SportsMed_June04 SPORTS MEDICINE VOL 16 NO.2 2004 33 Introduction Protein turnover (protein synthesis and breakdown) is typi- cally increased during and post-exercise. With heavy resis- tance exercise certain muscle fibres are disrupted or damaged and need to undergo a remodelling and repair process during the recovery period.16 For a detailed review of exercise-induced muscle damage and inflammation see Pyne.56 Muscle damage or disruption (protein breakdown) is influenced by the duration, intensity and type of exercise (eccentric vs. concentric), as well as training status.16 It has been shown that with regular exercise training, the rise in protein breakdown is attenuated.54 During endurance-type training there is also an increase in protein breakdown in order to sustain exercise metabolism, which increases when muscle glycogen stores are depleted. In order for muscle repair, recovery and adaptation to take place post-exercise, a positive nitrogen balance is needed in order to allow for a state of net protein synthesis.71 This shift from a catabolic to anabolic state is mediated by the pres- ence of certain dietary nutrients, hormones and growth fac- tors.71 Protein synthesis and skeletal muscle repair post-exercise have been shown to increase in response to adequate energy and amino acid availability, while protein breakdown is decreased by insulin.68 Furthermore, resis- tance exercise and amino acid availability have additive effects in terms of protein synthesis.6 This article (Part II) will focus on dietary factors that contribute to protein synthesis and skeletal muscle repair during the recovery period. REVIEW ARTICLE Dietary macronutrient recommendations for optimal recovery post-exercise: Part II H H Wright (MSc Dietetics, PhD Nutrition)1 A Claassen (BSc (Hons) Dietetics, BSc (Med) (Hons) Exercise Science)2 J Davidson (DSc)3 1Potchefstroom Institute of Nutrition, Faculty of Health Sciences, Northwest University, South Africa 2UCT/MRC Research Unit for Exercise Science and Sports Medicine, Faculty of Health Sciences, University of Cape Town, South Africa 3College of Education and Health Sciences, Bradley University, Peoria, Illinois, USA CORRESPONDENCE: H Wright School of Physiology, Nutrition and Consumer Science North-West University Private Bag X6001 Potchefstroom, 2531 Tel: 018-299 2482 Fax: 018-299 2464 E-mail: vgehhw@puk.ac.za Abstract A net positive nitrogen balance is needed for exercise- induced muscle damage to be repaired during the recov- ery period. Apart from hormones and growth factors, adequate energy and amino acid availability contribute to this balance and influence the rate at which protein syn- thesis and muscle repair occur post-exercise. This paper reviews the dietary factors involved in muscle repair dur- ing the post-exercise recovery period. Both resistance and endurance-trained athletes have a higher dietary pro- tein requirement of between 1.2 and 1.8 g protein/kg body weight (BW)/day, with an upper limit of 2 g protein/kg BW/day. To increase the rate of protein synthesis during the recovery period, immediate ingestion of protein post- exercise is recommended. Additionally, ingesting 1.2 g carbohydrate (CHO)/kg BW/hour with 0.4 g/kg BW/hour of a wheat amino acid mixture (wheat protein hydrolysate combined with free leucine and phenylalanine) enhances the insulin response compared with ingesting CHO only or combined with other protein hydrolysates, peptides, or intact protein. This increased insulin response could increase muscle protein synthesis indirectly by altering the hormonal milieu. Results on the anabolic effect of sin- gle or mixtures of amino acids remains to be further elu- cidated. The possible antioxidant benefits of whey protein supplementation in athletes remains to be proven, while the antioxidant potential of soy protein holds promise. The effect of glutamine supplementation on protein syn- thesis in athletes is limited and its clinical relevance for enhanced immune function in endurance athletes remains to be established. Creatine supplementation seems to be beneficial in terms of protein synthesis and gains in fat free mass during the recovery period, while the use β-hydroxy β-methylbutyrate (HMB) supplementation by trained athletes seems to have limited benefits. It is important to keep dietary advice individualised consider- ing the complexity in which the endocrine system regu- lates cell function, the diverse mechanisms that control homeostasis, as well as genetic variability. 