Which is not a factor in a safe fitness plan?

The factor of injury is not a factor in a safe fitness plan

Explanation:

The factor that is not involved in the safe fitness plan is that of injuries that takes place while exercising.  It is concerned with the rapidity and duration of an exercise. A rapid twisting fitness method can result in injuries.  Doing a vigorous or painful exercise should not be in the safe plan of fitness.  

Safe plans develop gradually, not very fast. So, a strenuous and extremely hard exercise is not an factor of fitness plan that are safe as it can lead to injuries.

answer; i believe that the correct answer is (participation);

which of what? i am confused