Comparative Effectiveness of Auditory, Visual, and Vibrotactile Sensory Cueing Versus Sham on Tibialis Anterior Muscle Onset Latency During Gait Initiation in Community-Dwelling Older Adults: A Sham-Controlled Crossover Trial

evaluate the effect of auditory, visual, and vibrotactile sensory cues on neuromuscular preparation during gait initiation in community-dwelling older adults, using a within-subject crossover design

Randomised, sham‑controlled, within‑subject crossover trial with five experimental conditions (auditory, visual, vibrotactile, sham, self‑initiated), 42 participants, Latin square randomisation with concealed allocation, blinded outcome assessment and data analysis, single‑centre study.

This study will be conducted in the Biomechanics Laboratory at the University of Tabriz, in a single session with 10 trials of each condition. Data collectors will not be blinded; the outcome assessor and data analyst will be fully blinded. Participants will be blinded to the sequence of stimuli.

Inclusion Criteria: Age ≥ 65 years, Independent ambulation without the use of assistive devices, No history of falls during the previous year, Ability to stand, unsupported for at least 30 seconds, Ability to walk 7 metres independently, Right‑foot dominance Exclusion Criteria: Neurological disorders, Musculoskeletal disorders affecting gait or balance, Peripheral neuropathy, Hearing loss > 25 dB, Visual impairment

Intervention group: Community-dwelling older adults who will receive an auditory stimulus (750 Hz, 70 dB, 200 ms), a visual stimulus (green, 200 ms, distance of 7m), and a vibrotactile stimulus (80 Hz, 1.5 times the detection threshold). Comparison group: Community-dwelling older adults who will receive a sham stimulus (sub-threshold, 0.2 times threshold) and a self-initiated condition (without any stimulus).

Tibialis anterior and medial gastrocnemius onset latency, centre‑of‑pressure parameters, co‑activation

Preliminary pilot observations indicated that requiring older adults to attend five separate sessions with a 24–48-hour interval between sessions was practically demanding for this age group and substantially increased the risk of participant attrition across sessions. Furthermore, given that older adults typically do not maintain consistent physical or daily conditions across different days of the week, conducting the protocol across multiple separate sessions increased the risk of confounding factors (such as day-to-day medication changes, or fluctuations in physical status) influencing the results between sessions. Therefore, to reduce participant attrition and eliminate potential confounding effects arising from the time interval between sessions, it was decided to modify the study protocol from five separate sessions to a single laboratory session, while keeping the randomised sequence of experimental conditions (Latin square design) unchanged.

This study will be designed as a crossover trial, and each participant will experience all five experimental conditions. Because the four externally cued conditions (auditory, visual, vibrotactile, and sham) require order balancing, a 4 × 4 Latin square design will be used as the block randomization method. This design will ensure that each of the four conditions occupies each of the four sequence positions (first through fourth) an equal number of times, thereby controlling for order and carry-over effects. The self-initiated condition, since it will serve solely as a descriptive reference, will always be performed after completion of the other four conditions and will not be included in the randomization sequence. The unit of randomization will be the individual; that is, each participant will be independently allocated to one of the four Latin-square sequences. Stratified randomization will not be used in this study. The random sequence will be generated using the online software Randomization.com. This will be carried out by an investigator who will not be involved in outcome assessment. The four allocation sequences derived from the Latin square design will be pre-determined. For allocation concealment, each participant's sequence number will be placed in opaque, sequentially numbered, sealed envelopes, which will be opened in the order in which participants enter the study; in this way, the intervention sequence for each individual will remain concealed until the start of the testing session. The outcome assessor (the individual analyzing the EMG and COP data) and the statistical analyst will be kept blinded to each participant's allocation sequence throughout the study.

This study will employ partial blinding. Participants will be blinded to the sequence of the four externally cued conditions (visual, auditory, vibrotactile, and sham), as this sequence will be concealed through the 4 × 4 Latin square design and sealed envelopes, so that participants will not know the upcoming condition prior to each session. However, participants will not be blinded to the nature of the intervention at the moment it is delivered, except in the vibrotactile condition: because the auditory (audible tone) and visual (visible light) stimuli are inherently and overtly perceptible, participants will immediately recognize whether the stimulus received was auditory or visual; complete participant blinding to these two interventions is therefore not achievable. Only in the vibrotactile condition, due to the active sham design at a sub-threshold intensity (0.2 times the individual detection threshold), will participants be unable to reliably distinguish the active stimulus from sham, allowing for meaningful blinding. The principal investigators and data collectors will not be blinded, owing to the perceptible nature of the auditory, visual, and vibrotactile stimuli at the time of administration, but will follow a standardized protocol. Both the outcome assessor and the data analyst will be fully blinded; condition labels will be replaced with random codes by an independent researcher, and analysis will be conducted on de-identified data. A data and safety monitoring board will not be established, and the manuscript authors will have access only to the final analyzed data.

