Introduction

Prolonged inappropriate posture can lead to widespread adverse adaptations in joints and soft tissues over time, including muscle shortening and stiffening on one side, elongation, and weakness on the opposite side, resulting in abnormalities and muscle imbalance [ 1 , 2 ]. According to the muscle imbalance theory, derived from Janda’s approach, three main patterns of imbalance are classified: upper cross syndrome (UCS), lower cross syndrome (LCS), and layer syndrome (LS). LCS is a muscle imbalance pattern characterized by a cross-imbalance in the lumbar and hip muscle segments; it involves stiffness in the lumbar extensors and hip flexors, along with weakness in the hip extensors and trunk flexors. This syndrome contributes to significant issues such as joint function disorder, anterior pelvic tilt, increased lumbar lordosis curve, tibial lateral rotation, and knee hyperextension in the affected individual’s posture [ 3 ]. Muscle imbalances can sometimes impair postural control and contribute to structural abnormalities. Vladimir Janda highlighted the interconnection between the nervous, muscular, and skeletal systems, suggesting that defects in any joint or muscle group can affect the function and quality of other muscles and joints [ 2 , 4 ]. Changes or disorders in one area’s muscles and joints can trigger chain reactions impacting other body parts. According to scientific literature, these chain reactions in posture occur across three systems—articular, muscular, and neural. These systems interact closely, and changes in one chain can disrupt another and vice versa [ 5 , 6 ].

Training programs that integrate all body segments and enhance their coordinated function are essential for addressing musculoskeletal abnormalities. Furthermore, the effect of these abnormalities on an individual’s motor function and balance should not be underestimated. Among such holistic training methods, the dynamic neuromuscular stabilization (DNS) technique has gained recognition in sports rehabilitation. DNS emphasizes not only muscular strength but also the involvement of the nervous system, offering a comprehensive approach to rehabilitation [ 7 ].

Dynamic Neuromuscular Stabilization (DNS) therapy accurately assesses the quality of stability or movement restoration through a spine integration system incorporating specific exercises based on the ideal musculoskeletal position. These exercises follow Janda’s chain reaction principles, inspired by the neuromuscular development observed in healthy infants. They aim to re-stimulate neuromuscular growth and enhance balance and motor function, which can benefit athletes.

The fundamental techniques in DNS therapy include core stabilization and control training, limb pattern training (both with and against limb movement for forward motion and support), evolutionary postural movement models for positional stabilization, and attention to muscle chain involvement. Additionally, DNS emphasizes postural function alignment with movement force, stability training alongside breathing techniques, maintaining spinal stability, and advancing movements from simple to complex without pathological patterns. Exercises begin after patients receive awareness training from healthcare providers [ 7 ].

Yi Lin Lim investigated the effects of DNS training on postural control and lumbar spine flexion in individuals with nonspecific chronic low back pain. The findings indicated that DNS exercises improved patients’ balance, highlighting the need for further studies on DNS applications in physiotherapy settings [ 8 ].

Movement screening tests are valuable for evaluating general performance and various motor and functional capabilities. These tests serve three main objectives: (1) dynamic evaluation of the kinematic chain, (2) detection of body alignment, and (3) identification of weak movement patterns [ 9 ]. Movement screening tests assess an individual’s susceptibility to injury, inefficiencies, and weaknesses within the kinematic chain. This, in turn, allows for developing effective exercise programs to enhance motor abilities. The Functional Movement Screening (FMS) test specifically challenges an individual’s capacity to perform movement patterns that involve proprioception, coordination, range of motion, muscle strength, balance, and flexibility [ 10 , 11 ].

Based on the principles underlying DNS exercises and their potential effectiveness for Lower Cross Syndrome (LCS), neuromuscular training appears to be a promising intervention for patients with this disorder. However, no studies to date have examined the impact of this type of neuromuscular training on postural control and movement function, specifically in athletes with LCS. Therefore, this study aimed to evaluate whether DNS training could improve postural control and motor function as measured by the Functional Movement Screening (FMS) test in female athletes with LCS.

