Post-exercise Carbohydrate Research Articles

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

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. 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. 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. 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.

Post-Exercise Carbohydrate Intake in the Early Postoperative Phase Following Primary Total Hip and Knee Arthroplasties – A Randomized Controlled Trial

The aim of this study was to investigate whether post exercise carbohydrate intake improves training effect in the first postoperative days, in patients who have had a primary total knee or hip arthroplasty. Subjects were primary total hip (THA) (n=18), and total knee arthroplasties (TKA)(n=25) patients randomized to consume 30 g maltodextrin or placebo within 15 minutes after each training session as a supplement to the standard diet. The outcome measures were six minute walk test (6-MWT), number of completed training sessions, training intensity, and duration. There was no difference in the 6-MWT, number of completed training sessions, training intensity and duration between the intervention vs control group. When stratified for operation procedure, THA patients in the intervention group trained longer (26.7 ± 5.8 vs 15.2 ± 4.1 min, P = 0.017), and at an overall higher intensity (scale 1-5) (2.4 ± 1.0 vs 1.75 ± 0.8, P = 0.021) and during the training sessions with the physiotherapist (2.5 ± 1.1 vs and 1.8 ± 0.9, P = 0.044) compared with controls. In contrary, the duration of self-training was longer in the TKA control group compared with the intervention group (19.7 ± 7.0 vs 13.8 ± 3.3 min, P = 0.021). In conclusion, minor positive effects of maltodextrin were observed after hip arthroplasties, while minor negative effects of maltodextrin were observed after knee arthroplasties. It is unknown whether these findings are due to the low dose of maltodextrin, small number of study participants, differences in overall nutritional status, or lack of effect.

Carbohydrate-Energy Replacement Following High-Intensity Interval Exercise Blunts Next-Day Glycemic Control in Untrained Women.

BackgroundImproved glycemic control has been reported for ∼24 h following low-volume high-intensity interval exercise (HIIE), but it is unclear if this is a direct effect of exercise or an indirect effect of the exercise-induced energy deficit. The purpose of this study was to investigate the effect of carbohydrate-energy replacement after low-volume HIIE on 24 h glycemic control in women.MethodsSeven untrained women (age: 22 ± 2 yr; BMI: 22 ± 3 kg/m2; VO2peak: 33 ± 7 ml/kg/min) completed three 2-day trials in the mid-follicular phase of the menstrual cycle. Continuous glucose monitoring was used to measure blood glucose concentrations during, and for 24 h following three conditions: (1) HIIE followed by a high-carbohydrate energy replacement drink (EX-HC); (2) HIIE followed by a non-caloric taste-matched placebo drink (EX-NC); and (3) seated control with no drink (CTL). HIIE involved an evening session (1,700 h) of 10 × 1-min cycling efforts at ∼90% maximal heart rate with 1 min recovery. Diet was standardized and identical across all three 2-day trials, apart from the post-exercise carbohydrate drink in EX-HC, which was designed to replenish the exercise-induced energy expenditure. Postprandial glycemic responses to the following days breakfast, snack, lunch, and dinner, as well as 24 h indices of glycemic control, were analyzed.ResultsThe day after HIIE, postprandial glycemia following breakfast and snack were reduced in EX-NC compared to EX-HC, as reflected by lower 3 h glucose mean (breakfast: 5.5 ± 0.5 vs. 6.7 ± 1, p = 0.01, Cohen’s d = 1.4; snack: 4.9 ± 0.3 vs. 5.7 ± 0.8 mmol/L, p = 0.02, d = 1.4) and/or area under the curve (AUC) (breakfast: 994 ± 86 vs. 1,208 ± 190 mmol/L x 3 h, p = 0.01, d = 1.5). Postprandial glycemic responses following lunch and dinner were not different across conditions (p > 0.05). The 24 h glucose mean (EX-NC: 5.2 ± 0.3 vs. EX-HC: 5.7 ± 0.7 mmol/L; p = 0.02, d = 1.1) and AUC (EX-NC: 7,448 ± 425 vs. EX-HC: 8,246 ± 957 mmol/L × 24 h; p = 0.02, d = 1.1) were reduced in EX-NC compared to EX-HC.ConclusionPost-exercise carbohydrate-energy replacement attenuates glycemic control the day following a single session of low-volume HIIE in women.

