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Amin Daneshfar, Carl J. Petersen, Majid S. Koozehchian and Daniel E. Gahreman

This study aimed to identify the acute effects of caffeinated chewing gum (CAF) on bicycle motocross (BMX) time-trial (TT) performance. In a randomized, placebo-controlled, double-blind cross-over design, 14 male BMX riders (age = 20.0 ± 3.3 years; height = 1.78 ± 0.04 m; body mass = 72 ± 4 kg), consumed either (300 mg; 4.2 ± 0.2 mg/kg) caffeinated (300 mg caffeine, 6 g sugars) or a placebo (0 mg caffeine, 0 g sugars) gum, and undertook three BMX TTs. Repeated-measure analysis revealed that CAF has a large ergogenic effect on TT time, F(1, 14) = 33.570, p = .001, ηp2=.71; −1.5% ± 0.4 compared with the placebo. Peak power and maximal power to weight ratio also increased significantly compared with the placebo condition, F(1, 14) = 54.666, p = .001, ηp2=.79; +3.5% ± 0.6, and F(1, 14) = 57.399, p = .001, ηp2=.80; +3% ± 0.3, respectively. Rating of perceived exertion was significantly lower F(1, 14) = 25.020, p = .001, ηp2=.64 in CAF (6.6 ± 1.3) compared with the placebo (7.2 ± 1.7). Administering a moderate dose (300 mg) of CAF could improve TT time by enhancing power and reducing the perception of exertion. BMX coaches and riders may consider consuming CAF before a BMX race to improve performance and reduce rating of perceived exertion.

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Ade B. Pratama and Tossaporn Yimlamai

Purpose: To compare the effectiveness of 3 recovery protocols on muscle oxygenation, blood lactate, and subsequent performance during a 200-m repeated swim session. Methods: Twelve collegte swimmers completed 3 sessions of 2 consecutive 200-m front-crawl trials separated by 1 of 3 recovery protocols: a 15-minute active recovery (AR), a 15-minute passive recovery (PR), and a combination of 5-minute AR and 10-minute PR (CR) in a counterbalanced design. Tissue saturation index at biceps femoris, blood lactate concentration, arterial oxygen saturation, and heart rate were measured at rest, immediately after the trial, and at 5, 10, and 15 minutes of recovery. Two-way analysis of variance (recovery × time) with repeated measures was used to determine measurement variables. A level of significance was set at P < .05. Results: No significant changes in swimming time were observed between trials (AR: 156.79 [4.09] vs 157.79 [4.23] s, CR: 156.50 [4.89] vs 155.55 [4.86] s, PR: 156.54 [4.70] vs 156.30 [4.52] s) across recovery conditions. Interestingly, tissue saturation index rapidly declined immediately after a 200-m swim and then gradually returned to baseline, with a greater value observed during CR compared with AR and PR after 15-minute recovery (P = .04). These changes were concomitant with significant reductions in blood lactate and heart rate during the recovery period (P = .00). Conclusion: The CR in the present study was more effective in enhancing muscle reoxygenation after a 200-m swim compared with AR and PR, albeit its beneficial effect on subsequent performance warrants further investigation.

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Katelyn M. Nelson, Elizabeth H.K. Daidone, Katherine M. Breedlove, Debbie A. Bradney and Thomas G. Bowman

The study objective was to determine the magnitude and frequency of head impacts in NCAA Division III soccer athletes based on player position and type of play (offense, defense, transition). Across player position, male and female soccer defenders sustained the most head impacts (males IR = 18.89, 95% CI = 16.89–20.89; females IR = 8.45, 95% CI = 7.25–9.64; IRR = 2.23, 95% CI = 1.87–2.67). The study revealed a nonstatistically significant interaction between sex, player position, and type of play for both linear (p = .42) and rotational accelerations (p = .16). Defenders sustained the majority of the head impacts in the study sample, suggesting preventative initiatives should be focused on back row players.

