Frontal Plane Body Posture as a Predictor of Musculoskeletal Injuries in Amateur Athletes: A Comprehensive Study of 89 Participants Over 12 Months

Introduction

Regular physical activity is crucial for maintaining good health, and numerous studies have highlighted its positive impact on overall well-being [1,2]. However, it is essential to acknowledge that physical activity also has negative aspects, such as the risk of musculoskeletal injuries [3]. Understanding the factors linked with a higher injury risk during physical activity is crucial. Some sports require specific body positions, as do certain jobs and daily activities [4]. All individuals have some body position abnormality, considered as structural asymmetry, that can lead to injury when combined with increasing musculoskeletal loads (eg, during physical activity) [5].

Moreover, extended periods of sitting can increase lower back and neck pain and lower the pain threshold of soft tissues [6]. These abnormalities can be categorized as intrinsic risk factors (related to individual characteristics like sex, age, flexibility and mobility, physical performance, and body composition) [7,8]. To date, few studies have explored the impact of postural dysfunctions on injury frequency correlations between spinal curves and functional movement screen results [9]. Notably, research in tae kwon do athletes linked ankle injuries to forward trunk inclination, while Snodgrass et al [10] associated lower limb injuries with kyphosis [11]. Retrospective analyses of soccer players indicated the premature end of a sports career due to injury as a common phenomenon [12]. Evidence suggests that postural dysfunctions may hinder proper movement patterns, as seen in hockey players with correlations between spinal curves and functional movement screen results [9,13] and in military personnel showing postural irregularities in sagittal and frontal planes [14]. However, studies on 8- to 11-year-old children [15] and young women with hyperlordosis [16] did not confirm such relationships, highlighting the need for further exploration.

Systematic studies revealed a considerable range of injury occurrences, ranging from 51% to 70%, among physically active individuals [17]. A study conducted in Poland found that 40% of physically active people reported injuries related to physical training, with a higher incidence among men (45.71%) than women (35.51%), often occurring during activities like running and jumping on uneven ground [18].

While existing research predominantly focused on military and professional athlete populations, there is a gap in understanding musculoskeletal injuries in physically active, amateur, young athletes [17,19]. To effectively prevent injuries, it is essential to identify injury risk factors [20]. Addressing this gap is crucial for public health, as physical activity-induced injuries pose significant challenges to healthcare systems [3]. Professional athletes and military personnel participate in specialized training programs, making it imperative to interpret injury risks accordingly [18,21]. Furthermore, intrinsic factors related to body posture parameters are not well explored [9,10]. The broadness of parameters and lack of indications as to which abnormality indicates an increased injury risk make them difficult to assess. A comprehensive exploration of various body composition indices and their cut-off points for injury risk is lacking, especially in the context of physically active amateurs [9,13].

Body posture measures are taken to assess health and functional state [22]. There is a consensus that body posture abnormalities are associated with many health problems. The symmetrical positioning of the scapulae conditions the proper functioning of the upper limb’s shoulder girdle. Differences in height (LSAS) and distance from the spine (LSPD) most commonly result from muscular imbalance. They can also be associated with scoliosis (PTA), hyperkyphosis, or assuming an incorrect body posture. Protraction, or the distancing of the lower angle of the scapula from the spine (LSPD), is caused, among other factors, by weakening of the rhomboid and serratus anterior muscles, while weakening of the serratus anterior muscle increases the protrusion of the scapula from the backplane. Elevation or depression of the scapula (LSAS) and asymmetry in the positioning of the acromion processes (SSA) results from changes in the tension of the levator scapulae, pectoralis minor, and rhomboid muscles. These postural dysfunctions can contribute to functional impairments manifested at various levels of the biomechanical chain, thereby hindering the proper execution of movement patterns [23]. However, few studies have considered body posture as an injury risk factor in young, physically active adults.

We performed a literature review, which raised questions regarding which methods of body posture assessment can accurately predict injury occurrence, which factors are best to use for injury risk assessment, and are there any sex-related differences in the relationship between body posture and injury risk. The present study examined various body posture parameters in the frontal plane as intrinsic risk factors for musculoskeletal injuries occurring during physical activity in 89 males and females involved in amateur sports. Specifically, we aimed to (1) investigate the diagnostic potential of these body posture parameters in relation to injuries, (2) identify the associated cut-off points for each parameter in physically active young adult males and females, and (3) assess whether potential relationships between the parameters and injuries are modified by sex.

