Sports Fitness Training

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Caffeine is perhaps the most extensively researched endurance ergogenic aid. By stimulating the central nervous system, caffeine can enhance the release of catecholamines (epinephrine and norepinephrine) and increase the use of fatty acids for energy. Research has shown an increase in fat oxidation and free fatty acid concentrations with the use of caffeine, therefore sparing muscle glycogen. Also, plasma epinephrine concentrations have been shown to be elevated with the ingestion of caffeine. 124 A third way in which caffeine may increase performance is by decreasing an individual’s rate of perceived exertion at a given work­add. The combination of these three factors can significantly increase an individual’s endurance performance. Some studies have shown no improvements in performance with the use of caffeine, but most studies have shown positive results.As a conditionally essential amino acid, carnitine is a physiological carrier of activated longchain fatty acids. Carnitine aids in the transport of these fatty acids into the mitochondria for oxidation. It is the oxidation of fatty acids that supplies the body with energy. The use of fatty acids for energy will spare muscle glycogen. This is why carnitine has been proposed as an ergogenic aid for endurance performance. Nonetheless, studies have not been able to show an improvement in endurance performance with the use of carnitine.

As a metabolite of leucine, HMB is normally used as a muscle-building supplement. The mechanism by which HMB may influence skeletal muscle growth or enhance endurance performance is unknown. Currently, no studies have been conducted on HMB and its influence on endurance, however, one study showed no increase in creatine phosphokinase activity and a decrease in LDH activity after a prolonged run with HMB supplementation. These changes suggest that HMB may help ameliorate skeletal muscle damage after exercise. HMB may help increase performance because it can decrease muscle damage, but more studies are needed.

CoQ10 aids in the transport of electrons within the mitochondria and aids in the production of ATP Studies have shown that the ingestion CoQ10 significantly increases serum concentrations of CoQ10, nevertheless, these studies did not show any improvements in endurance performance. In fact, one study showed that the use of CoQ10 actually decreased performance, and another study by the same investigator showed that CoQ10 might cause some cell damage

Dimethylglycine (DMG) has also been touted as an endurance enhancer by increasing oxygen use and mental alertness. A couple of studies have shown improvements in performance with DMG, however, these studies were highly criticized for various reasons such as not having blinding for either the subjects or the investigators. Most of the more recent studies on DMG have not shown positive results. The basis by which DMG supposedly works has little merit.

The herbal supplement, ginseng, is widely used to enhance performance and aid in various health-related issues. Early studies conducted on ginseng and its effect on endurance in mice showed positive results. These studies showed an increase in performance time, swim time, capillary density, and mitochondrial content with ginseng supplementation. At least one human study has also shown an improvement in endurance performance with ginseng nonetheless, the bulk of human data on ginseng have not shown an improvement in endurance.

On the other hand, the use of pyruvate on endurance performance has shown some encouraging results. When pyruvate is ingested, it will apparently enhance the efficiency of the Krebs cycle, thereby producing more ATP for energy. Although many studies have been performed on pyruvate’s effect on weight loss, few have been conducted on its effectiveness in endurance performance. Two of the studies conducted on pyruvate have shown that it can aid in performance, then again, these studies used 25 g of pyruvate combined with 75 g of dihydroxyacetone. To ingest this extremely high dose, you would be consuming more capsules than the average individual would care to. Also, the most recent study on low doses of pyruvate (7 g) showed no improvement in endurance performance. Moreover, the use of pyruvate has resulted in some mild side effects including flatus and diarrhea.

Polylactate has been shown to increase blood pH, thereby allowing a greater lactic acid buildup before fatigue. The few studies that have been conducted on polylactate have not shown an increase in endurance performance. Also, individuals ingesting polylactate at a concentration greater than 2.5% had severe gastrointestinal efflux. The sparse data available do not show much hope for this supplement.

Phosphates are a blood buffer that might also increase the production of 2,3 DPG, thereby increasing the amount of oxygen delivered to skeletal muscles. The research conducted on phosphates is mixed, with slightly more data showing an increase in endurance performance with phosphates. Thus far, studies have not shown any toxic side effects of phosphates, but few studies have tested for them.

