Fuel for the Work Required: A Theoretical Framework for Carbohydrate Periodization and the Glycogen Threshold Hypothesis

Elite collegiate swimmers do not meet sport nutrition recommendations during heavy training: effects of sex and within-day nutrient timing

BACKGROUND

Compared to the general population, athletes experience high energy expenditures requiring increased energy and macronutrient intakes to sustain training and optimize performance. While the International Olympic Committee (IOC) and International Society for Sports Nutrition (ISSN) have established recommendations for nutrient intakes, many athletes do not meet the recommended daily allowance (RDA) for the general population, and sport and sex-specific differences are not well documented. Exploration of within-day energy balance (WDEB) shows athletes may achieve energy balance by the end of the day but may present with poor WDEB. Data support that female athletes are at greater risk of nutrient deficiencies than their male counterparts, and it is unclear whether swimmers meet sport-specific nutrient intake and timing recommendations. Following our previous WDEB analysis, the purpose of this investigation was to assess dietary macronutrient intake as related to RDAs (USDA and IOC/ISSN), within-day macronutrient timing, and associated sex differences in swimmers.

METHODS

In elite male and female swimmers (n = 25; 18-22 yr), we assessed energy intake (EI), total daily energy expenditure (TDEE), macronutrient intake (fat (FAT), protein (PRO), carbohydrate (CHO)) and timing during heavy training. Frequency analysis was utilized to determine the number of athletes meeting general and athlete-specific RDAs. Repeated-measures ANOVA was used to assess nutrient timing across sex groups.

RESULTS

When compared to IOC/ISSN daily recommendations, only 6/25 swimmers met FAT intake, 7/25 met CHO intake, and 24/25 met PRO intake IOC/ISSN daily recommendations.Males had greater EI and TDEE compared to females (p < 0.05). PRO consumption (% of EI) was a larger percentage of total intake in male vs females (28 ± 5% vs 23 ± 3%; F = 2.996; p = 0.014). No swimmers met CHO recommendations (g⋅kg-1) pre- or during exercise for the first daily training session. 13/25 met pre-exercise CHO recommendations, while 6/25 and 11/25 met during and post-exercise CHO recommendations for the second training session. Repeated measures ANOVA revealed effects of sex and time on intake (g⋅kg LBM-1⋅hr-1) for FAT (Sex; F = 5.659, p = 0.26; time; F = 12.068, p = 0.006) and PRO (Sex; F = 6.719, p = 0.016; time; F = 13.177, p = 0.011). There was a significant sex*time interaction for CHO consumption (F = 6.520, p = 0.017).

CONCLUSION

The results from this study demonstrate significant sex-differences, indicating that most swimmers meet athlete-specific recommendations for PRO, but not CHO or FAT intake. CHO timing for pre-, during, and post-exercise was met by only 52% swimmers. Results suggest that swimmers should prioritize CHO intake, emphasized around and during training bouts.

Minimum Overnight Interstitial Glucose Concentration in Professional Cyclists During Two Consecutive Annual Training Camps: The Limited Impact of Daily Exercise Energy Expenditure

This observational study investigated the use of continuous glucose monitoring (CGM) in a team of professional cyclists without diabetes during two consecutive annual training camps. The goal of the study was twofold: to present the aggregated CGM metrics such as day/overnight CGM average (DAYAVG/OVNAVG) for this group of professional cyclists and to study the association between exercise energy expenditure (megajoules per day), carbohydrate intake (grams), and minimum overnight CGM values (millimoles per liter). Linear mixed models were employed in the analysis. Data were available for 26 cyclists (22 participated in both training camps). CGM levels reported (DAYAVG = 6.37 ± 0.54 mmol/L and OVNAVG = 5.30 ± 0.52 mmol/L), are not typically seen in healthy individuals not engaged in intensive exercise routines. Results showed that minimum overnight CGM values significantly fluctuated throughout the training camp, but a statistically significant association between exercise energy expenditure (p = .0839) or carbohydrate intake (p = .059) and minimum overnight CGM values could not be detected. This research contributes to the literature on CGM use in professional athletes and underscores the need for further studies to fully understand the benefits and limitations of CGM to guide sports performance.

Predicting VO2max Using Lung Function and Three-Dimensional (3D) Allometry Provides New Insights into the Allometric Cascade (M0.75)

BACKGROUND

Using directly measured cardiorespiratory fitness (i.e. VO2max) in epidemiological/population studies is rare due to practicality issues. As such, predicting VO2max is an attractive alternative. Most equations that predict VO2max adopt additive rather than multiplicative models despite evidence that the latter provides superior fits and more biologically interpretable models. Furthermore, incorporating some but not all confounding variables may lead to inflated mass exponents (∝ M0.75) as in the allometric cascade.

OBJECTIVE

Hence, the purpose of the current study was to develop multiplicative, allometric models to predict VO2max incorporating most well-known, but some less well-known confounding variables (FVC, forced vital capacity; FEV1, forced expiratory volume in 1 s) that might provide a more dimensionally valid model (∝ M2/3) originally proposed by Astrand and Rodahl.

METHODS

We adopted the following three-dimensional multiplicative allometric model for VO2max (l⋅min-1) = Mk1·HTk2·WCk3·exp(a + b·age + c·age2 + d·%fat)·ε, (M, body mass; HT, height; WC, waist circumference; %fat, percentage body fat). Model comparisons (goodness-of-fit) between the allometric and equivalent additive models was assessed using the Akaike information criterion plus residual diagnostics. Note that the intercept term 'a' was allowed to vary for categorical fixed factors such as sex and physical inactivity.

RESULTS

Analyses revealed that significant predictors of VO2max were physical inactivity, M, WC, age2, %fat, plus FVC, FEV1. The body-mass exponent was k1 = 0.695 (M0.695), approximately∝M2/3. However, the calculated effect-sizes identified age2 and physical inactivity, not mass, as the strongest predictors of VO2max. The quality-of-fit of the allometric models were superior to equivalent additive models.

CONCLUSIONS

Results provide compelling evidence that multiplicative allometric models incorporating FVC and FEV1 are dimensionally and theoretically superior at predicting VO2max(l⋅min-1) compared with additive models. If FVC and FEV1 are unavailable, a satisfactory model was obtained simply by using HT as a surrogate.

Nutritional Strategies to Improve Post-exercise Recovery and Subsequent Exercise Performance: A Narrative Review

Post-exercise recovery strategies influence the body's ability to restore physiological homeostasis, replenish energy stores, repair muscle damage, and promote desired adaptations, which improve exercise performance. This narrative review examines the impact of nutritional strategies commonly used for enhancing recovery and subsequent exercise performance, particularly when athletes face short recovery periods. Carbohydrate ingestion is essential for glycogen replenishment, especially within the initial hours post-exercise, with its impact dependent on the types, timing, and amount. Protein is essential for accelerating muscle recovery and achieving a positive nitrogen balance, depending on the type and dosage. The co-ingestion of carbohydrates with proteins or fats is explored for its role in maximizing glycogen resynthesis and muscle repair, with evidence supporting the addition of protein to suboptimal carbohydrate intake for enhanced recovery. Moreover, this review addresses the potential benefits of creatine and caffeine co-ingestion for accelerating glycogen synthesis and improving subsequent performance. Hydration strategies, including the use of milk-based beverages and electrolyte solutions, are also discussed, emphasizing their importance in maintaining fluid balance and optimizing recovery. This review also highlights the emerging role of micronutrients such as omega-3 fatty acids, antioxidants, and sodium bicarbonate in reducing muscle damage and improving acid-base balance. Evidence supports the tailored use of these nutritional strategies, particularly for athletes managing tight competition/training schedules. Future research should focus on refining individualized approaches for recovery and investigating the impact of novel supplements on subsequent performance.

Protein Nutrition for Endurance Athletes: A Metabolic Focus on Promoting Recovery and Training Adaptation

The purpose of this narrative review is to provide an evidence-based update on the protein needs of endurance athletes with a focus on high-quality metabolic studies conducted on the topics of recovery and training adaptation over the past decade. We use the term 'protein needs' to delineate between the concepts of a daily protein requirement and per meal protein recommendations when devising scientific evidence-based protein guidelines for the endurance athlete to promote post-exercise recovery, enhance the adaptive response to endurance training and improve endurance performance. A habitual protein intake of 1.5 g/kg of body mass (BM)-1·day-1 is typical in male and female endurance athletes. Based on findings from a series of contemporary protein requirement studies, the evidence suggests a daily protein intake of ~ 1.8 g·kgBM-1·day-1 should be advocated for endurance athletes, with the caveat that the protein requirement may be further elevated in excess of 2.0 g·kgBM-1·day-1 during periods of carbohydrate-restricted training and on rest days. Regarding protein recommendations, the current lack of metabolic studies that determine the dose response of muscle protein synthesis to protein ingestion in relation to endurance exercise makes it difficult to present definitive guidelines on optimal per meal protein intakes for endurance athletes. Moreover, there remains no compelling evidence that co-ingesting protein with carbohydrate before or during endurance exercise confers any performance advantage, nor facilitates the resynthesis of liver or muscle glycogen stores during recovery, at least when carbohydrate recommendations are met. However, recent evidence suggests a role for protein nutrition in optimising the adaptive metabolic response to endurance training under conditions of low carbohydrate and/or energy availability that represent increasingly popular periodised strategies for endurance athletes.

