It is the position of Sports Dietitians Australia (SDA) that exercise in hot and/or humid environments, or with significant clothing and/or equipment that prevents body heat loss (i.e., exertional heat stress), provides significant challenges to an athlete’s nutritional status, health, and performance. Exertional heat stress, especially when prolonged, can perturb thermoregulatory, cardiovascular, and gastrointestinal systems. Heat acclimation or acclimatization provides beneficial adaptations and should be undertaken where possible. Athletes should aim to begin exercise euhydrated. Furthermore, preexercise hyperhydration may be desirable in some scenarios and can be achieved through acute sodium or glycerol loading protocols. The assessment of fluid balance during exercise, together with gastrointestinal tolerance to fluid intake, and the appropriateness of thirst responses provide valuable information to inform fluid replacement strategies that should be integrated with event fuel requirements. Such strategies should also consider fluid availability and opportunities to drink, to prevent significant under- or overconsumption during exercise. Postexercise beverage choices can be influenced by the required timeframe for return to euhydration and co-ingestion of meals and snacks. Ingested beverage temperature can influence core temperature, with cold/icy beverages of potential use before and during exertional heat stress, while use of menthol can alter thermal sensation. Practical challenges in supporting athletes in teams and traveling for competition require careful planning. Finally, specific athletic population groups have unique nutritional needs in the context of exertional heat stress (i.e., youth, endurance/ultra-endurance athletes, and para-sport athletes), and specific adjustments to nutrition strategies should be made for these population groups.
Alan J. McCubbin, Bethanie A. Allanson, Joanne N. Caldwell Odgers, Michelle M. Cort, Ricardo J.S. Costa, Gregory R. Cox, Siobhan T. Crawshay, Ben Desbrow, Eliza G. Freney, Stephanie K. Gaskell, David Hughes, Chris Irwin, Ollie Jay, Benita J. Lalor, Megan L.R. Ross, Gregory Shaw, Julien D. Périard and Louise M. Burke
Nicole C.A. Strock, Kristen J. Koltun, Emily A. Southmayd, Nancy I. Williams and Mary Jane De Souza
Energy deficiency in exercising women can lead to physiological consequences. No gold standard exists to accurately estimate energy deficiency, but measured-to-predicted resting metabolic rate (RMR) ratio has been used to categorize women as energy deficient. The purpose of the study was to (a) evaluate the accuracy of RMR prediction methods, (b) determine the relationships with physiological consequences of energy deficiency, and (c) evaluate ratio thresholds in a cross-sectional comparison of ovulatory, amenorrheic, or subclinical menstrual disturbances in exercising women (n = 217). Dual-energy X-ray absorptiometry (DXA) and indirect calorimetry provided data on anthropometrics and energy expenditure. Harris–Benedict, DXA, and Cunningham (1980 and 1991) equations were used to estimate RMR and RMR ratio. Group differences were assessed (analysis of variance and Kruskal–Wallis tests); logistic regression and Spearman correlations related ratios with consequences of energy deficiency (i.e., low total triiodothyronine; TT3). Sensitivity and specificity calculations evaluated ratio thresholds. Amenorrheic women had lower RMR (p < .05), DXA ratio (p < .01), Cunningham1980 (p < .05) and Cunningham1991 (p < .05) ratio, and TT3 (p < .01) compared with the ovulatory group. Each prediction equation overestimated measured RMR (p < .001), but predicted (p < .001) and positively correlated with TT3 (r = .329–.453). A 0.90 ratio threshold yielded highest sensitivity for Cunningham1980 (0.90) and Harris–Benedict (0.87) methods, but a higher ratio threshold was best for DXA (0.94) and Cunningham1991 (0.92) methods to yield a sensitivity of 0.80. In conclusion, each ratio predicted and correlated with TT3, supporting the use of RMR ratio as an alternative assessment of energetic status in exercising women. However, a 0.90 ratio cutoff is not universal across RMR estimation methods.
