Rate Of Muscle Glycogen Resynthesis Research Articles

Decreased pancreatic amylase activity after acute high-intensity exercise and its effects on post-exercise muscle glycogen recovery.

Our prior results showed that an acute bout of endurance exercise for 6h, but not 1h, decreased pancreatic amylase activity, indicating that acute endurance exercise may affect carbohydrate digestive capacity in an exercise duration-dependent manner. Here, we investigated the effects of acute endurance exercise of different intensities on mouse pancreatic amylase activity. Male C57BL/6J mice performed low- or high-intensity running exercise for 60min at either 10 (Ex-Low group) or 20m/min (Ex-High group). The control group comprised sedentary mice. Immediately after acute exercise, pancreatic amylase activity was significantly decreased in the Ex-High group and not the Ex-Low group in comparison with the control group. To determine whether the decreased amylase activity induced by high-intensity exercise influenced muscle glycogen recovery after exercise, we investigated the rates of muscle glycogen resynthesis in Ex-High group mice administered either oral glucose or starch solution (2.0mg/g body weight) immediately after exercise. The starch-fed mice exhibited significantly lower post-exercise glycogen accumulation rates in the 2-h recovery period compared with the glucose-fed mice. This difference in the glycogen accumulation rate was absent for starch- and glucose-fed mice in the sedentary (no exercise) control group. Furthermore, the plasma glucose AUC during early post-exercise recovery (0-60min) was significantly lower in the starch-fed mice than in the glucose-fed mice. Thus, our findings suggest that acute endurance exercise diminishes the carbohydrate digestive capacity of the pancreas in a manner dependent on exercise intensity, with polysaccharides leading to delayed muscle glycogen recovery after exercise.

Fenugreek and Its Effects on Muscle Performance: A Systematic Review.

Fenugreek extracts possess promising physiological and pharmacological properties in human and animal models. This review aims to provide a scientific and comprehensive analysis of the literature on the effects of fenugreek extracts on muscle performance. An extensive online search was conducted according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement guidelines. The main medical and scientific engines were searched for articles from May 1981 to May 2021 to capture all scientific studies focused on the effect of fenugreek on muscle and exercise or sport. Out of 81 studies acquired, six eligible randomized controlled trials (RCTs) were included in the qualitative analysis. Four RCTs observed that fenugreek supplementation had significantly improved muscle strength, repetitions to failure (muscle endurance), submaximal performance index, lean body mass, and reduced body fat. Among the remaining two trials, one reported the significant effect of fenugreek extracts on the rate of muscle glycogen resynthesis during post-exercise recovery; however, the other failed to do so. Those two trials were weak, with a minimal sample size (<10). Further, fenugreek glycoside supplementation with sapogenins and saponins reported substantial anabolic and androgenic activity, influencing testosterone levels and muscle performance. It was useful during eight weeks of resistance training without any clinical side effects. Fenugreek with creatine supplementation improved creatine uptake without the necessity of high carbohydrate intake. Hence, fenugreek extracts can be a helpful natural supplement and ergogenic aid for athletes. However, it is better to be aware of doping and liver and kidney damage before using the fenugreek supplement.

Does the Nutritional Composition of Dairy Milk Based Recovery Beverages Influence Post-exercise Gastrointestinal and Immune Status, and Subsequent Markers of Recovery Optimisation in Response to High Intensity Interval Exercise?

This study aimed to determine the effects of flavored dairy milk based recovery beverages of different nutrition compositions on markers of gastrointestinal and immune status, and subsequent recovery optimisation markers. After completing 2 h high intensity interval running, participants (n = 9) consumed a whole food dairy milk recovery beverage (CM, 1.2 g/kg body mass (BM) carbohydrate and 0.4 g/kg BM protein) or a dairy milk based supplement beverage (MBSB, 2.2 g/kg BM carbohydrate and 0.8 g/kg BM protein) in a randomized crossover design. Venous blood samples, body mass, body water, and breath samples were collected, and gastrointestinal symptoms (GIS) were measured, pre- and post-exercise, and during recovery. Muscle biopsies were performed at 0 and 2 h of recovery. The following morning, participants returned to the laboratory to assess performance outcomes. In the recovery period, carbohydrate malabsorption (breath H2 peak: 49 vs. 24 ppm) occurred on MBSB compared to CM, with a trend toward greater gut discomfort. No difference in gastrointestinal integrity (i.e., I-FABP and sCD14) or immune response (i.e., circulating leukocyte trafficking, bacterially-stimulated neutrophil degranulation, and systemic inflammatory profile) markers were observed between CM and MBSB. Neither trial achieved a positive rate of muscle glycogen resynthesis [−25.8 (35.5) mmol/kg dw/h]. Both trials increased phosphorylation of intramuscular signaling proteins. Greater fluid retention (total body water: 86.9 vs. 81.9%) occurred on MBSB compared to CM. Performance outcomes did not differ between trials. The greater nutrient composition of MBSB induced greater gastrointestinal functional disturbance, did not prevent the post-exercise reduction in neutrophil function, and did not support greater overall acute recovery.

