Abstract
er represents an important parameter of aerobic function and is the highest average effort that can be sustained for a period of time without fatigue. Critical power is determined mainly in the laboratory. Many different approaches have been applied in testing methods, and it is a dif cult task to determine which testing protocol it the most suitable. This review aims to evaluate all possible tests on bicycle ergometers or bicycles used to estimate critical power and to compare them. A literature search was conducted in four databases (PubMed, Scopus, SPORTDiscus, and Web of Science) published from 2012 to 2022 and followed the PRISMA guidelines to process the review. Twenty-one articles met the eligibility criteria: records with trained or experienced endurance athletes (adults > 18), bicycle ergometer, a description of the testing protocol, and comparison of the tests. We found that the most widely used tests were the 3-min all-out tests set in a linear mode and the traditional protocol time to exhaustion. Some other alternatives could have been used but were not as regular. To summarize, the testing methods offered two main approaches in the laboratory (time to exhaustion test andthe
protocol, and comparison of the tests. We found that the most widely used tests were the 3-min all-out tests set in a linear mode and the traditional protocol time to exhaustion. Some other alternatives could have been used but were not as regular. To summarize, the testing methods offered two main approaches in the laboratory (time to exhaustion test andthe 3-min all-out test with different protocols) and approach in the eld, which is not yet completely standardized. Keywords:critical work; methods; performance analysis; endurance athletes 1. Introduction Critical power (CP) represents the boundary between the intensity domains of heavy and severe exercise [1]. It is the greatest average effort that can be sustained for a period of time without fatigue. Endurance athletes are exposed to a fast pace, but even a slight increase in pace may lead to a reduction in the tolerable duration of exercise. This is what CP can predict [2]. From the mathematical viewpoint, CP is de ned as the power-asymptote of the hyperbolic relationship between power output (PO) and time-to-exhaustion [3]. The power-asymptote stands for CP and the hyperbole stands for the amount of work done above CP (W'); together they predict the tolerable duration of exercise above the CP [4]. Figure the CP asymptote but under the curve represents the amount of work (in joules) over CP that can be performed until exhaustion occurs. Each grey shaded box shows how much work can be performed at speci c PO with the CP, in this case 300 W. The important thing is that every athlete has a unique critical power curve, which has to be constructed from their own individual exercise tests. W' is constant, but may be utilized at different rates depending on the proximity of the exercise PO to the CP [5]. W' is measured in kilojoules (kJ) and is a function of the oxygen uptake (VO2) slow component; meaning a slow increase in the VO2during constant work performed above the lactate threshold [6]; maximal oxygen uptake (VO2max); the depletion of intramuscular substrates, such as muscle creatine phosphate; and the glycogen, and the accumulation of
the exercise PO to the CP [5]. W' is measured in kilojoules (kJ) and is a function of the oxygen uptake (VO2) slow component; meaning a slow increase in the VO2during constant work performed above the lactate threshold [6]; maximal oxygen uptake (VO2max); the depletion of intramuscular substrates, such as muscle creatine phosphate; and the glycogen, and the accumulation of metabolites (hydrogen ions, adenosine diphosphate, phosphate ions), which is associated with impaired muscle contractile function [7]. The CP represents Int. J. Environ. Res. Public Health2022,19, 7589.
