Analysis of Joint Range of Motion, Balance and Injury among Kitesurfers: a Cross-Sectional Study
1Child Health and Diseases Section, Istanbul Training and Research Hospital, University of Health Sciences, Istanbul, Turkey
2Department of Sports Medicine, Faculty of Medicine, Hacettepe University, Ankara, Turkey
3Department of Orthopaedics and Traumatology, Faculty of Medicine, Hacettepe University, Ankara, Turkey
4Orthopaedics and Traumatology Section, Şişli Etfal Hamidiye Training and Research Hospital, Istanbul, Turkey
5Sports Medicine Unit, Acıbadem Sports Excellence, Istanbul, Turkey
6Department of Sports Medicine, Faculty of Medicine, Istanbul University, Istanbul, Turkey
Keywords: Range of motion, balance test, sports injury, kitesurfing
Objectives: In kitesurfing, regular training programs are difficult to implement and also injury risk is high. In this study; shoulder, hip and ankle range of motion (ROM) and balance test results of kitesurfers were compared with healthy controls and the relationships between kitesurfer injuries, and ROM and balance test results were examined.
Material and Methods: For a total of 54 kitesurfers (aged 29.2±11.2 yrs) and 46 controls (aged 29.5±6.8 yrs), shoulder and hip internal (IR) and external rotations (ER), total rotation ability (IR+ER), ankle plantar flexion (PF) and dorsiflexion (DF), and the Y-balance test (YBT) were bilaterally measured and compared. The number, type and area of injuries of athletes after starting kitesurfing were noted.
Results: Bilateral shoulder IR-ER and right hip ER ROM were lower (p<0.001), whereas bilateral ankle PF was higher (p=0.013) in kitesurfers compared to the control group. YBT measurements were higher in all three directions in kitesurfers (p<0.001). At least one sports injury was reported in 55.6% of the kitesurfers. 50.0% of the athletes had experienced injuries requiring physical therapy and rehabilitation. 48.3% had only lower extremity, 20.7% upper extremity and 6.9% vertebral injuries, whereas 20.7% had both lower and upper extremity injuries.
Conclusions: The restriction of shoulder and hip ROM were thought to be depended on the intensive use of the shoulder, and hip stabilizers. The results of this study indicate the necessity of detecting high-risk groups by clinical and kinesiological examinations in kite surfers.
Kitesurfing, an extreme sport, which is defined as "A type of sport different from the traditional ones, which has unusual rules and techniques, where the individuals take risks and danger" has gained popularity very quickly (1). Kitesurfing combines aspects of surfing, windsurfing, wake surfing, snowboarding, paragliding, skateboarding, and sailing, and is considered to be a moderate or rigorous type of physical activity that can be done at almost any age (2). The International Sailing Federation (ISAF) and the International Kiteboarding Association (IKA) reported around 1.5 million people kitesurfing all over the world in 2012, and this number continues to increase every year (3). Kitesurfing has five different disciplines including crossing, free-ride, freestyle, speed racing, and wave riding. Crossing requires semi-isometric contraction movements, where abdominal and leg muscles remain under stress during hyperextension of the spine. Freestyle and splash are also characterized by increased hip flexion and hip and knee joint extension before landing. Knees and feet act as shock absorbers in landing. However, shoulders and wrists are the sites where the pain is felt most frequently (4).
Kitesurfers travel over the water surface with a kite (5-20 m2) connected to a harness on their waist with a 20-25m-long line and a board (120-200 cm) with footpads. Various maneuvers can be performed in the air by vertically lifting the kite and performing jumps up to 15m high and 30m long. The kitesurfer moves on the water surface by leaning back to the water surface according to the “upwind” or “downwind" position of the breeze, performing small flexion movements in the hip and knee and rotating the upper body. Scientific studies about this extreme sport, which imposes severe stress and strain on the musculoskeletal and cardiovascular systems, risk of injury, permanent damage and even death are limited (4-7). Since treatment of these injuries is difficult, time-consuming and expensive, it is essential to determine the possible biomechanical imbalances for injury prevention.
