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You are watching: Which of the following is a feature of specific ergogenic aids?

Institute of Medicine (US) Committee on Military Nutrition Research; Marriott BM, editor. Food Materials to Enhance Performance: An Evaluation of Potential Performance-Enhancing Food Components for Operational Rations. Washington (DC): National Academies Press (US); 1994.


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Food Materials to Enhance Performance: An Evaluation of Potential Performance-Enhancing Food Materials for Operational Rations.

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INTRODUCTION

For years world have actually routinely searched for ways to optimize physical performance, rise the amount of work-related that have the right to be completed under miscellaneous eco-friendly extremes, and also boost recoexceptionally from a physically exhausting job. Aids that are provided to boost physical performance or improve recoextremely from physical exertion are described as ergogenic aids. Words ergogenic is acquired from the Greek word ergon definition “work” and the sufresolve -genic interpretation “producing.” Therefore, the word ergogenic literally implies “occupational producing” or “tfinishing to increase work-related.”

Ergogenic aids are primarily classified into five categories: (1) mechanical, (2) emotional, (3) physiological, (4) pharmacological, and (5) nutritional. An example of a mechanical ergogenic help is the fiberglass pole for pole vaulting or the lightweight framework on a racing bike. A mental ergogenic assist might be hypnosis or psychological rehearsal. Blood doping or erythropoietin injections are taken into consideration powerful physiological ergogenic aids by virtue of their capacity to increase red blood cell mass and increase maximum aerobic capacity. Pharmacological ergogenic aids might be the xanthines such as caffeine or the amphetamines. Carbohydrate and protein supplements are examples of nutritional ergogenic aids. It should be listed that many type of ergogenic aids can be classified right into even more than one category. For instance, caffeine deserve to be classified as a nutritional or a pharmacological ergogenic assist. Likewise, bicarbonate can be classified as a physiological or pharmacological ergogenic assist.

Of the assorted aids recognized to have actually ergogenic results, many type of are natural foods items or derivatives of food assets. This chapter identifies some of the even more reliable food components that have actually been discovered to improve physical performance and also defines their approaches of action. Some potential yet unverified ergogenic aids are likewise debated.

Food components or food derivatives that could have actually ergogenic impacts are primarily classified as either a nutritional or a pharmacological ergogenic aid. Such aids improve performance by:

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acting as a main or peripheral nervous mechanism stimulant,

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enhancing the stored amount or availability of a limiting substprice,

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acting as a supplemental fuel source or reducing reliance on a limiting substprice during prolonged physical exertion,

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reducing or neutralizing metabolic by-products that interfere through energy-developing reactions or muscle contractivity, and

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boosting recoextremely.


Ergogenic Aids That Act as Central or Peripheral Nervous System Stimulants

Several food components or substances acquired from plant extracts have been offered to stimulate the brain, ward off feelings of exhaustion, and renew vigor and also enthusiasm. These substances might stimulate the brain straight, might increase the manufacturing or release of neurotransmitters that activate certain stimulatory regions of the brain, or prevent the release of inhibitor neurotransmitters. Instances of these neurostimulating aids are caffeine, which is uncovered in a variety of foodstuffs, and also norpseudoephedrine, which is discovered in the leaves of the African plant Catha edulis.

Recently, it was suggested that branched-chain amino acid (BCAA) supplementation might proccasion central nervous system fatigue (Blomstrand also et al., 1988, 1991). One of the hypotheses proposed to explain central nervous mechanism exhaustion is regarded a rise in the concentration of 5-hydroxytryptamine (serotonin) in one or even more specific locations of the brain. An rise in serotonin levels in the brain deserve to theoretically arise from two peripheral effects of endurance exercise. First, an increase in BCAA utilization by muscle might cause a decrease in plasma BCAA levels, which would raise the plasma tryptophan/BCAA ratio. Due to the fact that BCAAs complete with totally free tryptophan for amino acid transporters in the brain (Pardridge and Oldendorf, 1975), a boost in the tryptophan/BCAA ratio need to favor the enattempt of tryptophan right into the brain. Tryptophan is a precursor of serotonin, and also therefore, as the levels of tryptopha boost in the brain, there is a proportional boost in serotonin levels (Newsholme and Leech, 1983). Second, a rise in the plasma complimentary fatty acid concentration could contend through tryptophan for binding sites on albumin and also rise the plasma cost-free tryptophan concentration. An increase in plasma free fatty acid levels generally occurs with prolonged aerobic exercise. Whatever the circumstances, it has actually been argued that BCAA supplementation may be helpful in that it may prevent a climb in the tryptophan/BCAA proportion, thereby reducing the uptake of tryptophan by the brain and also blunting or avoiding a increase in brain serotonin levels. However, tbelow has been bit definitive research study that supports this principle.

