1. Background
Musculoskeletal disorders (MSDs) encompass a broad range of conditions affecting bones, muscles, joints, tendons, and ligaments. Common clinical conditions include fractures, degenerative joint diseases, and sports-related injuries.These conditions, together with postoperative immobilization and restricted physical activity, may lead to muscle weakness, muscle atrophy, reduced joint range of motion, and impaired gait function, ultimately affecting patients’ mobility and quality of life.
Although conventional rehabilitation can improve physical function, patients experiencing pain, weight-bearing restrictions, or insufficient lower-limb loading capacity may find it difficult to participate in early and repetitive gait training.
The anti-gravity treadmill utilizes lower-body positive pressure technology to provide adjustable body-weight support. This allows individuals to perform walking and running exercises while reducing the load placed on the lower extremities.By enabling controlled weight-bearing during exercise, AGT offers an additional rehabilitation approach for patients recovering from fractures, joint replacement surgery, and other musculoskeletal conditions.
This systematic review evaluated the clinical applications and potential effects of anti-gravity treadmill training in individuals with various musculoskeletal disorders.
2. Methods
A systematic literature search was conducted on May 10, 2024, using PubMed, Scopus, and Web of Science. The review followed PRISMA guidelines.The methodological quality of the included studies was assessed using the PEDro scale and the Joanna Briggs Institute (JBI) checklist.
Study selection and characteristics:
- Articles initially screened: 185
- Studies included in the final review: 11
- Total participants: 386
- AGT intervention group: 246 participants
- Control group: 140 participants
- Randomized controlled trials: 6
The included studies investigated patients undergoing total knee arthroplasty, femoral fractures, hip fractures, ankle fractures, tibial plateau fractures, anterior cruciate ligament reconstruction, meniscectomy, Achilles tendon repair, and lower-limb osteoarthritis.
3. Results
3.1 Improvement in Muscle Function and Muscle Atrophy-Related Outcomes
Fractures and postoperative activity restrictions may contribute to muscle weakness and atrophy. AGT enables repetitive walking exercises under reduced weight-bearing conditions.
A randomized controlled trial involving patients with femoral fractures reported that adding 20 minutes of AGT training per session for four weeks to conventional rehabilitation resulted in greater improvements in isokinetic strength of the hip extensor muscles and gluteal muscle activity compared with conventional rehabilitation alone.
In addition, studies involving patients with ankle and tibial plateau fractures evaluated muscle atrophy as an outcome. These findings suggest that AGT may contribute to postoperative muscle function recovery.
3.2 Improvements in Fracture Healing and Bone-Related Outcomes
A randomized controlled trial published in 2024 involving patients with ankle fractures reported improvements after eight weeks of intervention in bone callus quality scores, bone density, ankle-hindfoot function scores, pain scores, and ankle range of motion.
These findings suggest that appropriately prescribed exercise may contribute to skeletal recovery and functional rehabilitation following fractures.
However, these results relate to patients recovering from fractures and should not be interpreted as direct evidence that AGT prevents osteoporosis or age-related bone loss in the general population.
3.3 Improved Joint Range of Motion and Pain Reduction
Positive effects on joint range of motion and pain were reported in studies involving patients recovering from ankle fractures, tibial plateau fractures, and anterior cruciate ligament reconstruction.
In individuals with lower-limb osteoarthritis, body-weight-supported walking enabled higher walking speeds during aerobic exercise and was associated with improvements in exercise-related pain.
Among patients following total knee arthroplasty, improvements in the Timed Up and Go (TUG) test were also reported, indicating enhanced functional mobility.
3.4 Improvements in Gait Function and Balance
Research involving patients with hip fractures found that combining AGT training with conventional rehabilitation resulted in additional improvements in the Koval walking ability score, Functional Ambulation Category (FAC), Berg Balance Scale (BBS), and quality-of-life scores.
Improvements in dynamic gait index and joint range of motion were also observed in some studies involving lower-limb fractures, suggesting that body-weight-supported gait training may facilitate the recovery of walking function.
3.5 Reduced Cardiovascular Responses During Exercise
In patients following total knee arthroplasty, body-weight support enabled walking at higher speeds and tolerating greater treadmill inclines.
Related studies also reported reductions in cardiovascular responses, including heart rate, systolic blood pressure, and oxygen consumption, with increasing levels of body-weight support.
These findings suggest that AGT provides a flexible approach to exercise-load management by allowing body-weight support to be adjusted according to individual physical capacity.
4. Training Parameters and Clinical Applications
The training protocols varied considerably across the included studies:
- Body-weight support: 20%–85%.
- Training duration: Commonly 10–20 minutes per session, with some studies reporting 8–32 minutes.
- Initial treadmill speed: Approximately 0.8–2.3 mph.
- Training approach: Primarily walking exercises, with some protocols progressively increasing treadmill speed and adjusting incline according to patient tolerance.
Self-selected walking speed was commonly used to ensure patient comfort and tolerance.
The appropriate body-weight support level and training protocol should be determined according to the patient’s diagnosis, age, physical condition, postoperative stage, and clinical weight-bearing restrictions.
5. Conclusions and Clinical Implications
This systematic review indicates that anti-gravity treadmill training is feasible, safe, and well tolerated in individuals with various musculoskeletal disorders.
Compared with conventional rehabilitation alone, the addition of AGT training demonstrated further improvements in joint range of motion, gait function, muscle strength, pain-related outcomes, and fracture recovery-related measures in some studies.
Its potential clinical benefits include:
- Reduced lower-limb loading: Providing an adjustable exercise environment for patients with weight-bearing restrictions or exercise-related pain.
- Support for early mobilization: Facilitating earlier gait training when consistent with clinical weight-bearing requirements.
- Functional recovery: Supporting improvements in muscle strength, joint mobility, balance, and walking performance through repetitive gait training.
- Individualized exercise-load management: Allowing body-weight support and exercise intensity to be adjusted according to individual rehabilitation needs.
Nevertheless, considerable heterogeneity existed among the included studies in terms of diagnoses, body-weight support levels, training duration, and outcome measures. Therefore, a quantitative meta-analysis could not be performed.Further high-quality randomized controlled trials using standardized training protocols and outcome measures are required to establish the clinical effectiveness of AGT more definitively.
Overall, anti-gravity treadmill training represents a promising rehabilitation approach that provides adjustable body-weight support and facilitates gait training in patients with musculoskeletal disorders, particularly those recovering from fractures, joint replacement surgery, and lower-limb functional impairments.
Reference：Trovato B, Sortino M, Roggio F, et al. Exploring the effects of anti-gravity treadmill training in musculoskeletal disorders: A systematic review. Heliyon. 2024;10. https://doi.org/10.1016/j.heliyon.2024.e40605.