Three phases smoothed in one move
1° Start from a stand still, brakes full-on, shift your weight on the back wheel.
2° Lift the front wheel and push on the legs to jump, extending the arms before lifting.
3° When the back wheel takes off, pull your knees upwards and carry on lifting the bars.
After that, gravity pulls you back to earth, nothing special.
Try to land on the back wheel first, it's smoother. See this move in a video
Lifting the bike in a bunny hop or back hop?
Lifting the handlebars is the only trick, because your feet can't lift the bike. It looks like the feet are stuck to the pedals, but in fact they are just limiting the ascension of the bike. During the extension, the arms are kept low to keep the rear wheel pushing on the ground, but as soon as the extension is over, its time to fold back the knees with a synchronised pull on the arms upwards to lift the whole bike. All the move takes less than a second.
If you can't take off
There is a mix of reasons...Sometime, the problem may be that your effort to jump is in conflict with your effort to pull on the bike (like trying to lift a stone while standing on it). It's a synchro problem. The backhop in itself is not so useful (it drags you backwards). So to make the most of it, try to add a pedal kick to it. To do so, release the rear brake during the extension phase, while pulling on the bars. The pedal kick will also prevent you from moving backwards. If you are in good shape, and pull all your strength doing the right move, it's like doing gymnastic, you can jump high.
Then with the right move alone, and vague effort, you can still do a back hop a foot
high, which you could manage with plenty of muscle and very bad technique too...
Basically the better the technique, the less effort...It is really true, especially when bouncing
on the back wheel. The next step is to Bunny Hop over something.
The bunny hop is exactly the same move but without using the brakes, and while riding at some good pace.
Do it at any speed you like. Or try out some pedal kicks to move forward.
All the clips in one video.
(or right-click to download the .wmv file)
Going backwards for fun
That's a cool trick, though in order to build up your impulse backwards (without the front wheel support), you'll need to lean a lot backwards, nearly to the vertical before your jump extension. Push back both on legs and arms and then pull back the bike with you. You can turn in the air and land forward by giving it a twist during the extension. Send your shoulders spiraling as if you wanted to look back.
Useful after all
The backhop will eventually come up naturally as a safe way to bail off an obstacle when landing too short or loosing balance. In competition, failing to stay in balance on the obstacle you just climbed doesn't mean you dab a 5 (both feet on the ground). Instead, just hop back and land firmly on both wheels to stay on the bike for another attempt in the zone. That can also bring interesting combinations.