34 SPORTS MEDICINE VOL 16 NO.2 2004 Dietary factors involved in muscle repair Overall dietary protein requirements with regular exercise training Intensive and/or high-volume aerobic and weight-training exercise increase the protein requirement for muscle repair, adaptation, and to remain in positive nitrogen balance.1 During prolonged endurance exercise, protein may also con- tribute as fuel to the overall energy demand, however, this contribution remains small (< 5 - 10%), with carbohydrate (CHO) and fat contributing to most of the energy demand.60 At the onset of a training programme, protein requirements may be slightly higher compared with the latter part of a training cycle where adaptation has already taken place.40 A range of 1.2 - 1.8 g protein/kg body weight (BW)/day is rec- ommended for resistance and/or endurance-trained athletes, however, an upper limit for protein ingestion has been set at 2 g/kg BW/day beyond which there is no added benefit of ingesting more protein. Ingesting > 2 g protein/kg BW/day will not enhance muscle repair and adaptation any further,1 and may be detrimental to health.23 One exception would be athletes training at high altitude, which elicits a greater cata- bolic response and increases protein requirements to ~ 2.2 g protein/kg BW/day in order to remain in positive nitrogen balance.66 Timing of protein intake An amino acid tracer infusion study (~ 0.15 g amino acid mix- ture/kg BW/hour for 3 hours) by Biolo and co-workers6 indi- cated an increased rate of muscle protein synthesis with hyperaminoacidaemia post-exercise compared with rest. This was supported by Rasmussen and co-workers58 who found that ingesting an essential amino acid-CHO supple- ment (6 g amino acids + 35 g sucrose/serving) at 1 or 3 hours after resistance exercise resulted in similar rates of muscle protein synthesis, which was ~ 400% above pre-drink values. Levenhagen and co-workers42 then showed that ingesting a high-protein supplement (10 g protein + 8 g CHO + 3 g fat/serving) immediately after an exercise bout (cycling for 60 minutes at 60% maximal oxygen uptake (VO2max)) enhanced whole-body protein synthesis three-fold compared with delayed ingestion (3 hours post-exercise), and signifi- cantly increased dynamic and isokinetic strength.19 Levenhagen and co-workers41 also investigated the poten- tial of nutrient intake post-exercise in terms of enhanced recovery of whole-body and skeletal muscle protein home- ostasis. Subjects were given either a placebo, a CHO-fat supplement (8 g CHO + 3 g fat/serving), or a CHO-protein- fat supplement (8 g CHO + 10 g protein + 3 g fat/serving) immediately after a 60-minute exercise period (cycling at 60% VO2max). After a 2-hour recovery period there was a net gain in whole-body protein and leg protein in the CHO-pro- tein-fat supplement group, while the placebo and CHO-fat supplement group resulted in a net loss in the same mea- surements. From these results it can be concluded that amino acid availability post-exercise is more important than energy for muscle repair and synthesis during recovery. A study by Tipton and co-workers70 found an increased rate of muscle protein synthesis 1 hour after resistance exercise when an oral essential amino acid-CHO supplement (35 g sucrose + 6 g essential amino acids) were given prior to the exercise bout compared with immediately afterwards. The main contributor to this increase was an increased delivery of amino acids to the muscle when ingested prior to exercise. In summary, it seems that the earlier amino acids are available post-exercise, the quicker a positive nitrogen bal- ance can be achieved which could contribute to increased muscle protein synthesis, hypertrophy and strength. Ingestion of protein or amino acids prior to exercise might have beneficial effects on enhancing post-exercise recovery, however, further research is needed to confirm this effect. Furthemore, pre-exercise protein ingestion may have ergolytic effects due to increased ammonia production (explained in more detail later).13,43 Type of protein and amino acids Since amino acids and their metabolites are