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Date of Graduation
5-9-2024
Semester of Graduation
Spring
Degree Name
Master of Science (MS)
Department
Department of Kinesiology
Second Advisor
Stephanie P. Kurti-Luden
Third Advisor
Michael Saunders
Abstract
Exercise performance is impaired by dehydration and, separately, can be negatively impacted in scenarios where there is pulmonary expiratory flow limitation (EFL). Interestingly, there may be an interaction between dehydration and pulmonary function. Previous work has suggested that resting pulmonary function is impaired by mild dehydration through the collapse of small/unsupported airways. Therefore, the aim of this study was to determine the effect of fluid restriction on EFL presence and other pulmonary dynamics such as operating lung volumes. METHODS: 12 healthy active adults (8 M and 4 F) aged 20 ± 2 years performed a VO2Peak test on a cycle ergometer during three separate trials, one preliminary and two experimental. The experimental trials consisted of subjects being euhydrated (HYD) and fluid restricted (FR), in a randomly counterbalanced order. Standardization procedures were implemented 24 hours before each trial. For fluid restriction, participants were instructed to avoid fluid intake as well as any food with >30% water content. Nude body mass and urine specific gravity with additional supplementary measures were used to verify hydration status. Maximum flow-volume loops were performed before and after exercise with inspiratory capacity maneuvers performed during exercise using a metabolic cart to measure pulmonary function. RESULTS: Body mass (kg) significantly decreased in the fluid restricted trial (70.16 ± 12.90 kg compared to the hydrated trial (71.12 ± 13.04 kg) and urine specific gravity significantly increased in the fluid restricted trial (1.03 ± 0.00) compared to the hydrated trial (1.01 ± 0.01). Hydration status had no apparent effect on presence or severity of EFL or operating lung volumes. However, post-exercise forced vital capacity (FVC) (4.53 ± 1.08 L) and peak expiratory flow (PEF) (8.89 ± 1.61 L) were attenuated when fluid was restricted. Additionally, fluid restriction lowered tidal volume (VT) (1.93 ± 0.26 L) at 150 W, the last common staged reached by all participants, along with VTmax (2.42 ± 0.69 L). Respiratory rate (RR) increased under the same conditions (FR: 34.42 ± 0.35 breaths/min; 45.58 ± 8.48 breaths/min). Dyspnea descriptors selected on the Multiple Dyspnea Profile following exercise were significantly higher with FR (3.4 ± 1.2) compared to HYD (2.6 ± 1.1). CONCLUSIONS: While hydration status had no impact on EFL presence and severity or operating lung volumes. Similarly, to previous studies though, small airways seem to still be affected by fluid restriction during exercise as VT was reduced and RR increased in order to compensate to maintain ventilation. It is worth noting that the 24-hr fluid restriction protocol employed here led to relatively small changes in hydration, and when coupled with the observations described herein, indicates that more marked dehydration could relay serious detriments to pulmonary physiology and consequential physical performance outcomes.
