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Purpose: The current study aimed to determine the effect of a synthetic-grass sport surface on core body temperature, skin temperature, heart rate, thermal sensation, thermal comfort, and rating of perceived exertion (RPE) during intermittent exercise in hot conditions. Methods: Using a randomized crossover design, 13 trained/developmental team-sport athletes completed two 50-minute standardized intermittent running protocols on a synthetic and a natural-grass surface, on separate days (control-condition air temperature 32.6 °C [1.3 °C], relative humidity 43.2% [5.3%]). Results: Final skin temperature was significantly higher on synthetic compared with natural grass at the calf (40.1 °C [2.5 °C] vs 33.4 °C [0.6 °C]; P <.001), shoulder (36.6 °C [1.7 °C] vs 33.7 °C [0.7 °C]; P <.001), and chest (33.2 °C [1.1 °C] vs 31.8 °C [1.2 °C]; P =.02). Thermal sensation (median: 2.3; interquartile range [0.5] vs 2.2 [0.5], P =.03) and sweat rate (1.5 [0.4] L·h−1 vs 1.2 [0.3] L·h−1; P =.02) were also significantly higher on synthetic grass. While final core body temperature was significantly higher on the natural than synthetic grass (38.4 °C [0.3 °C] vs 38.2 °C [0.4 °C]), there were no significant differences in delta core temperature, as well as heart rate, thermal comfort, or RPE. Conclusions: Higher skin temperatures, thermal sensation, and sweat rates suggest that exercising on synthetic grass in hot conditions may increase some markers of heat strain during exercise. However, delta core body temperature, heart rate, thermal comfort, and RPE remained unaffected. [ABSTRACT FROM AUTHOR]

Purpose: To assess elite racewalkers' preparation strategies, knowledge, and general practices for competition in the heat and their health status during the World Athletics Race Walking Teams Championships (WRW) Muscat 2022. Methods: Sixty-six elite racewalkers (male: n = 42; mean age = 25.8 y) completed an online survey prior to WRW Muscat 2022. Athletes were grouped by sex (males vs females) and climate (self-reported) they live/trained in (hot vs temperate/cold), with differences/relationships between groups assessed. Relationships between ranking (medalist/top 10 vs nonmedalist/nontop 10) and precompetition use of heat acclimation/acclimatization (HA) were assessed. Results: All surveyed medalists (n = 4) implemented, and top 10 finishers were more likely to report using (P =.049; OR = 0.25; 95% CI, 0.06%–1%), HA before the championships. Forty-three percent of athletes did not complete specific HA training. Females (8% [males 31%]) were less likely to have measured core temperature (P =.049; OR = 0.2; 95% CI, 0.041–0.99) and more likely to not know expected conditions in Muscat (42% vs 14%; P =.016; OR = 4.3; 95% CI, 1%–14%) or what wet bulb globe temperature is (83% vs 55%; P =.024; OR = 4.1; 95% CI, 1%–14%). Conclusions: Athletes who implemented HA before the championships tended to place better than those who did not. Forty-three percent of athletes did not prepare for the expected hot conditions at the WRW Muscat 2022, primarily attributed to challenges in accessing and/or cost of equipment/facilities for HA strategies. Further efforts to bridge the gap between research and practice in this elite sport are needed, particularly in female athletes. [ABSTRACT FROM AUTHOR]

Purpose: To determine the effect of wearing a phase-change cooling vest in elite female rugby sevens athletes during (1) a simulated match-day warm-up in hot conditions prior to a training session and (2) a prematch warm-up during a tournament in cool conditions. Methods: This study consisted of 2 randomized independent group designs (separated by 16 d) where athletes completed the same 23- to 25-minute match-day warm-up (1) in hot conditions (range = 28.0°C to 35.1°C wet bulb globe temperature [WBGT]) prior to training and (2) in cool conditions (range = 18.8°C to 20.1°C WBGT) prior to a World Rugby Women's Sevens Series match. In both conditions, athletes were randomly assigned to wearing either (1) the standardized training/playing ensemble (synthetic rugby shorts and training tee/jersey) or (2) the standardized training/playing ensemble plus a commercial phase-change athletic cooling vest. Group-wise differences in core temperature rise from baseline, global positioning system–measured external locomotive output, and perceptual thermal load were compared. Results: Core temperature rise during a match warm-up was lower in the hot condition only (−0.65°C [95% confidence interval = −1.22°C to −0.08°C], η p 2 =.23 [95% confidence interval =.00 to.51], P =.028). No differences in various external-load variables were observed. Conclusions: Phase-change cooling vests can be worn by athletes prior to, and during, a prematch warm-up in hot conditions to limit excess core temperature rise without adverse effects on thermal perceptions or external locomotion output. [ABSTRACT FROM AUTHOR]

