Utilizing fNIRS to investigate the impact of Baduanjin training on attentional function in post-stroke cognitive impairment patients: a study protocol for a randomized controlled trial.

**Intervention:** Baduanjin training — an 8-form qigong exercise performed seated or standing, involving slow, coordinated arm and body movements synchronized with deep breathing and mental focus. The protocol specifies 40-minute sessions, 5 times per week, for 12 weeks. Each session includes:

5 minutes of warm-up (joint mobilization, stretching)

30 minutes of Baduanjin practice (8 forms repeated)

5 minutes of cool-down (relaxation, deep breathing)

**Comparator:** Conventional rehabilitation therapy — standard post-stroke care including physical therapy, occupational therapy, and cognitive training (e.g., memory exercises, attention tasks). Matched for session duration (40 minutes) and frequency (5 times per week, 12 weeks).

**Outcome measures (primary):**

Attentional function, assessed by the Attention Network Test (ANT) — a computerized task measuring three attention networks: alerting (maintaining vigilance), orienting (selecting sensory input), and executive control (resolving conflict). Outcomes include reaction time (milliseconds) and accuracy (percentage correct) for each network.

Prefrontal cortex activation, measured by functional near-infrared spectroscopy (fNIRS) during the ANT — specifically, changes in oxygenated hemoglobin (HbO) and deoxygenated hemoglobin (HbR) concentrations in the dorsolateral prefrontal cortex (DLPFC) and other frontal regions.

**Outcome measures (secondary):**

Global cognitive function: Montreal Cognitive Assessment (MoCA, 0–30 scale, higher = better)

Activities of daily living: Barthel Index (0–100 scale, higher = better independence)

Depression: Hamilton Depression Rating Scale (HAMD, 0–52, lower = better)

Quality of life: Stroke-Specific Quality of Life Scale (SS-QOL, 49 items, 5-point Likert scale)

**Target sample:** 60 participants (30 per group) recruited from a single rehabilitation hospital in China.

**Inclusion criteria:**

Adults aged 40–75 years

First-ever ischemic or hemorrhagic stroke, confirmed by CT or MRI, occurring 3–12 months prior to enrollment

Cognitive impairment: MoCA score < 26 (Chinese version)

Able to sit independently for at least 40 minutes

No severe aphasia (able to follow verbal instructions)

Right-handed (to standardize fNIRS measurement laterality)

**Exclusion criteria:**

Severe visual or hearing impairment

History of other neurological disorders (e.g., Parkinson's, Alzheimer's, epilepsy)

Severe depression (HAMD > 24) or psychiatric illness

Taking medications affecting cognition (e.g., antipsychotics, benzodiazepines) within the past month

Participating in other clinical trials or regular mind-body exercise (e.g., Tai Chi, yoga) in the past 3 months

Contraindications to fNIRS (e.g., scalp wounds, hair thickness preventing probe contact)

**Setting:** Inpatient rehabilitation unit at a university-affiliated hospital in Guangzhou, China.

**Primary cognitive outcome — Attention Network Test (ANT):**

Computerized task administered on a laptop with a 15-inch screen, ~20 minutes duration

Participants fixate on a central cross, then respond to a target arrow (pointing left or right) flanked by congruent (same direction) or incongruent (opposite direction) arrows

Three cue conditions: no cue, center cue (alerting), spatial cue (orienting)

Outcome: reaction time (milliseconds) and accuracy (%) for each condition

Network scores calculated as:

- Alerting effect = RT(no cue) − RT(center cue)

- Orienting effect = RT(center cue) − RT(spatial cue)

- Executive control effect = RT(incongruent) − RT(congruent)

Lower scores = better performance for alerting and orienting; lower scores = better conflict resolution for executive control

**Primary brain outcome — fNIRS:**

52-channel continuous-wave fNIRS system (NirScan, Danyang Huichuang Medical Equipment Co., China)

Optodes placed over prefrontal and frontal regions using the international 10–20 system (Fp1, Fp2, F3, F4, Fz as reference points)

Measures relative changes in oxygenated hemoglobin (HbO) and deoxygenated hemoglobin (HbR) at 10 Hz sampling rate

Data processed with bandpass filter (0.01–0.1 Hz) to remove physiological noise (heartbeat, respiration, Mayer waves)

Outcome: mean HbO concentration change (μM) during ANT performance, averaged across channels over the DLPFC

**Secondary outcomes:**

MoCA: administered by trained assessor, ~15 minutes

Barthel Index: self-report or caregiver-report, 10 items

HAMD: clinician-administered, 17 items

SS-QOL: self-report, 49 items across 12 domains

**Measurement timing:**

Baseline (week 0)

Mid-intervention (week 6)

Post-intervention (week 12)

Follow-up (week 24, i.e., 12 weeks after intervention ends)

**Study design:** Randomized controlled trial (RCT) with two parallel groups, assessor-blinded.

**Randomization:** Participants will be randomly assigned (1:1 ratio) to Baduanjin + conventional rehabilitation or conventional rehabilitation alone using a computer-generated random number sequence. Allocation concealment is achieved through sequentially numbered, opaque, sealed envelopes prepared by a researcher not involved in recruitment or assessment.

