Competitive sports for disabled individuals have entered into a fast development process during the recent years. These sports have gained a place in a wide spectrum reaching open athletes and elite athletes. Paralympic games have raised awareness for the participation of disabled individuals in these sports. These games form an exercise characteristic for preventive health and improve cardio-metabolic aptness. Furthermore, they develop social integration of the disabled individuals by improving their self-confidence, self-competency and life quality (Blauwet and Willick, 2012). Wheelchair (WC) basketball is the most popular paralympic sport (Gil-Agudo et al., 2010). This sport consists of activities demanding explosive strength and speed and intermediate intensity (Ozmen et al., 2014).

WC-use requires the active and coordinated usage of upper extremity muscles especially shoulder complex muscles actively and coordinately. The shoulder flexors make the major contribution during WC-pushing stage and the shoulder extensors are dominant during the return stage. There is increased shoulder muscle cocontraction seen during the passage stage between these two stages (Morrow et al., 2009; Rankin et al., 2011).

The upper extremity injuries are seen in WC-using individuals considerably (Boninger et al., 1998). Shoulder pain is the most frequently seen complaint (Fullerton et al., 2003). Finley and Rodgers (2004) reported in their study conducted on WC-using individuals that the persons suffered shoulder pain caused by many reasons including biceps tendinitis and shoulder instability, and 29% of these people had pain during relaxation as well. Curtis and Black (1999) showed in their study that 90% of women WC basketball athletes had shoulder and upper extremity pain. Muscle strength unbalance in the shoulder region and relative weakness in the depressors of humeral head can be affective for the development and continuation of rotator cuff compression syndrome (Burnham et al., 1993). In addition to shoulder complexities, elbow and wrist injuries occur frequently in WC athletes. Wrist extension and wrist joint movement speed with deviations are the factors affecting dynamic performance and causing injuries (Lee et al., 2016). Both wrist extension and flexion movement gap and muscle strength are the factors affecting performance of WC basketball players (Wang et al., 2005).

High level of condition is required for winning a competition in WC basketball like in all sports. The major factors affecting WC basketball performance are muscle strength and sprint speed. Having high level of muscle strength in WC basketball will ensure both performance improvement in basic movements unique to basketball and independence in daily life activities. The objective of this study was to reveal the isokinetic muscle strength characteristics of upper extremity in WC basketball athletes. The descriptive information will lead to the description of injury-preventing programs and more specific training programs.

This study was conducted to reveal upper extremity isokinetic muscle strength characteristics in WC basketball players at the Ministry of Youth and Sports, Sports General Directorship, Health Affairs Department Directorship (Athlete Training and Health Research Center). All the athletes who accepted to participate in the study were informed about the study purpose, the assessments contained in the study and the benefits of the study before starting the study and the study was based on volunteerism, and approval was obtained. The necessary permit and approval was obtained from the Ethics Committee of Ankara Yıldırım Beyazıt University to conduct the study (13/03 [346]). The participants in the present study consisted of 12 male WC basketball players, aged 23–40 years, who are members of the Turkish national WC basketball team and their scores ranged between 2.5–4.5. The descriptive characteristics, age, height, weight and disability types of the athletes were recorded.

Demographic characteristics and disability types of the athletes are shown in Table 1.

The peak torque values and peak torque/weight values of dominant - nondominant shoulder flexion and extension movements of the athletes and wrist flexion and extension movements at 60°/sec and 240°/sec velocity, and the angles of these values and repeat times are shown in Table 2.

The extension peak torque was found to be higher than the flexion peak torque in the shoulder joint, and the flexion peak torque value was higher in the wrist. The peak torque values were generated with 2–3 repeats at 60°/sec velocity at both movements for the wrist and shoulder. It occurred at 240°/sec velocity with an average of 5–6 repeats for both movements, and it occurred at 3–4 repeats for the wrist. Considering the angle values where the peak torque value is generated, it was at 60°/sec velocity in the shoulder joint as similar in the dominant and nondominant sides approximately 81°–86° and 112°–109° for flexion and extension respectively. At 240°/sec velocity, it was 110°–97°; 108°–106°. For the wrist, at 60°/sec velocity, it was approximately 16°–24° at flexion and at 5°–6° extension as similar in the dominant and nondominant sides respectively for the flexion and extension; at 240°, for flexion and extension, it was respectively 22°–25° flexion and 13°–6° extension.

The percentages of the shoulder and wrist flexion/extension movements of the athletes at 60°/sec and 240°/sec velocity for the dominant and nondominant sides and between the right and left, and the standard deviation values are shown in Table 3.

The extension isokinetic muscle strength in the shoulder joint was higher than the flexion isokinetic muscle strength, and the flexion isokinetic muscle strength in the wrist was higher than the extension isokinetic muscle strength (Table 3).

In this study, the peak torque, peak torque/kg, right/left ration percentage and flexion/extension ratio percentage of WC basketball athletes were determined.

