Novel nutrition strategies to maintain skill performance in academy soccer players

The present thesis reports on 4 studies on soccer-specific skill performance in academy male soccer players and novel nutritional strategies that could be used in order to help maintain skill. The first study reported in this thesis investigated how the consumption of 250 mL of a 12% carbohydrate-electrolyte beverage, both before the start of a 90-min soccer match simulation and at half time, influenced the preservation of soccer-specific abilities (specifically, dribbling, and passing proficiency), sprinting speed, and anaerobic endurance running capacity. The main finding from this study was that higher passing scores were consistently attained by players using both their dominant and non-dominant feet from the 60-min mark onward in the match simulation when ingesting the carbohydrate-electrolyte beverage. Notably, this sustained skill performance was achieved without a decline in passing speed. Interestingly, passing speed was better maintained particularly on the non-dominant foot when the players consumed the 60g of carbohydrates. Concomitantly, high-intensity running capacity was improved when the participants ingested the 12% carbohydrate-electrolyte solution compared with placebo; all of these positive findings occurred with minimal impact on gut comfort. In the second study, the test-rest reliability of soccer-specific skills was assessed using a modified version of the Russell et al (2011) soccer match simulation protocol. The results suggested that the modified soccer match simulation protocol exhibited promising reliability for most of the evaluated skills. Good to excellent reliability was reported for passing speed and accuracy and sprint speed. However, dribbling and shooting variables showed lower reliability. Additionally, it was determined that the modified version of the protocol could be easily incorporated into professional club settings without the need for specialised equipment. The third study identified that a single dose of a beverage containing 300 mg of coffeeberry ingested one hour before a soccer-specific skill assessment, conducted under rested conditions, did not result in any significant alteration in soccer skill performance compared with placebo. Moreover, it was concluded that it would be prudent to explore similar studies involving activities that induce physical and/or mental fatigue to better understand how coffeeberry might mitigate the negative impact of fatigue on soccer-specific skill performance. In the fourth and final study, the primary aim was to examine the impact of a single pre-exercise dose of a beverage containing 300 mg of coffeeberry on soccer skill performance throughout a 45-min period of simulated soccer-match play and on soccer skills evaluated after exercise-induced fatigue. The study confirmed that the consumption of coffeeberry extract could be advantageous in preserving some aspects of soccer-specific skill performance under exercise conditions. Specifically, it demonstrated notable maintenance of passing performance with retention of passing speed and accuracy during a 45-min simulated soccer match

Influence of Peak Menstrual Cycle Hormonal Changes on Restoration of Fluid Balance After Induced Dehydration

The present study examined the impact of hormonal differences between late follicular (LF) and midluteal (ML) phases on restoration of fluid balance following dehydration. Ten eumenorrheic female participants were dehydrated by 2% of their body mass through overnight fluid restriction followed by exercise-heat stress. Trials were undertaken during the LF (between Days 10 and 13 of the menstrual cycle) and ML phases (between Days 18 and 23 of the menstrual cycle) with one phase repeated to assess reliability of observations. Following dehydration, participants ingested a volume equivalent to 100% of mass loss of a commercially available sports drink in four equal volumes over 30 min. Mean serum values for steroid hormones during the ML (estradiol [E2]: 92 ± 11 pg/ml, progesterone: 19 ± 4 ng/ml) and LF (estradiol [E2]: 232 ± 64 pg/ml, progesterone: 3 ± 2 ng/ml) were significantly different between phases. Urine tests confirmed no luteinizing hormone surge evident during LF trials. There was no effect of menstrual cycle phase on cumulative urine volume during the 3-hr rehydration period (ML: 630 [197–935] ml, LF: 649 [180–845] ml) with percentage of fluid retained being 47% (33–85)% on ML and 46% (37–89)% on LF (p = .29). There was no association between the progesterone:estradiol ratio and fluid retained in either phase. Net fluid balance, urine osmolality, and thirst intensity were not different between phases. No differences in sodium (ML: −61 [−36 to −131] mmol, LF: −73 [−5 to −118] mmol; p = .45) or potassium (ML: −36 [−11 to −80] mmol, LF: −30 [−19 to −89] mmol; p = .96) balance were observed. Fluid replacement after dehydration does not appear to be affected by normal hormonal fluctuations during the menstrual cycle in eumenorrheic young women

