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Available from: Igho Onakpoya
Background : Several slimming aids being sold as food supplements are widely available. One of them is pyruvate. Its efficacy in causing weight reduction in humans has not been fully established. The objective of this systematic review was to examine the efficacy of pyruvate in reducing body weight. Methods: Electronic and nonelectronic searches were conducted to identify all relevant human randomized clinical trials. The bibliographies of all located articles were also searched. No restrictions in language or time were applied. Two independent reviewers extracted the data according to predefined criteria. A fixed-effect model was used to calculate mean differences (MD) and 95% confidence interval (CI). Results: Nine trials were identified and 6 were included. All had methodological weaknesses. The meta-analysis revealed a statistically significant difference in body weight with pyruvate compared to placebo (MD: -0.72 kg; 95% CI: -1.24 to -0.20). The magnitude of the effect is small, and its clinical relevance is uncertain. Adverse events included gas, bloating, diarrhea, and increase in low-density lipoprotein (LDL) cholesterol. Conclusion: The evidence from randomized clinical trials does not convincingly show that pyruvate is efficacious in reducing body weight. Limited evidence exists about the safety of pyruvate. Future trials involving the use of this supplement should be more rigorous and better reported.
Critical reviews in food science and nutrition 01/2014; 54(1):17-23. DOI:10.1080/10408398.2011.565890
Together with carbon monoxide (CO), nitric oxide (̇NO) and hydrogen sulfide (H2S) form a group of physiologically important gaseous transmitters, sometimes referred to as the “gaseous triumvirate”. The three molecules share a wide range of physical and physiological properties: they are small gaseous molecules, able to freely penetrate cellular membranes; they are all produced endogenously in the body and they seem to exert similar biological functions. In the cardiovascular system, for example, they are all vasodilators, promote angiogenesis and protect tissues against damage (e.g. ischemia-reperfusion injury). In addition, they have complex roles in inflammation, with both pro- and anti-inflammatory effects reported. Researchers have focused their efforts in understanding and describing the roles of each of these molecules in different physiological systems, and in the past years attention has also been given to the gases interaction or “cross-talk”. This review will focus on the role of ̇NO and H2S in inflammation and will give an overview of the evidence collected so far suggesting the importance of their cross-talk in inflammatory processes.
The intake of whey, compared with casein and soy protein intakes, stimulates a greater acute response of muscle protein synthesis (MPS) to protein ingestion in rested and exercised muscle.
We characterized the dose-response relation of postabsorptive rates of myofibrillar MPS to increasing amounts of whey protein at rest and after exercise in resistance-trained, young men.
Volunteers (n = 48) consumed a standardized, high-protein (0.54 g/kg body mass) breakfast. Three hours later, a bout of unilateral exercise (8 × 10 leg presses and leg extensions; 80% one-repetition maximum) was performed. Volunteers ingested 0, 10, 20, or 40 g whey protein isolate immediately (∼10 min) after exercise. Postabsorptive rates of myofibrillar MPS and whole-body rates of phenylalanine oxidation and urea production were measured over a 4-h postdrink period by continuous tracer infusion of labeled [(13)C6] phenylalanine and [(15)N2] urea.
Myofibrillar MPS (±SD) increased (P < 0.05) above 0 g whey protein (0.041 ± 0.015%/h) by 49% and 56% with the ingestion of 20 and 40 g whey protein, respectively, whereas no additional stimulation was observed with 10 g whey protein (P > 0.05). Rates of phenylalanine oxidation and urea production increased with the ingestion of 40 g whey protein.
A 20-g dose of whey protein is sufficient for the maximal stimulation of postabsorptive rates of myofibrillar MPS in rested and exercised muscle of ∼80-kg resistance-trained, young men. A dose of whey protein >20 g stimulates amino acid oxidation and ureagenesis. This trial was registered at http://www.isrctn.org/ as ISRCTN92528122.
