Strength training and conditioning is a very important part of parkour, because for many moves strength is needed. This will become clear if you are trying a climb up (0.00 - 0.05 minutes, You can't always use the technique. Than you only have your arm power). With a good technique it can become easier but strength and condition is still needed. Furthermore it's allows you who handls new situations. As the motto of parkour is “being strong to be useful” you probably also want to be able to carry an unconscious person out of a danger situation. This is also an example where strength and condition is of great importance. Furthermore being strong can prevent injuries very well. The best example is David Belle who never brook a bone because of his strength and conditioning trainings.
As the legs and foods are used to absorb the impacts from drops and sometimes the arms as well (for example by a diving parkour roll), it is obvious that this muscles need to be strengthen. However these are not the only muscles which are important doe to injury prevention. Abdominals and back muscles are also very important as they keep the back straight during landings etc. This prevents it from a landing with a convex or hollow back during the landing which can even led to invalidity. The hands and fingers are also very important as it could be that you jump to short to land on something but instead you only can grab the top of it. In this case you need to have strong hands and fingers to prevent you from falling down and even more muscles to get away from the situation (eg. climbing to a lower drop, climbing up etc.). This shows that it makes sense to train every muscle.
In parkour the strength training and conditioning is manly done by bodyweight conditioning. The following three movies from Northern Parkour (Obsidian1138) show a lot of ideas how you can do bodyweight conditioning.


The shown exercises are not the only exercises which can be done. It is possible to experiment and modify exercises so for example there are not just push ups, but it is also possible to change the distance between the hands (both hands together or with a big distance), moving the upper body from the left to the right and back, move the body forward and backwards but keeping the tips of the food on the same place, put one food over the other and do push ups, jump into push up position etc.

If you are doing strength training and conditioning there are some things you should keep in mind:

• You can make a training very efficient by doing a exercise 10 times as often or long as you can do it normaly
• Muscle pain will appear about 24 hours after the training and is good, if it does not take a week to disappear. It is a clear sign that the muscles are getting stronger and that you should give this muscles some rest.
• Don’t train the same muscles two days in a row, especially not if you expect muscle pain from the first training.
• If you have musclpain after the day of training, the muscles need 48 - 72 hours rest in order to recover and become stronger than before.