Lennard began his relationship with Dr. Andy Pruitt, the founder of the Boulder Center for Sports Medicine and pioneer of medical 3D bicycle fitting, as a fellow bike racer and as a patient being treated in 1982 for a torn gastrocnemius muscle. Over the years, they collaborated on many bike technology innovations. In 2012, Zinn customers gained the option to have Andy, the guru of bike fitting, do a full medical fit of them for their custom bike before it was built. When the bike was done, they could also do a followup fit with Andy on their new bike. Andy Pruitt retired in 2018 and Zinn Cycles continued to do 3D bike fits for customers at the Boulder Retul Center.