In many sports, the most important criteria of success rely on the ability to produce short-term maximal efforts, either in a single bout or repeatedly. Therefore, accurate, valid, and reliable testing of anaerobic performance is essential to structure and monitor training programs for these athletes. Although no single method has been yet established as a gold standard for the assessment of anaerobic characteristics, it seems that the standard Wingate all-out test (WAT) is currently the most widely used.
The validity of the standard WAT relies on the assumption that metabolic energy during the test is produced predominantly by the anaerobic metabolism (4). Although previous studies agreed that total energy turnover during this test is mainly derived from the phospholytic (alactic anaerobic) and glycolytic (lactic anaerobic) energy pathways, the magnitude of oxidative (aerobic) contribution measured in the same studies ranged from 9 to 44% (6,20,27,35–37). The large range of values reported by these various investigations is probably because of differences or limitations in the methods used to calculate energy expenditure derived from each energy pathway. This highlights the need for clarification on the extent of oxidative contribution during Wingate test, using a robust calculation method.
Although some validity studies showed a good correlation between mechanical parameters measured during the WAT and strength, speed, power, or agility (13,24,28), other investigations reported an absence of relationship between these variables and/or the incapacity of the WAT to discriminate between elite and nonelite athletes (2,10,17,26,32). Consequently, these authors criticized the ecological validity of the WAT, referring in particular to the discrepancies in the movement patterns and/or muscular mass involved in the test compared with real competition. To address these critiques, various modifications have been developed including the standing arm-crank and rowing Wingate test (15,25). However, these ergometers were designed either to target only 1 part of the body or focused on 1 specific sport discipline. Therefore, in sports involving the entire body, such as martial arts, racket sports, or team sports, there is a need to develop new tests based on ergometers involving the whole-body in the production of performance.
Recent studies reported that a modified elliptical trainer may be a good alternative to traditional cycle ergometers when performing the Wingate protocol to evaluate mechanical power during whole-body activities (29,31). Ozkaya et al. (30,31) showed that the 30-second elliptical all-out test (EAT) was characterized by very good retest Pearson correlations, ranging from 0.80 to 0.98 , and intraclass correlation coefficients (ICCs), ranging from 0.80 to 0.94 (p ≤ 0.001; 95% confidence intervals = 0.62–0.90) based on the same statistical data. However, correlations between mechanical power indices (r = 0.09–0.21) and physiological parameters, such as lactate responses (r = 0.28) between EAT and WAT, were very low. Thus, despite the fact that similarities have been observed between muscular and metabolic parameters measured during exercises performed on elliptical trainers and walking or running-based whole-body activities (8,33), data on the validity of this new test modality are lacking, in particular regarding the anaerobic nature of energy production.
Therefore, the main purpose of the present study was to compare the contributions of the oxidative, phospholytic, and glycolytic pathways to total energy expenditure during two 30-second all-out tests performed on a modified elliptical trainer and a cycle ergometer. It was hypothesized that compared with WAT, EAT would result in a significantly lower contribution of the oxidative system (hypothesis 1) and significantly greater contributions of the phospholytic and glycolytic energy systems (hypothesis 2) to total energy production. A secondary aim was to investigate the relation between metabolic and mechanical indices measured in WAT and EAT. It was hypothesized that peak power (PP) and average power (AP) during both tests would not be well correlated to physiological parameters reflecting the involvements of the phospholytic and glycolytic processes (hypothesis 3).
Experimental Approach to the Problem
A randomized cross-sectional study design was used to investigate the anaerobic nature of an EAT compared with the standard cycling Wingate test. Both tests have been used in previous publications to assess anaerobic characteristics of athletes and their accuracy and reliability have been well established (4,30,31). The present study thus focuses on the validity of both tests. After familiarization sessions and pilot studies to allow adaptation to the various test ergometers and determine individual workloads, the two 30-second all-out tests were presented a week apart, in a random order. The main dependent variables considered were parameters classically used in previous studies as indicators of oxidative (exercise oxygen consumption), glycolytic (blood lactate concentration), and phospholytic (oxygen kinetics during recovery) energy pathways. However, because of the various criticisms regarding the calculation methods used in previous studies, the present investigation relied on the most modern method and the one currently considered as the most valid to calculate the contribution of each energy pathway to total energy expenditure (6). The hypotheses were then tested by analyzing the differences between variables measured in EAT and WAT.