Ingesting a 12% carbohydrate-electrolyte beverage before each half of a soccer match simulation facilitates retention of passing performance and improves high-intensity running capacity in academy players

This study investigated the influence of ingesting a 12% carbohydrate plus electrolyte (CHO-E) solution providing 60 g of carbohydrate before each half of a 90-min soccer match simulation (SMS) protocol on skill performance, sprint speed and high-intensity running capacity. Eighteen elite academy (age 18±2 y) soccer players ingested two 250 mL doses (pre-exercise and at half-time) of a 12% CHO-E solution or electrolyte placebo administered in a double-blind randomised cross-over design. During an indoor (artificial grass pitch) SMS, dribbling, passing and sprint performance were assessed, and blood was drawn for glucose and lactate analysis. High-intensity running capacity was assessed following the SMS. Dribbling speed/accuracy and sprint speed remained unchanged throughout the SMS. Conversely, passing accuracy for both dominant (mean % difference (95% CI): 9 (3-15)) and non-dominant (mean % difference (95% CI): 13 (6-20)) feet was better maintained during the SMS on CHO-E (p < 0.05), with passing speed better maintained in the non-dominant foot (mean % difference (95% CI): 5.3 (0.7 to 9.9), p=0.032). High-intensity running capacity was greater in CHO-E vs. placebo (mean % difference (95% CI): 13 (6 to 20), p=0.010). Capillary blood glucose concentration was higher in CHO-E than placebo at half-time (CHO-E: 5.8±0.5 mM vs. placebo: 4.1±0.4 mM, p=0.001) and following the high-intensity running capacity test (CHO-E: 4.9±0.4 mM vs. placebo: 4.30.4 mM, p=0.001). Ingesting a 12% CHO-E solution before each half of a match can aid in the maintenance of soccer-specific skill performance, particularly on the non-dominant foot, and improves subsequent high-intensity running capacity

Fluid and electrolyte balance considerations for female athletes

This review explores the effects of oestrogen and progesterone fluctuations across the menstrual cycle on fluid and electrolyte balance. The review aims to provide information on this topic for the exercising female but also for researchers working in this field. Beginning with a basic introduction to fluid and electrolyte balance, the review goes on to describe how oestrogen and progesterone have independent and integrated roles to play in the regulation of fluid and electrolyte balance. Despite evidence that oestrogen can influence the osmotic threshold for arginine vasopressin release, and that progesterone can influence aldosterone production, these actions do not appear to influence fluid retention, plasma volume changes at rest and during exercise, or electrolyte losses. However, the large inter-individual variations in hormonal fluctuations throughout the menstrual cycle may mean that specific individuals with high fluctuations could experience disturbances in their fluid and electrolyte balance. During phases of oestrogen dominance (e.g. late-follicular phase) heat dissipation is promoted, while progesterone dominance (e.g. mid-luteal phase) promotes heat conservation with overall higher basal body temperature. However, these responses do not consistently lead to any change in observed sweat rates, heat-stress, or dehydration during exercise. Finally, the literature does not support any difference in fluid retention during post-exercise rehydration periods conducted at different menstrual cycle phases. Although these mean responses largely reveal no effects on fluid and electrolyte balance, further research is required particularly in those individuals who experience high hormonal fluctuations, and greater exploration of oestrogen to progesterone interactions is warranted

A preliminary study of the reliability of soccer skill tests within a modified soccer match simulation protocol

