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Mu Qiao

Although the dynamics of center of mass can be accounted for by a spring-mass model during hopping, less is known about how each leg joint (ie, hip, knee, and ankle) contributes to center of mass dynamics. This work investigated the function of individual leg joints when hopping unilaterally and vertically at 4 frequencies (ie, 1.6, 2.0, 2.4, and 2.8 Hz). The hypotheses are (1) all leg joints maintain the function as torsional springs and increase their stiffness when hopping faster and (2) leg joints are controlled to maintain the mechanical load in the joints or vertical peak accelerations at different body locations when hopping at different frequencies. Results showed that all leg joints behaved as torsional springs during low-frequency hopping (ie, 1.6 Hz). As hopping frequency increased, leg joints changed their functions differently; that is, the hip and knee shifted to strut, and the ankle remained as spring. When hopping fast, the body’s total mechanical energy decreased, and the ankle increased the amount of energy storage and return from 50% to 62%. Leg joints did not maintain a constant load at the joints or vertical peak accelerations at different body locations when hopping at different frequencies.

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Joffrey Drigny, Marine Rolland, Robin Pla, Christophe Chesneau, Tess Lebreton, Benjamin Marais, Pierre Outin, Sébastien Moussay, Sébastien Racinais, and Benoit Mauvieux

Purpose: To measure core temperature (T core) in open-water (OW) swimmers during a 25-km competition and identify the predictors of T core drop and hypothermia-related dropouts. Methods: Twenty-four national- and international-level OW swimmers participated in the study. Participants completed a personal questionnaire and a body fat/muscle mass assessment before the race. The average speed was calculated on each lap over a 2500-m course. T core was continuously recorded via an ingestible temperature sensor (e-Celsius, BodyCap). Hypothermia-related dropouts (H group) were compared with finishers (nH group). Results: Average prerace T core was 37.5°C (0.3°C) (N = 21). 7 participants dropped out due to hypothermia (H, n = 7) with a mean T core at dropout of 35.3°C (1.5°C). Multiple logistic regression analysis found that body fat percentage and initial T core were associated with hypothermia (G 2 = 17.26, P < .001). Early T core drop ≤37.1°C at 2500 m was associated with a greater rate of hypothermia-related dropouts (71.4% vs 14.3%, P = .017). Multiple linear regression found that body fat percentage and previous participation were associated with T core drop (F = 4.95, P = .019). There was a positive correlation between the decrease in speed and T core drop (r = .462, P < .001). Conclusions: During an OW 25-km competition at 20°C to 21°C, lower initial T core and lower body fat, as well as premature T core drop, were associated with an increased risk of hypothermia-related dropout. Lower body fat and no previous participation, as well as decrease in swimming speed, were associated with T core drop.

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Oliver W.A. Wilson, Michael J. Panza, M. Blair Evans, and Melissa Bopp

Background: The purpose of this scoping review was to critically examine the design and quality of contemporary research involving college student physical activity participation, focusing on physical activity measurement, assessment of sociodemographic characteristics, and examination of inequities based on sociodemographic characteristics. Methods: Systematic searches were conducted in 4 electronic databases. Results: From 28,951 sources screened, data were extracted from 488 that met the inclusion criteria. The majority of the studies were cross-sectional in design (91.4%) and employed convenience sampling methods (83.0%). Based on the subsample of studies that reported the percentage of students meeting aerobic (n = 158; equivalent of 150 min/wk of moderate physical activity) and muscle-strengthening activity recommendations (n = 8; ≥2 times/wk), 58.7% and 47.8% of students met aerobic and muscle-strengthening recommendations, respectively. With the exception of age and sex, sociodemographic characteristics were rarely assessed, and inequities based upon them were even more scarcely examined—with no apparent increase in reporting over the past decade. Conclusions: College student physical activity levels remain concerningly low. The generalizability of findings from the contemporary literature is limited due to study design, and acknowledgement of the influence that sociodemographic characteristics have on physical activity has largely been overlooked. Recommendations for future research directions and practices are provided.

