In recent years, the recognition, public interest and participation in Paralympic sports, including wheelchair basketball, have increased remarkably. The volume of literature concerning field-based physiological testing of wheelchair basketball is considerably smaller (Goosey-Tolfrey and Leicht, 2013) compared to able-bodied basketball players (Boone and Bourgois, 2013; Gocentas and Landõr, 2006; Köklü et al., 2011; Pojskić et al., 2015; Žumbakytė-Šermukšnienė et al., 2012). In wheelchair basketball, high-intensity performance and a complex structure of movement are prevalent (Skucas and Pokvytyte, 2017; Yanci et al., 2015). Furthermore, an increase in the number of studies on performance in wheelchair sports has been observed over the past two decades (de Groot et al., 2016; Leicht et al., 2012, 2013; Molik et al., 2010; Paulson and Goosey-Tolfrey, 2017; Pereira et al., 2016; Vanlandewijck et al., 1999; Weissland et al., 2015). Wheelchair basketball is a team sport for individuals with such chronic conditions resulting in lower-limb disability as spinal cord injury, cerebral palsy, musculoskeletal conditions, spina bifida, amputation and poliomyelitis, and a reduced ability to play running basketball in the same manner as able-bodied players (IWBF, 2014; Paulson and Goosey-Tolfrey, 2017). Thus, wheelchair basketball players use sport-specific manual wheelchairs and are classified according to their physical capacity to perform basic basketball movements (de Groot et al., 2003; IWBF, 2014). Performance in wheelchair basketball is similar to a regular basketball game based upon endurance, strength, speed, coordination and mobility (Cavedon et al., 2015; Iturricastillo et al., 2015; Knechtle and Köpfli, 2001). Therefore, performance testing in wheelchair basketball is complex and difficult. The importance of high-level aerobic fitness for team sport players is well known (Harrison et al., 2015; Knechtle and Köpfli, 2001). In wheelchair basketball, aerobic power is considered crucial. Aerobic capacity (VO2peak) is a success-related factor in endurance sports (Pretorius et al., 2015). Lactate concentration (LApeak) during and after exercising determines the metabolic character of the process and the anaerobic threshold (AT) can be estimated. In practice, LApeak and AT are essential when preparing an appropriate training plan in terms of the type of exercises, repetitions and intensity (intervals between each exercise, a number of sets of exercises) (Ghosh, 2004). Therefore, cardiorespiratory variables as well as LApeak and AT were analyzed in this study.
There are a lot of evaluation protocols used to identify aerobic performance in able-bodied basketball players (Ben Abdelkrim et al., 2010; de Araujo et al., 2014). Although typically the principles of endurance training and aerobic testing are directly transferred from able-bodied sport to disabled sport, it has to be noted that sports performance of wheelchair athletes may be affected by some unique physiological differences (Bhambhani, 2003; de Lira, 2010). Moreover, due to the fact that considerably smaller muscle mass is utilized during upper body exercise (arm cranking) than during lower body exercise, it is often questionable whether the cardiovascular system of wheelchair athletes is fully stressed and maximal values of aerobic power are attained (Bhambhani, 2011). Even though static exercises of upper limbs do not exert a significant influence on the left ventricular function of the heart and on cardiorespiratory adaptation to incremental arm exercises in power lifting athletes (Żebrowska et al., 2013a), it was noted that athletes with left ventricular hypertrophy demonstrated enhanced responses to eccentric arm exercises (Żebrowska et al., 2013b). If lower-limb and upper-limb exercises of similar intensity are performed, the former require greater carbohydrate (muscle glycogen) expenditure and greater lactate production in the exercising limb (Ahlborg and Jensen-Urstad, 1991). Therefore, selecting an optimal exercise protocol is essential for athletes’ safety and comfort as well as for obtaining the most interpretable data (Cooper and Storer, 2001). It has been established that in sports testing, an exercise mode should simulate a given motor task as closely as possible (Bhambhani, 2011; Goosey-Tolfrey and Tolfrey, 2008). In wheelchair athletes, aerobic performance is commonly assessed with the use of an arm crank ergometer (ACE), a wheelchair ergometer (WCE) or a wheelchair treadmill (WCT) (Bhambhani, 2011; Cooper