Carbohydrates do not accelerate force recovery after glycogen-depleting followed by high-intensity exercise in humans.

Prolonged low-frequency force depression (PLFFD) induced by fatiguing exercise is characterized by a persistent depression in submaximal contractile force during the recovery period. Muscle glycogen depletion is known to limit physical performance during prolonged low- and moderate-intensity exercise, and accelerating glycogen resynthesis with post-exercise carbohydrate intake can facilitate recovery and improve repeated bout exercise performance. Short-term, high-intensity exercise, however, can cause PLFFD without any marked decrease in glycogen. Here, we studied whether recovery from PLFFD was accelerated by carbohydrate ingestion after 60minutes of moderate-intensity glycogen-depleting cycling exercise followed by six 30-seconds all-out cycling sprints. We used a randomized crossover study design where nine recreationally active males drank a beverage containing either carbohydrate or placebo after exercise. Blood glucose and muscle glycogen concentrations were determined at baseline, immediately post-exercise, and during the 3-hours recovery period. Transcutaneous electrical stimulation of the quadriceps muscle was performed to determine the extent of PLFFD by eliciting low-frequency (20Hz) and high-frequency (100Hz) stimulations. Muscle glycogen was severely depleted after exercise, with a significantly higher rate of muscle glycogen resynthesis during the 3-hours recovery period in the carbohydrate than in the placebo trials (13.7 and 5.4mmol glucosyl units/kg wet weight/h, respectively). Torque at 20Hz was significantly more depressed than 100Hz torque during the recovery period in both conditions, and the extent of PLFFD (20/100Hz ratio) was not different between the two trials. In conclusion, carbohydrate supplementation enhances glycogen resynthesis after glycogen-depleting exercise but does not improve force recovery when the exercise also involves all-out cycling sprints.

Systematic literature review: The effect of dairy milk on markers of recovery optimisation in response to endurance exercise

The food and fluid provided in the acute post-exercise period plays an essential role in endurance exercise recovery and adaptation. The current systematic literature review (SLR) aimed to identify and synthesize research that investigated the effect of dairy milk beverages in comparison to alternative post-exercise beverages on markers of ‘exercise recovery optimisation’, which may influence subsequent endurance exercise performance. Seventeen papers met the inclusion criteria. Quality assessment was undertaken using the Cochrane Collaboration’s tool for assessing risk of bias. Intervention beverages included fresh dairy milk (n= 3), chocolate flavoured dairy milk (n= 6), dairy milk-based sports beverages (n= 4), or a combination of the aforementioned beverages (n= 4). Results indicate dairy milk enhanced muscle protein synthesis (i.e., mixed fractional synthetic rate: 0.11%/h dairy milk vs. 0.08%/h control), and elicited similar rates of muscle glycogen resynthesis (5.9 mmol/kgWW/h) compared to a carbohydrate replacement beverage (7.6 mmol/kgWW/h). Seven studies investigated the effect of dairy milk beverages on hydration status, three of which found no differences in restoring net fluid balance after consumption of a dairy milk or dairy milk-based beverage compared to a carbohydrate-electrolyte beverage and (or) water, when consumed ad libitum. The remaining four studies observed a greater net fluid balance after consumption of a dairy milk or dairy milk-based beverage compared to an isovolumetric dose of a carbohydrate-electrolyte beverage and (or) water. To date, no study has investigated the effect of dairy milk consumption after endurance exercise on markers of immune competency or gastrointestinal status. Five studies observed enhanced time-trial or time-to-exhaustion performance (7.4% to 52.4%) with a dairy milk beverage compared to an isocaloric beverage, while another study found no differences. It is concluded that dairy milk may provide either comparable or superior recovery nutrition qualities with regards to muscle protein synthesis, glycogen replenishment, rehydration, and subsequent endurance exercise performance, when compared to non-nutritive, carbohydrate replacement, and (or) carbohydrate-electrolyte alternatives.

