, a runner who demonstrates considerably less than 45?of knee flexion may

, a runner who 3-MA dose demonstrates considerably less than 45?of knee flexion may suggest reduced shock absorption, and intervention may be OPC-8212 side effects warranted. Some data exist suggesting that lower knee flexion (<40? may be associated with certain subgroups of patients with patellofemoral pain.22 Knee stiffness, a variable that includes both reduced knee flexion and/or increased knee flexion moment during stance phase, may be associated with tibial stress fractures.23 Hip Extension During Late Stance Reduced hip extension during late stance is a common observation in the recreational runner (Fig. 6). It is traditionally believed that lack of hip extension may be associated with reduced flexibility of the iliopsoas muscle. However, the optimal amount of hip extension during running remains elusive. It is possible that the required amount of hip extension is not the same for each runner, but related to other characteristics of their running form. For example, a fairly slow runner may have a very compact stride, demonstrate approximately 10?of peakAuthor Manuscript Author Manuscript Author Manuscript Author ManuscriptPhys Med Rehabil Clin N Am. Author manuscript; available in PMC 2016 February 01.SouzaPagehip extension and not require any intervention. However, a different runner, with a long stride and perhaps a faster pace, may also have approximately 10?of hip extension, but also concurrently demonstrate a significant overstride pattern (landing with the foot out in front of the center of mass) with higher impact loading and braking forces. The latter runner may require stride modification or improved hip extension during running to modify these forces that could contribute to injury. Commonly observed compensations for persons with reduced hip extension include (1) increased lumbar spine extension, (2) bounding, a strategy to increase float time to increase overall stride length in the absence of adequate hip extension, (3) increased overstriding, including excessive reaching during initial contact as a strategy to increase stride length, and (4) increased cadence to increase running speed in the presence of a limited hip extension. Trunk LeanAuthor Manuscript Author Manuscript Author ManuscriptOverstridingTrunk lean is a variable that has received little attention in the scientific literature. However, this is not the case in the popular running non eer-reviewed literature. Many running styles, including ChiRunning, pose running, and even barefoot running have included cues for novice runners to increase trunk lean. A focus on leaning "from the ankles," rather than increasing hip flexion to achieve the trunk lean, seems to be a priority for some styles. Many running experts suggest that trunk lean is a key component to correct running posture. However, very little has been done on the research side of this issue. A recent article by Teng and Powers24 demonstrated that a small increase in trunk lean ( 7? resulted in a significant lowering of the stress across the patellofemoral joint without a significant increase in ankle demand, suggesting that this strategy may be important for runners with patellofemoral pain. The overall findings were that reduced trunk flexion (more upright posture) was associated with greater knee loads. In contrast, increased trunk flexion shifted demand away from the knee joint, and to the hip and ankle (although the latter was not statistically higher).25 However, the authors warn that this study was performed in healthy subj., a runner who demonstrates considerably less than 45?of knee flexion may suggest reduced shock absorption, and intervention may be warranted. Some data exist suggesting that lower knee flexion (<40? may be associated with certain subgroups of patients with patellofemoral pain.22 Knee stiffness, a variable that includes both reduced knee flexion and/or increased knee flexion moment during stance phase, may be associated with tibial stress fractures.23 Hip Extension During Late Stance Reduced hip extension during late stance is a common observation in the recreational runner (Fig. 6). It is traditionally believed that lack of hip extension may be associated with reduced flexibility of the iliopsoas muscle. However, the optimal amount of hip extension during running remains elusive. It is possible that the required amount of hip extension is not the same for each runner, but related to other characteristics of their running form. For example, a fairly slow runner may have a very compact stride, demonstrate approximately 10?of peakAuthor Manuscript Author Manuscript Author Manuscript Author ManuscriptPhys Med Rehabil Clin N Am. Author manuscript; available in PMC 2016 February 01.SouzaPagehip extension and not require any intervention. However, a different runner, with a long stride and perhaps a faster pace, may also have approximately 10?of hip extension, but also concurrently demonstrate a significant overstride pattern (landing with the foot out in front of the center of mass) with higher impact loading and braking forces. The latter runner may require stride modification or improved hip extension during running to modify these forces that could contribute to injury. Commonly observed compensations for persons with reduced hip extension include (1) increased lumbar spine extension, (2) bounding, a strategy to increase float time to increase overall stride length in the absence of adequate hip extension, (3) increased overstriding, including excessive reaching during initial contact as a strategy to increase stride length, and (4) increased cadence to increase running speed in the presence of a limited hip extension. Trunk LeanAuthor Manuscript Author Manuscript Author ManuscriptOverstridingTrunk lean is a variable that has received little attention in the scientific literature. However, this is not the case in the popular running non eer-reviewed literature. Many running styles, including ChiRunning, pose running, and even barefoot running have included cues for novice runners to increase trunk lean. A focus on leaning "from the ankles," rather than increasing hip flexion to achieve the trunk lean, seems to be a priority for some styles. Many running experts suggest that trunk lean is a key component to correct running posture. However, very little has been done on the research side of this issue. A recent article by Teng and Powers24 demonstrated that a small increase in trunk lean ( 7? resulted in a significant lowering of the stress across the patellofemoral joint without a significant increase in ankle demand, suggesting that this strategy may be important for runners with patellofemoral pain. The overall findings were that reduced trunk flexion (more upright posture) was associated with greater knee loads. In contrast, increased trunk flexion shifted demand away from the knee joint, and to the hip and ankle (although the latter was not statistically higher).25 However, the authors warn that this study was performed in healthy subj.