The Effects of Quadriceps Strengthening Exercise on Quadriceps Muscle Biomechanics During Locomotion in Adults with Knee Osteoarthritis

Knee Osteoarthritis (OA) is a disease characterized by knee joint deterioration and pain, while also being associated with altered knee joint mechanics and quadriceps strength deficits. Research investigating the effects of quadriceps-strengthening exercise on knee OA has shown improvements in symptoms, function, and strength, but minimal changes to joint mechanics. It is speculated that improved quadriceps muscle biomechanics are the mechanism responsible for this improvement in symptoms, though this concept is untested. The purpose of this study is to examine the effects of quadriceps strengthening exercise on quadriceps muscle biomechanics during level walking, stair ascent, and stair descent in adults with knee osteoarthritis.   Three-dimensional kinematic, ground reaction force, isokinetic strength, and WOMAC data were collected on 10 adults with uni- or bi-lateral knee OA. During the 12-week period between the testing procedures, 6 adults participated in strengthening exercise, while the other 4 adults went untrained. Quadriceps biomechanics were quantified using kinetic data collected during level walking, stair ascent, and stair descent tasks in combination with a mathematical knee model. A 2x2 repeated measures ANOVA (p<0.05) was used to analyze each symptomatic, strength, joint kinetic, and muscle biomechanics parameter.    Only the training group experienced significant improvements in pain, function, and strength (All p<0.02). At follow-up, this group climbed and descended stairs at faster velocities (Both p<0.03), exhibited greater knee extensor torque and power during level walking (Both p<0.03), experienced increased quadriceps force and work during level walking and stair ascent (All p<0.05), and exhibited increased knee compressive force during all three conditions (All p<0.03).   The results of this study reinforce the notion that quadriceps-strengthening exercise reduces pain and improves function in adults with knee OA. The data refute the study hypothesis by suggesting that quadriceps muscle biomechanics are, in fact, altered following a strengthening protocol. Study results also refute claims that reduced joint loads are the cause of pain relief by showing significant increases in knee compressive force alongside significant improvements in pain and physical function. Because of the limited number of participants used, more work is needed.  M.S

The Influence of Age at Pediatric-Onset Spinal Cord Injury and Years of Wheelchair Use on Shoulder Complex Joint Dynamics During Manual Wheelchair Propulsion

Objective To assess the association of age at pediatric-onset spinal cord injury (SCI) and years of manual wheelchair use with shoulder dynamics. Design Upper extremity kinematics and hand-rim kinetics were obtained during manual wheelchair propulsion. An inverse dynamics model computed three-dimensional acromioclavicular, sternoclavicular, and glenohumeral joint dynamics. Linear mixed effects models evaluated the association of age at injury onset and years of wheelchair use with shoulder dynamics. Setting Motion laboratory within a children\u27s hospital. Participants Seventeen manual wheelchair users (N=17; 6 female, 11 male; mean age: 17.2 years, mean age at SCI onset: 11.5 years) with pediatric-onset SCI (levels: C4-T11) and International Standards for Neurological Classification of SCI grades: A (11), B (3), C (2), and N/A (2). Interventions Not applicable. Main Outcome Measures Acromioclavicular, sternoclavicular, and glenohumeral angles and ranges of motion, and glenohumeral forces and moments. Results We observed a decrease in maximum acromioclavicular upward rotation (ß [95% confidence interval {CI}]=3.02 [0.15,5.89], P=.039) and an increase in acromioclavicular downward/upward rotation range of motion (ß [95% CI]=0.44 [0.08,0.80], P=.016) with increasing age at SCI onset. We found interactions between age at onset and years of use for maximum glenohumeral abduction (ß [95% CI]=0.16 [0.03,0.29], P=.017), acromioclavicular downward/upward rotation range of motion (ß [95% CI]=-0.05 [-0.09,-0.01], P=.008), minimum acromioclavicular upward rotation (ß [95% CI]=-0.34 [-0.64,-0.04], P=.026). A decrease in glenohumeral internal rotation moment (ß [95% CI]=-0.09 [-0.17,-0.009], P=.029) with increasing years of use was found. Conclusions Age at injury and the years of wheelchair use are associated with shoulder complex biomechanics during wheelchair propulsion. These results are noteworthy, as both age at SCI onset and years of wheelchair use are considered important factors in the incidence of shoulder pain. These results suggest that investigations of biomechanical changes over the lifespan are critical

Functional integrity of the shoulder joint and pectoralis major following subpectoral implant breast reconstruction

