It is very common to see people exercising on the treadmills before their strength training routine. If your primary goal is to exercise your heart and lungs or if aerobic training is just what you like to do, then disregard my recommendations.  But if it your goal is to improve body shape it is more advantageous if you do your resistance training before the aerobic training.  Toning or sculpting basically means getting rid of fat while increasing or holding on to muscle.  The fuel found within the muscle necessary during resistance training will be depleted if aerobic training is performed first which hinders most of its benefits.  Resistance training coupled with the right nutrition is what keeps or increases muscle ,and  muscle is what burns fat.  Fat doesn’t just dissolve like magic.  It needs a place to be taken to and converted to energy, and the place is the mitochondria found within the muscle.  If you interfere with muscle you interfere with the fat burning mechanism.  It’s ok if you use the treadmill for a little warm up.  Make sure you don’t tap into the muscle reserves and you’re on your way to a healthier you.