How Worried Should NFL Teams Be About Eddie Lacy's Injured Hamstring?

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How Worried Should NFL Teams Be About Eddie Lacy's Injured Hamstring?
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Former Alabama standout Eddie Lacy is widely regarded as the best running back heading into April's NFL draft, but a lingering hamstring injury has put a bit of a damper on his draft week expectations.

On Feb. 18, ESPN's Adam Schefter reported Lacy strained his hamstring while training for the NFL Scouting Combine. The injury prevented Lacy from participating and now it will force him to miss Alabama's March 13 Pro Day as well (h/t ESPN).

Questions about Lacy's straight-line speed already surrounded him prior to the injury (h/t Rob Rang, The Sports Xchange/ He also carries with him a history of injury troubles (h/t Derek Harper, The Sports Xchange/ Without the ability to address either of those concerns during Pro Day workouts, teams are now even more likely to balk at calling Lacy to the podium during the first round.

Unfortunately for Lacy, hamstring injuries can be very tricky, especially for a running back. A brief detour into the anatomy and mechanics of sprinting makes it clear why that is.

The above diagram shows the three hamstring muscles as viewed from behind. The semitendinosus is colored bright red, and the semimembranosus and biceps femoris can be seen immediately to its left and right, respectively. For reference, the back of the knee can be seen at the bottom of the picture. The inner thigh is to the left, and the outer thigh is to the right. Photo from Wikimedia Commons.

The three hamstring muscles—the semimembranosus, semitendinosus and biceps femoris—are located in the back of the thigh. Their primary function is to bend the knee and also to swing the leg backward at the hip. When a running back sprints, he uses the hamstrings to "pull" the ground beneath him as he moves forward with each stride.

Hamstring injuries, called "strains," occur when one or more of the muscles are over-stretched or torn. A grade-one strain is a simple over-stretch without any tear, while grade-two and grade-three strains represent partial and complete muscle tears, respectively.

Strains usually occur while sprinting, and the sight of an athlete pulling up lame mid-run is a fairly common occurrence. Lacy's strain is no exception—Schefter's report states the injury occurred during a mock 40-yard dash.

While playing for Spain in the 2010 FIFA World Cup, Fernando Torres suffered a left hamstring strain while sprinting after a ball. His reaction is classic for the injury.

A fascinating April 2012 study by Dr. Anthony Schache and coworkers at the University of Melbourne demonstrates why hamstrings are vulnerable to injury while running (h/t Pub Med). In the study, investigators measured the force applied to the ground by seven sprinting athletes and combined it with computer models to determine the nature of the stress applied to the hamstrings at top speed.

According to Dr. Schache's data, the hamstring is stretched to maximum length toward the end of the forward-leg-swing phase of sprinting. Then, it starts to contract immediately before the foot is planted. It continues to shorten throughout the rest of the running motion until the athlete begins to stride forward once more.

In other words, the act of sprinting puts the hamstrings through rapidly repeated cycles of forceful lengthening and shortening. If they are not warmed up beforehand—and sometimes even if they are—a strain can result.

Strained hamstrings are unable to do their job as effectively, usually manifested as the need for a shorter stride length on the injured side. They are also prone to further, more serious injury. As a result, Lacy running on an injured hamstring would not only likely produce a slower 40 time, it could also do more damage to the muscle.

Streeter Lecka/Getty Images
Scouts last saw Lacy run in January during the BCS National Championship Game.

While grade-three strains sometimes require surgery to reattach the torn muscle, grade-one and grade-two strains will usually heal on their own.

There is no evidence to suggest Lacy's strain is of the grade-three variety, so patience, rest and physical therapy should be sufficient treatment. In fact, Schefter's original report states an MRI found a "small tear in some tissue around the hamstring." It is not entirely clear what that implies—perhaps a tear in the hamstring's connective tissue, called "fascia"—but the effect is essentially the same and should not complicate his recovery.

That said, any time someone wants to bend their knee, he or she must contract the hamstring muscles. As such, it is extremely difficult to fully rest them, which is one of the reasons hamstring injuries tend to linger or re-surface weeks later. The tightness Lacy still feels is likely due to continued inflammation—a part of the body's healing process.

To further complicate matters, one of the biggest risk factors for a hamstring strain is a history of prior injury. In a 2001 British Journal of Sports Medicine study, Dr. G. Verrall and colleagues determined that players with previous strains are at a 4.9 times higher risk of future strains when compared to those without such history.

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Will NFL teams take that increased risk into account on draft day? Maybe. Each team's medical staff must come to its own conclusion. Need at the running back position will also play a crucial role.

Nevertheless, proper treatment and rehabilitation should limit any long-term effects of Lacy's current injury. He also has plenty of time to get back to full strength before training camps get underway, and proper precautions, stretching and warm-ups will be his best friends.

However, for now, Lacy remains unable to address the concerns about his top-end speed. Bleacher Report's NFL draft lead writer Matt Miller weighed in on that very subject:

NFL scouts need to see Lacy run, if only to answer questions about his hamstring. It's concerning at this point that he's putting it off. We're talking about the clear-cut No. 1 running back in this class with late-first-round potential.

While an increased risk of future injury may be considered, its importance will pale in comparison to that of the shear amount of unknowns still surrounding the injury.

Rest assured, Lacy will heal, and he will probably do so before the draft. It's just a matter of time. Yet with the draft now only about six weeks away, nothing can be taken for granted.

Dave Siebert is a medical featured columnist for Bleacher Report who will graduate from medical school June 15. He plans to specialize in both Family Medicine and Primary Care (non-operative) Sports Medicine. Injury and anatomical information discussed above is based on his own knowledge except when otherwise cited, and quotes were obtained firsthand unless alternatively noted.


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