The extended stress test or Cardio-Pulmonary Exercise Testing (CPET) shows the patient his or her clinical-cardiac condition, allowing for accurate assessment of the individual's aerobic fitness, and providing personal parameters for adapting optimal training intensity. Aerobic fitness is of considerable importance in attaining athletic achievements involving moderate endurance lasting three to 20 minutes, and in prolonged aerobic endurance lasting more than 20 minutes. Measurement and assessment of an individual's current aerobic fitness is a basic condition for starting a professional, high quality process to improve such fitness, and to upgrade the physical training level at different stages of the training process.
Quantifying and evaluating aerobic fitness using objective measures enables goal setting, and constitutes a basis for comparison after re-evaluation. Achieving a goal in sport requires upgrading the training process by accurately determining the training variables (intensity, duration and frequency) based on personal physiological parameters such as maximal oxygen consumption (VO2 max) and anaerobic threshold (lactate threshold).
Towards the end of the 20th century, a significant change occurred in the characteristics of physical fitness activity in modern Western society. Accelerated technological changes have reduced the need for spontaneous physical activity for daily existence, security and mobility. The recognition of the importance of physical activity to human health and the clear connection between poor physical fitness and mortality resulting from chronic diseases such as cardiovascular disease, diabetes, and various cancers, have accelerated the integration of structured and planned exercise as part of modern lifestyle. In terms of good health, aerobic fitness is considered to be the most important component of physical fitness. Objective assessment of aerobic fitness highlights the level of any potential health risk, enabling doctors to prescribe a relevant course of activity to improve fitness.
In addition to improving aerobic fitness for health and sports purposes, activities such as walking, running, cycling, etc. make a significant contribution to a person's energy expenditure. Research evidence indicates that a controlled dietary regime combined with physical activity can create a negative caloric balance to help reduce weight we can sustain over time. To calculate someone's energy balance, we require accurate information about the person's metabolism and the amount of energy used up when performing structured and planned physical activity.
Extended stress test (CPET)
Based on the above, we can see that proper aerobic training planning to achieve both health and athletic improvement, and to reduce weight. requires:
- A reliable and valid indicator by which aerobic fitness can be estimated
- Precise information on optimal workout intensity for aerobic fitness development
- Accurate information on the energetic cost of a given effort.
An extended stress test (see image), also called CardioPulmonary Exercise Testing (CPET), provides all the necessary information for the planning and monitoring of aerobic training for both professional and amateur athletes, and whether someone engages in physical exercise to maintain a healthy lifestyle or as part of a weight loss program. CPET incorporates the clinical stress test (ergometric or ECG stress test) and measurement of respiratory components using a metabolic system. The clinical stress test, required by the Sports Act for certain ages, is designed to examine heart function and resting blood pressure response, both during stress and recovery. Using the maximum mechanical power achieved in the clinical stress test, in the form of the maximum speed and incline of the treadmill or the maximum output in watts whilst cycling, it is possible to roughly assess the aerobic capacity of the subject within a 10%-20% error range.
As will be explained below, the metabolic system measurements obtained from the CPET enable a very accurate assessment of aerobic fitness.
The CPET and accompanying consultations last about two hours and include:
- Filling out a medical questionnaire and medical evaluation by a sports physician
- Connection to an ECG system, conducting ECG and resting blood pressure check
- Connection to a metabolic system
- Performing an incremental effort until reaching the maximum (- symptom limited) level of stress. The duration of the effort is eight to 12 minutes, and can be performed on an ergometer or bicycle (see picture). ECG, as well as respiratory and metabolic parameters * monitored throughout the entire stress test period.
- ECG test and blood pressure during recovery
- Meeting with an experienced physiologist to analyze the findings of the examination*
- A concluding meeting with the sports doctor.
The findings
The results obtained from the CPET are as follows:
- The characteristics of the heart's electrical activity on the ECG diagram and the blood pressure response, which indicate the heart's ability to perform physical exercise.
