I came across a small research project I was working on a number of months ago and wanted to further tackle the topic. I came to the conclusion that I have not been paying as much attention to hamstrings strength for patient athletes and patients who participate in sports recreationally. The hamstrings are quite a dynamic muscle, having to control movements of the hip while simultaneously regulating the knee. You can also consider the types of muscle contractions that the hamstrings must complete; isotonic, isometric, and isokinetic. And if you want to look deeper into the issue, by creating stability of the hip it also will effect the stability up the chain to the pelvis and lower back.
In order to do this the hamstrings must fight and create harmony between itself and the strength of the hip flexors and the overly strong quadriceps muscles. If you are an individual who routinely attends the gym or if not you are not and know someone who does ask them or yourself what leg exercises they complete. Most likely you will get a lot of exercises that primarily focus on quadriceps strengthening; such as the knee extension machine, leg press, squats, box jumps, etc. (The reason I say primarily is because even though some of those exercises work all the muscles of the leg, people do them improperly which tends to place excessive load on the quadriceps.) Then consider the hamstrings exercises you will see people participate in at the gym; mostly the hamstring curl machine and the dead lift. The scales will tip in the quadriceps exercise direction. The major problem with the hamstring curl machine is that it only works the distal aspect of the hamstrings at the knee. The dead lift allows you to work the proximal aspect of the hamstrings but the issue is that in doing so you overload the lower back. Both exercises are also not functional in nature. When I use the word functional I use it in reference the hamstrings needing to work at the hip and the knee at the same time while completing the different types of muscle contractions mentioned earlier. Think of it as primarily a motor control problem. Just because you do exercises to strengthen the hip flexors, then exercises for quadriceps, and so forth for hamstrings and glutes the timing of these muscles to fire and work together is not being worked on. So how do we go about improving this and what is an appropriate strength ratio for the quadriceps to hamstrings to provide optimal performance and prevent future injury?
I will be working on answering the strength ratio question today and focus on concentric and eccentric muscle contractions. I have reviewed two articles that helped to tackle this question. The article by Kim and Hong studied 82 male and female Division III intercollegiate basketball and soccer players and concluded that a ratio of hamstrings to quadriceps should be greater than 60% (The maximum strength of the hamstrings should be about 60% of the maximum strength of the quadriceps). They suggested to work more on landing techniques rather than jumping techniques to better improve the hamstrings as opposed to the quadriceps.
But I wanted to further delve into the correlations that two muscle groups have when compared with the different muscle contractions (eccentric vs. concentric). So I reviewed another article by Hadzic et al. who studied 95 male professional volleyball players and found that the higher level volleyball players had significantly higher hamstrings strength (both eccentric and concentric) and hamstrings eccentric strength to quadriceps concentric strength ratios (A ratio of >70% hamstrings to quadriceps for the international level compared to 62-66% for the two lower level professional volleyball player groups).
(Click on the links below for access to the articles)
Kim D and Hong J. Hamstring to quadriceps strength ratio and noncontact leg injuries: a prospective study. Isokinect Exerc Sci. 2011; 19:1-6.
Purpose: To investigate the relationship of hamstrings and quadriceps strength imbalance with overall non-contact lower extremity injuries.
Methods: Subjects were 82 male and female intercollegiate Division III basketball and soccer players. The subjects were followed over a full season. Participants completed 3 maximal muscle contractions for knee flexion and extension at 60 degrees/second over a 90 degree range. The researchers only counted injuries that were non-contact in nature.
Results: There were 35 right leg injuries and 32 left leg injuries during the season. The researchers showed that participants with a hamstrings to quadriceps ratio of greater than 60% had significantly less of injury to their legs than subjects with less than 60%.
Limitations: The researchers believed that only using one testing parameter (60 degrees/second) could have limited the results. Also they thought that only assessing concentric strength could have limited their findings.
Hadzic V, Sattler T, Markovic G, Veselko M, Dervisevic E. The isokinetic strength profile of quadriceps and hamstrings in elite volleyball players. Isokinet Exerc Sci. 2010; 18: 31-37.
Purpose: To establish the concentric and eccentric strength of quadriceps and hamstrings in healthy male volleyball players varying in age, playing position, and playing level. To evaluate the differences in concentric and eccentric peak torques, various strength ratios and bilateral leg strength asymmetries among different playing positions, age groups, and playing levels. To assess bilateral concentric and eccentric strength asymmetry of quadriceps and hamstrings.
Methods: The researchers were able to examine 95 male national Division I and II professional volleyball players from Slovenia. Quadriceps and hamstrings muscles were tested eccentrically and concentrically using an isokinetic dynamometer. They measured subjects at 60 degrees per second at a range of 60 degrees for 30 degrees to 90 degrees knee flexion. The subjects completed 5 consecutive maximal concentric quadriceps and hamstrings contractions and 5 maximal eccentric quadriceps and hamstrings contractions with 60 second breaks in between. Participants had a short 5 minute warm-up on a bike and stretching.
Results: The higher level international volleyball players had significantly higher peak torque on the right for eccentric hamstrings strength when compared to the Division I and II players and significantly stronger right concentric hamstrings strength when compared to the Division II players. They also found that international players (73%) had higher eccentric hamstrings strength to concentric quadriceps strength when compared to Division I professional players (66%) and significantly higher values when compared to Division II professional players (62%).
Limitations: The researchers did not determine any limitations with their study but conclusions can be drawn based on personal findings.