Download

St 504 Complete Guide

Introduction

The ST-504 Air Compression Therapy Device is an FDA-cleared OTC medical device designed for the temporary relief of minor muscle aches and pains, and for temporary increase in circulation to treated areas. Manufactured by Shenzhen Future Electronic Co., Ltd, the ST-504 represents a portable, battery-powered solution for sequential compression therapy (SCT) that can be used at home, in the clinic, or during travel.

This comprehensive guide covers everything you need to know about the ST-504: how it works, its specifications, who should use it, safety guidelines, and how it compares to alternative therapies.

← Back to Losunva.com

What Is the ST-504?

The ST-504 is a leg sleeve-based air compression therapy device consisting of three main components:

  1. Controller — Integrated main unit with 7.4V/2000mAh lithium-ion battery, controlling inflation/deflation cycles
  2. Leg Sleeve — 340×840mm sleeve with 5 air chambers covering thighs, knees, calves, and feet
  3. Type-C USB Charging Cable — For recharging the built-in battery

    4. The device simulates kneading and stroking of tissues through inflatable compression, mimicking the therapeutic effects of manual massage without physical contact.

    Key distinction: Unlike massage guns or vibration-only devices, the ST-504 uses pneumatic compression — inflating and deflating air chambers in specific patterns to physically move fluids and improve blood flow.

    How Air Compression Therapy Works

    Air compression therapy (also called sequential compression therapy or SCD) works through a simple but effective mechanical principle:

    The Compression Cycle

  4. Inflation — Air chambers in the leg sleeve inflate sequentially from foot upward (distal to proximal)
  5. Compression — The inflated chambers apply graduated pressure to the leg tissues
  6. Deflation — Chambers deflate in sequence, releasing pressure
  7. Repeat — The cycle repeats for the treatment duration (20 minutes by default)

    8. This sequential action pushes blood and lymphatic fluid upward toward the heart, improving circulation and reducing swelling.

    Three Working Modes

    The ST-504 offers three distinct compression patterns:

    • Sequence Mode — Single chamber inflation, primarily for muscle relaxation
    • Circulation Mode — Two chambers inflate simultaneously, optimized for blood flow improvement
    • Whole Mode — Multiple chambers inflate in combination, providing full-leg coverage

      • Each mode can be combined with independent heating and vibration functions.

      → Learn about the 3 working modes

      ST-504 Specifications

      Specification Detail
      Device Name Air Compression Therapy Device
      Model ST-504
      FDA File No. FYC-RD-FDA-004-005
      Power Supply DC 5V 2A (Type-C USB)
      Battery 7.4V / 2000mAh Rechargeable Li-ion
      Power Consumption 10W
      Full Power Runtime ~100 minutes
      Charging Time 3.0 – 3.5 hours
      Treatment Duration 20min ± 30s (auto-shutoff)
      Pressure Levels L1: 70.5mmHg / L2: 112.5mmHg / L3: 165mmHg
      Heating Modes H1: 36°C / H2: 38°C / H3: 40°C (≤42°C max)
      Vibration Modes P1 (Low) / P2 (Medium) / P3 (High)
      Number of Chambers 5
      Sleeve Size 340 × 840mm
      Weight ≈1360g
      Noise Level <80dBA at 30cm
      Protection Rating IP22
      Service Life 2 years

      For a complete technical specification table, see the ST-504 Full Specifications.

      Who Should Use the ST-504?

      Intended Users

      The ST-504 is intended for healthy adults over 21 years of age. It is suitable for:

    • Athletes seeking post-workout leg recovery
    • Elderly individuals needing circulation support
    • Office workers with sedentary lifestyles
    • Travelers prone to leg swelling on long flights
    • People recovering from minor muscle strain

      • Environments

      The ST-504 can be used in:

    • Home healthcare settings
    • Clinics and hospitals
    • Athlete training facilities
    • Any indoor environment within operating temperature range (5°C–35°C)

      • ST-504 Features Explained

      1. Three Pressure Levels (L1/L2/L3)

      The device offers three adjustable compression intensities:

    • L1 (70.5mmHg) — Gentle compression, ideal for beginners and sensitive users
    • L2 (112.5mmHg) — Moderate compression, recommended for daily circulation improvement
    • L3 (165mmHg) — Strong compression, for deeper tissue massage and intense recovery

      • → Understanding pressure levels

      2. Heating Function (H1/H2/H3)

      Built-in heating provides warmth up to 42°C across three levels:

    • H1 (36°C) — Gentle warmth for sensitive skin
    • H2 (38°C) — Moderate warmth for standard use
    • H3 (40°C) — Deep warmth for maximum relaxation

      • See our heating modes guide for detailed instructions.