Another blood buffer, sodium bicarbonate, has also had mixed results. The data are basically split with approximately half of the studies showing an improvement in performance, while the other half showed no improvement. Also, sodium bicarbonate has been known to cause severe gastrointestinal discomfort depending on the individual.

Many studies have been conducted on the use of medium-chain triglycerides (MCTs) and their effects on endurance performance. MCTs are oxidized as easily as glucose, and therefore they may have a glucose­s paring effect. Out of the numerous studies conducted on MCT, only one has shown an increase in endurance performance. Also, most of these studies have shown an increase in ketone bodies, and some gastrointestinal problems have also resulted.

Moreover, glycerol concentrations in the blood may be a reflection of an athlete’s performance. Therefore, it would be feasible that ingesting exogenous glycerol may help increase performance. Nevertheless, of the few animal and human studies conducted on glycerol and performance, none have shown an increase in performance, and some have shown a significant decrease in performance.

Finally, the most likely and frequently used supplement in endurance athletics is carbohydrates. Numerous studies support an ergogenic role of carbohydrates under the proper conditions. Carbohydrates are readily broken down into glucose and used for energy, therefore, ingestion of extra carbohydrates before and/or during exercise should increase endurance performance.

Casein represents a class of phosphoproteins (a, ß, K,y ) derived from bovine milk. Food scientists consider bovine casein as the fraction of milk that precipitates from raw milk at a pH of 4.6 and 200C. However, some whey protein may also precipitate under these same conditions, thereby contaminating the casein with lactalbumin and lactoferrin. Casein comprises 82% of the protein fraction of milk, compared to 18% for whey. Casein is commercially available primarily as sodium caseinate, potassium caseinate, and calcium caseinate and is used in the production of infant formulas, dried skim milk, and protein powders. It is considered a high-quality protein capable of increasing amino acid levels in man as well as improving protein metabolism.

Animal Studies

Studies in animals have examined the effects of casein on liver protein synthesis and fractional synthesis rates of whole-body proteins. The effects of casein and lactalbumin on radiolabeled leucine incorporation into the liver protein of Sprague-Dawley rats were compared. More Cleucine was incorporated into the liver of rats from the casein group, indicating higher rates of liver protein synthesis. Curiously, the wet weight and total protein content of the liver was lower for the casein group than the lactalbumin group. These contradictory effects were thought to result from increased liver catabolism or an increased secretion rate of liver proteins into circulation. The casein­induced increase in liver protein synthesis may be an advantage during times of infection or illness by allowing the liver to regenerate at a higher rate.

Insulin-like growth factor-1/somatomedin C (IGF-1) is a peptide hormone produced primarily by the liver. In addition, it is also a potent stimulator of protein synthesis. Male Wistar rats fed diets differing only in protein content had significantly higher levels of IGF-1 on a casein diet compared with rats fed gluten- or protein-free diets. Casein has also been shown to increase levels of IGF-1 when infused into pregnant ewes and steers and affect IGF-1 receptor levels of various tissues in rats. The casein-fed rats also had significantly greater rates of whole-body protein synthesis. These results lend some support to the previously discussed findings of James and Treloar that showed greater levels of liver protein synthesis with reduced liver weights in rats. Previous work has also shown that casein can stimulate the hepatic content of mRNA species of IGF-1 By stimulating the liver to

produce IGF-1, casein may exert an indirect effect on protein synthesis.

Casein may also affect IGF-1 levels by increasing IGF-1 absorption from the gastrointestinal tract. The survival profiles of a bolus of 1-labelled IGF-1 (8.6 ng) in vivo in various ligated gut segments of fasted adult rats was investigated. IGF-1 administered orally is rapidly proteolyzed and loses its bioactivity. However, when administered with casein, IGF-1 structural integrity and receptor binding activity in both stomach and duodenum fluids were maintained. IGF-1 uptake via endocytosis by enterocytes may allow the safe transport of unaltered IGF-1 into the blood. Casein has a slow gastric emptying rate and long gastrointestinal transit time, and therefore may allow enterocytes to endocytized IGF-1.

