Clinical Exercise Physiology Tests
Resting Energy Expenditure Measurement
Resting metabolic rate (RMR) is the amount of energy expended by the body to maintain vital physiological functions such as cardiovascular activities and respiration in the resting state. In sedentary individuals the RMR can account for 60-75% of daily energy expenditure. Resting energy expenditure (REE) is measured via indirect calorimetry. During the test, an individual's oxygen consumption and carbon dioxide production is measured at rest. Based on the direct relationship between O2 consumed and the amount of heat produced in the body, measuring O2 consumption provides an estimate of metabolic rate. Therefore, measurement of resting energy expenditure (REE) allows us to get a good estimate of a person's RMR.
Resting energy expenditure, being the largest component of total energy expenditure, is considered the most important to quantify. It can be used to calculate many things ranging from dietary needs of hospitalized patients to assisting in the development of treatment plans (weight management) for such populations as obese persons.
Metabolic Treadmill Exercise Tolerance Test
In a metabolic treadmill exercise test, the patient is asked to walk and/or jog on the treadmill for as long as they can. The most commonly used protocol is the Bruce protocol, in which the speed and incline of the treadmill are increased every three minutes. The patient's heart rhythm is monitored by an EKG (electrocardiogram) and ventilatory response is measured by a metabolic cart. The patient's blood pressure, symptoms and their rating of perceived exertion (RPE) are also monitored throughout the test. The test usually lasts between 8 and 12 minutes in the clinical setting. The interpretation and report upon its completion is referred to the patient's cardiologist or primary care physician.
The metabolic exercise tolerance test is used in clinical practice to assess a patient's exercise tolerance along with their cardiac, pulmonary, hemodynamic and symptomatic responses to exertion. Patients can be referred for an exercise stress test by their doctor for a variety of reasons, including:
- Chest pain
- Shortness of Breath
- Syncope (Fainting)
- Congenital Heart Defects
- Diagnosis of Cardiovascular Disease or Arrhythmias
Dual Energy X-ray Absorptiometry (DXA)
DXA uses two different X-ray beams to measure soft tissue and bone. While scanning, DXA directs alternating X-ray energy from two separate sources towards bone at a set frequency. These two sources of X-ray energy transmit bone density through a filter onto a photon counter that is part of the DXA machine. The greater the bone density, the stronger the signal picked up by the photon counter.
- Bone Densitometry
- Body Composition (total and regional)
- Monitoring response to drug therapy
- Pediatric Assessment
A simple, accurate, non-invasive, low-cost method of body composition testing which uses the measured amount of subcutaneous fat and regression equations to estimate percent body fat.
Skinfold measurements are used when other methods of body composition testing are impractical (cost, time, space, etc.). Measurements are taken at 7 sites on the body and the sum of skinfolds is put into one of several regression equations used to convert them to percent body fat. The accuracy of predicting percent fat from skinfolds is ~ +/- 3.5% with proper technique and equations.
YMCA Submaximal Bike Test
The YMCA protocol uses two to four 3-minute stages of continuous exercise of submaximal exercise. The test is designed to raise the steady-state heart rate (HR) of the subject to between 110 bpm and 85% of age-predicted maximal HR for at least two consecutive stages.
To determine HR response to several submaximal work rates and use the results to predict maximal oxygen uptake (VO2max). VO2max is a measure of cardiorespiratory fitness closely related to the functional capacity of the heart.
Pulmonary Function Tests
Pulmonary function tests (PFTs) are performed using a metabolic cart. The patient must maximally inhale and then exhale as quickly and forcefully as possible, creating a flow-volume loop. The data collected from the patient are then compared to the patient's predicted values based on their age, height, weight, etc.
PFTs are used to analyze a patient's lung function over time and assess the patient for any restrictive or obstructive pulmonary issues they may possess. PFTs measure the following values:
- FVC: total amount of air in a forceful exhalation after a maximal inhalation
- FEV1: volume of air exhaled in the first 1 second of maximal exhalation
- FEV1/FVC ratio
- FEF 25-75: forced expired flow between 25% and 75% FVC
- Peak flow: the highest expiratory flow rate during a forceful exhalation
Department of Health Sciences
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