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James Stephens and Susan Hillier

include an overview of research examining the effectiveness of the FM and identified areas where little research has been conducted. In addition, we describe research involving some of the internal processes through which the FM is thought to effect changes. We refer to this as mechanism of action

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Wolf E. Mehling

It has been suggested that improvement in bodily awareness is a key mechanism of action for many movement therapies ( Mehling et al., 2011 ). Examples of these mind–body therapies include mindful movement, integrative exercise, movement-education approaches named after or by founding teachers (e

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Vilton E.L. de Moura e Silva, Jason M. Cholewa, François Billaut, Ralf Jäger, Marcelo C. de Freitas, Fabio S. Lira, and Fabrício E. Rossi

regarding the effects of CAP on exercise performance. Therefore, the objective of this systematic review was to investigate the effects of CAP compounds as an ergogenic aid and to discuss the underlying mechanisms of action by which these supplements may potentially enhance endurance and resistance exercise

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Peter Peeling, Martyn J. Binnie, Paul S.R. Goods, Marc Sim, and Louise M. Burke

in duration. Sodium Bicarbonate Ingestion of sodium bicarbonate (NaHCO 3 ) is proposed to enhance high-intensity exercise performance as an extracellular (blood) buffer; however, the mechanisms of action are complex ( Siegler et al., 2016 ). Although playing an important role in the maintenance of

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Thomas G. Almonroeder, Lauren C. Benson, and Kristian M. O’Connor

The mechanism of action of a foot orthotic is poorly understood. The purpose of this study was to use principal components analysis (PCA) to analyze the effects of a prefabricated foot orthotic on frontal plane knee and ankle mechanics during running. Thirty-one healthy subjects performed running trials with and without a foot orthotic and PCA was performed on the knee and ankle joint angles and moments to identify the dominant modes of variation. MANOVAs were conducted on the retained principal components of each waveform and dependent t tests (P < .05) were performed in the case of significance. Mechanics of the ankle were not affected by the foot orthotic. However, mechanics of the knee were significantly altered as subjects demonstrated an increase in the magnitude of the knee abduction moment waveform in an orthotic condition. Subjects also demonstrated a significant shift in the timing of the knee abduction moment waveform toward later in the stance phase in the orthotic condition. These orthotic effects were not related to subject’s foot mobility, measured using the navicular drop test. The mechanism of action of a foot orthotic may be related to their effect on the timing of frontal plane knee loading.

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Mitchell M. Kanter and Melvin H. Williams

Three nutritional products that have very different mechanisms of action are antioxidant vitamins, carnitine, and choline. Antioxidant vitamins do not appear to have a direct effect on physical performance in well-fed people but have been touted for their ability to detoxify potentially damaging free radicals produced during exercise. Carnitine purportedly enhances lipid oxidation, increases VO2max, and decreases plasma lactate accumulation during exercise. However, studies of carnitine do not generally support its use for ergogenic purposes. Choline supplements have been advocated as a means of preventing the decline in acetylcholine production purported to occur during exercise; this decline may reduce the transmission of contraction-generating impulses across the skeletal muscle, an effect that could impair one’s ability to perform muscular work. However, there are no definitive studies in humans that justify choline supplementation. Much of the scientific data regarding the aforementioned nutrients are equivocal and contradictory. Their potential efficacy for improving physical performance remains largely theoretical.

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J. Matt Green, P. Jason Wickwire, John R. McLester, Shawn Gendle, Geoffrey Hudson, Robert C. Pritchett, and C. Matt Laurent

Context:

Ergogenic effects of caffeine on aerobic or endurance exercise are well documented. Conversely, the ergogenic value of caffeine on high-intensity, primarily anaerobic performance is not well understood even though the proposed mechanisms of action for caffeine permit a strong theoretical basis for application to this type of exercise.

Purpose:

This study examined effects of caffeine (Ca) on number repetitions (reps), ratings of perceived exertion (RPE), and peak heart rate (PHR) during resistance-training exercise with reps performed to volitional failure.

Methods:

Subjects (N = 17) were tested for 10-rep maximum in bench press (BP) and leg press (LP). In sessions 2 and 3, Ca (~6 mg/kg) or placebo (Pl) was ingested 1 hr beforehand in a double-blind manner and counterbalanced order. Subjects performed 3 sets to failure (BP and LP) with reps, PHR, and RPE recorded each set. Repeated-measures ANOVAs, 2 (trial) × 3 (set), were used to analyze dependent measures with the Tukey honestly significant difference used when necessary as the post hoc test.

