Date of Award

Summer 2021

Document Type


Degree Name

Doctor of Philosophy (PhD)


Human Movement Sciences


Applied Kinesiology

Committee Director

Patrick Wilson

Committee Member

Laura Hill

Committee Member

Gena Gerstner

Committee Member

Hayley Russell


Gastrointestinal (GI) symptoms, such as nausea and gas, are common problems for athletes in endurance sport. There is considerable evidence that psychological factors influence GI function, but little research has evaluated this in the context of exercise-induced GI symptoms. The overall purpose of this dissertation was to explore the role of psychological factors in the incidence and management of GI symptoms during endurance running. Study 1 assessed associations between several psychological factors, GI symptoms, and nutrition intake before and during runs. Study 2 evaluated the effects of daily breathing interventions on GI symptoms, psychological factors, and heart rate variability (HRV) in runners.

Eighty-two runners were recruited for study 1. They tracked information about their running, GI symptoms, and nutrition intake before and during runs for seven days, and completed a survey containing psychological questionnaires. Correlational analyses were used to quantify associations between 1) GI symptoms and psychological factors and 2) psychological factors and nutrition intake. A measure of GI-specific anxiety had statistically significant correlations with GI symptom burden during runs (Spearman’s rho = 0.32 – 0.38), which remained significant (although somewhat attenuated) after adjusting for potential confounders. However, GI symptom burden did not have statistically significant correlations with measures of stress, trait anxiety, or body vigilance. There were also no significant negative associations between psychological factors and nutrition intake.

Fifty-six runners with at least mild levels of anxiety and previous experiences with GI symptoms during running were recruited for study 2 and completed baseline measurements to quantify levels of several psychological factors, GI symptom burden, and resting HRV. They were then randomly allocated to slow deep breathing with breath counting (SLOWBC), normal breathing with breath counting (NORMALBC), or control groups. Participants in SLOWBC and NORMALBC were asked to complete daily, 5-minute breathing sessions for four weeks. Additional measurements were completed at the midpoint and during the final week of the intervention. The results generally did not support a treatment effect from either breathing intervention compared to the control group, except for a group x time interaction for anxiety in a per-protocol analysis. Follow-up analyses suggested anxiety tended to decrease over time in the breathing groups, and participants who found the breathing sessions more engaging tended to have larger reductions in anxiety levels. Overall, it seems more intensive breathing- and/or mindfulness-based interventions are required to substantially influence GI symptoms, stress, GI-specific anxiety, mindfulness, and HRV in runners with elevated levels of anxiety and GI symptom burden.


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