Methods

This quasi-experimental study employed a pre-test and post-test design. The sample comprised 30 female athletes aged 20–30 years with Lower Cross Syndrome (LCS) from Mashhad, who were purposefully and randomly divided into control and experimental groups based on inclusion and exclusion criteria. Ethical considerations were followed per the Ethics Committee guidelines of Shahroud University (IR.SHAHROODUT. REC.1402.032). Postural control was evaluated using the Y-balance test, and functional movement was assessed through the Functional Movement Screening (FMS) test. Inclusion criteria included: diagnosis of LCS syndrome, lumbar lordosis above 46.92 degrees, anterior pelvic tilt above 5 degrees, a minimum of three years of exercise experience, regular exercise (1-4 days per week) in both groups, voluntary participation, completion of an individual consent form, and adherence to health protocols for COVID-19 prevention [ 12 , 13 ]. Exclusion criteria encompassed experiencing pain in the lower back or lower limbs, presence of a lumbar disc condition, pain during exercises, failure to complete the training program, irregular attendance, and failure to maintain the required time interval for sessions due to COVID-19 concerns.

Tools

Evaluating LCS: The selected indices for assessing LCS complications were lumbar hyperlordosis angle and anterior pelvic tilt. A flexible ruler [ 14 ] measured the lordosis angle, while a tilt gauge [ 15 ] assessed the pelvic tilt angle. For lordosis measurement, participants positioned themselves in the designated area for spinal arch assessment. The evaluator identified and marked the T12 and S2 spinous processes using palpation. The flexible ruler was placed between these marked points, with uniform pressure applied to ensure no space between the ruler and the skin. Without altering the arc, the evaluator transferred the ruler’s curvature onto A3 paper by tracing the marked points. A straight line (labeled “I”) was drawn connecting these points, and a perpendicular line from the deepest part of the arc was measured as the width (H). The lumbar curvature angle (Ө) was calculated using the formula: Ө=4Arctan(2H/L) [ 14 , 16 ].

For pelvic angle measurement, participants stood on a flat surface, placing one hand on the posterior superior iliac spine (PSIS) and the other on the anterior superior iliac spine (ASIS). Once aligned, the degree was read directly (Figure 1) [ 15 , 17 ].

Figure 1. Y-balance test (left) and scoring method (right)

Y-Balance Test: This test was used to evaluate dynamic balance. Participants stood barefoot, positioning one foot at the center of the Y-board with the other foot adjacent to it. Maintaining balance on one foot, participants extended the free foot forward and diagonally backward in both the internal and external directions (Figure 3.3). The reach distance from the center was measured in centimeters. Each direction was tested three times. Before starting, the lower limb length was measured [ 18 ]. The balance test score in each direction was calculated individually using the following formula:

Functional Movement Screening (FMS) tests: The FMS test results are categorized into three scoring levels:

1. Score of 3: The task is performed correctly without errors or compensatory movements.

2. Score of 2: The task is performed correctly but with compensatory movements.

3. Score of 1: The task is completed with difficulty

and requires compensatory movements.

If the subject experiences pain during any task or clearing test, no points are awarded for that movement. Consequently, a subject could receive a final score of zero if pain is reported in each movement test or a maximum score of 21 if they achieve a score of three on every movement test [ 11 , 19 ].

Procedure

After visiting sports clubs in Mashhad, athletes with visible signs of anterior pelvic tilt and increased lumbar lordosis were identified. Those meeting the selection criteria who volunteered to participate were informed about the research process. Following confirmation of eligibility for Lower Crossed Syndrome (LCS) and other criteria, participants received a detailed explanation of the study’s purpose and the DNS training protocol. They were then asked to complete a consent form confirming their willingness to participate, which allowed the research process to begin as scheduled.

Initial assessments were performed using a flexible ruler and tilt gauge, and participants meeting the criteria for lordosis and anterior pelvic tilt were designated as research subjects. Participants completed a personal information questionnaire detailing age, height, weight, lower limb length, and sports activity history. Thirty athletes were randomly assigned to either the control or experimental group. Before implementing the training protocol, Y-balance and FMS tests were administered to both groups to establish baseline (pre-test) data.

