Sydney Marathon Prep on an AlterG Treadmill
Searches for "alter g treadmill near me" climb through the Sydney winter, and the story behind them is usually the same. Someone is seven or eight weeks out from the Sydney Marathon, long runs have crept past 28 km, and a calf, shin or Achilles starts complaining in the back half of every easy run. Taking three weeks off puts a hole in the build. Repeating the same 60 km week on Marrickville footpaths often makes the niggle louder. Unweighted running sits between those two choices, and it is one of the reasons runners come to us in the Inner West during a marathon block.
What the machine does
An AlterG anti-gravity treadmill runs inside a sealed air chamber that closes around your hips. You wear neoprene shorts that zip into the chamber, the machine calibrates to your standing weight, then air pressure lifts a set percentage of that weight off you. The AlterG unweights down to 20% of body weight and adjusts in 1% increments, so a 78 kg runner can train at anything from roughly 16 kg of load to full weight.
Less body weight through the leg means smaller peak forces at the tibia, metatarsals, Achilles, patellofemoral joint and plantar fascia with every footstrike, while your legs keep cycling through a running pattern at running cadence. Breathing, heart rate and stride rhythm still get worked. That combination is why it gets used to keep aerobic volume going while a tissue settles.
Where it fits in a marathon build
The usual approach is to convert part of the week rather than the whole week. A runner on 65 km with a grumbling Achilles might keep the outdoor long run and one quality session at full weight, then move two easy runs and part of the long run onto the AlterG at 70 to 80% body weight. Total weekly minutes stay similar. Cumulative load on the sore tissue drops.
Decisions about how much weight to remove, and how fast to add it back, come from your symptoms. A common clinical guide we use with runners:
- Discomfort during the run stays low and does not build session to session
- Symptoms settle within about 24 hours
- The first few steps out of bed the next morning are no worse than the day before
If those hold, body weight typically goes up in 5% steps across sessions. If they do not, the percentage comes back down and we look again at the diagnosis, footwear, cadence and the strength work sitting underneath the running.
The niggles it tends to suit
Unweighted running is most useful when the problem is load tolerance rather than something that needs a full stop. That includes late-stage calf strains, Achilles and patellar tendon irritation, plantar heel pain, patellofemoral pain, graded return after a diagnosed metatarsal or tibial bone stress injury, and running rehab after ACL reconstruction once your surgeon has cleared impact.
It is not the right tool for undiagnosed pain, for bone stress at higher-risk sites such as the femoral neck, or for a leg that hurts to walk on. In those cases the first step is assessment and, where indicated, imaging. MRI picks up early bone stress that plain X-ray often misses, so a referral may be part of the plan before any treadmill running happens.
What it will not replace
The Sydney Marathon is run at 100% body weight over 42.195 km, with the Harbour Bridge climb early and rolling ground later in the course. Road running has camber, downhill braking forces, heat and fuelling demands that no treadmill reproduces. AlterG work is a bridge, not a substitute.
That shapes the plan backwards from race day. We want a runner completing key long runs outdoors at full body weight in the final weeks, with enough of them to know how the leg responds to three hours on concrete. If the calendar does not allow that, the honest conversation is about race day expectations, pace, or shifting to a shorter event.
What an assessment and session involve
A running assessment starts with your training history in numbers: weekly kilometres, surfaces, shoe rotation, how the long run has progressed, where the pace distribution sits. Then physical testing, which usually includes palpation of the painful area, single-leg calf raise capacity, hop and single-leg squat testing, ankle and hip range, and video of your gait on the treadmill.
From there we set a starting body weight percentage, speed and duration. Sessions generally run 20 to 40 minutes. A physiotherapist stays with you and adjusts the unweighting during the run based on what you report and what the gait looks like on the screen. Most runners also get strength work to do alongside it, either at home or in our strength and conditioning classes, because calf and hip capacity is often part of why the niggle appeared in a 60 km week.
When to stop guessing and get it looked at
Get assessed promptly if you have sharp pain in one small spot on a bone, pain that comes on earlier in each run, pain walking or at night, or swelling that keeps returning. Those patterns change the plan, and the earlier they are identified the more of your build there is left to work with.
If you are in the Inner West and managing something through a Sydney Marathon block, you can book a running assessment to talk through where anti-gravity treadmill running might fit in your week.