The study protocol was approved by the University Ethics Committee. Written informed consent was obtained after explanation of the nature and risks involved in participation in the experimentation. Twelve male athletes specialists of football, ice-hockey, and rugby volunteered to take part in the study (age, 20.3 ± 1.8 years; body mass, 74.8 ± 12.4 kg; height, 176.0 ± 9.10 cm; body fat, 12.1 ± 1.0%). At the time of the study, they were competing at a regional level in their respective sports and were involved in 5 ± 1 training session per week, including physical conditioning. Their average experience in their particular discipline was 7.6 ± 2.3 years. Physical conditioning practices of all the participants were quite similar, and they all had experienced repeated sprint and lactate tolerance training, classically used to enhance buffer capacity. All the testing sessions were performed in spring (20–22 °C temperature, 50% relative humidity), after the end of the competitive season, to minimize the effects of training load or periodization. In addition, the time of day at which testing was undertaken was replicated for each participant. They were requested not to take part in any exhaustive exercise 24 hours before the testing sessions. None of the participants suffered from any injury or were under any specific medication.
Familiarization Sessions and Pilot Studies
Participants visited the laboratory a few weeks before the main testing sessions to perform 10- and 30-second all-out tests on both cycle ergometer (Monark 894, Varberg, Sweden) and elliptical trainer (Precor Experience series EFX 576i; Precor, Inc., Woodinville, WA, USA). Previously suggested workloads, from 7.5 to 10% of body weight for a cycle ergometer (4) and 13.5 to 18% of body weight for a modified elliptical trainer (30), were tested to determine the best individual test load for each athlete. This latter was defined as the load that provided the greatest PP and expected ∼45–50% relative decline in power production over the 30-second test period. During each participant's familiarization session, special care was taken to supervise adaptation to high-velocity performance on the 2 ergometers, based on overall movement technique and pedaling/stepping rates.
Wingate All-out Test
The WAT protocol was performed on a standard lower body cycle ergometer (Monark 894). Individual workloads were used for each athlete, as previously determined. The seat height was adjusted for each participant to allow the knee to be slightly bent when the pedal was at its lowest position. Toe clips were individually adjusted. A 5-minute warm-up was performed with a resistance corresponding to 20% of the test load and a pedal rate of 70–80 rpm. Three acceleration bursts were included during the third, fourth, and fifth minutes, lasting 2- to 3-second each. At the end of the warm-up period, participants rested for a period of 5 minutes. The all-out test started with a 2- to 3-second unloaded period to overcome the inertia of the cycle ergometer and provide the opportunity to reach a maximal pedal rate. Just after the unloaded period, the test load was administered, setting the start of the 30-second all-out test. Participants received verbal encouragements throughout the test to help produce a maximal effort and were not allowed to stand up during the test. Mechanical power indices were continuously recorded and processed by the software and interface of the original Monark 894 cycle ergometer (4). After termination of the test, volunteers were supervised during a 60-minute resting period in a sitting position for recovery analyses.
Elliptical All-out Test
The Wingate test protocol was performed on a modified elliptical trainer (Precor Experience series EFX 576i, Precor, Inc.). As for WAT, individual workloads were used for each athlete, as previously determined. A 5-minute warm-up was undertaken with a cadence of 100 stairs per minute (50 rpm) (9). Modified 30-second elliptical trainer tests were standardized with the same procedures described above for the standard 30-second Wingate test protocol administrations (30). All mechanical power data were continuously collected using a Monark 894 rpm counter placed at the center point of the pulley and transferred to the computer. Sent data were automatically processed by the original Monark 894 cycle ergometer software (30). After termination of the test, volunteers were supervised during a 60-minute resting period in a sitting position for recovery analyses.
