Longitudinal midsole bending stiffness and elasticity are two critical features in the construction of running shoes. Stiff elastic materials (eg, carbon fiber) can be used to alter the midsole bending behavior. The purpose of this study was to investigate the effects of midsole stiffness and elasticity manipulation on metatarsophalangeal (MTP) joint mechanics during running in 19 male subjects at 3.5 m/s. Midsole bending stiffness and elasticity were modified by means of carbon fiber insoles of varying thickness. Stiffening the shoe structures around the MTP joint caused a shift of the point of force application toward the front edge of the shoe-ground interface. Negative work was significantly reduced for the stiffest shoe condition and at the same time a significant increase of positive work at the MTP joint was found. It seems plausible that the increase in positive work originates from the reutilization of elastic energy that was stored inside the passive elastic structures of the shoe and toe flexing muscle tendon units. Further, an increase in midsole longitudinal bending stiffness seems to alter the working conditions and mechanical power generation capacities of the MTP plantar flexing muscle tendon units by changing ground reaction force leverage and MTP angular velocity.
Steffen Willwacher, Manuel König, Wolfgang Potthast and Gert-Peter Brüggemann
Ming Xiao and Jill Higginson
Generic muscle parameters are often used in muscle-driven simulations of human movement to estimate individual muscle forces and function. The results may not be valid since muscle properties vary from subject to subject. This study investigated the effect of using generic muscle parameters in a muscle-driven forward simulation on muscle force estimation. We generated a normal walking simulation in OpenSim and examined the sensitivity of individual muscle forces to perturbations in muscle parameters, including the number of muscles, maximum isometric force, optimal fiber length, and tendon slack length. We found that when changing the number of muscles included in the model, only magnitude of the estimated muscle forces was affected. Our results also suggest it is especially important to use accurate values of tendon slack length and optimal fiber length for ankle plantar flexors and knee extensors. Changes in force production by one muscle were typically compensated for by changes in force production by muscles in the same functional muscle group, or the antagonistic muscle group. Conclusions regarding muscle function based on simulations with generic musculoskeletal parameters should be interpreted with caution.
Alison R. Valier, Ryan S. Averett, Barton E. Anderson and Cailee E. Welch Bacon
Shoulder pain is a common musculoskeletal complaint and is often associated with shoulder impingement. The annual incidence of shoulder pain is estimated to be 7% of all injuries, and is the third-most-common type of musculoskeletal pain. Initial treatment of shoulder impingement follows a conservative plan and emphasizes rehabilitation programs as opposed to surgical interventions. Shoulder rehabilitation programs commonly focus on strengthening the muscles of the shoulder complex and, more specifically, the rotator cuff. The rotator cuff is a primary dynamic stabilizer of the glenohumeral joint, using both eccentric and concentric contractions. The posterior rotator cuff, including teres minor and infraspinatus, works eccentrically to decelerate the arm during overhead throwing. Exercises to strengthen the rotator cuff and the surrounding dynamic stabilizers of the shoulder girdle vary and include activities such as internal and external rotation, full-can lifts, and rhythmic stabilizations. Traditionally, shoulder rehabilitation programs have focused on isotonic concentric contractions. Common strengthening exercises typically involve movements that result in shortening the muscle length while simultaneously loading the muscles. However, recent attention has been given to eccentric exercises, which involve lengthening of the muscle during loading, for the treatment of a variety of different tendinopathies including those of the Achilles and patellar tendons. The eccentric, or lengthening, motion is thought to be beneficial for people who are involved in activities that place eccentric stress on their shoulder, such as overhead throwers. Based on studies related to the Achilles tendon, eccentric exercise may positively influence the tendon structure by increasing collagen production and decreasing neovascularization. The changes that occur as a result of eccentric exercises may improve function, strength, and performance and decrease pain more than concentric programs, producing better patient outcomes. Although eccentric strength training has been shown to provide strength gains, there are no clear guidelines as to the inclusion of this form of exercise training in shoulder rehabilitation programs for the purposes of improving function and decreasing pain.
Focused Clinical Question:
Does adding an eccentric-exercise component to the rehabilitation program of patients with shoulder impingement improve shoulder function and/or decrease pain?
Renato Semadeni and Kai-Uwe Schmitt
In this study a numerical model of a skier was developed to investigate the effect of different rehabilitation strategies after anterior cruciate ligament (ACL) rupture.
A computer model using a combined finite-element and multibody approach was established. The model includes a detailed representation of the knee structures, as well as all major leg muscles. Using this model, different strategies after ACL rupture were analyzed.
The benefit of muscle training to compensate for a loss of the ACL was shown. The results indicate that an increase of 10% of the physiological cross-sectional area has a positive effect without subjecting other knee structures to critical loads. Simulating the use of a hamstring graft indicated increasing knee loads. A patellar-tendon graft resulted in an increase of the stress on the lateral collateral ligament.
Muscle training of both extensors and flexors is beneficial in medical rehabilitation of ACL-deficient and ACL-reconstructed knees.
