By Gabriel Mvumvure and Kim Goss
If there’s one bold statement that we can make about hamstrings pulls, it’s “whatever most athletes are doing to prevent them, it’s not working!” It seems no matter how much an athlete stretches or what special strength training exercises they perform, hamstring injuries are still some of the most common injuries among those who need to move fast.
Let’s explore why so many athletes get hamstring injuries and what can be done to prevent it.
Is Sprinting Dangerous?
There is a widespread belief that sprinting is an unnatural activity that causes the body to become “quad dominant,” increasing the stress on the hamstrings. It follows that to stay healthy, sprinters must get their sprinting muscles in balance by performing special knee flexion and hip extension exercises. We contend that sprinting itself is not the cause of hamstring pulls, but rather, poor sprinting technique is to blame.
One issue we’ve seen with many freshman sprinters is they have compromised their technique to achieve lower times. “Run faster, turn left!” as the saying goes. Not only are the technique faults from such training a challenge to correct, but they can cause chronic injuries we have to address when the athletes enter our program.One issue we’ve seen with many freshman sprinters is they have compromised their technique to achieve lower times. Click To Tweet
The most common technique fault in sprinting is overstriding, such that the contact foot lands too far in front of the athlete’s center of mass (see video 1 below). One study found that “the runners with hamstring injuries demonstrated 4.9° greater overstride angles compared with the healthy control runners.” The researchers said one cause of these injuries could be excessive tension. “When the foot lands on the ground with overstride mechanics, the hamstring musculature may be stretched eccentrically, which may facilitate in increasing the tension on the hamstring muscle bundles.”
Video 1. Overstriding increases the stress on the hamstrings, making the athlete more susceptible to injury.
Optimal sprinting technique involves placing the contact foot in a position where it can apply maximum force into the ground. The more force applied into the ground, the greater the stride length. The greater the stride length, the more ground covered with each step and the faster the athlete moves. For example, in 1991, Carl Lewis took 43 steps when he established his 100m world record of 9.86 seconds. In 2009, Usain Bolt needed just 40.92 steps to cover that distance and finished in 9.58 seconds!
If the contact foot lands in front of the hips, less vertical force is applied to the ground and stride length is decreased. That’s not good, but what’s worse is that the athlete’s hamstrings must work harder by pulling the foot across the ground, increasing the stress on these muscles. So how can overstriding be corrected? Let’s start with an off-track sprinting drill.
In video 2 below, one of our sprinters demonstrates a drill to correct overstriding that can be performed in a gym. The setup involves attaching an elastic band to the top of a power rack and hooking the other end around the ankle of the working leg. From this starting position, the athlete performs a high step march in place, focusing on driving that foot to their center of mass. We especially like that the drill has a built-in feedback quality, because the athlete will lose their balance if they step in front of their center of mass.
Video 2. A gym-based drill using bands to correct overstriding.
Next, let’s look at a track drill to correct overstriding. In video 3 below, one of our sprinters demonstrates a wicket run that promotes optimal front-side mechanics with a high heel recovery. If an athlete overstrides, they will gallop over the wickets. Galloping results in a slower time, as the force production is less vertical. In addition, overstriding makes it more likely they will hit the wickets, causing them to lose their momentum.
Video 3. A wicket drill to correct overstriding.
Anatomy of a Hamstring Pull
Extensive research has revealed how most hamstring injuries occur and what area(s) of the hamstrings are most likely to be injured. But before going further, let’s address the belief that increasing hamstring flexibility is the key to preventing hamstring pulls.
A study on Australian rules footballers involved 67 athletes who were tested in the standing toe-touch before the season. During the season, eight players suffered a hamstring strain, but researchers found “no relationship between pre-season results of toe-touch test measurements and hamstring strains sustained during the football season.” Another study involved 34 athletes from rugby, hurling, and Gaelic football. Sixteen of the subjects had no history of hamstring injury during the preceding year. The researchers found that “differences in hamstring flexibility are not evident between injured and noninjured groups.”
Many other studies suggest that hamstring flexibility, along with static stretching intervention programs, have no influence on preventing hamstring injuries. However, we’re not saying that static stretching has no value—just that it appears to have little influence in preventing hamstring pulls. But let’s move on.
Most sprinting injuries occur during the late swing phase, immediately before the foot strikes the ground. During this phase, the long head of the biceps femoris completes the longest stretch of all the hamstring muscles; it is also the area of the hamstrings most likely to become injured. If there is excessive tension in the biceps femoris during sprinting, an injury can occur. This is not a new concept.The issue of incomplete muscle relaxation is a concept that must be considered when selecting exercises to strengthen the hamstrings. Click To Tweet
“Soviet era research of muscle relaxation dates back to at least the 1930s,” says weightlifting sports scientist Bud Charniga. “The critical role of muscle relaxation; especially the speed of muscle relaxation; has been a consistent theme in efficacy of sport technique in East European literature ever since those days.” Charniga adds that Soviet sports scientist L.P. Matveyev referred to the incomplete relaxation of a muscle after contraction as “coordination enslavement.” Whatever it’s called, the issue of incomplete relaxation is a concept that must be considered when selecting exercises to strengthen the hamstrings.
