Carbohydrate-protein ingestion improves subsequent running capacity towards the end of a football-specific intermittent exercise

Effects of the Timing of Carbohydrate Intake on Metabolism and Performance in Soccer Players

This study aims to provide information to improve the performance of athletes comparing the effects of carbohydrate-electrolyte intake before and during exercise on metabolism and performance in soccer players. The study had a single-blind cross-over design. Drust's protocol is a soccer-specific intermittent exercise test. The carbohydrate-electrolyte intake experiments were divided into three timings: first, pre-exercise; second, half-time; and third, mixed. Eight participants were included in the data analysis (age: 21.32 ± 1.19 years; BMI: 22.69 ± 1.91 kg/m2; height: 176.5 ± 7.52 cm; weight: 69.5 ± 9.18 kg; Vmax: 16.75 0.71 km/h). The results of the mixed test showed a significantly lower respiratory exchange ratio than those of the placebo and half-time tests (p < 0.05). The mixed test showed significantly more fat oxidation than the half-time test (p < 0.05). The running times are placebo (422.13 ± 133.44 s) and mixed (677.38 ± 217.75 s), and the distances are placebo (1577.25 ± 517.02 m) and mixed (2530.00 ± 832.71 m) (p < 0.05). The mixed test showed a significantly lower rating of perceived exertion than the placebo test (p < 0.05). Carbohydrate oxidation and heart rate showed no significant differences between the experiments (p > 0.05). The exercise protocol in this study showed the metabolic response of soccer players to intermittent high-intensity exercise and subsequent endurance exercise. In conclusion, it can be seen that the intake of carbohydrate-electrolytes improves the performance of soccer players, and the effect varies depending on the timing of carbohydrate-electrolyte intake.

Meta-Analysis of Carbohydrate Solution Intake during Prolonged Exercise in Adults: From the Last 45+ Years' Perspective

Carbohydrate (CHO) supplementation during prolonged exercise postpones fatigue. However, the optimum administration timing, dosage, type of CHO intake, and possible interaction of the ergogenic effect with athletes' cardiorespiratory fitness (CRF) are not clear. Ninety-six studies (from relevant databases based on predefined eligibility criteria) were selected for meta-analysis to investigate the acute effect of ≤20% CHO solutions on prolonged exercise performance. The between-subject standardized mean difference [SMD = ([mean post-value treatment group-mean post-value control group]/pooled variance)] was assessed. Overall, SMD [95% CI] of 0.43 [0.35, 0.51] was significant (p < 0.001). Subgroup analysis showed that SMD was reduced as the subjects' CRF level increased, with a 6-8% CHO solution composed of GL:FRU improving performance (exercise: 1-4 h); administration during the event led to a superior performance compared to administration before the exercise, with a 6-8% single-source CHO solution increasing performance in intermittent and 'stop and start' sports and an ~6% CHO solution appearing beneficial for 45-60 min exercises, but there were no significant differences between subjects' gender and age groups, varied CHO concentrations, doses, or types in the effect measurement. The evidence found was sound enough to support the hypothesis that CHO solutions, when ingested during endurance exercise, have ergogenic action and a possible crossover interaction with the subject's CRF.

Low-fat, lactose-free and leucine-enriched chocolate cow milk prototype: A preliminary study on sensorial acceptability and gastrointestinal complaints following exhaustive exercise

BACKGROUND

Chocolate milk has gained recent scientific support as a recovery drink. However, it is known that high exercise-demand triggers gastrointestinal discomfort which continues post-exercise, thereby hindering this nutritional strategy. In addition, those who are lactose intolerant cannot benefit from a milk-based beverage. Thus, the aim of this preliminary study was to develop a low-fat, lactose-free, and leucine-enriched chocolate cow milk prototype (CML) representing nutrition-related recommendations for football players, as well as assess athletes' individual subjective outcomes for gastrointestinal complaints and sensorial acceptability in a field-based setting following strenuous team-sport physical demands.

