Nine-year-old Will Martin loves baseball.“Nothing can keep him from playing,” said his mother, Michele Martin. “He just loves it so much.”While today he’s happy spending many hours a week batting and rounding the bases for the Midway Rangers, a few months ago he had to cut his fall baseball season short. Like thousands of children around the country each year, he suffered a concussion.Michele Martin said her son was visiting a friend in September, when he “jumped on a dirt bike without thinking to put on a helmet.”