i have read 10 secs and 15secs have also read 15 is too long. wich is it plz?

30 seconds

Yeh i hold a stretch for 15-30... more so the last one.. get your self warmed up and stretch those muscles..

My hamstring injury is a perfect example of NOT doing longish stretches!

oh so all of what ive read is rubish ok guys thanks. this must be why i keep hurting my self  

After you stretch your body part you've just done should feel more relaxed..more mobile.. dont stretch on a cold muscle tho.. that leads to injury..

do a few mins very easy cardio at the start to get the body warmed up if your prone to injurys then a good stretch out.

My instructor tells me, for example before doing bicep curls, to take the lightest weight (5kilos here) and do 15 - 20 slowish reps, to warm up the muscle, before the real WO starts.
Similarly for chest presses etc.

Yeh very true..

For each new exercise i do a warm up set.. ie dumbell curls..1 warmup set..then if preacher was next..first set is a warm up set..

ok guys thanks good info