and Storer, 2001; Hartung et al., 1993). Although there are many evaluation protocols to identify peak oxygen uptake in wheelchair athletes (Goosey-Tolfrey et al., 2014; Hartung et al., 1993; Leicht et al., 2013; Rasehe et al., 1993; West et al., 2016; Wicks et al., 1983; Veeger et al., 1991), few protocols have been applied to evaluate these conditions specifically in wheelchair basketball players (de Lira et al., 2010; Goosey-Tolfrey, 2005; Knechtle and Köpfli, 2001; Rotstein et al., 1994). The majority of maximal exercise testing protocols in wheelchair basketball use WCT as the mode of exercise with various combinations of constant and/or increased grade and speed. There is no agreement as to which test protocol yields the most consistent values of peak oxygen uptake in wheelchair basketball players. Hartung et al. (1993) noted that a treadmill protocol involving increments of both speed and grade produced maximal outcomes. Very few studies have been found regarding the use of ACE to determine aerobic performance in wheelchair basketball players. Rotstein et al. (1994) used ACE (Fleish cycle ergometer) to evaluate elite Israeli wheelchair basketball players. The starting load was 30 W, which was increased by 30 W every 2 minutes. Vanlandewijck et al. (1999) examined 15 wheelchair basketball players and the load in their protocol (power output; PO) increased by 15 W every 3 minutes (with the starting load of 15 W). Each athlete was asked to crank with a frequency of around 60 rpm. Although it is not a typical arm movement pattern (asymmetrical) for wheelchair basketball, it may be advantageous when practitioners wish to determine physiological capacities of an athlete in isolation from their equipment (Paulson and Goosey-Tolfrey, 2017). Additionally, due to ACE availability in many laboratories and because of low costs and portability of the device (Hutzler, 1998), it could be more applicable for regular aerobic testing performance in wheelchair basketball players. Rotstein et al. (1994) reported low correlations between peak oxygen uptake (VO2peak) and minute ventilation (VE) which were measured during movement on ACE and WCT (r = .57, p = .137 and r = .4, p = .233, respectively). However, Glaser et al. (1980) and Wicks et al. (1978) reported a high correlation between VO2peak, VE and peak heart rate (HRpeak) measured during movements on ACE and WCE. According to the study of Paulsen and Goosey-Tolfrey (2017), ACE is more mechanically efficient than wheelchair propulsion. Higher levels of peak power output (POpeak) can be obtained on ACE (~30% higher), with little difference in VO2peak. However, protocols performed on ACE have limited specificity to the type of movement of wheelchair athletes. Still, those protocols may be advantageous when determining physiological capacities of those athletes.
Therefore, the purpose of this study was to compare physiological responses during maximal exercise testing with the use of ACE and WCT in wheelchair basketball players.
Twelve elite male wheelchair basketball players (mean age 28.2 ± 7.1 years) volunteered to participate in the study. They were informed about the purpose and all testing procedures, and were asked to sign the consent form. All the procedures were approved by the local bioethics committee and were completed in accordance with ethical standards as described in the Declaration of Helsinki. The research was carried out in April 2017 during a training camp of the Polish National Wheelchair Basketball Team. The subjects were divided into functional classes (from 1.0 to 4.5) according to the International Wheelchair Basketball Federation (IWBF) procedures (IWBF, 2014). All the players were evaluated by international classifiers. The characteristics of the study participants are presented in Table 1.
Physical impairment and anthropometric characteristics of elite wheelchair basketball athletes
|Subject||Age [years]||Body mass [kg]||Body height [cm]||Vertical reach in a seated position [cm]||Arm span [cm]||Type of impairment||Functional level - class (1-4.5 CLASS)||Category (A-B)|
Anthropometric characteristics of elite wheelchair basketball players divided into two functional categories
|Category (A-B)||Age [years]||Body mass [kg]||Body height [cm]||Vertical reach in a seated position [cm]||Arm span [cm]|
|A (n=5)||mean 29.0||66.6||176.2||179.0||183.2|
|B (n=7)||mean 27.6||67.9||177.0||203.0||183.2|
Load progression in the wheelchair treadmill stress test (WCT test) and arm crank ergometer stress test (ACE test).
