Principles of Exercise: How to Get the Best Fitness Results
Progressions in ‘time’ and ‘type’ are inter-related
For instance, if you walk for exercise, and that is your ‘type,’ then you can increase ‘time’ from 30 to 60 minutes after it begins to get easy. But if the type is heavy weight training, then time increase may not be a good idea.
Instead, you can vary type by introducing new weight training exercises; for instance move from machine-assisted work to free-dumbbells work, move from wide base of support to narrow base of support, etc.