Purpose: To determine whether elite female rugby sevens players are exposed to core temperatures (Tc) during training in the heat that replicate the temperate match demands previously reported and to investigate whether additional clothing worn during a hot training session meaningfully increases the heat load experienced. Methods: A randomized parallel-group study design was employed, with all players completing the same approximately 70-minute training session (27.5°C–34.8°C wet bulb globe temperature) and wearing a standardized training ensemble (synthetic rugby shorts and training tee [control (CON); n = 8]) or additional clothing (standardized training ensemble plus compression garments and full tracksuit [additional clothing (AC); n = 6]). Groupwise differences in Tc, sweat rate, GPS-measured external locomotive output, rating of perceived exertion, and perceptual thermal load were compared. Results: Mean (P =.006, η p 2 =.88) and peak (P <.001, η p 2 =.97) Tc were higher in AC compared with CON during the training session. There were no differences in external load (F4,9 = 0.155, P =.956, Wilks Λ = 0.935, η p 2 =.06) or sweat rate (P =.054, Cohen d = 1.09). A higher rating of perceived exertion (P =.016, Cohen d = 1.49) was observed in AC compared with CON. No exertional-heat-illness symptomology was reported in either group. Conclusions: Player Tc is similar between training performed in hot environments and match play in temperate conditions when involved for >6 minutes. Additional clothing is a viable and effective method to increase heat strain in female rugby sevens players without compromising training specificity or external locomotive capacity. [ABSTRACT FROM AUTHOR]

When athletes are burning out, performance decreases whereas exhaustion and devaluation increases. Athletes with perfectionistic tendencies may be at greater risk for burnout than those with lower levels. But are there any differences between athletes participating in objectively assessed sports (utilizing unbiased measures, such as time, e.g. swimming) and athletes participating in subjectively assessed sports (relying on coach feedback, competition judges, or internal perceptions to gauge performance, e.g. competitive dancing)? A total of 108 athletes (including 53 athletes in objectively assessed and 55 athletes in subjectively assessed sports) completed the Sport Multidimensional Perfectionism Scale-2 and the Athlete Burnout Questionnaire. Significant relationships were detected between perfectionism and burnout; negative dimensions of perfectionism were more strongly correlated with burnout. However, no significant differences were observed between the sports groupings, either on perfectionism or burnout. This study suggests that perfectionistic concerns are positively associated with athlete burnout, regardless of the athlete's sport being objectively or subjectively assessed. [ABSTRACT FROM AUTHOR]

Purpose: Hot-water immersion (HWI) after training in temperate conditions has been shown to induce thermophysiological adaptations and improve endurance performance in the heat; however, the potential additive effects of HWI and training in hot outdoor conditions remain unknown. Therefore, this study aimed to determine the effect of repeated postexercise HWI in athletes training in a hot environment. Methods: A total of 13 (9 female) elite/preelite racewalkers completed a 15-day training program in outdoor heat (mean afternoon high temperature = 34.6°C). Athletes were divided into 2 matched groups that completed either HWI (40°C for 30–40 min) or seated rest in 21°C (CON), following 8 training sessions. Pre–post testing included a 30-minute fixed-intensity walk in heat, laboratory incremental walk to exhaustion, and 10,000-m outdoor time trial. Results: Training frequency and volume were similar between groups (P =.54). Core temperature was significantly higher during immersion in HWI (38.5 [0.3]) than CON (37.8°C [0.2°C]; P <.001). There were no differences between groups in resting or exercise rectal temperature or heart rate, skin temperature, sweat rate, or the speed at lactate threshold 2, maximal O2 uptake, or 10,000-m performance (P >.05). There were significant (P <.05) pre–post differences for both groups in submaximal exercising heart rate (∼11 beats·min−1), sweat rate (0.34–0.55 L·h−1) and thermal comfort (1.2–1.5 arbitrary units), and 10,000-m racewalking performance time (∼3 min). Conclusions: Both groups demonstrated significant improvement in markers of heat adaptation and performance; however, the addition of HWI did not provide further enhancements. Improvements in adaptation appeared to be maximized by the training program in hot conditions. [ABSTRACT FROM AUTHOR]

