The burpee is the ultimate conditioning exercise, and it's one you've likely encountered in a group fitness class before. I'm an instructor at Epic Hybrid Training Centre, an obstacle-course based HIIT facility, and I assign my fair share of burpees to our clients.
There's certainly a love/hate relationship with this particular movement, but whether you like it or despise it, here's the common mistake I see most people making when they do a burpee: they don't really jump at the end of the movement.
It's usually because they're tired or they're trying to conserve their energy, but whatever the case may be, you're missing out on a really good spike in your heart rate and added strength work for your legs. The next time you're doing burpees, as you come up from the floor, fully extend your arms and jump as high as you can. Yes, it will be harder, but it will be really worth it in the long run! You'll get added conditioning, and your legs will get more toned.