Work-related means related to an event or exposure occurring within the work environment. An injury or illness is presumed work-related if an event or exposure occurring in the work environment is a discernable cause of the resulting condition or a discernable cause of a significant aggravation to a pre-existing injury or illness. The causal event or exposure need not be peculiarly occupational so long as it occurs at work. For example, a causal event or exposure may be outside the employer's control, such as a lightning strike; involve activities that occur at work but are not directly productive, such as horseplay; or involve activities that are not peculiar to work, such as walking on a level floor, bending down, climbing stairs or sneezing. Such activities, along with other normal body movements, are considered events. So long as the event or exposure occurred at work and is a discernable cause of the injury or illness, the injury or illness is work-related. It does not matter whether there are other or bigger causes as well, or that the activity at work is no different from actions performed outside work. If an injury is within the presumption of work-relatedness, the employer can rebut work-relatedness only by showing that the case falls within an exception listed in 225.15. In cases where it is not obvious whether a precipitating event or exposure occurred at work or outside work, the employer must evaluate the employee's work duties and environment and decide whether it is more likely than not that an event or exposure at work was at least one of the causes of the injury of the injury or illness.