Menthol is effective at stimulating thermosensitive neurons that evoke pleasant cooling sensations. Internal application of menthol can be ergogenic for athletes, and hence, addition of menthol to sports nutrition products may be beneficial for athletes. The aim of this study was to develop a menthol energy gel for consumption during exercise and to determine acceptability and preferences for gels with different menthol concentrations. With a randomized, crossover, and double-blind placebo-controlled design, 40 endurance athletes (20 females) ingested an energy gel with a menthol additive at a high (0.5%; HIGH) or low concentration (0.1%; LOW), or a mint-flavored placebo (CON), on separate occasions during outdoor endurance training sessions. The athletes rated the gels for cooling sensation, mint flavor intensity, sweetness, and overall experience and provided feedback. Results are reported as median (interquartile range). Both menthol gels successfully delivered a cooling sensation, with a significantly greater response for HIGH (5.0 [4.0–5.0]) compared with LOW (3.5 [3.0–4.0]; p =.022) and CON (1.0 [1.0–2.0]; p <.0005), and LOW compared with CON (p <.0005). Ratings of mint flavor intensity followed the same trend as cooling sensation, while ratings of overall experience were significantly worse for HIGH (2.0 [1.0–3.0]) compared with LOW (4.0 [2.0–4.0]; p =.001) and CON (4.0 [3.0–4.0]; p <.0005). An energy gel with the addition of menthol at 0.1–0.5% provides a cooling sensation for athletes with a dose–response when ingested during exercise. The 0.1% concentration is recommended to maximize the overall experience of the gel. [ABSTRACT FROM AUTHOR]

Purpose: To characterize player core temperature (Tc) across a World Rugby Women's Sevens Series tournament day (WRWSS) and determine the efficacy of commonly employed cold-water-immersion (CWI) protocols. Methods: Tc was measured in 12 elite female rugby sevens athletes across 3 games (G1–3) from day 1 of the Sydney WRWSS tournament. Symptoms of exertional heat illness, perceptual scales, CWI details, playing minutes, external-load data (measured by global positioning systems), and wet-bulb globe temperature (range 18.5°C–20.1°C) were also collected. Linear mixed models and magnitude-based inferences were used to assess differences in Tc between periods (G1–3 and warm-ups [WU]). Results: Average Tc was "very likely" lower (effect size; ±90% confidence limit −0.33; ±0.18) in G1 than in G2. Peak Tc was "very likely" (0.71; ±0.28) associated with increased playing time. CWI did not remove the accumulated Tc due to WU and match-play activity (∼1°C–2°C rise in Tc still present compared with Tc at WU onset for players ≥6-min match play). Conclusions: Elite WRWSS athletes experienced high Tc during WU (Tc peak 37.9–39.0°C) and matches (Tc peak 37.9–39.8°C), a magnitude known to reduce intermittent high-intensity physical performance (≥39°C). The CWI protocol resulted in players (≥6-min match play) with ∼1°C to 2°C raised Tc compared with Tc at WU onset. [ABSTRACT FROM AUTHOR]