- A physiological index called maximal oxygen consumption (VO2 max) (Fig. 1). We can use this index to quantify and evaluate a subject's aerobic fitness on the basis of norms adapted to men (Table 1) and to women (Table 2). The norms and corresponding assessment refer to the regular population and not to athletes. In the professional literature there are norms for the various sports, according to which we can evaluate the aerobic ability of the athlete and even predict his or her athletic achievements.
The subject, whose test appears in Figure 1, is 48 years old and his VO2, as shown in Figure 1, is 54.7 ml/kg/min. A comparison of the findings of the test to the norms in Table 1 shows that in relation to his age group, the examinee was above the 90th percentile and in a state of "excellent" aerobic fitness. Those subjects with a VO2 value below the 20th percentile are deemed to suffer from low aerobic fitness, which is a health risk factor for the development of various diseases such as cardiovascular disease, diabetes and various cancers.
- A physiological indicator called respiratory anaerobic threshold (Fig. 2). This value corresponds to the lactate threshold, and it enables you to ascertain optimal effort intensity to develop aerobic fitness in High Intensity Interval Training (HIIT). In the anaerobic threshold data table, appearing in the lower right corner of Figure 2, the intensity of the anaerobic threshold is shown in values of VO2 (ml/min), specific oxygen consumption (ml/kg/min), HR (bpm), speed and slope when the test is performed on a treadmill, and power in watts when the test involves cycling. The anaerobic threshold of the subject (24 years old), whose results are described in Figure 2 occurred at a HR of 171 bpm and at a speed of 10.5 mph (17 kph) and an incline of 4%. If the subject wishes to continue to improve his aerobic fitness, he must perform the quality interval training lasting 60-50 minutes at a HR between 170 and 175 bpm. His VO2 was 68 ml/kg/min, indicating that his aerobic fitness (maximum aerobic capacity) is excellent for his age. He reached the anaerobic threshold at an oxygen consumption value of 62.4 ml/kg/min, which is 92% of VO2. This is further evidence of the subject's outstanding aerobic fitness (aerobic endurance). It is no wonder that his personal record in a 10,000m run is 31:30 minutes.
- Average values of 30 seconds in each of the following elements (Table 3): total oxygen consumption (ml/min), specific oxygen consumption (ml/kg/min), HR (bpm), speed and slope when the test is performed on a treadmill and power in watts when the test involves cycling.
The table provides precise information on the following:
- The energetic cost of physical activity, i.e. how many calories a person burns up during physical activity conducted at a given heart rate.
- HR at each relative given oxygen consumption. This component is of considberable importance when planning high quality training in which aerobic intensity is determined in relation to VO2.
In Table 3, average 30-second values are shown in the subject's CPET, whose anaerobic threshold appears in Figure 2 (24 years of age, VO2 - 68 ml/kg/min, anaerobic threshold at HR 171 and oxygen consumption of 62.4 ml/kg/min). Based on the table data, it is possible to calculate the energetic cost of a HIIT session with an anaerobic threshold lasting 60 minutes. When the subject has a HR range of 171-174 bpm, his total oxygen consumption is about 4.4 l/min (bold). Every liter of oxygen consumed produces about 5 calories of energy. In other words, the person in question uses up about 22 calories/min, and the total energetic cost of a 60-minute workout is about 1,320 calories.
If the above subject seeks to perform an extended HIIT workout at an intensity level of 75% of the VO2, he can use the table to identify the corresponding HR. A result of 51 ml/kg/min makes up 75% of a VO2 value of 68 ml/kg/min. The table data (bold) shows that the training HR corresponding to oxygen consumption of 51 ml/kg/min is 154-160 bpm.
In conclusion, as shown in Table 4, the CPET shows the patient his or her clinical-cardiac condition, allowing for accurate assessment of the individual's aerobic fitness, and provides personal parameters for adapting optimal workout intensity to develop aerobic fitness and to calculate the energy expenditure involved in physical activity. CPET combines three tests simultaneously: clinical stress testing, anaerobic threshold (lactate threshold) and VO2, thus saving time and money, and providing a comprehensive physiological picture of the subject.