A Review of Carbohydrate Supplementation Approaches and Strategies for Optimizing Performance in Elite Long-Distance Endurance

Carbohydrate supplementation is a common practice among endurance athletes participating in long-distance competitions. However, glycogen storage regulation, in-competition blood glucose levels, and their relationship with athletic performance are influenced by multiple factors. This review summarizes the recent research progress on carbohydrate supplementation, addressing its applications in the pre-, during-, and post-competition phases. It explores variables that influence the effectiveness of carbohydrate supplementation and provides a summary of strategies, based on six key aspects: carbohydrate properties, multi-nutrient interactions, gastrointestinal function, individual differences (such as age and gender), environmental conditions, and psychological factors. The combination of different types, ratios, and concentrations of carbohydrates has been demonstrated to enhance the efficiency of carbohydrate digestion and absorption. The synergistic combination of protein, sodium, and caffeine intake demonstrates enhanced efficacy in carbohydrate supplementation strategies. Gastrointestinal tolerance training for carbohydrate supplementation has been identified as an effective measure to alleviate gastrointestinal discomfort during high-dose carbohydrate intake. The adjustment of the carbohydrate-to-fat ratio and the type of carbohydrate intake has been found to mitigate the impact of gender and menstrual cycles on glycogen storage and substrate utilization. Modifying the timing of glycogen storage and regulating the concentration and temperature of carbohydrate solutions during competition have been demonstrated to facilitate coping with the elevated energy expenditure and metabolic substrate shift from fat to carbohydrates, triggered by a combination of environmental and psychological factors, including special environmental and climatic conditions (e.g., high altitude, high temperature, high humidity, and cold) and emotional states (e.g., pre-competition stress and anxiety during the competition). To achieve precise carbohydrate supplementation for athletes in major events under various competitive environments, it is necessary to quantitatively assess the effects of carbohydrate supplementation, supported by mechanistic studies. This can be achieved by utilizing wearable devices to monitor the entire competition, coupled with data collection technologies, such as high-throughput profiling. Furthermore, emerging data analytics techniques, such as machine learning and causal inference, should be leveraged to refine supplementation strategies.

A Novel Method to Predict Carbohydrate and Energy Expenditure During Endurance Exercise Using Measures of Training Load

BACKGROUND

Sports nutrition guidelines recommend carbohydrate (CHO) intake be individualized to the athlete and modulated according to changes in training load. However, there are limited methods to assess CHO utilization during training sessions.

OBJECTIVES

We aimed to (1) quantify bivariate relationships between both CHO and overall energy expenditure (EE) during exercise and commonly used, non-invasive measures of training load across sessions of varying duration and intensity and (2) build and evaluate prediction models to estimate CHO utilization and EE with the same training load measures and easily quantified individual factors.

METHODS

This study was undertaken in two parts: a primary study, where participants performed four different laboratory-based cycle training sessions, and a validation study where different participants performed a single laboratory-based training session using one of three exercise modalities (cycling, running, or kayaking). The primary study included 15 cyclists (five female; maximal oxygen consumption [ V ˙ O2max], 51.9 ± 7.2 mL/kg/min), the validation study included 21 cyclists (seven female; V ˙ O2max 53.5 ± 11.0 mL/kg/min), 20 runners (six female; V ˙ O2max 57.5 ± 7.2 mL/kg/min), and 18 kayakers (five female; V ˙ O2max 45.6 ± 4.8 mL/kg/min). Training sessions were quantified using six training load metrics: two using heart rate, three using power, and one using perceived exertion. Carbohydrate use and EE were determined separately for aerobic (gas exchange) and anaerobic (net lactate accumulation, body mass, and O2 lactate equivalent method) energy systems and summed. Repeated-measures correlations were used to examine relationships between training load and both CHO utilization and EE. General estimating equations were used to model CHO utilization and EE, using training load alongside measures of fitness and sex. Models were built in the primary study and tested in the validation study. Model performance is reported as the coefficient of determination (R2) and mean absolute error, with measures of calibration used for model evaluation and for sport-specific model re-calibration.

RESULTS

Very-large to near-perfect within-subject correlations (r = 0.76-0.96) were evident between all training load metrics and both CHO utilization and EE. In the primary study, all models explained a large amount of variance (R2 = 0.77-0.96) and displayed good accuracy (mean absolute error; CHO = 16-21 g [10-14%], EE = 53-82 kcal [7-11%]). In the validation study, the mean absolute error ranged from 16-50 g [15-45%] for CHO models to 53-182 kcal [9-31%] for EE models. The calibrated mean absolute error ranged from 9-20 g [8-18%] for CHO models to 36-72 kcal [6-12%] for EE models.

CONCLUSIONS

At the individual level, there are strong linear relationships between all measures of training load and both CHO utilization and EE during cycling. When combined with other measures of fitness, EE and CHO utilization during cycling can be estimated accurately. These models can be applied in running and kayaking when used with a calibration adjustment.

The acute and chronic influence of exercise on mitochondrial dynamics in skeletal muscle

Exercise and nutritional modulation are potent stimuli for eliciting increases in mitochondrial mass and function. Collectively, these beneficial adaptations are increasingly recognized to coincide with improvements in skeletal muscle health. Mitochondrial dynamics of fission and fusion are increasingly implicated as having a central role in mediating aspects of key organelle adaptations that are seen with exercise. Exercise-induced mitochondrial adaptation dynamics that have been implicated are 1) increases to mitochondrial turnover, resulting from elevated rates of mitochondrial synthesis (biogenesis) and degradative (mitophagy) processes and 2) morphological changes to the three-dimensional (3-D) tubular network, known as the mitochondrial reticulum, that mitochondria form in skeletal muscle. Notably, mitochondrial fission has also been implicated in coordinating increases in mitophagy, following acute exercise. Furthermore, increased fusion following exercise training promotes increased connectivity of the mitochondrial reticulum and is associated with improved metabolism and mitochondrial function. However, the molecular basis and fashion in which exercise infers beneficial mitochondrial adaptations through mitochondrial dynamics remains to be fully elucidated. This review attempts to highlight recent developments investigating the effects of exercise on mitochondrial dynamics, while attempting to offer a perspective of the methodological refinements and potential variables, such as substrate/glycogen availability, which should be considered going forward.

The Diet Quality of Ultramarathon Runners Taking Part in an Australian Event: A Cross-Sectional Explorative Study

Background/Objectives: Ultramarathon runners exceed the physical activity guidelines and in doing so are constantly exposed to physical and metabolic demands, requiring strategic dietary practices to support training, performance, and recovery. This study aimed to assess the diet quality and nutrient intake in runners enrolled in an Australian-based ultramarathon. Methods: A 3-day food diary was collected using the Australian smartphone application 'Easy Diet Diary' during both peak and taper periods. Macronutrient and micronutrient intakes were analysed using the AUSNUT 2011-2013 food composition database within the Foodworks professional software, and diet quality was evaluated using the Healthy Eating Index for Australians (HEIFA-2013). Results: A total of 26 runners participated in the study. The results revealed that, although runners met or exceeded protein recommendations, their carbohydrate intake fell short of endurance-specific guidelines, whilst total dietary fat intake exceeded recommendations (excluding long-chain polyunsaturated fatty acids). Diet quality scores averaged 63.1 out of 100, reflecting moderate alignment with dietary recommendations. Fruit, vegetable, and wholegrain food groups were inadequately consumed. Conclusions: The findings indicate that ultramarathon runners who easily exceed physical activity recommendations, may paradoxically consume suboptimal diets, characterized by insufficient intake of core food groups such as whole grains and fruits, alongside excessive consumption of discretionary items. This dietary pattern may not only elevate their risk of chronic disease but also impair optimal performance by compromising recovery and adaptation to training. Further research is warranted to better understand the dietary behaviors and nutritional needs of this population.

Carbohydrate Restriction During Recovery from High-Intensity-Interval Training Enhances Fat Oxidation During Subsequent Exercise and Does Not Compromise Performance When Combined With Caffeine

Background

Carbohydrate restriction can alter substrate utilization and potentially impair endurance performance in female athletes. Caffeine intake may mitigate this performance decrements.

Objectives

The aim of this study was to test the hypothesis that maximal fat oxidation (MFO) rate would be enhanced in the carbohydrate (CHO) restricted state in trained females. Additionally, the impact of caffeine intake before exercise under conditions of low CHO availability was examined on time-trial performance.

Methods

By using a randomized, double-blinded, placebo-controlled, crossover design, 17 female endurance athletes completed 3 experimental blocks. Each block consisted of high-intensity-interval-training (HIT) in the evening, followed by a fat oxidation test to measure MFO rate and a 20-min time trial (20TT) performance the next morning. The females received standardized, isoenergetic diets with different timing of CHO intake: No CHO between exercise sessions without (FASTED) or with 300 mg caffeine (4.1-4.9 mg/kg body mass) (FASTED+CAFF) before morning exercise tests or CHO ingestion after HIT (FED).

Results

MFO rate was higher in FASTED+CAFF (0.57 ± 0.04 g/min) than that in FED (0.50 ± 0.04 g/min, P = 0.039) but not different from FASTED condition. Power output performed during the 20TT was higher after FASTED+CAFF (189 ± 9 W) than that after FASTED (+6.9%, P = 0.022) and FED (+4.2%, P = 0.054).

Conclusions

CHO restriction during recovery from HIT enhances MFO rate during subsequent exercise compared with the condition where CHOs were consumed during the recovery period, but the effect was only significant when CHO restriction was combined with caffeine supplementation before the MFO test. In addition, caffeine ingestion before exercise in the CHO-restricted state compensates for the decreased work capacity associated with the CHO-restricted state.

Responses to Exercise with Low Carbohydrate Availability on Muscle Glycogen and Cell Signaling: A Systematic Review and Meta-analysis

BACKGROUND

The growing interest in how exercise and carbohydrate (CHO) restriction may modify molecular responses that promote endurance adaptations has led to many interesting controversies.

