What is the protocol for treadmill stress testing?

Updated: Nov 21, 2018
  • Author: David Akinpelu, MD, FACP; Chief Editor: Eric H Yang, MD  more...
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Answer

Exercise capacity is reported in terms of estimated metabolic equivalents of task (METs). The MET unit reflects the resting volume oxygen consumption per minute (VO2) for a 70-kg, 40-year-old man, with 1 MET equivalent to 3.5 mL/min/kg of body weight.

In the standard Bruce protocol, the starting point (ie, stage 1) is 1.7 mph at a 10% grade (5 METs). Stage 2 is 2.5 mph at a 12% grade (7 METs). Stage 3 is 3.4 mph at a 14% grade (9 METs). This protocol includes 3-minute periods to allow achievement of a steady state before workload is increased.

The modified Bruce protocol has 2 warmup stages, each lasting 3 minutes. The first is at 1.7 mph and a 0% grade, and the second is at 1.7 mph and a 5% grade. This protocol it is most often used in older individuals or those whose exercise capacity is limited by cardiac disease.

The Bruce protocol has larger increments between stages than do other protocols, such as the Naughton, Weber, and Asymptomatic Cardiac Ischemia Pilot (ACIP) study protocols, all of which start with less than 2 METs at 2 mph and increase in 1- to 1.5-MET increments between stages.

Other exercise protocols include bicycle and arm ergometry, both of which are used less often in North America than treadmill stress testing is. The bicycle ergometer has the advantage of requiring less space than a treadmill. It is quieter, permits sensitive precordial measurements without much motion artifact, and is generally safer because the risk of falling from the machine is lower.


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