1.    Introduction
Improper postures maintained during prolonged work and job assignments can result in musculoskeletal disorders (1). Muscle imbalance can yield serious and well-documented consequences in the body (2). Upper crossed syndrome manifests in the neck and shoulder girdle (4), characterized by the involvement of the skeletal-muscular system. Primarily, the posterior upper and anterior muscles of the neck region, classified as tonic muscles, become shortened, while the anterior deep muscles of the cervical spine and the lower back of the shoulder girdle, predominantly phasic muscles, are inhibited, stretched, and weakened. Notable postural changes associated with upper crossed syndrome include forward head posture, forward shoulder posture, and dorsal kyphosis (5). Individuals with this syndrome often experience difficulty breathing due to increased activity of accessory respiratory muscles, along with the potential development of temporomandibular joint osteoarthritis and chronic neck pain (4, 6, 7). There have been several documented cases of temporomandibular joint arthrosis resulting from complications of forward head posture and mechanical head pains (4).
Historically, various methods have been employed to correct this syndrome. Previous approaches involved applying different stretching and strength training techniques to address forward head posture, forward shoulder posture, and kyphosis individually, while the concurrent presence of these three anomalies signifies the presence of upper crossed syndrome. Upper crossed syndrome may coincide with abnormal thoracic kyphosis and alterations in glenohumeral joint biomechanics, contributing to shoulder and chest discomfort (9). Given the significance of research in this area and the reported positive outcomes of rehabilitation exercises, it is imperative to gather comprehensive information regarding the effects of each approach. Therefore, the objective of the present study is to review the impact of various exercise protocols on the improvement of upper crossed syndrome.
2.    Methods
The present study constituted a comprehensive library and systematic review. The search for articles, conducted in both Persian and English, spanned from the beginning of December 2011 to the beginning of April 2024. This search encompassed various databases, including WOS, Science Direct, SID, Magiran, Scopus, PubMed, ISC, and Google Scholar. The selected studies comprised original research, review articles, and clinical trials. Ultimately, 10 articles focusing on different exercise protocols for individuals with upper crossed syndrome were scrutinized. These studies were categorized into two distinct groups, each detailed in separate tables: studies investigating various exercise protocols aimed at improving posture in individuals afflicted with upper crossed syndrome, and studies focusing on enhancing dynamic and static balance in individuals with upper crossed syndrome.
3.    Results
In the present study, out of the initial 74 articles retrieved through keyword search, only 10 articles met the inclusion criteria and were subsequently analyzed. Of these, 60% of the articles focused on investigating the effect of exercise protocols on improving posture in individuals suffering from upper crossed syndrome, as depicted in Table 1. Meanwhile, 40% of the articles explored the impact of various exercise protocols on enhancing dynamic and static balance in individuals with upper crossed syndrome, as presented in Table No. 2. In terms of gender distribution among the selected articles, 50% of the studies focused on female participants, 40% on male participants, and 10% included both genders. The duration of the training protocols across the studies ranged from 3 to 10 weeks, with the shortest study implementing a 3-week training protocol and the longest study employing a 10-week training protocol.

4.    Conclusion
The upper crossed syndrome denotes an abnormal body position characterized by altered muscle activity patterns in the neck and trunk muscles, leading to changes in movement patterns in the shoulders, and deviations in body posture such as forward head and shoulder posture, along with increased thoracic kyphosis. These alterations can result in various musculoskeletal complications affecting the head, neck, shoulders, and spine. In terms of the effectiveness of the current research, it aligns with previous studies conducted by Katzman (24), Katzman (25), a scientist and close associate of Manzari (26), Pawloski et al. (27), and Katzman (28). The findings of a study comparing the effects of an eight-week shoulder belt exercise program, pelvic belt exercise program, and a combination exercise program on the balance of individuals with upper crossed syndrome revealed improvement in the balance of all three exercise groups following participation in the corrective program. Moreover, the holistic corrective exercises were found to enhance balance more effectively than the positional group. The study also demonstrated improvement in balance as a result of shoulder girdle corrective exercises. Consistent with these findings, Ahmadi et al. (2018) demonstrated that a comprehensive corrective exercise program in a water environment improved the balance of individuals with upper crossed syndrome (39), while Mirafazl et al. confirmed the kinesiological alignment of the spine in individuals with kyphosis (40).
Regarding the mechanism of central stability exercises, strengthening the muscles in this area enhances neuromuscular control and reduces displacement of the center of gravity outside the support surface, thereby minimizing fluctuations and improving balance. Central stability exercises rectify neuromuscular system deficits, optimizing arthrokinematics in the lumbopelvic complex during functional chain movements, enhancing both optimal acceleration and deceleration, and ensuring optimal muscular balance, thus providing proximal stability for effective lower limb movements. However, the results of research on differences between groups during 10-second balance tests with the right and left legs did not reveal any significant differences. This finding underscores the role of sensory input from body sensory receptors, vision, and the vestibular system in balance control. Information regarding the position and movement of various body parts relative to each other, as well as the level of support and tension in relevant muscles, is conveyed by sensory receptors. Given that maintaining balance on one leg necessitates reliance on ankle, thigh, and associated muscle strategies, their role in balance maintenance is pivotal.
In summary, the present review study underscores the significant impact of various exercise protocols in ameliorating complications associated with upper crossed syndrome. Additionally, these exercise protocols alleviate pain, enhance movement, and improve the performance of affected individuals.

Ethical Considerations
Compliance with ethical guidelines
There were no ethical considerations to be addressed in this research.
Funding
This research did not receive any grants from funding agencies in the public, commercial, or non-profit sectors.
Authors' contributions
All authors contributed equally to preparing the article.
Conflicts of interest
The authors declared no conflict of interest.