OBJECTIVE

We conducted a systematic review and a meta-analysis regarding the effect of low-carbohydrate availability (LOW) pre-, during, or post-exercise, on the mRNA content of commonly measured genes involved in mitochondrial biogenesis (PGC-1α, TFAM mRNA) and metabolism (PDK4, UCP3 and GLUT4 mRNA), and on muscle glycogen levels, compared with a high-CHO (CON) condition.

METHODS

MEDLINE, Scopus, and Web of Science databases were searched following the PRISMA 2020 guidelines (with an end date of November 2023). In total, 19 randomized-controlled studies were considered for inclusion. We evaluated the methodological quality of all studies using the Cochrane Risk of Bias tool for randomized clinical studies. A meta-analysis was performed using a random effects model to calculate the standardized mean difference (SMD), estimated by Hedges' g, and 95% confidence intervals (CIs).

RESULTS

The LOW condition was associated with an increased mRNA content of several genes during the early recovery period post-exercise, such as PDK4 (SMD 1.61; 95% CI 0.80-2.42), GLUT4 (SMD 1.38; 95% CI 0.46-2.30), and UCP3 (SMD 2.05; 95% CI 0.40-3.69). However, overall, there was no significant effect on the mRNA content of PGC-1α or TFAM. Finally, CHO restriction and exercise significantly reduced muscle glycogen levels (SMD 3.69; 95% CI 2.82-5.09). A meta-analysis of subgroups from studies with a difference in muscle glycogen concentration of > 200 mmol kg dw-1 between the LOW and CON conditions showed an increase in exercise-induced PGC-1α mRNA (SMD 2.08; 95% CI 0.64-3.52; p = 0.005; I2 = 75%) and a greater effect in PDK4 and GLUT4 mRNA.

CONCLUSION

The meta-analysis results show that CHO restriction was associated with an increase in the exercise-induced mRNA content of PDK4, UCP3, and GLUT4, but not the exercise-induced mRNA content of PGC-1ɑ and TFAM. However, when there were substantial differences in glycogen depletion between CON and LOW CHO conditions (> 200 mmol kg dw-1), there was a greater effect of CHO restriction on the exercise-induced mRNA content of metabolic genes, and an increase in exercise-induced PGC-1α mRNA.

Acute effects of intra-training carbohydrate ingestion in CrossFit® trained adults: a randomized, triple-blind, placebo-controlled crossover trial

Carbohydrate (CHO) intake during exercise could decrease the subjective perceived exertion and promote recovery; however, the effects of intra-training CHO ingestion remain uncertain in CrossFit® (CF) sessions. Therefore, the aim of this randomized, triple-blind, placebo-controlled crossover trial was to investigate the effect of acute CHO intake during a CF session on the delayed onset muscle soreness (DOMS), the perceived exertion (RPE), performance, recovery, and metabolic markers (capillary lactate and glucose) in CF athletes. Twenty-three male athletes trained in CF ingested CHO (60 g of maltodextrin + fructose) or a placebo (PLA) during a CF session. DOMS was assessed 24 and 48 h after the CF session. The Counter Movement Jump (CMJ) test and the Deep Squat test at 70% of the athlete's body weight (AST70) were performed before, immediately after, and 24 h after the session. Perceived exertion, Feeling Scale (FS), Gastrointestinal Distress Score (GDS), heart rate, capillary lactate, and glucose were assessed across the session. CHO supplementation did not improve DOMS (all P ≥ 0.127), CMJ, or AST70 parameters (all P ≥ 0.053) compared to PLA. There were no differences between CHO and PLA in RPE, FS, GDS, heart rate (all P ≥ 0.088), performance (e.g., nº of repetitions; all P ≥ 0.556), or lactate levels (P = 0.810). However, glucose levels increased from the back squat to the WOD and remained stable after the AMRAP (P < 0.001). In conclusion, acute CHO intake during a CF session did not improve DOMS, perceived exertion, performance, recovery, or metabolic markers in CF athletes. TRN: NCT06440343. Date: 2024-05-10.

Nutritional approaches applied to recovery of skeletal muscle injury immobilization: a review of nutrition aid for sport trauma

Skeletal muscle (SM) injuries are a very common occurrence among athletes during training and/or competitive periods, resulting in time loss and absence from sports. Of several existing interventions to improve SM recovery, the nutritional approach has emerged as integral part to improve the physiological response and maintain the body composition to promote a rapid and safe return to play. Growing evidence supports that the physiological response to SM injuries results in a number of changes, suggesting the relevance of a personalized nutritional approach, according to the degree of immobilization, SM mass loss, strength and function. Therefore, we aimed to review the current evidence of the nutritional approach applied to SM injuries recovery in athletes, highlighting energy intake, use the main nutrients and elements for the SM recovery, such as proteins, carbohydrates, vitamins and omega-3 fatty acids. Currently, evidence from injured athletes is scarce, and so specific guidelines cannot be established, calling from greater research into nutritional interventions in SM injury recovery in athletes.

Evaluating the evening carbohydrate dilemma: the effect of within-the-day carbohydrate periodization on body composition and physical fitness

PURPOSE

To assess the effects of carbohydrate timing and type on body composition and physical fitness.

METHODS

Forty-two healthy, trained male volunteers underwent a four-week intervention, randomly divided into three groups: (i) Sleep Low-No Carbohydrates (SL-NCHO): consuming all carbohydrate intake at regular intervals prior to evening training, (ii) Sleep High-Low Glycemic Index (SH-LGI), and (iii) Sleep High-High Glycemic Index (SH-HGI). In both SH-LGI and SH-HGI, carbohydrates were distributed throughout the day, both pre-(60% of total intake) and post-evening training (40% of total intake). The SH-LGI and SH-HGI groups diverged in evening carbohydrate quality, featuring LGI and HGI foods, respectively. All participants performed a standardized exercise program combining resistance exercise and high-intensity interval training. Body composition was assessed using skinfold measurements and bioelectrical impendence analysis. Physical fitness was assessed by measuring VO2max, Visual Reaction Time (VRT), Countermovement Jump (CMJ), and 1-repetition maximum (1RM) in hack squat, chest press, shoulder press, and lat-pulldown exercises.

RESULTS

There was a significant time-effect on both body composition and physical fitness indices. Bodyfat percentage decreased by an average of 1.5% (p < 0.001), fat-mass by 1.4 kg (p < 0.001) and fat-free mass increased by 0.9 kg (p = 0.006). A time-effect was also observed in VO2max, CMJ, 1RM testing, and VRT (all p < 0.05). There were no significant differences among interventions.

CONCLUSIONS

A balanced dietary plan with sufficient nutrient and energy intake promotes body composition optimization and physical fitness, independently of carbohydrate type or timing. This study points towards implementing flexible nutrition interventions, emphasizing the potential of tailored dietary strategies to optimize health and physical fitness.

TRIAL REGISTRATION NUMBER

The trial was registered at clinicaltrials.gov as NCT05464342.

Evidence-based sports supplements: A redox analysis

Despite the overwhelming number of sports supplements on the market, only seven are currently recognized as effective. Biological functions are largely regulated through redox reactions, yet no comprehensive analysis of the redox properties of these supplements has been compiled. Here, we analyze the redox characteristics of these seven supplements: bicarbonates, beta-alanine, caffeine, creatine, nitrates, carbohydrates, and proteins. Our findings suggest that all sports supplements exhibit some degree of redox activity. However, the precise physiological implications of these redox properties remain unclear. Future research, employing unconventional perspectives and methodologies, will reveal new redox pixels of the exercise physiology and sports nutrition picture.

Delaying post-exercise carbohydrate intake impairs next-day exercise capacity but not muscle glycogen or molecular responses

AIM

To investigate how delayed post-exercise carbohydrate intake affects muscle glycogen, metabolic- and mitochondrial-related molecular responses, and subsequent high-intensity interval exercise (HIIE) capacity.

METHODS

In a double-blind cross-over design, nine recreationally active men performed HIIE (10 × 2-min cycling, ~94% W˙peak) in the fed state, on two occasions. During 0-3 h post-HIIE, participants drank either carbohydrates ("Immediate Carbohydrate" [IC], providing 2.4 g/kg) or water ("Delayed Carbohydrate" [DC]); total carbohydrate intake over 24 h post-HIIE was matched (~7 g/kg/d). Skeletal muscle (sampled pre-HIIE, post-HIIE, +3 h, +8 h, +24 h) was analyzed for whole-muscle glycogen and mRNA content, plus signaling proteins in cytoplasmic- and nuclear-enriched fractions. After 24 h, participants repeated the HIIE protocol until failure, to test subsequent HIIE capacity; blood lactate, heart rate, and ratings of perceived effort (RPE) were measured throughout.

RESULTS

Muscle glycogen concentrations, and relative changes, were similar between conditions throughout (p > 0.05). Muscle glycogen was reduced from baseline (mean ± SD mmol/kg dm; IC: 409 ± 166; DC: 352 ± 76) at post-HIIE (IC: 253 ± 96; DC: 214 ± 82), +3 h (IC: 276 ± 62; DC: 269 ± 116) and + 8 h (IC: 321 ± 56; DC: 269 ± 116), returning to near-baseline by +24 h. Several genes (PGC-1ɑ, p53) and proteins (p-ACCSer79, p-P38 MAPKThr180/Tyr182) elicited typical exercise-induced changes irrespective of condition. Delaying carbohydrate intake reduced next-day HIIE capacity (5 ± 3 intervals) and increased RPE (~2 ratings), despite similar physiological responses between conditions.

CONCLUSION

Molecular responses to HIIE (performed in the fed state) were not enhanced by delayed post-exercise carbohydrate intake. Our findings support immediate post-exercise refueling if the goal is to maximize next-day HIIE capacity and recovery time is ≤24 h.

