Bruce protocol

Last updated
Bruce protocol
RIAN archive 555848 Testing on treadmill.jpg
Treadmill for functional diagnostics for competitive athletes (1980)
Purposeevaluate cardiac function
Test of Cardiac stress test

The Bruce protocol is a standardized diagnostic test used in the evaluation of cardiac function and physical fitness, developed by American cardiologist Robert A. Bruce. [1]

Contents

According to the original Bruce protocol the patient walks on an uphill treadmill in a graded exercise test with electrodes on the chest to monitor. Every 3 min the speed & incline of the treadmill are increased. [2] There are 7 such stages and only very fit athletes can complete all 7 stages. The modified Bruce Protocol is an alteration in the protocol so that the treadmill is initially horizontal rather than uphill, with the 1st few intervals increasing the treadmill slope only. [3]

The Bruce treadmill test estimates maximum oxygen uptake using a formula and the performance of the subject on a treadmill as the workload is increased. The test is easy to perform in a medical office setting, does not require extensive training or expensive equipment, and it has been validated as a strong predictor of clinical outcomes. [4]

Procedure

Exercise is performed on a treadmill. The leads of the ECG are placed on the chest wall. The treadmill is started at 2.74 km/h (1.7mph) & at an inclined gradient of 10%. After 3 min incline of the treadmill is increased by 2%, and the speed increases. Indications to terminate the test include signs or symptoms of impaired blood flow to the heart, irregular heart rhythm, fatigue, shortness of breath, wheezing, leg cramps, or any impairment in walking or pain, discomfort, numbness, or tiredness in the legs. [5]

Stages

Stages of the standard Bruce protocol are as follows: [5]

StageMinutes % grade MPHmin/mile km/h min/km METSm/s
13101.735:182.722:1330.75
23122.524:004.015:004-51.11
33143.417:395.510:5571.52
43164.214:176.88:49101.89
53185.012:008.07:30142.22
63205.510:558.96:44172.47
73226.010:009.76:11212.69

Total Duration = 21 minutes

History

Before the development of the Bruce protocol there was no safe, standardized protocol that could be used to monitor cardiac function in exercising patients. Master's two-step test [6] was often used, but it was too strenuous for many patients, and inadequate for the assessment of respiratory and circulatory function during varying amounts of exercise.

To address these problems, Bruce and his colleagues began to develop a cardiac stress test. The test made extensive use of relatively new technological developments in electrocardiograph machines and motorized treadmills. The Bruce exercise test involved walking on a treadmill while the heart was monitored by an electrocardiograph with various electrodes attached to the body. Breathing volumes and respiratory gas exchange 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's first reports on treadmill exercise tests, published in 1949, analyzed minute-by-minute changes in respiratory and circulatory function of normal adults and patients with heart or lung disease. [7] [8]

In 1950 Bruce joined the University of Washington, where he continued research on the single-stage test, particularly as a predictor of the success of surgery for valvular or congenital heart disease. Later he developed a multistage test, consisting of several stages of progressively greater workloads. It was this multistage test — a description of which was first published in 1963 — that became known as the Bruce Protocol. In the initial paper, Bruce reported that the test could detect signs of such conditions as angina pectoris, a previous heart attack, or a ventricular aneurysm. Bruce and his colleagues also demonstrated that exercise testing was useful in screening apparently healthy people for early signs of coronary artery disease.[ citation needed ]

Typically during a Bruce Protocol, heart rate and rating of perceived exertion are taken every minute and blood pressure is taken at the end of each stage (every three minutes). There are Bruce protocol tables available for maximal (competitive athletes) and sub-maximal (non-athletic people) efforts.[ citation needed ]

Modifications

The Modified Bruce protocol starts at a lower workload than the standard test and is typically used for elderly or sedentary patients. The first two stages of the Modified Bruce Test are performed at a 1.7 mph and 0% grade and 1.7 mph and 5% grade, and the third stage corresponds to the first stage of the Standard Bruce Test protocol as listed above.[ citation needed ]

Results

The test score is the time taken on the test, in minutes. This can also be converted to an estimated maximal oxygen uptake score using the calculator below and the following formulas, where the value "T" is the total time completed (expressed in minutes and fractions of a minute e.g. 9 minutes 15 seconds = 9.25 minutes). As with many exercise test equations, there have been many regression equations developed that may give varying results. If possible, use the one derived from a similar population and which best suits your needs.[ citation needed ]

ref: ACSM's Health-Related Physical Fitness Assessment Manual

Underlying Heart Rate Formulas

Maximum heart rate (MHR) is often calculated with the formula 220-age, which is quite inaccurate.[ citation needed ] The heart rate formula most often used for the Bruce is the Karvonen formula (below).

