streching cardio lift questions

yes you do need to stretch before and after.
before warms your muscles up and helps prevent injuries
afterwards it helps your muscles recover quicker

I am not a fitness expert, but here is what I've gathered through research and what works for me.

There are different kinds of stretches that should be done before and after exercises. Before exercising, focusing more on loosening, warming, and readying your muscles for the workout. This means you should focus on mobile stretches (hip/arm/knee circles, easy jumping jacks, walking, reps at 25-50% weight, etc). This will prepare your muscle for movement. Static stretches before exercise can actually break the muscle down and cause you not to be able to deliver a peak performance. It can also make you more susceptible to injuries.
However, static stretches post-exercise are a plus. Your muscles are warm already, they've been moving, so a deep stretch can be executed without as much risk of injury. As mentioned above, these stretches can help break down the muscle, which is good once you're muscles are already worked for the day, as it is a necessary step in building muscle. Static stretches post-exercise will also help you keep your muscle from getting to tight and causing cramps/splints/spasms, etc.

I hope this helps!

Excellent advice Thedreamhazer! I would add that from what I've heard there is no data to support the old addage that stretching before excercise prevents injury. Warming up before intense excercise is definitely a good thing, but static stretching likely isn't. One version of a routine would be to do a warm up (7-10 minutes of cardio), then stretch, then lift or do your major cardio work.