Effect of water ingestion on cardiovascular and thermal responses to prolonged cycling and running in humans: a comparison.
The aim of this investigation was to examine the effect of water ingestion on physiological responses to prolonged cycling (CYC) and running (RUN). A group of 11 men with mean (SEM) maximal oxygen uptake (VO(2max)) 48.5 (1.8) ml x kg(-1) x min(-1) on a cycle-ergometer and 52.1 (2.2) ml x kg(-1) x min(-1) on a treadmill (P<0.01) exercised for 90 min on four occasions, twice on each ergometer, at 60% of mode specific VO(2max). No fluid was taken (D) in one trial on each ergometer, whereas 60% of fluid losses were replaced by drinking water in the other trial (W). In CYC, water ingestion attenuated the change in cardiac output (Delta Qc) and the reduction in stroke volume (DeltaSV) [DeltaSV: -22.7 (3.8) in D, -10.7 (2.9) ml x beat(-1) in W, P<0.01; : Delta Qc: -1.9 (0.5) in D, -0.2 (0.4) l x min(-1) in W at 85 min, P<0.01], but did not affect rectal temperature [T(re) at 90 min: 38.8 (0.1) degrees C in D, 38.7 (0.1) degrees C in W]. In contrast, fluid replacement reduced hyperthermia in RUN [T(re) at 90 min: 39.6 (0.2) in D, 39.1 (0.2) degrees C in W, P<0.01], and this was linked with a higher skin blood flow [RUN-W 88.9 (8.5), RUN-D 70.7 (8.4)%, P<0.05]. The Delta Qc and DeltaSV were also attenuated with water ingestion in this mode of exercise (P<0.05). It is concluded that water ingestion improves physiological function in both cycling and running, but that the underlying mechanism is different in the two modes of exercise.
Nassis
George P
GP
Department of Sport Medicine and Biology of Physical Activity, Faculty of Physical Education and Sport Science, University of Athens, 41, Ethnikis Antistassis Street, 172 37, Daphne, Greece.
Geladas
Nickos D
ND
D000328:Adult; D001642:Bicycling / Q000502:physiology*; D001783:Blood Flow Velocity; D001831:Body Temperature / Q000502:physiology*; D001835:Body Weight / Q000502:physiology; D002320:Cardiovascular Physiological Phenomena; D004326:Drinking / Q000502:physiology*; D005542:Forearm / Q000098:blood supply; D006801:Humans; D008297:Male; D012007:Rectum / Q000502:physiology; D012420:Running / Q000502:physiology*; D012881:Skin Temperature; D013546:Sweating / Q000502:physiology; D013997:Time Factors