American Journal of Clinical Nutrition 11/2013; 99(1). DOI:10.3945/ajcn.112.055517
Available from: Alex Rowlands
The Sedentary Sphere is a method for the analysis, identification and visual presentation of sedentary behaviours from a wrist-worn triaxial accelerometer.
To introduce the concept of the Sedentary Sphere, and to determine the accuracy of posture classification from wrist accelerometer data.
Three samples were used: 1) free-living (N=13, aged 20-60y); 2) laboratory-based (N=25, aged 30-65y); 3) hospital in-patients (N=10, aged 60-90y). All participants wore a GENEActiv on their wrist and activPAL on their thigh. The free-living sample wore an additional GENEActiv on the thigh and completed the Multimedia Activity Recall for Children & Adults (MARCA). The laboratory-based sample wore the monitors while seated at a desk for seven hours, punctuated by two minutes of walking every 20 minutes. The free-living and in-patient samples wore the monitors for 24 h. Posture was classified from wrist-worn accelerometry using the Sedentary Sphere concept.
Sitting time did not differ between the wrist GENEActiv and the activPAL in the free-living sample and was correlated in the three samples combined (rho=0.9, p<0.001), free-living and in-patient samples (r≃0.8, p<0.01). Mean intra-individual agreement was 85±7%. In the laboratory-based and in-patient samples, sitting time was underestimated by the wrist GENEActiv by 30 minutes and two hours relative to the activPAL, respectively (p<0.05). Posture classification disagreed during reading while standing, cooking standing and brief periods during driving. Posture allocation validity was excellent when the GENEActiv was worn on the thigh, evidenced by near perfect agreement with the activPAL (96±3%).
The Sedentary Sphere enables determination of the most likely posture from the wrist-worn GENEActiv. Visualising behaviours on the Sphere displays the pattern of wrist movement and positions within that behaviour.
Medicine and science in sports and exercise 11/2013; DOI:10.1249/MSS.0000000000000224
EMBO Reports 11/2013; 14(12). DOI:10.1038/embor.2013.174
Muscular coactivation can help stabilise a joint, but contrasting results in previous gait studies highlight that it is not clear whether this is metabolically beneficial. The aim was to assess the relationship between the metabolic cost of running and muscular coactivation across different running speeds, in addition to assessing the reliability and precision of lower limb muscular coactivation.
Eleven female recreational runners visited the laboratory on two separate occasions. On both occasions subjects ran at three speeds (9.1, 11 and 12kmh(-1)) for six minutes each.
Oxygen consumption and electromyographic data were simultaneously recorded during the final two minutes of each speed. Temporal coactivations of lower limb muscles during the stance phase were calculated. Five muscles were assessed: rectus femoris, vastus lateralis, biceps femoris, tibialis anterior and gastrocnemius lateralis.
Nonparametric correlations revealed at least one significant, positive association between lower limb muscular coactivation and the metabolic cost of running for each speed. The length of tibialis anterior activation and muscular coactivation of the biceps femoris-tibialis anterior and gastrocnemius lateralis-tibialis anterior decreased with speed.
These results show that longer coactivations of the proximal (rectus femoris-biceps femoris and vastus lateralis-biceps femoris) and leg extensor (rectus femoris-gastrocnemius lateralis) muscles were related to a greater metabolic cost of running, which could be detrimental to performance. The decrease in coactivation in the flexor and distal muscles at faster speeds occurs due to the shorter duration of tibialis anterior activation as speed increases, yet stability may be maintained.
