554 research outputs found
The Potential Benefits of Red Beetroot Supplementation in Health and Disease
No full textIn recent years there has been a growing interest in the biological activity of red beetroot (Beta vulgaris rubra) and its potential utility as a health promoting and disease preventing functional food. As a source of nitrate, beetroot ingestion provides a natural means of increasing in vivo nitric oxide (NO) availability and has emerged as a potential strategy to prevent and manage pathologies associated with diminished NO bioavailability, notably hypertension and endothelial function. Beetroot is also being considered as a promising therapeutic treatment in a range of clinical pathologies associated with oxidative stress and inflammation. Its constituents, most notably the betalain pigments, display potent antioxidant, anti-inflammatory and chemo-preventive activity in vitro and in vivo. The purpose of this review is to discuss beetroot’s biological activity and to evaluate evidence from studies that specifically investigated the effect of beetroot supplementation on inflammation, oxidative stress, cognition and endothelial function
Influence of a montmorency cherry juice blend on indices of exercise-induced stress and upper respiratory tract symptoms following marathon running - a pilot investigation
No full textThis is the first study that provides encouraging evidence of the potential role of Montmorency cherries in reducing the development of URTS post-Marathon possibly caused by exercise-induced hyperventilation trauma, and/or other infectious and non-infectious factors
Analgesic and anti-inflammatory drugs in sports: implications for exercise performance and training adaptations
No full textOver-the-counter analgesics, such as anti-inflammatory drugs (NSAIDs) and paracetamol, are widely consumed by athletes worldwide to increase pain tolerance, or dampen pain and reduce inflammation from injuries. Given that these drugs also can modulate tissue protein turnover, it is important to scrutinize the implications of acute and chronic use of these drugs in relation to exercise performance and the development of long-term training adaptations. In this review we aim to provide an overview of the studies investigating the effects of analgesic drugs on exercise performance and training adaptations relevant for athletic development. There is emerging evidence that paracetamol might acutely improve important endurance parameters as well as aspects of neuromuscular performance, possibly through increased pain tolerance. Both NSAIDs and paracetamol have been demonstrated to inhibit cyclooxygenase (COX) activity, which might explain the reduced anabolic response to acute exercise bouts. Consistent with this, NSAIDs have been reported to interfere with muscle hypertrophy and strength gains in response to chronic resistance training in young individuals. Although it remains to be established whether any of these observations also translate into detriments in sport-specific performance or reduced training adaptations in elite athletes, the extensive use of these drugs certainly raises practical, ethical and important safety concerns that need to be adressed. Overall, we encourage greater awareness among athletes, coaches and support staff on the potential adverse effects of these drugs. A risk-benefit analysis and professional guidance is strongly advised before the athlete considers analgesic medicine for training or competition
The role of intra-session exercise sequence on the interference effect: a systematic review with meta-analysis
No full textBackground: There is a necessity for numerous sports to develop strength and aerobic capacity simultaneously, placing a significant demand upon the practice of effective concurrent training methods. Concurrent training requires the athlete to perform both resistance and endurance exercise within a training plan. This training paradigm has been associated with an ‘interference effect’, with attenuated strength adaptation in comparison to that following isolated resistance training. The effectiveness of the training programme rests on the intricacies of manipulating acute training variables, such as exercise sequence. The research, in the most part, does not provide clarity of message as to whether intra-session exercise sequence has the potential to exacerbate or mitigate the interference effect associated with concurrent training methods.
Objective: The aim of the systematic review and meta-analysis was to assess whether intra-session concurrent exercise sequence modifies strength-based outcomes associated with the interference effect.
Methods: Ten studies were identified from a systematic review of the literature, for the outcomes of lower-body dynamic and static strength, lower-body hypertrophy, maximal aerobic capacity, and body fat %. Each study examined the effect of intra-session exercise sequence on the specified outcomes, across a prolonged (≥5 wk) concurrent training programme in healthy adults.
