The BEST times to do prolonged cardio sessions are after your strength training workout and on rest days.
You CAN do cardio before a strength workout, but only as a warm-up tool, for ~5-10 minutes.
If you do a 30+ minute cardio session before a strength workout, chances are you will perform suboptimally afterward.
This is due to the fact that prolonged cardio sessions deplete muscle glycogen, which is essential for optimal athletic performance.
To perform best at your strength workouts, make sure to load up on carbohydrates and only do cardio as a warm-up.
Your transformation coach