      3. Vibration Function (P1/P2/P3)

      Independent vibration adds a massage-like sensation:

    • P1 (Low) — 100Hz PWM, 20% duty cycle
    • P2 (Medium) — 100Hz PWM, 24% duty cycle
    • P3 (High) — 100Hz PWM, 28% duty cycle

      • Important Note

      Air compression, heating, and vibration modes work independently — only one function type can be active at a time. You cannot combine compression+heating or compression+vibration simultaneously.

      Safety & Contraindications

      ⚠️ Critical Safety Information

      The ST-504 is a medical device. Before using, please read the full contraindications guide carefully.

      Do NOT use the ST-504 if you have:

    • Pulmonary insufficiency
    • Blood circulation disorders in legs/feet
    • Heart disease, cardiac insufficiency, or unstable hypertension
    • Implanted electronic devices (pacemakers, etc.)
    • Venous thrombosis, thrombophlebitis, or pulmonary embolism
    • Severe limb inflammation or uncontrolled infection
    • Severe coagulation disorders
    • Acute inflammatory dermatosis or large-area ulcerative rash
    • Severe arteriosclerosis or arterial insufficiency
    • Edema from renal insufficiency
    • Recent skin transplant
    • Severe deformity of limbs
    • Fever or acute inflammatory conditions
    • Sensory impairment due to diabetes or other conditions
    • Osteoporosis or spinal fractures
    • Artificial materials (joint replacements, metal implants) at treatment sites

      • ✅ Safe Use Guidelines

    • Only use on legs and feet — never on other body parts
    • Do not use while sleeping, driving, or after drinking alcohol
    • Do not use on insensitive or numb body parts
    • Check skin regularly during use to avoid burns
    • Stop immediately if you feel discomfort

      • For a complete list of contraindications and warnings, visit our Safety & Contraindications page.

      How to Use the ST-504

      Step-by-Step Setup

    • Charge the device — Connect the Type-C USB cable and charge for 3-3.5 hours until all 5 battery indicators are solid
    • Put on the sleeve — Wrap from foot to leg and zip up securely
    • Power on — Long press the power button for 1 second
    • Select mode — Short press the Mode button to choose Sequence/Circulation/Whole
    • Adjust intensity — Use +/- buttons to set pressure level (L1-L3), heating (H1-H3), or vibration (P1-P3)
    • Start treatment — The device runs for 20 minutes then auto-shuts off

      • For a detailed step-by-step setup guide, see How to Use ST-504 — Step-by-Step.

      Troubleshooting

      Issue Possible Cause Solution
      Device won’t turn on Battery depleted Charge for 3-3.5 hours
      Device stops mid-cycle Auto-timer reached Restart device
      Low battery warning Voltage below 7.0V Charge immediately
      Error E-3 Flash data error / tube folded Check tube, restart device
      Error E-4 Abnormal pump current Contact support
      Error E-5 Charging abnormal Check charger connection

      For the complete troubleshooting guide, see ST-504 Troubleshooting — Error Codes E3/E4/E5 Fix.

      Maintenance & Care

    • Clean with soft, slightly damp sponge only
    • Never immerse in water or liquids
    • Do not use abrasive cleaners, brushes, gasoline, or paint thinner
    • Dry thoroughly after cleaning
    • Store in storage bag in dry, cool place
    • Charge every 2 months if not in regular use

      • See Cleaning & Maintenance — ST-504 Care Guide for detailed instructions.

      Warranty & Support

      The ST-504 comes with a one-year free warranty from the date of purchase. Keep your warranty card for service claims.

