اثر تحریک جریان مستقیم فراجمجمه‌ای مخچه بر زمان رسیدن به پایداری سالمندان

Extended Abstract
Background and Purpose
Maintaining balance requires the coordinated interaction of multiple systems, including sensory, musculoskeletal, and neuromuscular components (1). Age-related declines in postural control are attributed to deterioration across these systems, manifesting as reduced muscle strength, musculoskeletal deformities, cognitive impairments, and slower motor responses (2). Stair use, increasingly common due to apartment living, constitutes a daily activity notably associated with falls among older adults (3). Injuries resulting from descending stairs occur approximately three times more frequently than during ascent. An essential strategy to mitigate such injuries is the ability to rapidly regain stability after perturbations (4).
Time to stabilization (TTS) quantitatively measures the body’s capacity to minimize postural sway transitioning from dynamic to static phases. In recent years, non-invasive brain stimulation (NIBS) techniques have emerged as promising adjunctive therapies for balance rehabilitation in older populations (5). Specifically, cerebellar stimulation has shown efficacy in improving balance, yet challenges remain in translating these effects to real-world activities of daily living.
In response, this study utilized a stair descent task performed on a force plate to realistically assess dynamic balance through TTS measurements. The primary objective was to investigate the effect of cerebellar transcranial direct current stimulation (tDCS) on TTS in elderly individuals, providing ecologically valid insights into potential therapeutic interventions targeting fall risk among this population.
 
Methods
This semi-experimental applied study employed a pretest-posttest design with a sham-controlled group. Thirty healthy elderly men aged between 60 and 75 years from Ahvaz city voluntarily participated and were randomly assigned via lottery into two groups of 15 each: cerebellar tDCS intervention and sham tDCS.
Inclusion criteria required participants to:

Independently walk 10 meters,
Stand unassisted for at least 10 seconds,
Possess normal vision, and
Follow simple verbal instructions.

Exclusion criteria encompassed:

Limiting musculoskeletal disorders,
Neurological conditions (e.g., stroke, Parkinson’s disease, paralysis),
Cardiovascular disorders,
Uncontrolled hypertension,
Dementia (defined as scoring below 22 on the Brief Mental Status Examination), and
Conditions or medication use impacting balance and movement.

The study comprised three phases: pretest, intervention, and posttest. At pretest, participants completed three stair descent trials on a force plate, with two-minute rests between trials. The intervention phase spanned two weeks, entailing five consecutive daily sessions each week (totaling ten sessions).
The cerebellar tDCS group underwent 20-minute daily anodal stimulation over the cerebellar cortex (anode placed 2 cm below the inion; cathode at Cz), with a constant current of 1.5 mA. The sham group received placebo stimulation following an identical protocol.
Forty-eight hours after the final intervention session, participants performed three posttest stair descent trials, with TTS recorded via force plate data. Given between-group baseline differences, data were analyzed using analysis of covariance (ANCOVA) with pretest scores as covariates, thereby effectively isolating cerebellar tDCS effects on dynamic balance compared to sham.
 
Results
Demographic variables did not differ significantly between groups: age (P = 0.86), height (P = 0.97), and weight (P = 0.11). ANCOVA revealed a significant group effect on anteroposterior TTS, with effect size η² = 0.44. The cerebellar tDCS group exhibited significantly faster stabilization than the sham group, with a mean difference of 0.78 seconds (P < 0.05).
Similarly, significant differences were observed for mediolateral TTS, with η² = 0.49. The intervention group showed quicker mediolateral stabilization relative to sham by 0.55 seconds on average (P < 0.05).
These findings demonstrate that cerebellar tDCS effectively improves both anteroposterior and mediolateral stabilization times compared to sham stimulation in older adults.
 
Conclusion
This study evaluated the impact of cerebellar tDCS on dynamic balance, specifically time to stabilization, during stair descent among elderly men. The results indicate that ten sessions of cerebellar tDCS significantly enhance postural stabilization in both the anteroposterior and mediolateral directions.
These outcomes align with prior research such as Parsaei et al. (6), which reported improvements in static and dynamic balance following cerebellar tDCS in older males, and Ehsani et al. (5), confirming cerebellar tDCS efficacy in elderly balance enhancement. Conversely, findings diverge from Steiner et al. (7), who observed no balance improvements in young adults after cerebellar tDCS, possibly reflecting age-dependent variations in neuroplastic responses.
Cerebellar tDCS likely facilitates more precise central nervous system modulation over balance fluctuations, thereby reducing fall risk and improving overall postural control in the elderly. Importantly, our study corroborated previous evidence that sham tDCS does not influence postural or gait performance, affirming that observed improvements derive from anodal cerebellar stimulation rather than placebo effects.
In summary, cerebellar tDCS emerges as a promising non-invasive intervention to accelerate recovery of postural stability during ecologically valid tasks such as stair descent in older adults. These findings advocate for wider adoption and further research into cerebellar tDCS to prevent falls and promote mobility in aging populations.
Keywords: Noninvasive Brain Stimulation, Postural Control, Elderly
 
Article Message
This research demonstrates that cerebellar tDCS administered over ten sessions significantly improves both anteroposterior and mediolateral time to stabilization during stair descent among elderly men. These balance enhancements were absent in sham controls, underscoring the specific efficacy of cerebellar tDCS. The intervention presents a promising non-invasive therapy to improve dynamic balance and reduce fall risks in older adults performing everyday activities such as stair negotiation.
Ethical Considerations
All research protocols complied with ethical standards, including informed participant consent, confidentiality of data, and adherence to scientific integrity.
Authors’ Contributions
This article is extracted from a doctoral dissertation in Physical Education and Sport Sciences focused on motor behavior by Mosna Kazem Alkari, supervised primarily by Dr. Farzaneh Davari (responsible author), with secondary supervision by Dr. Mazin Hadi Kazr Altaie and advisory support from Dr. Zohreh Meshkati.
Conflicts of Interest
The authors declare no conflicts of interest.
 Acknowledgment
We sincerely thank all participants for their invaluable cooperation in this research.