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Beetroot Juice Increases Human Muscle Force

Moderatorji: UrosS, Metka, Stasa, Grom

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Grom

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Vnosov: 63865

Pridružen: Če sep 23, 2004 18:35

Odgovor Sr maj 17, 2017 18:41

Beetroot Juice Increases Human Muscle Force

Beetroot Juice Increases Human Muscle Force Without Changing Ca2+-handling Proteins.
Whitfield J, et al. Med Sci Sports Exerc. 2017.
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Abstract

Dietary inorganic nitrate (NO3) supplementation improves skeletal muscle (SkM) contractile efficiency, and while rodent literature has suggested improvements in calcium handling or redox modifications as likely explanations, the direct mechanism-of-action in humans remains unknown.

PURPOSE: To examine the effects of 7-d of beetroot juice (BRJ) supplementation on SkM contractile characteristics and function.

METHODS: Recreationally active males (n=8) underwent transcutaneous electrical muscle stimulation of the vastus lateralis for evaluation of contractile characteristics before (pre) and after (post) 7-d of BRJ supplementation (280 mL/day, ~26 mmol NO3). An additional group of individuals (n=8) followed the same supplementation protocol but underwent SkM biopsies pre/post supplementation for determination of proteins associated with calcium handling via Western blotting, and the ratio of reduced/oxidized glutathione (GSH:GSSG), an indicator of cellular redox state, via HPLC.

RESULTS: Following supplementation, there was no change in maximal voluntary force production (602 ± 50 vs 596 ± 56 N), or electrically-induced tetanic contractions. In contrast, force production was increased at 10 Hz electrical stimulation (41.1 ± 2.3 vs 37.6 ± 2.4% of peak force, p<0.05), as was peak twitch tension (164.0 ± 12.5 vs 136.5 ± 7.2 N, p<0.01) and maximal rates of force development and relaxation (3582.8 ± 382.3 vs 2575.7 ± 196.2 and -2752.4 ± 423.9 vs -2104.4 ± 249.0 N/s, respectively, p<0.05). Despite these measurements implicating a change in calcium handling, the content of associated proteins (SERCA1a, SERCA2a, dihydropyradine receptor, ryanodine receptor, calsequestrin), and the GSH:GSSG ratio were unaltered by BRJ.

CONCLUSION: BRJ supplementation increases force production at low stimulation frequencies, however in human SkM this is independent of changes in redox stress or the expression of protein targets associated with calcium handling.
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Grom

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Pridružen: Če sep 23, 2004 18:35

Odgovor Sr maj 17, 2017 18:42

Re: Beetroot Juice Increases Human Muscle Force

Beetroot juice supplementation reduces whole body oxygen consumption but does not improve indices of mitochondrial efficiency in human skeletal muscle.
Whitfield J, et al. J Physiol. 2016.
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Abstract

KEY POINTS: Oral consumption of nitrate (NO3(-)) in beetroot juice has been shown to decrease the oxygen cost of submaximal exercise; however, the mechanism of action remains unresolved. We supplemented recreationally active males with beetroot juice to determine if this altered mitochondrial bioenergetics. Despite reduced submaximal exercise oxygen consumption, measures of mitochondrial coupling and respiratory efficiency were not altered in muscle. In contrast, rates of mitochondrial hydrogen peroxide (H2O2) emission were increased in the absence of markers of lipid or protein oxidative damage. These results suggest that improvements in mitochondrial oxidative metabolism are not the cause of beetroot juice-mediated improvements in whole body oxygen consumption.

ABSTRACT: Ingestion of sodium nitrate (NO3(-)) simultaneously reduces whole body oxygen consumption (V̇O2) during submaximal exercise while improving mitochondrial efficiency, suggesting a causal link. Consumption of beetroot juice (BRJ) elicits similar decreases in V̇O2 but potential effects on the mitochondria remain unknown. Therefore we examined the effects of 7-day supplementation with BRJ (280 ml day(-1), ∼26 mmol NO3(-)) in young active males (n = 10) who had muscle biopsies taken before and after supplementation for assessments of mitochondrial bioenergetics. Subjects performed 20 min of cycling (10 min at 50% and 70% V̇O2 peak) 48 h before 'Pre' (baseline) and 'Post' (day 5 of supplementation) biopsies. Whole body V̇O2 decreased (P < 0.05) by ∼3% at 70% V̇O2 peak following supplementation. Mitochondrial respiration in permeabilized muscle fibres showed no change in leak respiration, the content of proteins associated with uncoupling (UCP3, ANT1, ANT2), maximal substrate-supported respiration, or ADP sensitivity (apparent Km). In addition, isolated subsarcolemmal and intermyofibrillar mitochondria showed unaltered assessments of mitochondrial efficiency, including ADP consumed/oxygen consumed (P/O ratio), respiratory control ratios and membrane potential determined fluorometrically using Safranine-O. In contrast, rates of mitochondrial hydrogen peroxide (H2O2) emission were increased following BRJ. Therefore, in contrast to sodium nitrate, BRJ supplementation does not alter key parameters of mitochondrial efficiency. This occurred despite a decrease in exercise V̇O2, suggesting that the ergogenic effects of BRJ ingestion are not due to a change in mitochondrial coupling or efficiency. It remains to be determined if increased mitochondrial H2O2 contributes to this response.
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Grom

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Pridružen: Če sep 23, 2004 18:35

Odgovor Sr maj 17, 2017 18:43

Re: Beetroot Juice Increases Human Muscle Force

Nitrate supplementation enhances the contractile properties of human skeletal muscle.
Randomized controlled trial
Haider G, et al. Med Sci Sports Exerc. 2014.
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Abstract

PURPOSE: Dietary nitrate supplementation positively affects cardiovascular function at rest and energy metabolism during exercise in humans and has recently also been reported to markedly enhance the in vitro contractile properties of mouse fast-twitch muscle. The aim of this study was to investigate the effects of short-term nitrate supplementation on the in vivo contractile properties of the skeletal muscle and voluntary muscle function of humans.

