What kind of HRM is it? If it's a Garmin and using the soft strap, that's your issue. Solution: Buy the plastic hard strap like myself and everyone I know has done. Or spend hours on Google researching, then buy the cheapo plastic strap. http://www.amazon.com/Garmin-010-10997-00-Heart-Rate-Monitor/dp/B000UOD5QM/ref=sr_sp-btf_title_1_6?ie=UTF8&qid=1383158761&sr=8-6&keywords=garmin+strap