Search

Background: Decreased muscle volume and increased muscle-associated adipose tissue (MAAT, sum of intra and inter-muscular adipose tissue) of the foot intrinsic muscle compartment are associated with deformity, decreased function, and increased risk of ulceration and amputation in those with diabetic peripheral neuropathy (DPN)., Research Question: What is the muscle quality (normal, abnormal muscle, and adipose volumes) of the DPN foot intrinsic compartment, how does it change over time, and is muscle quality related to gait and foot function?, Methods: Computed tomography was performed on the intrinsic foot muscle compartment of 45 subjects with DPN (mean age: 67.2 ± 6.4 years) at baseline and 3.6 years. Images were processed to obtain volumes of MAAT, highly abnormal, mildly abnormal, and normal muscle. For each category, annual rates of change were calculated. Paired t-tests compared baseline and follow-up. Foot function during gait was assessed using 3D motion analysis and the Foot and Ankle Ability Measure. Correlations between muscle compartment and foot function during gait were analyzed using Pearson's correlations., Results: Total muscle volume decreased, driven by a loss of normal muscle and mildly abnormal muscle (p<0.05). MAAT and the adipose-muscle ratio increased. At baseline, 51.5% of the compartment was abnormal muscle or MAAT, increasing to 55.0% at follow-up. Decreased total muscle volume correlated with greater midfoot collapse during gait (r = -0.40, p = 0.02). Greater volumes of highly abnormal muscle correlated with a lower FAAM score (r = -0.33, p = 0.03)., Significance: Muscle volume loss may progress in parallel with MAAT accumulation, impacting contractile performance in individuals with DPN. Only 48.5% of the DPN intrinsic foot muscle compartment consists of normal muscle and greater abnormal muscle is associated with worse foot function. These changes identify an important target for rehabilitative intervention to slow or prevent muscle deterioration and poor foot outcomes., Competing Interests: Declaration of Competing Interest None., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Background: Electromyography signal amplitude is influenced by a variety of factors. Normalization strategies aimed at decreasing signal variability include using peak electromyography signal during a maximum voluntary contraction and peak-to-peak M-wave amplitude. However, whether these normalization methods are comparable has not been investigated in injured populations. This study investigated the relationship between peak signal during maximum voluntary contraction and M-wave amplitude in individuals with a unilateral Achilles tendon rupture. Secondarily, we observed whether the two normalizations strategies would yield similar results when evaluating between limb differences in muscle activity during a jump task., Methods: Eleven individuals 1-3 years after a unilateral Achilles tendon rupture were included in this study. Surface electromyography was used on the medial and lateral gastrocnemii bilaterally. Peak maximum voluntary contraction, M-wave amplitude, and electromyography during a jumping task were collected., Findings: A strong relationship was observed between peak maximum voluntary contraction and M-wave amplitude on the uninjured (r = 0.71-0.88, P < 0.05) but not on the ruptured side (r = 0.41-0.44, P > 0.05). The two normalization techniques did not produce different results when comparing the uninjured and ruptured sides., Interpretation: The findings of this study suggest that M-wave normalization yields similar results as peak maximum voluntary contraction-normalized electromyography in uninjured conditions. M-wave normalization may be a useful strategy in an injured population where a maximal muscle contraction is unsafe or impaired., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Background: Orthopaedic boots with wedging are commonly used in the treatment of individuals with Achilles tendon rupture to immobilize the foot in plantar flexion and approximate tendon ends., Research Question: To describe changes in muscle activity of the triceps surae and gait mechanics with the use of wedges in an orthopaedic boot immediately and after an accommodation period., Methods: Muscle activity of the triceps surae and gait parameters (vertical ground reaction force, knee extension power, gait speed) were collected using surface electromyography and motion capture in 12 healthy individuals. Participants walked in an instrumented orthopaedic boot with 0, 3, and 5 wedges tested in random order. Participants were provided a one hour accommodation period where time spent walking was collected. This was followed by a repeat assessment of triceps surae activity and gait., Results: Peak and integrated EMG in the medial gastrocnemius (p = 0.001, p < 0.001) and soleus (p = 0.010, p < 0.001) significantly decreased with increasing number of wedges. Peak and integrated EMG had a slight but non-significant decrease with increasing number of wedges in the lateral gastrocnemius (p = 0.151, p = 0.077). Vertical ground reaction force decreased (p = 0.019) and peak knee extension power increased (p = 0.003) with increasing number of wedges. There were no statistically significant differences in gait speed with wedges (p = 0.450). There were no significant changes in EMG or gait parameters from pre- to post-accommodation period., Significance: A combination of factors yield decreased triceps surae activity in individuals wearing an orthopaedic boot with wedges - decreasing loading on the immobilized limb and shifting power generation proximally., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Achilles tendon rupture leads to long term plantar flexor deficits. The purpose of this study was to describe changes in jumping biomechanics along with triceps surae structure and activation in individuals after Achilles repair. Eleven individuals 1-3 years following Achilles repair and 10 healthy controls were included. Kinetics and kinematics, analyzed using a constituent lower extremity work (CLEW) approach, and muscle activity using surface electromyography (EMG) were collected during a unilateral hopping task. Triceps surae myotendinous structure was assessed using ultrasound imaging. There were no differences in jump height, absolute limb work, or cost of transport between groups. During takeoff, the knee did more (p < 0.001) and ankle did less concentric work (p < 0.001), and lateral gastrocnemius rate of rise was higher (p = 0.02) on the ruptured side. During landing, the knee did more eccentric work (p = 0.033) and lateral gastrocnemius (p = 0.003) and soleus (p = 0.02) activation amplitude prior to landing was higher on the ruptured side. Individuals after Achilles tendon repair shift work toward the knee and alter muscle recruitment. Differences in lateral gastrocnemius activity may indicate that it is well-situated to generate power during takeoff and assist in landing with the soleus. The lack of change in muscle activity and decreased cross sectional area of the medial gastrocnemius may suggest that this muscle atrophies and does not accommodate to the hopping task. Clinical Significance: Proximal lower extremity strengthening along with emphasizing medial gastrocnemius and soleus activation during the recovery of patients with Achilles tendon repair may be rehabilitative targets for improved jumping performance. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res., (© 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.)