Results: Analysis of pooled data indicated that a resistance-endurance exercise sequence had a positive effect for lower-body dynamic strength, in comparison to the alternate sequence (weighted mean difference: 6.91% change; 95% CI: 1.96, 11.87% change; p=0.006), with no effect of exercise sequence for lower-body muscle hypertrophy (weighted mean difference: 1.15% change; 95% CI: -1.56, 3.87% change; p=0.40), lower-body static strength (weighted mean difference: -0.04% change; 95% CI: -3.19, 3.11% change; p=0.98), or the remaining outcomes of maximal aerobic capacity and body fat % (p>0.05).
Conclusion: These results indicate that the practice of concurrent training with a resistance followed by endurance exercise order is beneficial for the outcome of lower-body dynamic strength, while alternating the order of stimuli offers no benefit for training outcomes associated with the interference effect
Performance Fatigability Is Not Regulated to A Peripheral Critical Threshold
No full textThe critical threshold hypothesis proposes that performance fatigability during high-intensity exercise is tightly regulated by negative-feedback signals from the active muscles. We propose that performance fatigability is simply dependent on the exercise mode and intensity; the consequent adjustments, in skeletal muscle and the other physiological systems that support exercise, interact to modulate fatigue and determine exercise tolerance
Modulation of specific inhibitory networks in fatigued locomotor muscles of healthy males
No full textReduced maximal force capability of skeletal muscle, as a consequence of exercise, can be due to peripheral or central fatigue mechanisms. In upper-limb muscles, neuromuscular fatigue is concurrent with reduced corticospinal excitability and increased inhibition (lengthened corticospinal silent period [CSP]; reduced shortinterval intracortical inhibition [SICI] ratio). However, it is unclear whether these adjustments occur in response to fatiguing exercise of locomotor muscles. This study examined the effect of fatiguing, maximal, knee-extensor exercise on motor cortical excitability and inhibition. Thirteen males performed three 30 s maximal, isometric contractions with the dominant knee-extensors (MVC1, MVC2 and MVC3), separated by 60 s. At the end of, and between each MVC, neuromuscular fatigue, corticospinal excitability, CSP and SICI were assessed with supramaximal stimulation of the femoral
nerve, and motor cortical stimulation, respectively. Repeated MVCs caused progressive reductions in MVC (−10, −24 and −29%, respectively, P≤0.01), along with significant peripheral (reductions in potentiated twitch of −23, −53 and −60%, respectively, P<0.001) and central (reductions in VA of −10% and −13% post-MVC2 and 3 respectively, P≤0.01) fatigue. Following MVC1 corticospinal excitability was reduced, and remained depressed thereafter. CSP increased in duration and
remained longer throughout the protocol, whereas, no change in SICI was observed.
Repeated, sustained, maximal contractions of the knee-extensors elicited substantial peripheral and central fatigue that was accompanied by a concomitant reduction in corticospinal excitability. However, divergent responses exist between inhibitory networks within the motor cortex, the activity of inhibitory networks mediated by GABAB are increased, whereas those mediated by GABAA are not
The plasma bioavailability of nitrate and betanin from Beta vulgaris rubra in humans
No full textPurpose
To evaluate the plasma bioavailability of betanin and nitric oxide (NOx) after consuming beetroot juice (BTJ) and whole beetroot (BF). BTJ and BF were also analysed for antioxidant capacity, polyphenol content (TPC) and betalain content.
Methods
Ten healthy males consumed either 250 ml of BTJ, 300 g of BF or a placebo drink, in a randomised, crossover design. Venous plasma samples were collected pre (baseline), 1, 2, 3, 5 and 8 h post-ingestion. Betanin content in BTJ, BF and plasma was analysed with reverse-phase high-performance liquid chromatography (HPLC) and mass spectrometry detection (LCMS). Antioxidant capacity was estimated using the Trolox equivalent antioxidant capacity (TEAC) and polyphenol content using Folin–Ciocalteu colorimetric methods [gallic acid equivalents (GAE)] and betalain content spectrophotometrically.
