The Boston series has always been a favorite of those that wanted a shoe they could train in that was also fast enough to race in. The originals were almost as light as the Adios series but featured more forgiving cushioning. This made them a frequent choice among elite and sub-elite marathoners given their uniquely combined comfort and speed. All of that changed with version 10, which saw a complete overhaul of the series. Boost was replaced with Lightstrike and Lightstrike Pro. Energy rods were placed along the length of the shoe for stiffness. The stack height maxed out, making for what many saw as a completely different shoe. The Boston 11 continues this with a redesigned upper but maintains the changes in the sole that divided many Adizero Boston fans.