Iphones ipod + gym help

I use the gym 3 or 4 times a week and im now sick of my iphone at it. It used to constantly switch the voice control on until i switched that off but now it randomly turns the volume up and down without me asking it too. Help???

Why does it do this? is it to do with me sweating into the headphones?

Can it be resolved?

Any help will be masively appreciated!