Hamstring strains are one of the most common soft tissue injuries affecting that affect soccer athletes. While injuries are always multifactorial, hamstring injury can be simplified to the muscle not having adequate capacity to meet the demands of sport. Soccer involves nearly constant movement, including running, sprinting, acceleration followed by sudden deceleration, changing directions, jumping, and diving. The hamstrings play an essential role in every movement that is essential to the sport. Sprinting places the highest amount of force on the hamstring muscles. In fact, the hamstrings experience the equivalent force of 8-9x bodyweight during sprinting. This is due to their function in doing two things: A) decelerating the tibia during the swing phase of sprinting and B) contributing to applying force into the ground to move forward during the stance phase. Let’s break those two concepts down.
Swing phase
As mentioned, the swing phase is a time of really high stress for the hamstring. During top-speed sprinting, the body has progressed from a horizontally directed angle to an upright posture. At this point, during each swing phase, the knees and hips move through greater total ranges of motion, and as a result, the hamstring is aggressively loaded in a lengthened position as it decelerates the tibia to prepare for the next step. This is when there is the highest potential to experience a muscle strain.
Stance phase
This phase of sprinting is underappreciated, in my opinion, in its contribution to hamstring strains. At the initial point of contact with the ground, the hamstring transitions from an eccentric to a concentric contraction. This means that the muscle is moving from a lengthened to a shortened position. Concentric force from the hamstring helps the calves and glutes produce force into the ground to project the body forward horizontally. Considering ideal top-speed sprint mechanics, the foot should strike under the pelvis. In reality, many athletes haven’t developed this level of skill, especially younger athletes. This means that their foot strike is likely in front of the pelvis. This is important because it places higher stress on the hamstrings due to operating with a longer lever arm. This increases the susceptibility to a strain in the stance phase.
Acceleration vs. top speed
Sprint mechanics during acceleration differ from top speed. When an athlete is accelerating, the torso is pitched forward, the chest is directed towards the ground, hip height is lower to the ground, the hip joints move into deep ranges of flexion, and the knees function in a piston-like manner. All of this is done to produce as much force as possible into the ground behind the body to project the athlete forward. Efficient acceleration is what gets the athlete moving fast. Once the athlete is at top speed, the primary goal of the body is to maintain the speed that was built during acceleration. At top speed, the torso is in an upright posture, the chest directs forward, the pelvis is level, hip flexion decreases, but total motion at the hip increases, and the knees cycle through an oval-like pattern.
What things to look out for when returning to soccer
Specific to the hamstring, it’s very important to know how strong you are. This isn’t done by someone saying, “Hold, don’t let me move you”, as they pull on your leg and proceed to say, “They feel equal to me”. That is not good enough. True assessment of strength needs to be objective. This means you have a number that represents how much force you can produce by contracting the muscle. These numbers are compared between legs to understand how much asymmetry exists. This number should be at least < 10%, ideally < 5%. If available, force plate testing can be another helpful piece of information to understand how the athlete loads each leg during different contraction types while jumping. Lastly, and in my opinion most importantly, the athlete needs to have completed a progressive training program that required them to do everything they will need to do on the pitch, including sprinting. So often, sprinting isn’t a part of the program for various reasons. Exposure to a sprinting progression is an absolute must to confidently clear an athlete after a hamstring injury.
Why all of that matters
Now that we have touched on the key points to know about how the hamstring functions in sports, hopefully there is an appreciation for how much goes into something as simple as running. In soccer, running is a large majority of the game. While a lot of time gets spent on skills training, and rightfully so, performance training needs the same amount of focus to stay healthy and reduce injuries. Despite doing everything possible to prevent injuries, we will never be able to completely avoid them. This is why when injuries do occur, choosing a physical therapist that specializes in sports rehabilitation and understands return to sport decision making, is critical. Taking a shortcut in this area can lead to a rehabilitation process that underloads tissues, increasing the risk for re-injury. This means more time spent on healthcare costs, more time away from the game, and more long-term effects. At Stamina, all of these things are not only well understood, but they matter. We understand how it feels to be on the sideline, wishing for better health. That’s why we’re here. If this speaks to someone you know, we would love to help. Call or text us at 404-548-8263, or complete a contact form, and we will reach out to you.
Best,
Board Certified Orthopedic Clinical Specialist
Certified Strength and Conditioning
SpecialistOwner/Founder - Stamina Performance Physical Therapy