Results:

In BP, no significant differences (Ca vs Pl) were observed (reps, RPE, PHR). During set 3 of LP training, Ca was associated with significantly higher reps (12.5 ± 4.2 vs 9.9 ± 2.6) and PHR (158.5 ± 11.9 vs 151.8 ± 13.2). No signifcant RPE differences were found during LP.

Conclusions:

The findings of similar RPE concurrent with higher reps suggest that caffeine can blunt pain responses, possibly delaying fatigue in high-intensity resistance training. Ergogenic effects might be limited to the later sets in a resistance-training session. Further research is warranted regarding ergogenic effects of caffeine during resistance training and potential mechanisms of action.

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Melinda M. Manore

Weight-loss supplements typically fall into 1 of 4 categories depending on their hypothesized mechanism of action: products that block the absorption of fat or carbohydrate, stimulants that increase thermogenesis, products that change metabolism and improve body composition, and products that suppress appetite or give a sense of fullness. Each category is reviewed, and an overview of the current science related to their effectiveness is presented. While some weight-loss supplements produce modest effects (<2 kg weight loss), many have either no or few randomized clinical trials examining their effectiveness. A number of factors confound research results associated with the efficacy of weight-loss supplements, such as small sample sizes, short intervention periods, little or no follow-up, and whether the supplement is given in combination with an energy-restricted diet or increased exercise expenditure. There is no strong research evidence indicating that a specific supplement will produce significant weight loss (>2 kg), especially in the long term. Some foods or supplements such as green tea, fiber, and calcium supplements or dairy products may complement a healthy lifestyle to produce small weight losses or prevent weight gain over time. Weight-loss supplements containing metabolic stimulants (e.g., caffeine, ephedra, synephrine) are most likely to produce adverse side effects and should be avoided.

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Megan A. Kuikman, Margo Mountjoy, Trent Stellingwerff, and Jamie F. Burr

Relative energy deficiency in sport (RED-S) can result in negative health and performance outcomes in both male and female athletes. The underlying etiology of RED-S is low energy availability (LEA), which occurs when there is insufficient dietary energy intake to meet exercise energy expenditure, corrected for fat-free mass, leaving inadequate energy available to ensure homeostasis and adequate energy turnover (optimize normal bodily functions to positively impact health), but also optimizing recovery, training adaptations, and performance. As such, treatment of RED-S involves increasing energy intake and/or decreasing exercise energy expenditure to address the underlying LEA. Clinically, however, the time burden and methodological errors associated with the quantification of energy intake, exercise energy expenditure, and fat-free mass to assess energy availability in free-living conditions make it difficult for the practitioner to implement in everyday practice. Furthermore, interpretation is complicated by the lack of validated energy availability thresholds, which can result in compromised health and performance outcomes in male and female athletes across various stages of maturation, ethnic races, and different types of sports. This narrative review focuses on pragmatic nonpharmacological strategies in the treatment of RED-S, featuring factors such as low carbohydrate availability, within-day prolonged periods of LEA, insufficient intake of bone-building nutrients, lack of mechanical bone stress, and/or psychogenic stress. This includes the implementation of strategies that address exacerbating factors of LEA, as well as novel treatment methods and underlying mechanisms of action, while highlighting areas of further research.

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Andrew M. Edwards and Raewyn E. Walker

The efficacy of inspiratory muscle training (IMT) has been the subject of considerable controversy in terms of whether it is beneficial to endurance athletes and because a convincing physiological rationale has not been identified to explain its mechanism of action. Early studies suggested that IMT was an ineffectual intervention for gains in either maximal aerobic power or endurance-specific performance. More rigorous recent research supports the observation that maximal aerobic power is not receptive to IMT; however, closer evaluation of both early and contemporary research indicates that responses to endurance-specific performance tests are sensitive to IMT. As the aim of endurance training is to improve endurance performance rather than maximal aerobic power, it is plausible that IMT may be useful in specific performance-related circumstances. Performance adaptations following IMT appear to be connected with post training reports of attenuated effort sensations, but this common observation has tended to be overlooked by researchers in preference for a reductionist explanation. This commentary examines the pertinent research and practical performance implications of IMT from the holistic perspective of complex central metabolic control.