Carbohydrate and Protein Co-Ingestion Postexercise Does Not Improve Next-Day Performance in Trained Cyclists.

Supplementing postexercise carbohydrate (CHO) intake with protein has been suggested to enhance recovery from endurance exercise. The aim of this study was to investigate whether adding protein to the recovery drink can improve 24-hr recovery when CHO intake is suboptimal. In a double-blind crossover design, 12 trained men performed three 2-day trials consisting of constant-load exercise to reduce glycogen on Day 1, followed by ingestion of a CHO drink (1.2 g·kg-1·2 hr-1) either without or with added whey protein concentrate (CHO + PRO) or whey protein hydrolysate (CHO + PROH) (0.3 g·kg-1·2 hr-1). Arterialized blood glucose and insulin responses were analyzed for 2hr postingestion. Time-trial performance was measured the next day after another bout of glycogen-reducing exercise. The 30-min time-trial performance did not differ between the three trials (M ± SD, 401 ± 75, 411 ± 80, 404 ± 58kJ in CHO, CHO + PRO, and CHO + PROH, respectively, p = .83). No significant differences were found in glucose disposal (area under the curve [AUC]) between the postexercise conditions (364 ± 107, 341 ± 76, and 330 ± 147, mmol·L-1·2 hr-1, respectively). Insulin AUC was lower in CHO (18.1 ± 7.7 nmol·L-1·2 hr-1) compared with CHO + PRO and CHO + PROH (24.6 ± 12.4 vs. 24.5 ± 10.6, p = .036 and .015). No difference in insulin AUC was found between CHO + PRO and CHO + PROH. Despite a higher acute insulin response, adding protein to a CHO-based recovery drink after a prolonged, high-intensity exercise bout did not change next-day exercise capacity when overall 24-hr macronutrient and caloric intake was controlled.

Interactive effects of acute exercise and carbohydrate-energy replacement on insulin sensitivity in healthy adults.

This study investigated whether carbohydrate-energy replacement immediately after prolonged endurance exercise attenuates insulin sensitivity the following morning, and whether exercise improves insulin sensitivity the following morning independent of an exercise-induced carbohydrate deficit. Oral glucose tolerance and whole-body insulin sensitivity were compared the morning after 3 evening conditions, involving (1) treadmill exercise followed by a carbohydrate replacement drink (200 or 150g maltodextrin for males and females, respectively; CHO-replace); (2) treadmill exercise followed by a non-caloric, taste-matched placebo (CHO-deficit); or (3) seated rest with no drink provided (Rest). Treadmill exercise involved 90minutes at ∼80% age-predicted maximum heart rate. Seven males and 2 females (aged 23± 1years; body mass index 24.0± 2.7kg·m-2) completed all conditions in a randomised order. Matsuda index improved by 22% (2.2 [0.3, 4.0] au, p= 0.03) and HOMA2-IR improved by 10% (-0.04 [-0.08, 0.00] au, p= 0.04) in CHO-deficit versus CHO-replace, without corresponding changes in postprandial glycaemia. Outcomes were similar between Rest and other conditions. These data suggest that improvements to insulin sensitivity in healthy populations following acute moderate/vigorous intensity endurance exercise may be dependent on the presence of a carbohydrate-energy deficit. Novelty: Restoration of carbohydrate balance following acute endurance exercise attenuated whole-body insulin sensitivity. Exercise per se failed to enhance whole-body insulin sensitivity. Maximising or prolonging the post-exercise carbohydrate deficit may enhance acute benefits to insulin sensitivity.

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.