Another feasible mechanism of activity of food components is the facilitation of excitation-contraction-coupling. This facilitating impact could occur at the neuromuscular junction by increasing the release of the neurotransmitter acetylcholine or, possibly, by staying clear of the depletion of this neurotransmitter by offering choline supplements (R.T.Wurtguy, Massachusetts Institute of Technology, personal communication, 1992). Just like BCAA supplementation, but, there has actually been no definitive research that supports this principle.


Ergogenic Aids That Increase the Stored Amount or Availability of a Limiting Substrate

Carbohydrate is a vital fuel source for extended exercise of moderate intensity. At intensities varying between 60 and also 80 percent of maximum aerobic power (maximum oxygen uptake

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), the major source of carbohydrate is muscle glycogen. Many researches have demonstrated that the capacity to exercise at exercise intensities ranging from 60 to 80 percent
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is directly related to the preexercise muscle glycogen level (Ahlborg et al., 1967; Bergström and Hultguy, 1967; Bergström et al., 1967). Since of the paramount prestige of muscle glycogen during prolonged, moderate-intensity exercise, the regulation of muscle glycogen synthesis and also mechanisms for increasing the muscle glycogen stores have been stupassed away extensively. For years it has been well-known that the intake of a high-carbohydrate diet will elevate glycogen stores above normal levels. To maximize muscle glycogen stores, however, a particular regimales of exercise and also diet have to be followed. Although several regimens have actually been developed, the 7-day protocol emerged by Sherguy et al. (1981) is the many helpful. First, the muscle glycogen level is depleted by exercise. During the following 3 days, exercise have to be of modeprice intensity and duration and also a well-well balanced combined diet created of about 45 percent carbohydprice must be consumed. Throughout the last 3 days, the exercise duration is tapered and also the carbohydprice content of the diet is increased to 70 percent. This protocol has actually been discovered to double the normal muscle glycogen concentration.

Oxygen availcapability is also a vital determinant of aerobic endurance. Increasing oxygen shipment or availability to the working muscles has actually been discovered to rise maximum aerobic power and also aerobic endurance. The boost in aerobic endurance is thneed to be because of a reduced reliance on carbohydprice stores and/or diminished lactate production during submaximal exercise. Blood doping and also erythropoietin injections have been offered to rise the oxygen-transporting capacity of the blood and also to boost by increasing the red blood cell mass (Spriet, 1991). These measures, yet, are perhaps dangerous bereason of the opportunity of infection and also boosted blood viscosity, which can location undue tension on the working out heart.

Phosphate loading, which has actually been found to boost is an alternate to blood doping and other measures that increase red blood cell mass (Cade et al., 1984; Kreider et al., 1990; Stewart et al., 1990). Typically, this procedure consists of consuming in between 600 and also 1,000 mg of sodium phosphate three to four times per day for 3 to 6 days. It has actually been reported that this procedure will boost by 6 to 12 percent, rise the anaerobic thresorganize, and boost the run time to exhaustion throughout a constant ramp protocol on the treadmill (Cade et al., 1984; Kreider et al., 1990; Stewart et al., 1990). It is thought that the boosted phosphate consumption elevates the 2,3-diphosphoglyceprice concentration of the blood and that this boosts tproblem oxygen extraction from blood by reducing the affinity of oxygen for hemoglobin (Bredle et al., 1988; Cade et al., 1984; Stewart et al., 1990). It should be discussed, yet, that other possibilities for the ergogenic results of phosphate loading have been argued (Bredle et al., 1988; Kreider et al., 1990) and that positive effects have not constantly been found (Bredle et al., 1988; Duffy and also Conlee, 1986).


