If I sense a band member struggling with tempo and ask them to tap their foot, they usually cannot. I'm not saying that nodding your head or tapping your foot is mandatory, but, if you're not feeling the tempo, trying to tap your foot is a dead give away. Someone who's feeling the tempo, especially through fills, can tap their foot no problem. Someone who's losing it through fills or turnarounds will have inconsistent tapping as they lose the tempo.
