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Open access

Alannah K.A. McKay, Peter Peeling, David B. Pyne, Nicolin Tee, Marijke Welveart, Ida A. Heikura, Avish P. Sharma, Jamie Whitfield, Megan L. Ross, Rachel P.L. van Swelm, Coby M. Laarakkers, and Louise M. Burke

This study implemented a 2-week high carbohydrate (CHO) diet intended to maximize CHO oxidation rates and examined the iron-regulatory response to a 26-km race walking effort. Twenty international-level, male race walkers were assigned to either a novel high CHO diet (MAX = 10 g/kg body mass CHO daily) inclusive of gut-training strategies, or a moderate CHO control diet (CON = 6 g/kg body mass CHO daily) for a 2-week training period. The athletes completed a 26-km race walking test protocol before and after the dietary intervention. Venous blood samples were collected pre-, post-, and 3 hr postexercise and measured for serum ferritin, interleukin-6, and hepcidin-25 concentrations. Similar decreases in serum ferritin (17–23%) occurred postintervention in MAX and CON. At the baseline, CON had a greater postexercise increase in interleukin-6 levels after 26 km of walking (20.1-fold, 95% CI [9.2, 35.7]) compared with MAX (10.2-fold, 95% CI [3.7, 18.7]). A similar finding was evident for hepcidin levels 3 hr postexercise (CON = 10.8-fold, 95% CI [4.8, 21.2]; MAX = 8.8-fold, 95% CI [3.9, 16.4]). Postintervention, there were no substantial differences in the interleukin-6 response (CON = 13.6-fold, 95% CI [9.2, 20.5]; MAX = 11.2-fold, 95% CI [6.5, 21.3]) or hepcidin levels (CON = 7.1-fold, 95% CI [2.1, 15.4]; MAX = 6.3-fold, 95% CI [1.8, 14.6]) between the dietary groups. Higher resting serum ferritin (p = .004) and hotter trial ambient temperatures (p = .014) were associated with greater hepcidin levels 3 hr postexercise. Very high CHO diets employed by endurance athletes to increase CHO oxidation have little impact on iron regulation in elite athletes. It appears that variations in serum ferritin concentration and ambient temperature, rather than dietary CHO, are associated with increased hepcidin concentrations 3 hr postexercise.

Open access
Open access

Kihan Kim, Hojun Sung, Yeayoung Noh, and Kimoon Lee

This study investigated the determinants of television viewership and its relation to broadcasters’ choices of matches for live telecasts. Also, factors driving the broadcasters’ choices were examined. A panel data set from the 2018 Korea Baseball Organization league pennant race was analyzed. Broadcasters’ choice order of matches and the actual television ratings of each match were regressed on a series of antecedent factors related to the game characteristics and audience preferences. It was found that the broadcasters’ choice order of matches positively affected the television ratings, suggesting that the broadcasters’ decisions were well reflected in the actual viewership. It also appeared that broadcasters’ choices were based on popularity and team performance/quality, whereas viewers showed preference for current games’ on-field performance. There was no evidence of audience preference for games with higher outcome uncertainty, whereas the broadcasters tended to choose games with more certain, rather than uncertain, outcomes. Theoretical and practical implications of the findings were discussed.

Open access

Mandeep Kaur, Daniel Cury Ribeiro, Kate E. Webster, and Gisela Sole

Context: Altered knee joint mechanics may be related to quadriceps muscle strength, time since surgery, and sex following anterior cruciate ligament reconstruction (ACLR). The aim of this study was to investigate the association between knee moments, with participant-related factors during stair navigation post-ACLR. Design: Cross-sectional study. Methods: A total of 30 participants (14 women) with ACLR, on average 7.0 (SD 4.4) years postsurgery were tested during stair ascent and descent in a gait laboratory. Motion capture was conducted using a floor-embedded force plate and 11 infrared cameras. Quadriceps concentric and eccentric muscle strength was measured with an isokinetic dynamometer at 60°/s, and peak torques recorded. Multiple regression analyses were performed between external knee flexion and adduction moments, respectively, and quadriceps peak torque, sex, and time since ACLR. Results: Higher concentric quadriceps strength and female sex accounted for 55.7% of the total variance for peak knee flexion moment during stair ascent (P < .001). None of the independent variables accounted for variance in knee adduction moment (P = .698). No significant associations were found for knee flexion and adduction moments during for stair descent. Conclusion: Higher quadriceps concentric strength and sex explains major variance in knee flexion moments during stair ascent. The strong association between muscle strength and external knee flexion moments during stair ascent indicate rehabilitation tailored for quadriceps may optimize knee mechanics, particularly for women.

