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Sigridur L. Gudmundsdottir

Purpose: Insufficient sleep duration may affect athletic performance and health. Inconsistent sleep pattern also has negative health effects, but studies on athletes’ intraindividual sleep variability are scarce. The aim of this research was to compare total sleep time (TST) and variability (TST-variability), wakening after sleep onset, and sleep efficiency, during nights preceding early morning practices with other nights, and to investigate sleep characteristics of nights following a day with early morning only, evening only, or both a morning and an evening session in adolescent swimmers. Methods: Wrist-worn accelerometers were used to measure 1 week of sleep in 108 swimmers (mean age 16.1 [2.6] y) in Iceland. Adjusted regression analyses and linear mixed models were used to explore associations of training schedules with TST, TST-variability, wakening after sleep onset, and sleep efficiency. Results: Mean TST was 6:32 (h:min) (±39 min) and TST-variability was 63 minutes (±25 min). TST decreased and TST-variability increased with more early morning practices. TST preceding early training was 5:36 and 5:06 in <16- and ≥16-year-olds, respectively, shorter than on nights preceding later or no morning training (P < .001). Conclusion: Swimmers have extremely short TST preceding early morning sessions and increased TST-variability with more early morning sessions.

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Mandy Peacock, Julie Netto, Polly Yeung, Joanne McVeigh and Anne-Marie Hill

Pet ownership is associated with increased levels of physical activity (PA) in older adults. Studies have mainly focused on the association between PA and dog walking; however, broader aspects of pet ownership may influence PA. The purpose of this study was to explore the association between pet ownership and incidental and purposeful PA using a mixed methods approach. Participants’ (N = 15) PA was measured for 7 days using accelerometers and diaries. Semistructured interviews explored participants’ perspectives regarding pet-related activities. Participants’ mean (SD) daily step count was 14,204 (5,061) steps, and mean (SD) sedentary time per day was 8.76 (1.18) hr. Participants strongly concurred that their pets were an integral part of their daily lives. Incidental and purposeful PA resulted from participants undertaking pet care and socially interacting with their pets. Pets may interrupt sedentary behaviors by nudging older adults to engage in PA as part of their daily lived experience.

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Aymen Ben Othman, Mehdi Chaouachi, Issam Makhlouf, Jonathan P. Farthing, Urs Granacher, David G. Behm and Anis Chaouachi

Purpose: Whereas cross-education has been extensively investigated with adults, there are far fewer youth investigations. Two studies suggested that children had greater global responses to unilateral knee extensor fatigue and training, respectively, than adults. The objective of this study was to compare global training responses and cross-education effects after unilateral elbow flexion (EFlex) and leg press (LP) training. Methods: Forty-three prepubertal youths (aged 10–13 y) were randomly allocated into dominant LP (n = 15), EFlex (n = 15) training groups, or a control (n = 13). Experimental groups trained 3 times per week for 8 weeks and were tested pretraining and posttraining for ipsilateral and contralateral 1-repetition maximum LP; knee extensor, knee flexors, elbow flexors; and handgrip maximum voluntary isometric contractions (MVIC), and countermovement jump. Results:In comparison to no significant changes with the control group, dominant elbow flexors training demonstrated significant ( P < .001) improvements only with ipsilateral and contralateral upper body testing (EFlex MVIC [15.9–21.5%], EFlex 1-repetition maximum [22.9–50.8%], handgrip MVIC [5.5–13.8%]). Dominant LP training similarly exhibited only significant ( P < .001) improvements for ipsilateral and contralateral lower body testing (LP 1-repetition maximum [59.6–81.8%], knee extensor MVIC [12.4–18.3%], knee flexor MVIC [7.9–22.3%], and countermovement jump [11.1–18.1%]). Conclusions: The ipsilateral and contralateral training adaptations in youth were specific to upper or lower body training, respectively.

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Oladipo O. Eddo, Bryndan W. Lindsey, Shane V. Caswell, Matt Prebble and Nelson Cortes

Gait modification using real-time biofeedback is a conservative intervention associated with positive outcomes. Results from systematic reviews corroborate the effectiveness of various strategies employing real-time biofeedback for reducing estimated knee joint load. The effects on the nonmodified limb, however, remain unclear. Biomechanical changes to the nonmodified limb were investigated during unilaterally implemented medial knee thrust, lateral trunk lean, and toe-in foot progression. Nineteen healthy participants were recruited. Ten trials were completed for each gait condition including baseline. Assigned magnitude for each gait modification strategy was individualized based on the mean and SD of the gait parameter during baseline. Visual real-time biofeedback was provided. During medial knee thrust, participants’ nonmodified limb presented with increased: first peak medial knee contact force, internal first peak knee extensor moment, as well as knee- and hip-flexion angles at internal first peak knee extensor moment. Observed biomechanical changes are elucidative of the body’s attempt to attenuate increased external loads. These findings may carry significant implications for pathological populations. Load redistribution to the nonmodified side may result in unfavorable long-term outcomes particularly in patients with bilateral diagnosis. Future studies should explore acute and chronic changes in the nonmodified limb of individuals with knee osteoarthritis.