Anna E. Voskamp, Senna van den Bos, Carl Foster, Jos J. de Koning and Dionne A. Noordhof
Background: Gross efficiency (GE) declines during high-intensity exercise. Increasing extracellular buffer capacity might diminish the decline in GE and thereby improve performance. Purpose: To examine if sodium bicarbonate (NaHCO3) supplementation diminishes the decline in GE during a 2000-m cycling time trial. Methods: Sixteen male cyclists and 16 female cyclists completed 4 testing sessions including a maximal incremental test, a familiarization trial, and two 2000-m GE tests. The 2000-m GE tests were performed after ingestion of either NaHCO3 supplements (0.3 g/kg body mass) or placebo supplements (amylum solani, magnesium stearate, and sunflower oil capsules). The GE tests were conducted using a double-blind, randomized, crossover design. Power output, gas exchange, and time to complete the 2000-m time trials were recorded. Capillary blood samples were analyzed for blood bicarbonate, pH, and lactate concentration. Data were analyzed using magnitude-based inference. Results: The decrement in GE found after the 2000-m time trial was possibly smaller in the male and female groups after NaHCO3 than with placebo ingestion, with the effect in both groups combined being unclear. The effect on performance was likely trivial for males (placebo 164.2 [5.0] s, NaHCO3 164.3 [5.0] s; Δ0.1; ±0.6%), unclear for females (placebo 178.6 [4.8] s, NaHCO3 178.0 [4.3] s; Δ−0.3; ±0.5%), and very likely trivial when effects were combined. Blood bicarbonate, pH, and lactate concentration were substantially elevated from rest to pretest after NaHCO3 ingestion. Conclusions: NaHCO3 supplementation results in an unclear effect on the decrease in GE during high-intensity exercise and in a very likely trivial effect on performance.
James A. Betts, Javier T. Gonzalez, Louise M. Burke, Graeme L. Close, Ina Garthe, Lewis J. James, Asker E. Jeukendrup, James P. Morton, David C. Nieman, Peter Peeling, Stuart M. Phillips, Trent Stellingwerff, Luc J.C. van Loon, Clyde Williams, Kathleen Woolf, Ron Maughan and Greg Atkinson
Michal Wilk, Michal Krzysztofik, Milosz Drozd and Adam Zajac
Purpose: Resistance training is one of the key components influencing power output. Previous studies directed at power development through the use of postactivation potentiation have analyzed resistance exercises at volitional or fast tempo of movement in the entire cycle, without control of the duration of the concentric and eccentric phases of movement. To date, no scientific studies have explored the effects of varied movement tempo on the level of power output, velocity, and postactivation potentiation efficiency. Methods: During the experimental sessions, study participants performed 3 sets (Sets1–3) of the bench-press exercise using 70% 1-repetition maximum and 2 different tempos of movement: 2/0/X/0 eccentric medium tempo (ECCMED) and 6/0/X/0 eccentric slow tempo (ECCSLO). Results: Post hoc analysis demonstrated significant differences in values of peak (P PEAK) and mean (P MEAN) power between Sets1–3 measured for the ECCMED (2/0/X/0) tempo. The values of P MEAN in Set3 (492.15 [87.61] W) were significantly higher than in Set2 (480.05 [82.10] W) and Set1 (467.65 [79.18] W). Similarly, the results of P PEAK in Set3 (713.10 [132.72] W) were significantly higher than those obtained in Set2 (702.25 [129.5] W) and Set1 (671.55 [115.79] W). For the ECCSLO tempo (6/0/X/0) in Set2 (587.9 [138.48] W), the results of P PEAK were significantly higher than in Set1 (565.7 [117.37] W) and Set3 (563.1 [124.93] W). Conclusions: The results of this study indicate that the postactivation potentiation effect is observed for both slow and medium tempos of movement.
