Practical precooling strategies and cycling time trial performance

Whole-body precooling can improve endurance exercise performance, especially in the heat; however there are logistical considerations that restrict the use of various precooling strategies prior to actual competition. Precooling is proposed to collectively reduce deep skin and body temperature and in effect, increase the heat storage capacity of an athlete, thereby allowing a greater amount of work to be completed prior to attainment of a critical core temperature. While there is a sound theoretical basis for implementing precooling to improve cycling time trial performance in the heat, the practicalities of employing effective precooling strategies in the field warrant further investigation. The purpose of this thesis was to investigate the effectiveness of various practical precooling strategies for reducing core temperature and improving cycling time trial performance in hot (32-35ºC; 50-60% r.h.) and temperate (20-22 ºC; 50-60% r.h.) conditions. The first three studies of this thesis involved the manipulation of body temperature via a range of precooling strategies that were applied under hot and humid environmental conditions. In study 1, eight precooling strategies involving external application or internal ingestion of cold water and ice were evaluated for their effectiveness in lowering deep body temperature, with due consideration regarding their application in a practical setting. The novel strategy identified in this study, which involved the combined application of iced towels and ingestion of an ice-slurry (“slushie”) made from sports drink, was then compared with an established cooling strategy (Study 2). Both the new and established precooling strategies achieved noticeable cooling effects (moderate and very large, respectively) but only the new strategy enhanced mean power output (3%, 8W) during a 46.4 km laboratory-based cycling protocol, with performance improvements detected in the second half of the time trial. This strategy was also found to be practical to implement. In study 3, practical precooling and hyperhydration were evaluated to assess whether their combination offered further benefits to endurance cycling time trial performance, when assessed over the same laboroatory protocol. The main findings indicated that practical precooling and hyperhydration, with and without the co-ingestion of glycerol, failed to achieve a clear enhancement of cycling performance. However, when practical precooling and hyperhydration without glycerol was compared to the control condition (i.e., hyperhydration alone), there was a 2% (30 s) improvement in cycling performance time, which was detected in the second half (climb 2) of the time trial. These improvements may be partially explained by a lower percieved exertion, which was observed during the initial 10 km of the time trial. Study 4 was conducted to validate anecdotal reports and laboratory-based observations of thermoregulatory strain in elite cyclists during a real-life event performed in temperate environmental conditions. The rationale for this study was to determine whether the magnitude of hyperthermia achieved during real-life cycling performed in temperate conditions was high enough to possibly benefit from precooling. Although fluid losses during racing were mild (1.3%), cyclists experienced hyperthermia, at magnitudes typically associated with heat-stress induced fatigue (\u3e67% of observations). Therefore, in the final study of this thesis, the effects of practical precooling on 45.6 km cycling time trial performance was examined in both hot (32˚C) and temperate (21˚C) environmental conditions. The effectiveness of practical precooling was enhanced in temperate conditions, such that there was a greater magnitude of body cooling achieved. However, this strategy failed to provide a clear performance benefit in temperate conditions and instead, was likely to impair performance, particularly in the first (flat) section of the time trial course (-2.3%, 8 W). Collectively, the studies contained within this thesis have contributed to the development of a practical precooling strategy involving the combined application of iced towels and ingestion of a slushie made from sports drink. These studies confirm the effectiveness of this novel strategy in reducing skin and core temperature and enhancing heat storage capacity prior to the commencement of exercise. However, the associated reduction in thermoregulatory strain translates into a performance enhancement in hot, but not temperate conditions. This thesis has provided detailed information regarding the range of factors that may be involved in altering the efficacy of a precooling manoeuvre and offers a highly practical insight into the application of precooling strategies aimed at improving field-based sports performance specific to time trial cycling

Effect of Protein Sources on Early Turkey Performance and Gastrointestinal Tract Development

