There is dynamic stretching and static stretching. Dynamic is best for post-workout, while static is best for in between sections and post-workout. This is very important, because doing static stretches before a workout can cause injury, since it lowers your muscle’s temperature. 

Dynamic stretching means your body is constantly moving while you’re stretching. We do this in warm up, and its purpose is to prepare your muscles. You need to warm up your muscles before they can safely stretch – raising the temperature increases the elasticity and makes them more powerful. Benefits include:

• Warms your body up for different types of movement, which we know we do a lot of during class. 
• Gives you time to mentally prepare for what’s to come – honing in on that mind-body connection.
• Improves the range of motion around your joints, reducing risk of injury! This will eventually improve your performance and maximize your movements. 

Static stretching are holding stretches, like what we do after leg work or combo. These are best suited for post-workouts or cool downs, which is why we place them at the end of each section and make them specific to whichever muscles we just worked. Benefits include:

• Improves flexibility by moving joints through specific range of motion
• Lengthens muscles
• Relaxes muscles after fatiguing them  

As always, links to full article are below:

http://www.bodyscapesfitness.com/the-benefits-of-dynamic-stretching-vs-static-stretching/

http://www.shape.com/blogs/weight-loss-diary/best-way-stretch-and-after-workout