Date of Award

Summer 8-2023

Document Type


Degree Name

Master of Science (MS)


Human Movement Sciences


Exercise Science

Committee Director

Patrick Wilson

Committee Member

Zachary Sievert

Committee Member

J. David Branch


Previous research has shown that food particle size affects gastric processing. For example, food particles greater than 3 mm may delay gastric emptying under certain conditions. Delays in gastric emptying can be problematic during aerobic exercise, leading to nausea, bloating, fullness, and other gastrointestinal (GI) symptoms. In some cases, symptoms can be severe enough to negatively affect athletic performance. This study investigated the effects of manipulating chewing duration of carbohydrate sports bars on GI discomfort, physiological responses, and performance during endurance running. This crossover study recruited 12 male runners (age: 36.4 ± 7.2 years, VO2peak: 57.2 ± 4.7 ml/kg/min) who completed 20 (20CHEW) and 40 (40CHEW) mastication cycle treatments in a counterbalanced order. The 40CHEW treatment and 20CHEW treatment followed the same testing parameters. Participants attended three testing sessions. The initial visit required a VO2peak test, a 10-minute familiarization run at 60% VO2peak, and a performance test (10 minutes at 90% VO2peak, followed by time to exhaustion at 100% VO2peak). All testing was conducted on a treadmill. The second visit consisted of a 60-minute run at 60% VO2peak, followed by the same performance test. Each participant was fed 45 g of a sports bar in 9-g servings 30 minutes before running. During the 40CHEW trial, participants ingested 27 g of the sports bar in 9-g servings at three time points; each feeding was chewed in 40 masticatory cycles, at 1 chew per second. During the 20CHEW trial, participants performed the same testing, except the bar was chewed in 20 masticatory cycles at a rate of 1 chew per second.


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