METHODS

This study followed a single group and repeated-measured design with 10 football players (23 ± 2 yrs., 74 ± 14 kg, 174 ± 5 cm) who consumed CML following a 90-min football match simulation protocol (FMP). The total CML intake to achieve 0.150 g leucine·kg [BW]·h^- 1 occurred in aliquots of 50, 30 and 20% at 0-, 45- and 75-min post-FMP, respectively. Athletes were evaluated by the prevalence, the type and severity (bloating, nausea, flatulence, and gastric reflux) of gastrointestinal complaints and sensorial acceptability (overall perception, appearance, consistency, and flavour) after drinking each aliquot in a 4-h recovery period.

RESULTS

The CML showed higher scores for "Product Acceptability Index" (88%) and sensorial acceptability (~ 8 in 9-point hedonic scale). Kendall's W with bootstrapped resample (95%CI) revealed agreement among respondents as "moderate" (overall perception, flavour) to "strong" (appearance, consistency) and with no significant agreement differences between rater response in the timeline analysis (0.57 up to 0.87; p > 0.05). Agresti-Caffo add-4 analysis (95% confidence interval, [95%CI]) revealed no differences in each time-point analysis versus baseline for athletes classified as having severe gastrointestinal symptoms, but confirmed concern with bloating (three athletes showed a transient response at 2-h and only one continued until 3-h; p = 0.051).

CONCLUSIONS

These preliminary findings suggest that CML presents good taste and high acceptability by the sampled athletes. Thus, CML may be an alternative sport drink for immediate post-workout supplementation to overcome the energy deficit, offer co-ingested leucine, maintain palatability and adherence including lactose intolerance following a team sport-specific fatigue.

TRIAL REGISTRATION

RBR-2vmpz9 , 10/12/2019, retrospectively registered.

Carbohydrate supplementation: a critical review of recent innovations

PURPOSE

To critically examine the research on novel supplements and strategies designed to enhance carbohydrate delivery and/or availability.

METHODS

Narrative review.

RESULTS

Available data would suggest that there are varying levels of effectiveness based on the supplement/supplementation strategy in question and mechanism of action. Novel carbohydrate supplements including multiple transportable carbohydrate (MTC), modified carbohydrate (MC), and hydrogels (HGEL) have been generally effective at modifying gastric emptying and/or intestinal absorption. Moreover, these effects often correlate with altered fuel utilization patterns and/or glycogen storage. Nevertheless, performance effects differ widely based on supplement and study design. MTC consistently enhances performance, but the magnitude of the effect is yet to be fully elucidated. MC and HGEL seem unlikely to be beneficial when compared to supplementation strategies that align with current sport nutrition recommendations. Combining carbohydrate with other ergogenic substances may, in some cases, result in additive or synergistic effects on metabolism and/or performance; however, data are often lacking and results vary based on the quantity, timing, and inter-individual responses to different treatments. Altering dietary carbohydrate intake likely influences absorption, oxidation, and and/or storage of acutely ingested carbohydrate, but how this affects the ergogenicity of carbohydrate is still mostly unknown.

CONCLUSIONS

In conclusion, novel carbohydrate supplements and strategies alter carbohydrate delivery through various mechanisms. However, more research is needed to determine if/when interventions are ergogenic based on different contexts, populations, and applications.

Acute and Residual Soccer Match-Related Fatigue: A Systematic Review and Meta-analysis

BACKGROUND

Understanding soccer players' match-related fatigue and recovery profiles likely helps with developing conditioning programs that increase team performance and reduce injuries and illnesses. In order to improve match recovery (the return-to-play process and ergogenic interventions) it is also pivotal to determine if match simulation protocols and actual match-play lead to similar responses.

OBJECTIVES

(1) To thoroughly describe the development of fatigue during actual soccer match play and its recovery time course in terms of physiological, neuromuscular, technical, biochemical and perceptual responses, and (2) to determine similarities of recovery responses between actual competition (11 vs. 11) and match simulations.

METHODS

A first screening phase consisted of a systematic search on PubMed (MEDLINE) and SportDiscus databases until March 2016. Inclusion criteria were: longitudinal study with soccer players; match or validated protocol; duration > 45 min; and published in English.