Results
TEAC was 11.4 ± 0.2 mmol/L for BTJ and 3.4 ± 0.4 μmol/g for BF. Both BTJ and BF contained a number of polyphenols (1606.9 ± 151 mg/GAE/L and 1.67 ± 0.1 mg/GAE/g, respectively), betacyanins (68.2 ± 0.4 mg/betanin equivalents/L and 19.6 ± 0.6 mg/betanin equivalents/100 g, respectively) and betaxanthins (41.7 ± 0.7 mg/indicaxanthin equivalents/L and 7.5 ± 0.2 mg/indicaxanthin equivalents/100 g, respectively). Despite high betanin contents in both BTJ (~194 mg) and BF (~66 mg), betanin could not be detected in the plasma at any time point post-ingestion. Plasma NOx was elevated above baseline for 8 h after consuming BTJ and 5 h after BF (P < 0.05).
Conclusions
These data reveal that BTJ and BF are rich in phytonutrients and may provide a useful means of increasing plasma NOx bioavailability. However, betanin, the major betalain in beetroot, showed poor bioavailability in plasma
Transcranial magnetic stimulation in sport science: a commentary
No full textThe aim of this commentary is to provide a brief overview of transcranial magnetic stimulation (TMS) and highlight how this technique can be used to investigate the acute and chronic responses of the central nervous system to exercise.
We characterise the neuromuscular responses to TMS and discuss how these measures can be used to investigate the mechanisms of fatigue in response to locomotor exercise. We also discuss how TMS might be used to study the corticospinal adaptations to resistance exercise training, with particular emphasis on the responses to shortening/lengthening contractions and contralateral training. The limited data to date suggest that TMS is a valuable technique for exploring the mechanisms of central fatigue and neural adaptation
Quantification of exercise intensity as energy expenditure: reliability and units of measurement [commentary]
No full textThis is a commentary on Beck ON, Kipp S, Byrnes WC, Kram R. Viewpoint: Use aerobic energy expenditure instead of oxygen uptake to quantify exercise intensity and predict endurance performance.
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Effects of Strength Training on the Physiological Determinants of Middle- and Long-Distance Running Performance: A Systematic Review
No full textBackground
Middle- and long-distance running performance is constrained by several important aerobic and anaerobic parameters. The efficacy of strength training (ST) for distance runners has received considerable attention in the literature. However, to date, the results of these studies have not been fully synthesized in a review on the topic.
Objectives
This systematic review aimed to provide a comprehensive critical commentary on the current literature that has examined the effects of ST modalities on the physiological determinants and performance of middle- and long-distance runners, and offer recommendations for best practice.
Methods
Electronic databases were searched using a variety of key words relating to ST exercise and distance running. This search was supplemented with citation tracking. To be eligible for inclusion, a study was required to meet the following criteria: participants were middle- or long-distance runners with ≥ 6 months experience, a ST intervention (heavy resistance training, explosive resistance training, or plyometric training) lasting ≥ 4 weeks was applied, a running only control group was used, data on one or more physiological variables was reported. Two independent assessors deemed that 24 studies fully met the criteria for inclusion. Methodological rigor was assessed for each study using the PEDro scale.
Results
PEDro scores revealed internal validity of 4, 5, or 6 for the studies reviewed. Running economy (RE) was measured in 20 of the studies and generally showed improvements (2–8%) compared to a control group, although this was not always the case. Time trial (TT) performance (1.5–10 km) and anaerobic speed qualities also tended to improve following ST. Other parameters [maximal oxygen uptake ( V˙O2max), velocity at V˙O2max, blood lactate, body composition] were typically unaffected by ST.
Conclusion
Whilst there was good evidence that ST improves RE, TT, and sprint performance, this was not a consistent finding across all works that were reviewed. Several important methodological differences and limitations are highlighted, which may explain the discrepancies in findings and should be considered in future investigations in this area. Importantly for the distance runner, measures relating to body composition are not negatively impacted by a ST intervention. The addition of two to three ST sessions per week, which include a variety of ST modalities are likely to provide benefits to the performance of middle- and long-distance runners
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