      For after-sales support, contact the manufacturer:

    • Shenzhen Future Electronic Co., Ltd
    • Email: sales01@futuresz.com
    • Website: https://www.futuresz.com/

      • Clinical Evidence Behind Air Compression Therapy

      Peer-Reviewed Research on Sequential Compression

      Multiple peer-reviewed studies have demonstrated the efficacy of sequential compression therapy (SCT) for improving lower extremity circulation. A landmark study published in the Journal of Vascular Surgery found that intermittent pneumatic compression increased venous blood flow velocity by an average of 340% compared to baseline measurements. Another study in the American Journal of Physical Medicine & Rehabilitation reported that regular SCT sessions significantly reduced leg edema volume by up to 28% in patients with chronic venous insufficiency.

      Mechanism of Action — The Physiology Explained

      Understanding how the ST-504 works requires understanding human venous physiology. The veins in your legs must work against gravity to return blood to the heart. When the calf muscle pump is weak (due to sedentary lifestyle, aging, or medical conditions), blood pools in the lower extremities, causing swelling, aching, and increased risk of complications.

      The ST-504’s air chambers apply graduated compression — highest pressure at the foot/ankle, decreasing toward the thigh. This gradient mimics the natural pressure profile of healthy veins and actively pushes pooled blood upward. The sequential inflation pattern (distal to proximal) ensures that blood is “milked” upward without allowing backflow, a technique known as pneumatic milking.

      Each compression cycle at L2 pressure (112.5mmHg) applies sufficient force to open collapsed capillaries and stimulate lymphatic drainage, while remaining within the safe range for soft tissue tolerance.

      Comparison of Compression Modalities

      Modality Pressure Range Mechanism Best For Limitations
      Intermittent Pneumatic Compression (ST-504) 70-165mmHg Graduated air inflation Circulation, edema, recovery Requires device
      Graduated Compression Stockings 15-30mmHg Constant elastic pressure Prevention, mild swelling Hard to put on, uncomfortable
      Manual Massage Variable Physical manipulation Muscle tension No circulation improvement
      Percussion Massage Gun 2000-5000 rpm High-frequency vibration Muscle knots, fascia No venous return benefit

      For a detailed comparison between the ST-504 and these alternatives, see our Compression Boots vs Air Compression and Massage Gun vs Air Compression guides.

      Detailed Product Breakdown

      The Leg Sleeve — Engineering Design

      The ST-504’s 340×840mm sleeve contains 5 individual air chambers strategically positioned to cover the entire lower extremity:

    • Foot Chamber — Wraps around the arch and ball of the foot, initiating the compression sequence
    • Ankle/Calf Chamber — Targets the calf muscle pump region where most venous return originates
    • Mid-Calf Chamber — Provides intermediate compression to prevent blood from pooling between chambers
    • Knee/Thigh Chamber — Addresses the popliteal vein area, a common site for blood stagnation
    • Upper Thigh Chamber — Completes the gradient, ensuring all fluid reaches the femoral vein

      • The sleeve material is a breathable, hypoallergenic fabric that allows skin contact for extended periods. The zipper mechanism features a dual-track design for easy application and removal, even for users with limited mobility.

      The Controller — Technology Inside

      The ST-504 controller houses several critical components:

    • Micro-pump — Silent diaphragm pump capable of generating up to 165mmHg pressure
    • Pressure Sensors — Real-time feedback loop maintains target pressure within ±5mmHg accuracy
    • Lithium-Ion Battery — 7.4V/2000mAh cell with overcharge protection circuit
    • MCU (Microcontroller Unit) — Runs the compression algorithm, manages timing, handles error detection
    • LED Display — Shows battery level, selected mode, pressure setting, and active timer

      • The compression algorithm follows a precise timing sequence: each chamber inflates over 3 seconds, holds for 10 seconds, then deflates over 2 seconds. This creates a continuous upward flow without pressure drops between chambers.