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Mary E. Medysky, Kelcey A. Bland, Sarah E. Neil-Sztramko, Kristin L. Campbell, Donald R. Sullivan, and Kerri M. Winters-Stone

The authors systematically reviewed and summarized exercise trials in persons with lung cancer on (a) attention to the principles of exercise training (specificity, progression, overload, initial values, reversibility, and diminishing returns); (b) methodological reporting of FITT (frequency, intensity, time, and type) components; and (c) reporting on participant adherence to prescribed FITT. Randomized controlled trials of exercise that reported on ≥1 physical fitness, physical function, or body composition outcome in persons with lung cancer were included. Of 20 trial arms, none incorporated all principles of exercise training. Specificity was included by 95%, progression by 45%, overload by 75%, and initial values by 80%, while one trial arm applied reversibility and diminishing returns. Fourteen interventions reported all FITT components; however, none reported adherence to each component. Including the principles of training and reporting FITT components will contribute to better understanding of the efficacy of exercise for persons with lung cancer and inform evidence-based exercise prescriptions.

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Nathálya Gardênia de Holanda Marinho Nogueira, Bárbara de Paula Ferreira, Fernanda Veruska Narciso, Juliana Otoni Parma, Sara Edith Souza de Assis Leão, Guilherme Menezes Lage, and Lidiane Aparecida Fernandes

This study investigated the influence of chronotype on motor behavior in a manual dexterity task performed at different times of the day. Sixteen healthy adults of each chronotype (morning, evening, and neither), as measured by the Morningness–Eveningness Questionnaire, practiced both conditions of the Grooved Pegboard Test either in the morning or in the afternoon to early evening. The “neither” chronotype (65.12 ± 7.46) was outperformed (ps ≤ .03) by both the morning (56.09 ± 7.21) and evening (58.94 ± 7.53) chronotypes when the task had higher cognitive and motor demand but was not outperformed in the task with lower demand (morning = 18.46 ± 2.11; evening = 19.34 ± 2.79; neither = 21.47 ± 2.54; p > .05). No difference between the morning and evening chronotypes was found at the different times of the day (ps > .05), suggesting that a manual dexterity task is not sufficiently demanding to be influenced by chronotype.

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Victoria Sanborn, Lauren Todd, Hanna Schmetzer, Nasha Manitkul-Davis, John Updegraff, and John Gunstad

Anxiety and depressive symptoms are prevalent in athletes. The pandemic of novel coronavirus (COVID-19) may increase risk for symptoms due to fear of exposure during competition or uncertainty regarding participation. The current study examined the prevalence of COVID-19 anxiety in 437 National Collegiate Athletic Association Division I student-athletes and its association with psychological symptoms. Only 0.2% of participants endorsed COVID-19 anxiety symptoms above cutoff. COVID-19 anxiety did not change after postponement of fall sports or differ between persons competing in different seasons. However, higher levels of COVID-19 anxiety were significantly associated with depression, anxiety, and stress. Though student-athletes generally reported low levels of psychological symptoms, females endorsed significantly higher levels than males. Low levels of COVID-19 anxiety in student-athletes may reflect protective factors (e.g., health knowledge, emotion regulation) or the tendency for this population to minimize psychological symptoms. Further investigations on the psychological impact of COVID-19 in athletes is needed.

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Sangsoo Park, Richard Van Emmerik, and Graham E. Caldwell

The aim of this study was to describe how major leg muscle activities are altered after learning a novel one-legged pedaling task. Fifteen recreational cyclists practiced one-legged pedaling trials during which they were instructed to match their applied pedal force to a target direction perpendicular to the crank arm. Activity in 10 major leg muscles was measured with surface electromyography electrodes. Improved upstroke task performance was obtained by greater activity in the hip and ankle flexor muscles, counteracting the negative effects of gravity. Greater quadriceps activities explained improved targeting near top dead center. Reduced uniarticular knee and ankle extensor downstroke activities were necessary to prevent freewheeling. Greater hamstring and tibialis anterior activities improved targeting performance near the bottom of the pedal stroke. The activity patterns of the biarticular plantarflexors changed little, likely due to their contributions as knee flexors for smooth upstroke pedaling motion. These results add to our understanding of how the degrees of freedom at the muscle level are altered in a cooperative manner to overcome gravitational effects in order to achieve the learning goal of the motor task while satisfying multiple constraints—in this case, the production of smooth one-legged pedaling motion at the designated mechanical task demands.