Five performance indices were calculated using the mean power produced during each 5-second interval: (a) PP, defined as the greatest mechanical power produced during any 5-second interval; (b) AP (mean), defined as the mean power production sustained throughout the 30-second test period; (c) minimum power, defined as the lowest power produced during any 5-second interval; (d) power drop (PD), defined as the degree of power drop-off during the 30-second test
; and (e) fatigue index (FI%), defined as the relative decline in power production over 30 second
Oxygen uptake (V[Combining Dot Above]O2) and carbon dioxide production (V[Combining Dot Above]CO2) were measured and recorded breath-by-breath using a laboratory gas analyzer (Quark b2; Cosmed, Rome, Italy) at rest, throughout the 30-second all-out tests and during the 60-minute recovery period. In addition to the device calibration before each test, instrument verification was undertaken immediately after testing according to the instructions of the manufacturer. Heart rate was recorded via the same gas analyzer system. Capillary blood samples were drawn from the fingertip at rest and at the first, third, fifth, seventh, and 10th minutes postexercise for both tests. Blood lactate (La) concentration was analyzed using the enzymatic amperometric method (Lactate Pro; KDK, Corp., Minami-Ku, Kyoto, Japan).
Estimations of the Relative Contributions of the Energy Systems
The net energy contribution (equation 1) of the oxidative energy pathway (W AER) was calculated using the trapezoidal method from the V[Combining Dot Above]O2 area integrated over time during the 30-second test (t 0–t 30) above rest (V[Combining Dot Above]O2r). V[Combining Dot Above]O2 was measured during a 5-minute period before warm-up while participants were in a seated position (Figure 1). The caloric equivalent of O2 was considered to be 21.1 J·L−1 (6).
The net energy contribution of the phospholytic energy pathway (W PC) was calculated from the fast component of the postexercise oxygen kinetics. The time course of the decay in V[Combining Dot Above]O2 was interpolated by using exponential analysis (equation 2), where “a” is the amplitude of the fast recovery V[Combining Dot Above]O2 consumption, “τa” is the time constant of the fast component of V[Combining Dot Above]O2, “b” is the amplitude of the slow component of V[Combining Dot Above]O2 consumption, “τb” is the time constant of the slow component of V[Combining Dot Above]O2, “c” is the asymptotic posttest V[Combining Dot Above]O2 at time → ∞, “t” is the time in seconds, and V[Combining Dot Above]O2(t) is the time-dependent variation in V[Combining Dot Above]O2 (Figure 2). Monoexponential and biexponential models were applied showing that V[Combining Dot Above]O2 data were best fitted by the biexponential model. Therefore, the time course of the decay in V[Combining Dot Above]O2 was interpolated by using the biexponential analysis (equation 2). Integration of the exponential part was calculated from “a” and “τa,” then W PC was estimated by using the caloric equivalent of O2 (equation 3) (21,34).
The net energy contribution of the glycolytic energy pathway (W LA) was predicted from body mass, peak delta La ([INCREMENT]Lap), O2-lactate equivalent, and the caloric equivalent of O2 (11,23). Delta La ([INCREMENT]La) was calculated as the difference between rest and postexercise lactate concentrations. The mean energy equivalent of peak lactate was considered to be 3.0 ml O2·kg−1·mmol·L−1, i.e., 63.3 J·kg−1·mmol·L−1 (11).
Total absolute metabolic work (W TOT) was calculated as the sum of the energy outputs from the 3 energy systems. Relative contributions of the oxidative (%W AER), phospholytic (%W PC), and glycolytic (%W LA) energy systems were then estimated in relation of the W TOT (6).
