Class Notes (839,315)
Canada (511,260)
EDKP 395 (37)
Lecture 4

Lecture 4 (revised) .docx

20 Pages

Kinesiology&Physical Education
Course Code
EDKP 395
Russell T Hepple

This preview shows pages 1,2,3,4. Sign up to view the full 20 pages of the document.
10/29/2012 7:06:00 AM Estimation of Fuel utilization during exercise: RER Respiration exchange ratio o Estimates the % contribution of CHO or fats to energy metabolism. o Calculated at the ratio b/w carbon dioxide production (VCO2) and rate of oxygen consumption (VO2) Both fats and carbs differ in their amount of O2 consumed and CO2 produced during oxidation RER for fat 16 CO2/23 O2= .70 RER for CHO 6 CO2/6 O2 = 1 closer to 1- use more CHO as energy source glycolytic energy source further from 1- use more fat stores o Usage: Must reach a steady state of exercise Only during steady state conditions are VCO2 and VO2 relfective of O2 consumption and Co2 production in the tissues RQ- respiratory quotient o VcellCO2/VcellO2 o Will never exceed 1 o Results can reach a max of 1.5 during intense exercises Lactic acid (HLa) is produced during Glycolysis HLa dissociates into La- and H+ causing an increase in acidity (acidosis, decrease in pH) In blood bicarbonate will combine w/ H+ to form carbonic acid In the lung H2CO3 dissociates into CO2 + H2O CO2 that appears in expired breath reflects both metabolic and non-metabolic production of CO2 Non metabolic artificially increases VCO2, which accounts for the RER >1 note: operating at VO2 max requires the use of CHO as energy source VCO2 and VO2 increase linearly with each other o up to a certain point that occurs during intense exercise that causes the levels of VCO2 to increase quicker than O2 this COINSIDES with lactate threshold Factors governing fuel selection during exercise INTENSITY & DURATION most important factors Intensity o Cross-over concept As exercise increases from mild to moderate to heavy the fuel mix switches (crosses-over) such that CHO becomes increasingly more important and fat become progressively less important Recruitment of Type IIa & IIx fibers to help match power output with demand Increases blood levels of epinephrine that stimulate glycogenolysis Duration o Prolonged low intensity >30min gradual shift from CHO towards reliance on oxidation of fats Fat metabolism depends on factors governing lipolysis which increases blood and muscle levels of free fatty acids by lipase enzymes Lipase enzymes are generally inactive until stimulated by NE, EPI hormones and glucagon which is a hormone released from pancreas in response to increasing EPI During prolonged, low-intensity exercise there is a progressive increase in EPI, NE, and glucagon which results in progressive increase in lipase acitivty and therefore lipolysis Body fuel sources during exercise Majority of CHO are stored as glycogen in liver/muscle o Muscle glycogen stores provide DIRECT source of CHO for metabolism via glycogenolysis ~ 1400 kcal in 350 gs o Liver glycogen stores serve as means of replacing (and regulating) blood glucose (glycogenolysis) ~240 kcal for 60 gs Blood glucose represents a small source of CHO for metabolism ~ 40 kcal for 10gs Fat is stored as triglycerides in adipocytes with a very small amount stored in muscles o Adipocytes ~ 107800 kcal in 14kg o Muscle ~ 3850 Obesity in inuit populations Have a greater fat intake than normal people store more of the fat in muscles than normally found o High fat stores in muscles can be good for endurance athletes Exercise intensity influences type of CHO/fat used Blood glucose- low intensity exercise Glycogen- high intensity exercise o Increase muscle glycogen use during high intensity exercise reflects increased rate of glycogenolysis that occurs due to recruitment of fast-twitch fiber and increased blood [EPI] Plasma free fatty acids- low intensity exercise Intramuscular triglycerides & plasma FFA- > or equal to 65% VO2max Exercise duration influences type of CHO/fat used Fat: prolonged submaximal exercise o Beginning: plasma FFA & intramuscular triglycerides o Later: plasma FFA Interaction of Fat & CHO metabolism during prolonged exercise After 2 hrs sub-maximal exercise muscle glycogen stores are depleted leads to muscular fatigue o Decreases glycolytic flux & rate of pyruvic acid production o This leads to decreases in concentrations of kreb-cycle intermediates and as a result a decrease in the rate of ox. Phos this limits muscle function and may result in fatigue o Since fats an only be metabolized via kreb-cycle oxidation, a decrease in kreb-cycle intermediates due to decreased amounts of intermediates provided by Glycolysis decrease the rate of ATP production from fat metabolism Why we say that fats burn in the flame of carbs
More Less
Unlock Document

Only pages 1,2,3,4 are available for preview. Some parts have been intentionally blurred.

Unlock Document
You're Reading a Preview

Unlock to view full version

Unlock Document

Log In


Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.