Daily Distribution of Macronutrient Intakes of Professional Soccer Players From the English Premier League.

The daily distribution of macronutrient intake can modulate aspects of training adaptations, performance and recovery. We therefore assessed the daily distribution of macronutrient intake (as assessed using food diaries supported by the remote food photographic method and 24-hr recalls) of professional soccer players (n = 6) of the English Premier League during a 7-day period consisting of two match days and five training days. On match days, average carbohydrate (CHO) content of the prematch (<1.5 g·kg-1 body mass) and postmatch (1 g·kg-1 body mass) meals (in recovery from an evening kick-off) were similar (p > .05) though such intakes were lower than contemporary guidelines considered optimal for prematch CHO intake and postmatch recovery. On training days, we observed a skewed and hierarchical approach (p < .05 for all comparisons) to protein feeding such that dinner (0.8 g·kg-1)>lunch (0.6 g·kg-1)>breakfast (0.3 g·kg-1)>evening snacks (0.1 g·kg-1). We conclude players may benefit from consuming greater amounts of CHO in both the prematch and postmatch meals so as to increase CHO availability and maximize rates of muscle glycogen resynthesis, respectively. Furthermore, attention should also be given to ensuring even daily distribution of protein intake so as to potentially promote components of training adaptation.

Effects of commercially available pneumatic compression on muscle glycogen recovery after exercise.

The purpose of this study was to investigate the effects of pneumatic compression pants on postexercise glycogen resynthesis. Active male subjects (n = 10) completed 2 trials consisting of a 90-minute glycogen depleting ride, followed by 4 hours of recovery with either a pneumatic compression device (PCD) or passive recovery (PR) in a random counterbalanced order. A carbohydrate beverage (1.8 g·kg bodyweight) was provided at 0 and 2 hours after exercise. Muscle biopsies (vastus lateralis) were obtained immediately and 4 hours after exercise for glycogen analyses. Blood samples were collected throughout recovery to measure glucose and insulin. Eight fingerstick blood samples for lactate were collected in the last 20 minutes of the exercise period and during the initial portion of the recovery period. Heart rate was monitored throughout the trial. During the PCD trial, subjects recovered using a commercially available recovery device (NormaTec PCD) operational at 0-60 and 120-180 minutes into recovery period. The same PCD was worn during the PR trial but was not turned on to create pulsatile pressures. There was no difference in muscle glycogen resynthesis during the recovery period (6.9 ± 0.8 and 6.9 ± 0.5 mmol·kg wet wt·h for the PR and PCD trials, respectively). Blood glucose, insulin, and lactate concentrations changed with respect to time but were not different between trials (p > 0.05). The use of PCD did not alter the rate of muscle glycogen resynthesis, blood lactate, or blood glucose and insulin concentrations associated with a postexercise oral glucose load.

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

BackgroundMuscle 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/DesignThe 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.DiscussionPhase 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 registrationISRCTN87937960.

Postexercise Cold-Water Immersion Does Not Attenuate Muscle Glycogen Resynthesis

The aim of this study was to test the hypothesis that postexercise cold-water immersion (CWI, via its associated reductions in skeletal muscle blood flow) attenuates muscle glycogen resynthesis during short-term recovery from exhaustive exercise. In a repeated-measures design, nine recreationally active men performed an exhaustive glycogen depleting cycling protocol (consisting of intermittent exercise the night before and steady-state exercise on the subsequent morning of the main trial) followed by 10 min of lower-limb CWI (8°C) or remained seated in normal ambient conditions (CONT). Subjects were fed carbohydrate (CHO) at an ingestion rate of 0.6 g·kg body mass at 30 min postexercise and at 1, 2, and 3 h postexercise. Reductions in thigh skin temperature and muscle temperature during postexercise recovery were greater in CWI compared with CONT (P < 0.01). In addition, norepinephrine and blood glucose concentrations were increased and decreased, respectively, during recovery in CWI compared with CONT (P < 0.01). Postexercise muscle glycogen (CONT and CWI postexercise = 76 ± 43 and 77 ± 26 mmol·kg dry weight [dw], respectively; mean ± SD) progressively increased (P < 0.01) during recovery, although rates of resynthesis did not differ (P = 0.719) between conditions (CONT and CWI 4 h postexercise = 160 ± 34 and 157 ± 59 mmol·kg dw, respectively). Total glycogen synthesis during recovery was comparable (CONT and CWI = 83 ± 43 and 79 ± 58 mmol·kg dw, respectively). Postexercise CWI does not attenuate muscle glycogen resynthesis rates during short-term recovery even when CHO availability is considered suboptimal. Athletes who regularly incorporate CWI as a recovery strategy to alleviate symptoms of exercise-induced muscle damage should therefore not be concerned with potential negative effects of the associated reductions in muscle blood flow on the restoration of muscle glycogen stores.