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Kristof Kipp, John Krzyszkowski and Daniel Kant-Hull

Purpose: To use an artificial neural network (ANN) to model the effect of 15 weeks of resistance training on changes in countermovement jump (CMJ) performance in male track-and-field athletes. Methods: Resistance training volume load (VL) of 21 male division I track-and-field athletes was monitored over the course of 15 weeks, which covered their indoor and outdoor competitive season. Weekly CMJ height was also measured and used to calculate the overall 15-week change in CMJ performance. A feed-forward ANN with 5 hidden layers was used to model how the VL from each of the 15 weeks was associated with the overall change in CMJ height. Results: Testing the performance of the developed ANN on 4 separate athletes showed that 15 weeks of VL data could predict individual changes in CMJ height with an average error between 0.21 and 1.47 cm, which suggested that the ANN adequately modeled the relationship between weekly VL and its effects on CMJ performance. In addition, analysis of the relative importance of each week in predicting changes in CMJ height indicated that the VLs during deload or taper weeks were the best predictors (10%–17%) of changes in CMJ performance. Conclusions: ANN can be used to effectively model the effects of weekly VL on changes in CMJ performance. In addition, ANN can be used to assess the relative importance of each week in predicting changes in CMJ height.

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Kelsie M. Full, Eileen Johnson, Michelle Takemoto, Sheri J. Hartman, Jacqueline Kerr, Loki Natarajan, Ruth E. Patterson and Dorothy D. Sears

Background: For breast cancer survivors, moderate to vigorous physical activity (MVPA) is associated with improved survival. Less is known about the interrelationships of daytime activities (sedentary behavior [SB], light-intensity physical activity, and MVPA) and associations with survivors’ health outcomes. This study will use isotemporal substitution to explore reallocations of time spent in daytime activities and associations with cancer recurrence biomarkers. Methods: Breast cancer survivors (N = 333; mean age 63 y) wore accelerometers and provided fasting blood samples. Linear regression models estimated the associations between daytime activities and cancer recurrence biomarkers. Isotemporal substitution models estimated cross-sectional associations with biomarkers when time was reallocated from of one activity to another. Models were adjusted for wear time, demographics, lifestyle factors, and medical conditions. Results: MVPA was significantly associated with lower insulin, C-reactive protein, homeostatic model assessment of insulin resistance, and glucose, and higher sex hormone-binding globulin (all P < .05). Light-intensity physical activity and SB were associated with insulin and homeostatic model assessment of insulin resistance (both P < .05). Reallocating 18 minutes of SB to MVPA resulted in significant beneficial associations with insulin (−9.3%), homeostatic model assessment of insulin resistance (−10.8%), glucose (−1.7%), and sex hormone-binding globulin (7.7%). There were no significant associations when 79 minutes of SB were shifted to light-intensity physical activity. Conclusions: Results illuminate the possible benefits for breast cancer survivors of replacing time spent in SB with MVPA.

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Stefanie Klatt and Nicholas J. Smeeton

In 2 experiments, the authors investigated the effects of bimodal integration in a sport-specific task. Beach volleyball players were required to make a tactical decision, responding either verbally or via a motor response, after being presented with visual, auditory, or both kinds of stimuli in a beach volleyball scenario. In Experiment 1, players made the correct decision in a game situation more often when visual and auditory information were congruent than in trials in which they experienced only one of the modalities or incongruent information. Decision-making accuracy was greater when motor, rather than verbal, responses were given. Experiment 2 replicated this congruence effect using different stimulus material and showed a decreasing effect of visual stimulation on decision making as a function of shorter visual stimulus durations. In conclusion, this study shows that bimodal integration of congruent visual and auditory information results in more accurate decision making in sport than unimodal information.

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Geoffrey T. Burns, Kenneth M. Kozloff and Ronald F. Zernicke

Movement is essential to the human experience, and efficient biomechanics facilitate effective action across the breadth of tasks one encounters in life. The concept of movement efficiency has been investigated and explored through a variety of means including biomechanical modeling, simulation, and experimental manipulation. Observations of elite performers for a given movement task serve as an additional line of insight into efficiency, as their movements have been driven toward optimization via competitive pressure. The authors first discuss the concept of efficiency in biomechanics from a qualitative perspective and the broad tools with which we explore it. They then highlight biomechanical investigations of elite performers and their contributions to our understanding of efficiency. Examples from various classes of movements illustrate unique insights of the elite performers in informing our understanding of movement efficiency.

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Mark Eys, Mark R. Beauchamp, Michael Godfrey, Kim Dawson, Todd M. Loughead and Robert J. Schinke

The objectives of this study were to (a) develop a conceptualization of role acceptance, later situated within the broader concept of role commitment, pertinent to the sport environment; (b) develop a measure integrating direct perceptions of role commitment and the bases of this variable; and (c) determine if role commitment could predict athletes’ intentions to return. To accomplish these objectives, multiple methods were used across 4 projects that leveraged the extant literature on acceptance and commitment perceptions from sport and organizational psychology, engaged athletes in focus groups in a think-aloud protocol, and obtained responses on iterative versions of a new role-commitment questionnaire from over 700 athletes from a variety of competitive and developmental levels. Overall, this approach captured the bases of role commitment (affective, normative, and continuance perspectives), as well as direct perceptions of role commitment, and demonstrated an important link to intentions to return to sport.