A more accurate formula, offered in a study published in the journal, Medicine & Science in Sports & Exercise, is 206.9 - (0.67 x age) which can also be used to more accurately determine VO2 Max, but may produce significantly different results.[ citation needed ]

A diagnostician (e.g., physical therapist, personal trainer, doctor, athletic trainer, nurse, medical professional, dietitian, etc.) may be best served to conduct the test twice using both parameters and formulas.

Karvonen method

The Karvonen method factors in resting heart rate (HRrest) to calculate target heart rate (THR), using a range of 50–85% intensity: [9]

THR = ((HRmax − HRrest) × %Intensity) + HRrest

Example for someone with a HRmax of 180 and a HRrest of 70:

Related Research Articles

<span class="mw-page-title-main">Lung volumes</span> Volume of air in the lungs

Lung volumes and lung capacities refer to the volume of air in the lungs at different phases of the respiratory cycle.

<span class="mw-page-title-main">Heart rate</span> Speed of the heartbeat, measured in beats per minute

Heart rate is the frequency of the heartbeat measured by the number of contractions of the heart per minute. The heart rate varies according to the body's physical needs, including the need to absorb oxygen and excrete carbon dioxide. It is also modulated by numerous factors, including genetics, physical fitness, stress or psychological status, diet, drugs, hormonal status, environment, and disease/illness, as well as the interaction between these factors. It is usually equal or close to the pulse measured at any peripheral point.

Jack Tupper Daniels is an American exercise physiologist, running coach and a coach of Olympic athletes. On March 21, 2013, he was named the head coach of the Wells College men's and women's cross country programs. He received his doctoral degree in exercise physiology at the University of Wisconsin–Madison. Named "The World's Best Coach" by Runner's World magazine, he led SUNY Cortland runners to eight NCAA Division III National Championships, 31 individual national titles, and more than 130 All-America awards. Daniels outlined his training philosophies in the 1998 book, Daniels' Running Formula. He mentors and coaches some of America's top distance runners in the country.

<span class="mw-page-title-main">Cardiac stress test</span> Measures the hearts ability to respond to external stress in a controlled clinical environment

A cardiac stress test is a cardiological examination that evaluates the cardiovascular system's response to external stress within a controlled clinical setting. This stress response can be induced through physical exercise or intravenous pharmacological stimulation of heart rate.

The cooper test which was designed by Kenneth H. Cooper in 1968 for US military use is a physical fitness test. In its original form, the point of the test is to run as far as possible within 12 minutes. Pacing is important, as the participant will not cover a maximal distance if they begin with a pace too close to an all out sprint. The outcome is based on the distance the test person ran, their age and their sex.

V̇O2 max (also maximal oxygen consumption, maximal oxygen uptake or maximal aerobic capacity) is the maximum rate of oxygen consumption attainable during physical exertion. The name is derived from three abbreviations: "V̇" for volume (the dot over the V indicates "per unit of time" in Newton's notation), "O2" for oxygen, and "max" for maximum and usually normalized per kilogram of body mass. A similar measure is V̇O2 peak (peak oxygen consumption), which is the measurable value from a session of physical exercise, be it incremental or otherwise. It could match or underestimate the actual V̇O2 max. Confusion between the values in older and popular fitness literature is common. The capacity of the lung to exchange oxygen and carbon dioxide is constrained by the rate of blood oxygen transport to active tissue.

<span class="mw-page-title-main">Exercise intensity</span>

Exercise intensity refers to how much energy is expended when exercising. Perceived intensity varies with each person. It has been found that intensity has an effect on what fuel the body uses and what kind of adaptations the body makes after exercise. Intensity is the amount of physical power that the body uses when performing an activity. For example, exercise intensity defines how hard the body has to work to walk a mile in 20 minutes.