Effect of whey protein‐ and carbohydrate‐enriched diet on glycogen resynthesis during the first 48 h after a soccer game

The effect of a whey protein- and carbohydrate (CHO)-enriched diet on the rate of muscle glycogen resynthesis after a soccer match was examined. Sixteen elite soccer players were randomly assigned to a group ingesting a diet rich in carbohydrates and whey protein [CHO, protein, and fat content was 71, 21, and 8E%, respectively; high content of carbohydrates and whey protein (HCP), n = 9] or a group ingesting a normal diet (55, 18, and 26E%; control [CON], n = 7) during a 48-h recovery period after a soccer match. CON and three additional players carried out a 90- and 60-min simulated match without body contacts (SIM90 and SIM60). Muscle glycogen was lowered (P < 0.05) by 54, 48, 53, and 38% after the matches in CON, HCP, SIM90, and SIM60, respectively. Glycogen resynthesis during the first 48 h after the match was not different between CON and HCP, whereas glycogen resynthesis was slower (P < 0.05) during the first 24 h after SIM60 than SIM90 (2.88 ± 0.84 vs 4.32 ± 0.54 mmol/kg dw/h). In HCP, glycogen content in type II muscle fibers was still lowered 48 h after the match. In conclusion, glycogen resynthesis 48 h after a soccer match is not elevated by ingestion of a HCP diet. Furthermore, glycogen resynthesis does not appear to be impaired by body contacts during a match.

Should Protein Be Included in CHO-Based Sports Supplements?

Should Protein Be Included in CHO-Based Sports Supplements?

Local Muscle Temperature Alters the Rate of Post-Exercise Glycogen Resynthesis

Previous research has established that the timing and dose of ingested carbohydrates greatly influences the rate of post-exercise glycogen resynthesis. We have recently demonstrated that glycogen resynthesis is impaired in a hot ambient environment (Naperalsky et al., 2010). PURPOSE: To determine the impact of intermittent hot and cold application and the concomitant skeletal muscle temperature on rates of muscle glycogen re-synthesis after exercise. METHODS: Recreationally active male subjects (n=21) completed a 90-minute glycogen depleting ride, followed by 4 h of recovery. During recovery, two different protocols were evaluated, 1) ice was applied intermittently to one leg (IL) while the subjects other leg (CL) acted as a control (n=12) or 2) heat was applied intermittently to one leg (HL) while the subjects other leg (CL) acted as a control (n=9). Intramuscular and rectal temperature was recorded continuously. A carbohydrate (1.8 g/kg bodyweight) beverage was supplied at 0 and 2 h post exercise. Muscle biopsies (v. lateralis) were taken immediately and 4 h post exercise for the analysis of glycogen and lactate. RESULTS: The IL was colder than the CL from 15 minutes until the end recovery (p<0.05). Similarly, the HL was warmer than the CL from 15-min until the end of recovery (p<0.05). The rate of glycogen resynthesis was significantly lower in the IL compared to the CL (4.3±1.0 and 9.7±1.3 mmol/kg/hr wet wt. for the IL and CL, respectively). In contrast, the rate of glycogen resynthesis was significantly higher in the HL compared to the CL (11.7±0.8 and 8.0±1.2 mmol/kg/hr wet wt. for the HL and CL, respectively). Muscle lactate was lower in the IL after 4 h of recovery compared to the CL (1.6±0.6 vs. 2.6±0.8 mmol/L, respectively; p<0.05) but was not different between the HL and the CL (1.9±0.6 vs. 1.9±0.7 mmol/L, respectively). CONCLUSION: These data demonstrate that local muscle temperature will either reduce (intermittent ice application) or increase (intermittent heat application) rates of muscle glycogen resynthesis.

