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Franco M. Impellizzeri, Matthew S. Tenan, Tom Kempton, Andrew Novak and Aaron J. Coutts

The number of studies examining associations between training load and injury has increased exponentially. As a result, many new measures of exposure and training-load-based prognostic factors have been created. The acute:chronic workload ratio (ACWR) is the most popular. However, when recommending the manipulation of a prognostic factor in order to alter the likelihood of an event, one assumes a causal effect. This introduces a series of additional conceptual and methodological considerations that are problematic and should be considered. Because no studies have even tried to estimate causal effects properly, manipulating ACWR in practical settings in order to change injury rates remains a conjecture and an overinterpretation of the available data. Furthermore, there are known issues with the use of ratio data and unrecognized assumptions that negatively affect the ACWR metric for use as a causal prognostic factor. ACWR use in practical settings can lead to inappropriate recommendations, because its causal relation to injury has not been established, it is an inaccurate metric (failing to normalize the numerator by the denominator even when uncoupled), it has a lack of background rationale to support its causal role, it is an ambiguous metric, and it is not consistently and unidirectionally related to injury risk. Conclusion: There is no evidence supporting the use of ACWR in training-load-management systems or for training recommendations aimed at reducing injury risk. The statistical properties of the ratio make the ACWR an inaccurate metric and complicate its interpretation for practical applications. In addition, it adds noise and creates statistical artifacts.

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Rob Millington, Lyndsay M.C. Hayhurst, Audrey R. Giles and Steven Rynne

Over the past two decades, significant policy shifts within Canada have urged corporations from all sectors, including the extractives industry, to fund and support sport for development (SFD) programming in Indigenous communities, often through corporate social responsibility strategies. The idea that sport is an appropriate tool of development for Indigenous communities in Canada and that the extractives industry is a suitable partner to implement development programs highlight profound tensions regarding ongoing histories of resource extraction and settler colonialism. To explore these tensions, in this paper, the authors drew on interviews conducted with extractives industry representatives of four companies that fund and implement such SFD programs. From these interviews, three overarching discourses emerged in relation to the extractives industry’s role in promoting development through sport: SFD is a catalyst to positive relationships between industry and community, SFD is a contributor to “social good” in Indigenous communities, and extractives industry funding of SFD is “socially responsible.”

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Dawn E. Trussell

This interpretative study examines the complexities of lesbian parents’ experiences in organized youth sport programs. Specifically, it seeks to understand youth sport as a potential site for social change that facilitates a sense of inclusive community for diverse family structures. Using thematic analysis, the author examines perspectives of nine participants from Australia, Canada, and the United States. Emphasis is placed on how the lesbian parents (a) negotiate heightened visibility, sexual stigma, and parental judgment; (b) foster social relationships through participation, volunteerism, and positive role models; and (c) create shared understanding toward building an inclusive sport culture. The findings call attention to the importance of intentional and unintentional acts (by families as well as sport organizations) that create a sense of community and an inclusive organizational culture. The connection of lesbian parents’ experiences to broader concepts, such as sexual stigma and transformative services, are also examined within the context of youth sport.

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Jerraco L. Johnson, Peter A. Hastie, Mary E. Rudisill and Danielle Wadsworth

The purpose of this study was to determine the extent to which preschool boys’ and girls’ gender and skill level relate to their throwing practice behaviors during a mastery motivational climate intervention. Fifty-four preschool children (24 boys, 30 girls) participated in a 7-week FMS intervention. Children’s practice behaviors (number of visits, total time, and total trials) at the overhand throwing station were video recorded during each session. A series of unpaired Welch assessments were run to determine if there were differences in practice behaviors across the intervention based on gender and initial skill level. Results indicated significant differences in practice time and trials based on gender and skill level, but no differences in the number of visits. It appears that throwing gender stereotypes perhaps may be related to practice behaviors for young children. Interventions should consider ways to make throwing more enticing for young girls and less skilled children to encourage practice and enhance learning.

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Tarkington J. Newman, Fernando Santos, António Cardoso and Paulo Pereira

Coaches’ role in positive youth development (PYD) has been extensively studied around the globe. Coach education has been considered crucial in helping foster PYD outcomes, such as emotional regulation, goal setting, and leadership. Thus, several researchers have attempted to provide a comprehensive understanding about how experiential learning could be utilized within PYD-focused coach education programs. The purpose of this article was to provide insight on the implications for research and practice associated with the integration of experiential learning opportunities within PYD-focused coach education. The authors shed light on how the existent literature on experiential learning may help bridge the gap between the delivery of PYD-focused coach education programs and actual coaching practices. Implications for research and practice are discussed in order to provide insight on how PYD-focused coach education programs could be configured to effectively train coaches and enhance their ability to promote PYD outcomes, such as life skill development, among youth athletes across a range of contexts.