The fourth dimension: physiological resilience as an independent determinant of endurance exercise performance

Endurance exercise performance is known to be closely associated with the three physiological pillars of maximal O2 uptake (V ̇ O 2 max $\dot{V}_{{\rm O}_{2}{\rm max}}$ ), economy or efficiency during submaximal exercise, and the fractional utilisation ofV ̇ O 2 max $\dot{V}_{{\rm O}_{2}{\rm max}}$ (linked to metabolic/lactate threshold phenomena). However, while 'start line' values of these variables are collectively useful in predicting performance in endurance events such as the marathon, it is not widely appreciated that these variables are not static but are prone to significant deterioration as fatiguing endurance exercise proceeds. For example, the 'critical power' (CP), which is a composite of the highest achievable steady-state oxidative metabolic rate and efficiency (O2 cost per watt), may fall by an average of 10% following 2 h of heavy intensity cycle exercise. Even more striking is that the extent of this deterioration displays appreciable inter-individual variability, with changes in CP ranging from <1% to ∼32%. The mechanistic basis for such differences in fatigue resistance or 'physiological resilience' are not resolved. However, resilience may be important in explaining superlative endurance performance and it has implications for the physiological evaluation of athletes and the design of interventions to enhance performance. This article presents new information concerning the dynamic plasticity of the three 'traditional' physiological variables and argues that physiological resilience should be considered as an additional component, or fourth dimension, in models of endurance exercise performance.

Energy Balance and Dietary Intake in Young Rugby Players during a Pre-Season Micro-Cycle: A Cluster Analysis

Rugby players must develop excellent levels of conditioning during adolescence. However, this pivotal period of life is also characterized by a surge in biological growth, which further increases the energy and nutritional requirements of this population. This study examined within-individual differences in energy intake (EI) and energy balance (EB) of 46 young rugby players during a pre-season micro-cycle. Two clusters were identified with significantly different characteristics and EB states, suggesting that young rugby players adjust their EI to match their body composition goals. The first cluster is characterized by players with a low body fat% (12.87 ± 2.53). They had a positive EB (330 ± 517 kcal), suggesting a goal of increasing muscle mass. Conversely, the second cluster is characterized by a higher body fat% (23.1 ± 1.6, p < 0.005) and reported a negative, lower EB (-683 ± 425 kcal, p < 0.005), suggesting a goal focused on reducing fat mass. Although our study provides more optimistic results than previous ones regarding the high risk of inadequate EI in young rugby players, we emphasize the importance of rigorous nutritional support, especially for players aiming to lose weight, to avoid severe caloric restriction, as well as the downstream effects of such practices on their nutritional status, given the higher risk of macro- (e.g., CHO < 6 g/kg/d) and micronutrient (e.g., iron < 11 mg/d, calcium < 1300 mg/d, vitamin D < 5 mg/d) deficiencies.

Nutrition for Children and Adolescents Who Practice Sport: A Narrative Review

At a developmental age, adequate physical activity is fundamental to overall health and well-being and preventing obesity. Moreover, establishing active behavior can help children and adolescents meet their growth and neurodevelopmental goals. Nutritional requirements vary according to intensity, frequency, and practiced physical activity or sport; therefore, pediatricians should give children and adolescents and their families adequate counseling, avoiding both nutrient deficiencies and excessive or inadequate supplement intake. The focus should be not only on sports performance but also on the child's well-being, growth, and neurodevelopment. Our narrative review aims to discuss the nutritional needs of children and adolescents who practice physical activity, non-competitive sports activity, and elite sports activity while also analyzing the role of food supplements and the risk of eating disorders within this category of subjects.

Carbohydrate Ingestion Increases Interstitial Glucose and Mitigates Neuromuscular Fatigue during Single-Leg Knee Extensions

INTRODUCTION

We aimed to investigate the neuromuscular contributions to enhanced fatigue resistance with carbohydrate (CHO) ingestion and to identify whether fatigue is associated with changes in interstitial glucose levels assessed using a continuous glucose monitor (CGM).

METHODS

Twelve healthy participants (six males, six females) performed isokinetic single-leg knee extensions (90°·s -1 ) at 20% of the maximal voluntary contraction (MVC) torque until MVC torque reached 60% of its initial value (i.e., task failure). Central and peripheral fatigue were evaluated every 15 min during the fatigue task using the interpolated twitch technique and electrically evoked torque. Using a single-blinded crossover design, participants ingested CHO (85 g sucrose per hour), or a placebo (PLA), at regular intervals during the fatigue task. Minute-by-minute interstitial glucose levels measured via CGM and whole blood glucose readings were obtained intermittently during the fatiguing task.

RESULTS

CHO ingestion increased time to task failure over PLA (113 ± 69 vs 81 ± 49 min, mean ± SD; P < 0.001) and was associated with higher glycemia as measured by CGM (106 ± 18 vs 88 ± 10 mg·dL -1 , P < 0.001) and whole blood glucose sampling (104 ± 17 vs 89 ± 10 mg·dL -1 , P < 0.001). When assessing the values in the CHO condition at a similar time point to those at task failure in the PLA condition (i.e., ~81 min), MVC torque, percentage voluntary activation, and 10 Hz torque were all better preserved in the CHO versus PLA condition ( P < 0.05).

CONCLUSIONS

Exogenous CHO intake mitigates neuromuscular fatigue at both the central and peripheral levels by raising glucose concentrations rather than by preventing hypoglycemia.

A Five-Week Periodized Carbohydrate Diet Does Not Improve Maximal Lactate Steady-State Exercise Capacity and Substrate Oxidation in Well-Trained Cyclists compared to a High-Carbohydrate Diet

There is a growing interest in studies involving carbohydrate (CHO) manipulation and subsequent adaptations to endurance training. This study aimed to analyze whether a periodized carbohydrate feeding strategy based on a daily training session has any advantages compared to a high-carbohydrate diet in well-trained cyclists. Seventeen trained cyclists (VO2peak = 70.8 ± 6.5 mL·kg-1·min-1) were divided into two groups, a periodized (PCHO) group and a high-carbohydrate (HCHO) group. Both groups performed the same training sessions for five weeks. In the PCHO group, 13 training sessions were performed with low carbohydrate availability. In the HCHO group, all sessions were completed following previous carbohydrate intake to ensure high pre-exercise glycogen levels. In both groups, there was an increase in the maximal lactate steady state (MLSS) (PCHO: 244.1 ± 29.9 W to 253.2 ± 28.4 W; p = 0.008; HCHO: 235.8 ± 21.4 W to 246.9 ± 16.7 W; p = 0.012) but not in the time to exhaustion at MLSS intensity. Both groups increased the percentage of muscle mass (PCHO: p = 0.021; HCHO: p = 0.042) and decreased the percent body fat (PCHO: p = 0.021; HCHO: p = 0.012). We found no differences in carbohydrate or lipid oxidation, heart rate, and post-exercise lactate concentration. Periodizing the CHO intake in well-trained cyclists during a 5-week intervention did not elicit superior results to an energy intake-matched high-carbohydrate diet in any of the measured outcomes.

Resistance-only and concurrent exercise induce similar myofibrillar protein synthesis rates and associated molecular responses in moderately active men before and after training

Aerobic and resistance exercise (RE) induce distinct molecular responses. One hypothesis is that these responses are antagonistic and unfavorable for the anabolic response to RE when concurrent exercise is performed. This thesis may also depend on the participants' training status and concurrent exercise order. We measured free-living myofibrillar protein synthesis (MyoPS) rates and associated molecular responses to resistance-only and concurrent exercise (with different exercise orders), before and after training. Moderately active men completed one of three exercise interventions (matched for age, baseline strength, body composition, and aerobic capacity): resistance-only exercise (RE, n = 8), RE plus high-intensity interval exercise (RE+HIIE, n = 8), or HIIE+RE (n = 9). Participants trained 3 days/week for 10 weeks; concurrent sessions were separated by 3 h. On the first day of Weeks 1 and 10, muscle was sampled immediately before and after, and 3 h after each exercise mode and analyzed for molecular markers of MyoPS and muscle glycogen. Additional muscle, sampled pre- and post-training, was used to determine MyoPS using orally administered deuterium oxide (D2 O). In both weeks, MyoPS rates were comparable between groups. Post-exercise changes in proteins reflective of protein synthesis were also similar between groups, though MuRF1 and MAFbx mRNA exhibited some exercise order-dependent responses. In Week 10, exercise-induced changes in MyoPS and some genes (PGC-1ɑ and MuRF1) were dampened from Week 1. Concurrent exercise (in either order) did not compromise the anabolic response to resistance-only exercise, before or after training. MyoPS rates and some molecular responses to exercise are diminished after training.

Improved physical performance of elite soccer players based on GPS results after 4 days of carbohydrate loading followed by 3 days of low carbohydrate diet

BACKGROUND

Carbohydrate loading is an established sports nutrition strategy for endur- 16 ance exercise performance. We tested if carbohydrate loading could improve the performance of 17 elite soccer players under ecologically valid circumstances using Global Positioning System (GPS) data.

METHODS

Twenty-two adult Iran Premier league soccer players were divided into a carbohydrate-loading group (CLG) and Control group (CG). The carbohydrate loading group restricted carbohydrate intake for three days to 1.5 g/kg/d while increasing exercise intensity. From days four to seven, exercise intensity was decreased and carbohydrate intake was considerably increased up to 7.5 g/kg/d on the day of the match, during which performance was analyzed using GPS data. The control group performed the same exercise training but maintained their habitual carbohydrate intake of 5-6 g/kg/d. The data were analyzed using a univariate ANCOVA with baseline data from a pre-intervention match as the control variable.

