Stress test treadmills and bikes are exercise machines used in tests that mostly measure cardiac and pulmonary responses to external stress, for early detection of coronary artery disease or to evaluate a patient's condition after a heart attack. For stress test treadmills, these are usually designed with ample space for stationary walking and running. Both are built to gradually increase or decrease acceleration, but are also equipped with an emergency stop. Some models are designed to work quietly, and ergonomically built to take in heavier patients. Stress test treadmills and bikes work in conjunction with ECG, EMG, ergospirometry, and BPM, and are essential components of a highly efficient stress test system.