DIETARY-SODIUM INTAKE AND CHANGES IN PLASMA-VOLUME DURING SHORT-TERM EXERCISE TRAINING

This study was a retrospective examination of the relationship between estimated dietary sodium intake and training-induced changes in plasm a volume (PV). It was undertaken to explore one possible explanation f or the large individual differences in PV shifts accompanying 3 d of e ndurance cycling. Ten healthy males rode a stationary cycle for an ave rage time of 94 min/day at an average relative intensity of 68 % VO(2) max. During the training period, the subjects were allowed to eat a di et of their own choosing and dietary sodium intake was estimated from diet records. Plasma volume was determined before and after short-term training by dye dilution using Evan's blue dye. The mean increase in PV was 4.53 ml . kg body weight (BW)(-1) (i.e. 11 %). However, the ind ividual shifts in PV ranged from -1.44-14.30 ml . kg BW-1. The correla tion coefficient between estimated dietary sodium intake and changes i n PV was 0.81. It was concluded that dietary sodium intake was strongl y associated with training-induced shifts in PV and may be an influent ial factor in determining the magnitude of PV expansion derived from s hort-term exercise traiing. Further studies are needed, however, to ex amine this hypothesis.