Efficacy of Lower Body Positive Pressure Treadmill in PT Rehab


Following this blog, the PT’s will be able to:


  • Prepare a running program safely on the Alter-G for a patient with a variety of injuries
  • Identify specific differences in running kinematics with varying BW% on the Alter-G
  • Research protocols for specific injuries and utilize clinical decision making for progression/regression to prevent re-injury


  • Correctly state 3 physiological effects of using a LBPPT
  • Correctly identify 4 effects on kinetics while running on an Alter-G
  • Value educating patients about the positive effects of using an Alter-G early in their rehabilitation program


How it Works

Originally developed by a researcher at NASA to maintain fitness between prolonged space flight times.

Alter g diagram showing many features listed in this blog post


  • Running Speed
  • Fitness level of subjects
  • Treadmill and LBPPT running experience
  • Lack of high-level confidence
  • Carryover effect

Physiological Effect:

  • Lower metabolic cost
  • Lower neuromuscular activation
  • Lower HR
  • Lower respiratory frequency
  • Lower minute ventilation
  • Lower RPE
  • Lower Vo2
  • Lower Submaximal HR

Reductions in weight and metabolic demand attributed to inflation of the chamber. (Standing weight on LBPPT was an average 7% lower than predicted BW (Body weight).

Additional vertical and horizontal support in mediolateral direction reduces the need to propel in the anterior-posterior direction.

Running Kinetics:

Direct relationships
– Increased BWS (Increased stride-length)
– Increased BWS (Increased flight duration)
– Increased Gait Speed (same BW%) =
– Increased plantar forces

Increased relationships
– Increased BWS= Decreased Cadence (Longer swing phase)
– Increased BWS= Decreased contact time
– Increased BWS= Decreased peak pressure

chart showing running kinetics  relationship between body weight and cadence

Shift to forefoot loading distribution. 80% BW may provide balance between Fmax and impulse while minimally disrupting in-shoe regional loading. Alter-G significantly reduces in-shoe maximum forces and impulse during running across multiple speeds. BW and relative load for each of 9 foot regions examine were different except 4 were the same between 80%-100% BW.

Achilles Tendon Surgery:

Alter-G protocol example-

  • Week 9-11 post op:
    Gait in AG 30-50% 1.5-2.5 MPH for 10-15 minutes.
  • Week 12-14 post op:
    Gait in AG 50-75% 2.5-3.5 MPH, 20-30 minutes.
  • Week 15-16 post op:
    Walk/jog 75-90% 3.5-4.0/5.0-6.0, 10 minutes.

1-5% progression if normal gait and pain free.

diagram of medical procedure - achilles tendon surgery

Stress Reactions:

Case study of Division 1 female runner with an iliac stress reaction (Tenforde et al., 2012)

  • Week 1-2: Aqua-jogging, stationary bicycle, isometric cope and hip exercises.
  • Week 3: 3 runs at 50-70% BW but had pain.
  • Week 4: No running due to previous pain.
  • Week 5: 5% BW 5-minute jog with 1 min recovery x3.
  • Week 6: 70% BW for 5 minutes.
  • Week 7: 85% for 35 minutes.
  • Week 8: 95% for 45 minutes.
  • Week 9:
  • Week 10: Qualified for NCAA track championships in 10,000m race without pain.


Knee Osteoarthritis:

2 weeks of Alter-G intervention improvements:

10 MWT, Tug Test, VAS score, Community Ambulation, Increased stride length, Increased velocity, Increased cadence, Increased Knee flexion/ext ROM.

Diagram of AlterG setting up and AlterG intervention protocol

Written by

Melissa A. Riback


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