How can I avoid calf muscle cramping in the run after the bike ride?
Many issues an athlete has during the run can be traced back to the bike, especially if you do not cramp up when you run without biking first. My first suggestion is to look at your foot angle during each pedal stroke. Do you point your toe? If not, check to make sure your seat isn't too high or too far back forcing you to "reach" for the bottom of your arc. If your bike position is good, your foot angle is good, and you have a comfortable bike fit, then look at your biking shoes to ensure they are appropriate for the type of riding you are doing. If you still have calf cramping, slow down during the last 5 minutes of your bike leg and get off your saddle. Stand on your pedals and complete a modified calf stretch. Since calf tightness can be a result of problems higher in the body, stretch your hamstrings and lower back as well. If using aero bars, make sure you have a professional properly fit your bike to you. Diet can also play a large role in cramping, so make sure you eat appropriately for your training and racing routine.
First, look at electrolyte consumption and hydration. What are you drinking and eating? Other causes could be some issue with bike fit or running shoes, of course.
Good question. Lets start with defining what causes cramping. The answer is... no one really knows. The scientific literature has not found a single cause for cramping. Many theories exist; dehydration, loss of salts, eating too much... The reality is that all of these factors can contribute to cramping.
However, the most likely candidate for what causes cramping is fatigue of the nurons that send the electrical impulses from the central nervous system to the muscles to tell it them to contract. Those nurons are used to firing a little and then resting a lot.
During a long ride, you perform the same motion over and over again. The brain sends the same signal time after time to the point that the neuron becomes fatigued. This happens because the neuron never gets to a point where it is truly "resting." Finally, the brain decides that it has had enough and it sends a "cramp" signal to the muscle. This forces you to stop what you are doing and rest the neuron.
So, strategies to use...
Change what that muscle is doing from time to time. In other words, the electrical impulses used to signal "walking" are different than those that signal "running." So, for longer runs, I have my athletes walk the aid stations. This is not a slow stroll. This is a strong, purpose driven walking stride. Just 30 seconds worth.
During the bike, change positions from time to time. Get out of the saddle, sit up, stretch the legs.
As you come into T2, shift down and spin, stand up and stretch. The few seconds you lose here you will make up in spades later in the race.
Finally, you need to practice bricks in the same environmental conditions in which you will be racing. If you race in humid, hot conditions, you must do some of your bricks in these conditions to allow you to acclimate.
Finally, increase your fluid and salt intake prior to longer training sessions and races.