1. For a high-speed dismount for a set of hurdles, approach with your hands either on the brake levers, or, if you have top-mounted levers, on the tops. Unclip your right foot.
A ﬂat-out dismount is usually performed to clear a hurdle quickly, with a fast remount to get straight back into your stride. This maneuver takes skill and nerve, and it can save or lose you the most time as well.
Your speed on the approach to the hurdle depends on your confidence and nerve. In training, start off slowly, and increase your speed until you feel confident you can approach the hurdle at race speed.
2. Swing your right leg over.
This is how it works. First, forget about shifting gears. Assume that the terrain after the obstacle is similar to the approach; with proper technique, you won't lose enough speed to need a gear shift. Your hand position should be the one you feel most confident with.
The levers and the flat section on the tops of the bars are the favorite places for the hands during this type of approach. Perhaps it is best to reserve the tops until you have a very high level of confidence, as in this position last-minute braking is out of the question and you are committed to jumping off at approach speed. So try the levers ﬁrst.
3. Grab the top tube with your right hand and put your weight on this arm. Unclip your left foot and if still some distance from the hurdle, hover in this position with both feet unclipped until you are two steps' distance away.
Adjust your speed on the approach to give yourself plenty of time to swing your right leg over and get in position for the dismount.
You won't slow down much, but you don't want to be hurried into making a mistake. Your right leg will be behind and slightly to the left of your left leg.
Place your right hand on the top tube—again, two or three inches in front of the seatpost—and lean your body back. With your weight on your right arm, unclip your left foot from its pedal and land right foot ﬁrst on the ground.
4. Land on your right foot, take one stride, then clear the hurdle with your right leg first.
Lift the bike up with your right hand, while your left hand remains on the bars or brake lever, keeping the wheels straight so that when the bike hits the ground again it is under control. Clear the obstacle, put the bike back on the ground, your right hand back on the bars, and jump on.
Sounds easy, doesn't it? The tricky bit is taking as few steps as possible before and after the hurdle, because as soon as you are on foot, you are losing speed. The secret is the weight that you are putting through your right arm onto the top tube.
5. Pick the bike up vertically so it goes back down on the ground straight. Alternatively, if you are moving too fast to do this, then lick it out slightly, as Johnson has done.
The top guys tend to jump off, take one full step, jump the obstacle on the next step, take one full step after the obstacle, and remount on the fourth.
You may find that you need six or eight steps, but constant practice should give you the confidence to first try the dismount closer to the obstacle, and then faster.
When dismounting at speed, it's best to leave your left foot clipped in until the last part of the dismount. You can only do this with a high-quality pedal system and cleats in good condition, as they must release every time without fail; the consequences of a pedal that won't release as you approach a solid obstacle at 20mph are not good!
6. Take one more stride after the hurdle to put the bike down and get your right hand back on the handlebars. Remount the bike on your next stride.
The alternative is to unclip your left foot ﬁrst, before you swing your right leg over.
You must then position your foot on the pedal in such a way that it will not clip in by mistake, and hope that there are not any big bumps ahead that could make your foot bounce off the pedal.
Personally, I prefer to keep my cleats in good shape and unclip at the last minute, but the choice is yours.