In which condition do symptoms often initially occur only after exercise?

The symptoms of osteoarthritis often manifest initially after physical activity due to the nature of the condition itself. Osteoarthritis is characterized by the degeneration of joint cartilage and the underlying bone, commonly exacerbated by weight-bearing movements or strain on the joints. When an individual with osteoarthritis engages in exercise or any form of repetitive stress on the joints, they may not experience pain or discomfort until they have been active for a period, as the synovial fluid and joint structures may initially provide some cushioning. However, following exercise, inflammation and joint stiffness often set in, leading to noticeable symptoms.

The other conditions listed do not typically have exercise-related symptom onset in the same way. Diarrhea can occur due to numerous causes but is not dependent on exercise for onset. Insomnia is related to sleep disturbances rather than physical activity, and the term inconclusively does not pertain to a specific medical condition. Thus, the defining characteristics of osteoarthritis align well with the condition in which symptoms typically occur after exercise.