De-identified Individual Participant Dataset — Sensory Cueing and Gait Initiation Trial: This dataset will include all primary and secondary outcome variables recorded at the individual level: tibialis anterior onset latency, medial gastrocnemius onset latency, onset latency variability, centre-of-pressure parameters (onset time, posterior displacement, peak velocity), step latency, first-step length, and baseline demographic variables (age, sex, body mass index, MoCA score, frailty status). The co-activation index, as an exploratory variable, will also be included in this dataset but will be explicitly labeled as "exploratory." All direct and indirect participant identifiers will be removed prior to publication. Full Study Protocol: The complete study protocol, including inclusion and exclusion criteria, detailed description of interventions, randomization and allocation concealment methods, and the pre-specified outcome measurement plan. Statistical Analysis Plan: Full specification of the pre-specified statistical models (linear mixed-effects models, Benjamini-Hochberg adjustment, BCa bootstrap), data quality criteria, and pre-planned sensitivity analyses. R Statistical Analysis Scripts: Complete R code (including the lme4, lmerTest, and boot packages) to reproduce all primary, secondary, sensitivity, and exploratory analyses reported in the manuscript. Informed Consent Form: A blank, de-identified template of the informed consent form used in this study (the form template only, not completed participant forms).

The access period for de-identified data, analysis scripts, and supplementary materials will begin immediately upon final acceptance of the manuscript for publication. These materials will be accessible via a Digital Object Identifier (DOI), included in the published article, hosted in the public Zenodo repository, and this access will continue for a minimum of 10 years from the date of publication. During the peer review process (prior to final acceptance), materials will be made available through the corresponding author upon reasonable request.

Because the data and documents from this study will be deposited publicly and without access restrictions in the Zenodo repository, they will be available to any researcher — whether affiliated with academic institutions, research centres, or industry — whose intended use is legitimate scientific research, replication of findings, or meta-analysis, without requiring specific permission from the authors. The only requirement will be appropriate citation of the original data source (the published article and repository DOI).

In addition to the criteria described above regarding who is eligible to request access, the following conditions will govern the use of data and documents from this study: 1. Purpose of use: Data may be used solely for non-commercial research purposes; any commercial use will require separate written permission from the corresponding author. 2. Permitted types of analysis: No restrictions will be placed on the type of statistical analysis or research methodology applied to the delivered data; researchers may use any analytical approach appropriate to their research objectives. 3. Request process: Applicants must submit a written request to the corresponding author, including the project title, research objectives, proposed methodology, and a written commitment to adhere to research ethics principles. 4. Data delivery mechanism: Upon approval of the request, data will be provided to the applicant either through the public Zenodo repository (using the dedicated DOI) or via direct file transfer. 5. Citation requirement: Researchers will be required to properly cite the data source, including the DOI and reference to the original article, in any publication resulting from secondary use of the data. 6. Participant privacy protection: Applicants will be required to commit to using the data solely for the purposes stated in their request and to refrain from any attempt at re-identification of participants.

First priority (public and direct access): All de-identified data, analysis scripts, and supplementary materials will be deposited in the public Zenodo repository and will be accessible via the Digital Object Identifier (DOI) included in the published article. Applicants may download the data free of charge by following the DOI link in the article, without needing to contact the authors directly. Second priority (request to the corresponding author): For supplementary information or documents not deposited in the public repository (e.g., the informed consent form), applicants may submit a written request — including the project title, research objectives, proposed methodology, and a written commitment to research ethics principles — to the corresponding author. Corresponding author contact information: Name: Hamed Fadaei Affiliation: Department of Sports Pathology and Biomechanics, Faculty of Sport Sciences, Kharazmi University, Tehran Postal address: 15719-14911 Email: hamed.fadaei1371@gmail.com Phone: 09025527109

Applicants should first access the public Zenodo repository via the Digital Object Identifier (DOI) provided in the article and download the data directly and free of charge, a process expected to take less than 5 minutes. If access to the repository is not possible, the applicant must submit a written request — including the project title, research objectives, proposed methodology, and a commitment to adhere to research ethics principles — by email to the corresponding author. The request will be reviewed within 3 to 7 business days, and if approved, the data will be provided to the applicant within 1 to 3 business days via an access link, email, or secure file-sharing platforms. The total time required, in cases where the public repository is not accessible, will be approximately 1 to 2 weeks.