Subpectoral implants for breast reconstruction after mastectomy requires the surgical disinsertion of the sternocostal fiber region of the pectoralis major. This technique is associated with significant shoulder strength and range of motion deficits, but it is unknown how it affects the underlying integrity of the shoulder joint or pectoralis major. The aim of this study was to characterize the long‐term effects of this reconstruction approach on shoulder joint stiffness and pectoralis major material properties. Robot‐assisted measures of shoulder strength and stiffness and ultrasound shear wave elastography images from the pectoralis major were acquired from 14 women an average of 549 days (range: 313–795 days) post reconstruction and 14 healthy, age‐matched controls. Subpectoral implant patients were significantly weaker in shoulder adduction (p < 0.001) and exhibited lower shoulder stiffness when producing submaximal adduction torques (p = 0.004). The underlying material properties of the clavicular fiber region of the pectoralis major were altered in subpectoral implant patients, with significantly reduced shear wave velocities in the clavicular fiber region of the pectoralis major when generating adduction torques (p = 0.023). The clinical significance of these findings are that subpectoral implant patients do not fully recover shoulder strength or stability in the long‐term, despite significant recovery time, and substantial shoulder musculature left intact. The impact of these procedures extends to the remaining, intact volume of the pectoralis major. Optimization of shoulder function should be a key aspect of the post‐reconstruction standard of care. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1610–1619, 2019.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149750/1/jor24257.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149750/2/jor24257_am.pd

Age and sex influence the activation- dependent stiffness of the pectoralis major

The pectoralis major fiber regions contribute uniquely to the mobility and the stability of the shoulder complex. It is unknown how age and sex influence the stiffness of these regions during volitional contractions, but this knowledge is critical to inform clinical interventions targeting the pectoralis major. The aim of the present study was to determine if the activation- dependent stiffness of the pectoralis major fiber regions differs between the sexes and if it is altered with age. Ultrasound shear wave elastography was used to acquire shear wave velocity from the clavicular and the sternocostal fiber regions of 48 healthy participants, including 24 younger (12 males, 12 females, mean ± SD age 25 ± 4.1 years) and 24 older adults (12 males, 12 females, 55 ± 3.6 years). Participants performed vertical adduction and horizontal flexion torques in neutral and 90° externally rotated shoulder positions, and one of the two shoulder abduction positions (60° and 90°) at varying torque magnitudes (passive, 15% and 30% of maximal voluntary contraction). Separate linear mixed- effects models were run for each fiber region and shoulder position to determine if the activation- dependent stiffness differed between the sexes and was altered in older adults. Age- related alterations in stiffness during volitional contractions were observed in both fiber regions and were dependent on the task. Alterations in activation- dependent stiffness due to age were more pronounced in females than males. Additionally, females had greater stiffness than males during volitional contractions in both fiber regions. The present findings provide the first line of evidence that the activation- dependent stiffness of the pectoralis major fiber regions is influenced by sex and changes with age.Age- related alterations in the stiffness of the pectoralis major during volitional contractions were observed in both fiber regions of the muscle. These alterations in activation- dependent stiffness due to age were more pronounced in females than males.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/168528/1/joa13455_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/168528/2/joa13455.pd

Functional integrity of the shoulder joint and pectoralis major following subpectoral implant breast reconstruction

Subpectoral implants for breast reconstruction after mastectomy requires the surgical disinsertion of the sternocostal fiber region of the pectoralis major. This technique is associated with significant shoulder strength and range of motion deficits, but it is unknown how it affects the underlying integrity of the shoulder joint or pectoralis major. The aim of this study was to characterize the long‐term effects of this reconstruction approach on shoulder joint stiffness and pectoralis major material properties. Robot‐assisted measures of shoulder strength and stiffness and ultrasound shear wave elastography images from the pectoralis major were acquired from 14 women an average of 549 days (range: 313–795 days) post reconstruction and 14 healthy, age‐matched controls. Subpectoral implant patients were significantly weaker in shoulder adduction (p < 0.001) and exhibited lower shoulder stiffness when producing submaximal adduction torques (p = 0.004). The underlying material properties of the clavicular fiber region of the pectoralis major were altered in subpectoral implant patients, with significantly reduced shear wave velocities in the clavicular fiber region of the pectoralis major when generating adduction torques (p = 0.023). The clinical significance of these findings are that subpectoral implant patients do not fully recover shoulder strength or stability in the long‐term, despite significant recovery time, and substantial shoulder musculature left intact. The impact of these procedures extends to the remaining, intact volume of the pectoralis major. Optimization of shoulder function should be a key aspect of the post‐reconstruction standard of care. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1610–1619, 2019.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/149750/1/jor24257.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/149750/2/jor24257_am.pd