METHODS: In a double-blind, randomized, crossover design, 19 healthy untrained men (21 ± 3 yr) ingested a nitrate-rich concentrated beetroot juice (NIT; nitrate dosage, approximately 9.7 mmol·d) and a placebo (PLA) for seven consecutive days. After the last supplementation dose, force was recorded while participants completed a series of voluntary and involuntary (electrically evoked) unilateral isometric contractions of the knee extensors.

RESULTS: NIT enhanced the peak force response to low-frequency electrical stimulation, as follows: maximal twitch (NIT, 149 ± 41 N, vs PLA, 138 ± 37 N; P = 0.008; effect size, r (ES) = 0.56) and submaximal 1- to 20-Hz contractions (5%-10%, ES = 0.53-0.63). Whereas explosive (rising phase) force production during the first 50 ms of evoked maximal twitch and octet contractions (eight electrical impulses at 300 Hz) was also 3%-15% greater after NIT compared with that after PLA (P = 0.023-0.048, ES = 0.52-0.59), explosive voluntary force remained similar (P = 0.510, ES = 0.16). Maximum voluntary force was also unchanged after NIT (P = 0.539, ES = 0.15).

CONCLUSIONS: These results indicate that 7 d of dietary nitrate supplementation enhanced the in vivo contractile properties of the human skeletal muscle. Specifically, nitrate supplementation improved excitation-contraction coupling at low frequencies of stimulation and enhanced evoked explosive force production but did not affect maximum or explosive voluntary force production in untrained individuals.
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Grom

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Vnosov: 63865

Pridružen: Če sep 23, 2004 18:35

Odgovor Sr maj 17, 2017 18:44

Re: Beetroot Juice Increases Human Muscle Force

Nitrate supDietary Nitrate and Skeletal Muscle Contractile Function in Heart Failure.
Review article
Coggan AR, et al. Curr Heart Fail Rep. 2016.
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Abstract

Heart failure (HF) patients suffer from exercise intolerance that diminishes their ability to perform normal activities of daily living and hence compromises their quality of life. This is due largely to detrimental changes in skeletal muscle mass, structure, metabolism, and function. This includes an impairment of muscle contractile performance, i.e., a decline in the maximal force, speed, and power of muscle shortening. Although numerous mechanisms underlie this reduction in contractility, one contributing factor may be a decrease in nitric oxide (NO) bioavailability. Consistent with this, recent data demonstrate that acute ingestion of NO3 (-)-rich beetroot juice, a source of NO via the NO synthase-independent enterosalivary pathway, markedly increases maximal muscle speed and power in HF patients. This review discusses the role of muscle contractile dysfunction in the exercise intolerance characteristic of HF, and the evidence that dietary NO3 (-) supplementation may represent a novel and simple therapy for this currently underappreciated problem.
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Grom

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Vnosov: 63865

Pridružen: Če sep 23, 2004 18:35

Odgovor Sr maj 17, 2017 18:45

Re: Beetroot Juice Increases Human Muscle Force

Nitrate ingestion: a review of the health and physical performance effects.
Review article
Clements WT, et al. Nutrients. 2014.
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Abstract

This paper provides an overview of the current literature and scientific evidence surrounding inorganic nitrate (NO3-) supplementation and its potential for improving human health and physical performance. As indicative of the ever-expanding organic and natural food consumer market, athletes and health enthusiasts alike are constantly searching for ingredient-specific "super foods" and dietary supplements capable of eliciting health and performance benefits. Evidence suggests that NO3- is the viable active component within beetroot juice (BRJ) and other vegetables, responsible for health-promoting and ergogenic effects. Indeed, multiple studies support NO3- supplementation as an effective method to improve exercise performance. NO3- supplementation (either as BRJ or sodium nitrate [NaNO3-]) has also demonstrated modest benefits pertaining to cardiovascular health, such as reducing blood pressure (BP), enhancing blood flow, and elevating the driving pressure of O2 in the microcirculation to areas of hypoxia or exercising tissue. These findings are important to cardiovascular medicine/exercise physiology and suggest a possible role for NO3- supplementation: (1) as a low-cost prevention and treatment intervention for patients suffering from blood flow disorders; and (2) an effective, natural ergogenic aid for athletes. Benefits have been noted following a single bolus, as well as daily supplementation of NO3-. While results are promising, additional research is needed to determine the impact of NO3- supplementation on anaerobic exercise performance, to identify principle relationships between isolated nitrate and other ingredients found in nitrate-rich vegetables (e.g., vitamin C, polyphenols, fatty acids, thiocyanate), to explore the specific dose-response relationships needed to elicit health and ergogenic benefits, to prolong the supplementation period beyond a relatively short period (i.e., >15 days), to determine if more robust effects can be observed with longer-term treatment, and to fully examine the safety of chronic NO3- supplementation, as this continues to be a concern of some.
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Pridružen: Če sep 23, 2004 18:35

Odgovor Sr maj 17, 2017 18:49

Re: Beetroot Juice Increases Human Muscle Force

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