Most triathletes are familiar with the sensation of heaviness in the quads as they leave the bike race and start to run. This is known as Heavy Leg Syndrome, and it is the main reason why running in a triathlon is so different to running fresh. With practice, and by incorporating the appropriate exercises into a training plan, triathletes can improve running off the bike and decrease the effects of Heavy Leg Syndrome.

Three Causes

Bicycling causes the blood to be mainly directed to the quads in what is known as a vasodilatory effect in the blood vessels and capillaries that service the muscles. When a triathlete goes to run, the blood is still in the same area, causing the quads to feel “heavy” until blood is redirected to other muscles used for running, such as those surrounding the hamstrings and calves.

A second cause of Heavy Leg Syndrome has to do with neural innervation patterns. The message to pedal in circles is sent to the leg muscles via neural pathways. In a transition to running, this message is suddenly changed, and the legs are told to support the competitor’s body weight. In other words, the triathlete starts to run before body is given a chance to respond.

However, it is possible to train the body in to speed up this adaptation and make running off the bike far easier. To do this, triathletes must incorporate certain methods specifically designed to reduce Heavy Leg Syndrome into their weekly training program.

Train to Reduce Heavy Leg Syndrome

Sports fitness site Active recommends beginning with at least one brick session per week, ideally incorporated midweek. Bricks consist of a moderately long bike ride followed by a moderately long run. These workouts force the legs to become accustomed to the transition by learning to fire the appropriate neural pathways and move the blood from the previously active to currently active muscles faster.

As the competition draws nearer, triathletes should substitute brick training with transition sessions. These workouts combine all three aspects of the triathlon (running, swimming, biking) in either a sequence or mixed structure. Each exercise lasts three to five minutes and is performed at race pace threshold. The process is then repeated either two or three times. In addition, the triathlete should complete a short run after every bike session; even as little as 800 meters is sufficient.

Another way to strengthen legs and prepare for transitions without experiencing Heavy leg Syndrome is to practice hill running; this movement requires more use of the quads and gluteals than when running flat. As these are the same muscles used for bicycling, hill running can help improve performance in both disciplines and make transitions easier.

Transition to a Running Mindset

During the competition, there are further ways to avoid Heavy Leg Syndrome that should be practiced in training. When the triathlete is five to eight minutes from finishing the bike race, he or she needs to shift into a running mindset. Active recommends the following preparation:

  • Change to a slightly higher gear and ride a couple hundred meters standing out of the saddle. This movement is similar to running and allows the blood to be redirected to the appropriate muscles,
  • Sit back into the saddle and switch to a lower gear to allow the legs to spin more effortlessly,
  • Finish the bike race while stretching the muscles needed for running such as the hamstrings, calves and lower back.

Running off the bike naturally becomes easier in time, as the triathlete has competed in more triathlons; however, this process can always be sped up to reduce the risk of Heavy Leg Syndrome with adequate training and preemptive competition tactics.