AlterG Anti-Gravity Treadmill Accuracy of Unloading Is Affected by Support Frame Height

Abstract

de Heer, HD, Kaufman, A, Repka, CP, Rojas, K, Charley, B, and Bounds, R. AlterG Anti-Gravity Treadmill accuracy of unloading is affected by support frame height. J Strength Cond Res 35(10): 2910–2914, 2021—The AlterG Anti-Gravity Treadmill uses air pressure to provide partial body-weight support (BWS), lowering impact forces and metabolic demand of walking and running. Users wear specialized shorts that zip onto a bag supported by a metal bar frame covering the treadmill. The frame is placed at hip height in positions numbered 1–9, adjusted up or down based on preference. Machine accuracy in providing BWS is important to achieve desired training effects, but it is unknown whether frame placement impacts accuracy. Twenty subjects (10 men/women) were weighed in 10% increments from 0 to 60% BWS with the frame at hip height (iliac crest), the “neutral” position, and reweighed with the frame placed up to 3 numbers above or below hip height. Although the machine displayed the same proportion BWS, placing the frame higher than the neutral position resulted in significantly more support, whereas placing the frame lower led to less support. At 10% BWS, placing the frame 3 positions higher resulted in 3% more support compared with the neutral position (13.1% BWS, p < 0.001) and 3 positions lower in 4.7% less support (5.3% BWS, p < 0.001). Deviances were greater with more BWS. At 60% BWS, 3 positions higher than neutral resulted in 71.2% BWS (11.2% more than expected, p < 0.001) and 3 below 48.1% BWS (12.9% below expected, p < 0.001), total 24.1% difference. These findings suggest that the position of the support frame significantly impacts the AlterG accuracy in providing BWS, with placement higher than hip height resulting in more support than displayed by the machine and lower placement resulting in less support.

Role of Antigravity Training in Rehabilitation and Return to Sport After Running Injuries

“…Vertical adjustment of the frame height allows participants of different heights to use the machine. 4 Moreover, a more sensitive adjustment of the body weight support can be provided. Antigravity treadmills allow for support up to 80% of body weight.…”

“…The standard operating instructions of the treadmill states the frame should position the zipper at the iliac crest line, with the caveat that the frame can be adjusted up or down on the basis of the individual preference for more or less trunk stabilization. de Heer et al 4 examined the accuracy of the AlterG unweighting across a range of body weight support levels (from 0% to 60%). Following the standard instructions, the authors found that the greatest accuracy occurred in the 10%-40% BWS range.…”

“…Even with 0% BWS, the treadmill may, in reality, provide 5%-8% BWS. 4,29 An experimental study was conducted specifically to test the accuracy of the BWS proportions displayed by the AlterG treadmill. 3 It was found that greatest variability from the predicted support level occurred at 100% (93% actual BWS), and above 60% (actual BWS level was 3%-8% more than displayed).…”