Aim: This study examined test-retest reliability of soccer-specific skills within a modified version of the soccer match simulation (SMS) protocol. Methods: Ten professional youth academy soccer players (18 ± 1 years) from the United Kingdom completed 30 minutes of the modified SMS on two occasions under standardised conditions. During each trial, participants performed 20-m dribbling, short passing (4.2-m), long passing (7.9-m), shooting skills, and 15-m sprints within four blocks of soccer specific activity. Results: Collapsed normative data (mean (SD)) for trial 1 and trial 2 for dribbling speed was 2.7 (0.2) m/s, for sprint speed 5.9 (0.4) m/s, for short pass speed 11.1 (0.5) km/h, for long pass speed was 12.2 (0.5) km/h, and for shooting speed was 13.3 (0.4) km/h. Mean results from trial 1 and trial 2 were not different for all measures evaluated (P > 0.05). Good to excellent reliability (ICC 0.76-0.99) was observed for long and short passing speed, shooting speed, sprint speed, and long pass accuracy, with CVs typically < 5-10%. Moderate reliability (ICC 0.50-0.75) was observed for dribbling speed. Poor reliability (ICC < 0.50) was observed for dribbling accuracy and shooting accuracy. Conclusions The reliability of the modified version of the SMS protocol is promising for most of the skills assessed, with the exception of dribbling and shooting accuracy in this group of professional youth soccer players. The modified protocol is easy to implement within professional clubs without specialist equipment, but due to the limited sample size the reliability requires further confirmation in a larger sample.Output Status: Forthcoming/Available Onlin

Effect of Drinking Rate on the Retention of Water or Milk Following Exercise-Induced Dehydration

This study investigated the effect of drinking rate on fluid retention of milk and water following exercise-induced dehydration. In Part A, 12 male participants lost 1.9% ± 0.3% body mass through cycle exercise on four occasions. Following exercise, plain water or low-fat milk equal to the volume of sweat lost during exercise was provided. Beverages were ingested over 30 or 90 min, resulting in four beverage treatments: water 30 min, water 90 min, milk 30 min, and milk 90 min. In Part B, 12 participants (nine males and three females) lost 2.0% ± 0.3% body mass through cycle exercise on four occasions. Following exercise, plain water equal to the volume of sweat lost during exercise was provided. Water was ingested over 15 min (DR15), 45 min (DR45), or 90 min (DR90), with either DR15 or DR45 repeated. In both trials, nude body mass, urine volume, urine specific gravity and osmolality, plasma osmolality, and subjective ratings of gastrointestinal symptoms were obtained preexercise and every hour for 3 hr after the onset of drinking. In Part A, no effect of drinking rate was observed on the proportion of fluid retained, but milk retention was greater (p

Guidelines for the use and interpretation of assays for monitoring autophagy (4th edition)

In 2008, we published the first set of guidelines for standardizing research in autophagy. Since then, this topic has received increasing attention, and many scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Thus, it is important to formulate on a regular basis updated guidelines for monitoring autophagy in different organisms. Despite numerous reviews, there continues to be confusion regarding acceptable methods to evaluate autophagy, especially in multicellular eukaryotes. Here, we present a set of guidelines for investigators to select and interpret methods to examine autophagy and related processes, and for reviewers to provide realistic and reasonable critiques of reports that are focused on these processes. These guidelines are not meant to be a dogmatic set of rules, because the appropriateness of any assay largely depends on the question being asked and the system being used. Moreover, no individual assay is perfect for every situation, calling for the use of multiple techniques to properly monitor autophagy in each experimental setting. Finally, several core components of the autophagy machinery have been implicated in distinct autophagic processes (canonical and noncanonical autophagy), implying that genetic approaches to block autophagy should rely on targeting two or more autophagy-related genes that ideally participate in distinct steps of the pathway. Along similar lines, because multiple proteins involved in autophagy also regulate other cellular pathways including apoptosis, not all of them can be used as a specific marker for bona fide autophagic responses. Here, we critically discuss current methods of assessing autophagy and the information they can, or cannot, provide. Our ultimate goal is to encourage intellectual and technical innovation in the field