How can I improve my cardio for rugby while also trying to add bulk?

The goal of rugby conditioning should be to keep it short and high-intensity. Your endurance will come from practice.Rugby demands both conditioning and power.  This means that both cardiovascular training and strength training need focus in a performance program.  For many, this means you must continue to add strength and bulk while not reducing speed or endurance.  Conditioning this type of athlete can be challenging.  The goal in the conditioning should be to keep it short and at a high intensity.  Your endurance will come more from practice than additional long runs, which will burn too many calories with few benefits. Limited cardiovascular training should be kept to under fifteen minutes in total time, while pushing the intensity and heart rate high for short periods of time (five to thirty seconds).  Add in equal amounts of rest until your workload (speed, distance, or watts) starts to decrease.  When your workload decreases, it is a sign of fatigue and you need longer breaks (one to two minutes) before repeating.  If you overlook the signs of fatigue, you can set yourself up for overtraining and injuries.