The goal of this clinical trial is to investigate the effect of breathing on the processing of experimental pain in healthy participants. The main questions are:

1. Does breathing rate influence the spatial extent of thermally induced secondary hyperalgesia, a proxy of central sensitization?
2. Does resonance frequency breathing influence the autonomic nervous system, compared to baseline and compared to paced breathing at a natural frequency?
3. Is spinal excitability, measured using the magnitude of the nociception withdrawal reflex (NWR), affected by resonance frequency breathing, compared to paced breathing at a natural frequency?

Participants:

• will receive heat stimuli
• 's skin's sensitivity will be tested using quantitative sensory testing tools.
• will receive various instructions on the speed of their breathing
• 's heart rate, respiratory rate and sweat response will be measured
• will fill in questionnaires

Researchers will compare the spatial extent of sensitivity resulting from application of heat stimuli during paced resonance frequency breathing compared to paced breathing at a natural frequency to see if the breathing rhythm influences central sensitization processes.

Inclusion Criteria:

1. over 18 and below 40 years of age
2. good general health
3. able to give informed consent

Exclusion Criteria:

1. any major medical or psychiatric condition (e.g. heart disease, diabetes, autoimmune disorders, infectious diseases, major depressive disorder), any chronic pain condition, any respiratory problems, any current acute pain at time of study
2. inability to follow study instructions, e.g. due to language problems
3. Consumption of alcohol, drugs, analgesics within the last 24 h
4. Consumption of no more than 100 mg of caffeine within the last 8 h
5. Scar tissue or generally reduced sensitivity in the designated testing site areas

Additional exclusion criteria for experiments 3 and 4

1. Shoe size < 38
2. Restless-Legs-Syndrome