Zinc metabolism in endurance-trained volunteers during prolonged restriction of muscular activity and chronic hyperhydration

The objective of this study was to evaluate the effects of hypokinesia (HK) and fluid- and salt supplementation (FSS) on zinc metabolism in endurance-trained volunteers (ETV) for a period of 364 d. Thirty long-distance runners aged 22–25 yr with a peak V_O2 of 67 mL/min/kg with an average 13.8 km/d running distance were chosen as subjects. They were equally divided into three groups:

1.	Controls;
2.	HK subjects; and
3.	HK+FSS subjects.

Throughout the duration of the study, groups 2. and 3. were maintained under an average running distance of 2.7 km/d, whereas group 1. did not experience any modifications to their normal training routines and diets. Prior to and during the experimental period, plasma volume, hemoglobin, sodium, potasium, hematocrit, osmolality, and protein concentrations were determined along with the concentrations and urinary excretions of zinc, magnesium, calcium, and phosphorous. During the HK period, plasma concentrations of these minerals increased significantly when compared to the HK+FSS and control groups. The same was observed for the remaining parameters, which led us to conclude that during prolonged restriction of muscular activity, (PRMA) the body of the HK+FSS volunteers acquire an apparent tendency to retain zinc, whereas in the HK group the opposite is observed.