Running is the most stressful sport on the body, as it is a 100% weight-bearing activity. It is important to run with proper technique for safety and to avoid injury. Running is the final leg of a triathlon, and you are most fatigued at this stage of the event. A large part of safety in running is ensuring that the core is strong, coordination is maintained, and components of your running (arm and leg motions) are efficient.

During your training, it is important to vary the surfaces on which you run, as running on one surface all of the time is a prescription for injury. Make sure that you train on varying terrain: hard and soft surfaces, up and down hills, on straight and curving trails. Running is the simplest and most accessible sport in triathlon; you can run almost anywhere, with anyone, at anytime, with a minimum of equipment. However, it is important to ensure that you have running shoes with adequate support, especially on hard surfaces. It is a good idea to do some barefoot running on soft surfaces, such as sand, to build strength in the muscles and tendons of the feet.

Running in triathlon

Running in triathlon does not only occur on the run leg. There is often a run to and from transition and sometimes in the middle of the swim. The most obvious running challenge is completing the run in a fatigued state after swimming and cycling. At higher levels, the musculature required for swimming and cycling must be adapted to in order to maximize running performance. Below are some running skills to practice while training.

- “Running off the bike”, which refers to running after cycling and swimming in a fatigued state.
- Running from the swim to the transition area. This distance varies from 20 to 40 meters, and may involve such different terrains as sand, grass, concrete, gravel; this is run in bare feet.
- Running with your bike in and out of a transition area, although not all races permit athletes to run in the transition areas.