Int. J. Environ. Res. Public Health2022,19, 7589 2 of 17 an important parameter of an aerobic function. It can provide an even more meaningful criterion based on the measure of external PO and time than the lactate threshold or the maximal uptake of oxygen (O2) [3,8]. Rather than using equivalent exercise intensities relative to these metabolic parameters (lactate threshold, VO2max), setting exercise intensity relative to CP combines systemic and intramuscular response, and the W' is expended above the CP, VO2maxis attained, and intolerance is manifested. The CP occurs approximately at 7080% VO2maxand trained individuals can reach 8090% VO2max[4].Int. J. Environ. Res. Public Health 2022, 18, x FOR PEER REVIEW 2 of 18 Figure 1. The power–time (P-t) relationship for high-intensity exercise W’ is constant, but may be utilized at different rates depending on the proximity of the exercise PO to the CP [5]. W´ is measured in kilojoules (kJ) and is a function of the oxygen uptake (VO 2) slow component; meaning a slow increase in the VO2 during con- stant work performed above the lactate threshold [6]; maximal oxygen uptake (VO 2max); the depletion of intramuscular substrates, such as muscle creatine phosphate; and the gly- cogen, and the accumulation of metabolites (hydrogen ions, adenosine diphosphate, phosphate ions), which is associated with impaired muscle contractile function [7]. The CP represents an important parameter of an aerobic function. It can provide an even more meaningful criterion based on the measure of external PO and time than the lactate thresh- old or the maximal uptake of oxygen (O 2) [3,8]. Rather than using equivalent exercise in- tensities relative to these metabolic parameters (lactate threshold, VO 2max), setting exercise intensity relative to CP combines systemic and intramuscular response, and the W´ is ex- pended above the CP, VO 2max is attained, and intolerance is manifested. The CP occurs approximately at 70–80% VO 2max and trained individuals can reach 80–90% VO2max [4]. This has a significant potential for sports performance but is often taken as a purely mathematical construct that does not have a physiological importance [3]. The CP is pri- marily the rate
pended above the CP, VO 2max is attained, and intolerance is manifested. The CP occurs approximately at 70–80% VO 2max and trained individuals can reach 80–90% VO2max [4]. This has a significant potential for sports performance but is often taken as a purely mathematical construct that does not have a physiological importance [3]. The CP is pri- marily the rate of oxidative metabolism rather than the mechanical PO (by which it is typically measured). This can properly be termed “critical VO 2”. In cycling, the PO corre- sponds to this critical VO 2 that can be altered with the chosen pedal rate. The actual CS (critical speed equivalent to CP) is also equivalent to the critical VO 2 but depends on the movement economy. This is because critical VO 2 is expressed functionally in units of power or speed that are effective in the prediction of exercise tolerance or performance [4]. Understanding CP can help with racing strategies. This concept is best explained through considering the performance of two runners with an identical gas exchange threshold (GET), which is used as an index of anaerobic threshold [9] and VO 2max values. Using the metric of running economy (i.e., the percentage of GET relative to VO 2max), the runners may be considered identical. However, one runner has a higher CS and lower D´ (distance equivalent to W´) compared to the other. The runner with higher CS should adopt a front-running strategy rather than holding back. This strategy involves running Figure 1.The powertime (P-t) relationship for high-intensity exercise. This has a signi cant potential for sports performance but is often taken as a purely mathematical construct that does not have a physiological importance [3]. The CP is primarily the rate of oxidative metabolism rather than the mechanical PO (by which it is typically measured). This can properly be termed critical VO2. In cycling, the PO corresponds to this critical VO2that can be altered with the chosen pedal rate. The actual CS (critical speed equivalent to CP) is also equivalent to the critical VO2but depends on the movement economy. This is because critical
metabolism rather than the mechanical PO (by which it is typically measured). This can properly be termed critical VO2. In cycling, the PO corresponds to this critical VO2that can be altered with the chosen pedal rate. The actual CS (critical speed equivalent to CP) is also equivalent to the critical VO2but depends on the movement economy. This is because critical VO2is expressed functionally in units of power or speed that are effective in the prediction of exercise tolerance or performance [4]. Understanding CP can help with racing strategies. This concept is best explained through considering the performance of two runners with an identical gas exchange threshold (GET), which is used as an index of anaerobic threshold [9] and VO2maxvalues. Using the metric of running economy (i.e., the percentage of GET relative to VO2max), the runners may be considered identical. However, one runner has a higher CS and lower D' (distance equivalent to W') compared to the other. The runner with higher CS should adopt a front-running strategy rather than holding back. This strategy involves running faster in split-times rather than trying to store energy for a big nish. This means that running or cycling below the CS/CP