Material and Methods

ETHICS STATEMENT:

The Senate Research Ethics Committee at Wrocław University Health and Sport Science approved the study following consideration of the institutional ethics requirements for human experiments under the Helsinki Declaration, consent number 16/2018. The approval was received based on the resolution of the Senate of the University of Physical Education in Wrocław dated December 20, 2002, regarding the establishment of the Senate Committee on Ethics in Scientific Research and the resolution of November 4, 2003, governing the procedures, as well as by Article 27 of the Act of June 6, 1997, the Code of Ethics (Journal of Laws of 1997, No. 553, as amended), and the principles outlined in “Good Practices in Science: A Collection of Principles and Guidelines” by the Ethics Committee in Science of the Polish Academy of Sciences from 2001.

All subjects were required to provide written consent before participating in this study, and they were informed in detail about the purpose, type, and method of conducting the research and participation conditions. They were aware of study demands, considering anthropometric measurements (body weight and height), body posture assessment, and an injury questionnaire. Participants were allowed to withdraw from the research at any stage without providing any reasons. The faculty and staff of the University of Sport and Health Sciences in Wrocław conducted the surveys. There are no conflicts of interest to declare.

STUDY PARTICIPANTS:

Our research included 89 young active adults ages 19–23 years, all of whom had at least 4 years of experience in sports and participated in training sessions a minimum of 3 times weekly. They were recruited electronically via the Internet using application forms sent to local sports clubs and universities of sports sciences. The 41 males included had an average height of 182.00±5.00 mm, weight of 79.42±8.20 kg, and a body mass index (BMI) of 23.90±2.00 kg/m², and 36.59% reported having injuries within the last year. The 48 female participants had an average height of 167.00±6.00 mm, weight of 58.96±7.75 kg, and a BMI of 20.91±2.13 kg/m², with 41.06% reporting injuries. Sports activities among participants included soccer, futsal, handball, basketball, and rugby. Participants with current injuries (n=9) at the start of the study were not included.

MANAGEMENT AND FILLING OF MISSING DATA:

The study encountered no missing data in anthropometric measurements or injury questionnaires. However, data on body posture were missing for 7 participants. To maintain participant numbers for analysis, requiring complete data sets, multiple imputations were applied to fill in missing values, assuming data were missing completely at random. This process indicated no pattern to the missing data relative to other data points. The imputations were performed using the R programming language in RStudio software version 2023.06.0+421. Heymans et al [24] and Austin et al [25] provided a detailed procedure for filling in missing data.

ANTHROPOMETRIC MEASUREMENTS:

The participant’s heights and weights were measured using a SECA 764 scale (SECA GMBH & CO., Hamburg, Germany). These measurements were used to calculate BMI=weight in kilograms/(height in meters)2. Anthropometric measurements adhered to the guidelines outlined by the International Society for the Advancement of Kinanthropometry (ISAK), ensuring standardized procedures [26]. Skilled specialists conducted each measurement individually in a private setting.

INJURY DATA COLLECTION:

Our research utilized the Injury History Questionnaire (IHQ) to collect data on the participant’s injuries [21]. This tool is recognized for its reliability in research settings. The questionnaire was completed under supervision to clarify any questions or concerns. An injury was identified as any problem in the musculoskeletal system during exercise that resulted in pain, discomfort, and either temporary restriction or complete cessation of the activity. The relevant definition was provided in the questionnaire form. The questionnaire specifically asked about injuries in various body parts (head and neck, trunk, and upper and lower limbs) over the previous 12 months. The questionnaire also included a table where responders must fill in appropriate places for body parts with several injuries. The assessment of IHQ reliability was carried out 1 week following participants’ completion of the IHQ. A randomly selected group of 56 individuals participated in a repeat survey. The reliability of the IHQ was determined through the calculation of Cronbach’s alpha coefficient, yielding a high reliability level of 0.836 [27].

BODY POSTURE MEASUREMENTS:

The posture was examined using the photogrammetric method utilizing a Computer-Aided System for Posture Assessment (CQ Electronic System, Poland). The process and device’s reliability and standardization were affirmed through the protocol outlined by Mrozowiak [28], which was rigorously implemented and validated. Before conducting examinations of the backs of the subjects, standing barefoot in a relaxed position with head positioned in the Frankfurt plane, the following bony points were marked with a black marker: spinous processes of the vertebrae from C7 to S1, inferior angles of the scapulae, acromion processes, and posterior superior iliac spines. Then, the subjects were instructed to stand with their backs to the recording camera in a strictly defined position: standing naturally, silhouette perpendicular to the camera, heels aligned in 1 line, and head in the Frankfurt plane position. Posture image recording lasted about 5 s to avoid fatigue of postural muscles. From several images, 1 shot was selected that corresponded to the correct alignment of the subject. Based on the recorded image, the computer program calculated parameters describing body posture and a graphical representation of the results. Measurements were taken under strictly defined conditions: a constant distance of 2.6 m from the camera, a completely darkened room, fixed optical system parameters, and a precisely leveled camera. The analysis of the recorded parameters enabled us to assess the magnitude of the following frontal plane asymmetries:

All values were measured in millimeters and represent the differences in the location of selected body posture parameters. Values further from zero indicate greater asymmetry in the position of bone points.

