Circulating XXXX and FFA during exercise: effect of reduction in plasma volume following exposure to simulated microgravity.

@entity1 @entity4962 @entity26 @entity880 @entity5934 @entity1718
We examined the relationship between changes in plasma volume (PV) following simulated weightlessness and the response of blood @entity880 (BL) and plasma free @entity1718 (FFA) during exercise. Ten healthy @entity1 (35-49 yr) performed 15 min of submaximal upright cycle ergoemetry at a workrate of 57% of pre-bed rest (BR) maximal @entity26 uptake before and after 10 d of continuous 6 degrees head-down BR. During exercise, @entity26 uptake (VO2) was measured to assure equivalent energy expenditure for pre-BR and post-BR workrate. Antecubital venous blood samples were collected at rest and during the last 30 s of exercise and analyzed for concentrations of BL and FFA, and hematocrit. Resting PV was measured pre-BR and post-BR with @entity5934 and total circulating BL and FFA were calculated as the product of PV and concentrations of BL and FFA, respectively. @entity4962 and FFA concentration during submaximal exercise were unchanged post-BR. During exercise, post-BR BL concentration of 2.9 mmol . L-1 was slightly greater (p less than 0.05) than pre-BR BL concentration of 2.5 mmol . L-1. However, as a result of a 17% reduction (p less than 0.05) in resting PV, total circulating BL during exercise was unchanged while total circulating FFA was reduced (p less than 0.05) post-BR. We conclude that the concentrations of BL and FFA during exercise following simulated weightlessness can be significantly altered by the reduction in PV.
