What's everyone opinion on this? My coach noticed that my cardio was lacking today, and my arms were burning out earlier than usual (I took a week off training to study for my exams). He suggested I run with handweights. I can imagine that there are pros and cons to this. Pros: Muscular endurance in arms and shoulders while improving cardio. Cons: Puts strain on joints. Even if I decide to do it, I am not sure how many times a week I should use weights when I run. I don't want any joint injuries. Also, I will be using two pound weights. Any input would be great, thanks!