How heavy is 10kg??

Tonight, I'm on my exercise bike, pumping away on the pedals, when a brilliant (?) idea pops into my head.

I'll ride the last 10 minutes of my session with a 5kg dumbbell in each hand! (as I said...brilliant!) 

By the time I'm at 38 minutes (2 to go) I'm swearing and sweating and swearing some more. 

And then it hits me.

I used to do EVERYTHING with two and a half times this weight on my body. How did I function that way? I thrashed out my 10 minutes and put those bastard weights down. I will NEVER go back to where I used to be.