RESULTS

A total of 77 eligible studies (n = 1105) were used to compute 1196 effect sizes (ES). Half-time assessments revealed small to large alterations in immunological parameters (e.g. leukocytes, ES = 1.9), a moderate decrement in insulin concentration (ES = - 0.9) and a small to moderate impairment in lower-limb muscle function (ES = - 0.5 to - 0.7) and physical performance measures (e.g. linear sprint, ES = - 0.3 to - 1.0). All the systematically analyzed fatigue-related markers were substantially altered at post-match. Hamstrings force production capacity (ES = - 0.7), physical performance (2-4%, ES = 0.3-0.5), creatine kinase (CK, ES = 0.4), well-being (ES = 0.2-0.4) and delayed onset muscle soreness (DOMS, ES = 0.6-1.3) remained substantially impaired at G + 72 h. Compared to simulation protocols, 11 vs. 11 match format (CK, ES = 1.8) induced a greater magnitude of change in muscle damage (i.e. CK, ES = 1.8 vs. 0.7), inflammatory (IL-6, ES = 2.6 vs. 1.1) and immunological markers and DOMS (ES = 1.5 vs. 0.7) than simulation protocols at post-assessments. Neuromuscular performances at post-match did not differ between protocols.

CONCLUSION

While some parameters are fully recovered (e.g. hormonal and technical), our systematic review shows that a period of 72 h post-match play is not long enough to completely restore homeostatic balance (e.g. muscle damage, physical and well-being status). The extent of the recovery period post-soccer game cannot consist of a 'one size fits all approach'. Additionally, the 'real match' (11 vs. 11 format) likely induces greater magnitudes of perceptual (DOMS) and biochemical alterations (e.g. muscle damage), while neuromuscular alterations were essentially similar. Overall, coaches must adjust the structure and content of the training sessions during the 72-h post-match intervention to effectively manage the training load within this time-frame.

Post-exercise Ingestion of Carbohydrate, Protein and Water: A Systematic Review and Meta-analysis for Effects on Subsequent Athletic Performance

BACKGROUND

Athletes may complete consecutive exercise sessions with limited recovery time between bouts (e.g. ≤ 4 h). Nutritional strategies that optimise post-exercise recovery in these situations are therefore important.

OBJECTIVE

This two-part review investigated the effect of consuming carbohydrate (CHO) and protein with water (W) following exercise on subsequent athletic (endurance/anaerobic exercise) performance.

DATA SOURCES

Studies were identified by searching the online databases SPORTDiscus, PubMed, Web of Science and Scopus.

STUDY ELIGIBILITY CRITERIA AND INTERVENTIONS

Investigations that measured endurance performance (≥ 5 min duration) ≤ 4 h after a standardised exercise bout (any type) under the following control vs. intervention conditions were included: Part 1: W vs. CHO ingested with an equal volume of W (CHO + W); and, Part 2: CHO + W vs. protein (PRO) ingested with CHO and an equal volume of W (PRO + CHO + W), where CHO or energy intake was matched.

STUDY APPRAISAL AND SYNTHESIS METHODS

Publications were examined for bias using the Rosendal scale. Random-effects meta-analyses and meta-regression analyses were conducted to evaluate intervention efficacy.

RESULTS

The quality assessment yielded a Rosendal score of 63 ± 9% (mean ± standard deviation). Part 1: 45 trials (n = 486) were reviewed. Ingesting CHO + W (102 ± 50 g CHO; 0.8 ± 0.6 g CHO kg^-1 h^-1) improved exercise performance compared with W (1.6 ± 0.7 L); %_Δ mean power output = 4.0, 95% confidence interval 3.2-4.7 (I ² = 43.9). Improvement was attenuated when participants were 'Fed' (a meal 2-4 h prior to the initial bout) as opposed to 'Fasted' (p = 0.012). Part 2: 13 trials (n = 125) were reviewed. Ingesting PRO + CHO + W (35 ± 26 g PRO; 0.5 ± 0.4 g PRO kg^-1) did not affect exercise performance compared with CHO + W (115 ± 61 g CHO; 0.6 ± 0.3 g CHO·kg body mass^-1 h^-1; 1.2 ± 0.6 L); %_Δ mean power output = 0.5, 95% confidence interval - 0.5 to 1.6 (I ² = 72.9).

CONCLUSIONS

Athletes with limited time for recovery between consecutive exercise sessions should prioritise CHO and fluid ingestion to enhance subsequent athletic performance. PROSPERO REGISTRATION NUMBER: CRD42016046807.

