Immediate Effect of Slump Neural Tensioners Compared With Neural Sliders on Dynamic Balance in Asymptomatic Young Adults

BACKGROUND Dynamic balance is a fundamental sensorimotor function required for safe and efficient movement during daily activities, sports, and rehabilitation. It depends on the continuous integration of proprioceptive, vestibular, and visual inputs with appropriate neuromuscular responses. Restrictions in neural tissue mobility - even in asymptomatic individuals - may impair afferent proprioceptive signaling from mechanoreceptors distributed along the peripheral neural pathway, potentially degrading neuromuscular coordination and dynamic balance performance.

Neural mobilization (NM) is a movement-based physiotherapy intervention designed to restore normal neural tissue mechanics and physiology. It comprises two primary techniques: the neural slider, which promotes nerve excursion through alternating opposite-direction joint movements with minimal neural strain; and the neural tensioner, which applies controlled mechanical loading through simultaneous same-direction joint movements to improve the viscoelastic properties of neural tissues. Both techniques are performed in the slump sitting position - a standardized posture that effectively loads the posterior neuromeningeal tract and sciatic nerve - making it optimal for lower limb neurodynamic interventions.

While existing evidence confirms that both techniques improve hamstring flexibility and reduce neural mechanosensitivity, their comparative immediate effects on dynamic balance in asymptomatic young adults remain unclear. Most prior studies have focused on symptomatic populations, making it difficult to isolate the pure neurodynamic contribution to balance from the confounding effects of pain relief. The present study was designed to address this gap.

STUDY DESIGN This is a two-arm parallel-group randomized controlled trial. Participants are randomly allocated in a 1:1 ratio to one of two intervention groups using a computer-generated randomization sequence prepared by an independent researcher not involved in data collection. Allocation concealment is maintained using sequentially numbered, sealed opaque envelopes opened immediately prior to the intervention session.

SETTING The study is conducted at the Physiotherapy Laboratory, College of Health Sciences, Gulf Medical University, Ajman, United Arab Emirates. All assessments and interventions are performed in the same standardized laboratory environment to minimize environmental confounding.

PARTICIPANTS One hundred asymptomatic young adults aged 18-25 years are recruited from Gulf Medical University and the surrounding community using convenience sampling. Eligibility is confirmed through clinical screening, the Nordic Musculoskeletal Questionnaire (NMQ), and physical assessment prior to enrollment.

Inclusion Criteria:

Age 18-25 years Male or female Healthy with no current musculoskeletal pain or neurological symptoms Able to assume and maintain the slump sitting position Willing to provide written informed consent

Exclusion Criteria:

Diagnosed neurological disorders Musculoskeletal injury or surgery within the past 6 months Vestibular dysfunction or balance disorders Lower limb deformity or congenital abnormalities Active musculoskeletal pain (NRS > 0/10) Any contraindication to neural mobilization

BASELINE ASSESSMENTS

Prior to randomization, all participants undergo the following standardized assessments performed by a trained physiotherapist:

Demographic and anthropometric data: age, gender, height, weight, body mass index (BMI) Nordic Musculoskeletal Questionnaire (NMQ) for musculoskeletal symptom screening International Physical Activity Questionnaire - Short Form (IPAQ-SF) for physical activity level classification Leg length measurement: anterior superior iliac spine (ASIS) to medial malleolus using a measuring tape Foot length measurement: heel to longest toe using a standardized measuring scale Hamstring length: Active Knee Extension Test (90-90 test) using a universal goniometer (ICC > 0.90) Knee range of motion: universal goniometer Ankle dorsiflexion range of motion: universal goniometer

Primary Outcome - Lower Quarter Y Balance Test (YBT-LQ):

Dynamic balance is assessed using the Lower Quarter Y Balance Test in three reach directions: anterior (ANT), posteromedial (PM), and posterolateral (PL). Participants stand on the test limb on a central platform and reach maximally with the contralateral limb in each direction. Three practice trials are performed to minimize learning effects, followed by three recorded trials per direction. Reach distances are measured in centimetres, normalized to leg length, and averaged across three trials. A composite score is calculated as the mean of the three normalized reach distances multiplied by 100. The YBT-LQ demonstrates high reliability (ICC = 0.85-0.99) and predictive validity for lower extremity injury risk.

INTERVENTIONS Both interventions are administered by the same trained physiotherapist following a standardized written protocol. All participants are positioned in the slump sitting posture: thoracic and lumbar spine in full flexion, hands clasped behind the back, hips flexed to 90 degrees, knees flexed to approximately 90 degrees, and ankles in neutral position.

