In last week’s post, I discussed how alternating running shoes can decrease injury risk.
This week, I’ll be discussing the findings from a 2015 study published in the Journal of Orthopedic and Sports Physical Therapy (JOSPT). Particularly the importance of quad strength in runners.
You can read the abstract below.
Type of Study
A cross-sectional study is a study where data is collected at a specific point in time from a particular population of subjects. This type of study provides a snapshot of data that may be present within a specific population; in this case, runners with and without low back pain.
Two groups were used in this study.
On group consisted of 18 healthy recreational runners without low back pain.
The second group consisted of 18 recreational runners with chronic low back pain.
What Did They Look At?
Six different variables were measured in this study:
- Lumbar extensor muscle fatigability
Participants were asked to maintain this position (pictured below) for 2 minutes while EMG activation was recorded for two lumbar extensor muscles (the iliocostalis and longissimus).
- Transverse Abdominis Muscle Activation
The researchers utilized real-time ultrasound imaging to determine the thickness of this muscle at rest and then during a straight leg raise. The change in muscle thickness was used to quantify the activation of this muscle.
- Lumbar Multifidus Muscle Activation
The activation of this muscle was quantified in a similar fashion as the transverse abdominis (discussed above) during a diagonal arm raise.
4-6. Lower Extremity Isokinetic Torque of the Hip Extensors, Hip Abductors, and Knee Extensors (Quadriceps)
Torque is a force that causes a rotation about an axis. In this case, it would be the hip and knee joints. Isokinetic means that this type of muscle contraction occurred at a constant speed. Researchers will often utilize torque, at a certain speed of movement, to quantify muscle strength.
The peak torque was normalized to each individual’s body mass and could be utilized as a measure of hip extensor, hip abductor, and knee extensor strength.
Of the six variables measured, only knee extensor strength was significantly less in the group of runners with chronic low back pain. Lumbar multifidus activation was also significantly less but only among men.
The authors concluded that weakness of the knee extensors (quadriceps) may increase knee joint stiffness and, therefore, minimize the capacity for shock attenuation.
This increased shock, from the ground, may transmit increased force to the lumbar spine and increase the susceptibility to low back pain.
The quadriceps (and calves) work as the primary muscles to attenuate shock during the stance phase of running. It makes sense that this muscle group would be more limited in those with low back pain.
However, I generally like to develop my own hypothesis when I start to read a paper’s methods. In this instance, I would have bet that the hip extensor and abductor strength would have been more reduced in those with LBP.
I generally think ‘core’ strength is sort of overrated, in terms of it being a cause/risk factor for injury, so the results about TA/multifidus activation and lumbar extensor endurance were not surprising.
The results of this study highlight the importance of the quadriceps strength in runners. I believe targeted quad strengthening should be performed at least twice a week as part of a well-rounded strength and conditioning program for runners.
Next week, I’ll be discussing some of my favorite methods for strengthening the quadriceps.
Questions for Readers
What are some of your favorite ways to strengthen the quadriceps? What other factors do you believe are important in the management/prevention of low back pain in runners?
Cai, C., & Kong, P. W. (2015). Low back and lower-limb muscle performance in male and female recreational runners with chronic low back pain. Journal of Orthopaedic & Sports Physical Therapy, 45(6), 436-443.
Cover Image created using Essential Anatomy 5 with permission from 3D4Medical.