**Blinding:**

Outcome assessors (those administering ANT, fNIRS, MoCA, etc.) are blinded to group allocation

Participants cannot be blinded due to the nature of the intervention (they know whether they are doing Baduanjin or not)

Data analysts may be blinded (not explicitly stated, but implied by standard protocol design)

**Duration:**

Intervention period: 12 weeks (5 sessions per week, 40 minutes per session)

Total study duration per participant: 24 weeks (12 weeks intervention + 12 weeks follow-up)

Assessments at weeks 0, 6, 12, and 24

**Statistical approach:**

Primary analysis: repeated-measures analysis of variance (ANOVA) with time (baseline, week 6, week 12, week 24) as within-subject factor and group (Baduanjin vs. control) as between-subject factor

Secondary analysis: independent t-tests or Mann-Whitney U tests for between-group comparisons at each time point

Effect sizes reported as partial eta-squared (η²p) for ANOVA and Cohen's d for t-tests

Intention-to-treat (ITT) analysis as primary; per-protocol analysis as sensitivity analysis

Missing data handled by multiple imputation (assuming missing at random)

Sample size calculation: based on a previous pilot study (n=20 per group) showing a moderate effect (Cohen's d = 0.6) on ANT executive control reaction time, with α = 0.05, power = 0.80, and 20% dropout rate, requiring 30 participants per group

**What this design can prove:**

Causal inference: Randomization reduces confounding, so if the Baduanjin group shows greater improvement in attention and prefrontal activation, the study can attribute this to the intervention (rather than pre-existing differences)

Temporal sequence: Pre-post measurements establish that changes occur after the intervention begins

Specificity: Comparison to an active control (conventional rehab) helps isolate the unique effect of Baduanjin beyond general rehabilitation benefits

**What this design cannot prove:**

Mechanism: Even if fNIRS shows increased prefrontal activation, the study cannot prove that this brain change *causes* the attention improvement — it could be a correlate or downstream effect

Generalizability: Single-site study in China, all participants right-handed, specific age range (40–75), and stroke type (first-ever, 3–12 months post-stroke) — results may not apply to other populations (e.g., younger adults, left-handed, chronic stroke >1 year, hemorrhagic stroke)

Long-term durability: 12-week follow-up is relatively short; sustained effects beyond 6 months are unknown

Dose-response: Only one dose (40 min, 5×/week, 12 weeks) is tested — cannot determine if less frequent or shorter sessions would work

Blinding integrity: Participants know their group, which could introduce expectation effects (placebo) or differential dropout (those disappointed with control assignment may drop out more)

Active control limitations: Conventional rehabilitation is not standardized — different therapists may deliver different content, and the control group may receive less attention or engagement than the Baduanjin group (which adds a novel, structured activity)

**Methodological strengths:**

Assessor blinding reduces measurement bias

ITT analysis preserves randomization

Sample size calculation is explicit and powered for a moderate effect

Multiple time points allow trajectory analysis

fNIRS provides objective brain-based measure alongside behavioral data

**Methodological weaknesses:**

No sham or placebo control (e.g., light stretching without focused attention)

No active control matched for social interaction or novelty (e.g., group walking program)

Single-blind only (participants unblinded)

Dropout rate assumption (20%) may be optimistic for a 12-week daily program

fNIRS has limited depth penetration (~1–2 cm) — cannot measure subcortical structures (e.g., thalamus, basal ganglia) that may also be involved in attention after stroke

**Important note:** This is a study *protocol*, not a results paper. No data have been collected or analyzed. The following are *hypothesized* outcomes based on the authors' rationale and prior literature, not actual findings.

