Fractal vs Isochronous Cueing in Athletes After ACL Reconstruction

NCT07243535 | Recruiting

• 1 other identifier: SyncGait-5725
• Study Type: interventional
• Target: 36
• Locations: 1 country
• Sites: 1

Brief Summary

Anterior cruciate ligament (ACL) injuries are among the most prevalent and functionally limiting knee injuries in sports, particularly those that involve pivoting movements. Despite advancements in surgical reconstruction and physical rehabilitation, many athletes continue to exhibit persistent motor control deficits and increased gait variability, both of which are closely linked to a heightened risk of re-injury and long-term joint degeneration. These deficits arise from biomechanical impairments and disrupt proprioceptive input that requires cortical reorganization, contributing to maladaptive neuroplasticity. However, conventional rehabilitation strategies often overlook this neural dimension. Recent findings emphasize the importance of fostering motor variability and promoting neuroplasticity through external focus strategies, including sensorimotor synchronization. While isochronous cues, an invariant stimulus, are commonly used, they do not reflect the natural fluctuations of healthy gait and may reduce its complexity. Fractal-based cues, in contrast, introduce structured variability resembling the natural dynamics of locomotion and have been shown to restore gait complexity in clinical populations. However, no study has yet explored their acute effects on gait variability and corticospinal function following ACL reconstruction (ACLR). This crossover randomized controlled trial aims to compare the acute effects of a single session of treadmill walking synchronized to either fractal or isochronous-based visual cues on gait variability and corticospinal measures in athletes with ACLR. The investigators hypothesize that fractal-based cueing will acutely restore gait variability and enhance corticospinal excitability, evidenced by increased corticospinal excitability and intracortical facilitation, and reduced short-interval intracortical inhibition, thus promoting adaptive neuroplasticity. Conversely, isochronous cueing is expected to maintain or decrease gait complexity without improving corticospinal measures. This study may provide insights that could be highly valuable as a way to promote neuroplasticity and optimize gait rehabilitation after ACLR, also allowing an objective quantification and aiming to restore variability to levels close to those observed in healthy individuals, thus contributing to reducing the re-injury rate.

Conditions

Anterior Cruciate Ligament Reconstruction; Anterior Cruciate Ligament Reconstruction Rehabilitation; Athlete

Keywords

Complexity; Excitability; Metronome; Neuroplasticity; Rehabilitation

Outcome Measures

Primary Outcomes (5)

• Gait Variability Measured by Fractal Scaling Exponent of inter-stride intervals

  The fractal-scaling exponent, α, of inter-stride intervals (α-ISIs) will be determine by calculating the time between two consecutive heel strikes of the same foot. First, the investigators will identify the heel strike events of the dominant foot. To improve the identification of this event, the signals will be filtered using a 2nd order, zero lag low-pass Butterworth filter with a cutoff frequency of 20 Hz. Then, Detrended Fluctuation Analysis (DFA) will be used to determine the fractal-scaling, an index of complexity. The DFA is a modified random-walk analysis that makes use of a long-range correlated time series. The long-range correlation can be mapped to self-similar calculations through simple integration.

  Pre- (40 minutes before) and Post- (40 minutes after) -Intervention

• Corticospinal Excitability Measured by Motor Evoked Potential Amplitude

  Conducted using Spike2 software (version 10; Cambridge Electronic Design, Cambridge, United Kingdom) and subsequently exported to, MATLAB R2018a (The MathWorks, Natick, Massachusetts, United States) for processing and analysis. Corticospinal Excitability will be quantified as the peak-to-peak amplitude of MEPs elicited by a single-pulse TMS stimulus, with values averaged across 10 trials per participant.

  Baseline (Pre) and immediately after the intervention (Post)

• Cortical Silent Period (SP) Duration

  Silent period will be calculated as the time from MEP onset to the resumption of voluntary EMG activity, expressed as SP = resumption of voluntary EMG time - MEP onset (58), and averaged across all 10 stimuli.

