Sports Nutrition and Supplements – Effective Strategies for Enhancing Performance and Body Composition
The scientific investigation of various sports nutrition and supplement strategies has undergone a tremendous growth in the last decade. The purpose of this review is to cover the latest science regarding several of the major categories in sports nutrition and performance enhancing supplements. They include: sports drinks, nutrient timing, protein, creatine and caffeine.
It is generally accepted that consuming traditional sports drinks (i.e. water, 6-8% carbohydrate, electrolytes [sodium, potassium]) during exercise is an effective tool in rehydration as well as enhancing exercise performance.(1-3) Marketing of these sports drinks also suggest their superiority as a recovery beverage post-workout. Though this is the commonly accepted paradigm in exercise and sports sciences, recent evidence suggests the contrary. Interestingly, the consumption of sports drinks during an 18-km run in cool environmental conditions is no better in comparison to mineral water.(4) Perhaps, the traditional sports drink (i.e. carbohydrate plus electrolyte solution) can be improved by the addition of protein.
In a recent investigation, scientists determined whether endurance cycling performance and post-exercise muscle damage were altered when consuming a carbohydrate and protein beverage (CHO+P; 7.3% and 1.8% concentrations) versus a carbohydrate-only (CHO; 7.3%) beverage. They had 15 male cyclists (average V02peak of 52.6 ml/kg/min) ride a cycle ergometer at 75% VO2peak to volitional exhaustion; twelve to 15 hours later, they performed a second ride to exhaustion at 85% of V02peak.
Subjects consumed 1.8 mL per kg body weight (BW) of randomly assigned CHO or CHO+P beverage every 15 min of exercise, and 10 mL per kg BW immediately after exercise. Beverages were matched for carbohydrate content, resulting in 20% less calories in CHO beverage versus the CHO+P. Subjects were blinded to treatment beverage and repeated the same protocol seven to 14 days later with the other beverage.
In the first ride to exhaustion, subjects rode 29% longer (P
There were no significant differences in exercising levels of oxygen uptake, ventilation, heart rate, perceived exertion, blood glucose, or blood lactate between treatments in either trial. According to these investigators, “a carbohydrate beverage with additional protein calories produced significant improvements in time to fatigue and reductions in muscle damage in endurance athletes. Further research is necessary to determine whether these effects were the result of higher total caloric content of the CHO+P beverage or due to specific protein-mediated mechanisms.(5)
It should be noted that there are other studies which indicate that the provision of protein to a carbohydrate-containing beverage is superior to carbohydrate alone. Ivy et al. found that the addition of protein to a carbohydrate supplement enhanced aerobic performance above that which occurred with carbohydrate alone.(6) Borsheim et al. discovered that after heavy resistance exercise, a mixture of whey protein, amino acids, and carbohydrate stimulated muscle protein synthesis to a greater extent than isocaloric carbohydrate.(7) Thus, one can reasonably conclude that adding protein to a carbohydrate-containing beverage is as good or superior to carbohydrate alone with regards to performance and recovery. Certainly, from a practical standpoint one can posit that the addition of protein, albeit a small amount, does not harm performance.
The study by Saunders et al. has been criticized because the investigators did not compare isocaloric beverages. There was a difference of 9 grams (36 kcals) of added protein in the CHO+P group versus the CHO group. First, the caloric different of 36 kcals cannot explain fully the significant differences in performance (i.e. the CHO+P group lasted 29-40% longer). Also, if indeed the added calories helped, then that would lead one to conclude that traditional sports drinks have inadequate energy and as such, are the not the ideal formula for consumption during exercise and post-exercise. Furthermore, in performing a product versus product study(5), it is illogical to match the beverages for calories, protein, carbohydrate, fat, and other nutrients. In the ‘real world’ of athletics, individuals consume products, they do not isocalorically match competing products to determine which is most (or least effective).