Restoration of Muscle Glycogen and Functional Capacity: Role of Post-Exercise Carbohydrate and Protein Co-Ingestion

The importance of post-exercise recovery nutrition has been well described in recent years, leading to its incorporation as an integral part of training regimes in both athletes and active individuals. Muscle glycogen depletion during an initial prolonged exercise bout is a main factor in the onset of fatigue and so the replenishment of glycogen stores may be important for recovery of functional capacity. Nevertheless, nutritional considerations for optimal short-term (3–6 h) recovery remain incompletely elucidated, particularly surrounding the precise amount of specific types of nutrients required. Current nutritional guidelines to maximise muscle glycogen availability within limited recovery are provided under the assumption that similar fatigue mechanisms (i.e., muscle glycogen depletion) are involved during a repeated exercise bout. Indeed, recent data support the notion that muscle glycogen availability is a determinant of subsequent endurance capacity following limited recovery. Thus, carbohydrate ingestion can be utilised to influence the restoration of endurance capacity following exhaustive exercise. One strategy with the potential to accelerate muscle glycogen resynthesis and/or functional capacity beyond merely ingesting adequate carbohydrate is the co-ingestion of added protein. While numerous studies have been instigated, a consensus that is related to the influence of carbohydrate-protein ingestion in maximising muscle glycogen during short-term recovery and repeated exercise capacity has not been established. When considered collectively, carbohydrate intake during limited recovery appears to primarily determine muscle glycogen resynthesis and repeated exercise capacity. Thus, when the goal is to optimise repeated exercise capacity following short-term recovery, ingesting carbohydrate at an amount of ≥1.2 g kg body mass⁻¹·h⁻¹ can maximise muscle glycogen repletion. The addition of protein to carbohydrate during post-exercise recovery may be beneficial under circumstances when carbohydrate ingestion is sub-optimal (≤0.8 g kg body mass⁻¹·h⁻¹) for effective restoration of muscle glycogen and repeated exercise capacity.

Nutrition and Supplementation in Soccer

Contemporary elite soccer features increased physical demands during match-play, as well as a larger number of matches per season. Now more than ever, aspects related to performance optimization are highly regarded by both players and soccer coaches. Here, nutrition takes a special role as most elite teams try to provide an adequate diet to guarantee maximum performance while ensuring a faster recovery from matches and training exertions. It is currently known that manipulation and periodization of macronutrients, as well as sound hydration practices, have the potential to interfere with training adaptation and recovery. A careful monitoring of micronutrient status is also relevant to prevent undue fatigue and immune impairment secondary to a deficiency status. Furthermore, the sensible use of evidence-based dietary supplements may also play a role in soccer performance optimization. In this sense, several nutritional recommendations have been issued. This detailed and comprehensive review addresses the most relevant and up-to-date nutritional recommendations for elite soccer players, covering from macro and micronutrients to hydration and selected supplements in different contexts (daily requirements, pre, peri and post training/match and competition).

Combined Carbohydrate and Protein Ingestion During Australian Rules Football Matches and Training Sessions Does Not Reduce Fatigue or Accelerate Recovery Throughout a Weeklong Junior Tournament

Lee, NA, Fell, JW, Pitchford, NW, Hall, AH, Leveritt, MD, and Kitic, CM. Combined carbohydrate and protein ingestion during Australian rules football matches and training sessions does not reduce fatigue or accelerate recovery throughout a weeklong junior tournament. J Strength Cond Res 32(2): 344-355, 2018-Australian rules football (ARF) is a physically demanding sport that can induce high levels of fatigue. Fatigue may be intensified during periods where multiple matches are played with limited recovery time. Combined carbohydrate and protein (CHO + PRO) intake during physical activity may provide performance and recovery benefits. The aim of this study was to investigate whether CHO + PRO ingestion during ARF matches and training sessions throughout a tournament would enhance performance or recovery in comparison with CHO-only ingestion. Australian rules football players (n = 21) competing in a 7-day national tournament participated in this randomized and double-blinded study. Beverages containing either CHO (n = 10) or CHO + PRO (n = 11) were provided during matches (day 1, day 4, and day 7) and training sessions (day 2 and day 3). Countermovement jumps (CMJs), ratings of muscle soreness, and autonomic function were assessed throughout the tournament. Gastrointestinal tract (GI) discomfort was measured after matches. Countermovement jump peak velocity increased in the CHO + PRO group (p = 0.01) but not in the CHO group. There were no differences in the other CMJ variables. In both groups, muscle soreness increased from days 0 and 1 to day 2 (p ≤ 0.05) but did not remain elevated. R-R intervals (time elapsed between successive peaks in QRS complexes) increased in both groups from day 1 to day 7 (mean difference = 59.85 ms, p < 0.01). Postmatch GI discomfort was not different (p > 0.05) between groups. When daily dietary protein is adequate (>1.8 g·kg·d), the ingestion of CHO + PRO during matches and training sessions throughout a tournament does not reduce muscle soreness nor have clear benefits for neuromuscular recovery or modulate autonomic function in junior ARF athletes, compared with that of CHO alone.