Results were evaluated by Sigma-Plot 16.0 (Systat Software, Inc., San Jose, CA, USA) and SPSS 19.0 (SPSS, Inc., Chicago, IL, USA). Descriptive results were reported as mean values
and SDs. Multiple nonlinear regression analyses were used to test whether the monoexponential single-3-parameter or biexponential double-5-parameter models sufficiently described the behavior of V[Combining Dot Above]O2 over time. Parametric assumptions were accepted and thus Student t-tests for paired samples were undertaken to assess differences in the contribution of the 3 energy systems and in mechanical variables between EAT and WAT. Effect size was analyzed based on Cohen's d. Finally, the relationship between mechanical and metabolic parameters was assessed by Pearson correlation analysis. Results with a p ≤ 0.05 were considered statistically significant for all the statistical analyses.
Mechanical power indices recorded during both tests are presented in Table 1. The results showed that PP, AP, MP, and PD were significantly greater in EAT than WAT (p ≤ 0.001). However, no significant difference between tests was observed in FI% (p > 0.05).
V[Combining Dot Above]O2 above rest during the EAT was 0.80 ± 0.12 L·min−1, whereas it was 0.94 ± 0.23 L·min−1 for WAT. Statistical analyses showed that significantly less absolute energy was derived from the oxidative energy pathway in EAT compared with WAT (p ≤ 0.05; Table 2). When expressed as a percentage of the total energy output, the relative oxidative contribution was also significantly lower in EAT as compared with WAT (p ≤ 0.001; Table 2). Mean “a” and “τa” were 2.87 ± 0.51 L and 1.09 ± 0.17 minutes for EAT vs. 2.62 ± 0.64 L and 0.91 ± 0.16 minutes for WAT. There was a significantly greater amount of energy derived from the phospholytic energy system, either expressed in absolute values, and relative to total metabolic energy (p ≤ 0.05; Table 2). There was a significantly greater [INCREMENT]Lap in EAT than WAT (14.4 ± 2.32 mmol·L−1 vs. 12.1 ± 1.62 mmol·L−1, p ≤ 0.001). Consequently, the absolute glycolytic energy output was significantly higher in EAT than WAT (p ≤ 0.01). However, when expressed as a percentage of the total energy output, the relative contribution of the glycolytic system was not significantly different between EAT and WAT (p > 0.05; Table 2). Finally, the total metabolic work was significantly higher in EAT than WAT (p ≤ 0.001; Table 2). During EAT, 89 and 11% of the metabolic energy were derived from anaerobic and aerobic energy sources, respectively, compared with 84 and 16% in WAT (p ≤ 0.001).
Pearson r correlation coefficients between the parameters measured from EAT and WAT are presented in Tables 1 and 2. The analyses showed that there were different correlation levels ranging from little (r = 0.17, p > 0.05) to high (r = 0.90, p ≤ 0.001) for both metabolic and mechanical parameters obtained from EAT and WAT.
On the other hand, the correlation analysis between mechanical and metabolic parameters measured in EAT showed little- and moderate-level relationships between PP and W PC (r = 0.20, p ≤ 0.05) and %W PC, (r = 0.53, p ≤ 0.05), respectively. In contrast, there were high- and moderate-level correlations between PP and W LA (r = 0.90, p ≤ 0.001) and %W LA (r = 0.63, p ≤ 0.05). The correlation between AP and estimation of the glycolytic energy contributions were high (r = 0.86, p ≤ 0.001) for W LA and moderate (r = 0.66, p ≤ 0.05) for %W LA. There were moderate-level correlations (r = 0.60, p ≤ 0.05) between all drop-off indices of EAT and W LA. A similar trend was observed for WAT, with little-level correlation between PP and W PC (r = 0.16, p > 0.05) and %W PC (r = 0.34, p > 0.05). There were high- and low-level correlations between PP and W LA (r = 0.85, p ≤ 0.01) and %W LA (r = 0.41, p > 0.05). In addition, AP was highly correlated with W LA (r = 0.85, p ≤ 0.01), but not with %W LA (r = 0.20, p > 0.05). Finally, there were moderate-level correlations between drop-off indices of WAT and W LA (p ≤ 0.05).