<span class="mw-page-title-main">High-intensity interval training</span> Exercise strategy

High-intensity interval training (HIIT) is a training protocol alternating short periods of intense or explosive anaerobic exercise with brief recovery periods until the point of exhaustion. HIIT involves exercises performed in repeated quick bursts at maximum or near maximal effort with periods of rest or low activity between bouts. The very high level of intensity, the interval duration, and number of bouts distinguish it from aerobic (cardiovascular) activity, because the body significantly recruits anaerobic energy systems. The method thereby relies on "the anaerobic energy releasing system almost maximally".

The metabolic equivalent of task (MET) is the objective measure of the ratio of the rate at which a person expends energy, relative to the mass of that person, while performing some specific physical activity compared to a reference, currently set by convention at an absolute 3.5 mL of oxygen per kg per minute, which is the energy expended when sitting quietly by a reference individual, chosen to be roughly representative of the general population, and thereby suited to epidemiological surveys. A Compendium of Physical Activities is available online, which provides MET values for hundreds of activities.

Cardiorespiratory fitness (CRF) refers to the ability of the circulatory and respiratory systems to supply oxygen to skeletal muscles during sustained physical activity. Scientists and researchers use CRF to assess the functional capacity of the respiratory and cardiovascular systems. These functions include ventilation, perfusion, gas exchange, vasodilation, and delivery of oxygen to the body's tissues. As these body's functions are vital to an individual's health, CRF allows observers to quantify an individual's morbidity and mortality risk as a function of cardiorespiratory health.

Interval training is a type of training exercise that involves a series of high-intensity workouts interspersed with rest or break periods. The high-intensity periods are typically at or close to anaerobic exercise, while the recovery periods involve activity of lower intensity. Varying the intensity of effort exercises the heart muscle, providing a cardiovascular workout, improving aerobic capacity and permitting the person to exercise for longer and/or at more intense levels.

<span class="mw-page-title-main">Robert A. Bruce</span> American cardiologist

Robert Arthur Bruce was an American cardiologist and a professor at the University of Washington. He was known as the "father of exercise cardiology" for his research and development of the Bruce Protocol.

Second wind is a phenomenon in endurance sports, such as marathons or road running, whereby an athlete who is out of breath and too tired to continue, finds the strength to press on at top performance with less exertion. The feeling may be similar to that of a "runner's high", the most obvious difference being that the runner's high occurs after the race is over. In muscle glycogenoses, an inborn error of carbohydrate metabolism impairs either the formation or utilization of muscle glycogen. As such, those with muscle glycogenoses do not need to do prolonged exercise to experience "hitting the wall". Instead, signs of exercise intolerance, such as an inappropriate rapid heart rate response to exercise, are experienced from the beginning of an activity, and some muscle GSDs can achieve second wind within about 10 minutes from the beginning of the aerobic activity, such as walking. (See below in pathology).

Continuous Training is a form of exercise that is performed at a continuous intensity throughout and doesn't involve any rest periods. Continuous training typically involves aerobic activities such as running, cycling, swimming, and rowing. rest intervals. Continuous training can be performed at low, moderate, or high exercise intensities, and is often contrasted with interval training, often called high-intensity interval training. Some training regimens, such as Fartlek, combine both continuous and interval approaches.

<span class="mw-page-title-main">Transfusion-associated circulatory overload</span> Medical condition

In transfusion medicine, transfusion-associated circulatory overload is a transfusion reaction resulting in signs or symptoms of excess fluid in the circulatory system (hypervolemia) within 12 hours after transfusion. The symptoms of TACO can include shortness of breath (dyspnea), low blood oxygen levels (hypoxemia), leg swelling, high blood pressure (hypertension), and a high heart rate (tachycardia).

vV̇O2max (velocity at maximal oxygen uptake), also known as maximal aerobic speed (MAS), is an intense running or swimming pace. This is the minimum speed for which the organism's maximal oxygen uptake (VO2 max) is reached, after a few minutes of constantly maintaining this exercise intensity. At higher paces, any additional increase in power is provided by anaerobic processes. In an incremental exercise test, it is the first speed at which any increase in exercise intensity fails to elicit an increase in oxygen consumption.

<span class="mw-page-title-main">Metabolic myopathy</span> Type of myopathies

Metabolic myopathies are myopathies that result from defects in biochemical metabolism that primarily affect muscle. They are generally genetic defects that interfere with muscle's ability to create energy, causing a low ATP reservoir within the muscle cell.

