What Is an Exercise Stress Test (Treadmill Test)? Who Should Have This Test?

The exercise stress test (treadmill) is a basic cardiovascular examination method that measures the heart’s rhythm, working capacity, and overall performance during physical activity on a treadmill with computer assistance. It is mainly applied to people who feel pressure in the chest area, experience unusual shortness of breath while moving, or have palpitations of unknown cause. Many circulatory problems can remain hidden in the body without causing any symptoms while the human body is completely at rest. By creating a load on the heart similar to the one experienced during daily activity in a safe environment, the heart’s responses to this stress are observed. In this way, possible circulatory problems that have not yet negatively affected daily life can be detected early.

What Is an Exercise Stress Test (Treadmill) Basically and How Does It Affect Our Heart?

The heart is a unique and resilient organ that works continuously throughout human life and can adjust its pumping rate within seconds according to the body’s immediate needs. In order to maintain this uninterrupted function, its own heart muscle tissue also requires a regular supply of fresh oxygen and blood. The exercise stress test is a test method designed to evaluate how the heart manages this blood supply and energy balance at the cellular and electrical levels. It is based on the patient walking on a well-equipped and safe treadmill within a specific program that complies with international medical standards. As the duration of the test progresses, the speed and upward incline of the treadmill are automatically increased gradually. This mechanical increase causes the leg and arm muscles in the body to demand more energy. To meet this increased circulatory demand, the heart begins to contract increasingly faster and more forcefully. Throughout this entire fatigue process, the person’s instantaneous heart rhythm, electrical activity, and blood pressure values are monitored and recorded in computer systems. In this way, the heart’s overall capacity under challenging conditions is mapped in detail.

Why Do We Request an Exercise Stress Test (Treadmill) Instead of Only Performing a Normal ECG?

A normal result on a standard ECG performed while lying on a stretcher in the emergency department or during a routine health check does not necessarily mean that there is no blockage in the heart vessels. While a person is resting in bed or lying on an examination table, the heart’s energy requirement is at its lowest level. Even if there is severe narrowing in the arteries supplying the heart from the outside, the very small amount of blood required for the low work rate at that moment can easily pass through that thin narrowed area. Therefore, no deterioration or abnormality is observed on the ECG tracing recorded at that moment. This situation can be compared to a narrow road with two lanes closed where traffic flows easily late at night when the number of vehicles decreases. However, when the same person begins intense physical activity, that vascular pathway cannot meet the increased demand for blood flow, just like heavy vehicle traffic in the morning, and signs of a crisis rapidly appear. While a standard resting ECG cannot detect this hidden blockage, dangerous narrowings are easily revealed by deliberately increasing the heart’s workload on the treadmill.

How Does Our Heart Meet the Increased Oxygen Demand During an Exercise Stress Test (Treadmill)?

When the human body begins to move and exert extra effort, the circulatory network rapidly adapts mechanically to this new situation. As the walking pace gradually increases, the person’s heart rate rises, blood pressure increases in a balanced manner, and the amount of blood pumped by the heart to the tissues with each beat increases. In order for the heart muscle to maintain this high pace without becoming fatigued, it naturally requires much more oxygen than it does at rest. In a healthy vascular structure, the coronary arteries surrounding the heart relax, stretch, and widen their lumens to immediately meet this increased need for oxygen and nutrients. Thanks to these widened arteries, the amount of fresh blood reaching the heart tissues can increase to several times its normal value without difficulty. The balance mechanism between the high amount of oxygen demanded by the heart and the powerful blood supply provided by the blood vessels works perfectly in people without structural problems. Since the heart of a healthy individual walking and sweating on the treadmill can immediately receive the nutrients it needs, it does not experience an energy crisis, and the walking process ends only with a natural feeling of fatigue in the skeletal muscles.

How Does an Exercise Stress Test (Treadmill) Reveal Narrowing in the Heart Vessels?

Serious structural narrowings caused over the years by cholesterol plaque accumulation or calcification in the coronary vessels surrounding and supplying the heart cause the vessels to lose their ability to stretch and widen instantly. When the person begins the test and the incline of the device increases, the heart attempts to pump more blood in response to the commands coming from the muscles. However, narrowed, hardened, and calcified vessels cannot expand. At that moment, the heart tissue cannot receive enough oxygen for its own needs, and regional nutritional insufficiency occurs in its walls. The metabolism of muscle cells deprived of oxygen becomes impaired, and cellular fatigue waste products rapidly begin to accumulate. This cellular crisis directly disrupts the heart’s electrical conduction network. Special curves, directional changes, or irregularities that signal disease begin to appear in the ECG waves on the computer screen. This biochemical deterioration is reflected second by second on the graphs during the procedure, providing critical clues to the specialists performing the evaluation about the extent of the narrowing in the vessels and the degree of damage caused to the tissue.