DATA ANALYSIS:

The Shapiro-Wilk test was conducted to assess normality of continuous data distribution. If the Shapiro-Wilk test yields statistical significance (P<0.05), it indicates a departure from Gaussian distribution. Data that met the assumption of normal distribution were subjected to parametric tests. Only the data on injuries did not meet the normality assumption. Therefore, an appropriate approach (non-parametric) was introduced. Descriptive statistics of anthropometric variables and body posture measurements were introduced as means, standard deviations, and 95% confidence intervals (95% CI). The independent samples t test was used to assess differences in anthropometrical and body posture measurements between sexes. Categorical variables (eg, sex, injuries) are presented as numbers and percentages. Descriptive statistics for percentages (SD, SE, 95% CI) were calculated. Chi-square tests with effect size statistics and odds ratios (ORs) were used to assess the relationship between categorical variables. The effectiveness of various body posture parameters (SSA, LSAS, LSPD, PSIS, and PTA) in distinguishing between injured and non-injured participants was evaluated using the receiver operating characteristic (ROC) technique. The results are graphically displayed as ROC curves, illustrating the sensitivity (the percentage of actual positives accurately detected by the test) versus specificity (the percentage of actual negatives precisely identified by the test) at different threshold levels. The Youden index was calculated from the formula: J=(sensitivity+specificity-1).

The area under the curve (AUC) is used to determine the model’s fit and validity, and the standard error (SE) was computed [29]. All body parameters were compared using the DeLong method [30]. Similarly, sex differences in all models were assessed.

A P value of less than 0.05 was deemed to indicate statistical significance. These calculations were performed using Statistica 13.3 (StatSoft Poland 2023, Cracow, Poland) and RStudio ver. 2023.06.1+524 (accessed: 09 July 2023).

Results

INJURY PREVALENCE:

Of 89 participants, 51 (57.30%) had a musculoskeletal injury. Among the 41 males, 26 (63.41%) had musculoskeletal injuries, while among the 48 females, 25 (52.08%) had at least 1 injury during the year before filling out the questionnaire. The remaining participants (males: n=15, 39.69%; females: n=23, 47.92%) did not have any musculoskeletal injuries. The chi-squared test results indicated no significant differences in the proportions of musculoskeletal injuries between males and females (χ² Yates=0.743, P=0.389, ϕ= −0.114, OR=0.63, 95% CI [0.27–1.47]). The t test did not reveal statistically significant differences between injured and non-injured individuals due to body morphology and the analyzed body posture parameters (P>0.05). Therefore, further analysis was performed on the total sample.

Table 1 presents descriptive statistics of the anthropometrical and body posture measurements of the males and females. Results showed statistically significant differences only in age (males were older, P=0.008) and anthropometrical measurements (all measurements: body height, body weight, and BMI were higher in males; P<0.001). However, there were no significant differences in body posture measurements (P>0.05).

CUT-OFF POINTS FOR BODY POSTURE MEASUREMENTS ACCORDING TO INCREASED INJURY RISK:

The diagnostic precision of threshold values for assessing injury risks exceeded chance levels (AUC >0.5) for all body posture metrics except LSAS and PTA. Specifically, LSPD was statistically significant (P=0.028) for predicting injuries, with a cut-off point value of >6.3 (Table 2, Figure 1).

When comparing the differences between AUC values, LSPD showed significant differences compared to LSAS and PTA (P<0.05) (Table 3).

The cut-off point values characterized by the highest sensitivity and specificity for SSA, LSAS, and PSIS were >2, while for the PTA, they were >3. The highest value was observed for LSPD, and it was >6.3 (Table 2). There were no statistically significant differences in the performance of the body posture parameters in detecting injuries between males and females (Table 4).