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Marco Meucci, Vibhav Nandagiri, Venkata S. Kavirayuni, Alexander Whang, and Scott R. Collier

Purpose: To investigate the association between the heart rate (HR) at maximal fat oxidation (MFO) and the HR at the aerobic threshold (AerT) in adolescent boys and girls, and to identify sex differences in the intensity that elicits MFO (Fatmax) as a percentage of HR peak (HRpeak). Methods: Fifty-eight healthy adolescents participated in this study (29 boys and 29 girls). Participants performed a cardiopulmonary exercise test on a cycle ergometer. MFO was calculated using a stoichiometric equation, and the AerT was identified using gas exchange parameters. Results: A strong correlation between HR at Fatmax and HR at AerT was found in both boys and girls (r = .96 and .94, respectively). Fatmax as a percentage of HRpeak occurred at 61.0% (4.9%) of HRpeak and 66.8% (6.9%) of HRpeak in adolescent boys and girls (P = .001, F = 13.6), respectively. MFO was higher in boys compared with girls (324 [150] and 240 [95] mg/min, respectively), and no sex differences were observed in the relative contribution of fat to energy expenditure at Fatmax. Conclusions: HR at Fatmax and HR at AerT were highly correlated in adolescent boys and girls. Girls obtained Fatmax at a higher percentage of HRpeak than boys.

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Shira Fanti-Oren, Daphna Birenbaum-Carmeli, Alon Eliakim, Michal Pantanowitz, Dana Schujovitzky, and Dan Nemet

Purpose: To assess the effect of 1 week of consuming a placebo “energy drink” compared with a week of drinking regular water on daily physical activity in obese children participating in a weight reduction multidisciplinary program. Methods: Seventeen prepubertal (age = 128.7 [26.6] m) overweight and obese children (7 females and 10 males) participated in the study. Participants received 7 bottles of mineral water per week for 2 weeks. Different types of information were randomly provided regarding the drink consumed in each week: standard (water) versus deliberate positive information (presumed energy drink and placebo). Daily step count was measured using pedometers and compared using paired t test. Results: After consuming the placebo drink, children demonstrated a significantly higher average daily step number (10,452 [4107]) compared with the days they drank water (8168 [2928], P < .005). This difference was attributed mainly to male participants. Conclusion: The use of placebo in the form of deliberate positive information was associated with a significant increase in real-life physical activity in overweight and obese children, especially in boys. Positive information may be used to encourage children with obesity to enhance daily physical activity and energy expenditure.

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Jerica M. Berge, Octavia Cheatom, Angela R. Fertig, Allan Tate, Amanda Trofholz, Junia N. Brito, and Nathan Shippee

Given the high prevalence of overweight/obesity and the low prevalence of engaging in physical activity in children, it is important to identify barriers that impede child physical activity. One potential barrier is parental stress. The current study examined the association between parental stress levels and girls’ and boys’ moderate to vigorous physical activity. Children aged 5–7 years and their families (n = 150) from 6 racial/ethnic groups (n = 25 each Black, Hispanic, Hmong, Native American, Somali, and White families) were recruited for the Family Matters mixed-methods study in 2015 through primary care clinics in Minneapolis and St Paul, MN. Two in-home visits were carried out with families 10 days apart for data collection, with an 8-day observational period in between when children wore accelerometers. Higher parental stress levels were associated with fewer minutes of moderate to vigorous physical activity in girls (P < .05) compared with boys. On average, girls with a parent reporting a stress rating of 10 engaged in 24 minutes less of physical activity per day than girls with a parent with a stress rating of 1. The results suggest that parental stress may reduce girls’ engagement in physical activity. The implications of these results include targeting parental stress and coping skills in future physical activity interventions. In addition, when addressing child physical activity in health care visits with parents and daughters, providers may want to focus their anticipatory guidance on parental stress and coping skills in addition to providing resources to help parents manage stress.