involved in mus- cle repair,6 post-exercise ingestion of intact protein, or sup- plementation with specific amino acids and their metabolites has been suggested to optimise muscle repair and adapta- tion. Adequate essential amino acids may be derived from the ingestion of intact protein, either in animal or soy-based foods.78 Available protein products include whey protein, milk isolates, caseinates, soy isolates, and other vegetable pro- teins. There is no consensus regarding which protein type is the best. It is important to note that ingestion of amino acids, when dietary protein intake is sufficient, does not further increase the rate of muscle repair.66 Furthermore, unrestrict- ed supplementation with single amino acids or amino acid mixtures is associated with metabolic imbalances, toxicity, as well as degeneration of myofibrils and disrupted mitochondr- ial membranes.23;37 Protein peptides/hydrolysates Van Loon and co-workers73 investigated the insulinotrophic effect of various drinks containing 0.8 g CHO/kg BW/hour combined with 0.4 g/kg BW/hour of different combinations of amino acids and/or protein sources ingested under resting conditions. The drinks were given at 30-minute intervals over a 2-hour period. Their main finding was that the oral intake of 0.4g/kg BW/hour of wheat protein hydrolysate com- bined with free leucine and free phenylalanine in the post- absorptive, resting state can produce a larger (~100%) insulin response when compared with the ingestion of CHO only, and comparable with the ingestion of a drink containing 0.4 g/kg BW/hour of free leucine, free phelylalanine and argi- nine. This drink, however, did not produce the severe symp- toms of gastro-intestinal upset and diarrhoea that was observed with the ingestion of drinks containing large doses of free amino acids, particularly free leucine, arginine, phenylalanine and glutamine.73 When comparing the ingestion of protein hydrolysates with intact protein, it was concluded that the use of protein hydrolysates is more preferable seeing that it results in a faster increase in plasma amino acid concentrations and stimulation of insulin secretion during a 2-hour period com- pared with intact protein.73 SPORTS MEDICINE VOL 16 NO.2 2004 35 Subsequently, Van Loon et al.72 investigated the insulinotrophic effects of post-exercise ingestion of 1.2 g CHO/kg BW/hour combined with differing amounts of wheat protein hydrolysate (0.2 or 0.4 g/kg BW/hour), with or without free leucine and phenylalanie at 30-minute intervals up to 3 hours post-exercise in trained men. Ingestion of wheat hydrolysate only (either 0.2 or 0.4 g/kg BW/hour) combined with 1.2 g CHO/kg BW/hour did not increase post-exercise insulin response compared with the ingestion of 1.2 g/kg BW/hour of CHO only. However, addition of free leucine and phenylalanine resulted in a substantial increase in insulin response. Additionally, a dose-related effect existed seeing that increasing the amount of wheat-amino acid mixture from 0.2 to 0.4 g/kg BW/hour resulted in a significant increase in the insulin response. Furthermore, a strong positive correla- tion between insulin response and plasma leucine, phey- lanaline and tyrosine concentrations existed.73 Increased plasma amino acid concentrations may directly (by providing substrate) and indirectly (by altering the anabolic hormonal milieu) increase muscle protein synthesis (for review see Tessari and co-workers68 ). Commercially, whey protein is marketed as a superior protein by manufacturers not only due to its high-quality pro- tein, but also due to its bio-availability and ease of dispersion in supplements and bars. Compared with other protein sources, whey has been found to contain a higher comple- ment of essential amino acids (EAAs) and branched-chain amino acids (BCAAs), and to result in greater biological value in humans.38 Additionally, whey protein contains more cysteine than casein. Cysteine is considered important for glutathione (potent antioxidant) production.12 It is due to this characteristic that it is hypothesised that the ingestion of whey protein post-exercise may protect against exercise- induced free radical damage. Though a number of studies (mostly done on animals) have demonstrated positive immune system benefits and antioxidant action with whey