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    ABSTRACT: 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.
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    ABSTRACT: 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;
  • EMBO Reports 11/2013;
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    ABSTRACT: 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.
    Journal of science and medicine in sport / Sports Medicine Australia. 10/2013;
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    ABSTRACT: 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;
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    ABSTRACT: 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 different subjects. 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 research. 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 same principles. 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;
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    ABSTRACT: 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;
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    ABSTRACT: Abstract The study examined Yo-Yo intermittent recovery level 2 (YYIR2) and submaximal YYIR1 test performances in 172 male semi-professional football players (age; 25.8 ± 4.1 years) representing all teams in a top league at pre-season, start-season, mid-season and end-season. YYIR2 performance was 847 ± 227 m (±SD) at pre-season and rose (P < 0.05) by 128 ± 113 m to 975 ± 205 m at start of season and further (P < 0.05) by 59 ± 102 m to 1034 ± 211 m at mid-season. Submaximal YYIR1 HR was 90.9 ± 4.2% HRmax at pre-season, which was higher (P < 0.05) than at start, mid and end of season (87.0 ± 3.9, 85.9 ± 4.1 and 87.0 ± 3.7% HRmax, respectively). Peak YYIR2 performance and minimum YYIR1 HR were 1068 ± 193 m and 85.1 ± 3.8% HRmax, respectively, with ∼50% of the players peaking at mid-season. Top-teams and middle-teams had higher (P < 0.05) peak YYIR2 scores (1094 ± 205 and 1121 ± 152 m, respectively) than bottom-teams (992 ± 185 m). YYIR2 performance was 16% higher (P < 0.05) and YYIR1 HR was 1.4% HRmax lower (P < 0.05) for regular players than non-regular players at pre-season and remained lower (P < 0.05) throughout the season. Central defenders had poorer (P < 0.05) YYIR performances compared to other positional roles. In conclusion, YYIR performances are highly variable within a football league over a season and are influenced by league ranking, regularity of competitive play and playing position.
    Journal of Sports Sciences 08/2013;
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    ABSTRACT: Barefoot running has increased in popularity over recent years, with suggested injury risk and performance benefits. However, despite many anecdotal descriptions of barefoot running styles, there is insufficient evidence regarding the specific characteristics of barefoot running. The present study provided reference data for four footstrike modalities adopted across a large cohort of habitually shod male runners while running barefoot: heel strikers (HS), midfoot strikers (MS), forefoot strikers (FS) and a newly defined group, toe runners (TR - contact made only with the forefoot), compared with the three modalities previously reported. Plantar pressure analysis was used for the classification of footstrike modality, with clearly distinguishable pressure patterns for different modalities. In the present study, the distribution of footstrike types was similar to that previously observed in shod populations. The absence of differences in ground contact time and stride length suggest that potential performance benefits of a non-HS style are more likely to be a function of the act of running barefoot, rather than of footstrike type. Kinematic data for the knee and ankle indicate that FS and TR require a stiffer leg than HS or MS, while ankle moment and plantar pressure data suggest that a TR style may put greater strain on the plantar-flexors, Achilles tendon and metatarsal heads. TR style should therefore only be adopted with caution by recreational runners. These findings indicate the importance of considering footstrike modality in research investigating barefoot running, and support the use of four footstrike modalities to categorise running styles.
    Journal of biomechanics 08/2013;
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    ABSTRACT: Poor self-regulation of high energy snacking has been linked to weight gain. Physical activity can acutely reduce chocolate consumption and cravings but the effects on attentional bias (AB) are unknown. The study aimed to test the effects of exercise among normal and overweight/obese individuals during temporary and longer abstinence. Participants were 20 normal and 21 overweight regular female chocolate eaters (after 24 hr abstinence), and 17 females (after ⩾ 1 week abstinence during Lent). They were randomly assigned to engage in 15 min brisk walking or rest, on separate days. AB was assessed using an adapted dot probe task pre and post-treatment at each session, with chocolate/neutral paired images presented for 200ms (initial AB; IAB) or 1000ms (maintained AB; MAB). Chocolate craving was assessed pre, during, immediately after, and 5mins and 10mins after treatment, using a 0-100 visual analogue score. Three-way mixed ANOVAs revealed that there was no significant interaction effect between group (i.e., BMI status, or abstinence status) and condition × time for craving and AB to chocolate cues. Fully repeated 2-way ANOVAS revealed a significant condition × time interaction for IAB (F(1, 57) = 6.39) and chocolate craving (F(2.34, 133.19) = 14.44). After exercise IAB (t(57) = 2.78, p< 0.01) was significantly lower than after the rest condition. Craving was significantly lower than the rest condition at all assessments post-baseline. A short bout of physical activity reduces cravings and AB to chocolate cues, relative to control, irrespective of BMI or abstinence period.
    Appetite 08/2013;
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