In kitesurfing, regular training programs are difficult to implement and preventive exercise programs are not available yet. To determine injury risk, it is essential to understand the association between range of motion (ROM) and the injury. ROM is determined by a number of anatomical, biomechanical and physiological factors (8). For this purpose, kitesurfers’ shoulder, hip and ankle ROMs, and balance test results were compared with healthy sedentary controls, and relationships with injuries were assessed.
Material and Methods
The study was carried out on sedentary healthy subjects (control group) and kitesurfers (study group) who had participated in the Maximum Kiteboard Turkey Open and the European Kitesurfing Competitions held in Istanbul in August 2017. Ethical approval was taken from the İstanbul University Faculty of Medicine (Approval date: 11.08.2016, number: 2016-13/16). A voluntary consent form was signed by all participants. Out of 200 kitesurfers, 54 Turkish kitesurfers volunteered. The control group consisted of 46 healthy volunteers who did not have any known disease and were not under medical follow-up.
Questions about "year and age of starting kitesurfing", "training status”, “history of injury (water/beach, training/competition, off-shore/on-shore)", "injury site", "contacting a physician", and "physical therapy and rehabilitation requirements" were answered by the kitesurfers. Shoulder and hip internal- (IR) and external-rotation (ER), total rotation ability (IR+ER), joint range of motion (ROM), ankle plantar flexion (PF) and dorsiflexion (DF) were evaluated with a standard conventional goniometer. Dynamic muscle balance was measured by Y-balance test (YBT). Participants with an active injury, using medications, or receiving physical therapy were excluded from the study. All analyses were performed minimum 12 h after training or competition without any alcohol consumption for at least 24 h. Male athletes were wearing sea-shorts, while female athletes had swimsuits or bikinis. Measurements were performed by the same physiotherapist in the beach facilities where the competition was held.
IR-ER was bilaterally measured in the active ROM within the range of 0-180°. Excellent reliability was reported for the manual goniometer as a measuring instrument for the upper and lower limbs joints (9). The YBT Kit (Perform Better, West Warwick, Rhode Island, USA) was used to evaluate dynamic muscle balance. It is consisted of three connected cylindrical tubular plastic bars marked in 0.5 cm increments. Each bar has a moveable indicator plate, which the subject moves by pushing with the toes, without bearing weight on the indicator. Three measurements were made for each lower extremity in each anterior, posteromedial and posterolateral direction and the most precise two results were recorded.
Statistical analyses were performed with the Statistical Package for the Social Sciences (SPSS, v15.0, IBM, Armonk, NY, USA). Descriptive statistics of the numerical data were reported as means, standard deviations (SD), minimum and maximum figures, while categorical data were represented as frequency (n) and percentage. For two independent groups, the Mann-Whitney U- and Student's t-tests were used. The Chi-Square test was performed to compare categorical data. The relationships between numerical variables were examined through the Spearman correlation analysis. The level of significance was set at <0.05.
A study group of 45 males and nine females, and a control group consisting of 37 males, and nine females were analyzed. The physical features of all participants are given in Table 1.
Mean age of joining sports in the study group was 15.4±9.0 years, while the mean kitesurfing starting age was 23.1±10.1 years. There was no difference in starting ages regarding gender (p=0.061 and p=0.990). In the study group, a positive correlation was detected between the length of the board used in kitesurfing and age (rho=0.376, p=0.008), height (rho=0.388, p=0.007), body weight (rho=0.523, p<0.001), and body mass index (rho=0.429, p=0.005). Mean measurements of both shoulders’ IR-ER and right hip ER were lower in the study group, whereas those for both ankles’ PF were higher than the controls’ (Table 2).
At least one sports injury was reported in 30 (55.6%) of the kitesurfers. No relationship was found between sex and injury (p=0.142). Of the athletes, 21 (70.0%) had a single site injury, seven (23.3%) had two injuries, and two (6.7%) had three injuries. About 28 (93.3%) athletes reported receiving medical support after injury. Additionally; of the injuries, 36.7% (n=11) were reported to require hospitalization, and 50.0% (n=15) needed physical therapy and rehabilitation. Twenty-three (76.7%) athletes mentioned that they underwent advanced MRI or CT scans.