Ergogenic Aids That Act as a Supplepsychological Fuel Source or Reduce Reliance on a Limiting Fuel Store

Several nutritional supplements have been supplied as a supplemental fuel resource. The the majority of popular and also probably the the majority of efficient is easy carbohydrates. Normally, these supplements are composed of glucose or a mix of maltodextrins, glucose, and fructose. The system by which carbohydprice supplements improve aerobic endurance performance may be identified by the intensity of the exercise. Throughout the onset of moderate-intensity aerobic exercise (60–75 percent ), muscle glycogen is a primary fuel source (Ahlborg et al., 1967; Bergström and Hultguy, 1967; Bergström et al., 1967). As exercise proceeds and the muscle glycogen stores decrease, the muscle becomes increasingly more dependent on blood glucose for its carbohydprice requirements (Gollnick et al., 1981). This, yet, does not appear to be a problem as long as the liver is able to maintain an adequate blood glucose concentration of roughly 3.5 mM (Coyle et al., 1986). However before, as soon as the muscle glycogen stores have been depleted and also the blood glucose concentration falls below 3.5 mM, muscle glucose uptake cannot satisfy the carbohydrate needs of the energetic muscle. Once the carbohydprice need cannot be met, muscle fatigue rapidly ensues. Carbohydrate supplements taken during the activity are able to maintain the blood glucose concentration above a vital level and prolong the time to tiredness throughout exercise of modeprice intensity (Coyle et al., 1983, 1986).

Carbohydrate supplementation has actually likewise been uncovered to be useful throughout low-intensity exercise (40–50 percent ) (Ivy et al., 1983; Yaspelkis and also Ivy, 1991). However before, the system of activity of the carbohydrate supplementation in the time of low-intensity exercise shows up to differ from that throughout moderate-intensity exercise. During low-intensity exercise, the price of muscle glycogen utilization is substantially diminished by carbohydprice supplementation (Yaspelkis and Ivy, 1991). The distinction in the muscle glycogen response elicited by a carbohydprice supplement in the time of moderate- and low-intensity steady-state exercise is most likely as a result of the distinctions in the plasma glucose and insulin responses. Ingestion of carbohydprice supplements throughout low-intensity exercise rises insulin and plasma glucose concentrations and also maintains these variables at elevated levels throughout the exercise bout (Ivy et al., 1983; Yaspelkis and Ivy, 1991). In comparison, carbohydprice supplementation during moderate-intensity exercise aids just in the maintenance of plasma glucose and also insulin concentrations (Coyle et al., 1983, 1986; Ivy et al., 1979). Recently, Yaspelkis et al., 1993) observed that carbohydprice supplementation elevated plasma glucose and also insulin levels in the time of prolonged, constant variable-intensity exercise (45–75 percent ) and also intensified aerobic endurance. The boost in plasma insulin levels was the highest possible that those investigators had observed in the time of exercise. Associated with the boost in endurance was a sparing of muscle glycogen (Yaspelkis et al., 1993). Thus, it shows up that when exercise intensity is fluctuating between low and also modeprice intensity, carbohydrate supplementation may boost aerobic endurance by reducing dependency on muscle glycogen as a fuel resource.

Anvarious other strategy to enhancing aerobic endurance is to boost the blood totally free fatty acid concentration prior to the oncollection of aerobic exercise. Raising the blood free fatty acid concentration boosts the amount of fatty acid uptake by the muscle and reduces reliance on muscle glycogen and also blood glucose for power manufacturing. This procedure has actually been uncovered to be effective in both rats and humans (Costill et al., 1977; Hickchild et al., 1977). The a lot of effective procedure for the elevation of plasma free fatty acid is to ingest a high-fat meal several hrs prior to exercise. This elevates the plasma triglyceride level. Once plasma triglycerides are elevated, heparin is injected intravenously to activate lipoprotein lipase, which hydrolyzes the triglycerides to glycerol and also cost-free fatty acids. This deserve to effectively raise the totally free fatty acid concentration in the blood to more than 1 mM. However before, this device is imvaluable and possibly dangerous bereason of the anticlotting effect of the heparin.

Since of the lipolytic result of caffeine, the usage of this xanthine to elevate plasma cost-free fatty acid levels before exercise has actually likewise been investigated. Several researches have actually found that ingestion of caffeine about 1 h before exercise increased the plasma free fatty acid concentration (Costill et al., 1978; Essig et al., 1980). This was accompanied by a decrease in the working out respiratory exadjust proportion and also an increase in aerobic endurance. However before, various other researches have discovered a boost in aerobic performance following caffeine ingestion without an increase in plasma cost-free fatty acid concentrations (Graham and also Spriet, 1991; Ivy et al., 1979; Spriet et al., 1992). For instance, Ivy et al. (1979) offered nine trained cyclists to study the results of caffeine on work-related manufacturing in the time of 2 h of isokinetic cycling exercise. Ingestion of 250 mg of caffeine 60 min prior to the ride and also ingestion of a secondary 250 mg of caffeine at 15-min intervals over the first 90 min of exercise increased work-related manufacturing by 7.4 percent without raising the subjects" perception of exertion. Of interemainder was the observation that the topics began working out at a higher job-related price from the begin of exercise and also kept a higher work rate than the controls during the course of the 2-h ride. Plasma totally free fatty acid levels in the test topics were not significantly various from those in the controls although fat oxidation, based on the respiratory exreadjust ratio, in the test subjects ended up being considerably better than those in the controls after 60 min of exercise. It was concluded that the ergogenic impact of caffeine was both neurological and metabolic in nature and also independent of an increase in plasma free fatty acid levels.

