Biomechanical Influences that cause cycling injuries
By Shaun O'Connor, PT
Do you remember when you were a kid and you sang the song “Dem Bones”… the hip bone is connected to the thigh bone…Well the cyclists who is in pain must understand the truth behind this song. Because the back, pelvis, hips and legs work together and directly affect each other.
Biomechanical cause of cycling overuse injuries
Low back, hip, and knee pain are injuries common to cyclists. These injuries typically develop slowly over time. The symptoms generally start out as an ache and eventually become painful enough to affect ones ability to pedal and/or perform daily routine tasks.
Many cyclists who experience chronic back, hip and/or knee pain suffer from pelvic asymmetry due to muscle imbalance ( also called pelvic instability). The pelvis has a unique role in affecting posture and movement in the spine and extremities. An imbalance or asymmetry of muscle function at the pelvis can affect the function of the low back, hip and knee.
Cyclists commonly present with an excessive anterior pelvic tilt. When the pelvis is anteriorly rotated, the base of the pelvis is tipped forward and the rest of the spine has no choice but to follow. This will increase the curvature (lordosis) of the lower back. This deep curvature of the back can create various problems including muscle spasms, pinched nerves and possible damage to the lumbar disc.
Here is an example that can be particularly problematic and illustrate the “Dem Bones” song. Once again the ligaments of the pelvis, can turn the femur (thigh bone) inward more than it should because of the position of the pelvic bones. This inward rotation of the femur then may cause of the lateral thigh muscles to over tighten creating compression of the hip bursa. Over time this can cause the bursa to become inflamed and painful causing severe hip pain. At the knee joint, inward rotation of the femur may cause misalignment between the femur, the patella (knee cap), and the lower leg bone leading to joint irritation/pain and may cause future degeneration of the knee.
The cause of an anterior pelvic tilt with cycling is often due to the biomechanics of cycling which involves the repetitive use of a family of muscles in the front of the thigh and groin (hip flexors and quadriceps) in a fixed plane of movement. The repeated movement of pedaling will cause these muscles to become stronger and less flexible. The opposing muscles in the back of the thigh (hamstrings and gluteals) become longer and positionally weaker.
As the pelvis tips forward, the hamstrings (back of the thigh) become stretched. An elongated muscle will become weaker over time. As a result, the body will compensate by relying on other muscle groups to maintain an upright posture. Normally, the body uses the hamstrings, gluteals and abdominals to maintain an upright posture. Now, the body will compensate by overusing the quadriceps and hip flexors to maintain an upright posture. This leads to a continous cycle of further weakening of the hamstrings, gluteals and abdominal obliques muscle groups. Overtime this, coupled with spending hours in a relatively fixed posture, will often induce an anterior pelvic tilt.
Example: A recreational cyclists who pedals at 90 rpm’s for one hour will have completed 5400 pedal revolutions, or up to 1.5 million pedal strokes in a 5000 mile year. These numbers help to illustrate how prone cyclists are to developing muscle imbalances and over use injuries.
How to prevent anterior pelvic tilt
To prevent pelvic instability (anterior pelvic tilt) cyclists should routinely perform hamstring , gluteal and abdominal strengthening and maintain good flexibility in the hip flexors, quadriceps and back extensors. So take an active role in this sport you love, to prevent and minimize overuse injuries. With adjustments to your program you can prevent and correct muscle imbalances and get out of that “cycle” of pain.
It’s important to note that proper bike fit and a well thought out training program are equally important in preventing overuse injuries.
Shaun is a licensed physical therapist and is the clinical director for Timberlane Physical Therapy. He is an active member of the American Physical Therapy Association. He is a former competitive cyclist. He can be reached at Timberlane Physical Therapy, 802-864-3785 or at oconnorpt@hotmail.com.