Short-Term Recovery from Prolonged Exercise

This review considers aspects of the optimal nutritional strategy for recovery from prolonged moderate to high intensity exercise. Dietary carbohydrate represents a central component of post-exercise nutrition. Therefore, carbohydrate should be ingested as early as possible in the post-exercise period and at frequent (i.e. 15- to 30-minute) intervals throughout recovery to maximize the rate of muscle glycogen resynthesis. Solid and liquid carbohydrate supplements or whole foods can achieve this aim with equal effect but should be of high glycaemic index and ingested following the feeding schedule described above at a rate of at least 1 g/kg/h in order to rapidly and sufficiently increase both blood glucose and insulin concentrations throughout recovery. Adding ≥0.3 g/kg/h of protein to a carbohydrate supplement results in a synergistic increase in insulin secretion that can, in some circumstances, accelerate muscle glycogen resynthesis. Specifically, if carbohydrate has not been ingested in quantities sufficient to maximize the rate of muscle glycogen resynthesis, the inclusion of protein may at least partially compensate for the limited availability of ingested carbohydrate. Some studies have reported improved physical performance with ingestion of carbohydrate-protein mixtures, both during exercise and during recovery prior to a subsequent exercise test. While not all of the evidence supports these ergogenic benefits, there is clearly the potential for improved performance under certain conditions, e.g. if the additional protein increases the energy content of a supplement and/or the carbohydrate fraction is ingested at below the recommended rate. The underlying mechanism for such effects may be partly due to increased muscle glycogen resynthesis during recovery, although there is varied support for other factors such as an increased central drive to exercise, a blunting of exercise-induced muscle damage, altered metabolism during exercise subsequent to recovery, or a combination of these mechanisms.

Glycaemic, insulinaemic, and immune responses to commercially available beverages consumed during recovery from rowing training

The consumption of carbohydrate and protein after exercise improves muscle glycogen synthesis and attenuates the decrease in immune function seen with endurance-type exercise. However, the impact of consuming commercially available beverages on glycaemic, insulinaemic, and immune responses during recovery from rowing training has not been investigated. Twenty-one male and female rowers completed four trials in a randomized order. Commercially available beverages were consumed in volumes providing 1.2 g carbohydrate · kg−1 body mass, upon completion of ~90 min of rowing at 60–70% maximum oxygen uptake, interspersed with up to five 5-min intervals at or above race pace. Blood samples were taken before and 15, 30, 45, 60, 90, and 120 min after consumption of the beverages for analysis of insulin and glucose and at 90 and 360 min for the analysis of cortisol and interleukin-6 (IL-6). The high-carbohydrate sports beverage and the meal replacement beverage produced a significantly larger (P<0.05) glucose incremental area under the curve than the sports-specific meal replacement beverage or the flavoured milk beverage. The high-carbohydrate sports beverage and the sports-specific meal replacement beverage produced a significantly lower (P<0.05) insulin incremental area under the curve than the meal replacement beverage or the flavoured milk beverage. The meal replacement beverage produced both a high glycaemic and insulinaemic response, suggesting that it may produce a higher rate of muscle glycogen resynthesis. There was a significant interaction between time and beverage for IL-6 (P=0.001), but not for cortisol (P=0.779). These results indicate that the impact of post-exercise nutrition on immune response may not be exclusively mediated by an attenuation of the cortisol response.

Oral acetate supplementation after prolonged moderate intensity exercise enhances early muscle glycogen resynthesis in horses

