Some Hard Truths About Soft-Tissue Injuries

Heading into the opening game of the season last year against the Bears, the Packers listed three players on its injury report with hamstring problems. The 31 other teams had just 21 combined. Then we watched Christian Watson lose most of the season, while key players such as Aaron Jones, Eric Stokes and Jaire Alexander all were shelved for varying periods. 

The Packers, and Watson himself, are sending optimistic signals this year, touting their work with experts at the University of Wisconsin. But hamstring injuries have plagued Green Bay, and the rest of the league, for decades with only marginal improvement. The reality is that despite being a non-contact injury, reducing it in number and severity remains elusive. On average, an estimated 175 hamstring injuries occur in the NFL each season. No team has cracked the code. 

“Everybody’s aware this is a problem, and nobody out there has a magic formula,” Stephania Bell, a physical therapist and ESPN injury analyst, said in a 2018 interview. “The No. 1 risk factor for a hamstring injury is a previous hamstring injury.” In fact, according to a group of medical researchers, of the 2,075 NFL hamstring injuries recorded between the 2009-10 and 2019-20 seasons, 38.4% of them were recurring. 

That’s not great news for a Green Bay roster with several players with hamstring histories. Josh Jacobs already is dealing with the problem again this year, though the team says it’s minor and he is expected back soon. But as we’ve seen, those predictions are often wrong. We don’t yet know about Stokes and Watson. 

To be sure, there are many degrees of severity with these injuries, complicating matters even further. But here are some things we do and don’t know:

— What exactly happens? Hamstrings are prone to injury at higher speeds and thus are more common for those playing receiver, DB, linebacker and running back. For years teams focused on what were deemed more serious lower extremity injuries — ligament tears, ankle damage, etc. Yet the effects of hamstring injuries can linger longer, and it’s interesting how much wasn’t known about exactly how and when the injury occurs until the past several years. For example, it was Dr. Bryan Heiderscheit’s team at UW which discovered that most of the strain on hamstrings occurs not at initial burst or acceleration, but when a player is running at roughly 60 percent or more of his top capability. More recently, as in the case of Watson, the UW group has been looking at the asymmetry between strength of each leg’s hamstring and how that imbalance can increase a player’s vulnerability.  

— A lot of these injuries occur in pre-season camps and games. This would be better news if it wasn’t for the recidivism problem, but it offers more opportunities than in the regular season to try different tactics to limit hamstring injuries. The NFL has been touting its improved pre-season injury numbers — including lower body extremities — but it’s unclear how much of that is specific to hamstrings, or whether the results are from a general reduction in pre-season activity, due to teams being cautious and the tradeoffs made as a result of adding more regular-season games.

— Conditioning matters greatly. Just this week, the players association proposed an overhauled off-season schedule that moves OTAs later, eliminating the break between them and training camps. The proposal was not aimed at the hamstring problem, but rather players believing that lengthening the time away from all activity after the end of the previous season was beneficial for their bodies. But the medical research suggests that a more concentrated and sustained conditioning regimen going into the start of the season could also be helpful for mitigating the number of hamstring injuries. As far back as 2000, the Patriots, who had had an unusually high number of hamstring problems, developed a new approach that involved more intensive conditioning for non-contact injuries and had some success in cutting down on their hamstring problems. It’s unclear based on available data how they have fared compared with other teams since then, but their physical therapy expert at the time believed that the preseason programs of teams were inadequate in conditioning players for the long haul of the regular season. And yet contractual rules that limit player training time — in part as a means preserving health — create a problematic paradox.

— Playing surface and regular-season scheduling are not the problem. Data shows no statistical difference between turf and natural grass when it comes to hamstrings, nor do more games during the week, with shorter turnaround times, seem to matter. It’s more about the ongoing conditioning.

— There remains a lot to learn. Basketball and hockey players suffer fewer hamstring injuries, and there has been speculation that it’s in part because their players are moving backwards at speed far more often than football players. Backwards running, the theory goes, helps strengthens them. A medical study of college football players found that those who did backward running as part of their conditioning showed considerably greater hamstring flexibility. Other research has shown that shorter strides are helpful, so some runners have been coached to increase the number of steps they take while running at the same speed. Players with previous hamstring problems also tend to overcompensate to try to limit recurrence, which can actually lead to more problems. More techniques have been and will be deployed, particularly as more data is collected that identifies exactly what happens when players run. 

Much of this is now the responsibility of Aaron Hill, Green Bay’s new strength and conditioning coach, who had served as the deputy with the 49ers. It’s a critically important, under-the-radar role. Success could make a big difference in how far the Packers advance this year. GPG.