Due to the lack of research in real-world sports competitions, the International Olympic Committee, in 2012, called for data characterising athletes' sport and event-specific thermal profiles. Studies clearly demonstrate that elite athletes often attain a core body temperature (Tc) ≥ 40°C without heat-related medical issues during competition. However, practitioners, researchers and ethical review boards continue to cite a Tc ≥ 40°C (and lower) as a threshold where athlete health is impacted (an assumption from laboratory studies). Therefore, this narrative review aims to: (i) summarise and review published data on Tc responses during competitive sport and identify key considerations for practitioners; (ii) establish the incidence of athletes experiencing a Tc ≥ 40°C in competitive sport alongside the incidence of heat illness/heat stroke (EHI/EHS) symptoms; and (iii) discuss the evolution of Tc measurement during competition. The Tc response is primarily based on the physical demands of the sport, environmental conditions, competitive level, and athlete disability. In the reviewed research, 11.9% of athletes presented a Tc ≥ 40°C, with only 2.8% of these experiencing EHI/EHS symptoms, whilst a high Tc ≥ 40°C (n = 172; Tc range 40--41.5°C) occurred across a range of sports and environmental conditions (including some temperate environments). Endurance athletes experienced a Tc ≥ 40°C more than intermittent athletes, but EHI/EHS was similar. This review demonstrates that a Tc ≥ 40°C is not a consistently meaningful risk factor of EHI/EHS symptomology in this sample; therefore, Tc monitoring alongside secondary measures (i.e. general cognitive disturbance and gait disruption) should be incorporated to reduce heat-related injuries during competition. [ABSTRACT FROM AUTHOR]

Flow is an optimal psychological state associated with exceptional performances and positive subjective experiences in sport and exercise. Considering these reported benefits, there have been many attempts to promote flow experiences through interventions. However, there is little evidence to demonstrate the effectiveness of flow interventions in sport and exercise. This study aimed to systematically review, synthesise, and evaluate the efficacy of flow interventions in sport and exercise to date. Twenty-nine empirical studies, published before August 2020 were identified, primarily comprising single-case designs (41.38%) and quasi-experimental designs (34.48%). Strategies most commonly reported in flow interventions to date included: mindfulness (30.03%); hypnosis (17.24%); and imagery (13.79%). While there is evidence that interventions increased certain dimensions of flow, no studies to date have reported conclusive evidence that flow was induced through an intervention. None of the included studies were developed through an intervention development framework, and the strategies employed were generally only partially related to a conceptual framework of flow. Collectively, these findings suggest interventions reported to date have largely been unsuccessful at producing flow experiences. The conceptual, developmental, and methodological issues impacting the quality of flow interventions are discussed, and recommendations are made to improve the efficacy of flow interventions in future. [ABSTRACT FROM AUTHOR]

A common practice among endurance athletes is to purposefully train in hot environments during a "heat stress camp." However, combined exercise-heat stress poses threats to athlete well-being, and therefore, heat stress training has the potential to induce maladaptation. This case study describes the monitoring strategies used in a successful 3-week heat stress camp undertaken by 2 elite Ironman triathletes, namely resting heart rate variability, self-report well-being, and careful prescription of training based on previously collected physiological data. Despite the added heat stress, training volume very likely increased in both athletes, and training load very likely increased in one of the athletes, while resting heart rate variability and self-report well-being were maintained. There was also some evidence of favorable metabolic changes during routine laboratory testing following the camp. The authors therefore recommend that practitioners working with endurance athletes embarking on a heat stress training camp consider using the simple strategies employed in the present case study to reduce the risk of maladaptation and nonfunctional overreaching. [ABSTRACT FROM AUTHOR]

Purpose: To determine how a cooling vest worn during a warm-up could influence selected performance (countermovement jump [CMJ]), physical (global positioning system [GPS] metrics), and psychophysiological (body temperature and perceptual) variables. Methods: In a randomized, crossover design, 12 elite male World Rugby Sevens Series athletes completed an outdoor (wet bulb globe temperature 23-27°C) match-specific externally valid 30-min warm-up wearing a phase-change cooling vest (VEST) and without (CONTROL), on separate occasions 7 d apart. CMJ was assessed before and after the warm-up, with GPS indices and heart rate monitored during the warm-ups, while core temperature (Tc; ingestible telemetric pill; n = 6) was recorded throughout the experimental period. Measures of thermal sensation (TS) and thermal comfort (TC) was obtained pre-warm-up and post-warm-up, with rating of perceived exertion (RPE) taken post-warm-ups. Results: Athletes in VEST had a lower ΔTc (mean [SD]: VEST=1.3°C [0.1°C]; CONTROL = 2.0°C [0.2°C]) from pre-warm-up to post-warm-up (effect size; ±90% confidence limit: -1.54; ±0.62) and Tc peak (mean [SD]: VEST = 37.8°C [0.3°C]; CONTROL = 38.5°C [0.3°C]) at the end of the warm-up (-1.59; ±0.64) compared with CONTROL. Athletes in VEST demonstrated a decrease in ΔTS (-1.59; ±0.72) and ΔTC (-1.63; ±0.73) pre-warm-up to post-warm-up, with a lower RPE post-warm-up (-1.01; ±0.46) than CONTROL. Changes in CMJ and GPS indices were trivial between conditions (effect size < 0.2). Conclusions: Wearing the vest prior to and during a warm-up can elicit favorable alterations in physiological (Tc) and perceptual (TS, TC, and RPE) warm-up responses, without compromising the utilized warm-up characteristics or physical-performance measures. [ABSTRACT FROM AUTHOR]

