Passive Cycle Training Promotes Bone Recovery after Spinal Cord Injury without Altering Resting-State Bone Perfusion

Medicine & Science in Sports & Exercise, 2023 · DOI: 10.1249/MSS.0000000000003101 · Published: May 1, 2023

Spinal Cord Injury Rehabilitation Musculoskeletal Medicine

Simple Explanation

Spinal cord injury leads to bone loss and diminished bone perfusion in paralyzed limbs. This study investigates whether activity-based physical therapy (ABPT) can improve bone health after SCI. The study found that passive-isokinetic bicycle training reversed cancellous and cortical bone loss after severe SCI. This occurred without changes in resting-state bone perfusion or locomotor recovery. The findings suggest that passive cycle training promotes bone recovery through antiresorptive and/or bone anabolic actions. This happens independently of changes in blood flow or regaining movement.

Study Duration

4 weeks

Participants

Male Sprague-Dawley rats

Evidence Level

Not specified

Key Findings

1
SCI without ABPT exhibited uncoupled bone turnover and progressive cancellous and cortical bone loss.
2
Hindlimb bicycle training suppressed surface-level bone resorption indices without suppressing bone formation indices and produced robust cancellous and cortical bone recovery at the distal femur.
3
No bone BF deficits existed 4 wk after SCI, and neither qBWSTT nor bicycle altered resting-state bone perfusion or locomotor recovery.

Research Summary

This study investigated the effects of quadrupedal bodyweight-supported treadmill training (qBWSTT) and passive-isokinetic bicycle training on bone health in rats with severe spinal cord injury (SCI). The results showed that SCI led to bone loss, and while qBWSTT did not prevent these deficits, bicycle training reversed cancellous and cortical bone loss. The study concludes that passive-isokinetic bicycle training promotes bone recovery after severe SCI, independently of locomotor recovery or changes in resting-state bone perfusion.

Practical Implications

Rehabilitation Strategies

Passive cycle training can be a valuable tool in rehabilitation programs for individuals with SCI to promote bone health.

Targeted Interventions

The antiresorptive and bone anabolic actions of passive cycle training suggest potential targets for pharmaceutical interventions to improve bone health after SCI.

Further Research

Further studies are needed to fully elucidate the mechanisms by which passive cycle training promotes bone recovery and to explore the relationship between bone blood flow and bone turnover after SCI.

Study Limitations

1
The design did not permit comparison of circulating and surface-level bone turnover indices at 4 wk after surgery because the technique we used to determine BF required infusion of colored microspheres into the circulation, which interfered with spectrophotometric analyses
2
we could not determine bone mechanical characteristics or assess molecular signaling pathways underlying our findings because histomorphometry and microsphere-based BF assessments require embedding/sectioning or destruction of tissue samples.
3
we used a SHAM control group to account for the surgical stress required to produce the contusion SCI, and it is unclear how bone loss occurring in response to T9 laminectomy may have influenced resting-state bone BF.

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