The Case Against the Nordic Curl
A typical workout to prevent hamstring pulls might include one exercise for the knee flexion function of the hamstrings and one for the hip extension function of the hamstrings. For complete development, the exercises could be varied every few weeks. For example, to strengthen hip extension, one exercise could focus on the top range of the resistance curve (reverse hyper), another the mid-range (45-degree back extension), and another the bottom range (barbell good morning).
Although the number of sets and reps and other loading parameters can be debated, this approach seems to make sense. After all, as shown by the accompanying photo, many professional bodybuilders have proven that performing a variety of hamstring exercises with various resistance curves can add tremendous size to the hamstrings. However, when training an athlete, you must consider more than just resistance curves and workout protocols that make muscles pop out when you flex.
In addition to addressing movement patterns, limb speed must be considered when selecting the best resistance training exercises for the hamstrings. That is, how quickly muscles contract and relax and how connective tissues stretch and recoil. According to Charniga, exercises such as the Nordic curl are characterized by prolonged muscle tension that is “inconsistent with what actually occurs in the late swing phase of running and sprinting.”
Another factor to consider, which Charniga says is often ignored in the literature about hamstring injuries, is that the ability of the hamstrings to relax is influenced by other muscles, “especially from muscles such as the bi-articular gastrocnemius which cross the knee from below.”
The anatomy of the gastrocnemius is such that it can assist the hamstrings with knee flexion. You can easily experience the influence of the calves on knee flexion strength by performing leg curls. Point your toes (plantarflex) as you perform the exercise, work up to a max weight set of 10 reps. Now pull your toes toward you (dorsiflex) and use that same max weight—you will find this set to be considerably easier, such that you could probably perform another set with 5-10% more weight.
Putting this together, it makes sense that tension in the calves can affect the ability of the long head of the biceps femoris to stretch. “These muscles cross the knee from below,” says Charniga. “Any extension of the knee joint up to 180° can only occur if these muscles relax and lengthen, i.e., knee extension is affected from an ‘overlap’ or a ‘choke’ point of muscle attachments from above and below.”If there is an injury-prevention effect of the Nordic curl, it doesn’t appear in the numbers. Click To Tweet
The Nordic curl produces prolonged tension of the hamstrings with the calves held in a fixed position. As the hamstrings lengthen, the calves contract isometrically—this is not how these muscles function in sprinting. “Teaching an athlete to develop eccentric strength of the hamstring group to prevent injury with grinding, slow eccentric strength exercises is probably counterproductive; because sprinting actually requires a rapid onset of a late ‘braking phase’ as the leg swings forward and extends for ground contact, i.e., low tension followed by tension from stretching,” says Charniga.
Charniga says the Nordic curl is a popular exercise in the NFL, but he makes a strong case with injury data that extensive use of the exercise may be causing hamstring injuries. For example, the 2018 NFL season began on September 2, 2018. Despite a long off-season of strength and conditioning and controlled practice environments, 74 athletes were placed on the injured list with hamstring injuries. Before the start of the 2019 season, 43 athletes were sidelined with hamstring injuries! Further, between the 2018 and 2019 seasons, at least 25 athletes on average could not play due to hamstring injuries. If there is an injury-prevention effect of the Nordic curl, it doesn’t appear in the numbers.
Another issue is that the knee joint is fixed with the Nordic curl. “Any time you fix a joint, you increase the shear stress,” says Paul Gagné, a Canadian strength coach and posturologist. “For example, bodybuilders who focus too long on exercises that fix the elbow, such as preacher curls, often develop tendinitis in the elbow.” Gagné also has found that the Nordic curl places adverse stress on the popliteus muscle, which is involved in knee flexion and knee stability, and the meniscus. “My sports medicine colleagues have worked with numerous athletes who developed knee pain in these two areas from performing the Nordic curl for long periods,” says Gagné.As for sport specificity, Gagné says the Nordic curl’s value must be questioned because the feet are not in contact with the ground & the hamstrings work w/muscles of the foot to produce movement. Click To Tweet
As for sport specificity, Gagné says the value of the Nordic curl must be questioned because the feet are not in contact with the ground, and the hamstrings work with muscles of the foot to produce movement. Dr. Michel Joubert, a podiatrist and posturologist who has treated many of Gagné’s athletes, said it’s rare for him to find someone who has a hamstring injury who does not also have problems with the arches of the feet.
Although a complete hamstring strength program is beyond the scope of this article, we would like to leave you with a few alternative gym exercises to the Nordic curl.
The Elastic Strength Approach to Hamstring Training
Muscles must contract and relax quickly in sprinting, but athletic performance is not just about muscles. To produce the highest levels of speed and power, the tendons and other connective tissues must stretch and recoil quickly.
