2Maximal oxygen uptake ALSO CALLED: VO2 max Peak aerobic power Maximal aerobic powerMaximum voluntary oxygen consumptionCardio-respiratory aerobic capacityMaximal cardio-respiratory fitnessMaximal functional aerobic capacity
3VO2 maxA maximum rate at which an individual can consume O2 during maximal exertion.Expressed as the maximum volume of oxygen consumed/minAbsolute: litres per min (L/min)Relative: milliliters per kilogram per minute (ml/kg/min)1 MET = metabolic equivalent = A unit used to estimate the metabolic cost oxygen consumption) of physical activity = 3.6 ml O2/kg/min
4VO2 max depends on 3 systems: Pulmonary, Cardiovascular, Muscular Cardiac output: stoke volume, heart rate, peripheral resistanceMuscle blood flow: capillary densityHemoglobin content (oxygen-carrying red pigment of the red blood corpuscles)Muscle massMuscle fiber typeOxygen extraction: muscle mitochondrial density, oxidative enzymesPulmonary function
5Oxygen deficit/oxygen debt Oxygen Deficit. While exercising intensely the body is sometimes unable to fulfill all of its energy needs. Specifically, it is unable to intake and absorb enough oxygen to adequately 'feed' the muscles the amounts of energy needed to adequately perform the tasks the athlete is requesting from the body. In order to make up the difference without sacrificing the output, the body must tap into its anaerobic metabolism. This where the body goes into a mix of aerobic and anaerobic energy production. While not hugely detrimental, oxygen deficits can grow to a level that the anaerobic energy system cannot cover. This can cause performance to deteriorate.Oxygen Debt. This term describes how the body pays back its debt incurred above after the exercise is over. You will notice that even after you are done racing you will continue to breath hard. At this point your body is still trying to repay the oxygen debt that was created when you were working hard. Technically, it is excessive post-exercise oxygen consumption.
7Factors affecting VO2 max HeredityAgeSexBody size and compositionTraining statusTypes of muscle fibers used during the exerciseAltitudeTemperature
8Factors affecting VO2 max HeredityIt is well established that the limits for developing fitness capacity are linked to genetic endowment.Genetic effect is currently estimated at approximately 20-30% for VO2 max, 50% for maximum heart rate, and 70% for physical working capacity.
9Factors affecting VO2 max AgeChildrenAbsolute values for girls and boys are similar until age 12At age 14 VO2 max value for boys 25% > girls and by age 16, the difference exceeds 50%.Relative values for boys VO2 max remains level at about 52 ml/kg/min from age 6-16
10Age related changes in VO2 max Average VO2 max in males18-25y 43-4636-45y 35-3946-55y 32-34>65y 25-28Average VO2 max in females18-25y 39-4136-45y 31-3346-55y 28-30>65y 22-24
12Factors affecting VO2 max Adults After age 25 its all down-hill (VO2 max declines at a rate of 1% per year after age 25) BUT one’s habitual level of physical activity has far more influence on aerobic capacity than age!
13Factors affecting VO2 max SexEven among trained endurance athletes, the sex difference for VO2 max = 15-20% mainly due to differences in:• Differences in body composition• Hemoglobin (oxygen-carrying red pigment of the red blood corpuscles) concentration
14Factors affecting VO2 max Body size and compositionAn estimated 69% of the differences in VO2 max scores among individuals can be explained by variations in body massMode of exerciseHighest values are generally found during treadmill exercise, lowest on bicycle ergometer test; specificity is very importantMuscle fiber typeSlow oxidative fibers – highest oxygen consumption
15Exercise and VO2 maxMoving from rest to exercise = energy requirementsMetabolism increases in direct proportion to rate of workAs demand for energy increases so does oxygen consumption (remember the role of oxidation to produce ATP to do work)VO2 eventually peaks = VO2 maxVO2 may remain constant at max or drop slightly even through work intensity continues to increase.Increased O2 consumption with increasing power output
16Other factors affecting VO2max AltitudeLow partial pressure of O2 in the atmosphereLower partial pressure of O2 in the arterial bloodLower hemoglobin saturationTemperatureHigher temperature – higher oxygen consumption
17Why VO2 testing?A measure of cardiorespiratory endurance gives us an indication of the individual’s aerobic fitness.Endurance athletes generally have a larger capacity for aerobic energy transfer.VO2 max is generally lower (10-20%) for females than males.
18Predicting VO2 maxDirect measurement of VO2 max requires an extensive laboratory and specialized equipment as well as considerable subject motivation.Direct tests are not suitable for measuring large groups of untrained subjects outside of the lab.Direct tests are strenuous and thus could pose a hazard to adults who are not fit
19Advantages Inexpensive No training required Short duration Safety because of submaximal effortVO2 can be estimatedHR and BP can be monitored
20Disadvantages Max HR and BP are not measured VO2max is not measured directlyLimited usefulness
21Predictive test for aerobic capacity Although there are many predictive tests available we only focus on those used most commonly in the labThe treadmill testYMCA stationary bicycle protocolBench step test
22Predictions based on heart rate Common tests to predict VO2 max use exercise or post-exercise HRThese tests make the use of the essentially linear relationship between HR and VO2 during various intensities of light to moderately heavy aerobic exercise
23Assumptions made in VO2 max predictions Linearity of HR-VO2 relationshipSimilar maximum HR for all subjectsAssumed constant economy or mechanical efficiency during exerciseSmall day to day variations in HR (+/- 5 bpm)Method is with of real values, good for screening
26Calculating VO2max Here’s how you do the calculation: If you are male, start with the number If you are female, begin with 100.5Calculate your weight in kilograms by dividing your weight in pounds by Then multiply your weight in kilograms by Finally, subtract the resulting number from either (male) or (female). Example: Kathy weighs 139 pounds. (a) 139/2.2= 63.2 kilograms. (b) 63.2 x = (c) = 90.16Convert the time it took you to jog the mile into a decimal number. Multiply this decimal number by Subtract the result from the last number obtained in step #2. EXAMPLE: (a) Kathy jogged her mile in 10 minutes and 15 seconds, which is minutes. (b) x = (c) – =To obtain your VO2max, multiply your heart rate (taken right at the end of the one mile jog) by Subtract the result from the last number obtained in step #3. Example: Kathy’s heart rate at the end of the mile was 132. (a) 132 x = (b) – = So, Kathy’s VO2max is about 50 milliliters of oxygen per kilogram of body weight per minute. With a VO2max of 50, she should be able to complete a 5K in around 29 minutes, a 10K in about 41:20, and a marathon in 3:11.
27Prediction equations for bench step MenVO2max = – (0.42 x HRREC)WomenVO2max = – ( x HRREC)HRREC = 15 second recovery HR (bpm)
28Pre-test screeningBe sure to carefully follow ALL procedures in lab manualSubject must answer NO to all questions on PAR-Q (physical activity Readiness Questionnaire) and sign it in order to carry on with testingSubject must complete the submaximal testing readiness questionnaire