Ball between the knees?

[rayening]

I've recently started riding, and my instructor told me to sit with a football between my knees whenever I'm watching tv or on the computer.
I don't actually have a football though.. living in a place with no garden, and being someone with absolutely no interest doesn't really warrant one!

Could I use my helmet as a replacement? Granted, it may be a little bit wider than an average football but it would do the same thing no?
Just wanted to make sure that I'm not doing this for nothing when I could easily go out and buy a cheap ball!
I can feel the burn in my thighs already.

 

[Fides]

It's good for strengthening your quads. Just do 3 mins or so at a time a few times a day. I suppose a helmet could work but it doesn't have any 'give' in it so may be up comfy?

 

[rayening]

My thighs are very squishy at the moment, so there's quite a bit of give
I guess for the next few days it will be alright.

Might see if anyone is selling one of those springy things secondhand instead..

 

[MiJodsR2BlinkinTite]

Go get yourself a gym ball - I got one from Lidls for £6.99. Then go on here and have a look:http://www.fittoride.org/ A football is good: you need some...o think the football is cheaper in that case!