I’m a fan of caffeine for racing or hard training days. I see significant reduction in RPE and will typically do 400+ mg of caffeine via gels, usually taken during the earlier parts of a race. It doesn’t help everyone, but there are a lot of studies that show these benefits.
Here is my concern/question - Caffeine pushes my heartrate up ~8 beats per minute at most power levels. I think a rise in HR from caffeine is pretty common. So, while caffeine can make a given power level feel easier, it’s happening at a higher HR. It makes me wonder if the higher HR is an important contributor to the lower RPE because it’s pushing more oxygen to the muscles, etc. Regardless of how caffeine works, it’s driving a higher HR at similar power, and I have to believe there is a physiological impact as a result. While I am never consciously aware of fatigue of my heart, I assume the body regulates this to prevent it from being overworked at some point. Is there anything to this? Any science that backs this up?
At the core, I think my question is which of the following options is better/faster and can be sustained longer:
-Riding at tempo with a high dose of caffeine - lower RPE, but running a higher HR
-Riding at tempo with no caffeine - “normal” RPE and HR
Within this question, maybe the key question is whether increased HR has a negative effect on endurance or is there no measurable cost?
I’m not debating the value of caffeine in certain events. If I was doing a 40k TT or really any event under a few hours, I think the reduced RPE can help push performance to the max. For longer events, I question whether the reduced RPE ultimately comes at the cost of reduced endurance. Particularly early in a long race where I don’t need RPE to be lowered until late in the race.
I’m racing Leadville in a couple weeks and I’m locked in on my caffeine plan, but it’s definitely got me thinking about how it might help and hurt for a long event like this.