Nutrition during the early life of turkey poults has a long lasting impact on bird performance, as well as gastrointestinal tract (GIT) development. This research focused on understanding the impact of protein source provided in the feed on performance and GIT development. All statistical analysis was completed using Proc Mixed in SAS 9.3 and significant differences were set at P≤0.05, while trends were identified for P≤0.10. The first study (5 x 2 factorial arrangement) evaluated apparent metabolizable energy (AMEn) and apparent ileal amino acid digestibility (AIAAD) of five high protein feed ingredients (soybean meal, SBM; corn gluten meal, CGM; canola protein concentrate, CPC; fish meal, FM; and porcine meal, PM) in male broiler chickens at 5 and 21 d with 6 replications of 30 and 8 chicks, respectively. The AMEn was not affected by bird age for CPC, FM, CGM, and SBM, however, the d 5 value for PM was higher than the d 21 value. The response of AIAAD was variable and dependent on amino acid and protein source, but overall, there was an increase in AIAAD with increasing age, with the largest increase observed for CGM. These AMEn and AIAAD values were then used to formulate the diets for a second experiment. The diets for this experiment consisted of a high SBM control diet, and four additional diets with either CPC, FM, PM, or CGM replacing 25% of the protein that was supplied by SBM in the control diet. This experiment was set up as a completely randomized design with four pens of 23 turkey poults per protein source. Body weights, feed and water intake, and mortality were recorded on a weekly basis. At the same time, four pens of 21 poults per protein source were used to study the impact of these diets on GIT development and blood metabolic profiling. At hatch, placement, d 1, 2, 3, 5, 7, 14, and 21, intestinal tract and tissue weights were collected and recorded (2 poults per replication per time point). Ileal segments were collected at hatch, placement, d 1, 3, 5, and 7 from 2 poults per replicate pen of the SBM and PM diets to study the effect of diet on intestinal morphology, number of goblet cells, and transcript abundance for selected genes relating to barrier function and inflammation. Blood samples were also drawn at these time points for blood metabolite analysis. Data were analyzed as a 5x9 factorial for tissues weights, a 2x5 factorial for histology and gene expression, and a 5x5 factorial for blood analysis. Planned contrasts were used on the performance, tissue, and blood data to compare the SBM diet to the average of the remaining diets, the PM diet to the average of the remaining diets, and the addition of animal or vegetable proteins. Inclusion of an additional protein source increased body weight up to 14 d, in comparison to poults fed the SBM diet, but feed efficiency and water consumption were not affected. The effect of diet on tissue weights were small, with the exception of the pancreas weight, which were higher in the birds fed vegetable protein diets. Age had an effect on all tissue weights, which peaked between d 2 and 7, as well as on digestive tract morphology and gene expression. There was an increase in gene expression between placement and d 1, which could illustrate the importance of feed as an activator of barrier function and the immune system. The goblet cell counts revealed a greater proportion of neutral goblet cells in PM fed birds associated with accelerated mucus maturation. The research shows there are benefits to limiting the amount of SBM provided in early turkey feeds, especially prior to two weeks of age

Analysis of the Effects of Dietary Pattern on the Oral Microbiome of Elite Endurance Athletes

