If you continue you will be starting to train endurance which will be counterproductive to developing explosive leaping power. Make writing personal training programs easy with these custom designed exercise templates, and keep your clients focused and progressing.
Pain-free clients are happy clients. Claim your free copy of the client back care guide today. Your clients will thank you for it! Link to Client Back Care Guide. All rights reserved. Search Site only in current section. Advanced Search…. If you train any of your clients at high intensity you must understand how this energy system works.
Here's a short ish explanation It has long been theorized that during the initial 10—15 seconds of exercise that creatine phosphate was solely responsible for ATP regeneration [ 6 ]. Added support for the theory of a near sole dependence on creatine phosphate during intense exercise arose because creatine phosphate is stored in the cytosol in close proximity to the sites of energy utilisation.
Phosphocreatine hydrolysis does not depend on oxygen availability, or necessitate the completion of several metabolic reactions before energy is liberated to fuel ATP regeneration.
However, as will be discussed in the section on glycolysis, a growing body of research has shown that glycolysis is rapidly activated during intense exercise, and seldom is there near complete reliance on the phosphagen system [ 20 ]. Nevertheless, the importance of phosphagen system lies in the extremely rapid rates at which it can regenerate ATP, as shown in Figure 5. Although controversy exists between physiologists over the measurements of the components of the energy systems, namely, the power, capacity, and relative contribution of each system during exercise, it has been generally accepted that with an exercise period of maximal effort of up to 5 to 6 seconds duration, the phosphagen energy system dominates in terms of the rate and proportion of total ATP regeneration [ 21 — 23 ].
Evidence suggests that when high-intensity contractions commence, the rate of CrP degradation is at its maximum but begins to decline within 1. Maximal rates of ATP regeneration from the energy systems of skeletal muscle. Adapted from Sahlin et al. During severe exercise the energy yield from the phosphagen system may continue until the stores of CrP are largely depleted see Figure 8 [ 6 , 26 ].
Thus the energetic capacity of this system is dependent on the concentration of creatine phosphate. The glycolytic pathway. Note the duplication of phase 2 3-carbon metabolite reactions to account for the 6 carbons of each metabolite from phase 1. Interestingly, most sports involve repeated bouts of intense exercise, separated by either active or passive recovery. Clearly, the rate of creatine phosphate recovery kinetics is also important to appreciate and understand the role of the phosphagen system in sports and athletics.
The ability of athletes to repeatedly recover their CrP stores and therefore produce high power outputs can have a significant effect on the outcome of their performance.
Such different rates of CrP recovery are presented in Figure 6 , and data is based on our recent and as yet unpublished observations using phosphorous magnetic resonance spectroscopy 31 P MRS. Unfortunately, limited research has been done to understand the implications of different rates of CrP recovery, or different strategies to improve such recovery [ 28 ].
Representative kinetics of creatine phosphate CrP recovery in subjects with different end exercise CrP concentrations and different proportions bias of slow or fast twitch muscle. Based on unpublished research observations of the authors.
It is important to understand the research methodology of 31 P MRS, as since its introduction in the s it has become the main method used to study the phosphagen system during and in recovery from exercise. Many research journals have also stated specific intentions to invite and publish more research based on 31 P MRS methodology. Research using 31 P MRS requires the use of a large bore magnet within which is a peripheral coil that is electronically tuned to the atomic signal frequency of the atom of interest.
For example, when placed in a magnetic field, most atoms with a negative number of electrons will be forced to alter their alignment when subjected to a short burst of high-frequency energy. Once the pulse of energy is over, the atoms release their specific frequency of energy for the given magnetic field as they return to their stable state.
This data collection occurs over several milliseconds, and the resulting data is referred to as a free induction decay FID. It is this signal that is collected in all forms of magnetic resonance imaging and spectroscopy. For spectroscopy, the FID is mathematically processed by a procedure known as Fourier transformation, which essentially converts the data from numbers expressed over time, to numbers expressed relative to the frequency of change of the data.
This processing produces a spectrum, where the curves, or peaks, represent the relative abundance of specific frequencies of change Figure 7. For 31 P MRS, the larger the area under these curves, the greater the concentration of the phosphorous containing metabolite to which they represent.
The muscle pH of each condition is 7. There are 5 signal peaks typically resolved, depending on the strength of the magnetic field and the extent of sample collection and averaging. The higher the magnetic field the stronger the signal and the higher the frequency of this signal for any given metabolite. Due to the magnetic field strength specificity of the signal frequency for a given atom, this frequency is corrected for the field strength, resulting in the common ppm x -axis unit of the MRS spectrum.