In kinesiology, the ventilatory threshold (VT1) refers to the point during exercise at which ventilation starts to increase at a faster rate than VO2 (V – volume, O2 – oxygen). One's threshold is said to reflect levels of anaerobiosis and lactate accumulation. As the intensity level of the activity being performed increases, breathing becomes faster; more steadily first and then more rapid as the intensity increases. When breathing surpasses normal ventilation rate, one has reached ventilatory threshold. For most people this threshold lies at exercise intensities between 50% and 75% of VO2 max. A major factor affecting one's ventilatory threshold is their maximal ventilation (amount of air entering and exiting lungs). This is dependent on their personal experience with the activity and how physically fit the person is. Comparison studies of more athletic people have shown that your ventilatory threshold occurs at a higher intensity if you are more active or have been training for that exercise; although, in some cases shorter continuous tests can be used because of rapid alterations in ventilation.

The physiology of marathons is typically associated with high demands on a marathon runner's cardiovascular system and their locomotor system. The marathon was conceived centuries ago and as of recent has been gaining popularity among many populations around the world. The 42.195 km distance is a physical challenge that entails distinct features of an individual's energy metabolism. Marathon runners finish at different times because of individual physiological characteristics.

Duke Treadmill Score is one of the tools for predicting the risk of ischemia or infarction in the heart muscle. The calculation is done based on the information obtained from an exercise test by this formula:

References

  1. Kennedy JW, Cobb LA, Samson WE (10 May 2005). "Robert Arthur Bruce, MD: 1916–2004". Circulation. 111 (18): 2410–2411. doi: 10.1161/01.CIR.0000164274.41137.75 . PMID   16389672.
  2. Bruce, RA (December 1971). "Exercise testing of patients with coronary heart disease. Principles and normal standards for evaluation". Annals of Clinical Research. 3 (6): 323–32. PMID   5156892.
  3. Sheffield, L.Thomas; Roitman, David (July 1976). "Stress testing methodology". Progress in Cardiovascular Diseases. 19 (1): 33–49. doi:10.1016/0033-0620(76)90007-4. PMID   785541.
  4. Kelly, Jacob P.; Andonian, Brian J.; Patel, Mahesh J.; Huang, Zhen; Shaw, Linda K.; McGarrah, Robert W.; Borges-Neto, Salvador; Velazquez, Eric J.; Kraus, William E. (April 2019). "Trends in Cardiorespiratory Fitness: The Evolution of Exercise Treadmill Testing at a Single Academic Medical Center from 1970 to 2012". American Heart Journal. 210: 88–97. doi:10.1016/j.ahj.2019.01.001. PMC   6441626 . PMID   30743212.
  5. 1 2 Fletcher, Gerald F.; Ades, Philip A.; Kligfield, Paul; Arena, Ross; Balady, Gary J.; Bittner, Vera A.; Coke, Lola A.; Fleg, Jerome L.; Forman, Daniel E.; Gerber, Thomas C.; Gulati, Martha; Madan, Kushal; Rhodes, Jonathan; Thompson, Paul D.; Williams, Mark A. (20 August 2013). "Exercise Standards for Testing and Training: A Scientific Statement From the American Heart Association". Circulation. 128 (8): 873–934. doi:10.1161/CIR.0b013e31829b5b44. PMID   23877260.
  6. Master, Arthur M. (April 1935). "The two-step test of myocardial function". American Heart Journal. 10 (4): 495–510. doi:10.1016/S0002-8703(35)90218-6.
  7. Robert A. Bruce; Frank W. Lovejoy Jr.; Raymond Pearson; Paul N. G. Yu; George B. Brothers; Tulio Velasquez (1949). "Normal respiratory and circulatory pathways of adaptation in exercise". J Clin Invest. 28 (6 Pt 2): 1423–30. doi:10.1172/JCI102207. PMC   439698 . PMID   15407661.
  8. Robert A. Bruce; Raymond Pearson; Frank W. Lovejoy Jr.; Paul N. G. Yu; George B. Brothers (1949). "Variability of respiratory and circulatory performance during standardized exercise". J Clin Invest. 28 (6 Pt 2): 1431–8. doi:10.1172/JCI102208. PMC   439699 . PMID   15395945.
  9. Karvonen J, Vuorimaa T (May 1988). "Heart rate and exercise intensity during sports activities. Practical application". Sports Medicine. 5 (5): 303–11. doi:10.2165/00007256-198805050-00002. PMID   3387734. S2CID   42982362.