The experimental group then completed an eight-week training protocol with three sessions per week, held either at participating clubs or at home for those who could not attend in person. This study occurred in Mashhad in the summer of 2020, during the COVID-19 pandemic, and health precautions were implemented to minimize virus transmission during tests and training sessions. Each session allowed up to four participants to train over a two- and-a-half-hour period. After the eight-week program, the Y-balance and FMS tests were re-administered as a post-test, with the results recorded.

Statistical Method

Data were analyzed using SPSS version 22. Descriptive and inferential statistical analyses were conducted. The Shapiro-Wilk test was used to test data normality. Assuming a normal distribution, a paired t-test assessed within-group effects, while ANCOVA evaluated between- group effects. For non-normally distributed data, the Wilcoxon test was applied (P ≤ 0.05).

Results

This section details the demographic and physical characteristics of the subjects, including height, weight, age, lordosis angle, anterior pelvic tilt, body mass index (BMI), and leg length. Table 1 summarizes these characteristics along with the results of the group homogeneity analysis.

The Shapiro-Wilk test indicated that the FMS test subscales exhibited a non-normal distribution (P<0.05). Consequently, the Wilcoxon test, with a 95% significance level and P≤0.05, was applied to assess the impact of DNS training on FMS subscales. The test confirmed normal distribution for the FMS test’s total score and the anterior, internal posterior, external posterior, and total Y-balance test scores (P<0.05). To examine the effect of DNS exercises on the Y-balance variable between the two groups (control and experimental), ANCOVA was conducted, and a paired t-test was used within each group at a 95% significance level (P≤0.05).

According to the Wilcoxon test results shown in Table 2, there was a statistically significant difference in the mean test scores for Deep Squat (P=0.014), Shoulder Mobility (P=0.003), In-line Lunge (P=0.039), Hurdle Step (P=0.008), Trunk Stability Push-Up (P=0.033), and Rotary Stability (P=0.002) in the experimental group between the pre-test and post-test (P<0.05). In contrast, no statistically significant differences were found in the control group for the mean scores of Hurdle Step, In-line Lunge, Deep Squat, Active Straight Leg Raise, Rotary Stability, Shoulder Mobility, and Trunk Stability Push- Up between pre-test and post-test (P<0.05). Furthermore, no significant difference was observed between the two groups regarding the Active Straight Leg Raise variable. The ANCOVA test was employed to compare the total FMS score and posture control test variable (across the three indices of anterior, internal posterior, external posterior, and total Y-balance score) between the control and experimental groups. The analysis of covariance revealed a significant difference between the control and experimental groups for the total FMS score and the posture control test variable in athletes with LCS (P=0.001), as determined by examining the mean scores (Table 3).

Table 4 summarizes the paired t-test results comparing the total scores of the FMS and Y-balance tests between the pre-test and post-test.

The mean total score of the FMS test in the experimental group increased from 14.10±0.84 before DNS exercises to 17.73±1.90 after participation. The paired t-test results indicated that this increase of 3.63 was statistically significant (P=0.001). Similarly, the mean total score of the Y-balance test in the experimental group rose from

83.97±4.39 to 97.34±4.55 following DNS exercises. The paired t-test confirmed that this increase of 13.37 in the Y-balance test score was also statistically significant (P=0.001).

Discussion

The current study investigated the impact of an 8-week DNS training protocol on motor function and postural control in 20–30-year-old female athletes with LCS. Results indicated a significant improvement in the FMS test scores of athletes in the experimental group. In contrast, the control group showed no statistically significant change between pre-and post-test scores. These findings align with previous research, including studies by Arazzadeh (2018) [ 20 ], Daneshjoo (2019)

Conclusion

DNS training is a rehabilitation technique that has recently gained traction in studies that facilitate the neuromuscular system. The results showed that 8 weeks of DNS training significantly improved FMS and Y-balance test scores in female athletes with LCS. This exercise regimen enhances strength, agility, flexibility, balance, and core stability and can be conveniently performed at home or elsewhere without substantial costs. Therefore, DNS exercises are recommended for athletes with LCS to improve balance and lower limb function. These exercises may also have the potential to reduce the incidence of LCS. Experts in the field are encouraged to incorporate these exercises to mitigate the disorder. Further research is suggested to evaluate the extent of reduction in lumbar lordosis and anterior pelvic tilt in patients with LCS following these exercises.

Conflict of Interest

None declared.