Although the oral microbiota is known to play a crucial role in human health, there are few studies of diet x oral microbiota interactions, and none in elite athletes who may manipulate their intakes of macronutrients to achieve different metabolic adaptations in pursuit of optimal endurance performance. The aim of this study was to investigate the shifts in the oral microbiome of elite male endurance race walkers from Europe, Asia, the Americas and Australia, in response to one of three dietary patterns often used by athletes during a period of intensified training: a High Carbohydrate (HCHO; = 9; with 60% energy intake from carbohydrates; ~8.5 g kg day carbohydrate, ~2.1 g kg day protein, 1.2 g kg day fat) diet, a Periodised Carbohydrate (PCHO; = 10; same macronutrient composition as HCHO, but the intake of carbohydrates is different across the day and throughout the week to support training sessions with high or low carbohydrate availability) diet or a ketogenic Low Carbohydrate High Fat (LCHF; = 10; 0.5 g kg day carbohydrate; 78% energy as fat; 2.1 g kg day protein) diet. Saliva samples were collected both before (Baseline; BL) and after the three-week period (Post treatment; PT) and the oral microbiota profiles for each athlete were produced by 16S rRNA gene amplicon sequencing. Principal coordinates analysis of the oral microbiota profiles based on the weighted UniFrac distance measure did not reveal any specific clustering with respect to diet or athlete ethnic origin, either at baseline (BL) or following the diet-training period. However, discriminant analyses of the oral microbiota profiles by Linear Discriminant Analysis (LDA) Effect Size (LEfSe) and sparse Partial Least Squares Discriminant Analysis (sPLS-DA) did reveal changes in the relative abundance of specific bacterial taxa, and, particularly, when comparing the microbiota profiles following consumption of the carbohydrate-based diets with the LCHF diet. These analyses showed that following consumption of the LCHF diet the relative abundances of and spp. were decreased, and the relative abundance of spp. was increased. Such findings suggest that diet, and, in particular, the LCHF diet can induce changes in the oral microbiota of elite endurance walkers

Ingesting a bitter solution: The sweet touch to increasing short-term cycling performance

Purpose: The authors investigated the potential benefit of ingesting 2 mM of quinine (bitter tastant) on a 3000-m cycling time-trial (TT) performance. Methods: Nine well-trained male cyclists (maximal aerobic power: 386 [38] W) performed a maximal incremental cycling ergometer test, three 3000-m familiarization TTs, and four 3000-m intervention TTs (∼4 min) on consecutive days. The 4 interventions were (1) 25 mL of placebo, (2) a 25-mL sweet solution, and (3) and (4) repeat 25 mL of 2-mM quinine solutions (Bitter1 and Bitter2), 30 s before each trial. Participants self-selected their gears and were only aware of distance covered. Results: Overall mean power output for the full 3000 m was similar for all 4 conditions: placebo, 348 (45) W; sweet, 355 (47) W; Bitter1, 354 (47) W; and Bitter2, 355 (48) W. However, quinine administration in Bitter1 and Bitter2 increased power output during the first kilometer by 15 ± 11 W and 21 ± 10 W (mean ± 90% confidence limits), respectively, over placebo, followed by a decay of 34 ± 32 W during Bitter1 and Bitter2 during the second kilometer. Bitter2 also induced a 11 ± 13-W increase during the first kilometer compared with the sweet condition. Conclusions: Ingesting 2 mM of quinine can improve cycling performance during the first one-third of a 3000-m TT and could be used for sporting events lasting ∼80 s to potentially improve overall performance

Athlete Perceptions of Flavored, Menthol-enhanced Energy Gels Ingested Prior to Running in the Heat

Thermal perception during exercise is known to influence endurance performance and the onset of fatigue. L-menthol, an organic compound derived from peppermint, evokes a cooling sensation through its action on TRPM8 channels which also respond to cold stimuli. Recent work identified that the internal application of menthol-enhanced fluids can be ergogenic during exercise in the heat. Hence, the addition of menthol to energy gels may be practical and beneficial for athletes. PURPOSE: To determine athlete acceptability and preferences for flavored energy gels with different menthol concentrations. METHODS: With a randomized, crossover, and double-blind placebo-controlled design, 27 endurance athletes (34.8±6.7 y, BMI: 21.7±1.6 kg·m-2, 9 female) ingested an energy gel with a menthol additive at relative concentrations: low (0.1%), medium-low (0.3%), medium-high (0.5%), high (0.7%), or a non-menthol, flavor-matched placebo (CON), on separate days before outdoor running sessions. Athletes rated the gels for cooling sensation, irritation (tingling/burning), flavor, and overall experience on 100-point sensory and hedonic labeled magnitude scales. The duration of any cooling sensation was also reported. Repeated measures ANOVAs with a Bonferroni adjustment for pairwise comparisons were used to determine differences. RESULTS: All menthol gels successfully delivered a greater cooling sensation compared to CON (7.4±8.1 AU) with a significantly greater response for 0.7% (59.9±20.5 AU) and 0.5% (57.7±21.8 AU), compared to all others, which were both rated “moderate-strong” for intensity. Irritation intensity was higher for all menthol gels compared to CON (3.4±7.2 AU), and for 0.7% compared to 0.1% (31.1±31.0 vs 16.3±21.0 AU, p=0.041), with none reported higher than a “mild-moderate” intensity. The menthol gels delivered a significantly longer cooling duration (range: 12.3-19.6 min) compared to CON (2.2±4.8 min) with no significant difference between menthol gels. Ratings of overall experience and flavor were not different between gels (p\u3e.05). CONCLUSION: A flavored energy gel with the addition of menthol at 0.1-0.7% provides a cooling sensation for athletes when ingested before exercise. The 0.5% concentration is recommended to maximize the cooling sensation of the gel whilst minimizing irritation

