A MET unit is the energy expenditure at rest, equivalent to an oxygen uptake of approximately 3.5 mL O 2 per kilogram bodyweight per minute. This is the most precise measurement of metabolic load, and therefore cardiovascular load, and can vary considerably between individuals with differing exercise efficiency working at the same treadmill or cycle ergometer setting. Treadmills must be motorised and calibrated, and should be capable of providing measured increases in speed and gradient. Treadmill inclination can be checked by a protractor. Cycle ergometers must be able to vary the external workload and quantify it in watts.
Preference is for electrical or mechanical braking, although wind-braking is probably adequate.
Thumb-screw braking is not adequate as the load cannot be quantified and is not reproducible. Equipment should be serviced on a regular basis to ensure performance within specifications. Devices which record only one or three ECG leads, even if these are bipolar chest leads, are not adequate. If the device provides computer-averaged complexes, raw ECG traces should also be inspected at each stage of exercise, or at least every three minutes, to avoid incorrect interpretation resulting from noise or artefact. Electrodes must be firmly fixed to the patient's skin with adhesive or continuous suction, and have good contact with the ECG lead, to prevent movement artefact in the ECG trace.