The intervention will consist of Forest Therapy sessions, once a week for 12 consecutive weeks .

The Forest Therapy sessions will be held in the Tombolo di Cecina Biogenetic Nature Reserve during the first year and in the second year in the "Giardino Belora, Fiume Cecina" Protected Natural Area, Municipality of Riparbella (PI). Forest Therapy will consist of short, slow walks, intentionally without significant physical effort, along safe and easy trails, classified at the lower "Tourist" level on the Italian Alpine Club's trail difficulty scale, immersed in particularly valuable forest environments.

The control groups will consist of a cohort of fibromyalgia patients randomized-like the intervention groups-according to the following stratification factors: age (<50 vs. ≥50 years); baseline VAS score (<60 vs. ≥60 mm), to ensure maximum homogeneity with the intervention groups. The same measures as those required for intervention group participants will be performed on them. Compared to the intervention group, participants will not be required to modify their normal habits and activities.

Each session of Forest therapy will be organized as follows: 1. Gathering at the meeting point with the participants, doctor, psychologist, and staff.

2. Introduction of the psychologist and the planned activities - 5 minutes. 3. Administration of the STAI and POMS tests and preliminary physiological measurements - 30 minutes.

4. Beginning of the activity: request to turn off the phone and minimize verbal exchanges.

Slow walking - 5 minutes. Visual perception - 15 minutes. Slow walking - 5 minutes. Auditory perception - 15 minutes. Slow walking - 5 minutes. Tactile perception - 15 minutes. Slow walking - 5 minutes. Olfactory perception - 15 minutes. Slow walking - 5 minutes. Perceptual and movement activity chosen by the participant - 20 minutes. 5. Walk back to the starting/ending point - 20 minutes. STAI-S and POMS test and final physiological measurements - 30 minutes

Level of perceived pain assessed using the Visual Analog Scale (VAS), a validated gold standard for fibromyalgia and allowing for direct and comparable measurement. The Visual Analogue Scale is the most widely used method in medicine to measure the intensity of pain subjectively perceived by the patient. It is usually represented as a continuous line 10 centimetres long, the ends of which indicate two opposite conditions: left end (0): no pain ; right end (10): the worst pain imaginable. The patient fills in the instrument by making a mark on the line at the point corresponding to the pain he or she feels. The operator then measures the distance in millimetres (from 0 to 100) to obtain the score. Interpretation of the Scores (cut-off): based on various clinical studies, the values of the scale are generally divided into 4 ranges: 0 - 4 mm: no pain ; 5 - 44 mm: mild pain ; 45 - 74 mm: Moderate pain; 75 - 100 mm: Severe pain.

The Revised Fibromyalgia Impact Questionnaire (FIQR) is a self-assessment questionnaire used to measure the impact of fibromyalgia on quality of life.

The FIQR has 21 individual questions. All questions are based on an 11-point numeric rating scale of 0 to 10, with 10 being 'worst'. All questions are framed in the context of the past 7 days. The FIQR is divided into 3 linked sets of domains (symptoms, function and overall impact of the disease) and the final score (0-100) is obtained by summing the values of the 3 domains. Four severity categories and their corresponding cutoffs have been identified: remission if final score ≤30, mild if final score >30 and ≤45, moderate if final score >46 and ≤65, severe if final score >65. The study will evaluate the change in the score of the FIQR in the 2 arms.