Exercise Testing.

Abstract

Introduction Exercise testing (ET) can provide the clinician with valuable information for a variety of patient conditions. ET can be used to evaluate a patient with potential coronary artery disease (CAD) or cardiopulmonary symptoms and to determine the cardiac response to exercise of a patient with known cardiac or pulmonary disease (1). ET can guide a patient who wants to increase his/her physical activity, allow the physician to monitor the progress of a patient who is participating in an exercise program, and highlight ways to optimize performance for elite athletes who have set new goals (2). ET Method and Measurements Typical ET is done under the supervision of a physician or trained staff in a controlled environment. The patient exercises on a treadmill or cycle ergometer with a gradually increasing workload, while the team assesses his/her heart rate, blood pressure, electrocardiogram, ventilation, gas exchange, and/or lactate levels. ET and CAD ET is best for patients with an intermediate pretest probability of CAD (3). Testing patients outside of this risk increases the risk of false positives and negatives. The exercise treadmill score (i.e., Duke Treadmill Score), calculated after the exercise test, will provide the physician and patient with prognostic information (4). ET can assess capacity in those with a recent acute coronary event and help clinicians develop an appropriate exercise program. In this situation, the exercise test should be symptom-limited and completed with the patient on appropriate medication. If an exercise test is not available, cardiac rehabilitation may still be performed with modification ((5), page 233). ET and New American College of Sports Medicine Recommendations ET can be used to evaluate the risk of adverse outcomes from cardiovascular and pulmonary diseases prior to starting an exercise program. The new 2018 American College of Sports Medicine (ACSM) recommendations now focus on the patient's current level of physical activity; the presence of signs or symptoms of and/or known cardiovascular, metabolic, or renal disease; and the desired exercise intensity. The new recommendations have removed cardiovascular disease risk factors and the low-, moderate-, or high-risk classification. Specific ET is not required, but recommendations still call for medical clearance, and the medical professional can determine what medical tests or examinations are warranted ((5), page 22). ET and Exercise Prescription ET can help the clinician provide an individualized exercise prescription and improve future results. Exercise prescriptions can encourage patients to be more physically active. Exercise prescriptions should be written using the Frequency, Intensity, Time, Type, Volume, and Progression principle. Heart rate maximum (HRmax), obtained on a maximal, symptom-limited ET, can be used as a guide to set exercise intensity. ACSM recommends aiming for an exercise intensity between 55% and 90% HRmax. To improve cardiorespiratory fitness, most adults need to exercise at 70% to 85% of HRmax ((5), page 143). ET and Performance Improvement ET also can be used to maximize performance for competitive athletes. Although other protocols are available to evaluate this population, the Bruce protocol with gas exchange is the most frequently used test for athletes (6). ET for performance improvement is targeted at identifying the maximal oxygen uptake (V̇O2max) and lactate threshold and developing an appropriate training program. V̇O2max is a measure of the maximum volume of oxygen consumption, when a person is working at maximal capacity. V̇O2max, expressed as volume/minute, is calculated by measuring the inspired O2 and expired CO2 with increasing exercise intensity. V̇O2max is often normalized for body weight to allow comparisons between individuals. V̇O2max is affected by age, sex, training level, altitude, and chronic disease. Untrained healthy individuals are found to have a V̇O2max of 30 to 45 mL·kg−1·min−1, while elite aerobic athletes can attain levels greater than 80 mL·kg−1·min−1 (7). Lactate threshold (LT) is the point at which the blood lactate accumulation, the byproduct of glycolysis, exponentially exceeds its clearance rate, affecting performance. The LT represents the conversion of aerobic activity, which relies on oxidative phosphorylation for energy, to anaerobic or glycolytic energy production. LT is reported as a percentage of V̇O2max or HRmax. Identifying one's lactate threshold allows an athlete to train more efficiently and improve performance (8). ET Contraindications ET is generally contraindicated in patients with any acute or severe chronic cardiorespiratory disease causing marked functional impairment (e.g., acute myocardial infarction in the last 2 d, unstable angina, uncontrolled cardiac arrhythmias, symptomatic severe aortic stenosis, uncontrolled symptomatic heart failure, acute pulmonary embolus or pulmonary infarction, acute myocarditis or pericarditis, acute aortic dissection) (9). Conclusion ET helps the clinician diagnose CAD, evaluate a patient's prognosis or improvement with a regular exercise program, write an individualized exercise prescription, and guide competitive athletes to reach new goals.