The purpose of this study was to investigate the effect of heel construction on ankle joint mechanics during the early stance phase of running. Kinematic and kinetic parameters (ankle joint angles, angular velocities and joint moments, lever arms of ground reaction force, triceps surae muscle tendon unit lengths, and rates of muscle tendon unit length change) were calculated from 19 male subjects running at 3.3 m/s in shoes with different heel constructions. Increasing heel height and posterior wedging amplified initial plantar flexion velocity and range. The potential for a muscle to control the movement of a joint depends upon its ability to produce joint moments. Runners in this study showed decreased external eversion moments and an increase in eversion range. Maximum eversion angles were not significantly affected by shoe conditions. Without considerable tendon prestretch, joint moment generation potentials of triceps surae and deep plantar flexors might be inhibited due to rapid plantar flexion based on the force–velocity relationship. It could be speculated that increasing ankle inversion at heel strike could be a strategy to keep maximum eversion angles inside an adequate range, if joint moment generation potentials of deep plantar flexors are inhibited due to rapid plantar flexion.
Steffen Willwacher, Wolfgang Potthast, Markus Konrad and Gert-Peter Brüggemann
Cori Sinnott, Hayley M. White, Jennifer W. Cuchna and Bonnie L. Van Lunen
Achilles tendinopathy is a painful condition commonly affecting the general and athletic population. It presents with localized pain, stiffness, and swelling in the midportion of the Achilles tendon. The physical stress placed on the tendon results in microtrauma, which leads to subsequent inflammation and degeneration. While it is not surprising that this condition affects the physically active, nearly one-third of Achilles tendinopathy cases occur in sedentary individuals. Etiology for this condition stems from a change in loading patterns and/or overuse of the tendon, resulting in microscopic tearing and degenerative changes. There are numerous causes contributing to the maladaptive response in these patients, such as mechanical, age-related, genetic, and vascular factors. The treatment for these patients is typically load management and eccentric strengthening of the gastrocnemius–soleus complex. Unfortunately, conservative treatment can lead to surgical intervention in up to 45% of cases. A relatively new phenomenon in the treatment of this condition is the use of autologous blood injections (ABI) and platelet-rich plasma injections (PRPI). This need for a less invasive treatment fostered more investigation into ABI and PRPI to treat these nonresponsive patients. However, the evidence concerning the effectiveness of these treatments in patients with Achilles tendinopathy has not been synthesized.
Focused Clinical Question:
In patients with Achilles tendinopathy, how do variations of ABI and PRPI compared with a placebo and/or eccentric training affect pain and function?
Liang-Ching Tsai, Irving S. Scher and Christopher M. Powers
The purpose of this study is to describe an MRI-based EMG-driven knee model to quantify tibiofemoral compressive and shear forces. Twelve healthy females participated. Subjects underwent 2 phases of data collection: (1) MRI assessment of the lower extremity to quantify muscle volumes and patella tendon orientation and (2) biomechanical evaluation of a drop-jump task. A subject-specific EMG-driven knee model that incorporated lower extremity kinematics, EMG, and muscle volumes and patella tendon orientation estimated from MRI was developed to quantify tibiofemoral shear and compressive forces. A resultant anterior tibial shear force generated from the ground reaction force (GRF) and muscle forces was observed during the first 30% of the stance phase of the drop-jump task. All of the muscle forces and GRF resulted in tibiofemoral compression, with the quadriceps force being the primary contributor. Acquiring subject-specific muscle volumes and patella tendon orientation for use in an EMG-driven knee model may be useful to quantify tibiofemoral forces in persons with altered patella position or muscle atrophy following knee injury or pathology.
Zachary K. Winkelmann and Kenneth E. Games
An 18-year-old, male collegiate basketball athlete complained of right testicular pain following basketball activities. The patient’s imaging denoted edema within the pubis at the insertion of the adductor longus tendon and rectus sheath aponeurosis consistent with inguinal disruption. The patient underwent conservative rehabilitation and attempted to return to participation with increased pain. Subsequently, the patient underwent surgery. Following surgical intervention, the patient underwent 6 weeks of rehabilitation with basketball-specific considerations. On conclusion, the patient was pain free and returned to activity. This case is unique due to the insidious onset, sport in which the patient participated, and failed conservative management.
