Exercise Physiology

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267-269, 277-280

* Direct calorimetry uses the measurement of heat production as an indication of metabolic rate. * Indirect calorimetry estimates metabolic rate via the measurement of oxygen consumption.

* Energy expenditure can be expressed in L•min-1, kcal•min-1, ml•kg-1•min-1, METs, and kcal•kg-1•hr-1. * To convert L•min-1 to kcal•min-1, multiply by 5.0 kcal•L-1. * To convert L•min-1 to ml•kg-1•min-1, multiply by 1000 and divide by body weight in kilograms. * To convert ml•kg-1•min-1 to METs or kcal•kg-1•hr-1, divide by 3.5 ml•kg-1•min-1. Efficiency:

* Exercise work rate
* Efficiency decreases as work rate increases
* Speed of movement
* There is an optimum speed of movement and any deviation reduces efficiency * Muscle fiber type
* Higher efficiency in muscles with greater percentage of slow fibers

SUMMARY: Net efficiency is defined as the mathematical ratio of work performed divided by the energy expenditure above rest, and is expressed as a percentage. * The efficiency of exercise decreases as the exercise work rate increases. This occurs because the relationship between work rate and energy expenditure is curvilinear. * To achieve maximal efficiency at any work rate, there is an optimal speed of movement. * Exercise efficiency is greater in subjects who possess a high percentage of slow muscle fibers compared to subjects with a high percentage of fast fibers. This is occurs because slow muscle fibers are more efficient than fast fibers. * Not possible to calculate net efficiency of horizontal running * Running Economy

* Oxygen cost of running at given speed
* Lower VO2 (ml•kg–1•min–1) at same speed indicates better running economy * Gender difference
* No difference at slow speeds
* At “race pace” speeds, males may be more economical that females

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CIRCULATORY RESPONSE TO EXERCISE

Organization: arteries branch to form vessels, vessels become microscopic and form arterioles, which develop into “beds” called capillaries. Capillaries are the smallest and most numerous of blood vessels—exchange of oxygen, CO2, and nutrients. Blood passes from capillary beds to venules that move back to heart and increase in size becoming veins. Mixed venous blood= mixture of venous blood from both upper and lower body in the right side of the heart. *it represents an average of venous blood from entire body.

HEART:
Right/left side separated by muscular wall called interventricular septum (prevents mixing blood from sides).

Valves:
Bicuspid/mitral = left atrioventricular valve **atrioventriculars close when heart contracts to prevent backflow. Tricuspid= right atrioventricular valve
Semilunar valve (pulmonary semilunar)- b/w right ventricle and pulmonary artery. Prevents backflow from arteries into ventricles. Aortic valve (aortic semilunar)= b/w left ventricle and aorta. Also prevents backflow…

Right side pumps deoxygenated blood to pulmonary circuit so oxygen can be loaded and CO2 released. Left side pumps oxygenated blood to body via systemic circuit. RIGHT: to lungs
LEFT: to body

Heart sounds are due to closing of atrioventricular valves (first sound-systole) and the closing of aortic and pulmonary valves (second sound-diastole)

Wall of heart is 3 layered: 1) outer layer is epicardium, 2) muscular middle layer called myocardium, 3) inner layer endocardium. Myocardium contracts to force blood out. Right and left coronary arteries supply myocardium Cardiac muscle fibers are shorter than skeletal and are branched and involuntary. Heart muscle fibers are all connected via intercalated discs- transmit electrical impulses. They are leaky membranes that allow ions to cross b/w fibers (contract together= functional syncytium). *atria contract separate from ventricles because there is a separating layer of CT *heart is only type 1, slow fiber- highly aerobic, many mitochondria (more than...
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