Some scientists have suggested that the addition of protein might hinder carbohydrate absorption. However, Saunders et al. found that blood glucose levels were not different between the CHO+P versus CHO group(5). Moreover, work published in the Journal of Strength and Conditioning Research (8) demonstrated that the consumption of a CHO+P beverage had similar effects on body weight immediately after exercise or after the recovery period. Changes in plasma volumes during the CHO+P and sports drink treatments were also similar. Therefore, the effects of these treatments on blood sodium, potassium, hematocrit, and hemoglobin did not differ during recovery.
Further, some commercial sports drinks have incorporated the branched-chain amino acids (i.e. valine, isoleucine, and leucine). There is evidence to suggest that consuming these amino acids may aid running performance in the marathon for “slower” runners (3.05-3.30 hours); however, there was no significant effect on the performance in the “faster” runners (less than 3.05 hours).(9)
In conclusion, consuming fluids during and post-exercise is critical for maintaining hydration status, enhancing performance, and expediting recovery. There is a growing body of evidence to suggest that adding protein/amino acids to a carbohydrate-containing beverage may enhance performance, ameliorate skeletal muscle damage, and expedite recovery. The mechanism(s) underlying this phenomenon is not clearly understood despite the fact that the clinical endpoints suggest a real difference (i.e. better performance and recovery). Certainly, there is likely going to be a paradigm shift regarding sports drinks. The traditional sports drinks (i.e. water, carbohydrate, electrolytes) may not be the best formula for athletes who wish to enhance performance and post-exercise recovery.
When you consume nutrients has a profound effect on the adaptive response to exercise. For instance, one study determined whether consumption of an oral essential amino acid-carbohydrate supplement (EAC) before exercise results in a greater anabolic response than supplementation after resistance exercise. Six healthy human subjects participated in two trials in random order, PRE (EAC consumed immediately before exercise), and POST (EAC consumed immediately after exercise). These investigators discovered that the total net phenylalanine uptake across the leg was greater (P = 0.0002) during PRE (209 +/- 42 mg) than during POST (81 +/- 19). Phenylalanine disappearance rate, an indicator of muscle protein synthesis from blood amino acids, increased after EAC consumption in both trials. Therefore, net muscle protein synthesis is higher when an EAC solution is consumed immediately before resistance exercise versus after exercise. This may be due to the increase in muscle protein synthesis as a result of increased delivery of amino acids to the leg.(10) However, inasmuch as this was an acute study, the important clinical endpoint is whether one can actually accrue more skeletal muscle mass as a result of utilizing a nutrient timing strategy.
Another study compared the effects of 14 weeks of resistance training combined with timed ingestion of isoenergetic (i.e. same total calories or energy) protein versus carbohydrate supplementation on muscle fiber hypertrophy and mechanical muscle performance. Supplementation was administered before and immediately after each training bout. On non-training days, subjects consumed their supplements in the morning. Muscle biopsy specimens were obtained from the vastus lateralis muscle and analyzed for muscle fiber cross-sectional area. After 14 weeks of resistance training, the protein group showed hypertrophy of type I (18% +/- 5%; P
From the standpoint of gaining skeletal muscle mass, it is evident that consuming carbohydrate is not necessary. However, one could posit that the addition of carbohydrate as well as insulinotropic protein (e.g. peptides, protein hydrolysates) may enhance the anabolic response. A recent investigation examined postprandial plasma insulin and glucose responses after co-ingestion of an insulinotropic protein (Pro) hydrolysate with and without additional free leucine with a single bolus of carbohydrate (Cho) in male patients with long-standing Type 2 diabetes (n = 10) and healthy controls (n = 10). The investigators concluded that the co-ingestion of a protein hydrolysate with or without additional free leucine strongly augments the insulin response after ingestion of a single bolus of carbohydrate.(11) Further work needs to determine if this can be applied to an athletic population.
Fast and Slow Proteins
Boirie et al.(12) found that a 30 gram feeding of casein protein versus whey protein had different effects on post-prandial protein gain. Both whey and casein are proteins derived from milk. In essence, they showed that whey protein is absorbed very quickly producing peak levels of amino acids at approximately 60-90 minutes after ingestion and then returning to baseline levels at approximately 3-4 hours post-ingestion. Casein on the other produced a much slower and less dramatic rise in amino acid levels peaking at approximately 60-90 minutes but maintaining higher levels of amino acids (versus baseline) over the entire 7-hr time frame.