Severe-intensity exercise initiated from an elevated metabolic rate would be expected to enhance the proportional activation of higher-order (type II) muscle fibers. The purpose of this study was therefore to test the hypothesis that, compared to placebo (PL), NO3--rich beetroot juice (BR) supplementation would speed the phase II vo2 kinetics (τp) and enhance exercise tolerance during severe-intensity exercise initiated from a baseline of moderate-intensity exercise. Nine healthy, physically-active subjects were assigned in a randomized, double-blind, crossover design to receive BR (140 mL/day, containing ~8 mmol of NO3(-)) and PL (140 mL/day, containing ~0.003 mmol of NO3(-)) for 6 days. On days 4, 5 and 6 of the supplementation periods, subjects completed a double-step exercise protocol that included transitions from unloaded-to-moderate intensity exercise (U→M) followed immediately by moderate-to-severe-intensity exercise (M→S). Compared to PL, BR elevated resting plasma nitrite concentration (PL: 65 ± 32 vs. BR: 348 ± 170 nM, P<0.01) and reduced the vo2 τp in M→S (PL: 46 ± 13 vs. BR: 36 ± 10 s, P<0.05) but not U→M (PL: 25 ± 4 vs. BR: 27 ± 6 s, P>0.05). During M→S exercise, the faster vo2 kinetics coincided with faster NIRS-derived muscle [deoxyhemoglobin] kinetics (τ; PL: 20 ± 9 vs. BR: 10 ± 3 s, P<0.05) and a 22% greater time-to-task failure (PL: 521 ± 158 vs. BR: 635 ± 258 s, P<0.05). Dietary supplementation with NO3(-)-rich BR juice speeds vo2 kinetics and enhances exercise tolerance during severe-intensity exercise when initiated from an elevated metabolic rate.
AJP Regulatory Integrative and Comparative Physiology 10/2013; 305(12). DOI:10.1152/ajpregu.00295.2013
Available from: Katya Mileva
We investigated whether altered peripheral and/or corticospinal excitatory output and voluntary activation are implicated in hypohydration-induced reductions in muscle isometric and isokinetic (90°.s(-1)) strength. Nine male athletes completed two trials (hypohydrated, euhydrated) comprising 90 min cycling at 40°C, with body weight losses replaced in euhydrated trial. Peripheral nerve and transcranial magnetic stimulations were applied during voluntary contractions pre- and 40 min post-exercise to quantify voluntary activation and peripheral (M-wave) and corticospinal (motor evoked potential) evoked responses in m. vastus medialis. Both maximum isometric (-15.3±3.1 vs -5.4±3.5%) and isokinetic eccentric (-24.8±4.6 vs -7.3±7.2%) torque decreased to a greater extent in hypohydrated than euhydrated trials (p<0.05). Half relaxation time of the twitch evoked by peripheral nerve stimulation during maximal contractions increased after exercise in the hypohydrated (21.8±9.3%) but stayed constant in the euhydrated (1.6±10.7%; p = 0.017) condition. M-wave amplitude during maximum voluntary contraction increased after exercise in the heat in hypohydrated (10.7±18.0%) but decreased in euhydrated condition (-17.4±16.9%; p = 0.067). Neither peripheral nor cortical voluntary activation were significantly different between conditions. Motor evoked potential amplitude increased similarly in both conditions (hypohydrated: 25.7±28.5%; euhydrated: 52.9±33.5%) and was accompanied by lengthening of the cortical silent period in euhydrated but not hypohydrated condition (p = 0.019). Different neural strategies seem to be adopted to regulate neural drive in the two conditions, with increases in inhibitory input of either intracortical or corticospinal origin during the euhydrated trial. Such changes were absent in the hypohydrated condition, yet voluntary activation was similar to the euhydrated condition, perhaps due to smaller increases in excitatory drive rather than increased inhibition. Despite this maximal isometric and eccentric strength were impaired in the hypohydrated condition. The increase in peripheral muscle excitability evident in the hypohydrated condition was not sufficient to preserve performance in the face of reduced muscle contractility or impaired excitation-contraction coupling.
PLoS ONE 10/2013; 8(10):e77004. DOI:10.1371/journal.pone.0077004
Available from: Edzard Ernst
Molassiotis is the author of about 40 reviews, all of which are
prone to the shortcomings he highlights. His statement, “I urge
researchers in the field not to proliferate publications of ‘systematic’
reviews of a very small number and of admittedly
poor/low quality level trials”, is thus surprising to say the least.
