PURPOSE: Recent studies suggest that NO bioavailability may be elevated by ingestion of nitrate-rich food (i.e., beetroot juice) or nitrate salts, modulating vascular tone as well as muscle oxidative metabolism during exercise. In rodents, dietary nitrate supplementation improves the perfusion of active skeletal muscles during dynamic exercise. In humans, similar results have been observed by direct infusion of elevated dose of sodium nitrite during forearm exercise whereas acute nitrate supplementation did not increase brachial artery blood flow during non-fatiguing forearm exercise. Aim of this study was to evaluate the effects of an acute dose of sodium nitrate on exercise hyperemia and skeletal muscle metabolism during light and vigorous forearm exercise. METHODS: Nine male young (28 ± 4 yr) healthy subjects were enrolled in a randomized, double-blind, placebo-controlled crossover study. Each subject performed a forearm exercise by a custom-built pulley device at six different intensities (15, 30, 45, 60, 75 and 90% of peak work rate) after both sodium nitrate (8.4 mM [NITR]) and sodium chloride (8.4 mM [PLA]) ingestion. Ultrasound Doppler was used to assess brachial artery blood flow. Muscle oxygenation characteristics were assessed by near-infrared spectroscopy. RESULTS: Plasma nitrate concentration was significantly increased after NITR (from 21.2 ± 4.4 to 121.3 ± 28.8 nM). Brachial artery blood flow increased linearly with workrate (NITR: r2 = 0.97, P<0.001; PLA: r2 = 0.98, P<0.001) and no significant differences were observed between NITR and PLA at any exercise intensity. Muscle oxygen fractional extraction index (?[deoxy(Hb+Mb)]), corrected by blood volume changes (?[tot(Hb+Mb)]), was significantly reduced after NITR vs. PLA at 45% (43.5 ± 6.7 vs. 29.0 ± 8.2% of ischemia), 60% (58.3 ± 9.3 vs. 33.2 ± 7.4%), and 75% (61.1 ± 11.9 vs. 39.6 ± 6.9%). CONCLUSIONS: Acute dietary nitrate supplementation does not increase brachial artery blood flow during forearm exercise in healthy young males even at high-intensity, condition that should have increased activation of the nitrate-nitrite-NO signalling pathway. Interestingly, acute ingestion of sodium nitrate seems to reduce O2 fractional extraction muscle capacity during submaximal (from 45% to 75% of maximal workload) exercises.
Sodium Nitrate Effects On Muscle Blood Flow And Oxidative Metabolism During Forearm Exercise: 3701 Board #140 June 4, 9: 30 AM - 11: 00 AM.
Porcelli Simone;Pugliese Lorenzo;Rastelli Fabio;MrakicSposta Simona;Moretti Sara;Vezzoli Alessandra;Marzorati Mauro
2016
Abstract
PURPOSE: Recent studies suggest that NO bioavailability may be elevated by ingestion of nitrate-rich food (i.e., beetroot juice) or nitrate salts, modulating vascular tone as well as muscle oxidative metabolism during exercise. In rodents, dietary nitrate supplementation improves the perfusion of active skeletal muscles during dynamic exercise. In humans, similar results have been observed by direct infusion of elevated dose of sodium nitrite during forearm exercise whereas acute nitrate supplementation did not increase brachial artery blood flow during non-fatiguing forearm exercise. Aim of this study was to evaluate the effects of an acute dose of sodium nitrate on exercise hyperemia and skeletal muscle metabolism during light and vigorous forearm exercise. METHODS: Nine male young (28 ± 4 yr) healthy subjects were enrolled in a randomized, double-blind, placebo-controlled crossover study. Each subject performed a forearm exercise by a custom-built pulley device at six different intensities (15, 30, 45, 60, 75 and 90% of peak work rate) after both sodium nitrate (8.4 mM [NITR]) and sodium chloride (8.4 mM [PLA]) ingestion. Ultrasound Doppler was used to assess brachial artery blood flow. Muscle oxygenation characteristics were assessed by near-infrared spectroscopy. RESULTS: Plasma nitrate concentration was significantly increased after NITR (from 21.2 ± 4.4 to 121.3 ± 28.8 nM). Brachial artery blood flow increased linearly with workrate (NITR: r2 = 0.97, P<0.001; PLA: r2 = 0.98, P<0.001) and no significant differences were observed between NITR and PLA at any exercise intensity. Muscle oxygen fractional extraction index (?[deoxy(Hb+Mb)]), corrected by blood volume changes (?[tot(Hb+Mb)]), was significantly reduced after NITR vs. PLA at 45% (43.5 ± 6.7 vs. 29.0 ± 8.2% of ischemia), 60% (58.3 ± 9.3 vs. 33.2 ± 7.4%), and 75% (61.1 ± 11.9 vs. 39.6 ± 6.9%). CONCLUSIONS: Acute dietary nitrate supplementation does not increase brachial artery blood flow during forearm exercise in healthy young males even at high-intensity, condition that should have increased activation of the nitrate-nitrite-NO signalling pathway. Interestingly, acute ingestion of sodium nitrate seems to reduce O2 fractional extraction muscle capacity during submaximal (from 45% to 75% of maximal workload) exercises.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
