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EXERCISE PHYSIOLOGY DR GAVIN SHANG SPORTS MEDICINE PHYSICIAN MBBCH (WITS) MPHIL SPORTS MEDICINE (UCT/SSISA) NO CONFLICT OF INTEREST OR FINANCIAL DISCLOSURES RELATED TO THIS TALK 2
PHYSIOLOGICAL CONSIDERATIONS DURING EXERCISE Human movement requires energy Energy = created nor destroyed but changes form Chemical to mechanical forms ENERGY PATHWAYS Energy derived from adenine tri-­‐phosphate (ATP) ATP = energy currency of the body Supply is limited Needs to be constantly re-­‐synthesized Body needs a continuous supply of energy Metabolic pathways which produce ATP depend on the intensity and duration of the activity Aerobic vs. anaerobic energy pathways AEROBIC PATHWAY Aerobic energy pathway occurs in the mitochondria of cells Energy is generated in the presence of oxygen Provides a large amount of energy but at a slow rate Suitable for low intensity and long duration exercise ANAEROBIC PATHWAY Anaerobic energy pathway occurs
in the cytoplasm of cells Energy is generated in the absence of oxygen Provides a small amount of energy but at a fast rate Suitable for high intensity and short duration exercise 2 different methods of producing energy: -­‐ lactate system -­‐ phosphate system ENERGY SYSTEMS Energy for activity provided by the breakdown of ATP Energy released when bonds are broken ATP => ADP + P + ENERGY Aerobic system and anaerobic systems even though described separately occur in conjunction with one another Aerobic = low intensity exercise Anaerobic = high intensity exercise ENERGY SYSTEMS AEROBIC SYSTEM Aerobic system: -­‐ low intensity, continuous exercise allows time for oxygen to be delivered to the muscles -­‐ 2 main sources of fuel = glucose and fat Broken down to produce ATP with carbon dioxide and water being the waste products Waste products eliminated through the lungs, sweat and urine ANAEROBIC SYSTEM PHOSPHATE SYSTEM: -­‐ Phospho creatine is stored in the muscle -­‐ rich energy molecule ATP + Phospho creatine provides enough energy for 5 – 10 seconds of maximal effort Phospho creatine also provides energy for re-­‐synthesis of ATP from ADP + P CP + ATP => ATP + creatine ANAEROBIC SYSTEM LACTATE SYSTEM: -­‐ breaks down glycogen to produce ATP -­‐ this replaces what has been used by the muscles Process known as anaerobic glycolysis Very inefbicient system Produces only 5% of ATP that is produced when glycogen is broken down in the presence of oxygen As glycogen is broken down in the absence of oxygen the metabolic by-­‐product is the build up of lactate and H+ ions Fatigue is related to the break down of glycogen and the diminished stores FUELS USED FOR EXERCISE Carbohydrates (CHO) Simple (glucose) vs. complex (starch) Complex CHO are broken down to simple CHO before being used for energy Body stores glucose as glycogen in liver and muscle Liver glycogen stores regulate blood glucose levels When exercising, glycogen is broken down into glucose and transported via the blood to the muscles Muscle glycogen is an immediate source of fuel in the muscle but has limited stores FUELS USED FOR EXERCISE Fats are another basic useable form of energy Free fatty acids stored in adipose and muscle tissue Major source of fuel Body has more stores for fat energy than CHO Free fatty acids can only be broken done in the presence of oxygen (aerobically) Used readily at low levels of exercise intensity OXYGEN UPTAKE Oxygen plays the pivotal role for energy production for sustained activities The more oxygen transported to the site the greater the endurance VO2 max = amount of O2 consumed for a given workload Measured when subject is exercising at maximum capacity whilst having their respiratory gas exchanges measured OXYGEN UPTAKE Sub-­‐maximal VO2 testing done under controlled conditions Treadmill Bicycle ergometer Rowing ergometer VO2 max = mls/kg/min or l/min CARDIAC OUTPUT With aerobic training, the body’s ability to improve blood blow and output increases VO2 max thus improves with increased bitness Cardiac output = amount of blood that the heart can pump out in 1 minute CO = HR x SV CO = cardiac output HR = heart rate (beats per minute) SV = stroke volume (volume of blood pumped with each beat) TRAINING EFFECTS Increased VO2 max (improved endurance) -­‐ increased in the contractile force of cardiac muscle -­‐ thus more blood is expelled with each beat -­‐ development of greater capillary networks for greater amounts of gas exchanges -­‐ increased number and size of mitochondria -­‐ increased mitochondrial enzyme activity -­‐ improved blood blow dynamics and oxygen carrying capacity TRAINING EFFECTS Excess post-­‐exercise oxygen consumption Positive carry-­‐over of increased basal metabolic rate after cardiovascular exercise Increase depends on exercise intensity, duration and regularity Exercise needs to be tailored to different individuals and their bitness and conditioning levels TRAINING EFFECTS Increased strength or power Improved neuromuscular functioning Increase in number and size of muscle bibres Protein (leucine, isoleucine, valine)