Plantar Needle-pricking for Early Lower-Limb Recovery After Stroke via the Nociceptive Withdrawal Reflex: Assessor-Blinded Randomized Trial

Summary

An assessor-blinded randomized trial in post-stroke flaccid hemiplegia (Brunnstrom I) tested plantar needle-pricking to evoke nociceptive withdrawal reflexes. After six days of treatment plus standardized rehabilitation, more participants progressed beyond stage I (12/38 vs. 3/38 controls), with greater Brunnstrom stage change (P = 0.013).

Abstract

This assessor-blinded randomized controlled trial evaluated whether a standardized plantar needle-pricking protocol designed to evoke the nociceptive withdrawal reflex (NWR) improves early lower-limb motor recovery in post-stroke flaccid hemiplegia. Eighty patients were randomized (1:1) to receive either NWR-evoking plantar needle-pricking plus standardized rehabilitation or standardized rehabilitation alone for 6 consecutive days; 76 participants completed outcome assessments (38 per group). Primary outcomes were Brunnstrom stage and the Fugl-Meyer Assessment of the Lower Extremity (FMA-LE). By day 6, the pricking group demonstrated a greater shift in Brunnstrom stage distribution (P = 0.03; Cramér's V = 0.31, 95% CI 0.14-0.48) and a larger median Brunnstrom stage change from baseline (1 [0-1] vs. 0 [0-1]; P = 0.013; effect size r = 0.29, 95% CI 0.06-0.48). FMA-LE total score at day 6 was higher in the pricking group (16 [12-19] vs. 11 [8-14]; P < 0.01; effect size r = 0.38, 95% CI 0.17-0.56). Secondary outcomes favored the pricking group for lower-limb active range of motion, manual muscle strength, and knee flexor tone (all P < 0.05). Outcome assessors guessed allocation at a rate not different from chance (52.6%; P = 0.68). One participant experienced mild local bruising that resolved without intervention; no serious adverse events occurred. This protocol provides a reproducible, safety-annotated approach for reflex-based early lower-limb rehabilitation after stroke.

Introduction

Stroke is one of the leading causes of long-term disability worldwide, characterized by sudden neurological deficits and high recurrence rates, and it imposes a substantial burden on patients' quality of life^1,2. Among survivors, hemiplegia is the most common motor impairment, with early-stage flaccid paralysis (Brunnstrom stage I) representing a critical barrier to functional recovery³. Patients at this stage typically present with loss of voluntary motor control, diminished muscle tone, and weakened tendon reflexes, which restrict active task practice and delay rehabilitation gains, thereby increasing the risk of chronic disability⁴. Early induction of reflex activity and restoration of basic motor output are therefore clinically important targets for improving prognosis⁵.

Neuromuscular facilitation offers a pathway for intervention when voluntary drive is minimal. The nociceptive withdrawal reflex (NWR) evokes coordinated flexion of the hip, knee, and ankle in response to peripheral noxious stimulation, engaging multi-muscle synergies through spinal and supraspinal circuits^6,7. Electrical stimulation has been applied to elicit NWR-like responses and improve lower-limb motor performance, but fixed stimulation parameters (site, intensity, frequency) may promote habituation and reduce responsiveness across repeated sessions⁸. In contrast, acupuncture-derived stimulation permits controlled variation in stimulus location and timing within a standardized protocol, which may help limit adaptation while maintaining a reproducible therapeutic "dose"⁹.

Building on prior evidence that foot needle-pricking improved lower-limb motor function in patients at Brunnstrom stage III¹⁰, the present randomized controlled trial investigates whether reflex-elicitation needle-pricking can accelerate rehabilitation during the flaccid phase (Brunnstrom stage I). By systematically evaluating functional outcomes with standardized scales, this study aims to determine the feasibility and clinical relevance of needle-pricking-induced reflex activation in early post-stroke recovery¹¹.