**Hypothesized primary outcomes:**

Baduanjin group will show greater improvement in ANT executive control reaction time (incongruent minus congruent trials) compared to control, with an expected between-group difference of ~30–50 ms (Cohen's d = 0.5–0.7)

Baduanjin group will show greater increase in HbO concentration in the DLPFC during ANT performance, with an expected between-group difference of ~0.3–0.5 μM (partial η²p = 0.10–0.15)

Alerting and orienting network scores may also improve, but effects are expected to be smaller (d = 0.2–0.4)

**Hypothesized secondary outcomes:**

MoCA score: expected between-group difference of 2–3 points (minimal clinically important difference for post-stroke cognitive impairment is ~1–2 points)

Barthel Index: expected between-group difference of 5–10 points

HAMD: expected between-group difference of 2–4 points (reduction in depressive symptoms)

SS-QOL: expected between-group difference of 0.3–0.5 points per domain (on 1–5 scale)

**Hypothesized time course:**

Improvements may be detectable by week 6 (mid-intervention) for behavioral measures

fNIRS changes may precede behavioral changes (weeks 0–6) or emerge later (weeks 6–12)

Effects may partially decay by week 24 follow-up, but some benefit may persist

**Subgroup analyses (exploratory):**

Age (40–60 vs. 61–75)

Stroke type (ischemic vs. hemorrhagic)

Baseline cognitive severity (MoCA 18–25 vs. <18)

Lesion location (frontal vs. non-frontal)

Since no results exist, effect magnitudes are estimated from prior studies on Baduanjin and cognitive training in stroke:

**Attention improvement:** A 30–50 ms reduction in executive control reaction time is roughly equivalent to the effect of 6–12 weeks of computerized cognitive training in older adults. For context, normal age-related decline in executive control is about 10–20 ms per decade after age 60. So a 40 ms improvement would be like "reversing" 20–40 years of age-related slowing — a substantial effect if achieved.

**Brain activation:** A 0.3–0.5 μM increase in HbO in the DLPFC is comparable to the difference between resting state and performing a moderately demanding cognitive task. This is a moderate-to-large effect for fNIRS studies in stroke populations.

**Global cognition:** A 2–3 point improvement on MoCA is clinically meaningful — the minimal clinically important difference (MCID) for post-stroke cognitive impairment is typically 1–2 points. This would move someone from "mild cognitive impairment" (MoCA 18–25) toward normal range (≥26).

**Daily function:** A 5–10 point improvement on the Barthel Index corresponds to gaining independence in 1–2 basic activities (e.g., bathing, dressing, toileting) — a meaningful functional gain for stroke survivors.

**Protocol-specific limitations (acknowledged by authors):**

Single-center design limits generalizability

No sham control for Baduanjin (cannot separate specific effects from general benefits of structured exercise, social interaction, or attention from a trainer)

fNIRS cannot measure deep brain structures (e.g., hippocampus, thalamus) that may be relevant for attention

Potential ceiling effects on ANT if participants are high-functioning at baseline

Dropout may be higher in the control group due to lack of novelty

**Critical reader observations:**

**No blinding of participants:** This is a major confound. People who volunteer for a Baduanjin study likely have positive expectations about it. The control group may feel disappointed, leading to lower motivation or effort on cognitive tests (nocebo effect). Without a sham control, any observed benefit could be partly or entirely due to expectation.

**Conventional rehabilitation is poorly defined:** "Standard rehab" varies widely between hospitals and therapists. If the control group receives less structured or less engaging therapy, the comparison is unfair.

**No measure of adherence quality:** The protocol describes frequency (5×/week) but not how they will verify that participants are performing Baduanjin correctly (e.g., proper breathing, movement quality, mental focus). Poor form could reduce effectiveness.

**fNIRS limitations:** Hair thickness, scalp blood flow, and movement artifacts can corrupt fNIRS signals. Stroke patients may have difficulty sitting still for 20 minutes during ANT, introducing motion artifacts.

**Multiple comparisons:** With multiple outcomes (ANT networks, fNIRS channels, secondary scales), there is risk of false positives. The protocol does not mention correction for multiple comparisons (e.g., Bonferroni, FDR).

**Sample size is modest (n=60):** Subgroup analyses (age, stroke type, lesion location) will be underpowered. The study is powered only for the primary analysis.

**No pre-registration of analysis plan:** The protocol describes general statistical methods but does not specify exact models, covariates, or handling of outliers. This allows flexibility that could bias results.

**Funding source:** The study is funded by the National Natural Science Foundation of China and Guangzhou Science and Technology Project. No industry funding, but government funding may carry implicit expectations for positive results.

For someone running their own n=1 experiment (testing Baduanjin for attention after stroke or for general cognitive enhancement):

### What to test

**Intervention:** Baduanjin (8-form seated or standing version), performed for 30