There are two studies in the literature assessing isokinetic muscle strength in healthy individuals. Danneskiold-Samsoe et al. (2009) categorized according to age and gender and measured the wrist flexion and extension and shoulder flexion and extension at 60°/sec velocity, and Harbo et al. (2012) published two studies determining isokinetic muscle strength in 178 healthy individuals at angular velocities that were different than ours (Danneskiold-Samsoe et al., 2009; Harbo et al., 2012). Moreover, Moon et al. (2013) published a study evaluating isokinetic muscle strength in WC tennis athletes as similar to our study. Our values at 60°/sec, and the flexion and extension peak torque values for the dominant and nondominant sides of Moon et al. (2013), and the shoulder and wrist flexion and extension peak torque values for 20–29 age group and 30–39 age group of Danneskiold-Samsoe et al. (2009) are shown in Table 4.

The peak torque of the shoulder flexion and extension in WC basketball athletes included in our study was approximately 2 times of those of the healthy participants in Danneskiold-Samsoe et al. (2009) study and also of WC tennis athletes in Moon et al. (2013) study. It is thought that this outcome is caused by the fact that WC basketball sports requires intense upper extremity muscle strength for coordinated movement of WC and ball, and these athletes are included in the Paralympic class. Danneskiold-Samsoe et al. (2009) found in their study that the wrist flexion/extension ratio was close to 1 in healthy individuals, and in our study, it was determined to be almost 1/3 in the favor of the flexors. Despite a high wrist flexor strength seems to be in favor of the athletes; it must be remembered that the muscle strength imbalance between the wrist flexors and extensors will be a preparatory factor for sports injuries. It was seen that the athletes had tennis player elbow complaint in their backgrounds as parallel to our results. We think that providing information on this issue to athletes and health team, and establishment of training programs for strengthening wrist extensors will prevent overuse injuries. There are numerous studies in the literature showing that individuals become prone to injuries due to muscle imbalances (Blauwet and Willick, 2012; Knight, 1980). Since there were only the peak torque data in Danneskiold-Samsoe et al. (2009) study, peak torque/kg and other characteristic data were not able to be compared. Isokinetic assessments vary according to angular velocity. Therefore, it is not possible to make a comparison with this study since Harbo et al. (2012) assessed the wrist in angular velocities different than ours. The flexion/extension difference and right and left difference in our study are shown in percentages in Table 3. These data are critical for the existence of a balance between agonist/antagonist muscle forces and the disruption of the balance make the person prone to injuries (Knapik et al., 1991). Perrin (1993) found this ratio as 75%–85% for shoulder flexion and extension in their study. In our study, this ratio was found as approximately 71.2% as parallel to this result.

Hughes et al. (1999) assessed the antagonist/agonist ratio between the wrist flexion and extension in their study and concluded that there was not a significant difference between the dominant and nondominant sides. In our study, we found that the wrist flexion/extension percentage in both sides varied between 260%–331%. The difference was outside of the normal limits and we suggest that the wrist extensors are strengthened and muscle imbalance is overcome to prevent sports injuries due to muscle strength imbalance.

Kannus (1994) reported in their study on isokinetic assessment that more than 10% of difference between the right and left extremities was abnormal. In our study, it was determined that the difference between the right and left side at the shoulder flexion and wrist extension at 240°/sec velocity was more than 10%. Therefore, workout programs must be added to the training programs to improve the strength for right and left bilaterally in activities requiring speed for especially the shoulder flexion and wrist extension. This puts forward the significance of neuro-reactive workouts in the training programs.

The results of our study and the percentages between the right-left and extension/flexion in Moon et al. (2013) study conducted on WC tennis players are shown in Table 5. It was seen that the percentage of the right-left flexion and the percentage of the dominant side flexion/extension in WC tennis players were higher than those of the basketball players included in our study. We think that this difference is caused by the inclusion of WC using athletes by both groups however tennis is more asymmetric in comparison to basketball.

In addition, in our study the repeat number and angles where the peak strength occurs are indicated. In our study, there were athletes reaching the peak torque in the first repeat, there were also athletes reaching the torque strength at the 14th repeat. The peak occurred at 60°/sec velocity for the shoulder and wrist flexion and extension at an average of 2–3 repeats; and the peak occurred at 240°/sec for the shoulder flexion and extension at the fifth–sixth repeat, and it occurred at the third–fourth repeat for the wrist flexion and extension. This outcome of our study shows that the repeat number must be increased as the assessment speed increases. Studies need to be conducted on this issue with high number of athletes.

It was determined in our study that the peak torque occurred at the angles when the shoulder was in an elevated position and at the angles when the wrist was at a functional holding position. We think that this angle was affected by the fact that the athletes were basketball players and basketball throwing position affected the angle for peak torque generation in the wrist. In this context, the angles where the peak torque is generated should be considered when training programs are established.

The limitations of our study were failure to compare the peak torque values according to the disability type and age due to the low number of athletes.

In conclusion, WC basketball sport is the most popular one among paralympic sports branches and in Turkey. It is a critical tool for the rehabilitation of disabled persons and their integration in society. WC basketball sport is exercised at a professional level in the world and Turkey. Prevention of sports injuries is important in WC basketball like in other sports branches. The workout and training programs is an issue that needs attention for both prevention of sports injuries and achieving high performance in this sports branch. As our study revealed, determination of characteristics of muscle strength of WC athletes and especially using objective isokinetic tools will be guiding for the training program planning and prevention of sports injuries in long term.