protein supplementation, these effects remain to be proven in physically active human populations. Soy protein also offers a high-quality protein, which is equivalent to casein and egg protein78 and may therefore also contribute to protein synthesis if ingested post-exercise. Additionally because of its high content of genistein and other phytochemicals, soy may have advantages in improv- ing post-exercise recovery by increasing its antioxidant potential which could attenuate muscle breakdown.3 Research investigating these possible effects during and post-exercise by evaluating skeletal muscle repair, oxidative function, antioxidant mechanisms, and immune function are, however, limited. Two studies in athletes demonstrated reduced exercise-induced antioxidant stress and muscle damage after consumption of a soy beverage post-exer- cise.3,62 Single amino acids and amino acid mixtures It has been suggested that supplementation of single amino acids or amino acid mixtures may attenuate the hormonal milieu (e.g. stimulate insulin and growth hormone release) with subsequent anabolic effects on protein metabolism,68 and/or directly stimulate the rate of muscle repair compared with the ingestion of intact protein.35 In vitro studies have shown that particularly leucine, phenylalanine, arginine and glutamine have powerful stimu- lating effects on insulin release by pancreatic β-cells.7 Floyd and co-workers20 reported that intravenous injection of 30 g of arginine in humans resulted in a similar insulin response as found with the injection of a 30 g amino acids mixture (arginine, lysine, phehylalanine, leucine, valine, methionine, histidine, isoleucine, threonine, and tryptophane). In con- trast, Van Loon and co-workers73 demonstrated that oral ingestion of a large dose of arginine (0.4 g/kg BW/hour) was not effective in increasing plasma arginine or insulin concen- trations. This was probably due to poor intestinal absorption of arginine due to severe diarrhoea that was elicited after ingestion.73 These results indicate that oral administration of large doses of arginine (and perhaps also other single amino acids) to stimulate growth hormone release and muscle anabolism should be practised with caution and is best avoided. Blomstrand and Saltin10 investigated the influence of a BCAA supplement (150 ml containing 45% leucine, 30% valine, 25% isoleucine) given 15 minutes before exercise, at 15-minute intervals during 1 hour of 1-legged exercise and at 15, 30, 60 and 90 minutes of recovery on muscle protein metabolism. They found that the supplement had a protein- sparing effect during recovery, which seemed to be insulin- dependent. Results from other studies suggest that the pro- tein-sparing effect could have been attributed to a decrease in the rate of protein degradation.17,47 In an earlier study, Blomstrand and Newsholme9 showed that the ingestion of 7.5 g BCAA during a 30 km cross-country race or full marathon decreased the net rate of exercise-induced protein degradation. Possible mechanisms proposed by Coombes and McNaughton17 include: (i) BCAAs increase anabolism and decrease catabolism, thus there is less damage to pro- teins associated with cell membranes; (ii) BCAAs increase sensitivity of muscle to anabolic actions of insulin, thereby increasing protein synthesis; (iii) BCAAs increase their own oxidation, thus limiting muscle damage; and (iv) BCAAs sup- press degradation during and after sustained exercise via alpha-ketoisocaproate (KIC). BCAAs can increase KIC con- centration which inhibits muscle proteolysis in vitro, thereby contributing to a decrease in degradation.17 No influence on exercise-induced hormonal response has, however, been found after 1 week of high-volume weight training and inges- tion of 2.4 g amino acid supplement prior to each meal, as well as 2.1 g BCAA supplement prior to each workout ses- sion for 1 week.21 The ingestion of a large single dose (~ 300 mg/kg BW) of BCAA ingested 15 - 30 minutes before and/or during exer- cise has been shown to increase ammonia production during exercise.43 After a series of observations Brouns and co- workers13 hypothesised that high intramuscular ammonia concentration may be related to the aetiology of muscle exhaustion during prolonged, strenuous endurance exercise. Other studies found no effect