will result in a slower time over a middle distance. On the other hand, the runner with a higher D' should try to keep the pack of runners closer to his pace and then rely on a large portion of D' for a big nish [10]. Once you know your CP and W', you can predict the maximal power you could sustain over various periods of time, and this can be useful for creating pace strategies. The CP concept is mainly generalized to endurance sports, such as running, rowing, swimming, and cycling, and continuous and intermittent isometric exercise. This model has been modi ed for intermittent exercise and has a potential application in interval training and team sports, such as football, rugby, hockey, etc. It cannot be applied to sporting activities that involve a single or only a few muscle contractions (e.g., eld athletics, archery), sports where the work-to-rest ratios are such that
continuous and intermittent isometric exercise. This model has been modi ed for intermittent exercise and has a potential application in interval training and team sports, such as football, rugby, hockey, etc. It cannot be applied to sporting activities that involve a single or only a few muscle contractions (e.g., eld athletics, archery), sports where the work-to-rest ratios are such that the limits set by the
Int. J. Environ. Res. Public Health2022,19, 7589 3 of 17 W' parameter are unlikely to be challenged (e.g., American football, baseball, cricket) or events where the PO does not exceed the CP (e.g., golf, ultra-endurance events) [3]. The CP is typically determined in the laboratory, though it is also possible to use eld conditions in the form of cycling in the velodrome or on the road for a certain time [5]. Recent research found that testing maximal power indoors and outdoors cannot be used interchangeably. It is hard to translate results from indoor testing to outdoor among elite cyclists due to individual variation [11]. Conditions such as cadence, body position, level ground, or uphill conditions have been shown to have an impact on the estimation of the critical power. However, a good agreement exists between some laboratory tests and real cycling performance. Testing protocols should mirror as closely as possible the competition settings to provide environmental validity. As an example, climbing specialists should perform prediction trials on a road bike in uphill conditions, while time trials specialists should conduct testing on a time trial bike on level ground [12]. The advantage of CP testing is that it gives you two physiological markers from one test (CP and W'). Knowing both the CP and W' can be useful in determining how to balance these different parts of the physiology, similarly to how the lactate threshold is a balance between the aerobic and anaerobic systems [5]. Due to the different approaches to testing methods, it is a dif cult task to determine which testing protocol is the most suitable. There is a large diversity of methods and many criteria can be chosen to establish the testing protocol. This review searched the more recent scienti c literature from the years 20122022 to provide a comprehensive overview of testing protocols. The aim of this paper is to evaluate all possible tests on bicycle ergometers and their alternatives in order to determine CP among endurance athletes and compare them. This could simplify decisions relating to test selection and provide a compact overview of all possible
recent scienti c literature from the years 20122022 to provide a comprehensive overview of testing protocols. The aim of this paper is to evaluate all possible tests on bicycle ergometers and their alternatives in order to determine CP among endurance athletes and compare them. This could simplify decisions relating to test selection and provide a compact overview of all possible criteria that affect testing. 2. Materials and Methods Search Strategy A literature search was conducted in four databases: PubMed, Scopus, SPORTDiscus, and Web of Science. The keywords put into the search were: (critical power) AND (test OR tests OR method OR methods) AND (bicycle ergometer OR cycle OR cycling). This review followed the PRISMA ow diagram (Figure). Several records (n= 4) were added from the literature search found in the relevant articles. Exclusion criteria were de ned for the search strategy to exclude unwanted studies: duplicates; language (if not English); wrong study design: review articles, meeting abstracts, letters, corrections, and edito- rial materials; participants (if not human); no words (if they did not include keywords); wrong words (critical speed, critical velocity, critical forces, critical torque); year (if not 20122022). The remaining records were assessed for eligibility and were not included if they did not comply with the inclusion criteria. The criteria that had to be met were: trained or experienced endurance athletes, adults (>18), detailed description of the test (bicycle ergometer, number of visits laboratory/ eld, resistance, cadence, calculation of CP and W'), comparison of the tests, and number of participants (n> 6). Studies had to ful l these criteria to be included in this review. A total of 1114 studies were identi ed from the databases (Figure). Before screening, 622 records of duplicates were eliminated A total of 170 full-text records were screened, though only 21 studies were included in the review. The 149 pieces of research that did not match the eligibility criteria based on full-text screening were excluded because of the aforementioned inclusion criteria.