Which People with Which Complaints Should Definitely Undergo an Exercise Stress Test (Treadmill)?

Sudden reactions of the body during ordinary physical activities in daily life may be the first signs of silently developing heart diseases. This test is frequently preferred in medicine as the first step in investigating the origin of these disturbing complaints. Specific pains felt while walking uphill or climbing stairs, jogging at a light pace, or carrying a heavy bag should be taken seriously.

The main complaints for which the procedure is decided are as follows:

• Pressure in the center of the chest
• Burning in the chest
• Pain radiating to the back
• Aching spreading to the jaw
• Numbness in the left arm
• Shortness of breath
• Abnormal palpitations
• Unexplained sweating
• Easy fatigue

Even if such complaints completely disappear within a few minutes when the person rests, they should not be ignored because they may indicate an underlying narrowing in a heart vessel. The data obtained from the walking test are highly valuable for medically proving the direct relationship between the complaints and exertion.

Should Individuals Without Complaints Also Undergo an Exercise Stress Test (Treadmill) for Check-Up Purposes?

People who enjoy movement, exercise regularly, or have no physical complaints do not always need to undergo routine heart screening on a treadmill. However, there are also special medical conditions in which vascular diseases may progress silently without causing complaints or stimulating pain mechanisms. Some individuals may not feel the narrowing in their vessels. When risk factors accumulate over the years, even people who appear generally healthy may harbor undiagnosed hidden problems.

The risk groups recommended to undergo evaluation even if they show no symptoms are as follows:

• Patients with diabetes
• People with high blood pressure
• People with high cholesterol
• Smokers
• People with obesity
• People with a sedentary lifestyle
• People with a family history of heart attack

This screening method may be used to evaluate the heart’s endurance under stress in people who carry these factors or in older individuals who are about to begin strenuous exercise for the first time.

How Does an Exercise Stress Test (Treadmill) Proceed in People Who Previously Had a Stent or Bypass Surgery?

Lifelong follow-up is extremely important for patients who have undergone surgical or balloon treatment due to vascular blockages. The health monitoring of patients whose blocked vessels were treated with stent placement through angiography or who had new vascular pathways created around the blocked area through open-heart surgery does not end with discharge from the hospital. Over time, there is always a possibility that narrowing may develop again inside the lumens of metal or drug-eluting stents or in the newly connected vascular grafts. One of the most practical ways to detect this mechanical condition at a very early stage without any adverse symptoms is again the same test. This follow-up performed a certain period after treatment is preferred to evaluate the quality of the procedures performed and the success of the vessels in remaining open. If the patient’s endurance time on the treadmill has increased and no ECG deviation is detected during the test, it is understood that the heart is once again being supplied adequately, and the medication doses are continued in the same manner.

Why Is an Exercise Stress Test (Treadmill) Requested Before Major Surgeries?

Major surgical operations planned for other organs or bones of the body that are completely unrelated to the heart place a very serious burden on the overall circulatory system. The effects of anesthesia lasting for hours, possible bleeding, sudden changes in body fluids, and the stress caused by surgery in the tissues force the heart to exert much more effort on the operating table than it does during normal daily life. Knowing before surgery whether the heart can withstand this difficult physiological load is a critically important safety step for the overall safety of the operation. Before major joint prosthesis procedures, advanced abdominal surgery, or cancer surgery, the condition of the patient’s cardiac capacity is necessarily tested through exertion. In patients who cannot climb stairs or become breathless even during short walks, the risk of a heart attack that the upcoming major surgery may create on the operating table is calculated by reviewing the treadmill findings. If the risk is found to be high, the surgical operation is postponed and priority is given to the heart.

How Should Nutrition and Preparation Be Before an Exercise Stress Test (Treadmill)?

In order to obtain accurate, clear medical results that have not been distorted by external factors, careful attention should be paid to eating habits before the test time. Taking the patient to the test on a completely empty stomach is an undesirable approach because intense energy expenditure may cause blood sugar to fall to dangerous levels and lead to fainting. However, walking on the treadmill with an overly full stomach may also cause digestive problems such as severe nausea or cramps during exercise. At the same time, because a large portion of circulating blood is directed to the digestive system after a meal, it may inaccurately reflect the heart’s performance during the test. For these reasons, it is most appropriate to consume a light meal that does not strain digestion approximately two to three hours before the procedure.