Flow is an intrinsically rewarding psychological state characterized by effortlessness, absorption, and feelings of automaticity, that is associated with numerous beneficial outcomes for athletes (e.g., performance, motivation, wellbeing). Many studies have attempted to induce flow through interventions, however, with minimal success, perhaps due to a lack of consultation with end-users regarding appropriate strategies. Therefore, this study sought to examine runners' perspectives on potential strategies that should be considered during the development of flow interventions. Fourteen athletes (Mage = 32.71; SD = 7.22) participated in semi-structured interviews. Data were analyzed using reflexive thematic analysis, which generated four categories with themes relating to factors that cause and inhibit the occurrence of flow within each category. Specifically, these runners suggested that flow interventions should: (i) create an exploratory or novel context; (ii) set open-ended goals; (iii) provide feedback that exceeds expectations; and (iv) ensure that attention is process-focused or directed toward pleasant aspects of the run. Moreover, runners suggested that certain strategies may inhibit the experience of flow: (i) evaluative contexts; (ii) setting specific goals; (iii) delivering quantitative feedback; and (iv) focusing on disruptive stimuli and bodily sensations. The findings of this study provide researchers with detailed end-user perspectives of strategies that may inform the development of flow interventions, and in turn, increase the likelihood of their efficacy. Lay summary: The immersive, motivating, and effortless psychological state of "flow" has numerous benefits for athletes and exercisers (e.g., improved performance and wellbeing). This study interviewed runners to understand their perspectives on factors involved in the occurrence of flow, and how they relate to potential intervention strategies. Through the exploration of these factors, the findings indicate that those developing flow interventions should consider lowering the perceived demands and expectations of the activity, open-ended goal setting strategies, the delivery of feedback implying performance is better than expected, and to direct attention toward process-related distractions. Runners indicated that various psychological contexts, goal setting strategies, feedback, and attentional focus can cause or inhibit flow states. Athletes, coaches, and practitioners should consider creating novelty or removing specific performance demands (e.g., running a new route, terrain, or distance that is devoid of clear expectations), setting open-ended goals, avoiding quantitative feedback, and focusing on process-related stimuli when attempting to experience flow during sport and exercise. Consulting with end-users during intervention development increases the likelihood of their efficacy. Hence, this study provides a range of considerations to improve flow intervention development and subsequent efficacy. [ABSTRACT FROM AUTHOR]

An approximate solution is developed for the mutual inductance of two circular coils enclosed by insulating cavities in a conducting medium. This solution is used to investigate the variation of the mutual inductance upon the conductivity of the background (e.g., soil, seawater or human body), as well as upon other parameters such as the vertical of the coils and the displacement of one of the coils in the horizontal plane. Our theoretical results are compared with full wave simulations and a previous solution valid when a conductive slab is inserted between two coupled resonant coils. The proposed approach can have direct impact on the design and optimisation of magnetoinductive waveguides and wireless power transfer for underground/underwater networks and embedded biomedical systems.

