Does an anti-gravity treadmill keep my fitness while unloading my legs?

Farina and colleagues (High Point University, Slippery Rock University) reviewed what running on lower-body positive pressure treadmills (LBPPTs), which reduce body weight to cut musculoskeletal loading, does to biomechanics and physiology, as the devices spread into athletic performance and clinical rehabilitation.

A search of PubMed, CINAHL, MEDLINE and SPORTDiscus found 15 eligible peer-reviewed studies; two reviewers rated their quality with a modified Downs and Black checklist for non-randomised studies.

Peak and active vertical ground-reaction forces were consistently reduced with unweighting, but loading within the foot shifted toward a forefoot strike; LBPPTs also provide some horizontal assistance. Neuromuscular activation was generally reduced, though stabiliser muscles may respond differently from propulsive ones.

Submaximal heart rate and oxygen uptake fell with unweighting, while maximal physiological responses were generally unchanged. The authors conclude that LBPPTs let people reach a given metabolic stimulus with less musculoskeletal loading, but that they change neuromuscular activation and biomechanics in complex ways that clinicians must account for.

Our reading: the base had no entry on anti-gravity treadmills. The practical consequence is that at a given speed unweighting lowers the heart-rate and oxygen cost, so the runner must go faster to keep the dose — and speed loads the forefoot.

A later study outside the base (Thomson 2017) found that raising speed raised peak plantar force more than raising body-weight support lowered it.