While acknowledging the preliminary scientific research indicating that young players who head too early in their physical development are susceptible to potential risks," Ouellette says the act of heading "should be regarded within a complete context of risk."
Instead of setting a particular hard-and-fast age at which heading is introduced, he recommends a more flexible approach: that a "general rule of thumb to follow is to start teaching heading when a player shows an interest, not when the coach thinks it should be taught."
Stuck in the middle with you
In the middle are experts like Chris Koutures, a pediatric and sports medicine specialist in Anaheim Hills, California, and lead author of the AAP's youth soccer study.  Although welcoming SLI's discussion of heading in soccer and commending its efforts to enhance study and ultimately the safety of young athletes, Koutures said he was personally disappointed that the SLI White Paper made no reference to the AAP youth soccer study: "I thought that the paper has good insight and the AAP truly wants to be a point of reference in matters of pediatrics and sports medicine in particular."
Koutures noted that youth soccer was not alone in contemplating or legislating delays in introducing higher risk activities, but warned about the downsides of doing so "without solid evidence bases of support to determine actual benefits," and without consideration of potential risks that "delaying certain actions might actually increase injury risk." Echoing Dr. Meehan's concerns, Koutures wondered whether "kids who don't learn a skill until later might not be as adept/competent, and that could increase risk of concussion and other injury."
In ice hockey, Koutures pointed to data from a recent AAP study  which definitively showed that delaying body checking until age 15 did not increase injury risk before or after the age. By contrast, he noted that two pilot studies examining the effect of limiting full-contact practices in youth football [36,37] have yielded inconsistent results about the effectiveness of such measures as a primary concussion prevention strategy.
"Where the science is lacking is the ability to definitively state that delaying heading will reduce both short-term and long-term concussion burdens, and won't actually increase the risk of concussion or other injury," said Koutures. He noted that even though the AAP report on youth soccer injuries  advanced the consensus opinion of the authors on the importance of neck strength and delaying introduction of heading until appropriate biomechanical control of head, neck, and chest could be obtained, the evidence to support the statement was lacking at the time of the paper's publication. "That evidence still does not fully exist today," Koutures said.
"One could accurately argue - with good scientific support - that restricting heading (at any age) could reduce concussion, because the mere act of going up for a header is itself associated with a risk of concussion, due to head/head, head/shoulder, and head/ground contact. This might be even more definitive at older levels of play where stronger, faster, and more experienced/confident players going into heading contacts with more speed, determination, and even intent to harm. However, if kids aren't as comfortable with the act of heading, there might actually be more risk, not less."
"Many of my discussions about sport safety (and head injuries in particular) revolve around acceptable risk, risk tolerance, what we know and do not know about the injury in question, potential risk reduction techniques (helmets, not heading, switching to a non-heading position), and alternatives (less risky activities)."
"Does [the recent research] make me want to restrict heading or express more caution? Not quite yet, though I have brought it up in clinical conversations when discussing risks/benefits of soccer with young patients and their families. If I were sitting in front of a young soccer player and his/her parents to discuss risks/benefits of delayed introduction to soccer heading, at this time I could not summon up enough evidence to categorically support delayed introduction, but am eager to continually review evolving studies and share thoughts with others," Koutures said.