References

1. Peggy A H. Therapeutic Exercise for Atheletic Injuries. Human Kinetics Inc. 2003, USA.
2. Nadler, S F. Hip muscle imbalance and low back pain in athletes: influence of core strengthening. Medicine &amp; Science in Sports &amp; Exercise, 2002. 34(1): p. 9-16.
3. Moore, M K. Upper crossed syndrome and its relationship to cervicogenic headache. Journal of manipulative and physiological therapeutics. 2004; 27(6):414-420.
4. Frank, C., P. Page, and R. Lardner,. Assessment and treatment of muscle imbalance: the Janda approach. 2009:Human kinetics.
5. Morningstar, M W. Cervical hyperlordosis, forward head posture, and lumbar kyphosis correction: A novel treatment for mid- thoracic pain. Journal of chiropractic medicine, 2003. 2(3): p. 111-115.
6. Guskiewicz, K M, D.H. Perrin. Research and clinical applications of assessing balance. Journal of Sport Rehabilitation, 1996. 5(1): p. 45-63.
7. Kobesova, A. Postural-Locomotion Function in the Diagnosis and Treatment of Movement Disorders. Summary for the lecture. Assoc. Prof. Pavel Kolar, Paed Dr., Ph. D. Alena Kobesova, MD, Ph. D.
8. Lim, Y.L., M. Lepsikova, and D.K.A. Singh. Effects of dynamic neuromuscular stabilization on lumbar flexion kinematics and posture among adults with chronic non-specific low back pain: a study protocol. In Regional Conference on Science, Technology and Social Sciences (RCSTSS 2016). 2018. Springer.
9. Cook, G. Functional movement screening: the use of fundamental movements as an assessment of function-part 2. International journal of sports physical therapy, 2014. 9(4).
10. Cook, G. Functional movement systems: Screening, assessment, corrective strategies. 2010: On Target Publications.
11. Lockie, R G. A preliminary investigation into the relationship between functional movement screen scores and athletic physical performance in female team sport athletes. Biology of sport, 2015. 32(1): p. 41.
12. Letafatkar, K., M. Alizadeh, and M. Kordi. The effect of exhausting exercise induced fatigue on the double-leg balance of elite male athletes. Journal of Social Sciences, 2009. 5(4): p. 445-451.
13. Gaerlan, M G. The role of visual, vestibular, and somatosensory systems in postural balance. 2010.
14. oudas, J.W., J.H. Hollman, and D.A. Krause. The effects of gender, age, and body mass index on standing lumbar curvature in persons without current low back pain. Physiotherapy theory and practice, 2006. 22(5): p.229-237.
15. Herrington, L. Assessment of the degree of pelvic tilt within a normal asymptomatic population. Manual therapy, 2011. 16(6): p. 646-648.
16. Rajabi, R, S Latifi. Normality of curvature of the back (kyphosis) and lumbar spine (Lordosis) of Iranian men and women. Research in Sport Sciences, 2010. 7: p. 13-30.
17. Koohkan, S. Studying the changes of the lumbar and thoracic curvatures and pelvic tilt inclinations during pregnancy in primigravida women. Rehabilitation Medicine, 2015. 3(4).
18. Gonell, A.C., J.A.P. Romero, and L.M. Soler. Relationship between the Y balance test scores and soft tissue injury incidence in a soccer team. International journal of sports physical therapy, 2015. 10(7): p. 955.
19. Brown, P. Movement: Functional Movement Systems–Screening, Assessing, Corrective Strategies On Target Publications. The Journal of the Canadian Chiropractic Association, 2012. 56(4): p. 316.
20. Arazzadeh H, Norasteh AA, Eidi Dahneh A. The Effect of 8 Weeks of Balance Training on Upper Extremity Function and Functional Movement Screening Test Scores of Adolescent Volleyball Players. Journal of Exercise Science and Medicine. 2019; 10(2):231-46.
21. Abdolrasoul Daneshjoo, Atena Eslami, Sayed Kazem Mousavi Sadati. Effect of core stability training on the balance and FMS scores of adolescent soccer players. J Rehab Med. 2020; 9(2):61-70.