RESULTS

The carbohydrate loading team scored significantly higher on running distance, maximum speed and the number of top and repeated sprints; the carbohydrate loading group scored significantly lower on player load, metabolic power and running imbalance compared to the control team during their match.

CONCLUSIONS

Our findings suggest carbohydrate loading enabled elite soccer players to achieve greater running outputs with greater metabolic efficiency and lower fatigue compared to their habitual diets.

The Physiological Requirements of and Nutritional Recommendations for Equestrian Riders

Equestrian sport is under-researched within the sport science literature, creating a possible knowledge vacuum for athletes and support personnel wishing to train and perform in an evidence-based manner. This review aims to synthesise available evidence from equitation, sport, and veterinary sciences to describe the pertinent rider physiology of equestrian disciplines. Estimates of energy expenditure and the contribution of underpinning energy systems to equestrian performance are used to provide nutrition and hydration recommendations for competition and training in equestrian disciplines. Relative energy deficiency and disordered eating are also considered. The practical challenges of the equestrian environment, including competitive, personal, and professional factors, injury and concussion, and female participation, are discussed to better highlight novelty within equestrian disciplines compared to more commonly studied sports. The evidence and recommendations are supported by example scenarios, and future research directions are outlined.

Association between Variation in Body Fat Mass Magnitude and Intake of Nutrients, including Carbohydrates, Fat, and B Vitamins, in a Cohort of Highly Trained Female Athletes

The most common sports nutrition strategies were constructed not only for maximizing musculoskeletal adaptations to exercise, but also to minimize health risks in athletes. Given the lack of research highlighting the potential effects of the intake of carbohydrates, fats, and B vitamins on body fat percentage in a population of female athletes, this study aimed to elucidate whether the intake of macronutrients and B vitamins could be associated with the variation in body fat percentage in a cohort of professional female athletes. This cross-sectional study was weighted to represent Lithuanian elite female athletes (n = 89). The dietary assessment of the female athletes was carried out using a 3-day dietary recall method. Their body composition was assessed using the bioelectrical impedance analysis method. For females, the reported average intakes of energy, carbohydrates, protein, and fat were 2475 kcal/day, 5.1 g/kg/day, 1.5 g/kg/day, and 36.7%, respectively. Excess B vitamin intake was revealed, ranging within plus 1-2 standard deviations (SDs) around the mean requirements. As a consequence, excessive body fat percentage was potentially factored as a negative outcome in maintaining optimal body composition in female athletes. Multivariate logistic regression analysis of a sample of female athletes revealed that, despite a slightly positive energy balance (∆ 95 kcal/day), the carbohydrate-deficient diet (adjusted odds ratio (aOR) 0.3, 95% confidence interval (CI) 0.1; 0.7), along with higher intakes of vitamin B1 (aOR 2.9, 95% CI 2.6; 7.8), vitamin B2 (aOR 6.7, 95% CI 1.1; 8.3), and vitamin B3 (aOR 1.8, 95% CI 1.4; 7.8) from food, was associated with a lower percentage of body fat. Therefore, more attention should be given to the intake of B vitamins in professional athletes with a range of body fat mass percentages for the purpose of achieving long-term goals of maintaining body composition and fitness.

An online exploratory survey of Australian athletes' and exercisers' use of and attitudes towards ultra-processed sports foods

Sports foods are convenient alternatives to everyday foods to fuel performance. Strong scientific evidence supports their use; however, commercial sports foods are classified by the NOVA system as ultra-processed foods (UPF). Consumption of UPF has been associated with poor mental and physical health, but little is known about athletes' consumption of and attitudes towards sports foods as a source of UPF. The aim of this cross-sectional study was to assess Australian athletes' intake of and attitudes towards sports foods and UPF. Adult athletes were recruited to complete an anonymous online survey via social media between October 2021 and February 2022. Data were analysed using descriptive statistics, and Pearson's χ2 test was used to assess potential relationships between categorical demographic variables and consumption of sports foods. One hundred forty Australian adults participating in recreational (n 55), local/regional (n 52), state (n 11), national (n 14) or international (n 9) sports completed the survey. Ninety-five percent reported consuming sports foods within the past 12 months. Participants consumed sports drinks most commonly (73 %) and isolated protein supplements most frequently (40 % at least once per week). Participants reported everyday foods to be more affordable, taste better, present less risk of banned substances, but less convenient and greater risk of spoilage. Half (51 %) of participants reported concern about health effects of UPF. Participants reported regular UPF consumption despite taste and cost-related preferences for everyday foods and health concerns regarding UPF intake. Athletes may need support to identify and access safe, affordable, convenient, minimally processed alternatives to sports foods.

Exercise metabolism and adaptation in skeletal muscle

Viewing metabolism through the lens of exercise biology has proven an accessible and practical strategy to gain new insights into local and systemic metabolic regulation. Recent methodological developments have advanced understanding of the central role of skeletal muscle in many exercise-associated health benefits and have uncovered the molecular underpinnings driving adaptive responses to training regimens. In this Review, we provide a contemporary view of the metabolic flexibility and functional plasticity of skeletal muscle in response to exercise. First, we provide background on the macrostructure and ultrastructure of skeletal muscle fibres, highlighting the current understanding of sarcomeric networks and mitochondrial subpopulations. Next, we discuss acute exercise skeletal muscle metabolism and the signalling, transcriptional and epigenetic regulation of adaptations to exercise training. We address knowledge gaps throughout and propose future directions for the field. This Review contextualizes recent research of skeletal muscle exercise metabolism, framing further advances and translation into practice.

Carbohydrate, but not fat, oxidation is reduced during moderate-intensity exercise performed in 33 vs. 18 °C at matched heart rates

PURPOSE

Exposure to environmental heat stress increases carbohydrate oxidation and extracellular heat shock protein 70 (HSP70) concentrations during endurance exercise at matched absolute, external work rates. However, a reduction in absolute work rate typically occurs when unacclimated endurance athletes train and/or compete in hot environments. We sought to determine the effect of environmental heat stress on carbohydrate oxidation rates and plasma HSP70 expression during exercise at matched heart rates (HR).

METHODS

Ten endurance-trained, male cyclists performed two experimental trials in an acute, randomised, counterbalanced cross-over design. Each trial involved a 90-min bout of cycling exercise at 95% of the HR associated with the first ventilatory threshold in either 18 (TEMP) or 33 °C (HEAT), with ~ 60% relative humidity.

RESULTS

Mean power output (17 ± 11%, P < 0.001) and whole-body energy expenditure (14 ± 8%, P < 0.001) were significantly lower in HEAT. Whole-body carbohydrate oxidation rates were significantly lower in HEAT (19 ± 11%, P = 0.002), while fat oxidation rates were not different between-trials. The heat stress-induced reduction in carbohydrate oxidation was associated with the observed reduction in power output (r = 0.64, 95% CI, 0.01, 0.91, P = 0.05) and augmented sweat rates (r = 0.85, 95% CI, 0.49, 0.96, P = 0.002). Plasma HSP70 and adrenaline concentrations were not increased with exercise in either environment.

CONCLUSION

These data contribute to our understanding of how moderate environmental heat stress is likely to influence substrate oxidation and plasma HSP70 expression in an ecologically-valid model of endurance exercise.

Environmental heat stress offsets adaptation associated with carbohydrate periodization in trained male triathletes

PURPOSE

Carbohydrate (CHO) intake periodization via the sleep low train low (SL-TL) diet-exercise model increases fat oxidation during exercise and may enhance endurance-training adaptation and performance. Conversely, training under environmental heat stress increases CHO oxidation, but the potential of combined SL-TL and heat stress to enhance metabolic and performance outcomes is unknown.

METHODS

Twenty-three endurance-trained males were randomly assigned to either control (n = 7, CON), SL-TL (n = 8, SLTemp ) or SL-TL + heat stress (n = 8, SLHeat ) groups and prescribed identical 2-week cycling training interventions. CON and SLTemp completed all sessions at 20°C, but SLHeat at 35°C. All groups consumed matched CHO intake (6 g·kg-1 ·day-1 ) but timed differently to promote low CHO availability overnight and during morning exercise in both SL groups. Submaximal substrate utilization was assessed (at 20°C), and 30-min performance tests (at 20 and 35°C) were performed Pre-, Post-, and 1-week post-intervention (Post+1).

RESULTS

SLTemp improved fat oxidation rates at 60% MAP (~66% VO2peak ) at Post+1 compared with CON (p < 0.01). Compared with SLTemp , fat oxidation rates were significantly lower in SLHeat at Post (p = 0.02) and Post+1 (p < 0.05). Compared with CON, performance was improved at Post in SLTemp in temperate conditions. Performance was not different between any groups or time points in hot conditions.

CONCLUSION

SL-TL enhanced metabolic adaptation and performance compared with CON and combined SL-TL and heat stress. Additional environmental heat stress may impair positive adaptations associated with SL-TL.

Impacts of altered exercise volume, intensity, and duration on the activation of AMPK and CaMKII and increases in PGC-1α mRNA

The purpose of this review is to explore and discuss the impacts of augmented training volume, intensity, and duration on the phosphorylation/activation of key signaling protein - AMPK, CaMKII and PGC-1α - involved in the initiation of mitochondrial biogenesis. Specifically, we explore the impacts of augmented exercise protocols on AMP/ADP and Ca²⁺ signaling and changes in post exercise PGC - 1α gene expression. Although AMP/ADP concentrations appear to increase with increasing intensity and during extended durations of higher intensity exercise AMPK activation results are varied with some results supporting and intensity/duration effect and others not. Similarly, CaMKII activation and signaling results following exercise of different intensities and durations are inconsistent. The PGC-1α literature is equally inconsistent with only some studies demonstrating an effect of intensity on post exercise mRNA expression. We present a novel meta-analysis that suggests that the inconsistency in the PGC-1α literature may be due to sample size and statistical power limitations owing to the effect of intensity on PGC-1α expression being small. There is little data available regarding the impact of exercise duration on PGC-1α expression. We highlight the need for future well designed, adequately statistically powered, studies to clarify our understanding of the effects of volume, intensity, and duration on the induction of mitochondrial biogenesis by exercise.

