Protocols used in TMT

a. Bruce Protocol :

Before the development of the Bruce Protocol there was no safe, standardized protocol that could be used to monitor cardiac function in exercising patients. Most physicians relied upon patients complaints about exertion, and examined them only at rest. To address these problems, Dr. Robert A. Bruce and Dr. Paul Yu began work on developing a treadmill exercise test. The test made extensive use of relatively new technological developments in electrocardiographs and motorized treadmills.

A  Bruce exercise test involved walking on a treadmill while the heart was monitored by an electrocardiograph with various electrodes attached to the body. Ventilation volumes and respiratory gas exchanges were also monitored, before, during and after exercise. Because the treadmill speed and inclination could be adjusted, this physical activity was tolerated by most patients. Initial experiments involved a single-stage test, in which subjects walked for 10 minutes on the treadmill at a fixed workload. Bruce analyzed minute-by-minute changes in respiratory and circulatory function of normal adults and patients with heart or lung ailments. Later he developed the multistage test, consisting of several stages of progressively greater workloads. It was this multistage test, which later became known as the Bruce protocol. In the initial experiment, Bruce reported that the test could detect signs of such conditions as angina pectoris, a previous heart attack, or a ventricular aneurysm. Bruce also demonstrated that exercise testing was useful in screening apparently healthy people for early signs of coronary artery disease .

Typically during a Bruce Protocol, Heart Rate (HR) is taken every minute and BP is taken at the end of each stage (every three minutes). However institutions often vary this procedure slightly.

The Bruce Treadmill Test Protocol
Level	Time (mins)	Speed (km/hr)	Gradient (%)
1	0	2.74	10
2	3	4.02	12
3	6	5.47	14
4	9	6.76	16
4	12	8.05	18
5	15	8.85	20
6	18	9.65	22

Table 1- The Bruce treadmill test protocol showing different levels with its respective time interval, speed and gradient

So, from the chart above, we see that the test starts at 2.7 km/hr at a gradient or incline of 10%. At minute 3 the speed is increased to 4.02km/hr and the gradient increased to 12%. This is a maximal test which means that the individual must continue until fatigued .Needless to say in a clinical setting; other parameters (such as blood pressure and ECG readings etc.) are used to determine the end of the test . Today, the Bruce Protocol is also one common method for estimating VO₂ maximum in athletes. VO₂ maximum, or maximal oxygen uptake, is one factor that can determine an athlete’s capacity to perform sustained exercise and is linked to aerobic endurance. VO₂ maximum refers to the maximum amount of oxygen that an individual can utilize during intense or maximal exercise. It is measured as “ milliliters of oxygen used in one minute per kilogram of body weight”(ml/kg/min).The Bruce treadmill test is an indirect test that estimates VO₂ maximum using a formula rather than using direct measurements that require the collection and measurement of the volume and oxygen concentration of inhaled and exhaled air. This determines how much oxygen the athlete is using. The length of time on the treadmill is the test score and can be used to estimate the VO₂ maximum value . The Bruce Protocol Formula for estimating VO₂ maximum:

·                     For Men, VO₂ maximum=14.8-(1.379*T)-(0.012*T)

·                     For Women, VO₂ maximum=4.38*T-3.9

Where, T=Total time on the treadmill measured as a fraction of a minute (i.e: A test time of 9 minutes would be written as T=9.5).

Men
Age	Very Poor	Poor	Fair	Good	Excellent	Superior
13-19	<35.0	35.0-38.3	38.4-45.1	45.2-50.9	51.0-55.9	>55.9
20-29	<33.0	33.0-36.4	36.5-42.4	42.5-46.4	46.5-52.4	>52.4
30-39	<31.5	31.5-35.4	35.5-40.9	41.0-44.9	45.0-49.4	>49.4
40-49	<30.2	30.2-33.5	33.6-38.9	39.0-43.7	43.8-48.0	>48.0
50-59	<26.1	26.1-30.9	31.0-35.7	35.8-40.9	41.0-45.3	>45.3
60+	<20.5	20.5-26.0	26.1-32.2	32.3-36.4	36.5-44.2	>44.2

Table 2- The Bruce Protocol Norms for Men (in ml/kg/min)

b.   Balke Protocol:

Balke Protocol has been used to monitor the development of the athlete’s general endurance (VO₂ maximum). In this, athlete walks on a treadmill to exhaustion. At timed stages during the test the gradient of slope (%) of the treadmill is increased as follows .

 Active and sedentary men:

o        Treadmill speed set at 3.3 mph

o        Start –Gradient is 0%

o        After 1 minute-Gradient set at 12%

o        After 2 minutes and each minute thereafter the gradient is increased by 1 %

Active and sedentary women:

o        Treadmill speed set at 3.0 mpg

o        Start-Gradient is 0%

o        After 3 minutes and every 3 minutes thereafter the gradient is increased by 2.5%

The assistant starts the stop watch at the start of the test and stops it when the athlete is unable to continue –this ideally should be between 9 and 15 minutes. From the total time an estimate of the athlete‘s VO₂ maximum can be calculated as follows:

VO₂ maximum=1.44*T+14.99(for active and sedentary men)

VO₂ maximum=1.38*T+5.22(for Active and sedentary women)

Where, “T” is the total time of the test expressed in minutes and fractions of a minute.