Assessing Energy Expenditure

Chapter Learning Outcomes Discuss the importance of CRF in both health and functional implications Describe which method of testing would be appropriate in certain situations Compare and contrast the different tests used to predict CRF Describe the procedures to various submaximal exercise tests Describe the threats to accurate interpretation of submaximal testing results

Aerobic vs Anaerobic Aerobic means “with oxygen”. The term aerobic relates to the energy processes that occur in the presence of adequate oxygen. “Aerobic Fitness” is the ability of the heart and lungs to provide the oxygen needs of the body (muscular system) over a sustained period of time. Aerobic Fitness may be limited by: O2 transport ability Cardiac/vascular limitations The ability of the muscles to extract and utilize oxygen

Aerobic vs Anaerobic Anaerobic means “without oxygen” Short-term, intense activity due to energy system used If continued, activity must cease due to increases in pyruvate/lactate/H2+ When oxygen availability is not sufficient to meet the demands of the workload, blood lactate concentrations start to rise significantly above resting values, triggering the AT.

Cardiorespiratory Fitness (CRF) Health-related concept of fitness – the ability of the CV system to effectively deliver fuel to the exercise muscles. Best represented by VO2MAX Defined as the greatest rate at which oxygen can be consumed during exercise. Typically expressed in milliliters of oxygen consumed per kilogram of body weight per minute (ml/kg/min). EXAMPLE: Collegiate female athletes, should have a VO2MAX of 55ml/kg/min

Assessing VO2MAX Why? How? Aerobic, functional and work capacity Health status Exercise/activity prescription How? Maximal Graded Exercise Treadmill Test (GXT) Laboratory assessment with direct measurement of: O2 consumption and CO2 expiration (RER) Blood lactate levels 12-lead EKG

VO2MAX Laboratory criteria for achieving a true VO2max: Oxygen consumption plateaus during last min RER increases to 1.15 or higher HR within 10 bpm of age-predicted HRmax Blood lactate levels rise above 8 mmol/liter

VO2MAX Laboratory GXT is prohibitive Estimating VO2MAX Equipment Personnel Safety Estimating VO2MAX Nomograms Field tests for CRF Submaximal laboratory tests Which to use? Equip/facilities/cost Time Risk to subject

Prediction Nomograms Predicting VO2MAX without any exercise is possible…. VO2 = 5.0 x wt (kg) + 19.8 International Physical Activity Questionnaire (IPAQ) Regression Equations …but poorly validated and not reliable Use only when necessary

Field Tests Step tests Females: VO2 = 68.81 – (0.1847 x HR) Harvard Two-Step Test, 1953 YMCA Step Test, Queens College Step Test (p. 113) Validated in 1972, r = 0.79, error + 8% 16.25in step for 3 min Different step cadences for males/females (96/88) Standing post exercise HR taken immediately Threats to validity/reliability/objectivity? Females: VO2 = 68.81 – (0.1847 x HR) Males: VO2 = 111.33 – (0.42 x HR)

Field Tests Fixed-distance tests Fixed-time tests 6-minute walk, 1993. 1 mile walk, 1987 (p. 115). r = 0.93 1 mile run 1.5 mile run Fixed-time tests Beep (multi-stage fitness) test 12-min run test, 1968 (p. 115). r = 0.9 Threats to validity/reliability/objectivity?

Submaximal Exercise Tests Submax tests rely on age-pred max HR MAXHR = 220 – age Indications for test termination based upon epidemiological data Monitoring HR BP EKG Box 7.3 – General Indications for Stopping an Exercise Test in Low-Risk Adults Onset of angina or angina like symptoms Drop in systolic BP of >10 mm HG from baseline BP despite an increase in workload Excessive rise in BP: systolic pressure >250 mm Hg or diastolic pressure >115 mm Hg Shortness of breath, wheezing, leg cramps, or claudication Signs of poor perfusion: light-headedness, confusion, ataxia, pallor, cyanosis, nausea, or cold and clammy skin Failure of heart rate to increase with increased exercise intensity Noticeable change in heart rhythm Subject requests to stop Physical or verbal manifestations of severe fatigue Failure of the testing equipment

Submaximal Exercise Test Treadmill – same test protocols (Bruce, Balke, etc…) Cycle Ergometer tests (YMCA Submax Bike Test) (p 121-126) 2-4 3-min stages based upon HR response to ex 50rpm pedal rate Stopped at 85% MAXHR/ <50RPM/request to stop/emerg. Prediction of VO2 can be graphed or calculated Graphing requires 2+hr points Calculation-based prediction requires “…calculating the slope of the HR and VO2 relationship….”

VO2 = [(1.8 x wr) / (kg)] + 7 YMCA Submax Bike Test Graphing the results…. Pt. A – 55y, 175lb, HR1 – 120, HR2 - 135 Pt. B – 30y, 215lb, HR1 – 130, HR2 - 165 Pt. C – 70y, 160lb, HR1 – 95, HR2 - 115 VO2 = [(1.8 x wr) / (kg)] + 7

Max vs Submax Standards are norm-based (population, gender, age) for both M & SM SEE (standard error of estimate) should be reported to the subject, if available for SM results Objective error caused by: Ergometer Age-predicted maxHR Subject’s mechanical efficiency for ergometer testing Submax HR variability HR/VO2 linearity **ExPhysRules Subjective causes of testing error?