Hamstring flexibility for rowers seems to always rank high in concerns for both coaches and rowers. “My hamstrings are tight” is offered as an explanation for everything from low back pain, poor stroke technique, restricted reach on the recovery, and more. However, perhaps we’ve been chasing the wrong culprit with our seemingly endless hamstring stretches. When writing my low back pain and rib stress injury research review article, I kept coming across references to “Koutedakis, 1997,” in regard to the muscular imbalance of quadriceps and hamstrings in rowers and resulting low back pain.
“Knee Flexion to Extension Peak Torque Ratios and Low-Back Injuries in Highly Active Individuals” was an intriguing study as described in other research, despite the bland name, as the authors reportedly did a 6-8-month study of female rowers with a history of low back pain, assigned a hamstring strengthening intervention, and found a decrease in days missed from practice for low back pain. I got the article through interlibrary loan, dug in, and it turned out to be even more interesting than I hoped.
The authors mention in their introduction that the structure of the hamstring muscles is one reason hamstring flexibility for rowers may be overrated for low back pain. The hamstrings and quadriceps are both two-joint muscles, and they are antagonists of each other with regard to knee flexion and extension. “Two-joint muscle” means they cross two joints–the knee and the pelvis, in this case. “Antagonists” means they oppose each other. The hamstrings are the knee flexors and hip extensors, and the quadriceps are the knee extensors and hip flexors. However, they both act simultaneously during the rowing stroke, as the quadriceps extend the knee during the drive while the hamstrings are extending the hip. This isn’t a flexibility issue, because both muscles are actively contracting, not lengthening. Also, the hamstrings are characterized by what the authors describe as “taut, cord-like tendons,” making them relatively inelastic. Stretch as much as you want–it’s pretty hard to make meaningful change to a tendon.
The researchers studied 48 male and 41 female competitive rowers, 30 of whom rowed for the British National Team, as well as 20 professional male ballet dancers. They included ballet dancers as another quadriceps-dominant sport with high frequency of low back pain. All participants had experienced a low back injury in the previous 12 months, but were not currently experiencing symptoms. The researchers also recorded how many days of training they had missed in the last year due to low back pain.
The researchers then did a sit-and-reach test with all participants, as well as an isokinetic dynamometer test to assess knee flexion (hamstrings) and knee extension (quadriceps) strength. The sit-and-reach test (below, left) is a standard test for flexibility of the spine and posterior muscles, in which the subject sits flat on the ground, legs straight out in front of them, feet against a box, and then reaches forward as far as they can without bending their legs. The isokinetic dynamometer (below, right) is basically a seated leg extension and leg curl machine, but instead of the load arm moving, it’s a fixed arm that records the amount of force the subject applies to a given point on the machine. The machine is fitted to each subject’s measurements and these are both standard tests in fitness research.
Left, sit-and-reach test (source PerformBetter.co.uk)
Right, isokinetic dynamometer (source aspetar.com)
Data and Results
The researchers then ran statistical analysis with this information alone. They found that the dancers were more flexible than the rowers, but that there was no significant correlation between sit-and-reach results and number of days missed due to low back pain in rowers or dancers. They used the missed number of training sessions to evaluate both frequency of injury, if the athlete missed 1-2 days at a time but perhaps 6-7 times per year, as well as severity, if the athlete missed more than 5 days just once during the year.
They did find a significant correlation in all three groups in ratio of knee-flexion-to-extension and number of days missed due to low back pain. A low ratio of knee-flexion-to-extension means relatively weaker hamstrings compared to quadriceps. Across all groups, the lower the ratio, the greater the degree of injury as measured by number of days missed from training. There was a significant drop in missed training sessions when the hamstrings were at least 45% as strong as the quadriceps.
