[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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;
[Show abstract][Hide abstract] 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;
[Show abstract][Hide abstract] 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
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.
[Show abstract][Hide abstract] 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;
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] 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.
[Show abstract][Hide abstract] ABSTRACT: Abstract We investigated the musculoskeletal health profile of elite female football players (ET) in comparison to untrained (UT) young women subjected to 16 weeks of football training (2 × 1 h per week). DXA scans, blood sampling, sprint testing and Flamingo postural balance testing were carried out for 27 Danish national team players and 28 untrained women, with eight women being tested after training. At baseline total BMD and BMC were 13% (1.305 ± 0.050 versus 1.159 ± 0.056 g · cm(-2)) and 23% (3047 ± 235 versus 2477 ± 526 g) higher (P <0.001) and leg BMD and BMC were 24 and 28% higher (P <0.01) in ET than in UT. Resting plasma osteocalcin was 45% higher in ET than in UT (28.8 ± 10.9 versus 19.9 ± 9.9 µg · L(-1), P <0.05). Total lean body mass was 14% higher (50.4 ± 3.3 versus 44.3 ± 4.0 kg) in ET compared with UT, with no difference in total body mass. The number of Flamingo test falls was 56-63% less (P <0.01) and 30 m sprinting speed was 31% faster (P <0.001) in ET than UT. After 16 weeks of football training for UT, lean body mass increased by 1.4 ± 0.5 kg and the number of left leg falls decreased by 29% (P <0.05). No significant changes occurred in BMD or BMC, but plasma osteocalcin increased (P <0.05) by 37%. In summary, elite women footballers have an impressive musculoskeletal health profile compared with untrained controls, but short-term football training seems to reduce the risk of falls and increase bone formation.
[Show abstract][Hide abstract] ABSTRACT: Abstract It has been shown that the critical power (CP) in cycling estimated using a novel 3-min all-out protocol is reliable and closely matches the CP derived from conventional procedures. The purpose of this study was to assess the predictive validity of the all-out test CP estimate. We hypothesised that the all-out test CP would be significantly correlated with 16.1-km road time-trial (TT) performance and more strongly correlated with performance than the gas exchange threshold (GET), respiratory compensation point (RCP) and [Formula: see text]O2 max. Ten club-level male cyclists (mean±SD: age 33.8±8.2 y, body mass 73.8±4.3 kg, [Formula: see text]O2 max 60±4 ml·kg(-1)·min(-1)) performed a 10-mile road TT, a ramp incremental test to exhaustion, and two 3-min all-out tests, the first of which served as familiarisation. The 16.1-km TT performance (27.1±1.2 min) was significantly correlated with the CP (309±34 W; r=-0.83, P<0.01) and total work done during the all-out test (70.9±6.5 kJ; r=-0.86, P<0.01), the ramp incremental test peak power (433±30 W; r=-0.75, P<0.05) and the RCP (315±29 W; r=-0.68, P<0.05), but not with GET (151±32 W; r=-0.21) or the [Formula: see text]O2 max (4.41±0.25 L·min(-1); r=-0.60). These data provide evidence for the predictive validity and practical performance relevance of the 3-min all-out test. The 3-min all-out test CP may represent a useful addition to the battery of tests employed by applied sport physiologists or coaches to track fitness and predict performance in atheletes.
[Show abstract][Hide abstract] ABSTRACT: Our aim was to determine the effects of different inspired oxygen fractions on repeated sprint performance and cardiorespiratory and neuromuscular responses, to construct a hypoxic dose response.
Nine male well-trained multi-sport athletes completed 10×6s all-out running sprints with 30s recovery in 5 conditions with different inspired oxygen fraction (FIO2: 12%, 13%, 14%, 15%, 21%).
Peak running speed was measured in each sprint and electromyography data were recorded from m. vastus lateralis in parallel with heart rate and blood oxygen saturation. Cardiorespiratory response was assessed via breath by breath expired air analysis and muscle oxygenation status was evaluated via near infrared spectroscopy.
In parallel with the higher heart rate, minute ventilation, blood lactate concentration, and muscle deoxygenation; lower blood oxygen saturation, pulmonary oxygen uptake and integrated EMG (all p<0.05) were registered in all hypoxic conditions, with the greatest changes from baseline observed during the 13% trial. However, fatigue index and speed decrement were significantly greater only during the 12% vs 21% trial (p<0.05).
Physiological responses associated with performing 10×6s sprints interspersed with 30s passive recovery was incrementally greater as FIO2 decreased to 13%, yet fatigue development was significantly exacerbated relative to normoxia (FIO2: 21%) only at the 12% FIO2.
Journal of science and medicine in sport / Sports Medicine Australia. 06/2013;
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