  Baseline (Pre) and immediately after the intervention (Post)

• Intracortical Facilitation (ICF)

  ICF will be determined using the same calculation method but with an interstimulus interval of 12 ms (ICF = conditioned MEP / control MEP).

  Baseline (Pre) and immediately after the intervention (Post)

• Short-Interval Intracortical Inhibition (SICI)

  SICI will be calculated as the ratio between the conditioned MEP elicited with a paired-pulse TMS protocol (interstimulus interval: 3 ms) and a control MEP obtained from AMT assessment, expressed as SICI = conditioned MEP / control MEP.

  Baseline (Pre) and immediately after the intervention (Post)

Secondary Outcomes (2)

• Magnitude of variability

  Pre- (40 minutes before) and Post- (40 minutes after) -Intervention

• Synchronization Accuracy

  During Intervention

Other Outcomes (3)

• Demographic characterization of the sample by Lysholm Knee Score (LKS).

  At the beginning of the first session (Day 1)

• Demographic characterization of the sample by Tegner Activity Scale (TAS)

  At the beginning of the first session (Day 1)

• Demographic characterization of the sample by Tampa Scale of Kinesiophobia (TSK)

  At the beginning of the first session (Day 1)

Study Arms (2)

Fractal Cueing, Then Isochronous Cueing

EXPERIMENTAL

Participants exposed to 12-minute treadmill walking synchronized to a visual fractal metronome individualized to stride time variability. After a washout period of 1 week, participants will be exposed to 12-minute treadmill walking synchronized to a visual isochronous metronome with fixed stride time.

Device: Fractal Cueing; Device: Isochronous Cueing

Isochronous Cueing, then Fractal cueing

EXPERIMENTAL

Participants exposed to 12-minute treadmill walking synchronized to a visual isochronous metronome with fixed stride time. After a washout period of 1 week, participants will be exposed to 12-minute treadmill walking synchronized to a visual fractal metronome individualized to stride time variability.

Device: Fractal Cueing; Device: Isochronous Cueing

Interventions

Fractal Cueing DEVICE

Walking synchronized to a visual fractal metronome.

Fractal Cueing, Then Isochronous Cueing; Isochronous Cueing, then Fractal cueing

Isochronous Cueing DEVICE

Walking synchronized to a visual Isochronous metronome.

Fractal Cueing, Then Isochronous Cueing; Isochronous Cueing, then Fractal cueing

Eligibility Criteria

• Age: 15 Years - 35 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Child (0-17), Adult (18-64)

You may qualify if:

• Undergone unilateral ACL reconstruction less than 2 years ago;
• Have medical release for the full load on the injury limb for at least 2 weeks;
• Be independently pain-free walking;
• Being sports athletes according to an athlete description: Training regularly to improve performance, actively participating in competitions or formally registering in a sports federation or association;
• Must be able to understand and perform the requested task.

You may not qualify if:

• Participants with previous surgery on either knee;
• Those with more than 3 months between ACL injury and surgery;
• More than 2 weeks between surgery and the start of physical therapy;
• Had another musculoskeletal injury in the lower limb within the past 6 months;
• Another musculoskeletal surgery within the past 18 months;
• Participants with a history of movement system pathologies, such as nervous system, cardiovascular, pulmonary, integumentary, or endocrine conditions;
• Participants with vestibular or somatosensory system pathologies or visual impairments limiting their ability to see the metronome required for the task;
• Use of medications that could affect locomotion and balance.

Sponsors & Collaborators

• Egas Moniz - Cooperativa de Ensino Superior, CRL: lead

Study Sites (1)

Egas Moniz School of Health & Science

Almada, Monte de Caparica, 2829-511, Portugal

RECRUITING

Related Publications (5)

• Grooms DR, Page SJ, Nichols-Larsen DS, Chaudhari AM, White SE, Onate JA. Neuroplasticity Associated With Anterior Cruciate Ligament Reconstruction. J Orthop Sports Phys Ther. 2017 Mar;47(3):180-189. doi: 10.2519/jospt.2017.7003. Epub 2016 Nov 5.

