The 31-year-old is healthy again and gearing up for the Rock 'n' Roll Philadelphia Half Marathon on September 21.
Try this workout from coach Brad Hudson to boost your fitness.
Kenyan Moses Mosop, second at Boston in 2011, also announces withdrawal from race.
Or are you satisfied with performing to 90% of your potential but with less chance of injury?
A strong international field will line up in The Windy City on October 13.
Seriously, everyone's doing it. Join the crowd.
The Olympic silver medalist booked his ticket to Moscow.
He dusted the field of 20 runners in the men's 5000m.
The Olympic silver medalist prevailed with a huge kick.
Peter Vigneron offers some ideas on how to spice up the sport and make it more entertaining.