Posterior shin splints occur when you damage the posterior tibial muscles in the inside back of your lower leg. Some very good bicycle racers develop painful shin splints on the front inside of the lower legs when they try to train for triathlons. In a triathlon, you compete in three events: running, cycling and swimming. They have to stop running until they can run without feeling pain.
Bicycle riding develops very strong upper leg muscles because you pedal with your knees and hips. It does not stress your lower leg muscles much. Running stresses mostly your lower leg muscles. When you run, you land on your heels and raise yourself up on your toes with the calf muscles in the back and the posterior tibial muscles on the inside back part of your lower leg. So your upper leg muscles can handle the stress of running very easily, but your lower leg muscles are not strong enough and you tore them.
Once a runner develops shin splints, he or she has to stop running to let the muscle and tendon injury heal. A bicycle rider has to go back to the bike. When he can run without hurting, he should try to run on one day and cycle on the next and stop running immediately when he feels pain in his lower leg. When he can run for 30 minutes without feeling pain, he can start training again by adding fast runs. In the future, he should not run very fast more often than every other day or twice a week.