full-text records were screened, though only 21 studies were included in the review. The 149 pieces of research that did not match the eligibility criteria based on full-text screening were excluded because of the aforementioned inclusion criteria.
Int. J. Environ. Res. Public Health2022,19, 7589 4 of 17Int. J. Environ. Res. Public Health 2022, 18, x FOR PEER REVIEW 4 of 18 · year (if not 2012–2022). The remaining records were assessed for eligibility and were not included if they did not comply with the inclusion criteria. The criteria that had to be met were: trained or experienced endurance athletes, adults (>18), detailed description of the test (bicycle er- gometer, number of visits laboratory/field, resistance, cadence, calculation of CP and W´), comparison of the tests, and number of participants (n > 6). Studies had to fulfil these criteria to be included in this review. A total of 1114 studies were identified from the databases (Figure 2). Before screen- ing, 622 records of duplicates were eliminated A total of 170 full-text records were screened, though only 21 studies were included in the review. The 149 pieces of research that did not match the eligibility criteria based on full-text screening were excluded be- cause of the aforementioned inclusion criteria. Figure 2. PRISMA flow diagram of the search strategy. Records identified through database searching: PubMed (n = 209) Scopus (n = 328) SPORTDiscus (n = 210) WoS (n = 367) Screening Included Eligibility Identification Additional records identified through other sources (n = 4) Records after duplicates removed (n = 496) Records screened (n = 452) Records excluded: No words (n = 154) Wrong words (n = 34) Year (n = 94) Full-text articles assessed for eligibility (n = 170) Full-text articles excluded: (n = 149) - not trained or experienced endurance athletes - not compared tests to determine CP - not included detailed description of the test - number of participants ≤6 - not included adults’ participants Studies included in quantitative synthesis (n = 21) Records excluded before screening: Duplicates (n = 622) Records excluded: Foreign language (n = 20) Wrong study design (n = 21) No humans (n = 3) Figure 2.PRISMA ow diagram of the search strategy. 3. Results Twenty-one studies remained for more detailed analysis. All of these are concerned with the same major subjectCP. The studies contain
synthesis (n = 21) Records excluded before screening: Duplicates (n = 622) Records excluded: Foreign language (n = 20) Wrong study design (n = 21) No humans (n = 3) Figure 2.PRISMA ow diagram of the search strategy. 3. Results Twenty-one studies remained for more detailed analysis. All of these are concerned with the same major subjectCP. The studies contain different methods, conditions (labo- ratory, eld), resistance/cadence, cycle ergometer, and choice of mathematical model. 3.1. Characteristics of the Participants The characteristics of the participants are summarized in Table. In total, 242 partici- pants were involved in the records (199 males, 43 females, mean SD: age = 29.1 5.9 years). Ten of the studies included men and women[1322],while the rest included onlymen [8,2332] . The inclusion criteria for participants were de ned as trained and experienced athletes. Four studies described moderate and recreationally trained subjects, which is somewhat in con ict with these criteria [13,14,17,25], but all participants were capable of completing the test and all studies contain important information. The other studies described subjects as elite/competitive, club-level, trained, or a combination [8,15,19,20,2224,26,2832]. Three incorporated various tness levels that included competitive and recreationally trained individuals [16,18,21]. All participants were focused on endurance sports, mainly cycling.
Description
A review of testing methods for determining critical power in endurance athletes.