Strength Training Intervention
Then, things get more interesting. The researchers took a sub-group of 22 female rowers and provided a strength training intervention that focused on hamstring strength for 6-8 months during their rowing training. The participants trained up to three times a week for 90 minutes per session. I was hoping for more details on exactly what they did, but the researchers only said that they did high reps with <70%1RM load for the first two weeks, and lower reps with >70%1RM load for the next 6-7 months, training 3-4 different muscle groups with mostly free weight exercises, always including both left and right hamstrings. In other words, a fairly typical strength training program aside from the emphasis on training the hamstrings directly. I’ve emailed Dr. Koutedakis to ask for the specific exercises or training protocol they used, and will update this if I receive a response.
After 6-8 months, the researchers re-tested the rowers on the original measures. The subjects improved their knee flexion results, but not their knee extension results or their sit-and-reach results. The researchers also found fewer days missed due to low back pain in the 6-8 months of the strength training intervention compared to the previous 12 months of training. The rowers improved their hamstring strength, but not their quadriceps strength or their posterior flexibility, and decreased the number of practices missed due to low back injury.
“The rowers improved their hamstring strength, but not their quadriceps strength or their posterior flexibility, and decreased the number of practices missed due to low back injury.”
What This Means for You
The researchers noted that the lack of correlation between sit-and-reach results and low back pain runs counter to the current research that suggests that poor lumbar and hamstring flexibility is related to low back pain, and that good flexibility indicates good musculoskeletal function. The authors suggest that different statistical procedures may have produced this result. There is a problem in exercise science research of researchers manipulating research to report statistically significant findings, rather than finding no result (the null hypothesis), as in the current study. You can read more about this by Greg Nuckols here. However, Koutedakis et al. also propose that the difference could be due to their participants not experiencing symptoms at the time of data collection. It is possible that pain limits flexibility, and that other studies researching subjects currently experiencing pain would get different results.
The researchers also found that the mean flexion-to-extension ratio of 50% in rowers is lower than the 55-80% that researchers suggest is optimal for trained and untrained populations. They suggest that this is due to the high emphasis on the quadriceps in rowing, and the absence of dedicated hamstring strengthening exercises in most traditional strength training programs. Their results support this conclusion, as improving the flexion-to-extension ratio in the 22 female rowers from 51% to 61% during the strength training intervention resulted in a decrease in days missed from training.
Other research on rowers also indicates that strength and lumbopelvic coordination may be more important factors than hamstring flexibility alone in reducing low back pain. Stutchfield and Coleman (2006) studied 26 male university rowers using the straight leg raise test of hamstring flexibility and found no connection to self-reported low back pain incidence. They did, however, find significant difference between left and right hamstring flexibility in the rowers, and found greater difference in left-right hamstring flexibility for rowers with low back pain compared to those without low back pain. Interestingly, the researchers did not find that the flexibility imbalance was connected to rowing port or starboard side.
“The lack of association between hamstring flexibility and low back pain suggests that techniques to increase hamstring flexibility for rowers may not prevent or be useful in low back pain rehabilitation.”
The Bottom Line
Overall, I would say yes, hamstring flexibility for rowers is overrated. This is partially because of how popular hamstring flexibility and stretching is, as well as how little it may actually do for us compared to other alternatives. Does this mean hamstring flexibility for rowers is never a concern, and should be entirely ignored? Of course not. A straight leg raise test, as Blake Gourley demonstrates in the picture above, can still provide some helpful information about an athlete. Dynamic hamstring stretches as part of a rowing warmup can help prepare the body to row. Finally, if static hamstring stretching feels good, then that is a benefit in and of itself.
However, if you’ve been in the “tight hamstrings” camp despite abundant stretching, consider incorporating some regular, specific hamstring strengthening into your strength training for rowing regimen. Exercises like Romanian deadlifts train the hip extension element of the hamstrings, but your program may not include specific knee flexion exercises for the hamstrings. Stability ball leg curls and glute-ham raises are my top two options, with machine-based bilateral and unilateral seated, lying, or standing leg curls, if that is all that is available, also possibly worth including in rowing strength training programs. Begin with 2-3 exercises per week, included in assistance work after your main work compound movements, for 3-5 sets of 8-15 reps per set, and stick with it for at least 6-12 weeks to see if it makes a difference in any back pain.