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Exercise Physiology

 

Basic definitions of terms:

VO2Max = cardiac output x oxygen uptake Necessary to supply oxygen to muscles. The "Fick equation" is the basis for determination of VO2.

Oxygen uptake (cardiac output) (arterial-venous oxygen difference)

Cardiac output(Q) product of stroke volume (SV) and heart rate (HR)


Aerobic exercise requires oxygen to be present for the generation of energy from fuels such as glucose or glycogen. It results in no buildup of lactic acid as a result of metablolism. It is a more efficient process than anaerobic metabolism. During normal rest and aerobic exercise carbohydrates and fats are used as fuels. A high degree of aerobic fitness, requires a well adapted ability to take in, carry and utilize oxygen. Laboratory measurements are most accurate, but expensive. Estimates may be made of your fitness level as depicted in charts presented later.

Anaerobic exercies is usually of short duration and produces lactic acid. It is high intensity and has a greater inherent risk of injury.

Unconditioned individuals have a lower anaerobic threshold than the aerobically trained athlete. The well trained athlete may be able to approach 80% of the maximum oxygen uptake level aerobically without lactate production. The usual measurements are in liters per minute, or to account for the size of the individual in milliliters per kilogram per minute (ml/kg/min). The values for the average 20 year old are between 37 to 48 ml/kg/min. The highly trained male athlete may approach the high 70's to low 80's. Training, therefore, enhances the ability of the body, and muscle cells in particular, to better handle oxygen. Muscle must be able to use oxygen efficiently to keep anaerobic metabolism at a given level of effort to a minimum.

Cardiac output is a major determinant of oxygen uptake. Maximum oxygen uptake (MVO2) declines with age as the maximum heart rate declines. This is one of the major factors causing the approximately 7 percent decline with each decade of life, after age 30 of course. Muscle training and utilization of oxygen at the end organ, muscle, is the second factor that affects oxygen uptake. The A-V oxygen difference comes about as a combination of arterial oxygen content, shunting of blood to muscles and the muscle extraction of oxygen.

Training results in a more efficient heart and an increase in the maximum stroke volume. An increase in VO2 results in an ease in the stress of a given workload. When maximum stroke volume is increased the heart can work more efficiently at a given pulse rate. This lessens the necessity of increased pulse at a given workload. Resting pulse is lower as is the pulse at any given work load.

METs-metabolic unit One met equals the VO2 at rest. The estimate of the valueof one MET is 3.5 ml O2/kg/min. Conversion of VO2 measurements may be obtained by dividing the value of the VO2 in ml of oxygen/kg/min by the value of one MET or 3.5. For example a VO2 measurement of 35 ml O2/kg/min is equivalent to an output of 10 mets.


Cardiac Changes Following Training

Resting bradycardia - frequently resting pulse below 50 Cardiac Hypertrophy - Left sided enlargement. Left ventricular hypertrophy. Strength trained athletes, such as weight lifters, appear to have a thickened ventricular wall rather than enlargement of the ventricular chamber itself.

ECG Changes related to Left Ventricular Hypertrophy - widened QRS complex, split QRS complex References include: Sports Medicine Straus.

Pre-exercise Cardiac Evaluation

It is important that family history be taken into account when contemplating a fitness program. A history of cardiac problems or suddent death in a young parent must be given attention by your physician. Symptoms such as pain in the chest, palpitations, difficulty breathing or dizziness following exercise are important to note and should be thorougly evaluated.

Muscle Changes Following Training

Improvement in ability to handle workload. Increase in strength, oxygen extacting and utilization capacity, increase in myoglobin content, increase in capillaries via development of enhanced capillary secondary pathways and collateral circulation. This increase in vascularity decreases the distance over which oxygen must diffuse to be delivered to muscle fibers. Increase in muscle fiber cross section diameter occurs, probably to a greater degree in fast twitch fibers. Increase in fuel utilization enzymes in muscles and enlargement of mitochondrial size.

 

Overtraining

There are variety of different signs and symptoms of overtraining. Most often mentioned is unusual fatigue or a feeling of staleness. The early morning resting pulse may jump 5 or more beats. A falloff in performance may occur, despite increased training. Muscles may be unusually sore. Emotional changes may also be noticed. Increased anxiety, tension, depression or anger may occur. Difficulty focusing and in making decisions may also occur. The desire to train may disappear. Joy in other activities may also dissipate. Bowel changes may be noted - diarhhea or constipation may occur. More frequent cold or virus infections may occur. Loss of appetite and weight loss may also occur.

Overtraining symptoms bear much resemblance to chronic fatigue syndrome. Overtraining is definitely to be avoided. Too much training can adversely affect your performance to a greater extent than can too little. Fatigue, injuries and a whole host of negative consequences may result from overtraining. The expression summing up much of the overtraining injury syndrome is"Too Much, Too Soon" . You may also add "Too Far, Too Fast" and now you have a near complete set of the terrible toos of overtraining.


Misc.

Selected Sports Bras

Jogbra- are one-sheet of elastic type which has coolmax to wick away moisture. Sizing is small medium and large.

Misha-Possibly obtainable at dance stores. Named after Baryshnikov

Vanity Fair running bra-underwire and compression, very supportive


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