Why 6 Weeks to Return to Sport?

In a word, scar tissue formation.

Interestingly, the way the body deals with an injury is by forming scar tissue. We repair, and we do so with remarkable alacrity. The process of the scar both becoming stable and tolerant of tensile stress is pre-determined. Assuming everything goes well, there are very specific time lines.

• Between 0 and 4 days, there is no prepair per se', just bleeding
• Between 4 days and 15 days the construction of the "scaffolding of repair" takes place. This scaffolding is not tolerant of tension, but it gradually picks up strength
• By day 21, the scar achieves 15 percent of its final tensile strength. This is good because at three weeks loading is important to help organize the scar and make it as strong as possible - more of this later.
  
• By day 42, six weeks, the scar achieves about 40% of its final integrity, and there is much that one can do on a scar like that has achieved this level of tolerance without irritating the injury.
• And by day 90, the scar achieves 90# of its final integrity.
  

The process that the scar undergoes, building of a scar from the initial injury, is significantly impacted by the introduction of tension. The reason for this is that the cells that build scar, fibroblasts, have a pole like the earth has a pole, and with intermittent tension, the cells align themselves parallel to the lines of stress, and the scar tissue fibers they lay down are also placed parrallell to the lines of stress. This leads to a stronger and healthier scar that is tolerant of stress as those fibers bond with adjacent fibers.