Protocol

This single-center, assessor-blinded randomized controlled trial evaluated whether successive foot needle-pricking could evoke withdrawal-related reflex patterns and accelerate motor recovery in patients with post-stroke flaccid hemiplegia. All procedures involving human participants were conducted in accordance with institutional guidelines and the principles of the Declaration of Helsinki. The study was approved by the Institutional Ethics Committee of Jiangdu People's Hospital (Yangzhou, China) and registered with the Chinese Clinical Trial Registry (ChiCTR2200058142). Written informed consent was obtained from each participant prior to enrollment.

1. Participant recruitment, screening, and enrollment

Participants were recruited from the Departments of Neurology and Traditional Chinese Medicine Rehabilitation at Jiangdu People's Hospital between March 2023 and August 2024. Screening was conducted by two independent therapists using a prespecified eligibility checklist during routine clinical hours. Inclusion criteria were: (i) first-ever ischemic or hemorrhagic stroke confirmed by CT or MRI; (ii) lower-limb impairment at Brunnstrom stage I within 1 month after stroke onset; (iii) age 30-79 years; and (iv) ability to follow clinician instructions and cooperate with repeated assessments. Exclusion criteria included:(i) unstable vital signs, (ii) neurodegenerative disease, (iii) peripheral neuropathy, (iv) severe cardiac/hepatic/renal dysfunction, (v) wounds or signs of infection at intended stimulation sites, and (vi) cognitive or language impairment that could compromise assessment validity or protocol adherence¹². Baseline assessments were scheduled at comparable times of day to reduce diurnal variation.

2. Sample size determination, randomization, allocation concealment, and blinding

Sample size was calculated using statistical power analysis software G*Power 3.1 based on an assumed between-group effect size of 0.6 for changes in the Fugl-Meyer Assessment of the Lower Extremity (FMA-LE), with α = 0.05 and power = 0.80. To account for an anticipated 20% attrition rate, 80 participants were enrolled. Randomization was conducted in a 1:1 ratio using a computer-generated sequence prepared by an independent coordinator who was not involved in enrollment, treatment delivery, or outcome assessment. Allocation concealment was maintained using opaque, sequentially numbered envelopes. After baseline assessments were completed, envelopes were opened sequentially by treating therapists to reveal group assignment. Outcome assessors remained blinded to group allocation and did not participate in intervention delivery. At the end of the trial, assessors were asked to guess group assignment for each participant and to indicate confidence in their guesses, and blinding success was evaluated against chance performance¹³.

3. Standardized rehabilitation administered to both groups

All participants received standardized rehabilitation for 60 min/day over six consecutive days. To reduce inter-therapist variability and ensure reproducibility, the rehabilitation program followed a prespecified "menu + dosing + progression rules" structure applied identically in both groups. Core components included: (i) positioning and range-preserving management to reduce secondary complications; (ii) passive-to-active range-of-motion exercises; (iii) guided movement initiation and task-oriented practice aligned with early-stage motor recovery principles; and (iv) bed mobility and transfer training (bridging, rolling, sit-to-stand) with standing balance practice as tolerated. Exercise intensity was titrated to moderate perceived exertion, with 30-60 s rest intervals between sets. The detailed exercise items, dosing parameters (sets/repetitions), and progression criteria were prespecified for reproducibility and are provided in Supplementary Table 1¹⁴.

4. Foot needle-pricking intervention to elicit withdrawal and crossed extensor responses

Immediately after each standardized rehabilitation session, participants in the intervention group received a structured three-phase foot needle-pricking procedure. All treatments were performed in a quiet room maintained at 24°C ± 2°C. Participants were positioned supine with both knees slightly flexed over a soft bolster to reduce unintended limb stiffness and facilitate visual identification of reflex-related movement patterns.

5. Parameter rationale (dose and timing)

The stimulation parameters and treatment schedule were selected to balance reflex reliability, safety, and feasibility within an early inpatient rehabilitation workflow. A short treatment block (6 consecutive days) was chosen to align with a clinically pragmatic acute-to-subacute ward-based rehabilitation cycle and to capture early changes in reflex-related motor patterns while minimizing participant burden and attrition in a medically fragile population¹⁵.