Michael R. McCarthy, Barton P. Buxton, W. Douglas B. Hiller, James R. Doyle and Denis Yamada
In an attempt to quantify the current standards in surgical procedures and rehabilitation protocols utilized to treat patients with anterior cruciate ligament (ACL)-deficient knees, a 19-question survey was sent to members of the Hawaii Orthopedic Association. The findings indicated that only 54% (30/56) of the respondents were performing ACL reconstructions, of which 87% (26/30) were performing an intra-articular procedure and none were performing extra-articular procedures exclusively. The findings further indicate that 80% (24/30) of the 30 respondents performing ACL reconstructions were using an arthroscopically assisted, bone-tendon-bone autograft procedure. However, in marked contrast to the uniformity that existed concerning the surgical procedure, there was a drastic difference in the rehabilitation protocols and procedures that were recommended postoperatively. The most apparent differences in rehabilitation protocols existed in the utilization and initiation of open versus closed type kinetic chain exercises and activities.
Joseph B. Myers
Shoulder pain is a common complaint among overhead athletes. Oftentimes, the cause of pain is impingement of the supraspinatus, bicipital tendon, and subacromial bursa between the greater tuberosity and the acromial arch. The mechanisms of impingement syndrome include anatomical abnormalities, muscle weakness and fatigue of the glenohumeral and scapular stabilizers, posterior capsular tightness, and glenohumeral instability. In order to effectively manage impingement syndrome nonoperatively, the therapist must understand the complex anatomy and biomechanics of the shoulder joint, as well as how to thoroughly evaluate the athlete. The results of the evaluation can then be used to design and implement a rehabilitation program that addresses the cause of impingement specific to the athlete. The purpose of this article is to provide readers with a thorough overview of what causes impingement and how to effectively evaluate and conservatively manage it in an athletic population.
Allyson M. Carter, Stephen J. Kinzey, Linda F. Chitwood and Judith L Cole
Proprioceptive neuromuscular facilitation (PNF) is commonly used before competition to increase range of motion. It is not known how it changes muscle response to rapid length changes.
To determine whether PNF alters hamstring muscle activity during response to rapid elongation.
2 X 2 factorial.
Twenty-four women; means: 167.27 cm, 58.92 kg, 21.42 y, 18.41% body fat, 21.06 kg/m2 BMI.
Measurements before and after either rest or PNF were compared.
Main Outcome Measures:
Average muscle activity immediately after a rapid and unexpected stretch, 3 times pretreatment and posttreatment, averaged into 2 pre-and post- measures.
PNF caused decreased activity in the biceps femoris during response to a sudden stretch (P = .04). No differences were found in semitendinosus activity (P = .35).
Decreased muscle activity likely results from acute desensitization of the muscle spindle, which might increase risk of muscle and tendon injury.
George Forrest and Kurt Rosen
Ultrasound is a commonly used modality of deep heating. Two techniques of application have been recommended: a technique in which the applicator head is applied directly to the subject and an immersion technique, The purpose of this study was to determine whether ultrasound treatments using the immersion technique in degassed water are as effective as ultrasound treatments using the direct technique of application in raising the temperature of periarticular structures into the therapeutic range. The limbs of a pig were treated with the direct and immersion techniques of application. Temperatures of the skin surface and of the extensor tendons of the ankle were taken before and after both methods of application. Treatments with the applicator head in direct contact with the limb of the subject were the more effective form of heating.
Mark S. De Carlo, Kecia E. Sell, K. Donald Shelbourne and Thomas E. Klootwyk
It is well established that intra-articular anterior cruciate ligament reconstruction with autogenous bone-patellar tendon-bone graft provides satisfactory long-term stability. However, the rehabilitation programs employed following this surgical procedure have been a topic of considerable debate. This paper describes an accelerated rehabilitation protocol that is divided into four phases. The first phase encompasses the preoperative period, during which the patient will work to decrease swelling and restore range of motion and strength. The second phase involves Weeks 1 and 2 following surgery, with the patient emphasizing immediate terminal knee extension and weight bearing. The final two phases involve improving lower extremity strength and full return to daily and athletic activities. This accelerated rehabilitation protocol has resulted in an earlier return of range of motion and strength without compromising ligamentous stability.
Sheri A. Hale
To review the etiology of patellar tendinopathy as it relates to clinical management of chronic patellar-tendon disease in athletes.
Information was gathered from a MEDLINE search of literature in English using the key words patellar tendinitis, patellar tendonitis, patellar tendinosis, patellar tendinopathy, and jumper’s knee.
All relevant peer-reviewed literature in English was reviewed.
The etiology of patellar tendinopathy is multifactorial, incorporating both intrinsic and extrinsic factors. Age, muscle flexibility, training program, and knee-joint dynamics have all been associated with patellar tendinopathy. The roles of gender, body morphology, and patellar mobility in patellar tendinopathy are unclear.
The pathoetiology of patellar tendinopathy is a complex process that results from both an inflammatory response and degenerative changes. There is a tremendous need for research to improve our understanding of the pathoetiology of patellar tendinopathy and its clinical management.