Caloric restriction induces anabolic resistance to resistance exercise

PurposeWeight loss can result in the loss of muscle mass and bone mineral density. Resistance exercise is commonly prescribed to attenuate these effects. However, the anabolic endocrine response to resistance exercise during caloric restriction has not been characterized.MethodsParticipants underwent 3-day conditions of caloric restriction (15 kcal kg FFM−1) with post-exercise carbohydrate (CRC) and with post-exercise protein (CRP), and an energy balance control (40 kcal kg FFM−1) with post-exercise carbohydrate (CON). Serial blood draws were taken following five sets of five repetitions of the barbell back squat exercise on day 3 of each condition.ResultsIn CRC and CRP, respectively, growth hormone peaked at 2.6 ± 0.4 and 2.5 ± 0.9 times the peak concentrations observed during CON. Despite this, insulin-like growth factor-1 concentrations declined 18.3 ± 3.4% in CRC and 27.2 ± 3.8% in CRP, which was greater than the 7.6 ± 3.6% decline in CON, over the subsequent 24 h. Sclerostin increased over the first 2 days of each intervention by 19.2 ± 5.6% in CRC, 21.8 ± 6.2% in CRP and 13.4 ± 5.9% in CON, but following the resistance exercise bout, these increases were attenuated and no longer significant.ConclusionDuring caloric restriction, there is considerable endocrine anabolic resistance to a single bout of resistance exercise which persists in the presence of post-exercise whey protein supplementation. Alternative strategies to restore the sensitivity of insulin-like growth factor-1 to growth hormone need to be explored.

Males and females exhibit similar muscle glycogen recovery with varied recovery food sources

PurposeResearch has elucidated the impact of post-exercise carbohydrate nutrition and environmental conditions on muscle glycogen re-synthesis. However, research has minimally considered the implications of glycogen recovery in females and has mostly focused on commercial sport nutrition products. The purpose of this study was to determine the effects of varied mixed macronutrient feedings on glycogen recovery and subsequent exercise performance in both sexes.MethodsMales (n = 8) and females (n = 8) participated in a crossover study. Subjects completed a 90-min cycling glycogen depletion trial, then rested for 4 h. Two carbohydrate feedings (1.6 g kg−1) of either sport supplements or potato-based products were delivered at 0 and 2 h post-exercise. Muscle biopsies (glycogen) and blood samples (glucose, insulin) were collected during the recovery. Afterwards, subjects completed a 20 km cycling time trial.ResultsThere was no difference between sexes or trials for glycogen recovery rates (male: 7.9 ± 2.7, female: 8.2 ± 2.7, potato-based: 8.0 ± 2.5, sport supplement: 8.1 ± 3.1 mM kg wet wt−1 h−1, p > 0.05). Time trial performance was not different between diets (38.3 ± 4.4 and 37.8 ± 3.9 min for potato and sport supplement, respectively, p > 0.05).ConclusionsThese results indicate that food items, such as potato-based products, can be as effective as commercially marketed sports supplements when developing glycogen recovery oriented menus and that absolute carbohydrate dose feedings (g kg−1) can be effectively applied to both males and females.

Post-exercise carbohydrate and energy availability induce independent effects on skeletal muscle cell signalling and bone turnover: implications for training adaptation.

Reduced carbohydrate (CHO) availability before and after exercise may augment endurance training-induced adaptations of human skeletal muscle, as mediated via modulation of cell signalling pathways. However, it is not known whether such responses are mediated by CHO restriction, energy restriction or a combination of both. In recovery from a twice per day training protocol where muscle glycogen concentration is maintained within 200-350mmolkg-1 dry weight (dw), we demonstrate that acute post-exercise CHO and energy restriction (i.e. <24h) does not potentiate potent cell signalling pathways that regulate hallmark adaptations associated with endurance training. In contrast, consuming CHO before, during and after an acute training session attenuated markers of bone resorption, effects that are independent of energy availability. Whilst the enhanced muscle adaptations associated with CHO restriction may be regulated by absolute muscle glycogen concentration, the acute within-day fluctuations in CHO availability inherent to twice per day training may have chronic implications for bone turnover. We examined the effects of post-exercise carbohydrate (CHO) and energy availability (EA) on potent skeletal muscle cell signalling pathways (regulating mitochondrial biogenesis and lipid metabolism) and indicators of bone metabolism. In a repeated measures design, nine males completed a morning (AM) and afternoon (PM) high-intensity interval (HIT) (8×5min at 85% ) running protocol (interspersed by 3.5h) under dietary conditions of (1) high CHO availability (HCHO: CHO ∼12gkg-1 , EA∼ 60kcalkg-1 fat free mass (FFM)), (2) reduced CHO but high fat availability (LCHF: CHO ∼3(-1 , EA∼ 60kcalkg-1 FFM) or (3), reduced CHO and reduced energy availability (LCAL: CHO ∼3gkg-1 , EA∼ 20kcalkg-1 FFM). Muscle glycogen was reduced to ∼200mmolkg-1 dw in all trials immediately post PM HIT (P<0.01) and remained lower at 17h (171, 194 and 316mmolkg-1 dw) post PM HIT in LCHF and LCAL (P<0.001) compared to HCHO. Exercise induced comparable p38MAPK phosphorylation (P<0.05) immediately post PM HIT and similar mRNA expression (all P<0.05) of PGC-1α, p53 and CPT1 mRNA in HCHO, LCHF and LCAL. Post-exercise circulating βCTX was lower in HCHO (P<0.05) compared to LCHF and LCAL whereas exercise-induced increases in IL-6 were larger in LCAL (P<0.05) compared to LCHF and HCHO. In conditions where glycogen concentration is maintained within 200-350mmolkg-1 dw, we conclude post-exercise CHO and energy restriction (i.e. <24h) does not potentiate cell signalling pathways that regulate hallmark adaptations associated with endurance training. In contrast, consuming CHO before, during and after HIT running attenuates bone resorption, effects that are independent of energy availability and circulating IL-6.

