I was wondering if was OK to use a barbell instead of dumbbells for this workout. Also, could you explain why you chose to use dumbbells for this workout instead of a barbell.
The main reason I use dumbbells for this workout and most of the other workouts in this program is because this is a strength training exercise program with an emphasis on calorie burning. Because the program can be done in 12 days, it was very important for each and every workout to work synergistically to burn calories and stimulate lean body tissue efficiently.
There are pros and cons to using dumbbells and barbells. One of the pros to using a barbell is that you can use heavier weight. Using heavier weight is important in building absolute strength. Gains in absolute strength can reap rewards in your fat burning goals down the road. The problem with using a barbell in a workout like this is that it can be a little difficult and time consuming to switch between weights. Dumbbells work well in a workout like this because it is a little easier to switch between weights. Your body will actually work a little harder using dumbbells because while you work the main muscle, smaller muscle groups have to help stabilize and balance the weight. This works well to burn extra calories.
Ultimately, the most important thing is that you get the workout in. If you are more comfortable using a barbell or that is all you have access to, by all means use it. The choice of dumbbells or barbells make a relatively small impact on the success of the program compared to the order of the exercises and method in which they are implemented.