So I've been using an HRM on the trainer for a while now, and noticed something. With my hands on the bars, I'll be spinning along at, say, a nice steady 160 bpm. If I sit up and take my hands off the bars, and hold the same cadence and resistance level, my HR immediately rises about 5 or 6 bpm and stays there as long as I stay upright. When I drop back to the bars, the HR drops back to its original level. Has anyone else noticed this effect, or know the reason for it?
Two possibilities I've thought of:
- pedaling with hands off bars uses different muscle groups that aren't as efficient
- upright posture forces heart to work harder to get blood to head