Chapter 12
Exercise Metabolism

Interest is how hard a person is working

Two ways to measure: Mechanical and Physiological

	Mechanical:

		Work = Force times Distance (foot-pounds, Newton-meters)
			ex: Bicycle = Resistance times Pedaling Rate

		Power = Work / Time (Newton-meters/sec -or- Joules)

		Energy = Potential and Kinetic

		Efficiency = Ability to use Energy to perform Work
		 - (energy used / work done)

	Physiological (VO2)

		Not always possible to measure Work
			treadmill; how to measure the Force

		Kinetic / Potential Energy hard to measure

		Measure Work by Energy Used
		 - Our Energy Used is ATP
		 - ATP is produced by O2
		 - Can measure O2 used (consumed)
		 - Relationship between O2 consumption (VO2) and mechanical work


Modes of measurement of VO2 and VO2max

	Treadmill is the standard
		- most accurate results for general population
		- most people can walk, run, or roll
	Bicycle is used most commonly
		- less cost
		- often results in early fatigue due to quad fatigue
	Bench Stepping
		- least cost
		- least reliable
	Anything possible (swimming, hiking, scuba diving, etc.)


Other Methods Used to Estimate VO2

	Bench Stepping
		- based on relationship between O2 consumption and heart rate 

	Run / Walk Times (correlation's)

	Calorimetry (measure heat gain)
		- direct = measure all the temperature changes
		- indirect = measure the changes in gas temperature

	Gas Analysis
		- measure changes in O2 and CO2 during exercise
		- used to collect in bags, then run through machine
		- later, collected in cylinder, and mechanically analyzed every 15/30 sec
		- now, breath by breath analysis

Other Factors in Measuring Physiological Work

	O2 Deficit, O2 Debt (recovery), and EPOC (excess post-exercise O2 consumption)

		As begin exercise, not producing enough O2 to do work
			Accumulate Lactate
			This is the O2 deficit
			This will have to be paid back (metabolized later)
		After end of exercise, metabolism remains elevated for some time
		Called O2 debt
			Due to:
				Normal functioning
					chemicals still driving system
				Replacing energy stores
					ATP/CP, Glucose, Glycogen
				Making up for the O2 deficit 
					metabolizing lactate => pyruvate => O2 cycle
		Theoretically, O2 debt should equal O2 deficit
			However, O2 debt is substantially higher
			Therefore, the term EPOC is now used to describe the O2 debt
				(Excess Post-Exercise Oxygen Consumption)
			Amount of EPOC varies depending upon training
				Mode, Intensity, Intervals, etc.
			Possible reason for EPOC variance, 
				Repair of damaged tissues



	Anaerobic Threshold / Lactate Threshold / Ventilatory Threshold / OBLA

		During low intensity exercise, the O2 (aerobic) system supplies the necessary ATP
		As intensity increases, eventually the O2 system cannot meet the demands 
		The Lactic-Acid (anaerobic) System then supplements the O2 system
			- termed the Anaerobic Threshold (AT)
		As intensity further increases, lactate continues to increase
			- thus, 	AT sometimes called the lactate threshold

		If intensity increases linearly (slope 1), ventilation (Ve) will also increase linearly
		However, at about AT, Ve begins to increase at a faster rate (slope 2)
		Where slope 1 and slope 2 intersect, this is the Ventilatory Threshold (VT)
		Has been used to signify the AT
			- correlation's of blood lactate and VT

		Problems with this idea:
			1. Muscles both produce and consume lactate
			2. Lactate is measured in the veins but produced in the muscles
				- time delay, liver also metabolizes lactate
				- thus, poor relationship exists

		Final term best describes condition:
			OBLA (Onset of Blood Lactate Accumulation)
			describes the build-up of blood lactate


	Respiratory Quotient (RQ) / Respiratory Exchange Ratio (RER)

		each are the Volume of CO2 produced / Volume of O2 consumed
		at steady state, the term Respiratory Exchange Ratio (RER) is also used
			- steady state refers to a constant metabolism (HR, VO2, etc.)
		RER tells what fuels are being burnt

			The range of RER values is 0.70 to 1.0
			.70 is pure fat
			1.0 is pure carbohydrates
			.83 (normal) is a mixture of the two 
		
			To determine protein used, need urinary nitrate (UN) sample

		RQ is A value looked at to determine level of exertion (i.e. maximal)
			other values are: HR at/near max, plateau of VO2, etc.



		
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