Nutritional Considerations for the Vegan Athlete

Accepting a continued rise in the prevalence of vegan-type diets in the general population is also likely to occur in athletic populations, it is of importance to assess the potential impact on athletic performance, adaptation, and recovery. Nutritional consideration for the athlete requires optimization of energy, macronutrient, and micronutrient intakes, and potentially the judicious selection of dietary supplements, all specified to meet the individual athlete's training and performance goals. The purpose of this review is to assess whether adopting a vegan diet is likely to impinge on such optimal nutrition and, where so, consider evidence based yet practical and pragmatic nutritional recommendations. Current evidence does not support that a vegan-type diet will enhance performance, adaptation, or recovery in athletes, but equally suggests that an athlete can follow a (more) vegan diet without detriment. A clear caveat, however, is that vegan diets consumed spontaneously may induce suboptimal intakes of key nutrients, most notably quantity and/or quality of dietary protein and specific micronutrients (eg, iron, calcium, vitamin B12, and vitamin D). As such, optimal vegan sports nutrition requires (more) careful consideration, evaluation, and planning. Individual/seasonal goals, training modalities, athlete type, and sensory/cultural/ethical preferences, among other factors, should all be considered when planning and adopting a vegan diet.

Nutritional Strategies for Endurance Cyclists - Periodized Nutrition, Ketogenic Diets, and Other Considerations

ABSTRACT

Cycling is a growing sport worldwide since the COVID-19 pandemic. With the growing availability and interest in long distance events, professional and amateur cyclists are pushing themselves further and harder than ever before. Training and nutrition should be understood by the sports medicine professional in order to guide counseling toward proper fueling to avoid health consequences. This article reviews macronutrients and micronutrients, periodized training and nutrition, and the relevance of the ketogenic diet for endurance cyclists riding greater than 90 min.

A novel approach to assess dynamic treatment regimes embedded in a SMART with an ordinal outcome

Sequential multiple assignment randomized trials (SMARTs) are used to construct data-driven optimal intervention strategies for subjects based on their intervention and covariate histories in different branches of health and behavioral sciences where a sequence of interventions is given to a participant. Sequential intervention strategies are often called dynamic treatment regimes (DTR). In the existing literature, the majority of the analysis methodologies for SMART data assume a continuous primary outcome. However, ordinal outcomes are also quite common in clinical practice. In this work, first, we introduce the notion of generalized odds ratio ( G O R $$ GOR $$ ) to compare two DTRs embedded in a SMART with an ordinal outcome and discuss some combinatorial properties of this measure. Next, we propose a likelihood-based approach to estimate G O R $$ GOR $$ from SMART data, and derive the asymptotic properties of its estimate. We discuss alternative ways to estimate G O R $$ GOR $$ using concordant-discordant pairs and two-sample U $$ U $$ -statistic. We derive the required sample size formula for designing SMARTs with ordinal outcomes based on G O R $$ GOR $$ . A simulation study shows the performance of the estimated G O R $$ GOR $$ in terms of the estimated power corresponding to the derived sample size. The methodology is applied to analyze data from the SMART+ study, conducted in the UK, to improve carbohydrate periodization behavior in athletes using a menu planner mobile application, Hexis Performance. A freely available Shiny web app using R is provided to make the proposed methodology accessible to other researchers and practitioners.

The Use of Continuous Glucose Monitors in Sport: Possible Applications and Considerations

This review discusses the potential value of tracking interstitial glucose with continuous glucose monitors (CGMs) in athletes, highlighting possible applications and important considerations in the collection and interpretation of interstitial glucose data. CGMs are sensors that provide real time, longitudinal tracking of interstitial glucose with a range of commercial monitors currently available. Recent advancements in CGM technology have led to the development of athlete-specific devices targeting glucose monitoring in sport. Although largely untested, the capacity of CGMs to capture the duration, magnitude, and frequency of interstitial glucose fluctuations every 1-15 min may present a unique opportunity to monitor fueling adequacy around competitive events and training sessions, with applications for applied research and sports nutrition practice. Indeed, manufacturers of athlete-specific devices market these products as a "fueling gauge," enabling athletes to "push their limits longer and get bigger gains." However, as glucose homeostasis is a complex phenomenon, extensive research is required to ascertain whether systemic glucose availability (estimated by CGM-derived interstitial glucose) has any meaning in relation to the intended purposes in sport. Whether CGMs will provide reliable and accurate information and enhance sports nutrition knowledge and practice is currently untested. Caveats around the use of CGMs include technical issues (dislodging of sensors during periods of surveillance, loss of data due to synchronization issues), practical issues (potential bans on their use in some sporting scenarios, expense), and challenges to the underpinning principles of data interpretation, which highlight the role of sports nutrition professionals to provide context and interpretation.

Post-exercise rehydration: Comparing the efficacy of three commercial oral rehydration solutions

Introduction

This study compared the efficacy of three commercial oral rehydration solutions (ORS) for restoring fluid and electrolyte balance, after exercise-induced dehydration.

Method

Healthy, active participants (N = 20; ♀ = 3; age ∼27 y, V˙O₂peak ∼52 ml/kg/min) completed three randomised, counterbalanced trials whereby intermittent exercise in the heat (∼36°C, ∼50% humidity) induced ∼2.5% dehydration. Subsequently, participants rehydrated (125% fluid loss in four equal aliquots at 0, 1, 2, 3 h) with a glucose-based (G-ORS), sugar-free (Z-ORS) or amino acid-based sugar-free (AA-ORS) ORS of varying electrolyte composition. Urine output was measured hourly and capillary blood samples collected pre-exercise, 0, 2 and 5 h post-exercise. Sodium, potassium, and chloride concentrations in urine, sweat, and blood were determined.

Results

Net fluid balance peaked at 4 h and was greater in AA-ORS (141 ± 155 ml) and G-ORS (101 ± 195 ml) than Z-ORS (-47 ± 208 ml; P ≤ 0.010). Only AA-ORS achieved positive sodium and chloride balance post-exercise, which were greater for AA-ORS than G-ORS and Z-ORS (P ≤ 0.006), as well as for G-ORS than Z-ORS (P ≤ 0.007) from 1 to 5 h.

Conclusion

when provided in a volume equivalent to 125% of exercise-induced fluid loss, AA-ORS produced comparable/superior fluid balance and superior sodium/chloride balance responses to popular glucose-based and sugar-free ORS.

Periodised Carbohydrate Intake Does Not Affect Substrate Oxidation but May Contribute to Endurance Capacity

The aim of this study was to investigate whether periodising carbohydrate intake around specific training sessions will enhance endurance training adaptations.Seventeen healthy recreationally endurance-trained males (n = 5) and females (n = 12) (27.5 ± 5.4 years) participated in a four-week training intervention. Participants were divided into two groups: FASTED (stayed fasted between evening high-intensity interval training session and low-intensity training session in the following morning) and FED (no restriction in food intake). Pre- and post-testing included peak oxygen uptake (VO_2peak), anaerobic capacity, and 60 min submaximal running tests. Fasted venous blood samples were drawn for the determination of triglyceride and glucose concentrations.VO_2peak increased in both FASTED (4.4 ± 3.0%, p = 0.001) and FED (4.6 ± 4.2%, p = 0.017), whereas maximal running velocity increased only in the FASTED (3.5 ± 2.7%, p = 0.002). Lactate concentrations in the anaerobic test after intervention were greater in FASTED than FED (p = 0.025-0.041). Running time in the anaerobic test was improved in FASTED (from 64.1 ± 15.6-86.3 ± 23.2 s, p < 0.001) but not in FED (from 56.4 ± 15.2-66.9 ± 21.3 s, p = 0.099). Substrate oxidation did not change after intervention in either of the groups (p = 0.052-0.597). Heart rate was lower in the submaximal running test in FASTED (p < 0.001) but not in FED (p = 0.097).Training with periodised carbohydrate availability does not have any effect on substrate oxidation. However, it seems to enhance the capacity to perform high-intensity exercise.

Muscle Glycogen Assessment and Relationship with Body Hydration Status: A Narrative Review

Muscle glycogen is a crucial energy source for exercise, and assessment of muscle glycogen storage contributes to the adequate manipulation of muscle glycogen levels in athletes before and after training and competition. Muscle biopsy is the traditional and gold standard method for measuring muscle glycogen; alternatively, ¹³C magnetic resonance spectroscopy (MRS) has been developed as a reliable and non-invasive method. Furthermore, outcomes of ultrasound and bioimpedance methods have been reported to change in association with muscle glycogen conditions. The physiological mechanisms underlying this activity are assumed to involve a change in water content bound to glycogen; however, the relationship between body water and stored muscle glycogen is inconclusive. In this review, we discuss currently available muscle glycogen assessment methods, focusing on ¹³C MRS. In addition, we consider the involvement of muscle glycogen in changes in body water content and discuss the feasibility of ultrasound and bioimpedance outcomes as indicators of muscle glycogen levels. In relation to changes in body water content associated with muscle glycogen, this review broadens the discussion on changes in body weight and body components other than body water, including fat, during carbohydrate loading. From these discussions, we highlight practical issues regarding muscle glycogen assessment and manipulation in the sports field.

