Does putting in some cardio time after a weight training session delay your recovery? A study published in the International Journal of Sports Medicine attempts to answer that question by comparing the effects of both types of training to an aerobic training session lasting equally as long.
Researchers had 10 healthy male subjects undertake a combined resistance training and cardio session or stick with aerobic training for the same amount of time. An analysis of knee muscle strength found that the combined workout decreased maximum torque by 6.8% while the continuous cardio reduced output by 17.3%.
The length of recovery was not significantly different. So give yourself a good 48 hours per muscle group and kick-start the recovery process with a carbohydrate-protein smoothie.