior to the physiological alterations.Support or Funding InformationGettysburg College Start‐up FundsThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.