We strongly recommend consulting your physician if you are injured or pregnant prior to starting a vigorous workout routine.
If you have an injury you can still do the workouts by modifying the exercises to your level and ability. You always have the option of cutting reps or weight or just using your bodyweight for many exercises. You can also take more breaks and go at your own pace. Keep in mind that if you cannot perform all the reps of a move properly with perfect form and without pain, you should modify and adjust the exercises accordingly.