To a cyclist why is training with a power meter preferable to training with just a heart rate monitor?
A power meter records watts and watts don’t fluctuate, a watt is a watt. The instant you increase power it's measured instantly. Heart can fluctuate based on many variables, the quality of sleep or how much you've slept, caffeine consumption, hydration levels, illness, air temp. HR is also reactive versus instant. Meaning, that HR has a delayed reaction to the effort being applied. Also, there's something called cardiac drift in which your heart rate begins to drift as you train due to a number of factors. So, what does it actually mean when an athlete’s HR is up or down? The only accurate way to figure that out is by using a power meter. Training with Power takes out the variables, and eliminates guess work. Power is instant, and gives results immediately on how much work is being applied.