Gavriil G. Arsoniadis, Gregory C. Bogdanis, Gerasimos Terzis and Argyris G. Toubekis
Purpose: To examine the acute effect of dry-land strength training on physiological and biomechanical parameters in a subsequent swim training session. Methods: Twelve male swimmers (age: 19.0 [2.2] y, peak oxygen uptake: 65.5 [11.4] mL·kg−1·min−1) performed a 5 × 200-m test with progressively increasing intensity. Blood lactate (BL) concentration was measured after each 200-m bout, and the speed corresponding to 4 mmol·L−1 (V4) was calculated. In the experimental (EXP) and control (CON) conditions, swimmers participated in a swim training session consisting of 1000-m warm-up, a bout of 10-second tethered swimming sprint, and 5 × 400 m at V4. In EXP condition, swimmers completed a dry-land strength training session (load: 85% of 1-repetition maximum) 15 minutes before the swimming session. In CON condition, swimmers performed the swimming session only. Oxygen uptake, BL concentration, arm-stroke rate, arm-stroke length, and arm-stroke efficiency were measured during the 5 × 400 m. Results: Force in the 10-second sprint was not different between conditions (P = .61), but fatigue index was higher in the EXP condition (P = .03). BL concentration was higher in EXP condition and showed large effect size at the fifth 400-m repetition compared with CON condition (6.4 [2.7] vs 4.6 [2.8] mmol·L−1, d = 0.63). During the 5 × 400 m, arm-stroke efficiency remained unchanged, arm-stroke length was decreased from the third repetition onward (P = .01), and arm-stroke rate showed a medium increment in EXP condition (d = 0.23). Conclusions: Strength training completed 15 minutes before a swim training session caused moderate changes in biomechanical parameters and increased BL concentration during swimming. Despite these changes, swimmers were able to maintain force and submaximal speed during the endurance training session.
Joel M. Garrett, Stuart R. Graham, Roger G. Eston, Darren J. Burgess, Lachlan J. Garrett, John Jakeman and Kevin Norton
Purpose: To determine the typical variation of variables from a countermovement jump (CMJ) test and a submaximal run test (SRT), along with comparing the sensitivity of each test for the detection of practically important changes within high-performance Australian rules football players. Methods: A total of 23 professional and semiprofessional Australian rules football players performed 6 CMJs and three 8-second 50-m runs every 30 seconds (SRT), 7 days apart. Absolute and trial-to-trial reliability was represented as a coefficient of variation, CV (±90% confidence intervals). Test–retest reliability was examined using the magnitude of the difference (effect size [±90% confidence interval]) from week 1 to week 2. The smallest worthwhile change was calculated as 0.25 × SD. Results: Good reliability (CVs = 6.6%–9.3%) was determined for all variables except eccentric displacement (CV = 12.8%), with no clear changes observed in any variables between week 1 and week 2. All variables from the SRT possessed a CV less than smallest worthwhile change, indicating an ability to detect practically important changes in performance. Only peak velocity from the CMJ test possessed a CV less than smallest worthwhile change, exhibiting a limitation of this test in detecting practically meaningful changes within this environment. Conclusions: The results suggest that while all variables possess acceptable reliability, a SRT might offer to be a more sensitive monitoring tool than a CMJ test within high-performance Australian rules football, due to its greater ability for detecting practically important changes in performance.
Andrea R. Taliaferro and Sean M. Bulger
The purpose of this study was to determine expert consensus regarding the essential characteristics of adapted physical education practicum experiences for preservice physical educators. Researchers used a 3-round Delphi procedure involving the repeated circulation of an online questionnaire to a panel of content experts (N = 24). During Round 1, panelists generated 70 items in response to an open-ended prompt. Then, panelists rated these recommendations on importance and feasibility in the following rounds. After the third round, 23 items were eliminated for failing to reach consensus. Of the remaining 47 items, 24 were both very important and feasible (both means >6), 21 were very important (mean ≥ 6) and probably feasible (mean ≥ 5), and 2 were feasible (mean ≥ 6) and moderately important (mean ≥ 5). Four major themes were identified through a post hoc qualitative cluster analysis: program context, teaching and learning activities, outcomes/soft skills, and evaluation of instructor performance.
Pierre Lepage, Gordon A. Bloom and William R. Falcão
The purpose of this study was to understand the learning experiences and acquisition of knowledge of youth parasport coaches. Five able-bodied male participants (M = 39 years old), who coached youth with a physical disability for an average of 7.4 years, participated in individual interviews. An inductive thematic analysis identified patterns within and across the data, allowing for description and interpretation of the meaning and importance of the themes. The results showed that coaches learned mostly from informal experiences, particularly through mentoring, trial and error, or use of technology. In addition, these learning opportunities were influenced by personal, environmental, and social factors. These findings can help to guide current and future generations of coaches of youth participants with a physical disability by highlighting available resources and addressing several barriers and facilitators to their learning.