Within each session, three cycles of the three-phase sequence were used to provide repeated sensorimotor input sufficient to elicit observable withdrawal-related and crossed extensor responses while limiting cumulative nociceptive exposure. A 1 s inter-prick interval and brief stimulus duration (<0.5 s) were applied to reduce rapid temporal summation of pain, allow discrete observation of each response, and reduce the likelihood of vasovagal reactions during repeated stimulation. The superficial insertion depth (2-3 mm) was selected to provide a consistent cutaneous nociceptive stimulus while avoiding deep tissue penetration, thereby minimizing bleeding and post-needling soreness¹⁶.

6. Infection control preparation and materials

Single-use sterile stainless-steel needles (0.25 mm × 13 mm) were used. The skin at intended stimulation sites was disinfected with 70% isopropyl alcohol and allowed to air-dry fully before stimulation. Clean gloves were worn throughout; contact with non-sterile surfaces required glove replacement before proceeding¹⁷.

1. Phase 1: Eliciting ipsilateral withdrawal-related flexion pattern on the affected sole (visual checkpoint)
   A brief superficial needle-pricking stimulus was delivered to the plantar region corresponding to the Yongquan area. The needle was inserted perpendicularly to a superficial depth of approximately 2-3 mm (dermis/subdermis). Each stimulus was brief (<0.5 s) and delivered three times at 1 s intervals. The visual checkpoint for a positive response was a coordinated flexion pattern involving the hip, knee, and ankle of the affected limb within approximately 2 s after stimulation. If the expected pattern was not observed, the stimulation point was adjusted slightly within the same plantar region, and one repeat attempt was permitted. Excessive searching across multiple points was avoided to limit unnecessary nociceptive exposure¹⁸.
2. Phase 2: Eliciting crossed extensor response via stimulation of the unaffected sole (visual checkpoint)
   Using the same superficial needling parameters (depth, timing, and repetition), stimulation was delivered to the sole of the unaffected foot while the affected limb was stabilized to reduce compensatory movement. The intended visual checkpoint was contralateral extension activity in the paretic leg (crossed extensor response), observed as a tendency toward knee extension and/or visible extensor engagement relative to baseline posture. If the response was ambiguous, it was documented as "uncertain" rather than prompting repeated stimulation.
3. Phase 3: Alternating dorsal foot stimulation during bridging (task-linked checkpoint)
   With both knees flexed, superficial stimulation was delivered alternately to the dorsal surfaces of both feet using the same timing parameters. Participants were then instructed to perform a gluteal bridge (pelvic elevation) and maintain the posture for approximately 10 s. Minimal manual assistance was permitted only for safe alignment and fall prevention, while active effort was encouraged as tolerated. The task-linked checkpoint was the ability to initiate pelvic elevation with observable proximal engagement without pain escalation or autonomic symptoms.

7. Session dose, documentation, discontinuation rules, and fidelity monitoring

The full three-phase sequence was repeated three times per session with short pauses between repetitions, resulting in a total intervention duration of approximately 8-10 min/day. During each session, the following were documented: (i) the number of stimulation events delivered per phase (including repeat attempts), (ii) whether expected reflex-related patterns were observed (withdrawal-related flexion, crossed extensor response, and bridge-related activation), (iii) participant-reported pain intensity (0-10 scale), and (iv) adverse signs (bleeding, bruising, dizziness, nausea, anxiety). The session was discontinued immediately if any of the following occurred: bleeding exceeding a pinpoint size or persistent bleeding after 30 s of compression, pain intensity >7/10, vasovagal symptoms (dizziness, pallor, sweating), acute anxiety/panic, or any new neurological complaint. All intervention sessions were supervised by a senior therapist, and adherence to the standardized procedure was monitored using a prespecified fidelity checklist; therapist training, competency checks, and procedural fidelity monitoring are summarized in Supplementary Table 2 (Therapist training and procedural fidelity for the needle-pricking intervention)¹⁹.