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Isao Saito, Koutatsu Maruyama, Tadahiro Kato, Yasunori Takata, Kiyohide Tomooka, Ryoichi Kawamura, Yuichi Uesugi, Yoshihiko Naito, Haruhiko Osawa and Takeshi Tanigawa

Background: Autonomic activity is possibly influenced by physical activity (PA). However, it remains unclear whether this association is modified by insulin resistance. Methods: This population-based study between 2009 and 2012 included 2016 men and women aged 30–79 years. The PA was assessed using a validated questionnaire based on sleep, occupation, transportation, household characteristics, and leisure-time PA. Heart rate (HR) and heart rate variability (HRV) in the sitting position were determined from 5-minute recordings of pulse waves detected by a fingertip sensor. The HRV was calculated as frequency (standard deviation of normal-to-normal [NN] intervals [SDNN]), root mean square of successive differences (RMSSD), and percentage differences between normal NN intervals >50 milliseconds [pNN50]) and time domains. Insulin resistance was evaluated using the homeostasis model assessment index (HOMA-IR). Results: HR, RMSSD, and pNN50 were related to the total and moderate/vigorous PA tertiles in models that included HOMA-IR. The partial regression coefficient of total PA per 1-SD increase was .05 (P = .019) for log-transformed RMSSD and 1.86 (P = .001) for pNN50. No interactive associations were observed between PA and HOMA-IR. Conclusions: Low total PA was associated with increased HR and low levels of RMSSD and pNN50, reflecting parasympathetic modulation that was not modified by insulin resistance.

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Milos R. Petrovic, Amador García-Ramos, Danica N. Janicijevic, Alejandro Pérez-Castilla, Olivera M. Knezevic and Dragan M. Mirkov

Purpose: To test whether the force–velocity (F–V) relationship obtained during a specific single-stroke kayak test (SSKT) and during nonspecific traditional resistance-training exercises (bench press and prone bench pull) could discriminate between 200-m specialists and longer-distance (500- and 1000-m) specialists in canoe sprint. Methods: A total of 21 experienced male kayakers (seven 200-m specialists and 14 longer-distance specialists) participated in this study. After a familiarization session, kayakers came to the laboratory on 2 occasions separated by 48 to 96 hours. In a randomized order, kayakers performed the SSKT in one session and the bench press and bench pull tests in another session. Force and velocity outputs were recorded against 5 loads in each exercise to determine the F–V relationship and related parameters (maximum force, maximum velocity, F–V slope, and maximum power). Results: The individual F–V relationships were highly linear for the SSKT (r = .990 [.908, .998]), bench press (r = .993 [.974, .999]), and prone bench pull (r = .998 [.992, 1.000]). The F–V relationship parameters (maximum force, maximum velocity, and maximum power) were significantly higher for 200-m specialists compared with longer-distance specialists (all Ps ≤ .047) with large effect sizes (≥0.94) revealing important practical differences. However, no significant differences were observed between 200-m specialists and longer-distance specialists in the F–V slope (P ≥ .477). Conclusions: The F–V relationship assessed during both specific (SSKT) and nonspecific upper-body tasks (bench press and bench pull) may distinguish between kayakers specialized in different distances.

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Werner de Andrade Müller, Grégore Iven Mielke, Inácio Crochemore M. da Silva, Mariangela F. Silveira and Marlos Rodrigues Domingues

Background: Physical activity (PA) during pregnancy is associated with several benefits in maternal and child outcomes, and its relationship with preterm birth is still conflicting. This study aims to examine the associations between PA during pregnancy and occurrence of preterm birth. Methods: PA was assessed by questionnaire (for each trimester) and accelerometry (second trimester) in women enrolled in a birth cohort study that started during pregnancy and included births that occurred between January 1 and December 31, 2015. Gestational age was based on the last menstrual period and ultrasonography. All deliveries before 37 weeks of gestation were considered preterm births. A Poisson regression model was used to measure associations controlling for potential confounders. Results: PA information was available for 4163 women and 13.8% of births were preterm. A total of 15.8% of women were engaged in PA during pregnancy. Multivariate analysis showed that only PA performed in the third trimester of pregnancy (prevalence ratio = 0.58; 95% confidence interval, 0.36–0.96) was associated with the outcome. Conclusions: PA performed in the third trimester of pregnancy was associated with a protection to preterm birth. Pregnant women should be counseled to engage in PA to lower the risk of premature delivery.

