The benefits can also extend to the skeleton. As Professor Alister Hart, an orthopaedic surgeon at UCL, notes: “The kneecap has the thickest cartilage in the body because it takes the greatest load.” In his MRI studies, runners who followed the four-month London Marathon training plan – with modest weekly increases, strength work and recovery – showed no joint deterioration during the plan, and some improved. “Bones need impact, they strengthen through it,” he says.