The present study is the first to assess the relative energy contributions of the 3 energy systems during an EAT performed on a modified elliptical trainer compared with the standard WAT performed on a traditional cycle ergometer. The main results showed that there was significantly less aerobic contribution in EAT compared with WAT, and thus hypothesis 1 was accepted. In addition, a significantly greater relative contribution of the phospholytic system was shown in EAT vs. WAT, whereas no significant difference between tests was observed for the relative contribution of the glycolytic system. Hence, hypothesis 2 was only partly accepted. This suggests that an elliptical trainer represents a more conceivable assessment of general anaerobic status during a 30-second all-out Wingate protocol and could be used as an alternative to the classical cycle ergometers in sports where performance relies on both upper body and lower body. These results will be interpreted in the following paragraphs with regards to methodological considerations and several potential explanation mechanisms, including mainly the muscle mass and fiber types involved in both tests.
The main issue raised in the literature regarding the use of a cycle ergometer when performing the Wingate protocol in the assessment of anaerobic performance is the extent of aerobic energy sources involvement in the production of total metabolic energy. The range reported in the literature is extremely wide, with values as low as 9% (20) and as high as 40 (27) or 44% (37). These apparent discrepancies between studies are mostly because of the various methods used to estimate relative energy contributions during anaerobic tests. Two main methods have been used in the above-mentioned studies to estimate the relative energy contributions during the WAT. The first method is based on the accumulated oxygen deficit and predicts anaerobic contribution by calculating the difference between the estimated oxygen cost of all work completed and the measured oxygen consumption during the test (27). The validity of this method during a supramaximal exercise relies on the assumption that energy demand can be estimated from the relationship between mechanical power and submaximal oxygen consumption (16). Studies based on this method assumed a constant mechanical efficiency; however, it has been shown that efficiency tends to decrease at high power outputs (22). This could result in an underestimation of anaerobic work or conversely an overestimation of aerobic contribution to total energy expenditure. The underestimation of anaerobic energy used by the accumulated oxygen deficit method has been confirmed by direct measurements from biopsied muscles (3). The second method involves directly measuring oxygen consumption to estimate aerobic contribution and then calculating anaerobic contribution based on the difference between completed total metabolic work and estimated aerobic work (20,35,36). This approach relies on other assumptions, in particular, the fact that until PP is reached, all the energy is provided by the phospholytic energy system and that there is no contribution of high energy phosphates to external work after 10-second of exercise. However, it has been shown that the 3 energy systems are not activated in a purely sequential manner, but instead start simultaneously and contribute to total energy in an overlapping way (16). In view of these inaccuracies, a recent study proposed another method to estimate the relative contribution of the oxidative, phospholytic, and glycolytic energy systems during the standard WAT, based on the integrated V[Combining Dot Above]O2 area over time during the test, the fast component of the kinetics of postexercise V[Combining Dot Above]O2, and net lactate accumulation (6). Relying on a similar method, results of the present study were very close to those from Beneke et al., for oxidative, phospholytic, and glycolytic energy contribution rates during a traditional WAT (16, 39, and 45% vs. 19, 31, and 50%, respectively), as well as the total metabolic work (127.8 vs. 128.1 J, respectively).
Our results demonstrated that all mechanical power indices, except FI%, were statistically greater in the EAT than the WAT. These results are not surprising because it is known that the total work capacity produced during exercise is closely related to the active muscle mass involved during this exercise. It is well established that the muscle mass involved during a standard all-out leg cycling test represents up to75% of whole-body muscle mass (6). Despite the limited literature on electromyographic analyses during exercises on elliptical trainers, 1 study has shown that there is a greater muscle recruitment during an exercise bout on an elliptical trainer compared with a lower body cycle ergometer (7). In many sports, such as team sports and martial arts, performance relies on the involvement of both lower body and upper body (1,5,12,14). Within this context, assessing the power of these athletes on an elliptical trainer seems more relevant than on a cycle ergometer that restricts the participation of the upper body.