Manipulation of Muscle Creatine and Glycogen Changes Dual X-ray Absorptiometry Estimates of Body Composition

Standardizing a dual x-ray absorptiometry (DXA) protocol is thought to provide a reliable measurement of body composition. Purpose: We investigated the effects of manipulating muscle glycogen and creatine content independently and additively on DXA estimates of lean mass. Method: Eighteen well-trained male cyclists undertook a parallel group application of creatine loading (n = 9) (20 g·d−1 for 5 d loading; 3 g·d−1 maintenance) or placebo (n = 9) with crossover application of glycogen loading (12 v 6 g·kg−1 BM per day for 48 h) as part of a larger study involving a glycogen-depleting exercise protocol. Body composition, total body water, muscle glycogen and creatine content were assessed via DXA, bioelectrical impedance spectroscopy and standard biopsy techniques. Changes in the mean were assessed using the following effect-size scale: > 0.2 small, > 0.6, moderate, > 1.2 large and compared with the threshold for the smallest worthwhile effect of the treatment. Results: Glycogen loading, both with and without creatine loading, resulted in substantial increases in estimates of lean body mass (mean ± SD; 3.0% ± 0.7% and 2.0% ± 0.9%) and leg lean mass (3.1% ± 1.8% and 2.6% ± 1.0%) respectively. A substantial decrease in leg lean mass was observed after the glycogen depleting condition (−1.4% ± 1.6%). Total body water showed substantial increases after glycogen loading (2.3% ± 2.3%), creatine loading (1.4% ± 1.9%) and the combined treatment (2.3% ± 1.1%). Conclusions: Changes in muscle metabolites and water content alter DXA estimates of lean mass during periods in which minimal change in muscle protein mass is likely. This information needs to be considered in interpreting the results of DXA-derived estimates of body composition in athletes

Katanin catalyzes microtubule depolymerization independently of tubulin C-terminal tails

Microtubule network remodeling is an essential process for cell development, maintenance, cell division, and motility. Microtubule‐severing enzymes are key players in the remodeling of the microtubule network; however, there are still open questions about their fundamental biochemical and biophysical mechanisms. Here, we explored the ability of the microtubule‐severing enzyme katanin to depolymerize stabilized microtubules. Interestingly, we found that the tubulin C‐terminal tail (CTT), which is required for severing, is not required for katanin‐catalyzed depolymerization. We also found that the depolymerization of microtubules lacking the CTT does not require ATP or katanin\u27s ATPase activity, although the ATP turnover enhanced depolymerization. We also observed that the depolymerization rate depended on the katanin concentration and was best described by a hyperbolic function. Finally, we demonstrate that katanin can bind to filaments that lack the CTT, contrary to previous reports. The results of our work indicate that microtubule depolymerization likely involves a mechanism in which binding, but not enzymatic activity, is required for tubulin dimer removal from the filament ends