Dietary Intakes of Elite Male Professional Rugby Union Players in Catered and Non-Catered Environments

In professional rugby union, it is common for players to switch between catered and non-catered dietary environments throughout a season. However, little is known about the difference in dietary intake between these two settings. Twelve elite male professional rugby union players (28.3 ± 2.9 y, 188.9 ± 9.5 cm, 104.1 ± 13.3 kg) from the New Zealand Super Rugby Championship completed seven-day photographic food diaries with two-way communication during two seven-day competition weeks in both catered and non-catered environments. While no significant differences were observed in relative carbohydrate intake, mean seven-day absolute energy intakes (5210 ± 674 vs. 4341 ± 654 kcal·day^-1), relative protein (2.8 ± 0.3 vs. 2.3 ± 0.3 g·kgBM·day^-1) and relative fat (2.1 ± 0.3 vs. 1.5 ± 0.3 g·kgBM·day^-1) intakes were significantly higher in the catered compared to the non-catered environment (respectively) among forwards (n = 6). Backs (n = 6) presented non-significantly higher energy and macronutrient intakes within a catered compared to a non-catered environment. More similar dietary intakes were observed among backs regardless of the catering environment. Forwards may require more support and/or attention when transitioning between catered and non-catered environments to ensure that recommended dietary intakes are being achieved.

Fibre type- and localisation-specific muscle glycogen utilisation during repeated high-intensity intermittent exercise

Glycogen particles are situated in key areas of the muscle cell in the vicinity of the main energy-consumption sites and may be utilised heterogeneously dependent on the nature of the metabolic demands. The present study aimed to investigate the time course of fibre type-specific utilisation of muscle glycogen in three distinct subcellular fractions (intermyofibrillar, IMF; intramyofibrillar, Intra; and subsarcolemmal, SS) during repeated high-intensity intermittent exercise. Eighteen moderately to well-trained male participants performed three periods of 10 × 45 s cycling at ∼105% watt max (EX1-EX3) coupled with 5 × 6 s maximal sprints at baseline and after each period. Muscle biopsies were sampled at baseline and after EX1 and EX3. A higher glycogen breakdown rate in type 2 compared to type 1 fibres was found during EX1 for the Intra (-72 vs. -45%) and IMF (-59 vs. -35%) glycogen fractions (P < 0.001) but with no differences for SS glycogen (-52 vs. -40%). In contrast, no fibre type differences were observed during EX2-EX3, where the utilisation of Intra and IMF glycogen in type 2 fibres was reduced, resulting in depletion of all three subcellular fractions to very low levels post-exercise within both fibre types. Importantly, large heterogeneity in single-fibre glycogen utilisation was present with an early depletion of especially Intra glycogen in individual type 2 fibres. In conclusion, there is a clear fibre type- and localisation-specific glycogen utilisation during high-intensity intermittent exercise, which varies with time course of exercise and is characterised by exacerbated pool-specific glycogen depletion at the single-fibre level. KEY POINTS: Muscle glycogen is the major fuel during high-intensity exercise and is stored in distinct subcellular areas of the muscle cell in close vicinity to the main energy consumption sites. In the present study quantitative electron microscopy imaging was used to investigate the utilisation pattern of three distinct subcellular muscle glycogen fractions during repeated high-intensity intermittent exercise. It is shown that the utilisation differs dependent on fibre type, subcellular localisation and time course of exercise and with large single-fibre heterogeneity. These findings expand on our understanding of subcellular muscle glycogen metabolism during exercise and may help us explain how reductions in muscle glycogen can attenuate muscle function even at only moderately lowered whole-muscle glycogen concentrations.

Nutritional intake when cycling under racing and training conditions in professional male cyclists with type 1 diabetes

This study sought to detail and compare the in-ride nutritional practices of a group of professional cyclists with type 1 diabetes (T1D) under training and racing conditions. We observed seven male professional road cyclists with T1D (Age: 28 ± 4 years, HbA_1c: 6.4 ± 0.4% [46 ± 4 mmol.mol^-1], VO_2max: 73.9 ± 4.3 ml.kg ^-1.min^-1) during pre-season training and during a Union Cycliste Internationale multi-stage road cycling race (Tour of Slovenia). In-ride nutritional, interstitial glucose, and performance variables were quantified and compared between the two events.    The in-ride energy intake was similar between training and racing conditions     (p = 0.909), with carbohydrates being the major source of fuel in both events during exercise at a rate of 41.9 ± 6.8 g.h^-1 and 45.4 ± 15.5 g.h^-1 (p = 0.548), respectively. Protein consumption was higher during training (2.6 ± 0.6 g.h^-1) than race rides (1.9 ± 0.9 g.h^-1; p = 0.051).   A similar amount of time was spent within the euglycaemic range (≥70-≤180 mg.dL^-1): training 77.1 ± 32.8% vs racing 73.4 ± 3.9%; p = 0.818. These data provide new information on the in-ride nutritional intake in professional cyclists with T1D during different stages of the competitive season.

Athlete experiences of communication strategies in applied sports nutrition and future considerations for mobile app supportive solutions

Aim

This study aimed to explore athletes' experiences and opinions of communication strategies in applied sports nutrition, as well as capture suggestions for future mobile app supportive solutions.

Methods

A qualitative approach was used for this research. Data was generated from semi-structured focus groups (n = 9) with a purposive sample of 41 (male = 24, female = 17) full time professional athletes (mean age 24 ± 4.59) from five sports (football, rugby union, athletics, cycling, and boxing). Data was analyzed using reflexive thematic analysis.

Results

The analysis identified four higher order themes and five sub themes. Athletes appear dissatisfied with the levels of personalization in the nutrition support they receive. Limited practitioner contact time was suggested as a contributing factor to this problem. Athletes acknowledged the usefulness of online remote nutrition support and reported a desire for more personalized technology that can tailor support to their individual needs.

Conclusion

Athletes experienced a hybrid human-computer approach that combines in-person and remote digital methods to communicate with and receive information from practitioners. Mobile technology may now afford sports nutritionists with new opportunities to develop scalable solutions to support practice.

Post-translational dysregulation of glucose uptake during exhaustive cycling exercise in vastus lateralis muscle of healthy homozygous carriers of the ACE deletion allele

Homozygous carriers of the deletion allele in the gene for angiotensin-converting enzyme (ACE-DD) demonstrate an elevated risk to develop inactivity-related type II diabetes and show an overshoot of blood glucose concentration with enduring exercise compared to insertion allele carriers. We hypothesized that ACE-DD genotypes exhibit a perturbed activity of signaling processes governing capillary-dependent glucose uptake in vastus lateralis muscle during exhaustive cycling exercise, which is associated with the aerobic fitness state. 27 healthy, male white Caucasian subjects (26.8 ± 1.1 years; BMI 23.6 +/− 0.6 kg m⁻²) were characterized for their aerobic fitness based on a threshold of 50 ml O₂ min⁻¹ kg⁻¹ and the ACE-I/D genotype. Subjects completed a session of exhaustive one-legged exercise in the fasted state under concomitant measurement of cardiorespiratory function. Capillary blood and biopsies were collected before, and ½ and 8 h after exercise to quantify glucose and lipid metabolism-related compounds (lipoproteins, total cholesterol, ketones) in blood, the phosphorylation of 45 signaling proteins, muscle glycogen and capillaries. Effects of aerobic fitness, ACE-I/D genotype, and exercise were assessed with analysis of variance (ANOVA) under the hypothesis of a dominant effect of the insertion allele. Exertion with one-legged exercise manifested in a reduction of glycogen concentration ½ h after exercise (−0.046 mg glycogen mg⁻¹ protein). Blood glucose concentration rose immediately after exercise in association with the ACE-I/D genotype (ACE-DD: +26%, ACE-ID/II: +6%) and independent of the fitness state (p = 0.452). Variability in total cholesterol was associated with exercise and fitness. In fit subjects, the phosphorylation levels of glucose uptake-regulating kinases [AKT-pT308 (+156%), SRC-pY419, p38α-pT180/T182, HCK-pY411], as well as cytokine/angiotensin 1-7 signaling factors [(STAT5A-pY694, STAT5B-pY699, FYN-pY420, EGFR-pY1086] were higher in angiotensin converting enzyme I-allele carriers than ACE-DD genotypes after exercise. Conversely, the AKT-S473 phosphorylation level (+117%) and angiotensin 2’s blood concentration (+191%) were higher in ACE-DD genotypes. AKT-S473 phosphorylation levels post-exercise correlated to anatomical parameters of muscle performance and metabolic parameters (p < 0.05 and │r│>0.70). The observations identify reciprocal alterations of S473 and T308 phosphorylation of AKT as gatekeeper of a post-translational dysregulation of transcapillary glucose uptake in ACE-DD genotypes which may be targeted in personalized approaches to mitigate type II diabetes.

Patterns of energy availability of free-living athletes display day-to-day variability that is not reflected in laboratory-based protocols: Insights from elite male road cyclists

The physiological effects of low energy availability (EA) have been studied using a homogenous daily EA pattern in laboratory settings. However, whether this daily EA pattern represents those of free-living athletes and is therefore ecologically valid is unknown. To investigate this, we assessed daily exercise energy expenditure, energy intake and EA in 10 free-living elite male road cyclists (20 min Mean Maximal Power: 5.27 ± 0.25 W · kg^-1) during 7 consecutive days of late pre-season training. Energy intake was measured using the remote-food photography method and exercise energy expenditure estimated from cycling crank-based power-metres. Seven-day mean ± SD energy intake and exercise energy expenditure was 57.9 ± 10.4 and 38.4 ± 8.6 kcal · kg FFM^-1 · day^-1, respectively. EA was 19.5 ± 9.1 kcal · kg FFM^-1 · day^-1. Within-participants correlation between daily energy intake and exercise energy expenditure was .62 (95% CI: .43 - .75; P < .001), and .60 (95% CI: .41 - .74; P < .001) between carbohydrate intake and exercise energy expenditure. However, energy intake only partially compensated for exercise energy expenditure, increasing 210 kcal · day^-1 per 1000 kcal · day^-1 increase in expenditure. EA patterns displayed marked day-to-day fluctuation (range: -22 to 76 kcal · kg FFM^-1 · day^-1). The validity of research using homogenous low EA patterns therefore requires further investigation.