|WCT test||ACE test [km/h]|
|Stage||Time [min]||Speed [km/h]||Slope [%]||Speed [rpm]||Load [Watt]|
Comparison of results achieved by wheelchair basketball players representing functional categories A and B in the wheelchair treadmill stress test
|Category (A-B)||HRpeak [beat/min]||VEpeak [l/min]||VO2peak [ml/kg/min]||AT [beat/min]||Distance [m]||LApeak [mmol/L]||%LA [%]|
Comparison of results achieved by wheelchair basketball players representing functional categories A and B in the arm crank ergometer stress test
|Category (A-B)||HRpeak [beat/min]||VEpeak [l/min]||VO2peak [ml/kg/min]||AT [beat/min]||LApeak [mmol/L]||%LA [%]|
Comparison of results achieved in two aerobic tests performed on the wheelchair treadmill and the arm crank ergometer
|Measuring equipment||HRpeak [beat/min]||VEpeak [l/min]||VO2peak [ml/kg/min]||AT [beat/min]||LApeak [mmol/L]||%LA [%]|
|Wheelchair treadmill (WCT)||mean||193.1||130.5||45.4||167.3||12.0||52.7|
|Arm crank ergometer (ACE)||mean||191.4||131.5||47.4||164.2||11.1||59.5|
Correlations between results achieved in tests performed on the wheelchair treadmill and the arm crank ergometer
Additionally, the subjects were divided into two functional categories: A (players with class 1.0 – 2.5; n = 5) and B (players with class 3.0 – 4.5; n = 7). There were no statistically significant differences in anthropometric variables between players (except for vertical reach in a seated position).
Experimental procedures and measures
A personal data form was completed by all the participants. Prior to the main tests conducted in laboratory settings, anthropometric measurements were made and personal data were collected (age, body mass, body height, vertical reach in a seated position, arm span, and type of impairment). Body mass was evaluated using a medical scale. Body height was measured in a lying position on a mattress with the GPM anthropometer. Vertical reach in a seated position and arm span were measured in a sitting position (in a wheelchair) near the wall with the use of a measuring tape. Each athlete was asked to raise his dominant hand vertically to the highest attainable position on the wall without lifting the buttocks. The maximum vertical distance from the floor to the highest fingertip (when the hand was raised vertically to the highest attainable position) was recorded. The measurement error in each trial was ± .5 kg, ± .5 cm and ± .5 cm, respectively.
Two maximal exercise tests, i.e. wheelchair treadmill stress test (WCT test) and arm crank ergometer stress test (ACE test) were used to evaluate aerobic performance of elite male wheelchair basketball players (Table 3). The WCT test was performed on the WCT HP Cosmos Saturn. The participants used their sports wheelchairs. The sports wheelchair was connected to the metal frame for security. The speed and grade of the treadmill were increased simultaneously. The test started at 3.2 km/h and 0% WCT grade. The speed and grade of the treadmill were increased every two minutes (0-2 min: 3.2 km/h, 0%; 2-4 min: 4.8 km/h, 1.0%; 4-6 min: 6.4 km/h, 1.5%; 6-8 min: 8 km/h, 2.0%; 8-10 min: 9.6 km/h, 2.5%; 10-12 min: 11.2 km/h, 3.0%). The distance covered in the WCT test was registered for further analysis (Hartung et al., 1993).
The ACE test was performed on the ACE Lode (Groningen). To maximize trunk stability, the players used their own basketball wheelchairs and strapping systems as appropriate. ACE was firmly affixed to a wall-mounted gymnastic ladder. The ergometer rotation axis was set so that it was level with the subject’s glenohumeral joints. Two assistants stabilized the wheelchair to help minimize rotational movements during arm cranking. The breaking force in this test was increased constantly by 35 W every two minutes (with the starting load of 35 W). The players were asked to maintain cranking speed at 70 rpm.
In the WCT and ACE tests, the following physiological variables were measured: peak heart rate (HRpeak), peak oxygen uptake (VO2peak), minute ventilation (VE), anaerobic threshold (AT). The measurements were made using the K5 system (Cosmed, Italy) that consists of a mask and a portable unit worn by the participant. Breath-bybreath data were averaged over 15 s. The heart rate (HR) was monitored with a GARMIN sensor connected and compatible with K5. HRpeak was the highest value in the conducted tests, while VO2peak was the highest value obtained over 15 s. The AT was measured with the use of the modified V-slope method (Beaver et al., 1986). This modification concerned the method of obtaining AT results based on the lactate curve (a graphical method; the AT result was the intersection of the straight line (the load) and the curve (LA)). Lactate concentration (LApeak) and a drop in lactate concentration (%LA) were measured prior to performing WCT and ACE tests, during the tests (every 2 minutes), immediately after the tests and in the 3rd, 6th, 9th and 30th minute of recovery. The difference between LApeak and LA in the 30th minute of recovery was calculated to assess the ability to utilize lactate (a drop in lactate concentration - %LA). Moreover, the distance covered during the WCT test was measured.