An analytical model is developed for the charge and potential distributions of the fundamental mode of three-dimensional (3D) singly split ring resonators (SRRs) with square cross section, which nowadays can be conveniently fabricated by additive manufacturing techniques. This model allows the derivation of approximate formulas for the equivalent capacitance and the analysis of the resonant properties of this type of SRRs at any frequency. The total capacitance is expressed as the sum of the usual gap capacitance and a surface capacitance associated with the charges on the SRR walls, which are determined from the solution for the irrotational part of the electric field of a square split cylinder obtained by conformal mapping. The applicability of the proposed model for a broad range of SRR parameters is demonstrated by comparing the resonance frequency of sample SRR configurations found theoretically with the corresponding values obtained by numerical simulations and experiments. Furthermore, the functions describing the charge and current mode profiles provided in this work can be instrumental in estimating the near-field interaction and the coupling constants of an ensemble of resonant 3D square split rings and thus for tailoring the response of metamaterials and other devices formed by these elements. [ABSTRACT FROM AUTHOR]

Monitoring athletes' training may help prevent negative consequences such as overtraining and burnout. However, acceptance or willingness of athletes to participate is a barrier to an effective training monitoring program. Educational strategies may potentially increase adherence. Therefore, our aims are to i) assess the impact of training monitoring education on adherence to a monitoring program; ii) determine the effect of the education intervention on burnout, stress, and recovery, and; iii) qualitatively investigate athlete perspectives of the education and training monitoring experience. Recreational athletes (18 male/17 female; age = 42.6 ± 12.0) were randomised to either a control (n = 19) or education (n = 16) group and completed daily training monitoring through a smartphone application over 10 weeks. Pre-post assessments using the Athlete Burnout Questionnaire, the Acute Recovery Stress Scale, and a perceived knowledge of training monitoring questionnaire, and semi-structured interviews were performed. Adherence was low, with no differences between the control group ([mean ± SD]; 43.0 ± 38.8%) and the education group (45.8 ± 36.7%). There were also no differences (p >0.05) between the groups on the standardised inventories. There was a significant effect of time (p <0.001) on participant's perceived understanding of training monitoring tools (scored out of 42) at the end of the washout period (Control: 24.4 ± 6.6; Education: 28.5 ± 5.6) and post-study (Control: 32.1 ± 7.5; Education: 35.1 ± 6.0) compared to the pre-study (Control: 21.5 ± 7.3; Education: 21.9 ± 7.7). Interviews revealed participants wanted more education on modifying their training, and feedback on their data. Our findings suggest this specific educational approach was not enough to increase adherence; other aspects of education and individual feedback needs to be further explored. [ABSTRACT FROM AUTHOR]

The radiation characteristics of ultrawideband (UWB) antennas vary with frequency, introducing directionally asymmetric bandwidth reduction and waveform dispersion. In this paper, we develop a simple technique to alleviate the distortion due to nonisotropically dispersive antennas, and use indoor channel measurements to verify its performance. The approach is based on multipath direction estimation and therefore involves antenna arrays. We show that antenna distortion can enhance sensor localization ambiguity and introduce errors in its estimate. Antenna compensation mitigates this effect, significantly improving the location estimation accuracy. We further demonstrate that antenna compensation helps reduce the small-scale fading artifacts that arise due to the antennas, thus reducing the channel spatial variability and delay spread. Our technique can also aid empirical channel characterization by providing antenna-independent propagation data. Index Terms--Antenna, array, direction-of-arrival (DOA) estimation, distortion, sensor localization, ultrawideband (UWB).

Rake reception can improve system performance significantly in wideband multipath channels. Its practical implementation, however, becomes prohibitively expensive in channels with dense multipath, such as the ultrawideband (UWB) channel. This paper investigates the effect of various system and environment parameters on rake performance, with emphasis on the amount of multipath and channel bandwidth. The treatment includes hybrid selection/maximal-ratio combining (H-S/MRC) and unordered, partial combining rake architectures, and is based on indoor channel measurements in the FCC-allocated UWB frequency range (3.1-10.6 GHz). The diversity gain is shown to follow the law of diminishing returns with the rake complexity. It is demonstrated that the rake can extract most of the incident signal power by combining only a subset of the resolved multipath components. The required number of rake fingers increases linearly with the number of resolved paths but sublinearly with the channel bandwidth. The characterization of the interplay of bandwidth, amount of scattering and rake complexity will facilitate efficient implementation of UWB systems. Index Terms--Diversity combining, hybrid selection/maximal-ratio combining (H-S/MRC), indoor propagation, multipath fading, rake receiver, ultrawideband (UWB).