I disagree with this statement. If you are punching (such as shadow boxing) and the weight are relatively low ( such as 2 or 3 lbs) It can actually be a big help for you in giving you the endurance to keep your arms up. The only thing I would caution against is throwing hard punches. DO NOT go tworads lockout with your punches but rather concentrate on using them to help your delts and not letting your arms drop. For this they have worked wonders for me. Good luck. They have caused no joint pain or problems for me and have actually helped me feel fresher and less tired in my training while sparring.