Wheelchair sports are the oldest and most representative of all disabled sports (Brittain, 2004). With recent advances in science and technology, wheelchair sports are receiving increasing attention, not only as means for facilitating rehabilitation and self-reliance but also as sporting events (Malone et al., 2000). Some well-known wheelchair sporting events include basketball, track and field, tennis, table tennis, dance sports, badminton, and boccia (Keogh, 2011). Most athletes in these sports acquire their disability from an accident or illness rather than from a congenital disorder (Brittain, 2004; Campbell and Jones, 1994; Li et al., 2018). Wheelchair athletes tend to be older because many of them begin participating in sports long after the onset of their disability (Blauwet and Willick, 2012). Therefore, national team players are older, and there are very few young athletes.

The number of registered athletes for wheelchair badminton in Korea is 10 times lower than those in China and Japan, as athletes on the national team tend to be in their late 40s and have >20 years of experience. Meanwhile, the mean age of reserves for the national team ranges from the late teens to the early 20s, indicating a generational gap within wheelchair athletics.

Despite such challenges, Korea has achieved excellent results in many international competitions for people with disability, thereby increasing its national prestige. Recently, the Korean team won two gold, three silver, and three bronze medals at the Thailand Para-Badminton International 2017; three gold, three silver, and six bronze medals at the World Championship held in Ulsan in the same year; and three gold, one silver, and three bronze medals at the Jakarta-Palembang 2018 Asian Games. This was made possible by the efforts of the athletes, coaches, and head coaches, as well as the various forms of sports science support.

The objective of this study was to compare performance-related physical fitness factors and anaerobic power between national and backup players in training programs for enhancing the performance of wheelchair badminton players in preparation for the 2020 Tokyo Paralympics.

Besides, this study was conducted to help the generational replacement of the aging wheelchair badminton players.

Table 2 shows the comparison of performance-related physical fitness parameters between the national and backup players. Muscle endurance was significantly different between the groups (supine pull-up test: U=3.00, P=0.047). Cardiorespiratory endurance, muscle strength, power, and agility were not significantly different between the groups but were higher in the national players than in the backup players.

Table 3 shows the comparison of anaerobic power between the national and backup players. Peak and mean power values showed significant differences between the groups (peak power: U=0.000, P=0.003; mean power: U=1.00, P=0.005). No statistically significant differences in fatigue index were found, but the national players had lower values than the backup players.

In this study, differences in fitness levels between the wheelchair badminton national and backup players were measured to provide individualized training programs designed to enhance performance.

The results revealed that the national players showed a higher level of cardiorespiratory endurance than the backup players. These findings were not consistent with those of the studies conducted by Steinberg et al. (2000) and Morgulec et al. (2006), which reported little difference in cardiorespiratory endurance among athletes with disabilities because the activities of the sympathetic nervous system, which regulates cardiovascular responses, are restricted in cases involving spinal cord injuries at or above the T6 level. This restriction results in suppressed secretion of epinephrine, which limits the stimulating factors for increasing heart rate, stroke volume, and ventilation when exercise intensity is increased. By contrast, the findings in the present study support the results of the study by Soyupek et al. (2009), which showed that cardiorespiratory functions improve after exercise training in patients with spinal cord injuries. Therefore, enhancement of cardiorespiratory endurance is important for wheelchair badminton players, suggesting the need for continued training to enhance cardiorespiratory endurance in these athletes.

The national players showed a higher muscle strength than the backup players. In addition, the national players showed significantly greater muscle endurance than the backup players (P>0.05). These findings are in agreement with those of Yüksel (2018a; 2018b), who reported that muscle strength and endurance were higher in experienced athletes. Bernard et al. (2004) reported that most wheelchair athletes had a spinal cord injury accompanied by a brachial plexus injury; as a result, neurotransmission is blocked, resulting in the formation of less motor neurons that relay signals to the muscles and decreased muscle contraction. In particular, for wheelchair athletes who compete in sports that require open motor skills such as rugby, basketball, tennis, and badminton, building muscle strength and endurance is highly important to maintain power and strength to execute repetitive dynamic skills and movement within short intervals, while also operating the wheelchair (Goosey-Tolfrey et al., 2010). Therefore, individualized strategies for improving the strength and endurance of muscles essential for enhancing performance are needed.

The national players tended to show higher levels of quickness and agility than the backup players. This was possibly due to the difference in experience and ability in operating the wheelchair in response to various positional changes on the court and impacting the shuttlecock through fine manipulation of the racquet. Haff et al. (2001) and Hakkine (1994) showed the importance of individualized programs for building speed and agility in the upper extremity muscles in sports such as wheelchair badminton. Future studies based on such findings are needed to demonstrate the effects of training programs with different levels of intensity.

The national players also showed significantly higher levels of peak and mean power in the anaerobic power measurement and fatigue index than the backup players. Anaerobic power showed a large difference depending on the performance ability of the athletes (Franchini et al., 2005). The findings were consistent with the results of a study by Sucharitha et al. (2014) that compared anaerobic power between national and amateur female badminton players. They reported that the national players showed greater anaerobic power. Wheelchair badminton is a typical sport that requires anaerobic exercises, in which a rally to win a single point may last between 10 sec and 2 min. Therefore, anaerobic power can be viewed as an important factor for enhancing the performance of athletes; therefore, training programs designed to enhance anaerobic power, along with other fitness factors, should be promoted.

In summary, development of individualized training programs for enhancing performance and preventing injuries among wheelchair badminton players is needed. Also, national wheelchair badminton players are aging, and the low number of players is a problem. To solve these problems, efforts should be made to increase the number of white hope along with the revitalization of disabled sports for all to expand the base of wheelchair badminton, and double the camping training period of the backup player training center, so that they can grow into a national team by conducting continuous training and managing the athletes.