Effect of respiratory muscle training on load sensations in people with chronic tetraplegia: a secondary analysis of a randomised controlled trial

Spinal Cord, 2023 · DOI: https://doi.org/10.1038/s41393-023-00920-3 · Published: August 16, 2023

Spinal Cord Injury Pulmonology Biomechanics

Simple Explanation

This study investigates whether respiratory muscle training affects the respiratory sensations for load detection and magnitude perception in people with chronic tetraplegia. Participants with tetraplegia underwent a 6-week training program, and the study measured their ability to detect inspiratory loads and perceive the magnitude of suprathreshold loads. The study found that while inspiratory muscle strength increased with training, the ability to detect inspiratory loads did not change. However, the perception of the effort required for a given change in inspiratory pressure was reduced.

Study Duration

6 weeks

Participants

32 adults with chronic tetraplegia

Evidence Level

Level 1, Randomised controlled trial

Key Findings

1
Respiratory muscle training (RMT) increased maximal inspiratory pressure (PImax) by 32% in the active group.
2
RMT did not affect load detection thresholds in either the active or sham group.
3
Increased inspiratory muscle strength reduced the slope magnitude between Borg rating and peak inspiratory pressure, indicating a reduced sensitivity to load sensations for a given pressure change.

Research Summary

This study investigated the effect of respiratory muscle training (RMT) on load sensations in people with chronic tetraplegia. The results showed that RMT increased inspiratory muscle strength but did not affect load detection thresholds. While RMT did not directly lower Borg effort ratings, it reduced the sensitivity of load sensations for a given change in pressure. This suggests that RMT can potentially lessen the increase in perceived effort during respiratory distress. The findings suggest that training protocols based on changes in contraction intensity relative to maximum, rather than the physical properties of the load, will be well tolerated by people with chronic tetraplegia.

Practical Implications

Rehabilitation Potential

RMT has the potential to lessen the increase in perceived effort when the resistance to breathing increases, such as during respiratory distress from pneumonia or exercise.

Training Load Selection

Selection of a suitable training load is important to increase muscle strength while minimizing breathing discomfort to optimize recovery.

Training Protocol Design

Training protocols should be based on changes in contraction intensity relative to maximum rather than the physical properties of the load.

Study Limitations

1
Not all participants completed all tasks, resulting in an unevenly distributed study population.
2
The present study was not adequately powered to compare differences between the sham and active groups for non-significant findings.
3
A learning effect may have influenced the Borg ratings, as participants had no prior experience breathing with an added resistive load.

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