This allows data from different magnets to be compared to one another. Note that the frequency of signal for each phosphorous atom is slightly different for different molecules due to the influence of the local atomic environment of the phosphorous atom.
Hence, the signal from the phosphorous of ATP is slightly different for each of the three phosphorous atoms of the three phosphate groups, which is different again from CrP, and different again from free inorganic phosphate Pi. As well as the rate of CrP recovery it is also important to consider the nature of the recovery process. Evidence from previous studies which have looked at the nature of CrP resynthesis points towards CrP resynthesis having a biphasic recovery pattern following intense muscular contraction [ 10 , 29 ].
It seems that there is an initial fast phase immediately after exercise followed by a slower secondary recovery phase. Harris et al. Also in support of the biphasic recovery of CrP, Bogdanis et al.
After 1. More recently Forbes et al. They found that in the majority of humans there was indeed an initial fast recovery component in skeletal muscle following intense exercise. Nevertheless the evidence for the biphasic nature of CrP recovery is not conclusive. Although it seems unlikely that after intense exercise the model of recovery will follow a monoexponential pattern, it could be that a biphasic model may not be adequate to describe the resynthesis pattern.
Advances in technology e. This suggests that there could be more than 2 distinct phases in the CrP recovery process. There is conflicting evidence in the literature over the importance of oxygen during the resynthesis of CrP following high-intensity exercise. A number of studies have looked at recovery of muscle following high intensity exercise under ischaemic conditions.
Sahlin and colleagues [ 25 ] and Harris and his coworkers [ 30 ] have found these conditions to substantially suppress the resynthesis of CrP. This therefore suggests that CrP resynthesis is reliant on oxidative metabolism [ 30 , 33 , 34 ]. However, Crowther and colleagues [ 35 ] found that following high-intensity exercise under ischaemic conditions, glycolytic flux remained elevated for a short period of time; it remained high for 3 seconds and had decreased to baseline levels within 20 seconds.
If this was the case and glycolytic ATP production was making a considerable contribution to energy supply during the recovery phase, then an initial fast phase of CrP recovery would be expected immediately following the cessation of high-intensity exercise. This ties in with the work discussed previously. Work done by Forbes et al.
If CrP is only partially restored during the recovery phase, this can lead to a compromised performance in subsequent exercise bouts, for example, a decrease in power output. When exercise continues longer than for a few seconds, the energy to regenerate ATP is increasingly derived from blood glucose and muscle glycogen stores [ 36 ].
This near immediate activation of carbohydrate oxidation after the onset of exercise [ 37 ] is caused by the production of AMP, the increases in intramuscular free calcium and inorganic phosphate both increase the rate of the phosphorylase reaction as calcium is an activator of phosphorylate and inorganic phosphate is a substrate , and the near spontaneous increase in blood glucose uptake into muscle caused by muscle contraction.
The increased rate of glucosephosphate G 6 P production from glycogenolysis and increased glucose uptake provides a rapid source of fuel for a sequence of 8 additional reactions that degrades G 6 P to pyruvate. This sequence of reactions, or pathway, is called glycolysis Figure 8. Glycolysis involves several more reactions than any component of the phosphagen system, slightly decreasing the maximal rate of ATP regeneration Figure 5.
Nevertheless, glycolysis remains a very rapid means to regenerate ATP compared with mitochondrial respiration [ 22 ]. It is convenient to separate glycolysis into two phases. Phase 1 involves six carbon phosphorylated carbohydrate intermediates called hexose phosphates. Phase 1 is also ATP costly, with ATP providing the terminal phosphate in each of the hexokinase and phosphofrucktokinase reactions.
Phase 1 is best interpreted to prepare for phase 2, where ATP regeneration occurs at a higher capacity than the cost of phase 1, resulting in net glycolytic ATP yield.
Phase 2 is the ATP regenerating phase of glycolysis. Each reaction of phase 2 is also repeated twice for a given rate of substrate flux through phase 1, as phase 2 involves 3 carbon phosphorylated intermediates, or triose phosphates. Such a doubling of reactions is caused by the splitting of fructose-1,6-bisphosphate into dihydroxyacetone phosphate and glyceraldehydephosphate.
Triosephosphate isomerase catalyses the conversion of dihydroxyacetone phosphate to glyceraldehydephosphate. Consequently, 2 molecules of glyceraldehydephosphate are now available for phase 2 of glycolysis, thereby allowing the doubling of each subsequent reaction when accounting for substrate flux and total carbons. It is important to note the role of inorganic phosphate as a substrate in the glyceraldehydephosphate dehydrogenase reaction.