Oral acetate supplementation enhances glycogen synthesis in some mammals. However, while acetate is a significant energy source for skeletal muscle at rest in horses, its effects on glycogen resynthesis are unknown. We hypothesized that administration of an oral sodium acetate-acetic acid solution with a typical grain and hay meal after glycogen-depleting exercise would result in a rapid appearance of acetate in blood with rapid uptake by skeletal muscle. It was further hypothesized that acetate taken up by muscle would be converted to acetyl CoA (and acetylcarnitine), which would be metabolized to CO2 and water via the tricarboxylic acid cycle, generating ATP within the mitochondria and thereby allowing glucose taken up by muscle to be preferentially incorporated into glycogen. Gluteus medius biopsies and jugular venous blood were sampled from nine exercise-conditioned horses on two separate occasions, at rest and for 24 h following a competition exercise test (CET) designed to simulate the speed and endurance test of a 3 day event. After the CETs, horses were allowed water ad libitum and either 8 l of a hypertonic sodium acetate-acetic acid solution via nasogastric gavage followed by a typical hay-grain meal (acetate treatment) or a hay-grain meal alone (control treatment). The CET significantly decreased muscle glycogen concentration by 21 and 17% in the acetate and control treatments, respectively. Acetate supplementation resulted in a rapid and sustained increase in plasma [acetate]. Skeletal muscle [acetyl CoA] and [acetylcarnitine] were increased at 4 h of recovery in the acetate treatment, suggesting substantial tissue extraction of the supplemented acetate. Acetate supplementation also resulted in an enhanced rate of muscle glycogen resynthesis during the initial 4 h of the recovery period compared with the control treatment; however, by 24 h of recovery there was no difference in glycogen replenishment between trials. It is concluded that oral acetate could be an alternative energy source in the horse.

Glycogen Synthesis after Road Cycling in the Fed State

The purpose of this study was to determine the effects of a recovery beverage immediately after exercise on rates of muscle glycogen resynthesis in response to road cycling when nutritional supplementation was supplied during exercise and a solid meal was served two hours after exercise. Eight trained male cyclists, (25+/-4 years, 69.3+/-5.2 kg, VO2 peak=4.5+/-0.4 L.min(-1)) performed two 62 km outdoor training rides in a double-blind, randomized cross-over experiment. Subjects received a food bar and a commercial sport drink during each ride. A recovery beverage (40 g CHO+20 g PRO) or a placebo (PL) was administered 30 min post-exercise. At 2 h post-exercise, a solid meal was provided for both trials. There was no difference between trials at any time point for glycogen (140+/-9, 56+/-8, and 70+/-8 mmol.kg(-1)wet wt.(-1).hr.(-1) for pre, post, and 4 h post, respectively). The addition of a supplemental recovery beverage ingested soon after exercise did not significantly increase the rate of muscle glycogen resynthesis after 4 h of recovery when nutritional supplementation is provided during exercise and a meal is consumed 2 h after exercise.

Fluid and electrolyte supplementation after prolonged moderate-intensity exercise enhances muscle glycogen resynthesis in Standardbred horses

We hypothesized that postexercise rehydration using a hypotonic electrolyte solution will increase the rate of recovery of whole body hydration, and that this is associated with increased muscle glycogen and electrolyte recovery in horses. Gluteus medius biopsies and jugular venous blood were sampled from six exercise-conditioned Standardbreds on two separate occasions, at rest and for 24 h following a competitive exercise test (CET) designed to simulate the speed and endurance test of a 3-day event. After the CETs, horses were given water ad libitum, and either a hypotonic commercial electrolyte solution (electrolyte) via nasogastric tube, followed by a typical hay/grain meal, or a hay/grain meal alone (control). The CET resulted in decreased total body water and muscle glycogen concentration of 8.4 +/- 0.3 liters and 22.6%, respectively, in the control treatment, and 8.2 +/- 0.4 liters and 21.9% in the electrolyte treatment. Electrolyte resulted in an enhanced rate of muscle glycogen resynthesis and faster restoration of hydration (as evidenced by faster recovery of plasma protein concentration, maintenance of plasma osmolality, and greater muscle intracellular fluid volume) during the recovery period compared with control. There were no differences in muscle Na, K, Cl, or Mg contents between the two treatments. It is concluded that oral administration of a hypotonic electrolyte solution after prolonged moderate-intensity exercise enhanced the rate of muscle glycogen resynthesis during the recovery period compared with control. It is speculated that postexercise dehydration may be one key contributor to the slow muscle glycogen replenishment in horses.

Recovery Nutrition

Consumption of macronutrients, particularly carbohydrate (CHO) and possibly a small amount of protein, in the early recovery phase after endurance exercise can enhance muscle glycogen resynthesis rates. A target of at least 1.2 g x kg body weight(-1) x h(-1) CHO (over several hours) is suggested. This rate of CHO intake could be sustained with liquid, gel, or solid food rich in CHO for maximizing muscle glycogen. Whether the coingestion of protein with CHO compared with isocaloric CHO results in meaningful differences in glycogen replenishment that translate into subsequent performance enhancement is equivocal. Advantages of added protein with CHO in reducing true muscle damage from endurance exercise remain to be verified. There are, however, no apparent contraindications for using milk or specialty CHO/protein/amino acid products either. Future investigations that examine signaling mechanisms within muscle should be conducted in parallel with translational evidence in humans.