Casein may modulate IGF-1 levels by three separate pathways by increasing

(a) Amino acid availability and therefore modulating skeletal muscle protein synthesis and accretion through an autocrine or paracrine IGF-1 influence

(b) Absorption of IGF-1 from the GI tract

(c) Liver production of IGF_1

There are some problems with directly applying these data. The research on animals using casein infusions is based on the introduction of undegraded proteins into the GI tracts of these animals. Normally, these proteins would have undergone hydrolysis and the positive effects on IGF-1 may be lost. However, oral feeding studies on rats do demonstrate that casein can exert positive effects on IGF-1 levels. But the positive effects of casein on IGF-1 do not steadily increase. l96 Initially, casein administration increases plasma and muscle levels of IGF-1, but levels return back to baseline after 14 days. Another important point to consider is that these studies have all compared casein (an animal protein) with either a plant protein or a protein-free diet. The effects of casein on IGF-1 may also be due to the presence of additional EAAs. Future research comparing casein. whey, specific milk protein isolates, and their combinations is needed to elucidate the specific mechanisms involved. The presence of other bioactive fractions in casein may also indicate that either the individual fractions themselves or some combination mediate the indirect effects of casein on protein synthesis.

Human Studies

The effects of amino acid mixtures simulating casein and hydrolysates of casein on absorption after oral or jejunal administration. This work supports similar work done on whey protein, indicating that hydrolysates are absorbed better than their amino acid counterparts. Additional work examined the effects of casein on postprandial amino acid responses and on insulin and glucagon. The most recent research on casein focused on the delayed gastric emptying time and impact on protein synthesis

Research on healthy men and women agrees with research on animals that casein has a slow gastric emptying time. This delay results in elevated plasma amino acid concentrations up to 300 minutes postingestion. The significance of this effect is exemplified by marked differences in protein metabolism compared with whey. Casein protein ingestion results in a slight increase in protein synthesis, moderate increase in protein oxidation, and large decrease in protein breakdown. This profile results in a more positive protein balance compared with whey. This effect may be lost if casein oligopeptides are given in place of whole casein protein.

Safety and Toxicity

Casein, like any protein, has the potential to induce allergic reactions in some individuals. This is more of a concern for infants receiving formulas than adults. A more practical concern for adults is the potential hypercholesterolemic effects of casein and data from animal studies on the potential carcinogenic effects of cooked or heated casein So, individuals with hypercholesterolemia or those consuming high saturated fat diets should use casein products cautiously. Long­term research demonstrates similar side effects in rats fed semipurified diets containing either casein or soy proteins.

However, a recent study demonstrated that a casein protein diet produced a dramatic drop in Lp(a) levels, thus potentially decreasing cardiovascular risk. Also, if casein has deleterious effects on blood lipids and tumor formation, then one would speculate that heavy milk drinkers would suffer from a malady of health problems. Clearly, this is not the case.

No evidence based on properly conducted, rigorous scientific study suggests that the use of amino acid supplements in conjunction with strength-training increases muscle growth or lean body mass to a greater extent than strength training alone. Two studies that reported greater increases in body mass and reduction in percent body fat, and gains in total body strength, lean body mass, and reduced urinary hydroxyproline excretion as a result of arginine and ornithine supplementation were seriously flawed. In these studies, untrained adult males (mean ages, 38.3 and 37.2 yrs, respectively) trained 3 days per week for 5 weeks. Body composition was assessed using skinfolds and body girths, but not hydrostatic weighing. Subjects in the experimental groups ingested 500 mg each of arginine and ornithine twice daily. In the first study, the statistical procedure used in data analysis was reported as an analysis of variance (ANOVA) using a 2 X 3 factorial design. However, data in the paper were given as absolute change for body mass, percent body fat, and body girths. It appears that each of the dependent variables measured was used within the same ANOVA, thus the “3″ in the 2 X 3 statistical analysis. This is clearly an inappropriate statistical analysis. Furthermore, t-tests of the data shown in the paper show no difference for body mass, percent body fat, and the sum of body girth measurements between placebo and amino acid-supplemented groups. In the second study, only the data collected after 5 weeks of training were used in the analysis. The authors reported using a two-way ANOVA with group (amino acid or placebo) and the dependent variables (strength, lean body mass, hydroxyproline excretion) used in the analysis. Again, this is an incorrect statistical procedure. Although it was suggested that the effects of amino acid supplementation could have been due to the effects of arginine and ornithine on GH, the conclusion is not supported by the data. Again, there are no properly designed studies demonstrating greater gains in strength or lean body mass in individuals using specific amino acids as GH secretagogues in conjunction with strength training.