Open access
Open access

Rodrigo Reis, Ruth F. Hunter, Leandro Garcia, and Deborah Salvo

We are experiencing a planetary tipping point with global warming, environmental degradation, and losses in biodiversity. The burdens of these changes fall disproportionately on poor and marginalized populations. Physical activity promotion strategies need to be aligned with climate action commitments, incorporating the Intergovernmental Panel on Climate Change scenarios in physical activity action plans. The promotion strategies must consider equity a core value and promote physical activity to the most vulnerable populations so that they are protected from the ill-health impacts of a changing climate.

Open access
Open access

Fei Tian, Yaqi Zhao, Jixin Li, Wenjin Wang, Danni Wu, Qiang Li, Liyun Guo, and Shaobai Wang

Context: Many methods used to evaluate knee proprioception have shortcomings that limit their use in clinical settings. Based on an inexpensive 3D camera, a new portable device was recently used to evaluate the joint position sense (JPS) of the knee joint. However, the test–retest reliability of the new method remains unclear. This study aimed to evaluate the test–retest reliability of the new device and a long-arm goniometer for assessing knee JPS, and to compare the variability of the 2 methods. Design: Prospective observational study of the test–retest reliability of knee JPS measurements. Methods: Twenty-one healthy adults were tested in 2 sessions with a 1-week interval. Three target knee flexion angles (30°, 45°, and 60°) were reproduced in each session. Target and reproduced angles were measured with both methods. Intraclass correlation coefficients, standard error of the measurement, and Bland–Altman plots were used to quantify test–retest reliability. Paired t tests were used to compare knee JPS (absolute error of the target-reproduced angle) between the methods. Results: The new device (good to excellent intraclass correlation coefficients .74–.80; standard error of the measurement 0.52°–0.61°) demonstrated better test–retest reliability than the goniometer (poor to fair intraclass correlation coefficients .23–.43; standard error of the measurement 0.89°–2.07°) and better test–retest agreement (respective mean differences for the 30°, 45°, and 60° knee angles: 0.11°, 0.13°, and 0.41° for the new system; 0.84°, 1.52°, and 1.18° for the goniometer). The measurements (absolute errors of the target-reproduced angles) with the goniometer were significantly greater than those with the new device (P < .05); the SDs of repeated measurements with the goniometer (1.50°–2.41°) were greater than with the new device (1.08°–1.38°). Conclusions: Given that the new device has good reliability and sufficient precision, it is the better alternative for evaluating knee JPS. Goniometers should be used with caution to assess knee JPS.

Open access

Seyyed Mohammadreza Mousavi and Takehiro Iwatsuki

Expectancies for success and autonomy support have been shown to facilitate motor learning and enhance motor performance. The purpose of the study was to examine whether we replicated (a) enhanced expectancies and autonomy support intervention enhanced motor skill learning in children, and (b) identified the underlying psychological mechanism. Sixty children kicked soccer balls with their dominant leg to a squared area target. Participants were randomly assigned to one of the four groups: enhanced expectancies and autonomy support (EE/AS), enhanced expectancies (EE), autonomy support (AS), or control (CON) groups. Participants learning the skill were or were not provided enhanced expectation instructions by making the task success easier and provided an opportunity to choose one of the three colored balls during their practice. Two days later, they performed retention and transfer tests. Results indicated that the EE/AS group had the highest scores, with main effects of autonomy support being significant and enhanced expectancies being marginally significant for the retention test and significant for the transfer test. The EE/AS group had the highest self-efficacy and perceived choice scores. Therefore, having high expectancies for success and being autonomous were important ingredients for facilitating motor skill learning in children.