The main point of his response seems to be that “systematic
reviews of few and low-quality studies do not help anybody”.
We feel that such articles can still be useful, for instance, for
disclosing important deficits in our current knowledge.
In making this point, Molassiotis seems to display a lack of
understanding of science in general and systematic reviews in
particular. Here are a few of his most obvious errors:
He asks “didn’t we know this [the result of a systematic
review] before the review”? It seems obvious to us that the
findings of a review can never be known before the research
has been conducted.
He refers to “systematic reviews on the same topic by
several different authors”. Yet a closer look at the actual
articles he quotes informs us that they are, in fact, on subtly
He claims that we believe that “anything that does not have
a sham arm is not a good trial”. Yet we never stated anything
like this. We would, however, argue that, for determining
whether an intervention has therapeutic effects beyond placebo,
a placebo/sham control is helpful.
He argues that controlling for placebo effects in acupuncture
trials is done “to give some ‘science’ credentials to such
trials and mimic drug trial placebo-controlled designs”. We
would counter that the sole reason for doing this is to be able
to differentiate between specific and non-specific therapeutic
effects; in our view, this is important for determining the value
of any treatment.
He states, “I am questioning the ethics” [of such sham controlled
studies].We would insist that differentiating between
placebo and specific effects is a crucial ethical task of clinical
He claims that “bringing all acupuncture trials together
as one treatment is like mixing apples and oranges”.
We would like to remind him that, by definition, systematic
reviews are about summary judgements of this nature
and that most of his own reviews have followed exactly the
Finally, we agree with him that “we should not deny patients
the possibility of experiencing symptom relief and health improvements
because of sterile and incapacitating arguments
about how to carry out ‘proper’ acupuncture trials”. But we
need to point out that, before we can be sure that patients do
benefit from our interventions, we need to determine whether
they generate more good than harm. In our opinion, this requires
rigorous research, and any attempt to bypass this process
is likely to be counterproductive and unethical.
Conflict of interest Both authors declare no competing interests.
Open Access This article is distributed under the terms of the Creative
Commons Attribution Noncommercial License which permits any
noncommercial use, distribution, and reproduction in any medium, provided
the original author(s) and the source are credited.
Supportive Care in Cancer 10/2013; DOI:10.1007/s00520-013-1990-5
Available from: Fred Dimenna
We investigated the responses of intramuscular phosphate-linked metabolites and pH (as assessed by (31)P-MRS) during intermittent high-intensity exercise protocols performed with different recovery-interval durations. Following estimation of the parameters of the power-duration relationship (i.e., CP and W') for severe-intensity constant-power exercise, eight male subjects completed three intermittent exercise protocols to exhaustion where periods of high-intensity exercise (60-s) were separated by different durations of passive recovery (18-s, 30-s and 48-s). The tolerable duration of exercise was 304 ± 68 s, 516 ± 142 s and 847 ± 240 s for the 18-s, 30-s and 48-s recovery protocols, respectively (P<0.05). The work done >CP (W>CP) was significantly greater for all intermittent protocols compared to the subjects' W' and this difference became progressively greater as recovery-interval duration was increased. Similarly, the degree of intramuscular phosphocreatine restoration during recovery was greatest, intermediate and least for 48-s, 30-s and 18-s of recovery, respectively (P<0.05). The W>CP in excess of W' increased with greater durations of recovery and this was correlated with the mean magnitude of muscle phosphocreatine reconstitution between work intervals (r = 0.61; P<0.01). During intermittent high-intensity exercise, recovery intervals allow intramuscular homeostasis to be restored, with the degree of restoration being related to the duration of the recovery interval. Consequently, the ability to perform W>CP during intermittent high-intensity exercise and, therefore, exercise tolerance, increases in a predictable manner when recovery-interval duration is extended.
AJP Regulatory Integrative and Comparative Physiology 09/2013; DOI:10.1152/ajpregu.00406.2013
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