When injury sites were examined, 48.3% (n=14) had only lower extremity injuries, 20.7% (n=6) had only upper extremity injuries, 6.9% (n=2) had only vertebral injuries, and 20.7% (n=6) had both lower and upper extremity injuries. Arm (20.7%, n=6) and shoulder (10.4%, n=3) injuries were most common among upper extremity injuries, while knee (37.9%, n=11) and ankle (20.7%, n=6) injuries were the most common lower extremity injuries. Muscle/tendon (57.7%, n=15) and bone injuries (34.6%, n=9) accounted for the most common injury types. The mean duration of training and the rate of regular physical activity were higher in athletes with previous injury history than in those without such a history (p=0.036 and p=0.048). Injury status and joint ROM measurements are shown in Table 3.
Relationships between joint ROM and YBT in those with multiple injuries are shown in Table 4. Left shoulder IR was lower in athletes with upper extremity injury than in those without an injury history (64.8±17.0 vs. 78.1±15.8, p=0.038). There was no difference in injury frequency concerning the dominant site (in both upper- and in lower-extremity injuries) (p=0.580 and p=0.928). In athletes with a history of lower extremity injury, hip IR/ER was not different from those without any injury history (p>0.05), and only anterior-left measurements were lower in the YBT (61.5±7.6 vs. 68.1±6.2, p=0.031).
Kitesurfing injuries are mainly acute (5). Overall injury rate was reported to be 5.9-7.0 injuries per 1000 kitesurfing hours in non-competitive kitesurfing, while this rate was 12 injuries per 1000 kitesurfing hours in competitive kitesurfing (10,11). The ankle (64%), foot (14%), knee (11%) and leg (11%) have been reported as the most commonly injured lower extremity sites (6). Upper extremities (18-22%) were the second most common site of injuries, followed by trunk (4-15%) and head (2-14%) injuries. Studies reported that the most common injury types were joint sprains (40%) followed by contusions (34%), abrasions (28%), and muscle or tendon damage (18%) (12,13). In this study, the frequency of lower extremity injuries was 48.3%, and both upper and lower extremity injuries were 20.7% in kitesurfers such as past reports. Lower extremity injury tend to be common because they all held weight and support balance. And arm injury was the most common site among upper extremity injuries while knee injury was the most common among lower extremity injuries because of that kitesurfing sports needed to use mostly arm joints softly and leg especially knee and ankle for turning on waves and keeping balance. Muscle/tendon injuries were accounted for the most common injury types. We thought that knee injury and hip health could be mentioned together.
In the literature, prospective (14) and retrospective (15) studies as well reported that hip muscle weakness is associated with knee injury (16). However, in this study, only the right hip ER in the lower extremity was significantly lower than in controls. Hip-abductor and external-rotator restriction leads to injury by altering trunk or lower extremity kinematics, resulting in increased mechanical stresses on joints and soft tissues (17). Hip-abductor and external-rotator weakness diminish the control of dynamic knee valgus by causing excessive femoral internal rotation and adduction (17-19). This may result in recurrent stress injuries such as patellofemoral pain and iliotibial band syndrome, or traumatic injuries such as a non-contact ACL rupture.
The low levels of mean upper extremity shoulder joint IR and ER ROMs may be due to the use of shoulder stabilizers to control the handlebar of the kite that they hold, which may lead to injury. The shoulder joint mechanism controls the position of the hand in front of the trunk and also controls the elbow joint to allow the motor function to be performed (20). Shoulder joint ROM, and IR/ER muscle strength are essential factors in performance, overuse injury rate and rehabilitation (21). In the shoulder joint with movement restriction, it was reported that the most recently acquired movement after standard physical therapy was IR, and most significant losses of both active and passive ROMs were in ER (22).
However, reduced hip ROM may lead to micro-trauma, joint contractures, and structural changes due to impaired kinematics of the hip and pelvis with an adaptation similar to IR restriction in the glenohumeral joint (23). In this study, we thought that the difference between the upper- and the lower extremities may be due to the intensive use of a right hip stabilizer to achieve balance on the surfboard, and protection from traumas by providing balance control on the right foot.
