Dynasty Football Factory

Injury Update Hamstrings Strains: Corey Davis

Why is a hamstring tear such a rough injury to recover from? Why do so many athletes have a recurrence of the injury? It seems these buggers linger for entire seasons killing a players ability and production. Today we examine Corey Davis and his injury. He had a classic cause and the effect on his season was pretty predictable. Let’s take a look at what the scientific literature has to say.

The most common mechanism of injury for a hamstring is during sprinting. The interesting thing is the injury often occurs when that leg isn’t even on the ground. Most hamstring strains/tears occur during what is called late swing phase of running,  or the phase of running right before the lead leg hits the ground. This is because the hamstrings have to slow down the extension of the knee and flexion of the hip (eccentric muscle contraction) before contacting the ground and propelling the athlete forward using knee flexion and hip extension. Interestingly enough, studies have shown that the hamstrings have the greatest electrical activity (EMG or electromyography) during the terminal swing phase of running, so it makes sense that this is where most hamstring injuries occur. A pictorial explanation is below:

The leg we are referring to in the picture is the dark leg. The images on the left depict a hamstring working concentrically (knee flexion and hip extension) and the images on the far right show an athlete transitioning to eccentrically contracting (slowing down knee extension and hip flexion), where most hamstring injuries and muscular activity occur.

Elliot et al. (2011) did a 10-year review of string injuries and here were the results: (A-E = athletic exposures and IR = injury rate… not injured reserve)

“Over the 10-year study period, 1716 hamstring strains were reported for an injury rate (IR) of 0.77 per 1000 A-E. More than half (51.3%) of hamstring strains occurred during the 7-week preseason. The preseason practice IR was significantly elevated compared with the regular-season practice IR (0.82/1000 A-E and 0.18/1000 A-E, respectively). The most commonly injured positions were the defensive secondary, accounting for 23.1% of the injuries; the wide receivers, accounting for 20.8%; and special teams, constituting 13.0% of the injuries in the study.”

Let’s check the boxes for Corey Davis:

Preseason: ✅

Hamstring injuries occur more frequently pre-combine and preseason because athletes are transitioning from training for strength and mass building to training for speed. This means more sprint training than their bodies may be accustomed to, too quickly, with more mass. Sometimes we sacrifice tissue health for performance in the sports world when millions of dollars are on the line. Can’t blame anybody there. Get it while you can.

WR position: ✅

It’s no secret that WR’s need to be able to reach their top end speed quickly. Scouts are always looking for that guy to take the top off of the defense making 40 times a huge factor for some teams (insert John Ross). Corey Davis was never lauded as a guy that would take the top off of a defense, but can you imagine the hype if he would have timed in the 4.4’s? Ultimately he was still drafted very high, but he plays a position that demands playing at high speeds, making him more susceptible to recurrence of the injury.

Another interesting piece to the Corey Davis puzzle is that he had an ankle injury that limited how much participation in offseason workouts he was able to do. This likely played a HUGE role in the development of a hamstring injury. Ankle injury = less sprint training and exposing the hamstrings to forces similar to sprinting and sport. That equates to having to speed up and condense the preparation for the season faster than is ideal and leaves an athlete susceptible to injury.

Bottom line: Studies from Heiser et al. (1984), Foreman et al. (2006), Gabbe al. (2006), and Worrell et al. (1994) have shown that the recurrence rate for hamstring injuries can be as high as 32%, The best predictor of a future hamstring injury is a past hamstring injury. Most re-injury occurs within the first two weeks after return to sport (Malliaropoulos, 2011). I’m not giving up in CD, but don’t be surprised if he has some future hamstring issues.

For more questions about the rehabilitation of this injury and more, you can contact me directly on @DPT_fjeldy. Thanks for reading!

efjeldheim

Eric is a Doctor of Physical Therapy specializing in the rehabilitation of sports medicine and orthopedic related injuries/surgeries. He has a passion for all things sports related. For more information about Eric, please visit any of his listed social media accounts or websites.

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