Triathletes often experience something called “heavy leg syndrome” when transitioning from cycling to running. There are two main reasons for this, cycling is quad dominate, while running involves a greater recruitment of the hamstring and calf muscles. Furthermore, the neural pathways used for cycling are different than those used for running. Your brain goes from telling your legs to move in a circular pattern during the cycling portion of a triathlon to supporting your full body weight as you transition to the running portion.
So, how do you negate these effects and become more efficient with your movement patterns as you transition from cycling to running?
In training, it is important to practice running immediately after the cycling portion of a workout. There are two variations of runs that can be performed: brick runs, which are runs off the bike longer in duration, and transition runs, which are shorter runs. There are many factors that should be taken into account when planning which of these two types should be incorporated into any training plan, including: experience level of the athlete, injury risk, allotted training time, their focused race distance, and the time of the season.
Triathletes who have a running background, or who have years of racing experience under their belts, may not spend a significant amount of time practicing transition runs. Their bodies have already become well adapted to the demands of running off the bike. You will typically see them practice brick runs (45 min or over, once per week). Less experienced triathletes and those at a high risk for injury do well with short transition runs. These are typically 2-3 miles, 25-30 minutes. Which of these options you choose will also depend largely on the distance you're training for. Shorter distance racers (sprint, Olympic) need to make a very quick transition off the bike into a solid “tempo-suprathreshold” effort and will benefit more from doing bricks or transition runs more often. Those training for Ironman and Half Ironman's may benefit greatly from doing aerobic brick runs.
As a coach, I do not have athletes do a significant amount of brick runs in order to avoid high amounts of training stress and injury. Instead, I have my athletes do more transition runs and focus their other running days on quality work. During the base phase (winter/building months) running off the bike should be limited and should pick up once an athlete is into the preparation and peak phases of training.
My best advice, practice both types of runs and see how your body adapts to the different demands of each, then practice accordingly!
A special thank you to our professional triathelete, Morgan Chaffin, for the information in this blog.