What is a stress test and what is its purpose?

Qué es y para qué sirve una prueba de esfuerzo

The stress test is one of the most sought-after services offered by the High Performance Sports Centre (CIARD) at La Manga Club. It's used to evaluate a person's physical condition, whether he or she is a professional athlete or an amateur. What’s more, at the CIARD testing is adapted to the needs of any sporting discipline.

La Manga Club, 16 June 2015. A stress test provides us with an analysis of a participant’s physical condition, measuring cardiovascular and pulmonary performances. There are two types of stress test: the first is known as an ergometer test (a stress test as such) which functions at a diagnostic level, and the cardiopulmonary test which complements the former as it provides an analysis of gas exchange, allowing us to gain a better understanding of someone’s physical state.     

Although there are many different ways in which a stress test can be carried out, the progressive treadmill test, which can be seen in this image, or the cyclo-ergometer (exercise bike) are the most common. The athlete starts at a low speed and intensity which is increased every minute until he or she can no longer continue. This test should last no longer than 15 minutes.

     

Together with the gas exchange analysis, cardiac activity is also monitored by an electrocardiogram (ECG). This allows the team of medical staff to analyse how the heart rate is effected alongside the levels of oxygen and carbon dioxide consumed throughout the test.      

 

One of the principal aims of the stress test is to rule out any possible health problems which could limit physical activity and daily exercise. At the CIARD we have sports medicine and cardiology specialists who analyse the results of the stress test and the ECG.

¿How is the test carried out at the CIARD?

CIARD coordinator, Asunción Martínez, tells us how this test and each of its phases are carried out. “First the cardiologist runs a resting ECG, and then carries out the test on the treadmill or cyclo-ergometer, carefully matching the intensity and speed of the test to the athlete’s abilities”. Upon completing the test, the information relating to the state of health of the athlete's heart is gathered. When the test is carried out with the gas consumption analysis test, the following information is also obtained:

VO2 max (used to calculate a person’s aerobic capacity, it is the maximum amount of oxygen that the body can use)    

Maximum heart rate

First Ventilatory Threshold (VT1)

Second Ventilatory Threshold (VT2)

The stress test provides us with information on the heart rate and running speed within each of these zones (as defined before taking the test according to the VT1 & VT2). “This makes it much easier to establish the correct levels of intensity for training sessions”, explains Doctor Martinez.    

Are these values the same for all athletes?

As Asunción Martínez, coordinator of the CIARD, states, “the values of oxygen consumption are specific to each individual athlete, and mostly depend on the athlete's chosen sport and gender”. This means that men produce higher values of oxygen consumption than women since these values correspond to the amount of muscle in the body, which is usually higher in men. For example, oxygen values tend to be higher in tests carried out on the treadmill than those on the bike because more muscles are in use in the running test than in the bike test. “Therefore,” continues Doctor Martínez, “if the same person took both tests (on the treadmill and bike), the VO2 value would be greater on the treadmill than on the bike. This figure is, therefore, irrelevant when comparing a cyclist with a runner.”     

It has always been said that long distance athletes, such as rowers, cyclists and especially cross-country skiers, are those who produce the highest values of oxygen consumption. Miguel Indurain proved this theory wrong in 1994, when at 30 years old, he broke the one hour record and won his fourth Tour de France. In his stress test he produced a value of 79 ml/min/kg, significantly above what other athletes had achieved.     

CIARD specialists tell us that someone who wants to start partaking in physical activity without any previous experience, does not need to complete a full stress test (including a gas exchange analysis), although a medical check-up is highly recommended. Your lifestyle will change and your heart will be put under more strain than usual. A medical check-up of this kind should include a stress test with an ECG, to eliminate the risk of any potential problems which could arise when starting to undertake physical activity.

“For those who exercise regularly” explains Asunción Martínez, “with the aim of improving their performance, or preparing for a run of up to 10km, a triathlon, marathon, half marathon… the stress test is highly valuable, since it can rule out diseases, and provide the information needed to tailor make training sessions in a much more effective way”.