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Physiological Adaptations to Anaerobic _ Aerobic Training

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					Physiological Adaptations to Anaerobic & Aerobic Training
University of Massachusetts Boston Strength & Conditioning Timothy Morgan, D.C.

Biological Energy Systems
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ATP (Adenosine Triphosphate) – ultimate molecular source for muscular contraction and human function; used at the site of Actin-Myosin crossbridging to create muscular contraction and force production Molecular breakdown of ATP ATP ADP + P (plus energy release) This Energy release is used by the muscle to allow crossbridging and contraction ATP must be constantly, and instantaneously replenished or re-synthesized in order for any biological function to continue (i.e. muscular ATP contraction) ATP can be synthesized or re-synthesized through several biochemical pathways (Creatine Phosphate, Glycolysis & Oxidative Systems

ATP Production – Energy Systems
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CP (Creatine Phosphate) – Provides ATP for short
term, high-intensity activities (resistance training, sprinting); CP system is active at the start of all activities, regardless of intensity; cannot supply energy for continuous long-duration activities
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CP donates a Phosphate to ADP to create ATP (potential energy) ADP + P = ATP

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Type II muscle fibers have a higher CP concentration than Type I Athletes often take supplemental CP (aka PC) to replete their bodies with this energy source

What type of athlete, or what type of training could benefit from CP supplementation

ATP Production – Energy Systems (cont.)
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Glycolysis – the breakdown of carbohydrates (CHO) to produce ATP
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Fast Glycolysis (aka Anaerobic Glycolysis)– occurs under conditions of reduced oxygen availability; CHO broken down to pyruvate and in the process, ATP is formed Slower ATP production vs. CP, but faster vs. slow glycolysis The ATP is then available to energize muscle contraction and pyruvate can be converted to lactic acid (LA) or it can enter into a third energy system (Oxidative or Aerobic System) LA can be converted to Lactate, which is shuttled back to the liver to be recycled into glucose If the rate of LA production exceeds its conversion to lactate, LA accumulation occurs in the muscle cells and blood stream; increasing LA levels can inhibit alter a muscle’s function by inhibiting further glycolysis, interfering with Actin-Myosin crossbridging, and causing fatigue; LA clearance rates are increased in the well trained aerobic or anaerobic athlete

ATP Production – Energy Systems (cont.)
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Slow Glycolysis – occurs under conditions where there is a sufficient quantity of oxygen in the muscle cell Pyruvate is not converted to LA and is available for use in the Oxidative (Aerobic) System known as the Krebs Cycle In reality, neither slow nor fast glycolysis will be operating to meet 100% of the athlete’s energy needs; rather, the ratio of Slow : Fast glycolysis is dependent on the extent of oxygen available to the muscle cell, and the cell’s ability to utilize the oxygen

ATP Production – Glycolysis (cont.)
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Lactate Threshold (LT)– the exercise intensity at which blood lactate begins an abrupt increase above baseline concentration; and after which diminished performance capacity is realized Training Effect - Training at intensities near, at, or above the LT can “push the LT curve to the right”, that is, a greater exercise intensity is required to raise lactate levels to the LT

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ATP Production – Energy Systems (cont.)
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Oxidative – the primary source for ATP production when the body is at rest, or at very low exercise intensity; this system uses primarily carbohydrates and fats (protein can be broken down for energy but the body naturally prevents this by “Protein Sparing”; reliance on protein stores for energy could result in a breakdown of the body’s structural proteins)
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Low intensity exercise – approximately 70% of ATP produced is derived from fats, 30% from CHO With increasing exercise intensity, a greater proportion of ATP production comes from CHO breakdown High intensity exercise – close to 100% of ATP derived from CHO breakdown Prolonged, submaximal, steady-state exercise results in a shift back towards fat and to some degree protein utilization for energy and ATP production Protein utilization may range from 3% to 18% during prolonged activity

What type of impact would these different exercise intensities have on training and nutrition

ATP Production – Oxidation (cont.)
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Glucose/Glycogen Oxidation occurs through a process called the Krebs cycle Fat Oxidation occurs through a process called Beta Oxidation Exercise Intensity – the level of muscular activity that can be quantified in terms of power  Maximal oxygen uptake is approximately 20-30% of peak power as measured on a cycle ergometer  Exercise or training performed in the aerobic range (up to 100% of maximal oxygen uptake) is therefore not considered high intensity exercise