The effects of maltodextrin and protein supplementation on serum metabolites in exercising competitive weight-pulling dogs

Post-exercise carbohydrate repletion of skeletal muscle glycogen utilising maltodextrin, with or without highly digestible protein, can improve performance in humans which has been extrapolated to dogs. There is limited metabolic evidence regarding substrate utilisation during exercise with and without supplementation other than serum hormone status and serum amino acid responses. The objectives of this study were 2-fold; (1) to examine the metabolomic changes associated with a weight-pulling exercise; and (2) to examine the effects of maltodextrin/protein supplementation on serum metabolomics during recovery. Serum was collected from 12 dogs (6 control and 6 treatment) at different time points (pre-exercise, 0 min post-exercise, 30 min post, 3 h post) and liquid chromatography-mass spectrometry (LC-MS) was performed identifying 242 metabolites. A two-way analysis of variance for time and treatment with false discovery rate correction was performed using MetaboAnalyst 3.0. There were 9 metabolites found to be significantly increased or decreased immediately after exercise from baseline representing primarily citric acid cycle metabolites. Treatment differences at 30 min post-exercise showed increases in 8 metabolites including amino acids and carbohydrate intermediates with supplementation. Thirty-seven metabolites were significantly different at 3 h post-exercise, with most metabolites being related to amino acid increases, as well as decreases in fatty acid metabolites with supplementation. Definite alterations in metabolites suggesting that post-exercise supplementation with maltodextrin and protein supports glucose metabolism and alters fatty acid metabolism or clearance during recovery from a weight-pulling exercise.

The Acute Effect of a Single Exhaustive Sprint Exercise Session on Post-Exercise Fat Oxidation Rate

Abstract It is well known that substrate oxidation rates are increased by exercise. The present study had two main objectives: firstly, to examine the effect of a single exhaustive exercise session on post-exercise substrate oxidation and energy expenditure; and secondly, to determine the differences between athletes and non-athletes. Material and methods: Eighteen healthy male athletes (mean ± SD age; 19.38 ± 2.26 years, VO2max; 60.57 ± 3.90 ml · kg-1 · min-1, n = 8) and non-athletes (age; 20.30 ± 1.26 years, VO2max; 44.97 ± 5.43 ml · kg-1 ·min-1, n = 10) volunteered to participate in the study. After an overnight fast, subjects performed a single sprint exercise session on a cycle ergometer with individual loads (0.075 kg per body weight) until volitional exhaustion. Energy expenditure (EE) and the substrate oxidation rate were measured at rest and during the post-exercise recovery period using indirect calorimetry. Results: Exhaustive exercise significantly increased post-exercise fat oxidation, energy expenditure and contribution of fat to EE (p &lt; 0.05). Also, it significantly decreased post-exercise carbohydrate (CHO) oxidation and the contribution of CHO to EE (p &lt; 0.05). However, the changes in the substrate oxidation rate and EE after the exercise test were not different between the groups (p &gt; 0.05). Conclusions: The study results suggest that a single short-duration exhaustive exercise session causes a higher fat oxidation rate during recovery than at rest, whereas training status did not affect this situation

The Effect of Postexercise Carbohydrate and Protein Ingestion on Bone Metabolism

The Effect of Postexercise Carbohydrate and Protein Ingestion on Bone Metabolism

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.