Nighttime feeding likely alters morning metabolism but not exercise performance in female athletes

The timing of morning endurance competition may limit proper pre-race fueling and resulting performance. A nighttime, pre-sleep nutritional strategy could be an alternative method to target the metabolic and hydrating needs of the early morning athlete without compromising sleep or gastrointestinal comfort during exercise. Therefore, the purpose of this investigation was to examine the acute effects of pre-sleep chocolate milk (CM) ingestion on next-morning running performance, metabolism, and hydration status. Twelve competitive female runners and triathletes (age, 30 ± 7 years; peak oxygen consumption, 53 ± 4 mL·kg(-1)·min(-1)) randomly ingested either pre-sleep CM or non-nutritive placebo (PL) ∼30 min before sleep and 7-9 h before a morning exercise trial. Resting metabolic rate (RMR) was assessed prior to exercise. The exercise trial included a warm-up, three 5-min incremental workloads at 55%, 65%, and 75% peak oxygen consumption, and a 10-km treadmill time trial (TT). Physiological responses were assessed prior, during (incremental and TT), and postexercise. Paired t tests and magnitude-based inferences were used to determine treatment differences. TT performances were not different ("most likely trivial" improvement with CM) between conditions (PL: 52.8 ± 8.4 min vs CM: 52.8 ± 8.0 min). RMR was "likely" increased (4.8%) and total carbohydrate oxidation (g·min(-1)) during exercise was "possibly" or likely increased (18.8%, 10.1%, 9.1% for stage 1-3, respectively) with CM versus PL. There were no consistent changes to hydration indices. In conclusion, pre-sleep CM may alter next-morning resting and exercise metabolism to favor carbohydrate oxidation, but effects did not translate to 10-km running performance improvements.

Carbohydrate supplementation attenuates decrement in performance in overtrained rats

Carbohydrate ingestion at the end of a single exercise is recognized as delaying fatigue and accelerating recovery, but whether chronic ingestion can prevent overtraining during periods of intense training has not yet been elucidated. This study aimed to determine whether carbohydrate supplementation minimizes overtraining in Wistar rats. The animals underwent 11 weeks of training (running) on a treadmill, and the last 3 weeks were designed to induce overtraining. One group was supplemented with carbohydrates (EX-CHO) (n = 13), 1 group had no supplementation (EX) (n = 10), and a third group remained inactive (C) (n = 9). Performance tests were given before training (Pr1) and at the 8th (Pr2) and 11th (Pr3) training week. Food intake, body weight, testosterone, cortisol, malondialdehyde, creatine kinase, and activities of the PI3-K, Akt-1, mTOR, and GSK-3 enzymes were measured. In the EX group, there was a significant 32.6% performance decrease at Pr3 when compared with Pr2. In addition, at protocol completion, the EX-CHO group had a greater gastrocnemius weight than did the C group (p = 0.02), which the EX group did not. Training caused anorexia, decreased testosterone (p = 0.001), and increased malondialdehyde (p = 0.009) in both exercise groups compared with the C group, with no influence of carbohydrate supplementation on these variables (p > 0.05). Compared with in the C group, the activity of Akt-1 was higher in the EX-CHO group but not in the EX group (p = 0.013). Carbohydrate supplementation promoted an attenuation in the performance decrement and maintained gastrocnemius muscle mass in animals that had undergone overtraining protocols, which was accompanied by increased activity of the Akt-1 molecular indicator.