Energy Production Continuum
Low Intensity, Long Term Exercise High Intensity, Short Term Exercise

Low
CHO or fat Oxidation

Exercise Intensity
Slow Glycolysis Fast Glycolysis

High
Creatine Phosphate

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High intensity, short duration exercises (i.e. resistance training, sprinting) have a high absolute power output, and therefore rely more on the CP energy system Low intensity, long term exercises (i.e. distance cycling, walking, marathon running) have a low absolute power output; this type of training relies more on the oxidative energy system (CHO/glucose or fat oxidation)

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Ranking of Bioenergetic Limiting Factors
Degree of exercise (example) ATP & CP Muscle Liver Fat Glycogen Glycogen Stores Lower pH

Light (marathon) Moderate (1,500-m run) Heavy (400-m run) Very intense (discus) Very Intense, repeated

1 1-2 3 2-3 4-5

5 3 3 1 4-5

4-5 2 1 1 1-2

2-3 1-2 1 1 1-2

1 2-3 3-4 1 4-5

NOTE: 1 = least probable limiting factor; 5 = most probable limiting factor

Effect of Event Duration on Primary Energy System Used
Duration of Event Intensity of Event Primary Energy System(s)

0-6 sec 6-30 sec 30 sec – 2 min 2-3 min

Very Intense Intense Heavy Moderate

Phosphagen Phosphagen & fast glycolysis Fast glycolysis Fast glycolysis and oxidative system

> 3 min

Light

Oxidative system

Contributions of Anaerobic & Aerobic Mechanism to Maximal Sustained Efforts in Bicycle Ergometry
0-5 sec 30 sec 60 sec 90 sec

Exercise intensity (% of max power output)
Contribution of anaerobic mechanisms (%) Contribution of aerobic mechanism

100

55

35

31

96

75

50

35

4

25

50

65

Metabolic Specificity of Training
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By prescribing the appropriate exercise intensities and rest intervals, an athlete can train the body to utilize energy systems specific to their sport or event Few sports require the athlete to exert a maximal sustained effort exercise to exhaustion or near exhaustion (i.e. cycling time trial, 10k running race) Most sports (soccer, resistance training, hockey, basketball, etc.) require high intensity, constant or near constant effort exercise bouts interspersed with periods of rest The aerobic, oxidative energy system is inadequate for producing the required power output of these types of intermittent sports Excessive training of the aerobic, oxidative energy system, and inadequate training of the CP and fast glycolysis systems improperly prepares the athlete for competition

Interval Training
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Interval Training – a system of training that uses appropriate exercise intensity and rest intervals in order to target energy systems specific to the athlete’s event Through interval training, more work can be performed at higher exercise intensities with the same or less fatigue than in continuous training The length and intensity of exercise bouts and rest periods are determined with the knowledge of the dominant energy source and the time needed for that energy source to be replenished

Interval Training (cont.)

Combination Training
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Combination training holds that multiple energy systems should be trained in order to enhance the capacity of the athlete’s primary energy system (i.e. aerobic training should be added to the anaerobic athlete’s training program to enhance recovery from anaerobic bouts)

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However studies have suggested that aerobic exercise may:  Reduce anaerobic performance capabilities, especially high strength and power performance  Reduce anaerobic energy production capabilities  Reduce gains in muscle girth, maximum strength, speed and power related performance

Combination Training (cont.)
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To the contrary, studies have suggested that anaerobic training can improve low intensity exercise endurance In prescribing aerobic exercise for the anaerobic athlete, concern must be given to the relative amount of aerobic training being performed by the athlete Because specific anaerobic training can stimulate increases in aerobic power and enhance markers of recovery, extensive aerobic training to enhance recover from anaerobic events is not necessary and may be counterproductive in most strength and power athletes

Interval Training of Specific Energy Systems
% of Maximum power 90-100 75-90 Primary system stressed Phosphagen Fast Glycolysis Typical exercise time 5-10 s 15-30 s Range of exercise- to-rest period ratios 1:12 to 1:20 1:3 to 1:5

30-75
20-35

Fast Glycolysis & Oxidative
Oxidative

1-3 min
> 3 min

1:3 to 1:4
1:1 to 1:3

“Performance gains typically are related to changes in more than one physiological system. The training program must train each physiological system in careful balance with specific performance goals in mind.”

References
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Baechle, TR. Earle, RW. Essentials of Strength Training and Conditioning, 2nd Ed. 2000. Human Kinetics.


				
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posted:11/3/2009
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