The Effect of Postexercise Carbohydrate and Protein Ingestion on Bone Metabolism

ABSTRACT This study aimed to investigate the effect of feeding carbohydrate and protein (CHO + PRO), immediately or 2 h after an exhaustive run, on the bone turnover response in endurance runners. Ten men (age = 28 ± 5 yr, height = 1.74 ± 0.05 m, body mass [BM] = 69.7 ± 6.3 kg) performed treadmill running at 75% V˙O2max, until exhaustion, on three occasions. Blood was collected before and immediately, 1, 2, 3, 4, and 24 h postexercise, for measurement of β-CTX, P1NP, parathyroid hormone, PO4, ACa, and Ca2+. This was a randomized, counterbalanced, placebo-controlled, and single-blinded crossover study. The three trials were (i) placebo (PLA), where the PLA solution was ingested immediately and 2 h postexercise; (ii) immediate feeding (IF), where CHO + PRO (1.5 g·kg−1 BM dextrose and 0.5 g·kg−1 BM whey) was ingested immediately postexercise and PLA 2 h postexercise; and (iii) delayed feeding (DF), where PLA was ingested immediately postexercise and CHO + PRO solution 2 h postexercise. Data were analyzed using repeated-measures ANOVA and Tukey's HSD post hoc test. At 1 and 2 h postexercise, β-CTX concentrations were lower in the IF trial compared with the DF and PLA trials (P ≤ 0.001). At 3 h postexercise, β-CTX concentrations were higher in the PLA trial compared with the IF (P ≤ 0.001) and DF trials (P = 0.026). At 4 h postexercise, β-CTX concentrations were lower in the DF trial compared with the IF (P = 0.003) and PLA trials (P ≤ 0.001). At 4 h postexercise, P1NP was higher in the IF trial compared with the DF (P = 0.026) and PLA trials (P = 0.001). At 3 h postexercise, parathyroid hormone was higher in the IF trial compared with the DF trial (P ≤ 0.001). After exhaustive running, immediate ingestion of CHO + PRO may be beneficial, as it decreases bone resorption marker concentrations and increases bone formation marker concentrations, creating a more positive bone turnover balance.

Metabolism and Whole-Body Fat Oxidation Following Postexercise Carbohydrate or Protein Intake.

This study investigated how postexercise intake of placebo (PLA), protein (PRO), or carbohydrate (CHO) affected fat oxidation (FO) and metabolic parameters during recovery and subsequent exercise. In a cross-over design, 12 moderately trained women (VO2max 45 ± 6ml·min-1·kg-1) performed three days of testing. A 23-min control (CON) incremental FO bike test (30-80% VO2max) was followed by 60min exercise at 75% VO2max. Immediately postexercise, subjects ingested PLA, 20g PRO, or 40g CHO followed by a second FO bike test 2h later. Maximal fat oxidation (MFO) and the intensity at which MFO occurs (Fatmax) increased at the second FO test compared to the first following all three postexercise drinks (MFO for CON = 0.28 ± 0.08, PLA = 0.57 ± 0.13, PRO = 0.52 ± 0.08, CHO = 0.44 ± 0.12g fat·min-1; Fatmax for CON = 41 ± 7, PLA = 54 ± 4, PRO = 55 ± 6, CHO = 50 ± 8 %VO2max, p < 0.01 for all values compared to CON). Resting FO, MFO, and Fatmax were not significantly different between PLA and PRO, but lower for CHO. PRO and CHO increased insulin levels at 1h postexercise, though both glucose and insulin were equal with PLA at 2h postexercise. Increased postexercise ketone levels only occurred with PLA. Protein supplementation immediately postexercise did not affect the doubling in whole body fat oxidation seen during a subsequent exercise trial 2h later. Neither did it affect resting fat oxidation during the postexercise period despite increased insulin levels and attenuated ketosis. Carbohydrate intake dampened the increase in fat oxidation during the second test, though a significant increase was still observed compared to the first test.