Evidently, the differences in digestion and absorption translate into differences in protein metabolism. For instance, they discovered that whole body protein breakdown was inhibited by 34% by casein ingestion but not by whey. However, whey protein ingestion stimulated protein synthesis by 68% while casein stimulated protein synthesis to a lesser extent (+31%). However, when they looked at the ‘net leucine balance’ over the 7-hour time period after ingestion, casein ingestion resulted in a significantly higher net balance (i.e., post-feeding protein deposition was greater). Apparently, a fast absorbing protein such as whey stimulates protein synthesis tremendously but a large part of the protein is also oxidized (used as fuel). Thus, one might conclude from this single study that a single feeding of a ‘slow’ protein such as casein is superior for promoting protein accretion to a ‘fast’ protein such as whey when examined in healthy subjects over a 7-hr time frame.
However, this same laboratory followed this study with a more in-depth investigation.(13) They took four groups of 5 or 6 young men and had them consume a 30-gram protein meal. However, they were divided into four categories:
a) a single meal of slowly digested casein (CAS)
b) a single meal of free form amino acids that had the same composition as the casein (AA)
c) a single meal of rapidly digested whey protein (WP)
d) repeated small meals of whey protein mimicking the slow digestion rate seen in the casein (RPT-WP). The RPT-WP group had 13 small whey protein meals given every 20 minutes over four hours. All subjects were examined over a 7-hr period.
When they examined leucine balance (a measure of whole body anabolism), CAS was found to be superior to AA and the RPT-WP was superior to WP. And with regards to RPT-WP versus CAS, their preliminary data suggest that RPT-WP is better than CAS.
Clearly, these two studies show that the digestion rate of protein may be more important than other factors such as amino acid composition. Moreover, the amino acid composition of whey and casein are strikingly different even though both proteins contain all of the essential amino acids. For instance, in a serving of 100 grams (powder), casein contains 11.6 and 8.9 grams of glutamine and leucine, respectively. Whey contains 21.9 and 11.1 grams of glutamine and leucine, respectively. Both glutamine and leucine play critical roles in muscle protein metabolism. Thus, how amino acid composition ultimately affects muscle protein accretion is not clear (assuming that a dietary protein contains the entire complement of essential amino acids).
In addition, the second study suggests that repeated meals of whey protein may be the ‘ideal’ way to promote an anabolic state. It should be noted that the feeding pattern (13 meals every 20 minutes for four hours is not a typical of ‘real-life’ eating). However, the evidence does suggest that multiple small feedings is superior to a single bolus feeding. This is likely due to the pattern of digestion. And lastly, casein and whey proteins are treated metabolized differently with a single feeding of casein producing greater gains in protein accretion than the same sized feeding of whey.
On the other hand, a recent investigation showed no differences in the anabolic effects of whey or casein. Healthy volunteers were randomly assigned to one of three groups. Each group consumed one of three drinks: placebo (PL; N = 7), 20 g of casein (CS; N = 7), or whey proteins (WH; N = 9). Volunteers consumed the drink 1 h after the conclusion of a leg extension exercise bout. They discovered that the Ingestion of both CS and WH stimulated a significantly larger net phenylalanine uptake after resistance exercise, compared with the PL (PL -5 +/- 15 mg, CS 84 +/- 10 mg, WH 62 +/- 18 mg). Amino acid uptake relative to amount ingested was similar for both CS and WH (approximately 10-15%). Thus, the acute ingestion of both WH and CS after exercise resulted in similar increases in muscle protein net balance, resulting in net muscle protein synthesis despite different patterns of blood amino acid responses.(10)
At least from this limited data, one can reasonably conclude that casein protein as a sole protein source (versus whey) is either more anabolic or not different. What this means in a practical sense is not entirely known. However, one could speculate that if you were to consume a single protein source for gaining muscle mass, casein may be preferable over whey.
