Dynamic stretching, as opposed to static, is always the best option before training. During exercise you are not likely to stretch the muscle as far as it can go and hold (excluding a few gymnastics and martial arts movements), so it doesn’t make sense to do any such thing when preparing them for a workout.
Exercise typically involves a rapid and repetitive stretching and contracting of muscles. That is the key behind dynamic stretching. You should use light weights to dynamically stretch and contract the muscles using movements similar to those that make up your exercise routine. This will also warm the muscles up.
Be sure to use light weights. For the stretches in the above video I recommend the following:
Men – 2kg/5lbs
Women – 1kg/2.5lbs
Complete 10-12 explosive reps of each movement and your chest, back, shoulders, triceps and biceps will be ready for action!