In the athlete, it appears that the most promising characteristic of antioxidant supplementation regarding performance is the ability to aid recovery As athletes know, recovery after exercise is vitally important to improved performance. Eccentric contractions (i.e., “negatives”) are a necessary part of many types of sport and result in exaggerated myofibrillar disruption, delayed-onset muscle soreness, inflammation, and reduced force generation. Thus, decreasing muscle damage and inflammation (and/ or hastening a return to “healthy” status) can allow an athlete to resume training and more rapidly improve in ability The response to muscle damage can last several days and is hallmarked by increased muscle enzyme release, urinary nitrogen excretion, increased metabolic rate, and increased cortisol and interleukin concentrations. Subjects also experience decreased glucose tolerance and strength after eccentric exercise This period of eccentric recovery is in stark contrast to the shorter, less traumatic 24-48 hour recovery period observed after less-damaging concentric exercise. As mentioned earlier, circulating leukocytes (white blood cells) infiltrate traumatized muscle tissue and, in concert with cortisol, prostaglandins, and various cytokines, they induce catabolism, edema, pain, and inflammation. Although this immune response is primarily beneficial, the period of catabolism may be unnecessarily aggressive before growth factors are secreted and tissue growth and/or repair begins.Think of this scenario as equivalent to a group of janitors arriving to clean up a mess. But, in addition to cleaning up the original mess, these janitors (neutrophils and monocytes) also tend to tear down the walls as they clean. Antioxidant vitamins like vitamin E and vitamin C may combat this aggressive cleaning strategy of the janitors (part of the acute-phase response) both by buffering the reactive oxygen species that are released and by suppressing cell membrane peroxidation and prostaglandin formation, which is partly responsible for the inflammation. The next logical question would be, Why would anyone punish themselves with eccentric contractions to the point of requiring pharmacologic doses of vitamins The logic behind using repeated, high-intensity eccentric contractions involves the growth response. Because the muscle hypertrophic response is greater, athletes requiring gains in muscular size and/or strength often use negative training using resistance exercises and/ or plyometrics. As we have seen, this can aggravate oxidant insult, inducing damage that might only be treated optimally with antioxidant supplementation

It is well known that intense or prolonged exercise results in oxidative injury to skeletal muscles, particularly in untrained individuals. Further, there is growing evidence that radicals and other reactive oxygen species contribute to muscular fatigue. Therefore, it is not surprising that there is strong interest in the effects of antioxidant supplements on exercise performance. Numerous animal studies have examined the effects of antioxidants on muscular performance. Many of these experiments have used in vitro preparations in which antioxidants were added to the bathing medium surrounding the muscle. In general, these in vitro experiments indicate that the addition of antioxidants results in delayed muscular fatigue. Some in vivo animal studies also indicate that the addition of antioxidants can improve muscular performance. Collectively, these experiments suggest that antioxidant supplementation can improve muscular performance by reducing exercise-induced oxidative stress. Nonetheless, most animal studies have used antioxidant treatments that cannot be used in humans. Therefore, results from antioxidant research using animal models cannot always be directly extrapolated to humans.Research examining the effects of antioxidant supplementation on human performance is in its infancy. At present, limited studies have examined the effects of antioxidant supplementation on muscular endurance in humans. Further, many of the studies suffer experimental design weaknesses and most studies have investigated the effects of a single antioxidant rather than investigating the combined effects of both lipid and water-soluble antioxidants. By far, the most widely studied antioxidant vitamin is vitamin E, whereas few studies have examined the effects of other antioxidants on human performance. Although several human studies have indicated that supplementation with vitamin E and/or vitamin C reduce exercise-induced oxidative stress, there is limited evidence that antioxidant supplementation can improve human performance. However, because of the paucity of research on this topic, many additional studies are required before a firm conclusion can be reached about the effects of antioxidant treatment on human exercise tolerance.