of BCAA ingestion on ammo- nia production, especially with low amounts (< 100 mg/kg BW) ingested as multiple smaller doses before or during exercise.8,46 Enhanced responsiveness of the pituitary corticotrophin and gonadotropin secretory cells to their releasing hormones (e.g. growth hormone) has been shown 60 minutes after the 36 SPORTS MEDICINE VOL 16 NO.2 2004 ingestion of an amino acid mixture (100 mg arginine/kg BW + 80 mg ornithine/kg BW + 140 mg BCAA + 10 g glucose/serving).18 An earlier study36 showed no influence on growth hormone concentration after the ingestion of three different amino acid drinks according to manufacturer's instructions (drink A = 2.4 g L-arginine/L-lysine/serving; drink B = 1.1 g L-ornithine, 750 mg pyridoxine HCL, 125 mg ascor- bic acid; drink C = 20 g Bovril: 7.8 g protein, 580 mg CHO, 146 kJ) after an 8-hour fast. It can be concluded that growth hormone secretion may be affected by the type of amino acid, its dosage and the specific combination of amino acids ingested, but more research is needed to confirm these find- ings. The question of EAA compared with mixed amino acid (MAA) supplements on protein synthesis has also sparked some interest. Tipton and co-workers69 found that the inges- tion of either a MAA (40 g/serving) or EAA (40 g/serving) supplement after a resistance exercise protocol led to similar net positive protein balance compared with a negative pro- tein balance with placebo ingestion. They therefore showed an anabolic response post-exercise, with or without EAA, which was also comparable to intravenous amino acid infu- sions. A more recent study11 found a significantly higher net muscle protein balance response after a resistance exercise protocol when an EAA (6 g/serving) supplement was ingest- ed post-exercise compared with a non-EAA (3 g EAA + 3 g non-EAA/serving) supplement. It can be concluded from these studies that there might be a threshold for the amount of EAA needed to stimulate protein synthesis and that non- EAA is not necessary to achieve protein balance. Glutamine Glutamine is a major fuel source to the intestinal wall (brush border) and due to the high turnover of these cells they need a continual supply of amino acids for protein synthesis.77 Thus, cells of the intestine may be preferentially supplied with amino acids for oxidation and protein synthesis at the expense of skeletal muscle protein.28 It is therefore hypothe- sised that providing dietary glutamine can 'spare' intramus- cular glutamine, while supplying the intestine with needed glutamine. This would contribute to a decrease in proteoly- sis secondary to lowered blood glutamine concentrations. Hankard and co-workers,25 however, found no change in glu- tamine release from proteolysis after a glutamine infusion study done at rest, whilst demonstrating an increase in pro- tein synthesis during glutamine infusion at rest.26 It therefore seems that glutamine supplementation may have an anabol- ic effect based on its influence on protein synthesis. Additionally, glutamine has been reclassified as a condition- ally essential amino acid during certain stressful conditions (including strenuous exercise).24 Most studies investigating the effect of glutamine on muscle protein metabolism have, however, been done in the clinical setting. Thus, studies investigating the direct influence of glutamine supplementa- tion on muscle protein synthesis in athletes are limited. Welbourne75 showed an increased plasma growth hor- mone concentration 90 minutes after ingestion of 2 g gluta- mine over a 20-minute period. Whether chronic ingestion of glutamine will result in a continued increase is, however, not known. Glutamine supplementation (0.35 g/kg BW/day for 14 days) in wrestlers consuming a hypocaloric diet resulted in the maintenance of a positive nitrogen balance, while the placebo group was in a negative nitrogen balance at the end of the supplementation period.61 Decreases in plasma glutamine concentrations has been shown after strenuous prolonged exercise, which could influ- ence immune system regulation59 since glutamine is an important fuel source for lymphocytes and macrophages.2 Decreased glutamine concentrations have also been found in athletes suffering from 'over-trained syndrome'.48 The reduced glutamine concentrations seen