Jin Hyuck Lee, Ji Soon Park and Woong Kyo Jeong
A 27-year-old man presented with a 5-year history of left periscapular muscle spasm and constant shoulder pain in activities of daily living. Magnetic resonance imaging (MRI) and physical examination revealed scapular dyskinesis without pathologic lesions in the rotator cuff tendon and labrum. However, there was hypertrophy of the serratus anterior muscle on computed tomography (CT). Scapular dyskinesis can be caused by isolated hypertrophy of the serratus anterior. After 4 months of physiotherapy, including manual therapy, therapeutic exercises, and neuromuscular retraining, the patient recovered normal scapular movement and reported no pain.
Sharon J. Dixon and David G. Kerwin
In this study sagittal plane joint angles of the lower extremity were used to obtain an indication of the influence of heel lift manipulation on Achilles tendon strain in running. The influence of increased heel lift on lower extremity kinematics was investigated for 8 heel striking subjects. With increased heel lift, all subjects demonstrated reductions in peak ankle dorsi-flexion and consistent values of peak knee flexion, indicating that there were reductions in peak Achilles tendon strain. Group analysis demonstrated that the reductions in peak ankle angle were statistically significant (p < .01). Typically, subjects also demonstrated adjustments in initial ankle angle, whereby the amount of ankle dorsi-flexion at initial ground contact was reduced with increased heel lift. Group mean data indicated that a 15-mm heel lift resulted in a mean decrease in initial ankle dorsi-flexion of 3.9°, while peak ankle dorsi-flexion was also reduced by 3.9°. It is suggested that the initial ankle angle adjustment acted to maintain a similar range of ankle joint movement in the period from initial ground contact to peak ankle dorsi-flexion across heel lift conditions. The distinct behavior of one subject, who demonstrated an increased ankle dorsi-flexion at ground impact, has highlighted the importance of considering single subject results in studies of footwear variation in running.
André Luiz Felix Rodacki, Neil Edward Fowler and Simon Bennett
The aim of this study was to compare the kinematic pattern and the segmental movement co-ordination when the trunk segment was constrained in different positions during plyometric rebound jumps. Nine skilled volleyball players, experienced in plyometric training, were asked to perform a random series of maximal rebound jumps, using three different seat arrangements (90°, 135°, and 180°) in a pendulum swing device. From two-dimensional filming, performed in a right sagittal plane at 200 Hz, it was possible to calculate ankle, knee, and hip displacements; velocities; and muscle-tendon lengths. The subjects showed similar ankle and knee angles between experimental conditions. The hip joint angle differed significantly between conditions. Only the muscle-tendon lengths of the biarticular muscles spanning the knee/hip were affected by the seat arrangement variations. Significantly greater knee angular velocities were observed in the upright sitting posture (90°). The hip was consistently the first joint to extend. The ankle and knee joint reversals were not invariant, regardless of the seat arrangement. The movement co-ordination strategy did not differ across postural variations.
Steffen Willwacher, Manuel König, Wolfgang Potthast and Gert-Peter Brüggemann
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.
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.
Andreas Schweizer and Robert Hudek
The aim was to investigate differences of the kinetics of the crimp and the slope grip used in rock climbing. Nine cadaver fingers were prepared and fixated with the proximal phalanx in a frame. The superficial (FDS) and deep (FDP) flexor tendons were loaded selectively and together with 40 N in the crimp grip (PIP joint flexed 90°/DIP joint hyperextended) and the slope grip position (<25° flexed/50° flexed respectively). Five different grip sizes were tested and the flexion force which was generated to the grip was measured. In the crimp grip the FDP generated more flexion force in small sized holds whereas the FDS generated more force in the larger holds. During the slope grip the FDP was more effective than the FDS. While both tendons were loaded, the flexion force was always greater during crimp grip compared with the slope grip. The FDP seems to be most important for very small holds using the crimp grip but also during slope grip holds whereas the FDS is more important for larger flat holds.