This study aims to evaluate the immediate hemodynamic effects of transcutaneous electrical nerve stimulation (TENS) on the popliteal artery and vein. Vascular issues like PAOD and DVT are common in patients with diabetes, obesity, or immobility due to increased resistance and reduced blood flow. Traditional treatments (medication or surgery) are not always feasible, prompting interest in TENS as an alternative. Although primarily used for pain relief, TENS may enhance blood flow. This research compares different stimulation frequencies (80 Hz vs. 4 Hz) and sites (gastrocnemius muscle vs. thoracolumbar sympathetic ganglia) to identify the most effective configuration.

Inclusion Criteria:

1. Healthy people
2. Age: 18 years and above (inclusive)
3. Body mass index (BMI) between 18.5 and 24

Exclusion Criteria:

1. Unable to complete two interventions within a week
2. Have contraindications to electrotherapy (for example: metal implants in the body, open wounds, pregnancy, sensory loss)
3. Obvious varicose veins 4. Unable to lie down for about 1 to 2 hours 5. Taking drugs or nutritional supplements that affect autonomic nervous activity or vasodilation (for example: Ginkgo biloba) 6. Smoking 7. Ankle and Ankle Index (ABI) less than 0.9 or greater than 1.3