after prolonged endurance-type exercise have been proposed to be a result of increased glutamine use by cells of the immune system.48 The effects of glutamine supplementation in endurance ath- letes on the immune system function are, however, contra- dicting (for review see Rohde and co-workers59). Thus, although glutamine supplementation to enhance immune system function is currently a popular practice amongst ath- letes, further scientific research is needed to establish the clinical relevance of glutamine supplementation in athletes in order to enhance immune system function. β-Hydroxy β-Methylbutyrate (HMB) HMB is a metabolite of leucine and has been suggested to increase strength and fat free mass (FFM).49 The metabolic function and fate of HMB are not fully understood (for a detailed review see Nissen and Abumrad49). Preliminary data suggests that HMB may be part of some structural com- ponent within tissues or membranes.49 The proposed mech- anism of increased strength and FFM is thought to be linked to HMB's anti-catabolic effects and inhibition of proteolysis.55 Leucine and KIC (an intermediate in leucine breakdown to HMB) have both been shown to inhibit proteolysis.49 Most studies on HMB focus on its effect on FFM accretion and strength gains. The preponderance of data suggest an increase in FFM and strength with the supplementation of 1.5 - 3 g HMB/day for at least 3 weeks combined with ≥ 2 times/week resistance training.22,30,50,52 Two clinical studies15,44 also found a decrease in protein degradation and increases in FFM when cachectic patients were supplemented with a HMB-mixture (3 g HMB + 14 g L- glutamine + 14 g L-arginine/day) for 8 weeks without physi- cal activity compared with a placebo group. Knitter and co-workers32 investigated the effect of HMB supplementation (3 g HMB/day 6 weeks prior to and 4 days after a prolonged run) in endurance-trained males and females. The placebo group exhibited a significantly greater increase in creatine phosphokinase and lactate dehydroge- nase activity compared with the HMB-supplemented group. These results suggest that HMB prevents exercise-induced muscle damage, which results have been supported by oth- ers.52 Kreider and co-workers,33 however, found no difference in whole body anabolic/catabolic markers, body composition, muscle enzyme efflux or one repetition maximum (1-RM) in resistance-trained men after 28 days of HMB supplementa- tion (3 or 6 g HMB/day) combined with 7 hours/week resis- tance training. On the other hand, Panton and co-workers52 found that HMB supplementation (3 g HMB/day for 4 weeks) combined with a resistance training programme increased body strength and minimised muscle damage regardless of SPORTS MEDICINE VOL 16 NO.2 2004 37 gender or training status. A possible reason for discrepancy in results could be that training loads were inadequate in the study by Kreider and co-workers,33 since subjects' resistance training was not monitored on a day-by-day training basis. Additionally, lack of significance might have been due to small statistical power since there were small numbers of subjects per treatment group. Lastly, the combination of HMB and creatine (20 g crea- tine + 3 g HMB/day for 7 days followed by 10 g creatine + 3 g HMB/day for 14 days) during a weight-training pro- gramme has also been shown to increase body strength and FFM and their effects seem to be additive.30 It is, however, important to note that most studies that found a positive relationship between HMB and FFM or strength were done by the same research group. Furthermore, it is important to note that the majority of stud- ies that showed an increase in FFM22,30 and/or strength22,30,52 were done on untrained subjects embarking on a training programme. Those studies done on trained individuals33,51,57,65 found no effect of HMB supplementation on measures of FFM and strength. Creatine Creatine is a naturally occurring compound derived from the amino acids glycine, arginine, and methionine.4 The daily requirement of creatine is approximately 2 - 3 g and can be obtained exogenously from the diet, primarily meat and fish, while the remainder is synthesised endogenously.4 Numerous studies have demonstrated that creatine sup- plementation is associated with an enhanced ability to per- form repeated bouts of