Depends on the type of burnout, but I would caution about doubling down on exercise.

For two reasons:

1: It can be an attempt to avoid working through the issues that led to the burnout. Sometimes it can be like replacing one addiction with another.

2: Exercise is stress, and burnout is a reaction to prolonged stress. Moderate exercise can help, by elevating mood. Heavy exercise in burnout can lead to prolonged fatigue and CFS like symptoms.