Future studies should examine the potential synergistic effects of several antioxidants on human performance. Further, additional experiments are required to explore the bioavailability of nutritional antioxidants provided in tablet form compared to the bioavailability of these nutrients derived from whole food. This is an interesting area for future research.

The phenomenon of overreaching and overtraining is not new to sport. Athletes involved in intense training often experience short-term and/or long-term decrements in performance. In fact, coaches and athletes often plan intensified periods of training in hopes that the training will promote greater training adaptations. Unfortunately, while some athletes respond well to the intensified training, others may become overreached and/or over­trained. According to Kreider, overreaching is an accumulation of training and/or nontraining stress resulting in a short-term decrement in performance capacity with or without related physiological and psychological signs and symptoms of overtraining in which restoration of performance capacity may take from several days to several weeks. More severely, overtraining is an accumulation of training and/or non training stress resulting in a long­term decrement in performance capacity with or without related physiological and psychological signs and symptoms of overtraining in which restoration of performance capacity may take several weeks or months.Although the specific etiology of overtraining is unclear, there are basically two types of overtraining described in the literature-sympathetic and parasympathetic . Sympathetic overtraining is typically associated with anaerobic strength-power training whereas parasympathetic overtraining is usually associated with endurance exercise training. In sympathetic-type over­training, performance is decreased and response to training stimulus is delayed. Athletes may also exhibit signs/ symptoms of increased irritability; disturbed patterns of sleep, weight loss, increased resting heart rate and blood pressure, and/or impaired recovery during training. In parasympathetic-type overtraining, performance capacity is decreased and response to training is also delayed with decreases in heart rate, blood pressure, and suppressed neuromuscular excitability. Other factors that can result in a decrease in performance are fatigue, depression, and altered endocrine function.

Although some overreached/overtrained athletes experience a decrease in performance without any signs/symptoms of overtraining, most will exhibit some of these overt signs. However, there does not appear to be any consistent pattern of symptoms of overtraining among athletes. Therefore, although some markers have been proposed, there are presently no valid markers of overreaching and overtraining other than reductions in exercise capacity.

Several factors have been suggested to increase the susceptibility of athletes to become overtrained. Care should be taken to plan training carefully so that the athletes are progressing properly from various training phases to avoid sudden increases in training volume and/or intensity. Care should also be taken to ensure that there is enough recovery time during training to optimize physiological adaptations. Additionally, one must consider that the athlete not only must endure the physical stress of training but that the psychological stress of competition, school, work, social environment, or personal life may add to the physical stress of training. 6 Coaches and trainers should be aware of these psychological stressors and alter training volume and intensity as necessary.

It is also clear that during periods of increased physical or psychological stress, athletes often do not eat enough calories to offset energy expenditure. The result is that the athlete maintains a negative energy status that may further compromise training adaptations. Consequently, coaches and trainers should ensure that the athlete is well-fed during periods of intensified training. Finally, it is recommended that coaches and athletes closely monitor signs and symptoms of overtraining during training. Research has indicated that some psychological signs (e.g., general fatigue, lethargy, disinterest in training, etc.) may often precede physiological symptoms of overreaching/ overtraining. Therefore, simply monitoring how athletes feel, how they perceive they are responding to training, and performance markers can serve as valuable feedback in understanding how athletes are tolerating training so that training volumelintensity can be altered accordingly.

