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Ivan A. Trujillo-Priego, Judy Zhou, Inge F. Werner, Weiyang Deng and Beth A. Smith

Wearable sensors are being used to measure intensity of infant physical activity across full days. The variability of infant activity intensity within and across days is important to study given the potential impact of physical activity on developmental trajectories. Using retrospective data, we analyzed the intensity of leg movements in 10 typically developing infants pre- and post-naptimes. Leg movement data were captured from 20 minutes before and after multiple events of naps across seven days for each infant. We hypothesized that leg movement intensity would be lower before a nap than after a nap potentially due to lower arousal and increased fatigue prior to attaining sleep. However, our results showed that leg movement intensity was not significantly different when comparing the 20-minute period pre- and post-naps (F(1,7) = 3.91, p = .089, ηp2=0.358). Our results are a first step in describing patterns of infant activity across days and highlights the need for further research regarding infant energy expenditure and physical activity.

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Arthur H. Bossi, Cristian Mesquida, Louis Passfield, Bent R. Rønnestad and James G. Hopker

Purpose: Maximal oxygen uptake (V˙O2max) is a key determinant of endurance performance. Therefore, devising high-intensity interval training (HIIT) that maximizes stress of the oxygen-transport and -utilization systems may be important to stimulate further adaptation in athletes. The authors compared physiological and perceptual responses elicited by work intervals matched for duration and mean power output but differing in power-output distribution. Methods: Fourteen cyclists (V˙O2max 69.2 [6.6] mL·kg−1·min−1) completed 3 laboratory visits for a performance assessment and 2 HIIT sessions using either varied-intensity or constant-intensity work intervals. Results: Cyclists spent more time at >90%V˙O2max during HIIT with varied-intensity work intervals (410 [207] vs 286 [162] s, P = .02), but there were no differences between sessions in heart-rate- or perceptual-based training-load metrics (all P ≥ .1). When considering individual work intervals, minute ventilation (V˙E) was higher in the varied-intensity mode (F = 8.42, P = .01), but not respiratory frequency, tidal volume, blood lactate concentration [La], ratings of perceived exertion, or cadence (all F ≤ 3.50, ≥ .08). Absolute changes (Δ) between HIIT sessions were calculated per work interval, and Δ total oxygen uptake was moderately associated with ΔV˙E (r = .36, P = .002). Conclusions: In comparison with an HIIT session with constant-intensity work intervals, well-trained cyclists sustain higher fractions of V˙O2max when work intervals involved power-output variations. This effect is partially mediated by an increased oxygen cost of hyperpnea and not associated with a higher [La], perceived exertion, or training-load metrics.

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Erik Trøen, Bjarne Rud, Øyvind Karlsson, Camilla Høivik Carlsen, Matthias Gilgien, Gøran Paulsen, Ola Kristoffer Tosterud and Thomas Losnegard

Purpose: To investigate how self-selected pole length (PL) of ∼84% (PL84%) compared with ∼90% (PL90%) of body height influenced performance during a 700-m time trial with undulating terrain on snow. Methods: Twenty-one cross-country skiers, 7 of whom were women, performed 4 trials at a maximal effort in a counterbalanced fashion with PL84% and PL90% separated by 20-minute breaks between trials. In trials I and II, only double poling was allowed, while in trials III and IV, skiers used self-selected classical subtechniques. Continuous speed, cyclic parameters, and heart rate were collected using microsensors in addition to a post-time-trial rating of perceived exertion (RPE). Results: The 700-m times with only double poling were significantly shorter with PL90% than PL84% (mean ± 95% confidence limits –1.6% ± 1.0%). Segment analyses showed higher speed with PL90% in uphill sections than with PL84% (3.7% ± 2.1%), with the greatest difference found for the female skiers (5.6% ± 2.9%). In contrast, on flat terrain at high skiing speeds, speed was reduced with PL90% compared with PL84% (–1.5% ± 1.4%); this was only significant for the male skiers. During free choice of classical subtechniques, PL did not influence performance in any segments, choice of subtechnique, or cycle rate during the trials. No differences in rating of perceived exertion or heart rate between PLs were found. Conclusions: PL90% improved performance in uphills at low speeds when using double poling but hindered performance on flat terrain and at higher speeds compared with self-selected PLs. Choice of PL should, therefore, be based on racecourse topography, preferred subtechniques, and the skier’s physiological and technical abilities.

