We sprint a lot. Sports culture is filled with it — track and field events, baseball, soccer, tennis, football, basketball, lacrosse, rugby — I’ve even sprinted across fairways in golf to see shots sweep around corners (intentionally, of course!) But it’s pretty much impossible to sprint with a hamstring injury. Pulls, tears, tweaks, and strains are common topics of discussion for athletes who sprint a lot, and even just a little. Fortunately, strong research is being published on one of my favourite exercises, the Nordic Hamstring Exercise.
What is a Nordic Hamstring Exercise?
The Nordic Hamstring Exercise (NHE), or Nordic Curl, is an eccentric exercise designed to strengthen the hamstrings and prevent injury during sprinting. Muscles generally operate in two fundamental directions: they can shorten, like your bicep when flexing your elbow, and they can lengthen, such as the bicep when extending your elbow. When our muscles work to produce an action, they must contract, and this usually involves shortening of the muscle — a process called “concentric contraction” — think of making your bicep bigger. However, it is also possible that a muscle tries to contract, but is overcome by competing forces and continues to lengthen — a process called “eccentric contraction”.
Why is Training with Eccentric Exercise Necessary?
Our hamstrings help our bodies move into hip extension and knee flexion. During walking and jogging, since we are not at the extremes of hip or knee motion, our hamstrings are relatively untaxed — there are plenty of other muscles to assist movement. During sprinting however, the hamstrings are required to work much harder to keep us moving quickly, and in control of our body. Research into the demands of the hamstrings while sprinting indicates that as we stretch our forward leg ahead of our body, our hamstrings, in anticipation of our foot striking the ground, must eccentrically contract to stop our knee from extending and transition to producing a powerful stride. This is the moment in time during a sprint where our hamstrings have the greatest demands placed on them, and is also the moment where injury most frequently occurs. Without this eccentric contraction occurring in the hamstrings, we would be unable to stop our knee from extending, and would fail to create a powerful stride.
Reasonable? This explanation makes good logical sense to me, but it is also supported by previous research conducted on hamstring injury. This research shows that inadequate eccentric hamstring strength is linked to an increased risk of hamstring injury during high-speed running. So all the more important to address this potential source of injury.
How do I perform a Nordic Hamstring Exercise?
Credit illustration: Ben Wiseman.
The NHE is a two-person exercise — one exerciser and one assistant. The assisting person maintains consistent downward pressure on the exerciser’s calves or heels, maintaining contact between the exerciser’s feet and the ground at all times. To perform an NHE, do the following:
1> The exerciser begins in a kneeling position.
2> With the assistant applying consistent pressure, the exerciser SLOWLY lowers their body towards the ground. The slower the better, as this maximizes the eccentric contraction time.
3> Catch your body on the ground with your arms (like a push-up), and push yourself back into a kneeling position. Try not to use your hamstrings to get back up — save those for the eccentric (lowering) phase!
4> Repeat.
Does the NHE impact injury rates?
A recently published study in the American Journal of Sports Medicine (2015) followed 40 soccer teams (579 players), of whom 50% were given an NHE protocol to follow in addition to normal training, and 50% continued with normal training alone. Before beginning the study, the rate of hamstring injury was essentially the same for both groups. Injury rates were recorded throughout the intervention period (13-weeks), as well as throughout the subsequent year (weeks 13-52).
During the 13-week intervention period, where players in the NHE group completed 27 NHE sessions over 13 weeks (2 sessions/week), no significant difference in injury rate was seen between groups (5 injuries NHE group; 7 injuries typical training group). However, in the subsequent 40 weeks post-intervention (weeks 13-52), a significant decrease in the incidence (number) and risk of injury was seen for the NHE group as compared to the typical training group (6 injuries NHE group; 18 injuries typical group).
These findings are supported by previous studies investigating similar eccentric training protocols, and data in support of eccentric training to prevent hamstring injury continues to build.
When and How Often should I do this?
Most recommendations suggest performing the NHE after a thorough warm-up period, ideally during your post-activity cool-down — so if you’re actively training for sport, or participating in exercises at a gym, I’d recommend at the end of this time is ideal.
Regarding how often you could be doing this, it’s important to understand that eccentric exercise generally creates a little more tissue damage (locally) than you might be used to from gym workouts, sporadic increases in activity, etc. What this means is you have to respect your rest too! My general advice, and something that the study discussed above used as well, is to do these exercises twice per week. This allows enough time for your hamstrings to recover, adapt, and grow stronger before the next round of NHE.
The study above used two general sections of training with the teams involved — the first 5 weeks were “training” sessions conducted during the pre-season, and the following 8 weeks were in-season “maintenance” sessions. Note the progression in repetitions in the table above, adapted from the study.
Considerations
- Eccentric exercises can create soreness! Delayed-onset muscle soreness (DOMS), frequently experienced following gym workouts, is a common side effect of eccentric training. So be forewarned, while the NHE is excellent for hamstring injury prevention long-term, there may be some soreness associated with getting to this level.
- Twice weekly, but the repetitions change as you get stronger. Note the progressive increase, and subsequent plateau, of repetitions noted above. We’re looking to build long-term prevention, so an incremental increase over time is important. Don’t try for too much too fast!
- Remember this is a two-person exercise. While there are methods available for turning this into a single-person exercise (heavy objects or equipment that is immovable), extreme care and safety precautions must be followed. I recommend using a friend, or asking a local trainer (if you’re at a gym) for assistance rather than turning this into a one-person exercise.
- What this exercise does not do, according to the study cited, is decrease injury severity. So while prevention gets better and overall injury rate declines, the severity of an injury that does occur appears not to be changed whether you use the NHE or not.
As always, for more information, if you have questions, or if you’d like to discuss this information in person, please feel free to leave a comment below, send me an email at drjimgilliard@gmail.com, or call and book an appointment at Endorphins Health and Wellness Centre in Burlington at 905-634-6000.
References
- Chumanov ES, Heiderscheit BC, Thelen DG. Hamstring musculotendon dynamics during stance and swing phases of high speed running. Med Sci Sport Exerc. 2011;43(3):525–32.
- Croisier J-L, Ganteaume S, Binet J, Genty M, Ferret J-M. Strength imbalances and prevention of hamstring injury in professional soccer players: a prospective study. Am J Sports Med. 2008;36(8):1469–75.
- Pas H, Reurink G, Tol JL, Weir A, Winters M, Moen MH. Efficacy of rehabilitation (lengthening) exercises, platelet-rich plasma injections, and other conservative interventions in acute hamstring injuries: an updated systematic review and meta-analysis. Br J Sports Med [In press]. 2015:1–10.
- Petersen J, Thorborg K, Nielsen MB, Budtz-Jorgensen E, Holmich P. Preventive Effect of Eccentric Training on Acute Hamstring Injuries in Men’s Soccer: A Cluster-Randomized Controlled Trial. Am J Sports Med. 2011;39(11):2296–303.
- Small K, McNaughton L, Greig M, & Lovell R. Effect of Timing of Eccentric Hamstring Strengthening Exercises During Soccer Training: Implications for Muscle Fatigability. J Strength Cond Res. 2009; 23(4): 1077-83.
- van der Horst N, Smits D-W, Petersen J, Goedhart E, Backx F. The Preventive Effect of the Nordic Hamstring Exercise on Hamstring Injuries in Amateur Soccer Players: A Randomized Controlled Trial. Am J Sports Med. 2015;43(6):1316–23.