From the Guidelines
The trapezius muscle difference can be addressed by incorporating unilateral exercises that target the smaller side, while maintaining some work on the stronger side, to prevent postural problems and increased injury risk. When considering the trapezius gross muscle difference, it is essential to understand the anatomy and function of the accessory nerve (CN XI), which supplies portions of the sternocleidomastoid muscle and the upper portion of the trapezius muscle, as discussed in the study by 1. The key factors to consider when addressing trapezius muscle difference include:
- Uneven use patterns, such as consistently carrying bags on one shoulder or favoring your dominant side during workouts
- Incorporating unilateral exercises, such as single-arm shrugs, one-sided rows, and isolated trapezius raises, to target the smaller side
- Maintaining proper form during all exercises and considering working with a physical therapist if the asymmetry is significant or causing pain
- Potential underlying conditions, such as torticollis, nerve damage, or scoliosis, which would require medical evaluation, as accessory nerve palsy can be clinically manifested by weakness and atrophy of the trapezius muscle, causing decreased shoulder abduction, shoulder pain, cosmetic disfigureation, and disability, as noted in the study by 1. Regular stretching, massage, and attention to daily posture habits can also help correct these differences over time, ultimately improving morbidity, mortality, and quality of life.
From the Research
Trapezius Muscle Gross Difference
The trapezius muscle is a large, triangular muscle that extends from the base of the skull to the lower back, playing a crucial role in movements of the shoulder and scapula. Studies have investigated the differences in the trapezius muscle, particularly in relation to its innervation, function, and response to various treatments.
- The main innervation of the trapezius muscle is provided by the spinal accessory nerve, with contributions from cervical plexus roots 2.
- The trapezius muscle can be divided into three portions: upper, middle, and lower. Research has shown that the middle and lower portions of the trapezius muscle are more susceptible to morphological and functional impairment after spinal accessory nerve transfer 2.
- Physical examination alone may not be sufficient to determine the residual functionality of the trapezius muscle. Magnetic resonance imaging (MRI) and electromyography (EMG) are useful tools to assess both morphological involvement and nerve conduction impairment of the trapezius muscle 2.
- Botulinum toxin type A (Botox) injection has been used to relieve pain in myofascial trigger points of the upper trapezius muscle. While it may not be more effective than placebo in reducing pain, it can increase the pressure pain threshold 3.
- Surgical treatment of trapezius palsy, resulting from injury to the spinal accessory nerve, can improve functional outcomes and quality of life. The Eden-Lange muscle transfer procedure has been shown to have high patient satisfaction rates and low complication rates 4.
- Exercises that target the trapezius and serratus anterior muscles, such as the unilateral shoulder shrug and arm raise overhead, can elicit high levels of EMG activity in these muscles 5.
- Quantitative MRI with T2 mapping can be used to assess myofascial trigger points in the upper trapezius muscles of patients with migraine, providing a more objective measure of muscle involvement 6.