high-intensity exercise interspersed by short recovery periods mainly attributed to increased adenosine triphosphate (ATP) re-phosphorylation (for review see Beduschi4). Creatine supplementation typically consists of a loading phase (2 - 5 days) in which 20 g creatine/day (4 x 5 g doses spread over the course of a day) is ingested, fol- lowed by a maintenance phase (≥ 3 days) in which 2 - 5 g creatine/day is ingested.67 It is hypothesised that creatine supplementation can be beneficial during the recovery phase in terms of protein syn- thesis and gains in FFM. Many studies have reported a sig- nificant increase in FFM, ranging from 1 to 2.2 kg with creatine supplementation.5,34,67 The gain in body mass has traditionally mainly been attributed to water retention within the muscle due to increased cellular osmolarity.31,34 However, it has been suggested that creatine ingestion may also stim- ulate myofibrillar protein synthesis27,67,76 and/or inhibit protein breakdown53 and thereby increase FFM. Another proposed mechanism includes an increased resynthesis of ATP which could allow for an increased training capacity and higher quality exercise bouts, thereby increasing exercise-induced stimulation of muscle protein synthesis. Additionally, creatine may play a role in glycogen synthe- sis, mediated by drawing water via an osmotic effect into the intracellular compartment.5,74 It is, however, important to note that some people might be non-responders to creatine supplementation and there- fore not gain any benefit from it.39 The reason for this is not clear but might be linked to habitual dietary habits (fish and meat consumption), as well as muscle fibre composition.39 Combination of protein with other substrates CHO and protein The insulinotrophic and endocrine effects of combined pro- tein and CHO may attenuate muscle breakdown64 and increase muscle protein synthesis.58 Chandler and co-work- ers14 found significantly higher plasma insulin levels post- exercise when experienced male weight lifters consumed isocaloric CHO (1.5 g CHO/kg BW/serving) and CHO-protein (1.06 g CHO + 0.41 g protein/kg BW/serving) supplements compared with an isocaloric protein only (1.38 g protein/kg BW/serving), as well as a control supplement. Furthermore, growth hormone levels were significantly greater with the CHO-protein supplement at 6 hours post-exercise. The opti- mal CHO:protein ratio for muscle repair and anabolic hor- monal milieu seem to be 4-7:1.58 Combining protein, CHO and fat Roy and co-workers63 found that the addition of fat to a CHO and protein meal did not influence post-exercise muscle repair negatively. Furthermore, positive correlations have been shown between testosterone levels and the percentage of overall dietary fat, mono-unsaturated and saturated fat. However, a negative correlation with polyunsaturated-to-sat- urated fatty acid ratio was reported.45 Practical considerations with protein ingestion Increasing the protein (and fat) content of a meal/beverage may decrease gastric emptying and subsequent intestinal absorption of nutrients.29 This is of practical importance when including protein in the before, during, or post-exercise CHO beverage seeing that it may ultimately delay CHO (glu- cose) absorption and availability for energy production and the regeneration of muscle glycogen stores, both critical fac- tors for increased exercise performance and post-exercise recovery (as discussed earlier). Additionally, delayed gastric emptying may contribute to feelings of stomach discomfort (fullness or bloatedness), which might dampen appetite and decrease the volume of food, and more specifically, the amount of CHO ingested in the post-exercise recovery period. As discussed earlier, when multiple exercise or competition sessions are per- formed within a day and recovery time is limited, decreased CHO intake and availability, as well as stomach discomfort may decrease the rate of recovery post-exercise and/or directly decrease exercise performance. Post-exercise pro- tein ingestion should ideally not exceed 0.2 - 0.4 g/kg BW/hour. Furthermore, oral ingestion of single amino acids in large doses should be avoided as it may cause gastro- intestinal upset and diarrhoea.73 Lastly, long-term excessive protein and/or amino acid intake (> 2 g/kg BW/day) may contribute to overweight (espe- cially if overall calorie intake is excessive), as well as increased urinary calcium losses, which could lead to the development of osteoporosis if calcium intake is inade- quate.23 Other adverse effects include hypotension, tumour stimulation, mental retardation, and fatty liver (for detailed review see Garlick23). 