Baro–Reflex Sensitivity is Augmented more in Athletes than in Sickle Cell Anaemia Subjects Following Vitamin C Supplementation

Abstract

This study examined the effect of chronic, low dose vitamin C supplementation on the baro-reflex sensitivity (BRS), rate - pressure product (RPP) and Barach energy index (BEI) in 21 male athletes and sickle cell anaemia subjects (SCAS). Arterial blood pressure and heart rate were recorded in the supine position and immediately on assumption of the upright position before and after oral vitamin C supplementation at a dose of 300mg/day for 6 weeks. BRS, RPP and BEI were determined from heart rate and blood pressure measurements. Change in posture significantly caused fall in MABP in the two groups of subjects. However, HR (P<0.05), RPP (P<0.001) and BEI (P<0.01) were raised significantly in the two groups. Vitamin C decreased the resting MABP significantly (P<0.05) in the two groups. Vitamin C also caused a significant rise in HR (P<0.05), RPP (P<0.01) and BEI (P<0.05) in the SCAS, while it caused a slight fall in RPP and BEI in the athletes. Nevertheless, the changes observed following change in posture alone were much compared to changes observed following Vitamin C supplementation only. But after 6 – week vitamin C supplementation, change in posture caused a less significant fall in SCAS MABP (P<0.05) and slight fall in athletes. On the other hand, there were greater significant rise in BRS, RPP and BEI in athletes than in SCAS P<0.001 in all the cases. In conclusion, low – dose, oral, chronic vitamin C supplementation augments BRS, RPP and BEI more in athletes than in SCAS following change in posture. Vitamin C also normalises cardiac and autonomic responses to change in posture in SCAS. The higher RPP and BEI produced may indicate earlier setting – in of fatigue than expected in athletes, limiting their performance and/or preventing any tissue damage.

Keywords: Chronic, low-dose, vitamin C, baro-reflex sensitivity, rate-pressure product, change in posture, athletes, sickle cell anaemia, Barach energy index.

Nigerian Journal of Health and Biomedical Sciences Vol. 7 (2) 2008: pp. 1-8