I don’t do a brick workout very often, and when I do, the run off the bike is always a short one.  I did a brick workout this evening, that consisted of a 75 minute bike ride, followed by an easy 20 minute run.  That is very typical of my brick workouts.

Most people do brick workouts as part of their training.  They are done for three main reasons:

• Bricks help you get used to the feeling of running after biking.  When running off the bike, your legs do feel strange.  It feels like you are running with terrible form. In reality it is just your body getting used to a different motion in your legs.  The motion on the bike is very different to a running motion.  By the end of the first mile off the bike, this feeling goes away; often sooner. 
• Many people do very long runs off the bike, to get used to the feeling of running on tired legs.  In reality, if your training program is set up correctly, there will be times when a regular run, occurs on tired legs.  You don’t need to make your legs super tired by biking hard before your run.  Save the long run off the bike for race day.  Doing it during training, increases the risk of injury.
• The final benefit of a brick workout, is that it allows you to practice your transition skills.  This is very critical for shorter events, where you don’t want to waste time between events.

So I only do a short run, as part of a brick workout.  With a short run, I get to feel the unusual sensation of running off the bike and I can also practice transition skills.  I chose to get my ‘running on tired legs’ practice elsewhere.