Recently, Spriet et al. (1991, 1992) performed a collection of research studies investigating the device of caffeine"s ergogenic results on running and also cycling performance at a reasonably high aerobic exercise intensity (80–85 percent ). It was found that high concentrations of caffeine ingested prior to exercise resulted in an elevation in plasma epinephrine levels and a sparing of muscle glycogen early in exercise. This spared glycogen was available late in exercise and corresponded with a lengthy time to fatigue. It was even more argued that raised utilization of intramuscular triglyceride and/or extramuscular free fatty acids after caffeine ingestion may have inhibited carbohydrate oxidation beforehand in exercise via elevations in muscle citprice and also the acetyl-coenzyme A to coenzyme A ratio (acetyl CoA/CoA-SH) ratio. Plasma totally free fatty acid levels, however, were not considerably different during the caffeine and also control therapies.

The combicountry of pyruvate and dihydroxyacetone (PD) is an additional food component that has potential as an ergogenic aid. Stanko et al. (1990a) found that usage of pyruvate and also dihydroxyacetone as part of a typical diet boosted submaximal arm endurance by 20 percent. The experimental paradigm referred to as for substituting 100 g of PD (1:3) for an isocaloric amount of carbohydprice in the diet over 7 consecutive days. Both arteriovenous glucose distinction and also blood fractional glucose extractivity were better after dietary consumption of the PD than after intake of the regulate diet, saying an intensified muscle glucose uptake. In addition, the muscle glycogen concentration was better for the PD therapy compared via that for the manage treatment prior to exercise yet did not differ between the 2 groups at exhaustion. It was argued that the better muscle glycogen stores and the increased muscle glucose uptake delayed the onset of fatigue and also extfinished the submaximal endurance capacity during the PD trial.

In a succeeding research by the very same team, the ergogenic results of PD were investigated throughout cycling at an exercise intensity of 70 percent (Stanko et al., 1990b). The experimental paradigm used was equivalent to that of their initially examine, other than that the PD and the placebo were gave individually from the meals. This led to similar muscle glycogen concentrations for the two treatment groups at the onset of exercise. Time to fatigue was 20 percent much longer for the PD therapy group compared through that for the placebo team. The whole-leg arteriovenous glucose difference was greater for the PD therapy team than for the placebo team at rest and throughout the initially 30 min of exercise, however tright here was no difference in the respiratory exadjust proportion in between the 2 groups. Tbelow was also no difference in muscle glycogen levels at the moment of exhaustion between the therapy groups. It was said that the higher glucose extractivity may have spared muscle glycogen and also that the spared muscle glycogen and/or the increased glucose extraction provided the crucial fuel for prolongation of exercise endurance capacity. A potential trouble via this supplement, however, is that pyruvate is accessible just as a sodium or a calcium salt. As such, the high concentrations of pyruvate forced for the ergogenic impact might create a mineral overfill.

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Medium-chain triglycerides (MCTs) have actually likewise been experimented through as a substitute fuel resource throughout prolonged moderate-intensity exercise. MCTs have actually been defined as a food fat that can be more quickly hydrolyzed, soaked up, and metabolized than ordinary long-chain triglycerides (Greenberger et al., 1966; Schwabe et al., 1964). Since MCTs are took in into the blood as medium-chain fatty acids (Greenberger et al., 1966) and also metabolized as conveniently as glucose (Schwabe et al., 1964), it has actually been speculated that they can provide an different carbon resource for muscle metabolism in the time of extended exercise. To date, however, tright here have been no research studies that have demonstrated an advantage to ingesting huge quantities of MCTs before or in the time of expanded aerobic exercise. In addition, tright here is a far-ranging problem with the oral management of MCTs. By themselves, MCTs are highly unpalatable and produce stomach discomfort and also diarrhea once taken in high concentrations (Ivy et al., 1980). Because of this, also if they showed up to improve aerobic endurance, their usage is questionable.