Anti-Gravity Treadmill: What It Is, Who Uses One and What It Costs

1. What Is an Anti-Gravity Treadmill? The Short Answer

An anti-gravity treadmill is a treadmill enclosed in a sealed air chamber from the waist down; raising the air pressure in the chamber lifts the user, so they walk or run carrying only a set percentage of their body weight. The best-known make is the AlterG Anti-Gravity Treadmill, whose current models can unweight a user by up to 80 percent of body weight in one-percent steps, according to the manufacturer.

The technique is called differential air pressure. You wear a pair of special shorts with a skirt that zips into an opening in the chamber, the chamber inflates, and the pressure difference pushes upward on your body. Because the lift is spread evenly, your gait stays close to normal, which is the point: you can practise walking or running with near-normal mechanics while your joints, a healing bone or a repaired ligament carry less load.

These machines are mainly found in rehabilitation hospitals, outpatient physical therapy clinics, university sports programmes and professional teams. Clinics that sell sessions directly to the public commonly charge somewhere in the region of $15 to $75 per session on the US price lists we checked, depending on the package and the location. Buying a clinical machine costs tens of thousands of dollars. A small number of home-focused air-pressure treadmills now exist, and for most people the practical home alternatives are low-impact walking set-ups rather than unweighting machines.

2. How Does Differential Air Pressure Work?

Differential air pressure works by raising the air pressure around your lower body slightly above the pressure around your upper body, so that the difference produces an upward force that offsets part of your weight.

In practice, the treadmill sits inside a flexible chamber, a little like a large inflatable bag sealed around the frame. The user steps into an opening in the top, wearing neoprene shorts with a fabric skirt around the waist. The skirt zips onto the opening and forms an airtight seal at the waist. A blower then raises the pressure in the chamber. Because the user's lower body is inside the higher-pressure zone and the upper body is outside it, the net effect is an upward push at the waist, and the treadmill's scale reads a lower effective body weight.

The machine first calibrates to your weight, then the operator sets a percentage, for example 60 percent of body weight. The manufacturer states that the current AlterG systems adjust the pressure continuously and in one-percent increments, and allow up to 80 percent unweighting, which leaves the user carrying 20 percent of body weight at the lowest setting. From there the session is ordinary treadmill walking or running at a set speed and incline, with the unweighting changed as the session or the rehabilitation programme progresses.

Why air rather than a harness? Harness-based body-weight-support systems also exist and are widely used in rehabilitation, particularly for people who need help with balance. A harness lifts from the trunk and groin, which can be uncomfortable at higher unweighting and can alter the way the hips move. Air pressure lifts more evenly around the pelvis and leaves the arms and legs free, which is why runners and athletes tend to use it. The two do different jobs, and a clinic will choose between them for the patient.

The NASA connection. The idea came from research at NASA's Ames Research Center, where Robert Whalen worked on using air pressure to load astronauts' bodies during exercise. NASA's own account describes how the concept was reversed to reduce load instead, and later developed into the AlterG. It is a genuine spin-off, though in day-to-day use it is a rehabilitation and training tool rather than space technology.

3. What Is the AlterG, and Who Makes It Now?

AlterG is the brand name most people mean when they search for an alter g treadmill, and since August 2023 it has been owned by Lifeward, the company formerly called ReWalk Robotics.

ReWalk completed its purchase of AlterG on 11 August 2023, for a cash price of approximately $19 million according to its annual report, and later renamed the combined company Lifeward. AlterG's own site, checked on 14 October 2026, lists three current models, the NEO, the NEO+ and the PRO, all built around the same differential-air-pressure technology. Lifeward's most recent annual report describes the NEO as the entry-level model introduced in 2024, the NEO+ as adding higher speeds and an integrated camera for gait analysis, and the PRO as the top model aimed at sports medicine and elite sport. Older models such as the M320, F320, Via 400 and Pro 200 remain in many clinics, and you may be booked on any of them.

Lifeward's annual report states that AlterG systems are used in more than 6,000 facilities in more than 40 countries. It describes its markets as inpatient rehabilitation facilities, outpatient clinics and sports programmes, and it does not describe a consumer home model. Users wear proprietary shorts, which some clinics sell to patients and others lend.

