[Purpose]
The effect of acute nitrate supplementation on muscle fatigue is largely unknown. This study aimed to evaluate the effect of acute nitrate supplementation on muscle fatigue.
[Methods]
Thirty-five recreationally active subjects consumed 140 ml of beetroot (BR) juice (nitrate: 8 mmol·d
-1
) or placebo (PL) 12 and 2.5 hours before two exercise sessions. Peak torque was measured during 50 repetitions, at maximal effort, and during concentric knee extensions at 90°·s
-1
. Blood pressure (BP) was recorded pre- and post-exercise.
[Results]
Peak torque, maximum work, rate of fatigue, and rate of work fatigue were similar between the BR and PL conditions. Post-exercise diastolic BP (BR: 67.2 ± 9.8 vs. PL: 64.5 ± 7.9 mmHg,
p
< 0.05) and mean arterial pressure (BR: 91.6 ± 9.3 vs. PL: 88.8 ± 8.2 mmHg,
p
< 0.05) were higher with BR supplementation.
[Conclusion]
These findings suggest that the acute intake of BR juice had no effect on knee extensor muscle strength or fatigue but increased BP in a healthy recreationally active population.
Plasma, urine, erythrocyte and leukocyte magnesium were measured in normotensive and hypertensive renal transplant patients who were being treated with either azathioprine or cyclosporin. These were compared with essential hypertensive patients and normal subjects. Erythrocyte and leukocyte magnesium were reduced in renal transplant patients in independent association (ANOVA) with both cyclosporin treatment (P = 0.03, P = 0.016 respectively) and hypertension (P less than 0.001 for both). Therefore, hypertensive transplant patients on cyclosporin had the lowest magnesium content of both erythrocytes (1.22 +/- 0.09 mmol/l cells) and leukocytes (2.68 +/- 0.2 nmol/10(6) cells) compared to normal subjects (1.96 +/- 0.17 and 4.11 +/- 0.58 respectively) whereas normotensive transplant patients on azathioprine had normal values (2.12 +/- 0.16 and 5.13 +/- 1.0 respectively). Plasma magnesium was also reduced with cyclosporin treatment. Urine magnesium was not significantly different between any of the groups. Therefore, magnesium depletion may have a role in hypertension in renal transplant patients. Since cyclosporin treatment is also associated with magnesium depletion, this could explain the increased occurrence of hypertension in these patients.
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