How to reduce static with kids on the trampoline?

We recently got our new trampoline, and our girls have been using it a lot, but there's one problem: it's a breeding ground for static electricity, especially in the afternoon. Static hair is the worst problem, because the girls practice gymnastics on the tramp and this builds up a lot of electricity in their hair. Shocks is another. When they touch each other, the metal springs, and sometimes even the net, they get nasty shocks. One time my youngest daughter was coming off the trampoline and touched the metal pole and got such a big shock it startled her. How can I solve this problem to make times on the tramp less dangerous?