Athlete perceptions of flavored, menthol-enhanced energy gels ingested prior to endurance exercise in the heat

Background L-menthol evokes a cooling sensation by activating cold sensing cation channels. Menthol-enhanced fluids can be ergogenic during exercise in the heat by improving thermal perception; hence, the addition of menthol to energy gels may benefit athletes. Previously, unflavored menthol gels were deemed acceptable at 0.1% concentration, but no research has been undertaken on menthol gels with additional flavoring. Therefore, we determined athlete perceptions of flavored energy gels with different menthol concentrations. Methods With a randomized, crossover, double-blind, placebo-controlled design, 27 athletes (34.8 ± 6.7 y, 9 females) ingested an energy gel with either 0.1%, 0.3%, 0.5%, or 0.7% menthol concentration, or a non-menthol, flavor-matched placebo (CON), on separate occasions before outdoor exercise. Gels were rated for cooling sensation, irritation, flavor, and overall experience on 100-point sensory and hedonic labeled magnitude scales. The duration of any cooling sensation was also reported. Results All menthol gels delivered a greater cooling sensation compared to CON (7.4 ± 8.1 AU) with a significantly greater response for 0.7% (59.9 ± 20.5 AU) and 0.5% (57.7 ± 21.8 AU), compared to all others. Irritation was higher for all menthol gels compared to CON (3.4 ± 7.2 AU) and for 0.7% compared to 0.1% (31.1 ± 31.0 vs. 16.3 ± 21.0 AU, p = 0.041), with none rated above a ‘mild-moderate’ intensity. The menthol gels delivered a significantly longer cooling sensation duration (12.3-19.6 min) versus CON (2.2 ± 4.8 min) with no difference between menthol gels. Conclusion A flavored menthol energy gel at 0.1–0.7% concentration provides a cooling sensation for athletes when ingested before exercise. The 0.5% concentration is recommended to maximize the cooling sensation whilst minimizing irritation

A menthol-enhanced “cooling” energy gel does not influence laboratory time trial performance in trained runners

l-menthol (menthol) is an organic compound derived from peppermint which imparts a refreshing mint flavor and aroma to oral hygiene products, chewing gum, and topical analgesics. Menthol has been identified as a non-thermal sensory cooling strategy for athletes when ingested or mouth-rinsed during exercise in hot environments. Therefore, sports nutrition products delivering a controlled concentration of menthol could be beneficial for athletes exercising in the heat. We sought to test the performance and perceptual outcomes of a novel menthol energy gel during treadmill running in the heat (33 °C, 49% RH). Fourteen trained runners (mean ± SD; age: 31 ± 6 years, VO2max: 56.5 ± 10.1 mL·kg−1·min−1, BMI: 23.2 ± 2.4 kg/m2; six female) participated in a randomized, crossover, double-blind, and placebo-controlled study. A menthol-enhanced energy gel (0.5% concentration; MEN) or flavor-matched placebo (PLA) was ingested 5 min before and again at 20 and 40 min of a 40 min treadmill exercise preload at 60% VO2max, followed by a 20 min self-paced time trial. The total distance, vertical distance, perceptual measures (thermal comfort, thermal sensation, rating of perceived exertion, and affect), and cognitive performance via computerized neurocognitive assessment were measured. No difference between 20 min self-paced time trial total distance (MEN: 4.22 ± 0.54 km, PLA: 4.22 ± 0.55 km, p = 0.867), vertical distance (MEN: 49.2 ± 24.6 m, PLA: 44.4 ± 11.4 m, p = 0.516), or any perceptual measures was observed (all p > 0.05). Cognitive performance was not different between the trials (all p > 0.05). These results suggest that a menthol energy gel is not superior to a non-menthol gel in terms of performance or perception during treadmill running in the heat. More research is needed to confirm whether these findings translate to ecologically valid settings, including outdoor exercise in ambient heat and during competition