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Emerson Franchini

Context: Combat sports are composed of high-intensity actions (eg, attacks, defensive actions, and counterattacks in both grappling and striking situations depending on the specific sport) interspersed with low-intensity actions (eg, displacement without contact, stepping) or pauses (eg, referee stoppages), characterizing an intermittent activity. Therefore, high-intensity interval training (HIIT) is at the essence of combat-sport-specific training and is used as complementary training, as well. HIIT prescription can be improved by using intensity parameters derived from combat-sport-specific tests. Specifically, the assessment of physiological indexes (intensity associated with the maximal blood lactate steady state, maximal oxygen consumption, and maximal sprint) or of time–motion variables (high-intensity actions, low-intensity actions, and effort:pause ratio) is a key element for a better HIIT prescription because these parameters provide an individualization of the training loads imposed on these athletes. Purpose: To present a proposal for HIIT prescription for combat-sport athletes, exemplifying with different HIIT protocols (HIIT short intervals, HIIT long intervals, repeated-sprint training, and sprint interval training) using combat-sport-specific actions and the parameters for the individualization of these protocols. Conclusions: The use of combat-sport-specific tests is likely to improve HIIT prescription, allowing coaches and strength and conditioning professionals to elaborate HIIT short intervals, HIIT long intervals, repeated-sprint training, and sprint interval training protocols using combat-sport actions, providing more specificity and individualization for the training sessions.

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Christopher Kevin Wong, Lizbeth Conway, Grant Fleming, Caitlin Gopie, Dara Liebeskind and Stephen Xue

Clinical Scenario: Many people with lower quarter musculoskeletal dysfunction present with muscle weakness. Strength training hypertrophies muscle and increases strength, but often requires periods over 6 weeks, which can exceed the episode of care. Weakness can persist despite muscle hypertrophy, particularly in the early stages of joint pathology or in the presence of limb or spinal joint hypomobility, which may inhibit muscle activation. Emerging evidence suggests spinal manipulation can increase short-term strength. Screening for specific muscle weakness that could benefit from manipulation to particular spinal segments could facilitate efficient clinical intervention. Although the neuromuscular mechanisms through which manipulation can increase strength remains a topic of investigation, immediate gains can benefit patients by jump-starting an exercise program to train new muscle function gained and enhancing the motivation to continue strengthening. Evidence from randomized controlled trials would provide support for using manipulation to increase muscle strength, while studying healthy people would eliminate confounding factors, such as pain and pathology. Clinical Question: Does randomized controlled trial-level evidence support the concept that a single lumbar spine manipulation session can increase lower-limb strength in healthy individuals? Summary of Key Findings: Level 1b evidence of moderate quality from 3 randomized controlled trials showed immediate small to large effect size muscle strength increases immediately after lumbar spine manipulation. Clinical Bottom Line: Lumbar spine manipulation can result in immediate lower-limb isometric strength increases. While healthy people with normal muscle strength may improve minimally, joint manipulation for people with knee and hip weakness who are otherwise healthy can result in large effect size strength gains. Strength of Recommendation: Moderate quality level 1b evidence from randomized controlled trials with small samples support the use of spinal manipulation to immediately increase lower-limb strength. Additional studies investigating impact on strength and function immediately in people with musculoskeletal pathology are warranted.

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Miguel A. Sanchez-Lastra, Kyle J. Miller, Rodolfo I. Martínez-Lemos, Antón Giráldez and Carlos Ayán

Background: Nordic walking (NW) is a potentially beneficial exercise strategy for overweight and obese people. To date, no reviews have synthesized the existing scientific evidence regarding the effects of NW on this population. This systematic review and meta-analysis aimed to identify the characteristics, methodological quality, and results of the investigations that have studied the effects of NW in overweight and obese individuals. Methods: Six electronic databases were searched up to June 2019 for studies that examined the effects of NW on people with a body mass index ≥ 25 kg/m2. The methodological quality of the included randomized controlled trials was retrieved from the physiotherapy evidence database or evaluated using the physiotherapy evidence database scale. Results: Twelve studies were included in the review. The investigations were mostly good-to-fair methodological quality. NW groups had a significant improvement on parameters such as fasting plasma glucose, abdominal adiposity, and body fat compared with the baseline, but no significant improvements were found when compared with control groups. Conclusions: NW can potentially lead to improvements in parameters related to major health outcomes in overweight and obese people. The lack of control for confounding variables in the analyzed studies prevents further elaboration on its potential benefits.

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Rebecca L. Krupenevich, William H. Clark, Gregory S. Sawicki and Jason R. Franz

Ankle joint quasi-stiffness is an aggregate measure of the interaction between triceps surae muscle stiffness and Achilles tendon stiffness. This interaction may be altered due to age-related changes in the structural properties and functional behavior of the Achilles tendon and triceps surae muscles. The authors hypothesized that, due to a more compliant of Achilles’ tendon, older adults would exhibit lower ankle joint quasi-stiffness than young adults during walking and during isolated contractions at matched triceps surae muscle activations. The authors also hypothesized that, independent of age, triceps surae muscle stiffness and ankle joint quasi-stiffness would increase with triceps surae muscle activation. The authors used conventional gait analysis in one experiment and, in another, electromyographic biofeedback and in vivo ultrasound imaging applied during isolated contractions. The authors found no difference in ankle joint quasi-stiffness between young and older adults during walking. Conversely, this study found that (1) young and older adults modulated ankle joint quasi-stiffness via activation-dependent changes in triceps surae muscle length–tension behavior and (2) at matched activation, older adults exhibited lower ankle joint quasi-stiffness than young adults. Despite age-related reductions during isolated contractions, ankle joint quasi-stiffness was maintained in older adults during walking, which may be governed via activation-mediated increases in muscle stiffness.

Open access

Bryan McCullick