physiology of exercise

PHYSIOLOGY OF EXERCISEPPL 30MFall 2012

Mr. Del Duca

Monday, November 12, 2012

PHYSIOLOGY OF EXERCISE

• physiology is the study of the molecules, cells, organs, and systems involved in maintaining/sustaining life

• we will examine the physiology of exercise, that is, the ways in which exercise can affect different systems of the body

SOME ORGAN SYSTEMS

• cardio-respiratory - heart and lungs

• neuromuscular - nerves and muscle tissue

• skeletal - bones

• for each system, we will briefly outline the anatomy of the organs, and then examine how exercise affects the system

• heart and lungs

CARDIO-RESPIRATORY SYSTEM

PHYSIOLOGY OF THE HEART• the heart consists of 4

chambers: 2 atria, and 2 ventricles

• the heart pumps blood around the body through blood vessels (veins and arteries)

• it has specialized muscle cells that create their own rhythmic beating through electrical impulses

• heart rate is the measure of how many times your heart beats per minute, and it also a measure of exercise intensity

• with exercise and improved heart fitness, as with any muscle, your heart gets stronger and beats more effectively and efficiently

• each beat of the heart is more powerful, and pumps more blood; it actually gets more flexible, too

• therefore, with any given exercise intensity, your heart beats slower than it would prior to exercising

• in addition, the blood changes with exercise: increased hemoglobin (protein for transporting oxygen) results in better oxygen transport throughout the body

PHYSIOLOGY OF THE HEART

PHYSIOLOGY OF THE LUNGS

• the lungs consist of a series of “tunnels” that bring air from the outside world into your bloodstream, and vice versa

• they are “opened” and “closed” by a special muscle called the diaphragm

PHYSIOLOGY OF THE LUNGS

• during exercise, breathing rate is increased, and oxygen uptake and usage can increase by up to 20x

• this is due to an increase in ventilation (breathing rate), better oxygen diffusion into the blood at the alveoli (more hemoglobin), and better oxygen uptake by cells (muscle cells - more on that later)

NEUROMUSCULAR SYSTEM

• neuromuscular system consists of all the parts involved in voluntary movement:

• brain, nerves (neurons), muscles

PHYSIOLOGY OF THE NEUROMUSCULAR SYSTEM

• specific part of the brain is responsible for movement: motor cortex

• signals originate here (under influence of other parts of the brain), and are sent down spinal cord to muscles around the body

• involuntary movement (breathing, heart beat) is under different control

BRAIN IMPROVEMENTS WITH EXERCISE

• with training, your brain becomes more efficient at sending signals to your muscles:

• neuron networks are rearranged, so that signals are sent faster, and are more coordinated

• “muscle memory” is actually the result of improved brain function - certain movements become automatic, originate in spinal cord rather than in brain

• improved reaction time - signal is more direct from brain to muscles

NERVES AND NEURONS

• nerves are simply bundles of neurons, and neurons are simply long cells that transmit electrical signals from the brain

• with exercise, neuromuscular junctions become more efficient at regulating the signal strength and duration (greater coordination and precision of movements)

MUSCLES AND MUSCLE CELLS

MOTOR UNITS

• a motor unit is simply one nerve and all the muscle fibres that it innervates (connects to)

MUSCLE FIBRE TYPE

• muscles fibres are broken down into 3 categories: type I fibres (slow twitch), type IIa and IIb fibres (fast twitch)

• type IIa and IIb can produce significantly more power (strength and speed); up to 10x more than type 1

• research suggests that training can change the distribution of type IIa and IIb, whereas type I is permanent

PHYSIOLOGY OF MUSCLE CELLS

• there are MANY training-induced changes that can be made to muscle tissue, including:

• increased vascularization (more blood vessels) resulting in:

• greater oxygen and glucose delivery, greater waste removal

• greater number of muscle fibres AND greater size of each muscle fibre = greater force production

• greater number of motor units recruited = greater force production

• more coordinated motor unit recruitment (fast twitch muscle fibres activated faster with training)

• more mitochondria in each muscle cell = more efficient use of oxygen = less lactic acid = less fatigue

KEY POINTS

• although exercise in general can increase fatigue resistance in muscles, different types of training can modify your muscles ability to continue to perform that particular activity

• example: aerobic training can increase the enzymes responsible for using oxygen to provide energy (ATP)

• this is called the SPECIFICITY PRINCIPLE (your body will perform better at the things you train it to do)

PHYSIOLOGY OF BONE

• bone consists of a very hard crystallized structure and different types of cells and blood vessels that maintain its amazing structure and function

PHYSIOLOGY OF BONE

• stem cells differentiate into different types of blood cells in the marrow

• osteoblasts create the crystal matrix, osteoclasts break the matrix down - constant remodelling

• bones allow for muscle attachment, and are protected at joints by cartilage and other structures

CHANGES IN BONE (& CONNECTIVE TISSUE)

• with exercise (especially resistance training), there are several important changes that occur in bone

• greater bone density - less likely to develop osteoporosis

• greater ligament and tendon strength

• faster healing - broken bones, torn ligaments, etc.

TAKE HOME POINTS

• the body has an amazing capacity for regeneration/repair - it is constantly breaking down and rebuilding all the molecules in our body -- exercise makes the rebuilding process more efficient

• specificity in adaptation - your body will get better at doing the things you train it to do:

• supplying blood and oxygen through cardiorespiratory system

• coordination of neural signals leading to voluntary movement

• muscular adaptations to exercise - strength, fatigue resistance/endurance

• increased bone density/more efficient repair of damaged connective tissue

physiology of exercise

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