Is it the same as a zero gravity treadmill? In searches, "zero gravity treadmill" usually means the same thing. No treadmill removes gravity, and the clinical machines stop well short of zero body weight; the term is marketing shorthand for reduced-body-weight running.

4. Who Uses an Anti-Gravity Treadmill?

Anti-gravity treadmills are used mainly by people in physical rehabilitation after lower-limb injury or surgery, by people with neurological conditions that affect walking, by athletes returning from injury or managing training load, and by people for whom full-weight walking is painful.

• After lower-limb injury or surgery. Clinics use reduced body weight to let patients walk or run earlier and with better mechanics than they could at full weight, following the surgeon's or therapist's loading plan. Typical examples are knee and hip surgery, ankle injuries and stress fractures.
• Neurological conditions. The Shirley Ryan AbilityLab in Chicago, for example, lists stroke, multiple sclerosis, Guillain-Barre syndrome and spinal cord injury among the conditions its AlterG training serves, alongside general strength, mobility and balance goals.
• Runners and athletes. Professional and college teams use anti-gravity treadmills to keep injured athletes running while a bone or tendon heals, and some runners use them to add training volume with less impact.
• Joint pain and higher body weight. Some clinics market sessions to people who want to walk for longer with less joint stress, including older adults and people whose weight makes walking uncomfortable.

Who it is not for, or not yet. Clinics screen users before the first session, and some conditions, recent wounds, or surgical restrictions rule it out or delay it. The Shirley Ryan AbilityLab, for example, states that clients must be prescreened. If you are under the care of a surgeon or therapist, the decision about whether and when to use one, and at what body weight, is theirs to make with you.

5. How Do You Get a Session on One?

Most people use an anti-gravity treadmill either as part of a physical therapy plan, where the therapist includes it in treatment, or by booking cash-pay sessions at a clinic or sports facility that offers them to the public.

Through physical therapy

If you are already in a course of physical therapy, ask whether the clinic has one and whether it suits your plan. When it is used as part of treatment, it is part of the therapy session rather than a separate purchase, and whether insurance covers that session depends on your plan and the clinic's billing, so ask both.

Cash-pay sessions

Many clinics and hospital wellness centres rent time on the machine directly, often in 30-minute blocks, with an initial screening or orientation. The AlterG site has a location finder listing facilities with its machines, which is the simplest place to start; then call the facility and ask whether it offers self-pay sessions, whether a referral is needed, and whether a staff member supervises.

What a session is like

Expect to put on the shorts, step into the chamber and zip in, then stand while the machine calibrates to your weight. The operator sets a body-weight percentage and you walk or run as you would on any treadmill, with the speed, incline and unweighting adjusted during the session. People commonly describe the first minutes as odd, a feeling of being lifted at the hips, before settling into it. Sessions are usually 30 minutes.

6. How Much Does an Anti-Gravity Treadmill Session Cost?

On the US clinic price lists we checked on 14 October 2026, cash-pay anti-gravity treadmill sessions ranged from about $12.50 to $75 per session, depending on the facility and whether you buy a single session, a package or a membership.

These are two published examples at opposite ends of the range, not a national average, and they cover different settings: a clinic renting time on the machine, and a specialist rehabilitation centre programme. Prices change and vary widely by city, so treat the band as a guide and call your local provider. In the UK, private providers commonly publish prices in the region of £20 to £45 per session, again varying with packages.

Extra costs to ask about: an initial assessment or orientation, which some providers require and charge for separately; the special shorts, which some clinics sell and others lend; and whether a therapist supervises, which may cost more than unsupervised time on the machine.

Insurance. When an anti-gravity treadmill is used within a course of physical therapy, the session is generally billed as therapy, and whether it is covered depends on your plan. Cash-pay wellness sessions are usually not covered. Ask the clinic how it bills before the first session.

7. How Much Does It Cost to Buy an Anti-Gravity Treadmill?

Clinical anti-gravity treadmills cost tens of thousands of dollars, and the manufacturer does not publish list prices; facilities buy them through sales representatives and distributors, often with financing and service contracts.

The figures that do exist come from press coverage over the years, so treat them as historical rather than current. Engadget reported an earlier, smaller AlterG model at $24,500 and up, around 2010, with a monthly financing option. Local news coverage of clinics buying one has quoted figures in the region of $35,000 to $75,000 depending on model. Lifeward's annual report, checked on 14 October 2026, does not disclose prices, and notes that it also earns revenue from the shorts users wear and from extended service contracts after the standard warranty.