Acute Effects of Carbohydrate Supplementation on Intermittent Sports Performance

Intermittent sports (e.g., team sports) are diverse in their rules and regulations but similar in the pattern of play; that is, intermittent high-intensity movements and the execution of sport-specific skills over a prolonged period of time (~1–2 h). Performance during intermittent sports is dependent upon a combination of anaerobic and aerobic energy systems, both of which rely on muscle glycogen and/or blood glucose as an important substrate for energy production. The aims of this paper are to review: (1) potential biological mechanisms by which carbohydrate may impact intermittent sport performance; (2) the acute effects of carbohydrate ingestion on intermittent sport performance, including intermittent high-intensity exercise capacity, sprinting, jumping, skill, change of direction speed, and cognition; and (3) what recommendations can be derived for carbohydrate intake before/during exercise in intermittent sports based on the available evidence. The most researched intermittent sport is soccer but some sport-specific studies have also been conducted in other sports (e.g., rugby, field hockey, basketball, American football, and racquet sports). Carbohydrate ingestion before/during exercise has been shown in most studies to enhance intermittent high-intensity exercise capacity. However, studies have shown mixed results with regards to the acute effects of carbohydrate intake on sprinting, jumping, skill, change of direction speed, and cognition. In most of these studies the amount of carbohydrate consumed was ~30–60 g/h in the form of a 6%–7% carbohydrate solution comprised of sucrose, glucose, and/or maltodextrin. The magnitude of the impact that carbohydrate ingestion has on intermittent sport performance is likely dependent on the carbohydrate status of the individual; that is, carbohydrate ingestion has the greatest impact on performance under circumstances eliciting fatigue and/or hypoglycemia. Accordingly, carbohydrate ingestion before and during a game seems to have the greatest impact on intermittent sports performance towards the end of the game.

A multi-ingredient containing carbohydrate, proteins L-glutamine and L-carnitine attenuates fatigue perception with no effect on performance, muscle damage or immunity in soccer players

We investigated the effects of ingesting a multi-ingredient (53 g carbohydrate, 14.5 g whey protein, 5 g glutamine, 1.5 g L-carnitine-L-tartrate) supplement, carbohydrate only, or placebo on intermittent performance, perception of fatigue, immunity, and functional and metabolic markers of recovery. Sixteen amateur soccer players ingested their respective treatments before, during and after performing a 90-min intermittent repeated sprint test. Primary outcomes included time for a 90-min intermittent repeated sprint test (IRS) followed by eleven 15 m sprints. Measurements included creatine kinase, myoglobin, interleukine-6, Neutrophil; Lymphocytes and Monocyte before (pre), immediately after (post), 1 h and 24 h after exercise testing period. Overall, time for the IRS and 15 m sprints was not different between treatments. However, the perception of fatigue was attenuated (P<0.001) for the multi-ingredient (15.9±1.4) vs. placebo (17.8±1.4) but not for the carbohydrate (17.0±1.9) condition. Several changes in immune/inflammatory indices were noted as creatine kinase peaked at 24 h while Interleukin-6 and myoglobin increased both immediately after and at 1 h compared with baseline (P<0.05) for all three conditions. However, Myoglobin (P<0.05) was lower 1 h post-exercise for the multi-ingredient (241.8±142.6 ng·ml(-1)) and CHO (265.4±187.8 ng·ml(-1)) vs. placebo (518.6±255.2 ng·ml(-1)). Carbohydrate also elicited lower neutrophil concentrations vs. multi-ingredient (3.9±1.5 10(9)/L vs. 4.9±1.8 10(9)/L, P = 0.016) and a reduced (P<0.05) monocytes count (0.36±0.09 10(9)/L) compared to both multi-ingredient (0.42±0.09 10(9)/L) and placebo (0.42±0.12 10(9)/L). In conclusion, multi-ingredient and carbohydrate supplements did not improve intermittent performance, inflammatory or immune function. However, both treatments did attenuate serum myoglobin, while only carbohydrate blunted post-exercise leukocytosis.