The YBT is a functional test that requires strength, flexibility, neuromuscular control, ROM, balance, and proprioception (24). The anterior, posteromedial and posterolateral directions have the most predictive ability for an increased injury risk (13). It was found that this test was predictive for lower extremity injuries in basketball players, and revealed chronic knee instability (25-27). Gribble et al. established that with a difference of more than 4 cm in anterior reach between the lower extremities, the individual is at a 2.5-times increased risk for a non-contact injury (9).
The high level of YBT measurements in the study group showed that their balance is quite high; therefore, kitesurfing has an advantage in this respect. However, bilateral posteromedial and posterolateral measurements were detected to be higher in athletes with an injury history than those without one. Additionally, there was no difference between the two groups in bilateral anterior balance measurements. Performance on dynamic balance depends on an individual's age, gender, sport, competition level, and motor development components (28).
YBT studies in the literature have been conducted about the mechanism, technique, and kinetics in sports such as basketball, football, volleyball, tennis, and swimming (26-30). YBT results obtained in competitive kitesurfers in this study may be the first ones performed in this sport. Therefore, according to technical and mechanical properties of kitesurfing, dynamic balance measurements may be different from other sports branches. We believe that this result will be a good reference for further balance studies in kitesurfing. At the same time, the results of this study suggest that YBT may be an inadequate measurement tool for lower extremity injury in kitesurfers, and internal/external factors that may affect the damage should be examined. Most common risk factors are bilateral strength imbalances, strength deficits, low agonist/antagonist ratios, muscle fatigue, insufficient warm-up, anatomical and morphological muscle features, poor lumbar posture, and core stability disorders (31).
YBT may help identify flexibility deficits and flexibility asymmetries in the ankle and hip regions (32). A correlation between hip IR/ER and YBT was detected in the present study. In the balance test of kitesurfers with multiple injury history, both hips IR+ER total ROM had positive correlations with PostlatR, PostmedL, PostlatL; and the right hip had an additional one with anteriorR. The relationship between hip strength and the YBT has not been fully elucidated. However, a weak correlation was detected between YBT and hip ER and IR forces (33). The results suggest that kinetics vary in kitesurfers and relationships should be assessed.
On the other hand, it was reported for competitive kitesurfers that bilateral ankle PF was higher than the controls, and that right ankle DF was lower than that of the left ankle. Data obtained from the measurements of PF and DF may be useful to determine the risk of anterior cruciate ligament injury in kitesurfers. Ankles with greater PF strength and smaller DF/PF ratio also had higher incidence of inversion ankle sprains (34). Besides, a restricted DF is associated with greater knee-valgus displacement during landing, because large ground reaction forces, valgus displacement, and limited knee-flexion displacement during landing are ACL injury risk factors (35).
We suggest that exercise programs and training plans recommended for kitesurfing should be extraordinary. Kitesurfing is a kind of sport that includes many components such as force, coordination, agility, and durability. Training should be targeted on practiced discipline, and a medium to high level of aerobic fitness is vital in course racing. In freestyle competitions, training should focus on exercises for proprioception, core stability, and articular mobilization to prevent possible injuries (5,13,36).
There are some limitations to our study. First, no question was asked to the participants about where the injuries took place. According to literature, 54% of the injuries occur in water at a distance >50 m to the beach, 26% occur at a distance of <50 m to the beach, and 20% occur on the beach (13). Additionally, no question was either asked to the participants about injury occurrence on-shore/off-shore (37). Second, injury frequency per 1000 training hours was not be evaluated in the study group. Most of the time, athletes can spend time waiting for wind on the beach. This situation complicates the planning of studies and makes it difficult to obtain injury data per 1000 training hours. In this study, injuries that occurred any time after onset of kitesurfing were examined, regardless of how they occurred.
To conclude, to the best of our knowledge, this is the first documented study that examines the relationships between shoulder/hip/ankle ROM, YBT measurements and injuries in kitesurfers. Results support the necessity of regular check-ups to identify high-risk muscle injuries in kitesurfers. Kitesurfers should be assessed using clinical and kinesiological examinations. We hope that the results of this study will guide research in determining possible injury mechanisms, and creating injury prevention strategies in kitesurfers.
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