High rates of muscle glycogen resynthesis after exhaustive exercise when carbohydrate is coingested with caffeine

We determined the effect of coingestion of caffeine (Caff) with carbohydrate (CHO) on rates of muscle glycogen resynthesis during recovery from exhaustive exercise in seven trained subjects who completed two experimental trials in a randomized, double-blind crossover design. The evening before an experiment subjects performed intermittent exhaustive cycling and then consumed a low-CHO meal. The next morning subjects rode until volitional fatigue. On completion of this ride subjects consumed either CHO [4 g/kg body mass (BM)] or the same amount of CHO + Caff (8 mg/kg BM) during 4 h of passive recovery. Muscle biopsies and blood samples were taken at regular intervals throughout recovery. Muscle glycogen levels were similar at exhaustion [ approximately 75 mmol/kg dry wt (dw)] and increased by a similar amount ( approximately 80%) after 1 h of recovery (133 +/- 37.8 vs. 149 +/- 48 mmol/kg dw for CHO and Caff, respectively). After 4 h of recovery Caff resulted in higher glycogen accumulation (313 +/- 69 vs. 234 +/- 50 mmol/kg dw, P < 0.001). Accordingly, the overall rate of resynthesis for the 4-h recovery period was 66% higher in Caff compared with CHO (57.7 +/- 18.5 vs. 38.0 +/- 7.7 mmol x kg dw(-1) x h(-1), P < 0.05). After 1 h of recovery plasma Caff levels had increased to 31 +/- 11 microM (P < 0.001) and at the end of the recovery reached 77 +/- 11 microM (P < 0.001) with Caff. Phosphorylation of CaMK(Thr286) was similar after exercise and after 1 h of recovery, but after 4 h CaMK(Thr286) phosphorylation was higher in Caff than CHO (P < 0.05). Phosphorylation of AMP-activated protein kinase (AMPK)(Thr172) and Akt(Ser473) was similar for both treatments at all time points. We provide the first evidence that in trained subjects coingestion of large amounts of Caff (8 mg/kg BM) with CHO has an additive effect on rates of postexercise muscle glycogen accumulation compared with consumption of CHO alone.

Increased Carbohydrate Oxidation after Ingesting Carbohydrate with Added Protein

To examine the metabolic impact of including protein in a postexercise carbohydrate supplement when ingested between two bouts of prolonged running performed within the same day. Six healthy men participated in two trials separated by 14 d, each involving a 90-min treadmill run at 70% VO2max followed by 4 h of recovery and a subsequent 60-min run at the same intensity. At 30-min intervals during recovery, participants ingested either a solution containing 0.8 g.kg(-1)h(-1) of carbohydrate (CHO) or the same solution plus an additional 0.3 g.kg(-1)h(-1) of whey protein isolate (CHO-PRO). Muscle biopsies were obtained from the vastus lateralis at the beginning and end of the recovery period, with a third muscle biopsy taken following the second treadmill run. Despite higher insulinemic responses to the CHO-PRO solution than to the CHO solution (P < 0.05), rates of muscle glycogen resynthesis during recovery were not different between treatments (CHO = 12.3 +/- 2.2 and CHO-PRO = 12.1 +/- 2.7 mmol glucosyl units per kilogram of dry mass per hour). Furthermore, there were no differences between treatments in muscle glycogen degradation during subsequent exercise (CHO = 2.2 +/- 0.3 and CHO-PRO = 2.0 +/- 0.1 mmol glucosyl units per kilogram of dry mass per minute). In contrast, whole-body carbohydrate oxidation during the second run was significantly greater with the CHO-PRO treatment than with the CHO treatment (48.4 +/- 2.2 and 41.7 +/- 2.6 mg.kg(-1)min(-1), respectively; P < 0.01). These data show that the inclusion of protein in a carbohydrate-recovery supplement can increase the oxidation of extramuscular carbohydrate sources during subsequent exercise without altering the rate of muscle glycogen degradation.