PE 254
PE 254 Maximal oxygen uptake ALSO CALLED: VO2 max Peak aerobic power Maximal aerobic power Maximum voluntary oxygen consumption Cardio-respiratory aerobic capacity Maximal cardio-respiratory fitness Maximal functional aerobic capacity VO2 max A maximum rate at which an individual can consume O2 during maximal exertion. Expressed as the maximum volume of oxygen consumed/min Absolute: 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 VO2 max depends on 3 systems: Pulmonary, Cardiovascular, Muscular Cardiac output: stoke volume, heart rate, peripheral resistance Muscle blood flow: capillary density Hemoglobin content (oxygen-carrying red pigment of the red blood corpuscles) Muscle mass Muscle fiber type Oxygen extraction: muscle mitochondrial density, oxidative enzymes Pulmonary function Oxygen 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. Oxygen deficit/oxygen debt Factors affecting VO2 max Heredity Age Sex Body size and composition Training status Types of muscle fibers used during the exercise Altitude Temperature Factors affecting VO2 max Heredity It 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. Factors affecting VO2 max Age Children Absolute values for girls and boys are similar until age 12 At 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 http://jap.physiology.org/cgi/content/abstract/65/3/1147 Age related changes in VO2 max Average VO2 max in males 18-25y 43-46 36-45y 35-39 46-55y 32-34 >65y 25-28 Average VO2 max in females 18-25y 39-41 36-45y 31-33 46-55y 28-30 >65y 22-24 Age and VO2max in Healthy Subjects Factors 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! Factors affecting VO2 max Sex Even 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 Factors affecting VO2 max Body size and composition An estimated 69% of the differences in VO2 max scores among individuals can be explained by variations in body mass Mode of exercise Highest values are generally found during treadmill exercise, lowest on bicycle ergometer test; specificity is very important Muscle fiber type Slow oxidative fibers – highest oxygen consumption Exercise and VO2 max Moving from rest to exercise = energy requirements Metabolism increases in direct proportion to rate of work As demand for energy increases so does oxygen consumption (remember the role of oxidation to produce ATP to do work) VO2 eventually peaks = VO2 max VO2 may remain constant at max or drop slightly even through work intensity continues to increase. Increased O2 consumption with increasing power output Other factors affecting VO2max Altitude Low partial pressure of O2 in the atmosphere Lower partial pressure of O2 in the arterial blood Lower hemoglobin saturation http://jap.physiology.org/cgi/content/abstract/91/3/1113 Temperature Higher temperature – higher oxygen consumption Why 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. Predicting VO2 max Direct 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 Advantages Inexpensive No training required Short duration Safety because of submaximal effort VO2 can be estimated HR and BP can be monitored Disadvantages Max HR and BP are not measured VO2max is not measured directly Limited usefulness Predictive test for aerobic capacity Although there are many predictive tests available we only focus on those used most commonly in the lab The treadmill test YMCA stationary bicycle protocol Bench step test Predictions based on heart rate Common tests to predict VO2 max use exercise or post-exercise HR These tests make the use of the essentially linear relationship between HR and VO2 during various intensities of light to moderately heavy aerobic exercise Assumptions made in VO2 max predictions Linearity of HR-VO2 relationship Similar maximum HR for all subjects Assumed constant economy or mechanical efficiency during exercise Small day to day variations in HR (+/- 5 bpm) Method is with 10-20 of real values, good for screening Relationship between HR and VO2 Calculating VO2max The formulas: Male: 108.844 – [lbs./2.2 (0.1636)] – [time (1.438)] – [HR (0.1928)] Female: 100.5 – [lbs./2.2 (0.1636)] – [time (1.438)] – [HR (0.1928)] Calculating VO2max Here’s how you do the calculation: If you are male, start with the number 108.844. If you are female, begin with 100.5 Calculate your weight in kilograms by dividing your weight in pounds by 2.2. Then multiply your weight in kilograms by 0.1636. Finally, subtract the resulting number from either 108.844 (male) or 100.5 (female). Example: Kathy weighs 139 pounds. (a) 139/2.2= 63.2 kilograms. (b) 63.2 x 0.1636 = 10.34. (c) 100.5-10.34 = 90.16 Convert the time it took you to jog the mile into a decimal number. Multiply this decimal number by 1.438. 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 10.25 minutes. (b) 10.25 x 1.438 = 14.74. (c) 90.16 – 14.74 = 75.42. To obtain your VO2max, multiply your heart rate (taken right at the end of the one mile jog) by 0.1928. 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 0.1928 = 25.45. (b) 75.42 – 25.45 = 49.97. 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. Prediction equations for bench step Men VO2max = 111.33 – (0.42 x HRREC) Women VO2max = 65.81 – (0.1847 x HRREC) HRREC = 15 second recovery HR (bpm) Pre-test screening Be sure to carefully follow ALL procedures in lab manual Subject must answer NO to all questions on PAR-Q (physical activity Readiness Questionnaire) and sign it in order to carry on with testing Subject must complete the submaximal testing readiness questionnaire Videos on VO2max tests http://www.youtube.com/watch?v=u5xiJ1qpMmA&fea ture=related http://www.youtube.com/watch?v=18- Fj8ub7Ik&feature=related http://www.youtube.com/watch?v=xi9ZGl1Ha3o&feat ure=related Monday, September 14th Read Chapter 2 before Monday, September 14th Please meet at the Fitness Lab, PE 2A (across from the Student Wellness Center) on Monday, September 14th
© Copyright 2024