All calculations and analyses were performed using the SPSS IBM Statistics 24 for Windows. The analysis of the quantitative data was based on arithmetic means and standard deviations (sd). The Kolmogorov-Smirnov test was applied in order to examine the distribution of results.
Results between players representing functional categories A and B were compared with the t-test for independent samples. The level of significance was set at p < .05. The t-test for dependent samples was used to compare results achieved in both physiological tests (WCT and ACE tests). The level of significance was set at p < .05.
In order to determine the relationship between the indicators for aerobic performance, the Pearson correlation analysis was performed. The correlation was significant at p < .05 and strong at r > .7.
The comparisons of results achieved by wheelchair basketball players representing functional categories A and B in both tests (WCT and ACE tests) are presented in Tables 4 and 5. No statistically significant differences were revealed between the players.
The comparison of results achieved in the two aerobic tests did not show any significant differences between the analyzed variables, i.e. HRpeak, VO2peak, VE, AT, LApeak and %LA (Table 6).
Strong correlations (r > .7) were observed between results achieved in WCT and ACE tests (Table 7). Correlations were confirmed between three variables, i.e. VO2peak, VE and LApeak (r = .825, r = .722, and r = .756, respectively).
The purpose of this study was to compare physiological responses during maximal exercise testing with the use of ACE and WCT in wheelchair basketball players. The main conclusion of this study is that there is no significant difference between the two approaches to assess aerobic capacity (VO2peak). It could be suggested that both methods are not analogous, yet they may be equally useful when determining VO2peak in wheelchair basketball players (Tørhaug et al., 2016). VO2peak values are similar but muscles that are involved in movement performance during both tests on various devices (ACE and WCT) are different because of movement specificity (Akinoğlu and Kocahan, 2017; Morrow et al., 2009; Paulsen and Goosey-Tolfrey, 2017; Rankin et al., 2011).
The results confirmed that both testing protocol performed on two different types of equipment (WCT and ACE) can be used for aerobic capacity assessment of wheelchair basketball athletes. There are some advantages and disadvantages of both protocols. The test conducted on WCT corresponds to the work performed by players while wheeling during the match (Bernardi et al., 2010; Goosey-Tolfrey and Leicht, 2013; Hartung et al., 1993). Moreover, the wheeling technique affects the test performance. In other words, differences in trunk stabilization or other functional abilities between players can exert a considerable influence on the level of parameters obtained during the test. Moreover, the type or quality of wheelchairs used by players as well as the type of strapping, belts or stabilization may determine WCT test performance.
During the WCT test, the treadmill grade and speed were increased every two minutes. That protocol seems to be more effective than those that involve increasing the grade or speed separately (Hartung et al., 1993). Still, that protocol seems to be more difficult due to problems with trunk stabilization in the last stages of the test. Moreover, a treadmill slope is not a natural condition when it comes to wheelchair basketball.
The test performed on ACE gives the opportunity to reduce the impact of the propulsion technique and differences between trunk stabilization on aerobic capacity (Tropp et al., 1997). However, the work done on ACE is not strongly related to performance during a wheelchair basketball match (Tropp et al., 1997). Another advantage of using ACE is that it can be easily transported to wheelchair basketball camps or training sessions. It is also worth noting that natural conditions of propulsion (symmetrical movement) on the treadmill could increase the advantage of this testing solution. On the other hand, in the treadmill protocol, speed as well as the angle of treadmill inclination were increased simultaneously and gradually. The increasing treadmill inclination during the test could affect trunk stability and the test results. In the ACE test, there were no disturbing factors. The advantages and disadvantages of both tests performed on two different types of equipment showed that coaches can choose the right test in order to meet their needs and achieve their training goals.
The duration of tests was similar in both protocols. The players performed both tests in 8 to 12 minutes, which allowed for proper analysis of aerobic performance variables. In both test protocols, the loads were increased every 2 minutes, what allowed for a comparison of variables in both test protocols was easier (LA concentration, HRpeak and VO2peak).