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Rachel Allison

Although women athletes in professional sport are uniquely positioned to expose the limits of gender essentialist ideology and challenge its relationship with inequality, little empirical research has considered how professional women athletes understand and negotiate gender ideologies. Drawing on 19 in-depth interviews and one e-mail exchange with U.S. women’s professional soccer players, this article finds that sportswomen strategically endorse constructions of gender difference while simultaneously universalizing White, middle-class women’s experiences. “Privileging difference” is a narrative whereby players recognize belief in women’s physical inferiority to men and argue for women’s moral superiority to men as a source of value and reward for women’s sport. Sportswomen’s moral authority is defined from a position of racialized class privilege, as players construct an idealized woman player who sacrifices material reward for emotional satisfaction and who emphasizes future change over present conditions.

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James A. Betts

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Eishin Teraoka, Heidi Jancer Ferreira, David Kirk and Farid Bardid

Purpose: The purpose of this study was to carry out a systematic review of intervention programs that have addressed affective learning outcomes within physical education and to explore pedagogical practices in alignment with teaching, lesson content, and learning outcomes. Method: The literature search was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Included were 26 peer-reviewed pedagogical studies of physical education programs that addressed affective outcomes and reported fidelity of implementation. Results and Discussion: Affective outcomes were grouped into four themes: motivation, emotional responses, self-concept, and resilience. The findings showed that offering choice, encouraging peer feedback, asking deductive questions, focusing on personal improvement, and differentiating are effective teaching strategies that were widely used to support affective learning in children and adolescents. This review highlights the importance of fidelity of implementation to understand how intervention programs are delivered.

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Erin L. McCleave, Katie M. Slattery, Rob Duffield, Stephen Crowcroft, Chris R. Abbiss, Lee K. Wallace and Aaron J. Coutts

Purpose: To examine whether concurrent heat and intermittent hypoxic training can improve endurance performance and physiological responses relative to independent heat or temperate interval training. Methods: Well-trained male cyclists (N = 29) completed 3 weeks of moderate- to high-intensity interval training (4 × 60 min·wk−1) in 1 of 3 conditions: (1) heat (HOT: 32°C, 50% relative humidity, 20.8% fraction of inspired oxygen, (2) heat + hypoxia (H+H: 32°C, 50% relative humidity, 16.2% fraction of inspired oxygen), or (3) temperate environment (CONT: 22°C, 50% relative humidity, 20.8% fraction of inspired oxygen). Performance 20-km time trials (TTs) were conducted in both temperate (TTtemperate) and assigned condition (TTenvironment) before (base), immediately after (mid), and after a 3-week taper (end). Measures of hemoglobin mass, plasma volume, and blood volume were also assessed. Results: There was improved 20-km TT performance to a similar extent across all groups in both TTtemperate (mean ±90% confidence interval HOT, −2.8% ±1.8%; H+H, −2.0% ±1.5%; CONT, −2.0% ±1.8%) and TTenvironment (HOT, −3.3% ±1.7%; H+H, −3.1% ±1.6%; CONT, −3.2% ±1.1%). Plasma volume (HOT, 3.8% ±4.7%; H+H, 3.3% ±4.7%) and blood volume (HOT, 3.0% ±4.1%; H+H, 4.6% ±3.9%) were both increased at mid in HOT and H+H over CONT. Increased hemoglobin mass was observed in H+H only (3.0% ±1.8%). Conclusion: Three weeks of interval training in heat, concurrent heat and hypoxia, or temperate environments improve 20-km TT performance to the same extent. Despite indications of physiological adaptations, the addition of independent heat or concurrent heat and hypoxia provided no greater performance benefits in a temperate environment than temperate training alone.