My friend who is an amateur bicyclist participated in a bicycle race conducted by a company I"'ll call "A". During the race, my friend was hit by an automobile. He claims that employees of "A" improperly allowed the car onto the course. "A" claims that it cannot be held liable to my friend because he signed a release exculpating "A" from any personal injury resulting from his participation in the race. Is the exculpatory clause effective?