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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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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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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.

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Vincent Shieh, Ashwini Sansare, Minal Jain, Thomas Bulea, Martina Mancini and Cris Zampieri

Aims: Clinical evaluation of balance has relied on forceplate systems as the gold standard for postural sway measures. Recently, systems based on wireless inertial sensors have been explored, mostly in the adult population, as an alternative given their practicality and lower cost. Our goal was to validate body-worn sensors against forceplate balance measures in typically developing children during tests of quiet stance. Methods: 18 participants (8 males) 7 to 17 years old performed a quiet stance test standing on a forceplate while wearing 3 inertial sensors. Three 30-second trials were performed under 4 conditions: firm surface with eyes open and closed, and foam surface with eyes open and closed. Sway area, path length, and sway velocity were calculated. Results: We found 20 significant and 8 non-significant correlations. Variables found to be significant were represented across all conditions, except for the foam eyes closed condition. Conclusions: These results support the validity of wearable sensors in measuring postural sway in children. Inertial sensors may represent a viable alternative to the gold standard forceplate to test static balance in children.

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Christina Zong-Hao Ma, Wing-Kai Lam, Bao-Chi Chang and Winson Chiu-Chun Lee

This systematic review investigated the effects of orthopedic, vibrating, and textured insoles on the postural balance of community-dwelling older adults. Articles published in English from 1999 to 2019 investigating the effects of (a) orthopedic, (b) vibrating, and (c) textured insoles on static and dynamic balance in community-dwelling older adults were considered. Twenty-four trials with a total of 634 older adults were identified. The information gathered generally supported the balance-improving effects of orthopedic, vibrating, and textured insoles in both static and dynamic conditions among community-dwelling older adults. Further examination found that rigidity, texture patterns, vibration thresholds, and components like arch supports and heel cups are important factors in determining whether insoles can improve balance. This review highlights the potential of insoles for improving the static and dynamic balance of community-dwelling older adults. Good knowledge in insole designs and an understanding of medical conditions of older adults are required when attempts are made to improve postural balance using insoles.

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Cassidy Preston, Veronica Allan, Lauren Wolman and Jessica Fraser-Thomas

Extensive research highlights the important roles of coaches and parents in fostering positive youth development (PYD). However, little research has examined the complex coach–parent relationship in the bidirectional interactions of the coach-parent-athlete triad. This research is particularly pertinent in elite youth sport, wherein the performance-oriented environment may impede the pursuit of PYD. As such, this study aimed to deepen understandings of the coach–parent relationship in relation to athletes’ PYD. Specifically, the first author critically analyzed and reflected on his experiences as an elite youth ice hockey coach, thus offering a unique portrayal of reflective practice in the context of sport coaching. Two interconnected themes emerged: understanding conflict in the coach-parent-athlete relationship and fostering collaboration through enhanced coach–parent communication. Findings and reflections are discussed in relation to the dual-concern model of conflict resolution, and strategies to help practitioners foster cooperative coach–parent relationships are presented.

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Dereck L. Salisbury and Fang Yu

The purpose of this study was to investigate the relationships among peak exercise parameters on 6-min walk test, shuttle walk test, and laboratory-based cardiopulmonary exercise testing in persons with Alzheimer’s dementia. This study is a cross-sectional analysis of the baseline data of 90 participants (age 77.1 [6.6] years, 43% female) from the FIT-AD trial. Cardiopulmonary exercise testing produced significantly higher peak heart rate (118.6 [17.5] vs. 106 [22.8] vs. 106 [18.8] beats/min), rating of perceived exertion (16 [2.1] vs. 12 [2.3] vs. 11 [2.1]), and systolic blood pressure (182 [23.7] vs. 156 [18.9] vs. 150 [16.9] mmHg) compared with the shuttle walk test and 6-min walk test, respectively. Peak walking distance on shuttle walk test (241.3 [127.3] m) and 6-min walk test (365.0 [107.9] m) significantly correlated with peak oxygen consumption (17.1 [4.3] ml·kg−1·min−1) on cardiopulmonary exercise testing (r = .449, p ≤ .001 and r = .435, p ≤ .001), respectively, which is considerably lower than what is seen in older adults and persons with cardiopulmonary diseases.