Elastic strength training methods look at these connective tissues as biological springs that absorb, store, and release energy. The more energy these tissues release, the faster and more powerful the movement. Charniga notes that the ground support time for an elite sprinter is so short that it “is not possible from mere muscular contraction.” And based on the data we’ve seen, Florence Griffith Joyner recorded the shortest ground support time ever for a woman, and Usain Bolt had the shortest time for a man.
One of the best sports for developing elastic strength is weightlifting, and the large range of motion these lifts require makes them especially effective for injury prevention. Most weightlifting coaches will never have to deal with a hamstring, ACL, or ankle injury because they are so rare. Let’s look at a real-world example.One of the best sports for developing elastic strength is weightlifting, and the large range of motion these lifts require makes them especially effective for injury prevention. Click To Tweet
From 2007 to 2012, 480 women competed in the European Weightlifting Championships. This event lasts about a week, and competitors do several workouts before they compete. These athletes performed perhaps as many as a quarter of a million total reps in snatches, clean and jerks, and squats during this period. Further, many of these lifts were performed with maximal weights. With this sample size, plus the women’s “fragile knee anatomy” and fluctuating hormones that are often blamed for their high injury rate (especially with the ACL), you would expect a horrific injury report. Not quite.
The number of hip, knee, hamstring, and ankle injuries reported during this period that required medical attention was zero. Again, zero. Compare this to most American sports, where about 70% of all knee, hamstring, and ankle injuries are non-contact and occur without load. As many motivational speakers are fond of saying, “Success leaves clues!”
In addition to weightlifting, there are many effective exercises that improve elastic strength. We want to leave you with a few we have our athletes perform.
The first exercise uses a Swiss ball and focuses on high-speed knee flexion, and the second uses bands and focuses on high-speed hip extension. Both exercises are performed at maximum speed and for a time limit to maintain quality, such as 30 seconds. (Note: we take no credit for creating these two exercises.) The exercises are demonstrated in videos 4 and 5 below, but first let’s go over a few notes.
In contrast to a prone leg curl—where the limbs move relatively slow—with this first exercise, the athlete moves their limbs as quickly as possible, kicking the ball with their heels as they do so.
Video 4. A high-speed knee flexion exercise.
For the second exercise, the athlete lifts their hips off the floor, maintains a neutral spine, and stabilizes their upper body with their arms as they perform a flutter kick as fast as humanly possible. We also have our athletes perform it with various foot/leg positions to emphasize different areas of the hamstrings.
Video 5. A high-speed hip extension exercise.
The last exercise is a single-leg assisted squat jump using a dumbbell. Kenneth Hunt, the jumps/combined events coach at Brown, deserves partial credit for creating this one. It could be considered an elastic strength exercise involving rapid contraction and relaxation of the thigh and calf muscles.
- Set up a power rack with a barbell resting inside of the bar catches, such that the supports will stop the bar if you pull back too hard. The bar should be raised to about chest height.
- Grasp a dumbbell in one hand and hold the bar with the other hand.
- Dorsiflex the foot of the working leg and lift the thigh until it is about parallel to the floor.
- Bend down to about a parallel position, then straighten your leg and hop a few inches off the floor—do not allow the opposite foot to touch the floor.
- Immediately squat down, focusing on reversing directions quickly at the bottom.
Perform all the reps in a set for one leg, then repeat with the opposite leg. To increase resistance, hold a heavier dumbbell.
Video 6. A single-leg assisted squat jump where resistance can be increased by holding heavier dumbbells.
These are just three of the many elastic strength exercises we use with our sprinters. One benefit we noticed from such training is a remarkable increase in vertical jumping ability in short periods, even for those who already have good verticals.
A complete hamstring prevention program involves many components that are beyond the scope of this article. For example, relatively weak glutes or collapsed foot arches (valgus) can increase the stress on the hamstrings. It’s also possible that athletes who have suffered serious hamstring tears may need medical intervention. For example, researchers have found that if an athlete has a previous hamstring injury, scar tissue can develop and linger that can “alter contraction mechanics” during running, increasing the risk of reinjury. This scar tissue may need to be addressed, such as with Active Release Techniques treatment®.The bottom line is that sprinters, sprint coaches, and strength coaches must carefully consider running mechanics and the true value of strength training exercises for the hamstrings. Click To Tweet
The bottom line is that sprinters, sprint coaches, and strength coaches must carefully consider running mechanics and the true value of strength training exercises for the hamstrings. Give the ideas presented in this article a try to keep your athletes moving fast and injury-free!
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Bennell, K., Tully, E., and Harvey, N. “Does the toe-touch test predict hamstring injury in Australian Rules footballers?” Australian Journal of Physiotherapy. 1999;45(2):103-109.
Charniga, Bud. “How Is It Possible Weightlifters are Stronger,” May 11, 2020, sportivnypress.com.
Charniga, Bud. “A Stability/Instability Convexity,” April 23, 2021, www.sportivnypress.com.
Charniga, Bud. “Hamstring Injury: Prophylaxis Fallacies in Sport,” June 29, 2021, www.sportivnypress.com.
Charniga, Bud. “Hamstring Injury in Sport,” July 21, 2021, www.sportivnypress.com.
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