One last note regarding dietary protein; it should be noted that there is no evidence that consuming a diet high in protein has any adverse effects. (14, 15)
Caffeine is the most commonly consumed drug in the world. Caffeine may affect stimulatory receptors in the central nervous system (CNS), as well as metabolic receptors in peripheral tissues, such as skeletal muscles and may have the ability to influence psychological states and alter pain perception.(16)
One of the first studies to investigate caffeine’s effect on exercise metabolism and performance was performed by Costill et al.(17) Subjects consumed decaffeinated coffee or decaffeinated coffee with 330 mg of caffeine 60 minutes prior to exercise. Time to exhaustion was over 19% greater in the caffeine trial compared to the decaffeinated trial. Erickson et al. demonstrated that caffeine supplementation prior to exercise was found to reduce muscle glycogen utilization by 30%.(18) Spriet et al. s(19) reported a 55% decrease in muscle glycogenolysis in just the first 15 minutes of exercise during the caffeine trail.
More recent work (20) by Bell and co-workers have further substantiated the ergogenic effects of caffeine as well as how this effect can be maintained throughout the day. In this study, nine male caffeine users performed exercise rides to exhaustion at 80% VO2max after ingesting a placebo, 5 mg x kg-1 of caffeine (~398 mg of caffeine for a 175 pound individual), or 2.5 mg x kg-1 of caffeine one hour before the endurance ride. Two endurance rides were performed weekly on the same day once in the morning (AM) and five hours later in the afternoon (PM). There were four treatments:trial A representing 5-mg x kg-1 caffeine in the AM and 2.5-mg x kg-1 caffeine in the PM; trial B, which was placebo in both AM and PM; trial C representing 5-mg x kg-1 caffeine in the AM and placebo in the PM; and trial D representing a placebo in the AM and 5-mg x kg-1 caffeine in the PM. The order of the treatment trials was double blind and randomized.
Caffeine ingestion significantly increased exercise time to exhaustion in the AM by up to 14%. This effect was maintained in the PM and greater than placebo regardless of whether redosing or placebo followed the initial morning dose. Thus, it was concluded that redosing with caffeine after exhaustive exercise in the AM was not necessary to maintain the ergogenic effect during subsequent exercise 6 h later. From a practical standpoint, this shows that one can ingest caffeine in the morning and still derive benefits later in the day.
Based on the available science, it is evident that a dose of 5 mg caffeine per kg of body weight is needed to see performance effect. This ergogenic effect can be seen with endurance exercise as well as sprint performance (21)
Do caffeinated beverages affect one’s hydration status? In a paper by Armstrong et al. he reviewed the scientific literature to determine if indeed caffeine posed a problem vis a vis dehydration. It is apparent that caffeine consumption stimulates a mild diuresis similar to water; however, there is no evidence of a fluid-electrolyte imbalance that is detrimental to exercise performance or health. In fact, studies that have compared caffeine (100-680 mg) to water or placebo seldom found a statistical difference in urine volume. Additionally, tolerance to caffeine reduces the likelihood that a detrimental fluid-electrolyte imbalance will occur. Thus, the notion that caffeine might have an eroglytic effect due to diuresis is not supported by the existing data.(22)
There is robust evidence to show that regular creatine supplementation increases total muscle creatine (TCr) concentration by 20-40%, improves skeletal muscle mass, and enhances exercise performance.(23-40) The increase in stored phosphagens allows for an enhanced ability to resynthesize phosphocreatine (PCr) thus promoting an ergogenic benefit for short-duration, high-intensity activities (e.g., weight lifting, sprinting, etc). Interestingly, creatine directly influences cellular physiology by increasing the expression of Type I, IIa, and IIx MHC as well as myogenin and MRF-4 mRNA and protein (24, 25) and stimulating satellite cell proliferation.(40, 41) On the practical side, it is not clear if there is an “optimal” method of enhancing intramuscular creatine uptake. For instance, it is known that the consumption of carbohydrates with creatine may facilitate creatine uptake into skeletal muscles. However, the enormous carbohydrate load used in previously published creatine loading studies may be an impractical method of improving intramuscular creatine concentrations.(34)
In an intriguing investigation from the University of Western Australia, scientists evaluated the efficacy of 3 different creatine (Cr) loading procedures and 2 different maintenance regimes on intramuscular Cr concentrations.(42)
The three loading phases were as follows:
1. Cr ( 4 x 5 grams per day, for 5 days)
2. Cr + glucose solution (same Cr dosage; subjects consumed creatine followed by 1g glucose/kg body weight, dissolved in 500 ml water 30 minutes after the 2nd and 4th daily doses).