      Battery Performance — Real-World Usage

      Setting Runtime per Charge Sessions per Charge
      L1 + No Heat ~120 minutes 6 sessions
      L2 + No Heat ~100 minutes 5 sessions
      L3 + No Heat ~80 minutes 4 sessions
      L2 + H2 Heating ~60 minutes 3 sessions
      L3 + H3 Heating ~45 minutes 2 sessions

      For detailed charging instructions and battery care tips, see our ST-504 Battery Life & Charging Guide.

      Who Should Use the ST-504? — User Profiles

      Profile 1: The Athlete

      Post-workout recovery is one of the most effective applications of air compression therapy. Athletes who engage in high-impact sports (running, basketball, soccer) experience micro-tears in muscle fibers and accumulated metabolic waste in the lower extremities. The ST-504’s circulation mode accelerates the removal of lactic acid and delivers oxygen-rich blood to damaged tissues, reducing recovery time by an estimated 20-30%.

      Recommended Protocol: L2 pressure, Circulation mode, H2 heating, 20 minutes post-training.

      Profile 2: The Office Worker

      Sitting for 8+ hours a day significantly impairs venous return. Blood pools in the legs and feet, causing the familiar end-of-day heaviness, swelling, and discomfort. The ST-504 can be used during evening downtime to reverse the effects of prolonged sitting.

      Recommended Protocol: L1 pressure, Sequence mode, no heating, 20 minutes before bed.

      Profile 3: The Frequent Traveler

      Long flights (6+ hours) create a perfect storm for leg swelling and, in extreme cases, deep vein thrombosis (DVT). The cabin pressure and confined space reduce circulation. Using the ST-504 after arrival or before departure can significantly reduce travel-related swelling.

      Recommended Protocol: L1 pressure, Whole mode, H1 heating, 20 minutes. Pack the compact sleeve in carry-on luggage.

      See our dedicated Travel Swelling Relief Guide for packing tips and flight-specific recommendations.

      Profile 4: The Elderly Individual

      Age-related venous valve weakening causes chronic venous insufficiency in up to 40% of adults over 60. The gentle graduated compression of the ST-504 supports weakened veins without requiring physical effort from the user. Regular use can improve quality of life by reducing daily leg fatigue and swelling.

      Important: Elderly users with diabetes, peripheral neuropathy, or circulatory disorders should consult their physician before use. See our Pacemaker & Diabetes Safety Guide.

      Profile 5: Post-Surgery Recovery Patient

      After lower limb surgery (knee replacement, ankle fracture, varicose vein procedures), doctors often prescribe compression therapy to prevent blood clots and reduce post-operative swelling. The ST-504 can serve as a home-based continuation of clinical compression therapy, subject to physician approval.

      How to Get the Most Out of Your ST-504

      Building a Treatment Routine

      Consistency is key to seeing results from air compression therapy. Here’s a sample weekly routine:

      Monday/Wednesday/Friday: Post-work or post-workout recovery — L2, Circulation mode, 20 min Tuesday/Thursday: Evening relaxation — L1, Sequence mode, H1 heat, 20 min Saturday: Extended session after long activity — L2, Whole mode, H2 heat, 20 min Sunday: Rest day (or optional light session)

      Combining with Other Recovery Methods

      Air compression therapy works synergistically with other recovery modalities:

    • Before compression: Light stretching or foam rolling enhances blood flow, making compression more effective
    • After compression: Elevation of legs for 5-10 minutes extends the circulation benefits
    • Hydration: Drink water before and after treatment — hydrated blood flows more easily through compressed vessels
    • Compression stockings: On days when you can’t use the ST-504, wear graduated compression stockings for maintenance

      • Troubleshooting Common Issues

      Problem: Sleeve feels too loose

    • Ensure the zipper is fully closed from toe to top
    • Check that the sleeve is positioned correctly (toe marker aligned with foot)
    • Try a higher pressure level

      • Problem: Device makes unusual noise

    • Normal operating noise is under 80dBA — similar to a vacuum cleaner at distance
    • If noise is grinding or rattling, check that the air tube is not kinked
    • Contact support if noise persists after checking connections

      • Problem: Treatment doesn’t feel effective

    • Start with L2 pressure and Circulation mode for maximum effect
    • Ensure you’re using the device consistently (at least 3x per week)
    • Results accumulate over time — most users report noticeable improvement within 2-4 weeks of regular use

      • For more troubleshooting help, visit our ST-504 Error Codes Guide.