The foods that should be avoided immediately before the test for an accurate ECG measurement are as follows:

• Tea
• Coffee
• Energy drinks
• Chocolate
• Carbonated soft drinks

The substances contained in these foods may artificially alter ECG results and impair the clarity of the diagnosis.

How Should Clothing Selection and Physical Preparation Be on the Day of the Exercise Stress Test (Treadmill)?

Since the exertion begins with a slow walk on the device and gradually turns into a light run as the duration increases, choosing textile products that do not restrict the muscles improves the quality of the procedure. Tight jeans, classic suits, or everyday shoes with high soles that are preferred in daily life both endanger the safety of the test in terms of falling and limit exertion, thereby reducing the quality of the test. It is highly advisable for individuals undergoing the test to choose flexible clothing that allows comfortable movement and sports shoes with non-slip soles. For women, arriving in a two-piece outfit consisting of separate upper and lower garments provides practicality so that the cables and adhesive electrodes can be positioned correctly on the chest during the procedure. In men, it is critically important that the electrodes attached to the chest surface do not separate from the skin due to sweating during running. Shaving the chest hair immediately before the procedure, as it prevents these medical devices from making perfect contact with the skin, is a necessary preparation for obtaining a clear graph without electrical interference on the device screen.

How Can the Medications You Use Affect the Result of an Exercise Stress Test (Treadmill)?

Many medications taken regularly every day to balance blood pressure or protect the heart fundamentally have properties that suppress the heart rhythm, reduce the force of contraction, or relax the vascular pathways. The purpose of these medical products is to strain the heart as little as possible and protect it in daily life. The exercise stress test, on the other hand, seeks to determine to what extent the heart can naturally be pushed to its limits and how it responds to a blockage. If certain medications that forcibly prevent the heart from speeding up are not discontinued before the test, no matter how fast the treadmill becomes, the patient’s heart rate may never reach the critical value required for diagnosis. This contradiction may completely conceal true ischemia in the heart, meaning the inability to receive adequate nourishment, and produce a misleadingly normal result. On the other hand, it may be considered appropriate to continue certain hypertension medications on the morning of the procedure in order to control dangerous increases in blood pressure during the test. Therefore, which medications should be discontinued one day in advance is planned beforehand through clinical evaluation.

Why Are Exercise Stress Test (Treadmill) Results Evaluated Differently in Women?

The diagnostic ability of medical examination methods may sometimes demonstrate different accuracy rates in the female body and male physiology. This interesting misleading effect of sex-related characteristics is also frequently experienced in routine measurements performed using an exercise treadmill. The thinner vascular structures of women, hormonal fluctuations that change with monthly cycles, and the cellular characteristics of ECG patterns contain microscopic differences compared with men. When all these physiological reasons come together, abnormalities that imitate blockage may appear on ECG tracings merely because exertion was performed, even though there is actually no structural blockage in the vessels supplying the heart. This natural margin of error, referred to as a false-positive result, may unnecessarily cause great anxiety in the person and lead them to undergo invasive vascular examinations that are not actually needed. Taking this biological possibility into consideration, suspicious results are evaluated together with the woman’s age and symptoms, and when necessary, confirmation is performed using different ultrasound methods.

In Which Special Situations Is It Inadvisable to Perform an Exercise Stress Test (Treadmill)?

Although it is an easily accessible diagnostic method in clinical practice, the test places a very serious temporary burden on the body. Therefore, deliberately straining the circulatory system on critical days when the person’s health is unstable may cause undesirable complications. In such urgent situations where physiological risks outweigh the limited information the test would provide, making the patient exercise is completely avoided.

Some conditions in which placing the patient on the treadmill is prohibited are as follows:

• Acute heart attack
• Blood pressure that does not decrease with medication
• Very rapid heart palpitations
• Advanced heart failure
• Severe valve diseases
• Inflammation of the pericardium
• Blood clot in the lungs
• Suspicion of a tear in the major vessels

Because exertion in such severe and unstable conditions may cause the heart to completely lose its function, diagnostic processes are directed using different bedside devices while the patient remains completely at rest.

What Findings on the Exercise Stress Test (Treadmill) Screen Put Us on Alert?

The waves flowing across the computer screen in front of healthcare personnel are not merely random rises and falls. Blood pressure data coming from the arm cuff and unusual deviations in the graphs may reflect the distress within the heart and issue very urgent warnings. If the graphs suddenly begin to deteriorate even at the very beginning of the test while the device is moving at a slow pace, it is concluded that the affected area may be very extensive.