The Effect of Postexercise Carbohydrate and Protein Ingestion on Bone Metabolism.

This study aimed to investigate the effect of feeding carbohydrate and protein (CHO + PRO), immediately or 2 h after an exhaustive run, on the bone turnover response in endurance runners. Ten men (age = 28 ± 5 yr, height = 1.74 ± 0.05 m, body mass [BM] = 69.7 ± 6.3 kg) performed treadmill running at 75% V˙O2max, until exhaustion, on three occasions. Blood was collected before and immediately, 1, 2, 3, 4, and 24 h postexercise, for measurement of β-CTX, P1NP, parathyroid hormone, PO4, ACa, and Ca. This was a randomized, counterbalanced, placebo-controlled, and single-blinded crossover study. The three trials were (i) placebo (PLA), where the PLA solution was ingested immediately and 2 h postexercise; (ii) immediate feeding (IF), where CHO + PRO (1.5 g·kg BM dextrose and 0.5 g·kg BM whey) was ingested immediately postexercise and PLA 2 h postexercise; and (iii) delayed feeding (DF), where PLA was ingested immediately postexercise and CHO + PRO solution 2 h postexercise. Data were analyzed using repeated-measures ANOVA and Tukey's HSD post hoc test. At 1 and 2 h postexercise, β-CTX concentrations were lower in the IF trial compared with the DF and PLA trials (P ≤ 0.001). At 3 h postexercise, β-CTX concentrations were higher in the PLA trial compared with the IF (P ≤ 0.001) and DF trials (P = 0.026). At 4 h postexercise, β-CTX concentrations were lower in the DF trial compared with the IF (P = 0.003) and PLA trials (P ≤ 0.001). At 4 h postexercise, P1NP was higher in the IF trial compared with the DF (P = 0.026) and PLA trials (P = 0.001). At 3 h postexercise, parathyroid hormone was higher in the IF trial compared with the DF trial (P ≤ 0.001). After exhaustive running, immediate ingestion of CHO + PRO may be beneficial, as it decreases bone resorption marker concentrations and increases bone formation marker concentrations, creating a more positive bone turnover balance.

The effects of a post-exercise carbohydrate and protein supplement on repeat performance, serum chemistry, insulin and glucagon in competitive weight-pulling dogs.

The physiological demands of weight-pulling dogs have yet to be investigated. Two groups of competitive weight-pulling dogs both underwent two identical pull series 3h apart. The control group (n 8) was compared with a group fed a rapidly digestible carbohydrate and protein supplement after the first pull series (n 9). Blood was drawn before and after each pull series as well as at 15 and 30min after the first pull series finished. Biochemistry values remained unremarkable throughout the study in both groups regardless of supplementation or exercise over time. Lactic acid showed mild significant increases post-exercise (2·1 (sd 1·2) mmol/l) compared with baseline (1·4 (sd 0·3) mmol/l; P=0·03) after the initial pull series. When examining the effects of time there was a significant increase in insulin from baseline (median of 10·8 (range 6·8-17·4) μIU/ml) compared with 30min after supplementation (17·0 (range 8·1-33·0) μIU/ml) and at 3h after supplementation (19·2 (range 9·7-53·4) μIU/ml). In the treatment group there was also a time effect, with glucagon being elevated from baseline (median of 100 (range 79-115) pg/ml) compared with 30min after supplementation (114 (range 90-183) pg/ml) and after the second pull series (131 (range 107-152) pg/ml). Evaluation of each dog's ability to pull the same or greater amount of weight on the second pull series revealed no significant differences. In conclusion, weight-pulling dogs have mild elevations in lactate reflecting little anaerobic metabolism compared with other canine sprinting athletes; hormonal changes associated with carbohydrate absorption are reflected within the treatment group, and supplementation had no effect on performance.

Glycogen availability and skeletal muscle adaptations with endurance and resistance exercise.