Effect of a carbohydrate-protein multi-ingredient supplement on intermittent sprint performance and muscle damage in recreational athletes

Carbohydrate-protein-based multi-ingredient supplements have been proposed as an effective strategy for limiting the deleterious effects of exercise-induced muscle damage. This study compares the effects of a commercially available carbohydrate-protein supplement enriched with l-glutamine and l-carnitine-l-tartrate to carbohydrate alone or placebo on sprint performance, muscle damage markers, and recovery from intermittent exercise. On 3 occasions, 10 recreationally trained males ingested a multi-ingredient, a carbohydrate supplement, or a placebo before, during, and immediately after a 90-min intermittent repeated sprint test. Fifteen-metre sprint times, creatine kinase, myoglobin, and interleukin-6 were assessed before (pre), immediately after (post), 1 h after (1h), and 24 h after (24h) exercise. Total sprint time measured during the intermittent protocol was not different between conditions. Fifteen-metre sprint time was slower (p < 0.05) at post, 1h and 24h compared with pre without differences between conditions (p > 0.05). Creatine kinase at 24h was lower (p < 0.05) in the multi-ingredient (461.8 ± 271.8 U·L) compared with both carbohydrate and placebo (606 ± 314.5 U·L and 636 ± 344.6 U·L, respectively). Myoglobin increased (p < 0.05) in all 3 conditions at post and 1h compared with pre, showing lower values at 1h (p < 0.05) for the carbohydrate and a trend (p = 0.060) for multi-ingredient compared with the placebo condition (211.4 ± 127.2 ng·mL(-1) and 239.4 ± 103.8 ng·mL(-1) vs. 484.6 ± 200.0 ng·mL(-1), respectively). Interleukin-6 increased at both post and 1h compared with pre (p < 0.05) with no differences between conditions. In conclusion, ingesting a multi-ingredient supplement before, during, and immediately after a 90-min intermittent sprint test resulted in no effects on performance and fatigue while the accumulation of some biomarkers of muscle damage could be attenuated.

Exploring mechanisms of fatigue during repeated exercise and the dose dependent effects of carbohydrate and protein ingestion: study protocol for a randomised controlled trial

Background

Muscle glycogen has been well established as the primary metabolic energy substrate during physical exercise of moderate- to high-intensity and has accordingly been implicated as a limiting factor when such activity is sustained for a prolonged duration. However, the role of this substrate during repeated exercise after limited recovery is less clear, with ongoing debate regarding how recovery processes can best be supported via nutritional intervention. The aim of this project is to examine the causes of fatigue during repeated exercise bouts via manipulation of glycogen availability through nutritional intervention, thus simultaneously informing aspects of the optimal feeding strategy for recovery from prolonged exercise.

Methods/Design

The project involves two phases with each involving two treatment arms administered in a repeated measures design. For each treatment, participants will be required to exercise to the point of volitional exhaustion on a motorised treadmill at 70% of previously determined maximal oxygen uptake, before a four hour recovery period in which participants will be prescribed solutions providing 1.2 grams of sucrose per kilogram of body mass per hour of recovery (g.kg^-1.h^-1) relative to either a lower rate of sucrose ingestion (that is, 0.3 g.kg^-1. h^-1; Phase I) or a moderate dose (that is, 0.8 g.kg^-1.h^-1) rendered isocaloric via the addition of 0.4 g.kg^-1.h^-1 whey protein hydrolysate (Phase II); the latter administered in a double blind manner as part of a randomised and counterbalanced design. Muscle biopsies will be sampled at the beginning and end of recovery for determination of muscle glycogen resynthesis rates, with further biopsies taken following a second bout of exhaustive exercise to determine differences in substrate availability relative to the initial sample taken following the first exercise bout.

Discussion

Phase I will inform whether a dose–response relationship exists between carbohydrate ingestion rate and muscle glycogen availability and/or the subsequent capacity for physical exercise. Phase II will determine whether such effects are dependent on glycogen availability per se or energy intake, potentially via protein mediated mechanisms.

Trial registration

ISRCTN87937960.

Metabolic limitations of performance and fatigue in football

Football participation requires considerable utilization of both aerobic and anaerobic energy systems to match the high energetic demands of the sport. The consequent stresses imposed on the physiological and metabolic systems carries players to the threshold of exhaustion during match-play, from which they are required to recover in preparation for the subsequent game. A high number of players experience fatigue during the high-intensity bouts and a consequent decline in their performance towards the end of the game is a likely outcome during match-play. The current review aims to establish the current understanding that relates to metabolic limitations of performance and the associated mechanisms for the onset of fatigue that may be instrumental in further development of evidence-based nutritional and training interventions in this event.