Its interesting that you should bring up body types.
Consider Stefan Holm: http://www.youtube.com/watch?v=WVZ3ZcorTF0
His high jump record is 2.40, only 3cm shy of the indoor record. “Holm has the distinction of jumping 2 m or higher in six different techniques. With his height, being only 1.81 m, he shares the unofficial World Record of height jumped above own height (59 cm).”
Also have a look at this one: http://www.youtube.com/watch?v=IclEQA48IOE.
and this one speaks for itself: http://www.youtube.com/watch?v=zSGOZb2qwtM&feature=related
Height alone will not give your legs the ability to lift yourself off the ground, especially like in that first video. Its a combination of technique and physical training, both of which take years to master. The physical side involves building up strength and speed. This could often involve loading the muscles against increasing resistance to build up foundation strength (weighted squats, deadlifts etc) and then doing plyometric exercizes (eg box jumps, depth jumps, broad jumps, hurdles) to increase the power output of the legs.
Its also important to remember that jumping isn’t just a lower body activity. A lot of the upwards drive comes from the arms and core strength is vital in ensuring effecient energy transfer between the upper and lower body. Its this whole body technique that allows people to achieve great heights (so to speak). Consider the physique of a sprinter:
needless to say there is a lot of muscle mass in all parts of the body, which clearly shows the importance of energy transfer between all four limbs and the torso.
Now to the ‘you will get better at something by just doing it’ approach. Theres alot of truth to this but its important that you might not be maximising your performance increases and you will eventually reach a plateau. Do you think that this jump was soley achieved by practising that exact movement? At an olympic level, the training involved becomes more and more specific depending on the event the athlete is trying to master.
Of course there is no such professional standard for unicyclists. There are no coaches and no training programs. I’ve never actually ridden trials, but the basic theory seems the same. Practise the jumping movements over and over again. And don’t always just practise hopping close to your best height, practise everything. Its not just about increasing the strength and speed of your muscles, its about learning how to use your muscles in the way that will give you the best output. Over time you will develop muscle memory that will enable you to execute given movements in a better manner.
I’m sure there’s a lot of room for improvement for most riders, a bit of patience and hard work goes a long way. Eventually there is a plateau that will be reached. Part of the reason behind this is that unicycling only involves a given resistance - bodyweight and unicycle weight. In order to further progress strengthwise, you need to work your muscles against more resistance and repeat jumps near your max height to increase your power output. Then you will reach another plateau, where your body is just physically incapable of getting better and your technique is perfect. And THATS where steroids come in.
So in short, height or any other physical quality is no excuse. Ryan Atkins isn’t that tall is he