Compared with prolonged endurance activity, much less has been researched and written regarding the influence of carbohydrate intake on high-intensity sporting events. The authors define high-intensity events, also termed strength/power sports, as exercise requiring high power or force output. This includes events in which power output leads to muscular fatigue in a few minutes of activity or less, and exercise that requires repetitive, high-force production from specific muscles. High-intensity exercise, therefore, cannot be sustained for extended periods of time, and frequent or prolonged rest periods are required. Fortunately for strength/power athletes, rest periods are usually included in such sports, owing to the depletion of energy substrates (i.e., phosphocreatine, glycogen) and accumulation of metabolic products (i.e., lactate, ammonia).Although the performance benefits of carbohydrate ingestion are well documented in endurance athletes, strength and power athletes must also be aware of this macronutrient’s potential ergogenic effects. Whereas glycogen use is insignificant during brief anaerobic events (i.e., Olympic weightlifting), in situations that call on athletes to perform repeated anaerobic exercise bouts (i.e., repetitive sprints, basketball, football), proper carbohydrate ingestion becomes increasingly significant. Too often, adequate carbohydrate intake is overlooked and the resulting glycogen debt becomes the culprit when premature fatigue surfaces in strength/power sports. In contrast, the energy attained via glycogen use in many prolonged low-intensity endurance sports (i.e., marathon running) is aided by the oxidation of fats. However, in the case of such anaerobic sports as basketball and ice hockey, the repetitive nature (and correspondingly high-glycogen use) does not physiologically allow for surplus energy production from fats. Thus, the ample glycogen availability demanded by these sports necessitates an augmented carbohydrate intake. Certainly, the carbohydrate requirements for high­intensity sports are not as great as those for endurance events, although some studies have noted the ability to maintain higher training intensities when greater than normal intakes were consumed. However, as the intensity of the event increases (and thus the duration decreases), higher than normal glycogen concentrations do not appear to offer any additional benefits. Therefore, a supplemental carbohydrate intake is most advantageous for those athletes involved in repetitive high-intensity events or training regimens of a similar nature. As an example, ice-hockey players who consumed a carbohydrate supplement (360 g/day for 3 days) in addition to their normal diet before a competition possessed muscle glycogen levels that were twice as high as those in players who were not given the supplement. It may also be important for similar athletes to ingest a high­carbohydrate diet during periods of intense training. events or training regimens of a similar nature. As an example, ice-hockey players who consumed a carbohydrate supplement (360 g/day for 3 days) in addition to their normal diet before a competition possessed muscle glycogen levels that were twice as high as those in players who were not given the supplement. It may also be important for similar athletes to ingest a high­carbohydrate diet during periods of intense training. events or training regimens of a similar nature. As an example, ice-hockey players who consumed a carbohydrate supplement (360 g/day for 3 days) in addition to their normal diet before a competition possessed muscle glycogen levels that were twice as high as those in players who were not given the supplement. It may also be important for similar athletes to ingest a high­carbohydrate diet during periods of intense training.

It is well understood by the athletic community that increased carbohydrate intake (loading) can significantly enhance exercise performance in situations in which muscle glycogen stores are limiting. Less well known, but of critical importance is that there is a brief window of opportunity perhaps 60 minutes or so following exercise in which the muscle glycogen synthetic rate is significantly greater than at any other time during the day. Similarly, it is becoming clear that strength exercise causes disruptions in both muscle protein synthesis and degradation, resulting over time in substantial muscle growth. Perhaps, nutrient supplementation post­exercise might optimize muscle growth. For example, this overall growth response could be limited by energy and/or amino acid availability. If so, providing either or both could enhance muscle growth/repair via increasing protein synthesis or decreasing protein degradation. Some evidence Combining carbohydrate and amino acids may be the best approach because the insulin released in response to the carbohydrate stimulates amino acid uptake by muscle, leading, at least potentially, to enhanced protein synthetic rates . As mentioned above, some amino acids are also powerful stimulators of insulin release. Moreover, other hormones important for positive training adaptations could be involved. It appears that the essential amino acids are the most crit­ical and that only small amounts may be necessary. As further study clarifies the details of the effects of strength training on net protein balance in muscle it should become possible to prescribe precise recommendations regarding type, amounts, and timing of nutrient supplementation to maximize the anabolic stimulus following strength training. If so, this information would be of considerable benefit not only to the athletic community but also to any group of individuals who have lost muscle function due to disease or disuse (i.e., post-surgery, injuries, elderly, zero-gravity environment, etc.).