Modified Bruce Protocol
Standard Bruce protocol for treadmill exercise test has 7 three minute stages. First stage starts at a speed of 1.7 miles per hour (mph) and a gradient of 10%. Each subsequent stage has an increment of 0.7 to 0.8 mph in speed and 2% in gradient. Modified Bruce protocol starts with a speed of 1.7 mph and a gradient of 0%. Second and third stages have the same speed, but the gradient increase by 5%. Third stage of modified Bruce protocol is thus equivalent to stage 3 of standard Bruce protocol. Further stages are just like that of subsequent stages of standard Bruce protocol. Earlier the first two stages of modified Bruce protocol were called stage 0 and stage 1/2 because the gradient was zero in the first stage and half of that of stage one in second stage.
Modified Bruce protocol for treadmill testing is usually applied when poor condition of the subject is suspected clinically or while conducting a predischarge treadmill test after treatment for acute myocardial infarction. Pre discharge treadmill test is often a sign limited one unlike the symptom limited test done in other situations. Maximum heart rate aimed at is around 120 per minute, unlike the 220-age maximum predicted heart rate for the standard treadmill test.