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Lorenzo Lolli, Alan M. Batterham, Gregory MacMillan, Warren Gregson and Greg Atkinson

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Jos J. de Koning

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Irene Torres-Sánchez, Araceli Ortiz-Rubio, Irene Cabrera-Martos, María Granados-Santiago, Isabel López-Torres and Marie Carmen Valenza

Background: Growing evidence demonstrates the negative health impact of physical inactivity. Our aim was to examine the influence of previous-year physical activity (PA) on the cognition of chronic obstructive pulmonary disease (COPD) patients during exacerbation. Methods: Observational study. One hundred and fifty-one patients with COPD exacerbation were recruited over a period of 3 years and divided in 2 groups according to their previous activity level. Sociodemographic, anthropometric, and clinical variables were collected. Our main outcome measures were previous-year PA level, measured using the Modified Baecke Physical Activity Questionnaire and cognitive status measured using the Montreal Cognitive Assessment. Results: The cognitive variables that exhibited significant differences (P < .05) according to PA level were the visuoconstructional skills subscore, attention subscore, language subscore, orientation subscore, and Montreal Cognitive Assessment total score, with worse results in the sedentary group. Based on the relationships between total scores, the Baecke score was positively correlated with the Montreal Cognitive Assessment total score (r = .457). Conclusions: The cognitive status of COPD patients during an exacerbation is related to previous-year PA level. Previous-year PA level should be taken into consideration when patients with a COPD exacerbation are evaluated.

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Meg E. Letton, Jeanette M. Thom and Rachel E. Ward

Background: Regular physical activity is of paramount importance to reduce chronic disease risk. Classical ballet training requires balance, strength, and range of motion. Participation in social ballet classes is increasing. Ballet training interventions may be an alternative method of regular, enjoyable activity. This review aimed to determine the effectiveness of classical ballet training interventions on physical and psychological health. Methods: Ten databases were searched until April 2019. The included studies investigated classical ballet training interventions of a ≥4-week duration, on any population (no restrictions on experience and clinical condition), measuring physical health or psychological outcomes. Results: Twenty-three studies (25 intervention groups) were included, comprising experienced (19 groups) and novice dancers (6 groups). In experienced populations, muscular strength was the most commonly reported outcome. However, only 25% of these studies reported improvements. With novice dancers, including clinical populations, balance showed the most positive change, improving in 75% of studies that reported this measure. Conclusions: Classical ballet training may improve balance in novices and maintain physical activity across the life span. Experienced dancers showed no further improvement, perhaps due to an already greater ability. There was large heterogeneity between the included studies. A greater focus on classical ballet interventions for inexperienced populations is required.

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Sergio Estrada-Tenorio, José A. Julián, Alberto Aibar, José Martín-Albo and Javier Zaragoza

Background: School environment provides several intervention opportunities for physical activity. The aim of this study was to examine the relationship between objectively assessed moderate to vigorous physical activity (MVPA) and academic achievement in adolescents. Methods: Cross-sectional data were collected from 301 students aged between 13 and 15 years (46.51% boys), enrolled at 7 secondary schools in the city of Huesca (Spain). Participants wore accelerometers during a 7-day period, and their academic achievement was calculated from the average marks of all subjects. Structural equation modeling and quadratic regression analysis were performed to test both linear and nonlinear explanatory models. One-way analysis of variance was also performed to explore the effect of gender and the percentage of compliance with MVPA recommendations. Results: MVPA on weekdays and higher levels of body mass index were negatively associated with academic achievement. According to the curvilinear relationship, those students whose MVPA levels were closer to the daily recommendation were more likely to obtain higher academic achievement. However, a significant association was only shown in the case of boys. Conclusions: Adolescents who satisfy the international recommendations tend to obtain better academic achievement. Therefore, MVPA for adolescents should be prescribed within some beneficial time margins (50–70 min/d).

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Anderson Nascimento Guimarães, Herbert Ugrinowitsch, Juliana Bayeux Dascal, Alessandra Beggiato Porto and Victor Hugo Alves Okazaki

According to Bernstein, the central nervous system solution to the human body’s enormous variation in movement choice and control when directing movement—the problem of degrees of freedom (DF)—is to freeze the number of possibilities at the beginning of motor learning. However, different strategies of freezing DF are observed in literature, and the means of selection of the control strategy during learning is not totally clear. This review investigated the possible effects of the class and objectives of the skill practiced on DF control strategies. The results of this review suggest that freezing or releasing the DF at the beginning of learning does not depend on the class (e.g., discrete skill class: football kick, dart throwing; continuous skill class: athletic march, handwriting) or objective of the skill (e.g., balance, velocity, and accuracy), in isolation. However, an interaction between these two skill elements seems to exist and influences the selection of the DF control strategy.