22. Kiani Shikhabadi, A., R. Mahdavinejad, and N. Rahnma. Effect of 8 Weeks 11+ Training on Functional Movement Screening (FMS) Tests in Footsal&#039;s Players Women. Journal of Sport Biomechanics, 2020. 6(1). 1
23. Soltandoost, S.M., M.H. Alizadeh, and A. Shamsoddini. Effects of Functional Movement Training Program on Functional Movement Screening Scores and Selected Physical Fitness Factors in Active Injury-Prone Military Men. Journal Mil Med, 2020. 22(4): p. 174-182.
24. Mahdieh, L., V. Zolaktaf, and M.T. Karimi. Effects of dynamic neuromuscular stabilization (DNS) training on functional movements. Human Movement Science, 2020. 70: p. 102568.
25. Benfiry, N., B. Ganji, and S.S. Beigi. The Effect of 8 Weeks of Dynamic Neuromuscular Stability (DNS) Exercises on the Performance and Quality of Men and Women&#039;s Life with Apoplexy (Stroke). Egyptian Academic Journal of Biological Sciences, E. Medical Entomology &amp; Parasitology, 2018. 10(1): p. 83-93.
26. Bae, W.-s., K.-C. Lee, and D.-Y. Lee. The Effects of Dynamic Neuromuscular stabilization Exercise on Forward Head Posture and spine Posture. Medico Legal Update, 2019. 19(2): p. 670-675.
27. Bt JP, S.J., Brick MJ, Jolly JT, Lephart SM, Fu FH. Relationship between cycling mechanics and core stability. The Journal of Strength &amp; Conditioning Research in Sport Sciences, 2007. ;21(4):1300-4.
28. Rackwitz B, d.B.R., Limm H, von Garnier K, Ewert T, Stucki G. Segmental stabilizing exercises and low back pain. What is the evidence? A systematic review of randomized controlled trials. Clinical rehabilitation. 2006. ;20(7):553-67.
29. Mahmoudkhani, M R. Effect of an 8-week specific functional training on injury risk factors and athletic performance in male judokas. Scientific Journals Management System, 2019. 16(16): p. 79-92.
30. Naderi, A. Comparison between the effects of core stability exercises and neuromuscular exercises on dynamic balance and lower limb function of athletes with functional ankle instability. Scientific Journal of Kurdistan University of Medical Sciences, 2016. 21(4).
31. Borao, O. 31. Borao, O., et al., Effects of a 6-week neuromuscular ankle training program on the Star Excursion Balance Test for basketball players. Apunts. Medicina de l&#039;Esport, 2015. 50(187): p. 95-102.
32. Son, M S. Effects of dynamic neuromuscular stabilization on diaphragm movement, postural control, balance and gait performance in cerebral palsy. NeuroRehabilitation, 2017. 41(4): p. 739-746.
33. Zamani, S.B.G.a.S.S.B. The effect of eight weeks of DNS training on the balance of women with multiple sclerosis, the first national conference on the development of sports science in the field of health, prevention and championship, Qazvin, Imam Khomeini International University. 2016.
34. Mohammadi, F. Assessment of CNS function on postural control with and without Somatosensory and Vestibular perturbation in goalball players in comparison with nonathlete blind and sighted subjects. 2008, [MSc. Thesis]. Tehran: University of Tehran.
35. Myer, G D. Neuromuscular training improves performance and lower-extremity biomechanics in female athletes. The Journal of Strength &amp; Conditioning Research, 2005. 19(1): p. 51-60.
36. Hertel J, B.R., Hale SA, Olmsted- Kramer LC. Simplifying the star excursion balance test: analyses of subjects with and without chronic ankle instability. Journal of Orthopaedic &amp; Sports Physical Therapy. 2006;36(3):131-7.
37. Kibler WB, P.J., Sciascia A. The role of core stability in athletic function. Sports medicine. 2006 Mar 1;36(3):189-98.
38. Wikstrom EA, P.M., Tillman MD. Dynamic stabilization time after isokinetic and functional fatigue. Journal of Athletic Training., 2004 Jul;39(3):247.
39. Necking LE, L.G., Friden J. Hand muscle weakness in long- term vibration exposure. Journal of Hand Surgery. 2002. Dec;27(6):520-5.