The findings that require urgent intervention at the screen are as follows:

• Sudden drop in blood pressure
• Severe chest pain
• Irregular rhythm attacks
• Deep ECG depressions
• Severe dizziness

As soon as such serious deviations are detected, the treadmill is stopped immediately. Considering that there may be a critical narrowing in the very important vascular pathways supplying the front and main surface of the heart, the patient is promptly moved into the recovery phase.

What Awaits Patients If the Exercise Stress Test (Treadmill) Result Is Suspicious?

If the patient experiences severe chest pain during physical strain that is intense enough to prevent further progress, or if the lines on the screen confirm signs of oxygen deficiency in the heart muscle, the test report is generally recorded as positive. The evidence obtained clearly demonstrates that the heart cannot increase blood flow. However, based on black-and-white waves, it is not possible with any technology at that moment to know which small vessel is narrowed and at exactly which millimetric point. The exercise process functions only like a sensitive fire detector that signals the general presence of a blockage. When reports are suspicious, positive, or inconclusive, the patient is referred to interventional angiography departments in order to directly visualize and confirm the problem and resolve it at the same time.

What Are the Angiography and Intravascular Measurements Required After an Exercise Stress Test (Treadmill)?

An invasive angiography procedure is planned in order to completely eliminate the doubts arising from the test result and create a detailed map of the vessels surrounding the heart like a network. This medical procedure is performed by entering the body’s bloodstream mainly through the small artery in the wrist. Very thin tubes are carefully advanced to the openings of the heart vessels, and special medical contrast dyes are injected into the lumen. In the moving X-ray recordings taken at that moment, narrowed areas are identified like blockages in a riverbed. Entering through the wrist significantly reduces the possibility of bleeding and allows the patient to get up quickly and return home on the same day. In gray areas where the degree of narrowing cannot be clearly understood visually, hair-thin digital pressure wires are advanced deep inside the vessel. These wires calculate the pressure passing through the narrowing with millimetric precision, just as if an exercise stress test were being performed, and mathematically confirm the severity of that area.

How Are Narrowings Detected by an Exercise Stress Test (Treadmill) Opened with a Stent?

Narrowings found to cause oxygen deprivation on the device and then proven to exist in the angiography environment are treated within minutes without the need for open surgery. The affected narrow channel is reached through special long wires, and a balloon is inflated exactly in the center of the blocked area. The inflated balloon crushes the stubborn plaques blocking the vascular pathway, widens the area, and opens the passage. However, elastic vessels may show a persistent reflex to return to their original condition after the procedure is completed. To physically prevent this closure and keep the wall permanently open like a tunnel, highly durable metal alloy scaffolds are placed in the area. The outer surfaces of new-generation technological stents are specially coated with specific medications. These coated medications greatly stop the uncontrolled cell proliferation that causes the vessel to narrow again, thereby securing healthy circulation.

How Are Follow-Up Exercise Stress Tests (Treadmill) and a New Lifestyle Planned After Treatment?

Placing a stent in the pathways on the surface of the heart solves the mechanical part of the problem within minutes and relieves the patient of the current narrowing. However, atherosclerosis is a chronic metabolic disease that does not end with that stent and continues to exist throughout the entire body. Returning completely to the previous inactive lifestyle, fatty diet, and cigarette smoke after the intervention will predispose the other healthy vessels to become blocked as well. Taking blood thinners without missing any doses and keeping cholesterol levels very low are essential rules. In the following periods, patients continue to undergo repeat exercise testing at certain intervals in order to monitor the recovery process. These follow-up exercise stress tests remain an integral part of the long-term plan to check how much the patient’s exercise capacity has improved and whether the stents are functioning perfectly.

Frequently Asked Questions

Prof. Dr. Kadriye Kılıçkesmez

Prof. Dr. Kadriye Orta Kılıçkesmez is one of the leading figures in the field of Turkish cardiology. She was born on January 24, 1974, in Tekirdağ. After completing her undergraduate education at Istanbul University Cerrahpaşa Faculty of Medicine, she chose cardiology as her specialty and received her specialist training at the Cardiology Institute of the same university. In 2015, she was appointed by the university to establish the Şişli Etfal cardiology clinic and Angio laboratory. Becoming a professor in 2017, Kadriye Kılıçkesmez established the cardiology clinic and Angio laboratory of Prof. Dr. Cemil Taşçı Hospital in 2020 and ensured that the clinic became a training clinic.