How do some insects jump so quickly? As anyone who has tried to catch a grasshopper or a planthopper knows, many insects can jump very rapidly. A planthopper can accelerate in less than 1 millisecond to a take-off velocity of 5 m s–1, requiring a power output (energy per given time) of tens of thousands of Watts per kilogram of muscle. To do this, jumping insects have to overcome two mechanical limitations. First, the maximum mechanical power a muscle can produce is only approximately 300 W kg–1 and furthermore, the faster a muscle contracts, the less force it can generate, exacerbating the problem. Second, a jumping animal can only accelerate while it remains in contact with the ground: in most small insects, therefore, the length of the propulsive legs determines the time available to reach a given take-off velocity.