A:Answer If your heart rate jumps significantly e.g. when interval training and running or for other reasons (say from 90 to 170 in 10 seconds), then no wrist device would be accurate due to how they work (at least for now). I even tested this with a relatively large and accurate medical device with the same results. However, assuming no connection drop outs, the chest straps are usually more useful than wrist based optical types and will be sufficient if you gradually and gently increase load when on the treadmill. Which is what I would recommend if you have heart troubles i.e. no sudden increases in speed.
If you have a Garmin watch, then the Garmin "Premium Heart Rate Monitor" would be your best value option.
Good luck!