38 SPORTS MEDICINE VOL 16 NO.2 2004 Conclusions Although athletes have a higher protein need than sedentary individuals to maintain a positive nitrogen balance, ingesting more protein (> 2 g/kg BW/day) than is needed to maintain this balance will not result in further enhancements in mus- cle repair and adaptation. In fact, excessive protein and/or amino acid intake may contribute to various adverse effects and gastro-intestinal upsets. The sooner protein is ingested post-exercise the faster the body is shifted into an anabolic environment, which is important for protein synthesis and adaptation. It seems that protein hydrolysates result in high- er insulin secretions than intact protein. Furthermore adding leucine and phenylalanine to a protein hydrolysate could cause even greater insulin secretion, thereby creating an anabolic hormonal milieu. The insulinotrophic and endocrine effects of combined protein and CHO ingestion (~0.8 g CHO/kg BW/hour + 0.2 - 0.4 g protein/kg BW/hour) may reduce muscle breakdown and increase muscle protein syn- thesis in the post-exercise period. The effect of glutamine supplementation on immune func- tion still needs further investigation to establish its clinical rel- evance. HMB supplementation seems to increase FFM and strength when untrained individuals start a training pro- gramme, with little proven benefits in trained individuals. Creatine supplementation seems to be beneficial during the recovery phase in terms of protein synthesis, gains in FFM and glycogen storage. Practical recommendations It is concluded from Part I and Part II of this contribution that macronutrient manipulation is a potential strategy to enhance recovery and the adaptation process post-exercise. It is, however, important to keep dietary advice individualised considering the complexity in which the endocrine system regulates cell function, the diverse mechanisms that control homeostasis, as well as genetic variability. Considering the relevant literature discussed in Parts I and II of this article, the following recommendations for enhanced muscle repair and muscle glycogen storage post- exercise are made: Short ≤ 6 hours) recovery period • Ingest 1 - 1.5 g high GI CHO/kg BW immediately post- exercise and at 15 - 60-minute intervals for 3 - 4 hours thereafter, OR 0.8 g high GI CHO + 0.2 - 0.4 g protein/kg BW immediately post-exercise and at 15 - 60-minute intervals for 3 - 4 hours thereafter. Practice with various amounts and combinations in order to establish individual tolerance and stomach comfort. • Aim at an overall ingestion of 7 - 10 g CHO/kg BW within a 24-hour period, especially when participating in multi- day competition events. • Do not exceed 2 g protein/kg BW/day. • Opt for protein hydrolysates with added leucine and phenylalanine. • Limit dietary fat intake since it could lower the GI of the CHO food and hence delay gastric emptying and the absorption and supply of nutrients to the muscle. Longer (> 6 hours) recovery period • Ingest 6 - 8 g low or high GI CHO/kg BW/day for a mod- erate-intensity training schedule. • Ingest 7 - 10 g low and/or high GI CHO/kg BW/day for a strenuous or prolonged training or competition schedule, especially when participating in strenuous multi-day com- petition events. • Ingest 1.2 - 1.8 g protein/kg BW/day for a resistance and/or endurance exercise training schedule. • Do not exceed 2 g protein/kg BW/day. • Athletes training at altitude can increase protein intake to 2.2 g protein/kg BW/day. • The addition of fat to a meal or supplement does not have any negative impact as long as total amount of CHO and protein ingested are sufficient and a favourable body fat is maintained. • When using creatine supplementation a loading phase may be followed consisting of 20 g creatine monohydrate powder/day for 3 - 5 days. This 20 g dose should be divid- ed into 4 x 5 g dosages, spread out over the course of a day. 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