Posts tagged biomechanics
Reducing Impact Forces In Runners
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In our previous blogs, we have described interventions designed to reduce the high rates of running related injuries. To date, our best Physical Therapy interventions include controlling training volume, concurrent strength training, and gait retraining. In our Boulder Physical Therapy practice we aim to reduce peak loading forces at foot strike in our runners. This can be achieved by increasing a runner’s forward lean (from the ankles) and stride length to reduce braking forces at the foot and ankle, as well as, reducing vertical oscillation in the flight phase of running. A recent article reviewed the use of real time biofeedback to reduce these braking forces in runners.

Napier and colleagues in the Journal of Orthopedic and Sports Physical Therapy utilized biofeedback in healthy, female runners with high rates of peak braking forces (2018). Each participant was provided with an 8 session gait retraining program aimed to increase step frequency and reduce step length. Basic cuing, such as “land softer”, can be used in this population to reduce the braking forces and in turn conserve energy for forward propulsion. Authors reported significantly reduced peak braking forces after the gait retraining sessions. In addition, these gait changes have been previously associated with increased running economy and performance.

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Is My Hip Or Knee More To Blame For My Knee Pain?
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The knee is a vulnerable joint at times due to its' location adjacent to the two long levers of our thigh and leg bones.  The length of the levers allows the ankle and hip to exert a high amount of forces across the knee.  The importance of treating these adjacent joints in patients with knee pain is reflected in our current understanding of functional movements including walking, stair climbing, hiking, and running.  Patient's who experience knee pain during these movements frequently demonstrate hip weakness and an inability to control their knee position during single limb loading.  The increased load under the knee cap is due to abnormal pressure and contact area on the thigh (femur).  A recent biomechanical analysis quantifies the knee cartilage stresses at the patellofemoral joint highlighting the importance of analyzing the hip in patients with knee pain.

Liao and colleagues analyzed cartilage stresses between the knee cap and thigh during squatting tasks with varying degrees of thigh and shin rotation (Clin Biomech. 2018).  The authors found a progressively greater cartilage stresses with increasing degrees of thigh rotation, but found a decrease in cartilage stress with progressive shin rotation.  Additionally, progressive thigh movement toward the midline of the body also was shown to increase knee cartilage loading.  The authors concluded thigh internal rotation and movement toward the midline had the greatest impact on knee cartilage forces.  These findings support prior research studies highlighting the importance of examining and treating the hip in patients with knee pain.

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Leg strength not found to be associated with mechanics during cutting
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Cutting movements utilized in soccer, football, basketball, and lacrosse are one of the most common mechanisms of non contact knee injuries.  Athletes who cut with poor mechanics demonstrate larger hip and knee angles placing the ligaments of the knee, such as the ACL, at greater risk of injury.  These movements at the knee are driven by two main factors: leg weakness and poor mechanics.  A recent study analyzed the mechanics of athletes performing cutting movements to determine the extent strength plays a role in poor mechanics.

Husted and colleagues analyzed 85 athletes for hip strength and muscle activation during a cutting task (International Journal of Sports Physical Therapy, 2018).  The authors found no association between lower body strength testing measurements and muscle contraction during the cutting task.  This study highlights the importance of first improving an athlete's lower body strength to give them the capacity to move properly.  Once the strength foundation is established we are able to work on the athlete's mechanics to ensure they utilize the most optimal movement strategy for their sport specific task.  This study highlights the importance of not assuming mechanics will improve with a strength training program alone.

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Shoulder Blade Mechanics and Shoulder Pain
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The shoulder blade and upper arm bone move together to produce a variety of arm and hand movements essential for life and sport.  Proper movement of the shoulder blade is required to produce normal mechanics at the joint surfaces and maintain the length and function of the shoulder blade and shoulder muscles.  Abnormal mechanics between these bones has been noted in many upper body conditions including neck pain, shoulder impingement, and rotator cuff injuries.  It is currently not known if these abnormal mechanics are the cause or result of pain.  In addition, we often see poor mechanics in individuals who do not have any shoulder symptoms. 

Researchers and clinicians have blamed a patient's poor mechanics on a lack of shoulder blade strength.  For example, those patients with weakness will have poor mechanics and in turn will respond well to a strengthening program.  Similar to what Physical Therapists find in patients with knee pain, often poor mechanics are found in patients with good strength.  These patients often respond better to coordination or motor control exercises instead of a program focused on strength development.

A recent research study by Hannah et al. confirmed this discrepancy between strength and shoulder blade mechanics (International Journal of Sports Physical Therapy, 2017).  The researchers recruited 40 college participants of which 27 (68%) demonstrated poor scapular mechanics.  The participants' strength assessments were compared to their age matched peers with good mechanics.  The authors found no significant differences between those with normal or poor shoulder blade mechanics.  A limitation of this study was its' testing of only healthy patients.  It is not known if this study would hold up in a population of patients with shoulder pain or injury. 

Patient's with shoulder pain and poor mechanics must be assessed for strength and control to determine the most appropriate treatment plan.  To learn more about how you can improve your strength and shoulder mechanics contact your local Physical Therapist.

Age and Running Biomechanics

Last year an estimated 30 million people ran at least 50 days for exercise and health benefits (Running USA).    The fastest growing segment of the running community includes older adults who gain impressive cardiovascular, muscle, bone, and mental health benefits compared to their sedentary peers.   In addition, contrary to popular but incorrect old wives tales about running and arthritis these active older adults experience less pain than their sedentary peers (Bruce et al. 2005).  Our previous posts on the older adult running community detailed specific cardiovascular and gait changes which take place due to aging.   These losses in flexibility, strength and balance increase the already high rates of overuse injuries among runners.  A better understanding of running gait changes through the life cycle may help us prevent future injuries among this population of runners. 

A recent study in the Journal Medicine and Science in Sports and Exercise studied the running gaits of 110 experienced runners between the ages of 18-60  (DeVita et al. 2016).  Consistent with the previous literature the authors noted each age group older than 18 demonstrated a progressive loss of running velocity.  These changes were largely due to decreased stride length vs. stride frequency compared to the younger participants.  Further, older runners ran with decreased ankle power which translated into decreased horizontal and vertical forces at push off.  The presence of ankle changes with age, but the absence of hip or knee changes, indicates the importance of the ankle for both energy absorption and propulsion during running.