Discussion

Promoting physical activity is essential, and a key objective is preventing injuries. To achieve this, it is crucial to identify the factors that contribute to injuries and determine the most suitable injury prevention method. A multifactorial approach should be adopted, considering various factors that can lead to injuries. Identifying factors contributing to injuries is vital in selecting the appropriate method of injury prevention.

It has been suggested that asymmetries in the frontal plane of the body posture can increase the risk of injury in amateur sports, independently of sex. The present study found that the difference in the distance between the lower angles of the scapula from the spine (LSPD) was statistically significant in predicting injuries. Among the frontal plane asymmetries tested, LSPD was the only intrinsic risk factor for predicting musculoskeletal injuries in sports amateurs of both sexes. This suggests that the alignment of the shoulder girdle is an integral part of posture mechanisms. A stable, symmetric trunk with balanced spinal curvatures is necessary to perform proper movements in the lower and upper extremities during different activities. Indeed, correct body posture and consistent, high-quality movement patterns have been associated with a reduced incidence of injuries [13,31]. Body posture is also an important indicator of functional state [33] and may be linked to injury risk [34]. Therefore, this factor could be modified [4,35].

The position of the scapula alters the thoracic and cervical spinal curvatures. Patients with spinal curvature disorders (kyphosis, lordosis, scoliosis, and unspecified) have a higher risk of unintentional injuries and injury diagnoses such as fractures, dislocations, open wounds, superficial injuries/contusions, and crushing and injuries to nerves and the spinal cord [12,36]. Our study did not assess spinal curvatures, so the incidence of injuries depending on spinal shape could not be discussed. Asymmetries of frontal plane posture occurred at similar levels between females and males, and the AUC differences were insignificant. This means that sex was not an essential factor in injuries for tested athletes.

Probabilities of the differences between AUC and body posture stated that LSAS-LSPD and LSPD-PTA revealed significant differences. It can be interpreted that asymmetry in the scapula’s position was influenced by deviation of the spinous processes, probably of the thoracic spine, or imbalance between thoracic muscles: serratus anterior, rhomboids, and spinal erector. The alignment of the spine is critical for maintaining correct posture in space. Postural control during standing or sitting involves active sensory processing, with a constant mapping of perception to action, so that the postural system can calculate the body’s position. Sensory inputs are critical to muscle tone in a standing position, called postural tone [37]. It is influenced by visual, vestibular, and somatosensory inputs. Postural tone in the trunk segment is the critical element for control of normal postural stability in an erect position. There is evidence that core stability exercises can improve this mechanism [38], which was more effective than general exercise for decreasing pain and increasing back-specific functional status in patients with low back pain [39]. Preventive active strategies focused on the trunk and shoulder should be used in athletes.

Interestingly, other intrinsic risk factors, like body composition, relative fat mass, fat mass, bone mineral content, fat-free mass, and bone mineral density, were non-significant in military students [19]. Few studies have considered lower limb tissue composition as an injury risk factor, especially asymmetry, which has been indicated as an intrinsic risk factor [40,41]. Most studies have used unspecific tools to measure anthropometric variables. However, the present study used photogrammetry to measure surface asymmetry, with good repeatability.

Analysis of injury frequency indicated that most injuries were localized in the lower extremity (38%) and the trunk and upper extremity (22.48%). Concerning the anatomical body parts affected, similar to our study, many studies have found a higher prevalence of injuries in the lower limbs [17,19].

Our study has some limitations. First, only amateur athletes engaged in different activities were examined, which may limit the generalizability of the findings. Additionally, the photogrammetric method used to assess symmetry posture parameters was effective and safe but only measured in the frontal plane. Although the technique provided values as close as possible to the Cobb radiographic measurements, it is essential to note that it is a surface measure only. As this was a cross-sectional study, it was impossible to establish a causal relationship between different injuries and body posture parameters. Future studies should focus on specific common physical activities, such as outdoor and indoor sports, to determine which activities pose the most significant concern for young athletes in predicting injury risks. The assessment of spine curvatures as an intrinsic risk factor for injury will be a crucial area of investigation.

Conclusions

The present study suggests that the position of lower angles of the scapula from the spine has the highest predictive potential for musculoskeletal injuries compared to other body posture frontal parameters. This is a valuable and sensitive indicator of injury risk in a group of young, physically active adults.

The primary strength of the current study is the potential utility of cut-off points (particularly for LSPD) for use in the fields of physical activity instructors or physiotherapists. Using ROC-generated cut-off points (especially high sensitivity) may support preventive measures.

This study suggests that body posture parameters can contribute to injury risk as an intrinsic factor, independent of sex. Athletes should use active preventive strategies focused on the trunk and shoulder.