The Effects Of A Novel Fluid-Loading Strategy On Cardiovascular Responses To Orthostatic Stress: Applications For Spaceflight?
- Paper number
IAC-07-A1.3.-A1.4.01
- Author
Mr. Chris Easton, University of Glasgow, United Kingdom
- Coauthor
Dr. Alyson Calder, United Kingdom
- Coauthor
Dr. Franck Prior, United Kingdom
- Coauthor
Ms. Sarah Dobinson, University of Glasgow, United Kingdom
- Coauthor
Ms. Rebecca l'Ansson, University of Glasgow, United Kingdom
- Coauthor
Ms. Rhona MacGregor, University of Glasgow, United Kingdom
- Coauthor
Mr. Yaser Mohammad, University of Glasgow, United Kingdom
- Coauthor
Mr. David Kingsmore, United Kingdom
- Coauthor
Dr. Yannis Pitsiladis, University of Glasgow, United Kingdom
- Year
2007
- Abstract
Astronauts experience large reductions in body mass (BM), total body water (TBW), plasma volume (PV) and skeletal muscle mass during spaceflight which can compromise cardiovascular and thermoregulatory function and lead to orthostatic intolerance on return to Earth, and as yet no effective countermeasure exists (Lane & Feeback, Nutrition 18: 820-828, 2002). However, a novel fluid loading strategy combining creatine (Cr) and glycerol (Gly) results in a significant increase in BM, TBW and PV (Easton et al. Int J Sport Nutr Exerc Metabol 17: 70-91, 2007), which may be of clinical significance to astronauts during and after space flight.
PURPOSE: To examine the effects of combined Cr and Gly supplementation on the cardiovascular responses to postural change.
METHODS: Seven euhydrated healthy male subjects underwent 2 tilt table experiments (baseline and pre-supplementation) 1 week apart during which they lay supine (0 o) for 30 min before being tilted to the head down position (-6 o) for 30 min and head up position (70 o) for 30 min to simulate the fluid shifts and reductions in PV that occur during exposure to, and return from microgravity. Following this, subjects supplemented with Cr (20g/day) and Gly (2g/kg BM/day) for 7 days before undergoing a final post-supplementation tilt table trial. Heart rate (HR) and blood pressure (BP) were recorded at 5 min intervals and venous blood samples drawn every 10 min. RESULTS: Post Cr/Gly supplementation, BM increased (mean ± s.d.) by 0.8 ± 0.2 kg, TBW by 0.7 ± 0.2 L and PV by 2.6 ± 2.0%. PV was reduced 30 min after tilting by approximately 2.5% (–6 o) and 8.0% (70 o), with no difference between trials ( P=0.96). Mean arterial BP remained relatively stable throughout the tilt test but was significantly higher following Cr/Gly supplementation throughout ( P=0.05). HR increased significantly upon tilting to 70 o with no difference between trials ( P=0.89). 1 subject became hypotensive and presyncopal after 25 min in the 70 o position during the baseline and pre-supplementation trials yet completed the full 30 min in the post-supplementation trial.
CONCLUSIONS: Cr/Gly supplementation resulted in a significant increase in BM, TBW and PV resulting in an increased BP during postural change and a reduced incidence of orthostatic hypotension and presyncope. These results suggest that the increased central blood volume resulting from Cr/Gly supplementation coupled with the potential anabolic effects of Cr on skeletal muscle may provide astronauts with an effective countermeasure to combat plasma volume reduction during space travel and orthostatic intolerance on return to Earth.
- Abstract document