Aerobic capacity (VO2max) of able-bodied individuals is limited by cardiac output (Tørhaug et al., 2016). Tørhaug et al. (2016) indicated that it was not the load applied in a test, but the weakness of aerobic capacity of small muscle groups involved in the movement that limited the athletes in the ACE test (Di Blasio et al., 2009; Tørhaug et al., 2016). It seems likely that training these muscle groups prior to the test would be a good solution regarding aerobic capacity assessment in disabled athletes.
The present study revealed higher values of HRpeak and LA as well as lower values of VO2peak during the test on the treadmill compared to the arm crank test. It seems that wheeling, which is an everyday activity for most players, is a motor task that is similar to moving on a wheelchair on the treadmill. Wheelchair users are more familiar with this task than with arm cranking. However, in order to be able to compare aerobic capacity results from both tests objectively, it is necessary to calculate energy cost. Even though energy cost of movement is calculated, there are still some factors influencing or limiting players’ movement in each test. Therefore, it appears that the results obtained in the ACE test and the treadmill test can be compared. This idea was also introduced by Tørhaug et al. (2016), who added that the results were not comparable especially for submaximal levels of energy cost.
The findings of the present study were compared with the results of Swiss players (Knechtle and Kopøi, 2001). Mean VO2peak values from the treadmill test of the Polish national players were higher than those of the Swiss players (VO2peak 45.4 vs. 35.1 ml/kg/min, stress test on the treadmill) (Knechtle and Kopøi, 2001). No studies have been found regarding the assessment of physiological responses during maximal exercise testing with the use of ACE in wheelchair basketball teams. Therefore, the greatest achievement of this study is the indication of the possibility of using two test protocols interchangeably. Wheelchair basketball coaches may use not only the WCT but also the ACE test (Hutzler, 1998). Haisma et al. (2006) compared VO2peak results from a wheelchair ergometer and ACE tests obtained by people with spinal cord injury and they noted higher VO2peak values in the WCT test (Haisma et al., 2006). This difference could stem from population heterogeneity, i.e. inherent VO2peak levels of the study population (Tørhaug et al., 2016). On the other hand, Hintzy et al. (2002) reported higher levels of POpeak during the movement on the ACE (~30% higher) with similar values of VO2peak.
Muscle fatigue could be observed when lactate production in blood exceeded its elimination and reached the anaerobic threshold (Ghosh, 20074; Schneider et al., 1999). In our study, LApeak values were slightly lower in the ACE. It indicated that LA accumulation in blood was slower in the ACE test. It may have been brought about by the specificity of the task that differentiated between the work of the upper body on both devices (Di Blasio et al., 2009).
The fact that no differences were revealed regarding results achieved by players of different functional classes confirms that both protocols can be used for players of all classes. These findings seem to be crucial when testing wheelchair basketball players, as they can be compared regardless of their functional capabilities and types of impairment.
Both the ACE and the treadmill tests lasted between 8 and 12 minutes, which was in line with Perret and Abel’s (2016) recommendations. Due to different types of functional abilities of the examined wheelchair basketball players, the proposed test protocols seem to have been selected properly.
The limitation of the study was a small sample size of elite male wheelchair basketball players. We recommend that in future studies, the analysis should be divided into all eight functional classes. On the practical side, it seems important to search for non-laboratory (field-based) tests to assess the level of aerobic capacity of wheelchair basketball players. The application of such tests can be very helpful in coaching wheelchair basketball teams at each level. Therefore, there is a need to seek appropriate training methods that would improve aerobic capacity of wheelchair basketball players.
The main conclusion of the study is that both WCT and ACE tests may be useful when determining aerobic capacity of wheelchair basketball players. Moreover, both protocols can be used by athletes regardless of their functional capabilities and types of impairment.
The authors would like to thank the players and coaches from the Polish National Wheelchair Basketball Team for their participation in the study. The study has been supported by the grant from the Academic Sport Research from the Polish Ministry of Higher Education and Science (PB-87; N RSA4 01854) and funds for science of the Polish Ministry of Higher Education and Science in the years 2016-2018 (“Academic Sport Development” program); grant no N RSA4 01854 (“Optimization of controlling physical fitness of wheelchair basketball players”).
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