Not sure what you mean by keeping them active. Most mantises use camouflage to hunt and avoid predators so it's in their nature to stay still. Certain mantises like Creobroters and Hierodulas are more prone to hunting actively, but even they will stay still for long periods of time. The only thing you could try is keeping them on the warmer side of their temperature ranges, they'll be more active than if they were kept cold.