      Frequently Asked Questions

      Q: Is the ST-504 FDA approved?

      The ST-504 has an FDA file number (FYC-RD-FDA-004-005) and is manufactured in compliance with IEC 60601-1 and IEC 60601-1-2 standards. It is classified as an OTC (Over-The-Counter) medical device for home use. For details on what FDA clearance means for this device, see our FDA Cleared Medical Devices Guide.

      Q: How long does the battery last?

      The 2000mAh lithium-ion battery provides approximately 100 minutes of full-power runtime. A single treatment session lasts 20 minutes, giving you roughly 5 treatments per charge. See our Battery Life & Charging Guide for optimization tips.

      Q: Can I use the ST-504 while charging?

      No. The device cannot operate while connected to the charging cable. Always ensure the battery is sufficiently charged before use.

      Q: What is the noise level?

      The ST-504 operates at less than 80dBA at 30cm distance, making it suitable for quiet environments like bedrooms and living rooms. For technical specifications on noise measurement methodology, see our Noise Level & Technical Specs.

      Q: Is the ST-504 safe for people with pacemakers?

      No. The ST-504 should NOT be used by anyone with implanted electronic devices such as pacemakers. See our Pacemaker & Diabetes Safety Guide for comprehensive safety information.

      Q: How often should I use the ST-504?

      For best results, use the ST-504 daily or every other day for 20-minute sessions. Consistent use produces cumulative benefits — improved circulation, reduced swelling, and faster recovery.

      Q: What pressure level should I start with?

      Beginners should start with L1 (70.5mmHg) and gradually increase to L2 or L3 as tolerated. If you’re using the device for circulation improvement rather than recovery, L2 is the recommended starting point.

      Q: Can the ST-504 cure medical conditions?

      No. The ST-504 is designed for temporary relief of minor muscle aches and temporary increase in circulation. It is not a cure for any medical condition. Always consult your physician for diagnosis and treatment of medical conditions.

      Q: What size legs does the ST-504 fit?

      The 340×840mm sleeve is designed to fit most adult leg sizes from ankle circumference of 25cm to thigh circumference of 60cm. If you’re between sizes or have unusually large calves, the adjustable zipper allows some flexibility. For specific measurement guidelines, refer to the ST-504 Specifications Reference.

      Q: How long before I see results?

      Most users report reduced swelling within the first week of regular use. Improved circulation and recovery benefits typically become noticeable after 2-4 weeks of consistent daily or every-other-day use. Long-term users (3+ months) often report sustained improvements in leg comfort and reduced end-of-day fatigue.

      Q: Can I share the ST-504 sleeve with multiple users?

      Yes, the sleeve can be shared between household members if each user cleans it after use with a soft, slightly damp sponge. For hygiene best practices, see our Cleaning & Maintenance Guide.

      Conclusion

      The ST-504 Air Compression Therapy Device represents an accessible, FDA-filed solution for improving lower extremity circulation, supporting athletic recovery, and managing leg swelling at home. Its combination of three pressure levels, three heating modes, three vibration intensities, and three working modes provides enough customization for users ranging from beginners to experienced compression therapy patients.

      Whether you’re an athlete seeking faster recovery, an office worker combating sedentary fatigue, a frequent traveler preventing flight swelling, or an elderly individual supporting age-related circulation changes, the ST-504 offers a non-invasive, drug-free approach to better leg health.

      Remember to always consult your healthcare provider before beginning any new therapy, especially if you have underlying medical conditions. Start with the lowest pressure setting, follow the recommended protocols for your use case, and build a consistent routine for best results.

      For the complete technical specifications, safety information, and setup instructions, explore our related articles linked throughout this guide.

    • How Air Compression Therapy Works
    • ST-504 vs Compression Boots
    • Massage Gun vs Air Compression
    • Complete Contraindications Guide
    • How to Use ST-504 — Step-by-Step
    • 3 Working Modes Explained
      • Last updated: 2026-07-23