activities and participation
Suppose you could examine a person's body in perfect detail and list every weak muscle and stiff joint, but you still had not watched them try to get dressed, cook a meal, or go to work. You would be missing the part of life that actually feels like living. The ICF gives this part its own home in two closely linked components: activities and participation.
An activity is the execution of a task by a person: standing up, walking, washing, dressing, writing, preparing food, handling money. Participation is involvement in a life situation as a member of society: holding a job, raising children, attending school, joining a religious community, playing in a team. When a person has difficulty doing an activity, the ICF calls it an activity limitation; when they have difficulty taking part in life roles, it is a participation restriction. The two overlap, so the ICF often groups them together, but the spirit differs: activities zoom in on the individual doing a task, while participation zooms out to the person embedded in a community. A useful distinction the ICF draws is between capacity (what a person can do in a standardized, ideal setting, like a therapy gym) and performance (what they actually do in their own real-world environment).
These components matter because they are where the goal of rehabilitation lives. Restoring a muscle is a means; the end is that the person can dress, return to work, and rejoin their world. They also reveal the power of environment: a wheelchair user with no change in their body can move from severe participation restriction to full participation simply because a workplace installs a ramp, an elevator, and an accessible toilet. The honest point is that participation is the hardest level to measure and the one most shaped by attitudes, opportunity, and society, not just by therapy.
In a therapy gym a man can walk 50 meters with rails (good capacity), but at home he never walks because there are no rails and the floor is cluttered (poor performance). The ICF captures both, pointing the team toward fixing the home, not just the legs.
Capacity is what you can do in ideal conditions; performance is what you actually do at home.
Participation is shaped at least as much by the environment and society as by the body. A ramp can lift someone from restricted to full participation without altering their impairment at all.