  PMID: 27817301 BACKGROUND

• Bodkin SG, Bruce AS, Hertel J, Diduch DR, Saliba SA, Novicoff WM, Hart JM. Visuomotor therapy modulates corticospinal excitability in patients following anterior cruciate ligament reconstruction: A randomized crossover trial. Clin Biomech (Bristol). 2021 Jan;81:105238. doi: 10.1016/j.clinbiomech.2020.105238. Epub 2020 Nov 20.

  PMID: 33234323 BACKGROUND

• Moraiti CO, Stergiou N, Vasiliadis HS, Motsis E, Georgoulis A. Anterior cruciate ligament reconstruction results in alterations in gait variability. Gait Posture. 2010 Jun;32(2):169-75. doi: 10.1016/j.gaitpost.2010.04.008. Epub 2010 Jun 29.

  PMID: 20591671 BACKGROUND

• Vaz JR, Groff BR, Rowen DA, Knarr BA, Stergiou N. Synchronization dynamics modulates stride-to-stride fluctuations when walking to an invariant but not to a fractal-like stimulus. Neurosci Lett. 2019 Jun 21;704:28-35. doi: 10.1016/j.neulet.2019.03.040. Epub 2019 Mar 25.

  PMID: 30922850 BACKGROUND

• Vaz JR, Knarr BA, Stergiou N. Gait complexity is acutely restored in older adults when walking to a fractal-like visual stimulus. Hum Mov Sci. 2020 Dec;74:102677. doi: 10.1016/j.humov.2020.102677. Epub 2020 Oct 15.

  PMID: 33069099 BACKGROUND

Study Officials

• João R Vaz, PhD

  Egas Moniz school of Health & Science

  STUDY DIRECTOR

Central Study Contacts

Inês D Ribeiro, MSC Student

CONTACT

(+351) 964 544 607; 115360@alunos.egasmoniz.edu.pt

Catarina S Pino, MSC Student

CONTACT

(+351) 937 780 194; 118878@alunos.egasmoniz.edu.pt

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: DOUBLE
• Who Masked: PARTICIPANT, OUTCOMES ASSESSOR
• Masking Details: The randomized order will be transmitted only to the main researcher through a sealed envelope. Participants will be blinded throughout their participation. Importantly, the participants are unable to detect the subtle changes in variability between the Isochronous and Fractal cueing conditions. The main researcher will not be blinded for the condition given the necessity to program the metronome per session. However, the remaining team will be blinded and, therefore, will run the data analysis.
• Purpose: BASIC SCIENCE
• Intervention Model: CROSSOVER
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Model Details: This study is a crossover randomized controlled trial, comprising two sessions. Each session will take approximately 2 hours, and the sessions will be separated from 7 to 10 days. Both sessions will be held at the same period of the day to avoid the circadian effect on our primary outcome. The two sessions will be similar. At the beginning of the first session, however, three questionnaires will be administered to collect the demographic and baseline characteristics of the participants. Following the completion of these questionnaires, a randomization process through a fixed block method will be conducted by the study's supervisor to determine the order in which the intervention will be presented across the two sessions. The participants will be asked to complete three 12-minute gait trials in each session: one cued trial and two uncued trials. A minimum of 20 minutes of rest will be taken between each trial while collecting the cortical drive assessment, PRE and POST the cued trial.

Study Record Dates

• First Submitted: September 16, 2025
• First Posted: November 24, 2025
• Study Start: October 3, 2025
• Primary Completion: February 1, 2026
• Study Completion: February 1, 2026
• Last Updated: November 24, 2025

Record last verified: 2025-11

Data Sharing

• IPD Sharing: Will share

Locations

PT (1)