Why I prefer heart-rate straps on the arm, despite one common drawback - Velo
Optical HR Armband Shootout: Polar OH1+, Scosche Rhythm24, Wahoo TICKR FIT | DC Rainmaker
Taope Elastic Sport Heart Rate Monitor Adjustable Chest Mount Belt Strap Bands Fitness Equipment for Garmin Wahoo Polar - Black : Amazon.co.uk: Sports & Outdoors