3. Cr + exercise (cycling exercise performed 1 hour after ingesting the second Cr dose).
The two maintenance doses studied were as follows (with a control as well):
1. 2 g Cr daily for 6 weeks
2. 5 g Cr daily for 6 weeks
3. No creatine for 6 weeks
What did they find? TCr concentrations increased significantly more in the Cr + glucose group (+25%) compared to the Cr only (+16%) and the Cr + exercise (18%) groups. There were no significant differences between the Cr only and Cr + exercise groups. Also, PCr stores were significantly elevated in the Cr + glucose (+8%), the Cr + exercise (+9%), but not the Cr only group (+5%).
After the 6-week maintenance phase, the 2g/d and 5g/d Cr dosages has similar intramuscular TCr concentrations; however, the 0g/d resulted in a significant decrement in creatine stores. Interestingly, muscle TCr stores had not returned to baseline after 6 weeks of 0g/d.
There are several interesting points about this study. First, it was surprising that exercise plus Cr did not improve intramuscular TCr over Cr alone. One could speculate that repeated sprint exercise (as used in this investigation) may have restricted gastrointestinal absorption and that perhaps exercise of a milder nature may have been more effective. Also, the improvement in TCr subsequent to carbohydrate plus creatine ingestion verifies other reports. However, the dose used in this investigation is still rather high (~773 grams of sugar total over the 5 day period; that’s over 3,000 extra calories). If maintenance of a low fat mass is critical, then the consumption of such high levels of high-glycemic sugars is not recommended. Another interesting observation is that a low daily dose of 2g Cr is sufficient to maintain high intramuscular TCr stores. To date, creatine is clearly the single most effective dietary supplement for enhancing gains in anaerobic performance as well as increasing lean body mass and muscle fiber size.
In summary, one can reasonably conclude that if you are seeking a fairly rapid improvement in anaerobic performance and lean body mass, it would be sensible to do a loading phase with creatine. However, if time is not an issue, a dose of 2-4 grams daily should be sufficient to fully saturate skeletal muscle within a month. Furthermore, the use of high-glycemic sugars to potentiate the uptake of creatine has good support in the scientific literature; however, if the maintenance of low body fat levels is a paramount concern (example: bodybuilders, strength-power athletes in the lower weight classes), then one can still supplement with creatine (minus the sugar) and still get significant elevations in total intramuscular creatine concentrations. Moreover, it should be noted that there is no evidence that regular creatine supplementation has any adverse effects. (15, 43, 44)
Athletes seek to attain the best performance possible within the confines of the rules and regulations of their sport. Certainly, there are nutritional/supplement strategies that may be effective. The consumption of a traditional sports drink is effective for rehydration and performance; however, it is possible that the provision of small amounts of protein/amino acids to such a drink may be more effective. From a timing standpoint, optimal performance and recovery may be enhanced if you consume a protein or carbohydrate-protein combination pre- and/or post-exercise. Supplements such as protein powders (e.g. whey, casein), creatine, and caffeine have been shown to have ergogenic potential as well.
Jose Antonio, Ph.D., CSCS completed his doctorate and post-doctoral research fellowship at the University of Texas Southwestern Medical Center in Dallas Texas. He is an elected member of the NSCA’s Board of Directors. For his CV, go to: www.joseantoniophd.com
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