Morphological Differences in the Upper Trapezius Muscle Between Female Office Workers With and Without Trapezius Myalgia: Facts or Fiction?: A Cross-Sectional Study

Comparison of Shifts in Skeletal Muscle Plasticity Parameters in Horses in Three Different Muscles, in Answer to 8 Weeks of Harness Training

Training-induced follow-up of multiple muscle plasticity parameters in postural stability vs. locomotion muscles provides an integrative physiological view on shifts in the muscular metabolic machinery. It can be expected that not all muscle plasticity parameters show the same expression time profile across muscles. This knowledge is important to underpin results of metabolomic studies. Twelve non-competing Standardbred mares were subjected to standardized harness training. Muscle biopsies were taken on a non-training day before and after 8 weeks. Shifts in muscle fiber type composition and muscle fiber cross-sectional area (CSA) were compared in the m. pectoralis, the m. vastus lateralis, and the m. semitendinosus. In the m. vastus lateralis, which showed most pronounced training-induced plasticity, two additional muscle plasticity parameters (capillarization and mitochondrial density) were assessed. In the m. semitendinosus, additionally the mean minimum Feret's diameter was assessed. There was a significant difference in baseline profiles. The m. semitendinosus contained less type I and more type IIX fibers compatible with the most pronounced anaerobic profile. Though no baseline fiber type-specific and overall mean CSA differences could be detected, there was a clear post-training decrease in fiber type specific CSA, most pronounced for the m. vastus lateralis, and this was accompanied by a clear increase in capillary supply. No shifts in mitochondrial density were detected. The m. semitendinosus showed a decrease in fiber type specific CSA of type IIAX fibers and a decrease of type I fiber Feret's diameter as well as mean minimum Feret's diameter. The training-induced increased capillary supply in conjunction with a significant decrease in muscle fiber CSA suggests that the muscular machinery models itself toward an optimal smaller individual muscle fiber structure to receive and process fuels that can be swiftly delivered by the circulatory system. These results are interesting in view of the recently identified important fuel candidates such as branched-chain amino acids, aromatic amino acids, and gut microbiome-related xenobiotics, which need a rapid gut-muscle gateway to reach these fibers and are less challenging for the mitochondrial system. More research is needed with that respect. Results also show important differences between muscle groups with respect to baseline and training-specific modulation.

Foci of Segmentally Contracted Sarcomeres in Trapezius Muscle Biopsy Specimens in Myalgic and Nonmyalgic Human Subjects: Preliminary Results

OBJECTIVE

The myofascial trigger point hypothesis postulates that there are small foci of contracted sarcomeres in resting skeletal muscle. Only one example, in canine muscle, has been published previously. This study evaluated human muscle biopsies for foci of contracted sarcomeres.

SETTING

The Departments of Rehabilitation Sciences and Physiotherapy at Ghent University, Ghent, Belgium.

SUBJECTS

Biopsies from 28 women with or without trapezius myalgia were evaluated, 14 in each group.

METHODS

Muscle biopsies were obtained from regions of taut bands in the trapezius muscle and processed for light and electron microscopy and for histochemical analysis. Examination of the biopsies was blinded as to group.

RESULTS

A small number of foci of segmentally contracted sarcomeres were identified. One fusiform segmental locus involved the entire muscle fiber in tissue from a myalgic subject. Several transition zones from normal to contracted sarcomeres were found in both myalgic and nonmyalgic subjects. The distance between Z-lines in contracted sarcomeres was about 25-45% of the same distance in normal sarcomeres. Z-lines were disrupted and smeared in the contracted sarcomeres.

CONCLUSIONS

A small number of foci of segmentally contracted sarcomeres were found in relaxed trapezius muscle in human subjects, a confirmation of the only other example of spontaneous segmental contraction of sarcomeres (in a canine muscle specimen), consistent with the hypothesis of trigger point formation and with the presence of trigger point end plate noise.

Effects of Transcatheter Arterial Microembolization on Persistent Trapezius Myalgia Refractory to Conservative Treatment

PURPOSE

To evaluate the safety and efficacy of transcatheter arterial microembolization for patients with trapezius myalgia.

MATERIALS AND METHODS

We retrospectively evaluated the prospectively collected data of patients with trapezius myalgia for > 6 months who were refractory to conservative treatment and were treated by transcatheter arterial microembolization between October 2017 and January 2019. Transcatheter arterial microembolization was performed using imipenem/cilastatin on the vessels of the transverse cervical artery, suprascapular artery, and circumflex scapular artery according to the region of pain.

RESULTS

Forty-two patients were treated by transcatheter arterial microembolization and followed up for 6 months. No major adverse events occurred related to the procedures. The brief pain inventory worst pain scores significantly improved at 1, 2, 3, and 6 months after transcatheter arterial microembolization (8.6 ± 1.3 (before procedure) vs. 5.1 ± 2.9, 4.4 ± 2.9, 4.1 ± 2.8, and 3.9 ± 2.9, respectively, P < 0.001). The brief pain inventory pain interference scores, including general activity, mood, walking ability, normal work, relations with others, sleep, and enjoyment of life, also significantly decreased at 1, 2, 3, and 6 months after transcatheter arterial microembolization compared to those at baseline (all P < 0.01). The clinical success rate at 6 months after transcatheter arterial microembolization was 71.4% (95% confidence interval, 55.4-84.3%).

CONCLUSION

Transcatheter arterial microembolization is a safe and effective treatment for persistent trapezius myalgia. Further evaluation with a control group is needed to confirm the effects of transcatheter arterial microembolization.

LEVEL OF EVIDENCE

Level 4, Case Series.

Differences in the Mitochondrial and Lipid Droplet Morphology in Female Office Workers With Trapezius Myalgia, Compared With Healthy Controls: A Muscle Biopsy Study

OBJECTIVE

Trapezius myalgia or, more specifically, myofascial dysfunction of the upper trapezius mainly affects women performing jobs requiring prolonged low level activation of the muscle. This continuous low muscle load can be accompanied by a shift to a more anaerobic energy metabolism, causing pain. The aim of the study was to investigate whether morphological signs of an impaired aerobic metabolism are present in female office workers with trapezius myalgia.

DESIGN

Muscle biopsy analysis, using electron and light microscopy, was performed to compare mitochondrial and fat droplet morphology, and irregular muscle fibers, between female office workers with (n = 17) and without (n = 15) work-related trapezius myalgia.

RESULTS

The patient group showed a significantly higher mean area (P = 0.023) and proportion (P = 0.029) for the subsarcolemmal and intermyofibrillar mitochondria respectively, compared with the control group. A significantly lower mean area of subsarcolemmal lipid droplets was found in the patient group (P = 0.015), which also displayed a significantly higher proportion of lipid droplets touching the mitochondria (P = 0.035). A significantly higher amount of muscle fibers with cytochrome c oxidase-deficient areas were found in the patient group (P = 0.030).

CONCLUSIONS

The results of the present study may be indicative for an impaired oxidative metabolism in work-related trapezius myalgia. However, additional research is necessary to confirm this hypothesis.