Board sports are examples of sports where the interaction of the task, environment and the athlete are essential. As for other sports, there are injuries and other issues associated with these sports, which affect performance and that can be avoided by proper preparation and well- designed equipment. By focusing on kitesurfing as a system structure the complex interactions between factors can help reveal which variables that are of interest to study to increase the level of performance and safety. Lack of research on the board sport kitesurfing makes this area interesting to study regarding performance and musculoskeletal problems. The purpose of this licentiate thesis was to further the understanding of on-water board sports, and specifically study kitesurfing by using a system analysis to structure factors that influence performance and injury risk for this board sport. The specific aims were:

To reveal the most common self-reported injuries related to kitesurfing and their causes (Paper I).

To evaluate in which body parts participants perceive musculoskeletal stress, pain and discomfort related to the performance of kitesurfing (Paper II).

To identify usability problems related to the preparation of kitesurfing equipment (Paper III).

To provide a system analysis to describe the relations between and identify characteristics that influence performance and injury risk of kitesurfing.

Methods used for these studies were hierarchical task analysis, observations (n=8), web- questionnaires (n=206), interviews (n=17) and a focus group (n=7). The system analysis was executed in six steps and based on ideas adopted from general systems theory, dynamical systems and ecological task analysis. Tasks performed in freestyle kitesurfing consist of riding a board and performing jumps and tricks, whereof the latter have sub-tasks involving take-off, acrobatic air movements and landings. Within the system of kitesurfing, there are the sub-systems athlete, kite system, board system and harness/protection. There are also external factors acting upon the system. All sub- systems have characteristics that are less changeable during execution of the task and which effect on the athlete can be represented by identified output measures, i.e. harness line force, board reaction force, steering force, pressure distribution, movement patterns, body temperature, fatigue level, comfort and pain, choice of sub-task, mood, stress level, concentration, motivation, experience and usability. The results show that the most frequent locations for injury are in the lower extremities, i.e. knee and ankle, and that about 50% of the injuries reported were associated with jumps and tricks. Equipment and environmental factors also contribute to injuries, as well as to musculoskeletal stress, pain and discomfort. The abdominal muscles were most frequently reported as exposed to high musculoskeletal stress, but also thighs and lower back were perceived as highly stressed throughout the tasks. Knees and feet were areas described as sometimes painful, especially in combination with landings from tricks or strong winds.

Furthermore, the lower back was reported painful when kitesurfing in strong winds. When hooking out from the harness for performing tricks, the shoulders were perceived as highly stressed. Before the execution of on-water kitesurfing starts, the preparation of the kite system must be accomplished. The results from Study III showed that there are usability problems related to this kitesurfing task, meaning risk for use error to arise. If use errors occur, serious consequences can follow later in the process. The results emphasize improvement of the products from a usability perspective. Some of the identified output measures were partly answered from the results of Papers I-III, where numbers of injuries, perceived musculoskeletal stress, pain and discomfort, and usability issues were evaluated for kitesurfing. The structure motives the need for further research within the area of on-water board sports and reveals variables that are affecting the system.