Beyond the purchase, a clinical machine needs floor space, a suitable electrical supply, installation, staff training and ongoing service. That is why most private individuals use one at a clinic rather than buying.

Home-focused air-pressure treadmills

A small number of companies have tried to bring the technique home. Boost Treadmills, a California company founded in 2017, was set up specifically to make an affordable air-pressure treadmill, and NASA's spin-off coverage describes it as cutting the price of an antigravity treadmill by almost two-thirds. Boost's own site, checked on 14 October 2026, describes its Boost 3 as designed for home use and available to rent or lease as well as buy, but does not publish a price. One press report put the Boost 3 at $24,999 to buy, with home rental from $499 a month; we could not confirm those figures on Boost's own site, so ask the company for a current quote. Even at that level, it is a specialist purchase for people with a long-term need, usually made with a clinician's input.

8. What Can an Anti-Gravity Treadmill Do, and What Can It Not?

An anti-gravity treadmill lets someone walk or run with less load on the legs while keeping a near-normal gait, which is genuinely useful in rehabilitation; it does not replace the rest of a rehabilitation programme or make full-weight training unnecessary.

What it does well. It allows graded loading: a therapist can start a patient at a low percentage of body weight and raise it session by session. It lets athletes maintain running fitness and the habit of running while an injury heals. It allows people who find walking painful to walk for longer, which can build confidence and conditioning. Because the speed and unweighting are precise, progress is easy to measure.

What it does not do. It does not strengthen muscles for full body weight on its own; strength work and eventually full-weight walking and running are still part of a plan. It does not train balance in the same way as walking unsupported, because the chamber gives some stability at the waist. And the reduction in load is not the only thing that matters in healing: timing, the type of injury and the surgeon's restrictions all count.

We are not in a position to summarise the clinical research on outcomes, and we do not quote it. If you want to know whether it would help your particular recovery, ask your surgeon or physical therapist, who can weigh it against the alternatives for your condition.

9. What Are the Home Alternatives?

For most people the realistic home alternatives are low-impact rather than reduced body weight: walking at a gentle pace on a well-cushioned treadmill, moderate incline walking instead of running, pool walking, and non-impact machines such as bikes and ellipticals. None of them unweights you, but each reduces impact in its own way.

• A cushioned treadmill at walking pace. A deck with effective cushioning softens footstrike compared with pavement. Our guide totreadmill cushioningexplains what it does and does not change, andour picks for bad kneescovers machines suited to joint-conscious walkers.
• Incline walking instead of running. Walking uphill raises the effort without the impact of running. Our guide towhat incline to walk onexplains how to start. Incline does increase load on some structures, such as the Achilles and calves, so check with your therapist if those are the injured part.
• Pool walking and deep-water running. Water is the original unweighting: buoyancy reduces load, and deep-water running uses a flotation belt to remove impact altogether. Many community pools allow it, and some physical therapy clinics have pools with built-in underwater treadmills.
• Bikes and ellipticals. Both remove impact. Our comparison of atreadmill vs ellipticalsets out the trade-offs.
• Handrail support, sparingly. Holding the rails takes some weight off the legs, and in early rehabilitation a therapist may suggest it. It also changes posture and gait, so it is a stopgap rather than a substitute for unweighting.

If you need true reduced-body-weight training at home for a long-term condition, talk to your therapist about whether a home air-pressure machine, a rental, or regular clinic sessions make most sense. For most short recoveries, clinic sessions during the critical weeks and a low-impact set-up at home are the usual combination.

10. What Should You Ask Before Booking?

Before booking anti-gravity treadmill sessions, confirm that they fit your treatment plan, what the full cost will be, and who will supervise.

1. Has my surgeon or therapist approved it, and at what body weight should I start?
2. Is a screening or assessment required, and is it charged separately?
3. Will a therapist supervise, or is it self-guided after the orientation?
4. What does a single session cost, and what do packages or memberships cost?
5. Do I need to buy the shorts, or does the clinic provide them?
6. Is it billed as therapy, and will my insurance cover any of it?
7. Which model does the clinic have, and does it record gait data I can take to my therapist?

A provider that will not screen you, or that encourages you to go beyond your surgeon's restrictions, is not the right one.

11. Frequently Asked Questions