Chronic muscle pain is one of the most prevalent clinical challenges in sports medicine, significantly affecting training capacity, competitive performance, and quality of life in athletes. The endocannabinoid system has emerged as a promising therapeutic target for pain modulation in the sports context. This prospective, comparative, non-randomized observational study aims to evaluate whether adjuvant topical application of a cannabinoid balm (CBD:THC 3:1 - Papa \& Barkley) provides additional reduction in chronic muscle pain intensity in athletes, compared to systemic CBD oil alone, over 90 days of follow-up in a real-world clinical practice setting. Sixty adult athletes (amateur or professional) with established chronic muscle pain (≥3 months) who receive clinical indication for cannabinoid therapy will be followed in two observational cohorts: Cohort A (n=30), receiving only systemic CBD oil (60 mg/day oral/sublingual), and Cohort B, (n=30) receiving systemic CBD oil plus the topical cannabinoid balm (CBD:THC 3:1, applied twice daily to the affected muscle area). Treatment allocation is based exclusively on the clinical decision of the principal investigator, reflecting routine medical practice. The primary outcome is the change in Brief Pain Inventory (BPI) scores from baseline (D0) to end of follow-up (D90). Secondary outcomes include pain intensity (NRS), sleep quality (PSQI), quality of life (SF-36), perceived muscle recovery (TQR scale), functional capacity (LEFS/UEFI), rescue analgesic use, and safety/tolerability of the topical formulation. The study aims to generate real-world evidence on the effectiveness and safety of adjuvant topical cannabinoid therapy in athletes with chronic muscle pain in the Brazilian clinical practice setting.
BACKGROUND: Chronic muscle pain affects up to 70% of amateur and professional athletes over 12 months, with 7-day prevalence rates of approximately 32.8%. Conventional pharmacological therapies (NSAIDs, muscle relaxants, opioids) frequently provide inadequate relief and are associated with limiting systemic adverse effects. The endocannabinoid system (ECS) has emerged as a promising therapeutic target, with CB1 and CB2 receptors playing key roles in nociceptive modulation and neuroinflammation attenuation. Topical cannabinoid administration offers the advantage of delivering high concentrations directly to peripheral receptors (CB1, CB2, and TRPV1) in nerve endings and immune cells of the skin and underlying muscle tissue, while minimizing systemic absorption. The combination of CBD and THC in a 3:1 ratio may maximize synergistic therapeutic effects (entourage effect) while mitigating psychotropic adverse effects. STUDY DESIGN: This is a prospective, comparative, non-randomized observational study with 90 days of follow-up per participant. Treatment allocation is based exclusively on the principal investigator's clinical decision, reflecting routine medical practice. POPULATION: 60 adult athletes (amateur or professional) practicing structured physical activity (≥3 sessions/week) for at least 6 months, with clinically confirmed chronic muscle pain (≥3 months duration), including myofascial pain syndrome, recurrent persistent DOMS, or pain from overtraining/repetitive microtrauma. INTERVENTIONS OBSERVED: Cohort A (Control, n=30): Full spectrum CBD oil, 60 mg/day, oral/sublingual, once daily at bedtime, for 90 days. Cohort B (Intervention, n=30): Full spectrum CBD oil (same as Cohort A) PLUS Papa \& Barkley Topical Balm (450 mg CBD + 150 mg THC per 50 mL bottle; 9 mg CBD + 3 mg THC per mL), applied twice daily (every 12 hours) to the affected muscle area for 90 days. ASSESSMENTS: Evaluations at D0 (baseline), D7, D14, D30, D60, and D90 using validated instruments including BPI, NRS (0-10), PSQI, SF-36, TQR scale, LEFS/UEFI, rescue analgesic quantification, and structured adverse event reporting. STATISTICAL ANALYSIS: Mixed-effects models for repeated measures (MMRM) or Generalized Estimating Equations (GEE) will be used. Propensity score matching may be employed to mitigate confounding bias. Pre-specified subgroup analyses by sport modality, pain location, competitive level, and training volume. ETHICS: The protocol will be submitted to the Research Ethics Committee (CEP) via Plataforma Brasil, following CNS Resolutions 466⁄2012 and 510⁄2016. Results will be reportedfollowing STROBE guidelines for observational studies.
Study Type
OBSERVATIONAL
Enrollment
60
Change in Chronic Muscle Pain Intensity and Interference (Brief Pain Inventory)
Change in Brief Pain Inventory (BPI) scores - pain intensity dimension (worst, least, average, current pain on 0-10 scale) and pain interference dimension (7 items on 0-10 scale assessing interference with general activity, mood, walking, work, relations, sleep, and enjoyment of life) - from baseline (D0) to end of follow-up (D90). Higher scores indicate worse pain/interference. A clinically meaningful change is defined as ≥2 points reduction in pain intensity.
Time frame: From baseline (Day 0) to end of follow-up (Day 90)
Pain Intensity (Numeric Rating Scale)
Pain intensity measured by the Numeric Rating Scale (NRS 0-10), where 0 = no pain and 10 = worst imaginable pain. Assessed at D0, D7, D14, D30, D60, and D90.
Time frame: From baseline (Day 0) to Day 90, with assessments at Days 7, 14, 30, 60, and 90
Sleep Quality (Pittsburgh Sleep Quality Index - PSQI)
Sleep quality measured by the Pittsburgh Sleep Quality Index (PSQI). The PSQI is a self-report questionnaire assessing sleep quality over a 1-month interval, consisting of 19 items creating 7 components producing a global score (0-21). Scoring: 0-5 = good sleep quality; 6- 10 = poor sleep quality; 11-21 = sleep disorder indication. Lower scores indicate better sleep quality.
Time frame: From baseline (Day 0) to Day 90, with assessments at Days 30, 60, and 90
Quality of Life (SF-36)
Health-related quality of life measured by the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36). The SF-36 assesses 8 physical and mental health domains, scored from 0 (worst health) to 100 (best health). Higher scores indicate better quality of life.
Time frame: From baseline (Day 0) to Day 90, with assessments at Days 30, 60, and 90
Perceived Muscle Recovery (Total Quality Recovery - TQR Scale)
Perceived muscle recovery measured by the Total Quality Recovery (TQR) scale of Kenttä \& Hassmén. The TQR is a single-item scale (6-20) that assesses the athlete's perceived recovery status. Higher scores indicate better perceived recovery (6 = very, very poor recovery; 20 = very, very good recovery).
Time frame: From baseline (Day 0) to Day 90, with assessments at Days 7, 14, 30, 60, and 90
Sports Functional Capacity (LEFS/UEFI)
Sports functional capacity measured by the Lower Extremity Functional Scale (LEFS) or Upper Extremity Functional Index (UEFI), according to pain location. LEFS: 0-80 scale (higher = better function). UEFI: 0-80 scale (higher = better function).
Time frame: From baseline (Day 0) to Day 90, with assessments at Days 30, 60, and 90
Safety and Tolerability (Adverse Events)
Structured recording of local and systemic adverse events, classified by severity (mild, moderate, severe) and causal relationship (definite, probable, possible, unlikely, unrelated). Includes monitoring of local skin reactions (dryness, erythema, pruritus, rash) and systemic effects (somnolence, diarrhea, nausea, appetite changes).
Time frame: From Day 7 to Day 90, with continuous monitoring and assessments at Days 7, 14, 30, 60, and 90
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