This is a very exergonic reaction, allowing free inorganic phosphate to bind to glyceraldehydephosphate, forming 1,3-bisphosphoglycerate. It is this reaction that effectively allows for glycolysis to be net ATP regenerating as it provides the added phosphate group necessary to support additional phosphate transfer to ADP to form ATP in subsequent reactions. The two reactions that regenerate ATP in glycolysis are the phosphoglycerate kinase and pyruvate kinase reactions, resulting in 4 ATP from phase 2.
Close inspection of Figure 8 reveals that there is an added immediate ATP benefit from commencing glycolysis from glycogen versus glucose. However, this is normally done in the resting and postprandial state well before exercise commences.
Traditionally within exercise science it was thought that CrP was the sole fuel used at the initiation of contraction, with glycogenolysis occurring at the onset of CrP depletion.
However, we have learned from a variety of research studies that ATP resynthesis from glycolysis during 30 seconds of maximal exercise begins to occur almost immediately at the onset of performance [ 20 , 38 ].
Also, unlike CrP hydrolysis which has a near instantaneous maximal rate of catalysis, ATP production from glycolysis does not reach its maximal rate of regeneration until after about 10 to 15 seconds of exercise and is maintained at a high rate for several more seconds. Over a period of second of exercise the contribution from glycolysis to ATP turnover is nearly double that of CrP [ 39 — 42 ] Figure 9.
Energy system interaction and the differences in rates of ATP turnover during short term intense exercise to fatigue. The data presented is original, theoretical, and based on the authors' assessment of contemporary research evidence.
Carbohydrate is the only nutrient whose stored energy can be used to generate ATP via glycolysis. When carbohydrate in the form of glucose or glycogen is catabolised during high-intensity performance only a partial breakdown or oxidation occurs, compared to the complete oxidation when reliant on mitochondrial respiration [ 46 ]. This is because pyruvate production occurs at rates that exceed the capacity of the mitochondria to take up pyruvate.
To prevent product inhibition of glycolysis and a reduction in the rate of glycolytic ATP regeneration, as much pyruvate as possible must be removed from the cytosol. While some pyruvate is transported out of contracting muscle fibers, most is converted to lactate via the lactate dehydrogenase reaction see 3 and Figure The lactate dehydrogenase reaction.
Note the use of the proton to complete the reduction of pyruvate to lactate. Furthermore, the metabolic proton buffering provided by lactate production is largely pH independent. The production of lactate during exercise was discovered in the early 19th century by Berzelitus, who found the muscles of hunted stags to have elevated levels of lactic acid [ 47 ].
However it was not until the beginning of the 20th century that the biochemistry of energy metabolism began to be better understood [ 48 ]. This led to a number of studies which indicated that lactate was a dead-end waste product of glycolysis [ 49 , 50 ] and a major cause of muscle fatigue [ 51 ]. However around the s this view began to be challenged [ 52 ], and it has now been shown that lactate is in fact beneficial during intense exercise [ 45 , 53 ].
This reaction, in being a dehydrogenase reaction, is also an oxidation:reduction reaction. Herein is a tremendously important function of lactate production.
An added benefit of lactate production concerns the metabolic proton buffering. The lactate dehydrogenase reaction uses two electrons and one proton from NADH and a second proton from solution to reduce pyruvate to lactate.
As such, lactate production retards, not causes, the development of metabolic acidosis. It is fair to state that we could not sustain high-intensity exercise for much longer than 10 to 15 seconds without lactate production.
As will be shown, this presentation is also beneficial for revealing the source of proton release during intense exercise. Figure 11 presents the net substrates and products of glycolysis, and how lactate production and the ATP hydrolysis supporting cell work are involved in the cycling of substrates and products as well as the net release of protons.
To develop this energy system, sessions of 4 to 8 seconds of high-intensity work at near peak velocity are required e. The length of recovery between repetitions is vital in recovering power output through CP's resynthesis.
A study by Holmyard et al. Once the CP stores are depleted the body resorts to stored glucose for ATP, the breakdown of glucose or glycogen in anaerobic conditions results in lactate and hydrogen ions production. The accumulation of hydrogen ions is the limiting factor causing fatigue in metres to metres. Each of these units can be developed as follows:. Anaerobic Capacity refers to the body's ability to regenerate ATP using the glycolytic system and Anaerobic Power refers to the body's ability to regenerate ATP using the phosphagen system.
These energy systems can be developed with appropriate interval training sessions. Glycolytic - the breakdown of glucose by enzymes into pyruvic and lactic acids with the release of energy ATP. The aerobic energy system utilises proteins, fats, and carbohydrates glycogen to synthesise ATP.
This energy system can be developed with various intensity Tempo runs. Although all energy systems turn on at the same time, the recruitment of an alternative system occurs when the current energy system is almost depleted.
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