As a result of these discrepancies in muscle mass involvement between both tests, participants' ability to naturally overcome the workload was different while exercising on EAT vs. WAT. Workloads that elicited the greatest PP and ∼45–50% fatigue index were accepted optimal for both Wingate test modalities. These optimal loads yielded similar results in FI% responses during EAT and WAT (p > 0.05), showing that the load optimizations were accurate. Therefore, it could be assumed that the greater anaerobic involvement observed in the present study during the test on the elliptical trainer resulted from differences in test modalities rather than differences in workloads between ergometers.
Because the validity of a test assessing short-term maximal power output relies on the assumption that metabolic energy during this test is produced predominantly by the anaerobic metabolism, our results are in favor of a good validity of the EAT. An element of explanation relies on the types of fiber in the specific muscles involved during those 2 exercise modalities. It is well known that the major muscle groups of the body (shoulder, chest, back, hip, leg, etc.) have a high proportion of fast-twitch (type-II) fibers (19). Thus, a greater involvement of these type II fibers was expected during the EAT compared with the cycling test, based on high-speed movement of the major muscle groups of upper body (18). This could partly explain the greater anaerobic involvement observed in the present study between the EAT and the classical WAT.
A secondary aim of this study was to investigate the relation between metabolic and mechanical indices measured in WAT and EAT. It was hypothesized that PP and AP would not be well correlated to the contributions of the phospholytic and glycolytic processes (hypothesis 3). This hypothesis was accepted. Indeed, an interesting finding of the present study was the weak correlations observed between mechanical and metabolic variables measured. This has been a matter of debate in the literature since several decades. When the WAT was created in the 1970s, PP was originally assumed to reflect the phospholytic processes, whereas AP was supposed to represent the extent of anaerobic glycolysis in the muscle. However, after subsequent studies, it was demonstrated that PP is unlikely to reflect only the phospholytic energy (4). This latter assumption was confirmed in the present study. Indeed, only little- and moderate-level correlations ranging from 0.16 to 0.53 were observed between PP and phospholytic processes in both all-out tests. In contrast, greater levels of association were observed between PP and the glycolytic energy system, ranging from 0.41 to 0.90. Because of above-mentioned findings, we also suggest that when referring to results of such tests, the terms of “PP output” and/or “AP output” are preferable to use than the commonly used terms of “anaerobic power” and/or “anaerobic capacity.” It may also be worth considering that instead of “anaerobic test,” the terms of “all-out test” may be preferable because all energy systems are activated simultaneously and contribute to total energy in an overlapping way (16). Indeed, the present study showed that there is at least 11% oxidative energy contribution in total energy turnover during an EAT.
Results of the present study indicate that there is less aerobic (11 vs. 16%) and more anaerobic (89 vs. 84%) energy contribution during a 30-second Wingate test when it is performed on an elliptical trainer instead of a cycle ergometer. Therefore, it is more useful to athletes and coaches because power indices obtained from elliptical testing represent whole-body locomotor tasks. All-out tests performed on elliptical trainers should thus be introduced into performance testing at different periods of the season in sports such as martial arts, team sports, or racket sports. The various indices measured could be used to assess the efficiency of various training interventions (i.e., PP as an assessment of power or speed training, AP or FI% to evaluate lactate tolerance), and determine athletes' profiles, with some sports mainly dependent on PP (team sports played on smaller pitches), and others on AP (martial arts or team sports played on larger pitches). These tests on elliptical trainers should also be incorporated into identification programs in all sports involving whole-body movements, and norms should be obtained regarding specific sports.
The authors would like to give special thanks to Alvin SUM, from London Metropolitan University, Sports Center Performance Laboratory, and Assistant Professor Serdar Arıtan, PhD, from Hacettepe University, School of Sport Science and Technology for their technical supports. This study was financially supported by International Post-doctoral Research Fellowship Program of the Scientific and Technological Research Council of Turkey. The authors do not have any conflict of interest. The results of this study do not constitute endorsement of the product by the authors or the National Strength and Conditioning Association. This paper was awarded the best oral presentation in the field of sports and health sciences at the 12 International Sports Science Congress.
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