Tag: Christopher Chapman

Renal Hemodynamic Response to Oral Protein Loading during Prolonged Mild Hypohydration

Presenter: Sadie Holt − Human Physiology

Faculty Mentor(s): Dr. Christopher Chapman

Session: (In-Person) Poster Presentation

Hypohydration, a state of low body water, can occur due to inadequate fluid consumption or with sweating during heat stress. The kidneys regulate body water through multiple mechanisms including modulation of renal blood flow. It is not known if prolonged hypohydration alters the control of renal blood flow. Renal blood flow control can be probed using an oral protein load, a stimulus that increases renal blood flow within 1-3 hours. We tested the hypothesis that prolonged mild hypohydration attenuates oral protein loading-induced increases in renal blood flow compared to a hydrated state (i.e., euhydrated). Eight healthy adults (5 females) arrived at the lab after 24 hours of fluid deprivation (HYPO) or when euhydrated (EUHY). Subjects ingested a whey protein beverage to stimulate increases in renal blood flow. Doppler ultrasonography was used to estimate renal blood flow from blood velocity in the renal and segmental arteries. Data were summarized as the peak increase in renal blood velocity. A mild hypohydration was confirmed by greater reductions in body mass in HYPO vs. EUHY (HYPO: -2.2±0.5%; EUHY: -0.3±0.7%, P=0.001). There were no differences between conditions in the peak increase in renal (HYPO: +5.6±3.8 cm/s; EUHY: +4.8±3.3 cm/s, P=0.54) and segmental (HYPO: +4.4±4.7 cm/s; EUHY: +3.4±4.0 cm/s, P=0.43) artery blood velocities. These findings indicate that prolonged mild hypohydration does not alter the kidneys’ ability to increase renal blood flow.

Prolonged mild hypohydration reduces handgrip strength in females

Presenter: Shaun Brazelton − Human Physiology

Faculty Mentor(s): Christopher Chapman

(In-Person) Poster Presentation 

An overwhelming majority of studies pertaining to the effects of hypohydration, a state of low body water, on muscular strength has been performed in males. One study recently reported that passive heat-stress induced hypohydration reduces upper-body muscular strength in females. It remains unknown whether hypohydration independent of heat stress elicits similar effects in females. We tested the hypothesis that maximal voluntary isometric handgrip strength is reduced in females following prolonged mild hypohydration compared to a hydrated state (i.e., euhydrated). Six healthy, physically active females performed two randomized experimental trials following either 24 hours of fluid deprivation (HYPO) or when euhydrated (EUHY). Subjects performed three attempts of maximal voluntary isometric handgrip strength with one minute rest between sets. Handgrip strength was evaluated as the maximum force produced and as the mean value of the three attempts. There were greater reductions in body mass in HYPO vs. EUHY (EUHY: -0.6±0.6%; HYPO: -2.2±0.6%, P=0.013), indicating that the 24-hour protocol induced a mild hypohydration in HYPO. Maximal handgrip strength was reduced in HYPO compared to EUHY (EUHY: 31±3 kg; HYPO: 28±5 kg, P=0.067) and there was a trend toward reduced mean handgrip strength (EUHY: 29±4 kg; HYPO: 26±6 kg, P=0.172). These preliminary findings suggest that prolonged hypohydration caused by inadequate fluid consumption reduces handgrip strength in females.