8. Safety warnings, emergency discontinuation, sharps disposal, and biohazard management

Needle-pricking carries risks of transient pain, minor bleeding, local bruising/hematoma, vasovagal reactions, and infection if aseptic technique is breached. Sterile single-use needles were used, and sites were disinfected before each stimulation. Minor bleeding was managed with gentle compression using sterile gauze until hemostasis, followed by site inspection and documentation. If dizziness or vasovagal symptoms occurred, stimulation was stopped immediately, the participant was maintained supine, vital signs were checked, and clinical staff were notified according to institutional emergency procedures. The procedure was not resumed on the same day after emergency discontinuation.

Used needles were discarded immediately into a puncture-resistant sharps container at the point of care. Contaminated gauze and materials were disposed of as biohazard waste according to institutional infection-control policies. Any needle-stick injury was managed under the hospital occupational exposure protocol (immediate wound cleansing and incident reporting)²⁰.

9. Outcome measures and assessment standardization

Primary outcomes were changes in Brunnstrom stage and FMA-LE total score, including subscores for reflex activity, flexor synergy, and extensor synergy. Secondary outcomes included active range of motion (AROM) of the hip, knee, and ankle; manual muscle testing (MMT); and Modified Ashworth Scale (MAS) scores for muscle tone. Assessments were performed at baseline (day 0), day 3, and day 6 by trained, blinded assessors using standardized procedures. AROM was measured with a universal goniometer using predefined anatomical landmarks, and the best value from two trials per joint was recorded. MMT was graded on a 0-5 scale under standardized positioning and resistance application. MAS scoring was performed during passive limb movement at approximately 90°/s²¹.

10. Statistical analysis

Data were analyzed using SPSS (version 26.0). Normality was tested using the Shapiro-Wilk test, and homogeneity of variances using Levene's test. Between-group comparisons at each time point were performed using independent-samples t-tests or Mann-Whitney U tests as appropriate, and within-group changes were assessed using paired t-tests or Wilcoxon signed-rank tests. Categorical variables were compared using Fisher's exact test. Effect sizes (Cohen's d for parametric tests and r for non-parametric tests) with 95% confidence intervals were reported. Associations between changes in FMA-LE total score and changes in synergy/reflex subscores were examined using Spearman's rank correlation. Statistical significance was set at P < 0.05 (two-tailed).

Results

General information
A total of 80 patients were enrolled and randomized 1:1 to the pricking group or the control group. Seventy-six participants completed the outcome assessments and were included in the analyses (pricking n = 38; control n = 38). Baseline characteristics, including age, sex, stroke type, disease duration, and hemiplegic side, were comparable between groups (all P > 0.05; Table 1).

Primary outcomes

Discussion

Stroke is a leading cause of long-term disability and mortality among non-communicable neurological diseases, and its sudden onset and recurrence risk impose substantial burdens on patients' quality of life^22,23. In the flaccid stage of hemiplegia, early restoration of reflex activity and emergence of movement-related output are clinically meaningful targets because voluntary motor control is minimal and opportunities for task practice are limited

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Acupuncture needle, sterile, stainless steel, 0.25 mm × 13 mm (single-use)	AguPunt (CTN)	SKU: A1090	Matches protocol needle specification for superficial plantar needle-pricking
Alcohol prep pad, 70% isopropyl alcohol, individually wrapped	embecta (BD brand)	326895	Skin antisepsis before needling
Biohazard waste bags, autoclavable	Fisherbrand	14-828-244	Regulated medical waste handling for contaminated disposables
Gauze sponges, sterile, 4 in × 4 in, 12-ply	McKesson Brand	16-4242	Local compression/hemostasis after minor bleeding
Nitrile examination gloves, powder-free	Ansell	TouchNTuff 92-600; Mfr. Part No. 92600090	PPE for needling and infection control
Sharps container (puncture-resistant), 1 qt (0.9 L)	BD	305635	Immediate disposal of used needles at point-of-use
Software: G*Power	Heinrich Heine University Düsseldorf (G*Power Team)	v3.1.9.7 (free software)	Sample size/power calculation in manuscript
Software: IBM SPSS Statistics	IBM	v26.0 (licensed software)	Statistical analyses in manuscript