Abstract
The beneficial effects of beetroot juice supplementation (BJS) have been tested during cycling, walking, and running. The purpose of the present study was to investigate whether BJS can also improve performance in swimmers. Fourteen moderately trained male master swimmers were recruited and underwent two incremental swimming tests randomly assigned in a pool during which workload, oxygen uptake (VO2), carbon dioxide production (VCO2), pulmonary ventilation (VE), and aerobic energy cost (AEC) of swimming were measured. One was a control swimming test (CSW) and the other a swimming test after six days of BJS (0.5l/day organic beetroot juice containing about 5.5 mmol of NO3−). Results show that workload at anaerobic threshold was significantly increased by BJS as compared to the CSW test (6.3 ± 1 and 6.7 ± 1.1 kg during the CSW and the BJS test respectively). Moreover, AEC was significantly reduced during the BJS test (1.9 ± 0.5 during the SW test vs. 1.7 ± 0.3 kcal·kg−1·h−1 during the BJS test). The other variables lacked a statistically significant effect with BJS. The present investigation provides evidence that BJS positively affects performance of swimmers as it reduces the AEC and increases the workload at anaerobic threshold.
Highlights
A diet rich in vegetables has been found to have a beneficial impact on several body functions [1].These effects may, in part, be attributable to the high inorganic nitrate (NO3−) content of vegetables.NO3− can be reduced to nitrite (NO2−) and in turn to nitric oxide (NO), which affects hemodynamics and muscle metabolic functions [2,3]
The upper panel demonstrates that workload at anaerobic threshold (AT) was significantly increased by beetroot juice supplementation as compared to the control swimming (CSW) test
Workload reached at AT was 6.3 ± 1.0 and 6.7 ± 1.1 kg during the CSW and the beetroot juice supplementation (BJS) test respectively
Summary
NO3− can be reduced to nitrite (NO2−) and in turn to nitric oxide (NO), which affects hemodynamics and muscle metabolic functions [2,3] In this regard, recent evidence suggests that beetroot juice supplementation may positively impact the physiological responses to exercise. A reduction in O2 cost of exercise has been demonstrated as well as improved performance, even though the precise mechanism through which dietary nitrate supplementation operates is not yet fully understood [4,5,6] It appears that these effects are related to NO2− and NO-mediated enhancements of muscle contractile function, and/or mitochondrial efficiency and/or enhanced muscle blood flow [4,5,6,7,8,9,10]. There is evidence that elevations of NO improves muscle metabolism, thereby modulating the ATP cost of force production [9,10]
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