Gut Microbial Stability is Associated with Greater Endurance Performance in Athletes Undertaking Dietary Periodization

Dietary manipulation with high-protein or high-carbohydrate content are frequently employed during elite athletic training, aiming to enhance athletic performance. Such interventions are likely to impact upon gut microbial content. This study explored the impact of acute high-protein or high-carbohydrate diets on measured endurance performance and associated gut microbial community changes. In a cohort of well-matched, highly trained endurance runners, we measured performance outcomes, as well as gut bacterial, viral (FVP), and bacteriophage (IV) communities in a double-blind, repeated-measures design randomized control trial (RCT) to explore the impact of dietary intervention with either high-protein or high-carbohydrate content. High-dietary carbohydrate improved time-trial performance by +6.5% (P < 0.03) and was associated with expansion of Ruminococcus and Collinsella bacterial spp. Conversely, high dietary protein led to a reduction in performance by −23.3% (P = 0.001). This impact was accompanied by significantly reduced diversity (IV: P = 0.04) and altered composition (IV and FVP: P = 0.02) of the gut phageome as well as enrichment of both free and inducible Sk1virus and Leuconostoc bacterial populations. Greatest performance during dietary modification was observed in participants with less substantial shifts in community composition. Gut microbial stability during acute dietary periodization was associated with greater athletic performance in this highly trained, well-matched cohort. Athletes, and those supporting them, should be mindful of the potential consequences of dietary manipulation on gut flora and implications for performance, and periodize appropriately.

IMPORTANCE Dietary periodization is employed to improve endurance exercise performance but may impact on gut microbial communities. Bacteriophage are implicated in bacterial cell homeostasis and have been identified as biomarkers of disequilibrium in the gut ecosystem possibly brought about through dietary periodization. We find high-carbohydrate and high-protein diets to have opposing impacts on endurance performance in highly trained athlete populations. Reduced performance is linked with disturbance of microbial stasis in the gut. We demonstrate bacteriophage communities are the most sensitive component of the gut microbiota to increased gut stress following dietary manipulation. Athletes undertaking dietary periodization should be aware of potential negative impacts of drastic changes to dietary composition on gut microbial stasis and, in turn, endurance performance.

High intramuscular triglyceride turnover rates and the link to insulin sensitivity: influence of obesity, type 2 diabetes and physical activity

Large intramuscular triglyceride (IMTG) stores in sedentary, obese individuals have been linked to insulin resistance, yet well-trained athletes exhibit high IMTG levels whilst maintaining insulin sensitivity. Contrary to previous assumptions, it is now known that IMTG content per se does not result in insulin resistance. Rather, insulin resistance is caused, at least in part, by the presence of high concentrations of harmful lipid metabolites, such as diacylglycerols and ceramides in muscle. Several mechanistic differences between obese sedentary individuals and their highly trained counterparts have been identified, which determine the differential capacity for IMTG synthesis and breakdown in these populations. In this review, we first describe the most up-to-date mechanisms by which a low IMTG turnover rate (both breakdown and synthesis) leads to the accumulation of lipid metabolites and results in skeletal muscle insulin resistance. We then explore current and potential exercise and nutritional strategies that target IMTG turnover in sedentary obese individuals, to improve insulin sensitivity. Overall, improving IMTG turnover should be an important component of successful interventions that aim to prevent the development of insulin resistance in the ever-expanding sedentary, overweight and obese populations. Novelty: A description of the most up-to-date mechanisms regulating turnover of the IMTG pool. An exploration of current and potential exercise/nutritional strategies to target and enhance IMTG turnover in obese individuals. Overall, highlights the importance of improving IMTG turnover to prevent the development of insulin resistance.

A pilot sequential multiple assignment randomized trial (SMART) protocol for developing an adaptive coaching intervention around a mobile application for athletes to improve carbohydrate periodization behavior

Background

It has recently been identified that manipulating carbohydrate availability around exercise activity can enhance training-induced metabolic adaptations. Despite this approach being accepted in the athletic populations, athletes do not systematically follow the guidelines. Digital environments appear to allow nutritionists to deliver this intervention at scale, reducing expensive human coaching time. Yet, digitally delivered dietary behavior change interventions for athletes and the coaching strategy to support them are still novel concepts within sports nutrition.

Methods/design

We aim to recruit 900 athletes across the UK. 500 athletes will be recruited to test the feasibility of a novel menu planner mobile application with coaching for 6 weeks. 250 athletes with pre-existing nutritionist support will also be recruited as control. We will then conduct a 4-week pilot sequential multiple assignment randomized trial (SMART) with an additional 150 athletes. In the SMART, athletes will be given the application and additional coaching according to their engagement responses. The primary outcomes are the mobile application and coach uptake, retention, engagement, and success in attaining carbohydrate periodization behavior. Secondary outcomes are changes in goal, weight, carbohydrate periodization self-efficacy, and beliefs about consequences. Due to the high attrition nature of digital interventions, all quantitative analyses will be carried out based on both the intention-to-treat and per-protocol principles.

Discussion

This study will be the first to investigate improving carbohydrate periodization using a digital approach and tailored coaching strategies under this context. Foundational evidence from this study will provide insights into the feasibility of the digital approach.

Carbohydrate Intake Practices and Determinants of Food Choices During Training in Recreational, Amateur, and Professional Endurance Athletes: A Survey Analysis

Carbohydrate (CHO) intake during exercise can optimize endurance performance. However, there is limited information regarding fueling practices of endurance athletes during training. Accordingly, an anonymous German-language online survey was circulated examining the determinants of CHO choices, and intake practices among runners, triathletes, and cyclists during training. Survey questions included predefined answers, and a Likert scale with response of CHO food choice intakes from 1 = never to 5 = always. 1,081 endurance participants (58.0% male, 68.6% aged 18–39 years) of varying competitive levels were included in the analysis. Overall, most participants consumed a combination of commercial sport nutrition products and everyday foods (67.4%, n = 729) with their primary reason that food-first was preferred, but in some exercise scenarios, commercial sport nutrition products were deemed more convenient (61.3%, n = 447). Participants consuming commercial sport nutrition products only (19.3%, n = 209) most often valued their ease of intake during exercise (85.2%, n = 178). Among those consuming everyday foods only (13.2%, n = 143), the most common reason was the perceived importance of eating wholesome foods/natural ingredients (84.6%, n = 121). Between the most frequently consumed CHO sources during training at low-to-moderate intensities (n = 1032), sports drinks (mean ± SD; 2.56 ± 1.33) were consumed significantly more often than bananas (2.27 ± 1.14, p &lt; 0.001), with no significant difference in intake frequency between bananas and traditional muesli/fruit/energy bars (2.25 ± 1.14, p = 0.616). Whereas during high intensities (n = 1,077), sports drinks (3.31 ± 1.51) were significantly more often consumed than gels (2.79 ± 1.37), and gels significantly more often than energy bars (2.43 ± 1.28), all commercial sport nutrition products (all, p &lt; 0.001). Overall, 95.1% (n = 1028) of all participants consumed CHO during training at all exercise intensities, with males (n = 602; 2.35 ± 0.70) consuming significantly more often commercial sport nutrition products than females (n = 424; 2.14 ± 0.79, p &lt; 0.001); females consumed significantly more often everyday foods than males (1.66 ± 0.47 vs. 1.54 ± 0.42, p &lt; 0.001). Most participants used mixed CHO forms during low-to-moderate (87.9%), and high exercise intensities (94.7%). 67.6% (n = 731) of all participants reported guiding their CHO intake rates during training by gut feeling. These large-scale survey findings suggest a preference of endurance participants’ CHO intake during training in liquid form independent of exercise intensities and offer novel insights into CHO intake practices to guide sports nutrition strategies and education.

Ergo-Nutritional Intervention in Basketball: A Systematic Review

Using nutritional supplements is a widespread strategy among basketball players to ensure the appropriate provision of energy and nutrients to avoid certain complaints. Particularly in basketball, there is no consensus on the type, quantity or form of use in which these supplements should be administered. Therefore, the main aim of this systematic review is to highlight the ergo-nutritional aids that may be effective in basketball. A structured search was carried out following the Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA®) guidelines in the Medline/PubMed and Web of Science, Cochrane Library, and Scopus databases until 31 December 2021; no year restriction was applied to the search strategy. There were no filters applied to the basketball players' level, gender, race, or age to increase the power of the analysis. The results of this systematic review have shown that the effective dose of caffeine to enhance anaerobic performance and the feeling of vigorousness and energy ranges from 3 to 6 mg·kg-1, showing more positive effects when is supplemented 60-75 min before exercise in the morning and in test-based task. On the other hand, vitamin E (ranging from 200 to 268 mg), vitamin D (10,000 IU) and EPA (2 g) may have a potential role in recovery and wellness. The primary limitation of this study is the scarcity of studies related to nutritional supplementation in basketball players. However, a major strength is that this is the first systematic review describing what ergo-nutritional aids may be specifically helpful for basketball. Despite the need for future studies, certain nutritional supplements may have promising advantages for basketball (long-term supplementation of nitrates for recovery), whereas others (β-alanine, sodium bicarbonate, and acute nitrate supplementation) might theoretically be regarded as not interesting for basketball, or even not recommended by the World Anti-Doping Agency (WADA) as bovine colostrum.