The aim of the study is to present the quantitative differences in oxygenated hemoglobin in different cohorts.

This clinical study evaluates whether there is a correlation between measurements using multispectral optoacoustic tomography and the results of spiroergometry in the context of performance diagnostics.

This study aims to investigate the muscle metabolism of athletes (endurance and strength athletes), PAD patients, and healthy control subjects using non-invasive multispectral optoacoustic tomography as part of interval treadmill spiroergometry. The aim is to take a closer look at changes in oxygen supply and muscle metabolism in the various patient groups during the recovery phase. To this end, the individual groups will perform a performance diagnosis on a treadmill spiroergometer, adapted to their respective estimated physical performance (in the case of PAD patients, taking into account the possibilities given by the disease), which will be carried out in the form of a step test. In addition, MSOT measurements will be taken between the individual steps.

The aim of this study is to use MSOT to visualize and compare the muscle perfusion-in particular the proportion of oxygenated and deoxygenated hemoglobin (Hb)-of the various cohorts, as well as to compare it with the diagnostics and methods commonly used to date and identify any advantages. In the future, this could contribute to a better understanding of muscle perfusion, especially in connection with diseases such as PAD or other muscle lesions in sports medicine.

Inclusion Criteria:

• Age ≥ 18 years (adults capable of giving consent)
• Capacity to consent. The subjects are able to understand the information provided and give their written consent.
• Belonging to one of the following cohorts:
• Endurance athletes: at least 3× per week ≥ 60 minutes of intensive endurance training (e.g., running, cycling, swimming)
• Strength athletes: at least 3× per week ≥ 60 minutes of intensive strength training without additional endurance training
• Healthy control subjects: less than 2× per week < 30 minutes of physical activity, no known vascular diseases
• PAD patients: diagnosed peripheral arterial occlusive disease in Fontaine stage I or IIa Women of childbearing age with or without contraception may participate, as there are no risks of harm to the fetus.
• Consent to pseudonymized data collection and storage in accordance with the GDPR.

Exclusion Criteria:

• Age over 75 years
• Minors (Age < 18)
• safety concerns on the part of the study physician, e.g., in the case of of: physical, mental or psychiatric illnesses, acute or chronic conditions that could jeopardise safety or data quality
• Taking medications that could affect physical performance or physiological measurements (e.g., heart rate, oxygen uptake).
• Pregnancy with known risks or complications (participation is possible in principle, but subject to individual medical review).
• Refusal to participate or lack of informed consent.

The study will include adult participants aged 18 to 75 years, representing different levels of physical activity and vascular health status. A total of approximately 60 participants will be recruited, divided into six cohorts of about ten individuals each.

Cohort Description:

• Young endurance athletes (≥ 3 times per week, ≥ 60 minutes per session) Examples: running, cycling, swimming
• Young strength athletes (≥ 3 times per week, ≥ 60 minutes) No additional endurance training
• Young healthy controls Less than 2 times per week and < 30 minutes of physical activity No known vascular or muscular diseases
• Patients with peripheral arterial disease (PAD) Diagnosed with PAD, Fontaine stage I, IIa or IIb
• Older inactive controls Age above 55 years, no regular physical activity, no pAVK
• Patients with PAD (Fontaine stage I, IIa or IIb, who participate in structured walking training