Transitions between the triathlon legs play important roles in competitive performance because they force the body to adjust to changing physical demands. By understanding the workings of human physiology and by practicing preparatory skills, a triathlete can use these transitional intervals to improve overall performance.

Many competitors have difficulty running at peak levels immediately after getting off of their bikes. This results from the fact that a great deal of blood is supplying oxygen and nutrients to the prime muscles of cycling before transition. Running involves the use of different muscles that require their own supply of oxygenated blood.

In fact, all three triathlon legs place different stresses on the body’s limited blood supply because they require the use of different muscle groups. A muscle at peak activity may utilize as much as 100 times more oxygenated blood than it needs at rest. That means the body must divert blood from other areas to supply active muscles. By prompting this blood diversion during transitions, a triathlete can encourage the body to have smoother starts and quicker finishes. The body has its own self- regulating mechanism of valves and shunts that controls the supply of oxygenated blood at all times. The autonomic nervous system regulates this flow through its sympathetic and parasympathetic functions, sending blood where it is most needed at any given time. The sympathetic branch speeds up heart rate and opens up the blood vessels to the muscles and diverts blood from the gastrointestinal tract. The parasympathetic lowers the heart rate and shunts blood directly to the digestive system.

Competition for Blood Flow

Sympathetic and parasympathetic functions can come into conflict when muscular exertion, such as running, competes with digestion of a heavy meal. The stomach needs blood to process food as part of normal metabolism. So, parasympathetic impulses will normally divert the necessary flow. Conversely, running requires sympathetic impulses to send blood to the leg muscles.

Since sympathetic impulses will always override parasympathetic processes, the act of running interferes with the digestive process by diverting blood from the stomach. This explains why a competitor may experience a stomach ache or nausea after consuming too many carbohydrates before a race or a strenuous training session. Muscular exertion robs the stomach of the blood it needs for digestion, causing physical distress.

Another common difficulty resulting from blood- supply limitations is typified by the dizziness experienced when one stands up quickly from reclining position. Gravity naturally pulls blood to the legs when one stands up too quickly. This momentarily compromises the supply of oxygenated blood that can reach the brain. In the few seconds required for the cardiovascular system to adapt to the new position, the individual will experience lightheadedness.

The Body in Transition

The trick to good triathlon performance is getting blood to the necessary muscles before the supply is overwhelmed by need. This means getting blood to the arms and shoulder during a swim, to the quads and glutes while cycling, and to the hamstrings and calves during a run.

Mental and physical preparation can enhance triathlon performance and lower race time by teaching the body to divert blood flow in a timely manner. The first transition takes place at the starting line where blood must be shunted to the swimming muscles during the sprint to the first buoy. By swimming slowly before the start of the race, the triathlete can make a progressive transition that does not overtax the blood flow. The harder and the shorter the distance, the longer one needs to warm up.

While waiting for a race to begin, a triathlete should keep blood flowing to the muscles. This is accomplished by shaking loose the arms and legs. Extreme mental tension can shunt blood from the extremities through overwhelming sympathetic nervous impulses, which is why it is important to remain calm and avoid pre- race panic.

On the other hand, one must avoid being too detached at the starting line, lest parasympathetic impulses cut off the blood supply to vital muscle groups. To achieve the appropriate mental state and promote proper blood flow before swimming, the triathlete should practice calming self- talk, while visualizing warmth flowing to the extremities.

The next transition occurs after finishing the swim when the triathlete sprints to his/ her bike. Most competitors experience leg weakness when they begin the run because the blood flow takes time to shift from the shoulders and arms to the hamstring and calf muscles. Additionally, the cardiovascular system must adapt from the body’s horizontal position during swimming to the vertical posture of running by reorganizing the blood flow.

The best way to prepare for this transition is to avoid a hard sprint in the last 100 yards of the swim. The triathlete should keep a steady pace in the last few minutes of the swim and mentally prepare for the next leg of the race by monitoring physical activity.
This mental imagery will help the body begin to regulate and redirect blood flow. If legs feel weak and rubbery at the start of the run, the triathlete should avoid panic because this anxiety will further tax leg muscles by unnecessarily closing down their blood vessels.

Cycling, Running and Finishing

It is extremely important to give the body time to prepare for the cycling portion of a race because it is generally the longest leg of competition. The triathlete should ride in high cadence and relax during the first few minutes on the bike, allowing oxygenated blood to be efficiently shunted to the quads and glutes. A buming sensation and fatigue may be felt in the thighs and hips, but should not cause alarm. This sensation is part of the cardiovascular system’s adaptation to the new activity.

The competitor also should avoid consuming excessive calories at the start of the cycling leg because digestion will drain limited cardiovascular resources. All of these transitional aspects between swimming and cycling should be incorporated into the pre- training routine to get the nervous system used to the necessary physical and mental demands.

The change from the bike to the run can be the most challenging transition and is a frequent cause of decreased triathlon performance. To ease the rigors of this change, the triathlete should avoid consuming excessive calories toward the end of the cycling leg to prevent the shunting of blood from the legs to the stomach. It is important to relax and ride at a steady pace, while mentally reviewing a checklist of conditions for the next transition.

In the first few minutes of the run, the competitor should give the running muscles a chance to receive oxygenated blood. There is no reason to panic if legs become fatigued and lactic acid builds up quickly. This build- up helps the body to shunt blood to the hamstrings and calves. Controlled imagery can also play an important role in encouraging the blood flow in the right direction. Pre- race training sessions should include running at race pace after getting off a bike.

The last transition comes between the final sprint to the finish line and the war stories generally shared with buddies at the end of the race. After completing the last leg, the nervous system needs time to shift from a hard sympathetic response to an easier, relaxed parasympathetic function. The triathlete should jog and walk after the finish to avoid stopping suddenly. Transition also should include a few minutes of rest before overloading the stomach with food and carbohydrate- rich drinks.

Bruce R. Wilk of Miami, Fla., is a board- certified physical therapist and director of Orthopedic Rehabilitation Specialists. He completed his first Ironman- distance triathlon, the Great Floridian, in 1995.