Group A - Slump Neural Slider Technique:

The participant actively performs cervical spine extension combined with knee extension and ankle dorsiflexion, followed by cervical spine flexion combined with knee flexion and ankle relaxation. This alternating movement promotes bidirectional neural excursion along the posterior kinetic chain with minimal increase in neural strain. The end position is held for 2 seconds before returning to the starting position. The movement is performed slowly and in a controlled manner at approximately 4 seconds per repetition. The technique is administered for 10 repetitions per set, 3 sets, with 30-second rest intervals between sets. Total intervention time is approximately 3-4 minutes. The intervention is stopped immediately if the participant reports pain greater than 3/10, numbness, tingling, dizziness, or cramping.

Group B - Slump Neural Tensioner Technique:

The participant maintains the cervical spine in sustained flexion while simultaneously performing active knee extension and ankle dorsiflexion, progressively increasing mechanical loading along the entire posterior neuromeningeal pathway. The end position is held for 2-3 seconds before returning to the starting position. Movements are slow and controlled at approximately 4-5 seconds per repetition. The technique is administered for 10 repetitions per set, 3 sets, with 30-second rest intervals between sets. Total intervention time is approximately 3-4 minutes. The intervention is stopped immediately if the participant reports pain greater than 3/10, numbness, tingling, dizziness, or excessive neural discomfort.

POST-INTERVENTION ASSESSMENT Immediately following the completion of the assigned intervention, dynamic balance is reassessed using the Lower Quarter Y Balance Test following the identical standardized procedure used at baseline. Reach distances in the anterior, posteromedial, and posterolateral directions are recorded as post-intervention outcome values.

SAMPLE SIZE The sample size was calculated based on the two-sample independent t-test formula for comparison of two independent groups. Assuming a two-tailed alpha of 0.05, 80% statistical power, a clinically meaningful between-group difference of 5 points in the YBT composite score, and a pooled standard deviation of approximately 8 points derived from pilot data and prior literature, the required sample size is approximately 44 participants per group. This was increased to 50 per group (total n = 100) to account for a 10-12% dropout rate commonly observed in similar single-session intervention studies, ensuring adequate statistical power for robust inference.

STATISTICAL ANALYSIS PLAN

All data are entered and analyzed using IBM SPSS Statistics software (Version 28). The following analytical approach is employed:

Descriptive Statistics: Mean and standard deviation for continuous variables; frequency and percentage for categorical variables. Used to summarize baseline demographic and anthropometric characteristics of both groups.

Normality Testing: Shapiro-Wilk test applied to all continuous outcome variables prior to inferential analysis.

Within-Group Analysis: Paired samples t-test used to compare pre- and post-intervention YBT reach distances (ANT, PM, PL, and composite score) within each group separately.

Between-Group Analysis: Independent samples t-test used to compare the magnitude of change (post minus pre) in YBT scores between Group A (Neural Slider) and Group B (Neural Tensioner).

Effect Size: Cohen's d calculated for all significant comparisons to quantify the practical significance of observed differences.

Side-to-Side Asymmetry: Paired t-test used to evaluate limb asymmetry in YBT reach distances before and after the intervention within each group.

Level of Significance: p \< 0.05 is considered statistically significant for all analyses.

PLAN FOR MISSING DATA Given the single-session design of this study, missing data are not anticipated. However, should any participant be unable to complete the post-intervention YBT assessment due to discomfort or withdrawal, their data will be excluded from the analysis and documented as a protocol deviation. No imputation methods will be applied. All withdrawals and reasons for missing data will be reported transparently in the final manuscript.

DATA MANAGEMENT AND QUALITY ASSURANCE All data are recorded on pre-designed, standardized paper-based data collection forms at the time of assessment. Data are subsequently entered into password-protected electronic spreadsheets by the principal investigator. A second team member independently verifies 100% of entered data against source documents to identify and correct transcription errors. Both hard copy and electronic copies of all data are stored securely at Gulf Medical University for a minimum of three years following study completion, accessible only to the authorized research team. No personal identifiers are included in the analysis dataset; participants are identified by unique numeric codes only.

ETHICAL CONSIDERATIONS The study has received ethical approval from the Gulf Medical University Institutional Review Board (GMU-IRB). All participants provide written informed consent prior to enrollment. Participation is entirely voluntary and participants may withdraw at any time without consequence. Confidentiality is maintained throughout by replacing personal identifiers with participant codes in all records and publications.