It is well established that glycogen depletion affects endurance exercise performance negatively. Moreover, numerous studies have demonstrated that post-exercise carbohydrate ingestion improves exercise recovery by increasing glycogen resynthesis. However, recent research into the effects of glycogen availability sheds new light on the role of the widely accepted energy source for adenosine triphosphate (ATP) resynthesis during endurance exercise. Indeed, several studies showed that endurance training with low glycogen availability leads to similar and sometimes even better adaptations and performance compared to performing endurance training sessions with replenished glycogen stores. In the case of resistance exercise, a few studies have been performed on the role of glycogen availability on the early post-exercise anabolic response. However, the effects of low glycogen availability on phenotypic adaptations and performance following prolonged resistance exercise remains unclear to date. This review summarizes the current knowledge about the effects of glycogen availability on skeletal muscle adaptations for both endurance and resistance exercise. Furthermore, it describes the role of glycogen availability when both exercise modes are performed concurrently.

Timing of post-exercise carbohydrate ingestion: influence on IL-6 and hepcidin responses.

Carbohydrate ingestion prior and during exercise attenuates exercise-induced interleukin-6. This investigation examined if an analogous effect was evident for interleukin-6 and hepcidin response when carbohydrates were ingested post-exercise. In a crossover design, 11 well-trained endurance athletes completed two experimental trials. Participants completed an 8 × 3 min interval running session at 85 % vVO2peak followed by 5 h of monitored recovery. During this period, participants were provided with two 1.2 g kg(-1) carbohydrate beverages at either an early feeding time (immediately post-exercise and 2 h post-exercise) or delayed feeding time (2 h post-exercise and 4 h post-exercise). Venous blood samples were collected pre-, immediately post-, 3 and 5 h post-exercise. Samples were analysed for Interleukin-6, serum iron, serum ferritin and hepcidin. Interleukin-6 was significantly elevated (p = 0.004) immediately post-exercise compared to baseline for both trials. Hepcidin levels were significantly elevated at 3 h post-exercise (p = 0.001) and 5 h post-exercise (p = 0.002) compared to baseline levels in both trials, with no significant difference between the two conditions and any time point. Serum iron was significantly increased from baseline to immediately post-exercise (p = 0.001) for both trials, with levels decreasing by 3 h (p = 0.025) and 5 h post-exercise (p = 0.001). Serum ferritin levels increased immediately post-exercise compared to baseline (p = 0.006) in both conditions. The timing and ingestion of post-exercise carbohydrate ingestion do not appear to impact post-exercise interleukin-6 and hepcidin responses; this is likely a result of the interval running task inducing an inflammatory response and subsequent up-regulation of hepcidin.

Dietary Behaviors of Amateur Endurance Athletes during Recovery from Exercise Training

PURPOSE: It is not known if amateur endurance athletes (runners, cyclists, triathletes, etc.) comply with nutrition guidelines for optimal recovery from exercise. We hypothesized that these athletes do not meet the recommendations from professional organizations for carbohydrate, protein, and fluid intake after exercise. METHODS: Data were collected by using an online questionnaire, 2-day food diaries and exercise logs. Specific post-exercise time periods in the food diaries were analyzed using computer software; nutrient intakes were compared to the published recommendations. RESULTS: Carbohydrate intake during the 30-min and 2-hr window immediately after exercise cessation was lower than recommended (24±7 vs. 70±2 g, p<0.001, 47±10 vs 70±2 g, p=0.012, respectively), as was carbohydrate intake between 2 and 4 hr after exercise (34±11 vs. 70±2 g, p=0.002) and between 4 and 6 hr (48±13 vs. 70±2 g, p=0.042); most subjects (75-88%) failed to meet the carbohydrate intake recommendations during these time periods. There was also a non-significant tendency for carbohydrate intake to be lower than recommendations in the 24 hours after exercise (390±24 vs. 419+15 g p=0.089). Protein intake within 1 hour of exercise and total daily protein intake met or exceeded the recommendations. Fluid intake within 1 hour of exercise met the recommendations. CONCLUSION: Amateur endurance athletes are not meeting the recommendations for post-exercise carbohydrate intake, specifically within 30 minutes, 2 hrs, 4 hours, and 6 hr of exercise, but they are meeting the recommendations for daily and post-exercise protein intake, and hydration status during exercise.