Balancing acts: respiratory sensations, motor control and human posture

Area of Science:

• Physiology
• Neuroscience
• Biomechanics

Background:

• Viscerosomatic reflexes involving pulmonary afferents can limit exercise in animals.
• Recent studies in humans challenge the role of these reflexes in limiting exercise.
• The interaction between respiratory and limb/trunk movements is complex.

Purpose of the Study:

• To review novel aspects of the integration between respiration and body movement.
• To explore the role of pulmonary afferents and respiratory sensations in exercise limitation.
• To examine the interaction between limb/trunk control and respiratory muscles, particularly the diaphragm.

Main Methods:

• Review of recent studies on pulmonary afferent stimulation in humans.
• Analysis of diaphragm activity during limb movements.
• Examination of postural challenges and their effect on ventilation.

Main Results:

• Pulmonary afferent stimulation in humans does not evoke reflex motoneuronal inhibition.
• Noxious respiratory sensations from vagal afferents appear critical for exercise cessation decisions.
• The diaphragm exhibits both feed-forward drive and phasic/tonic contractions during limb movements.
• Diaphragm coordination contributes to trunk control, and postural challenges can impact ventilation.

Conclusions:

• Exercise limitation in humans may be driven by sensory feedback rather than reflex inhibition.
• The diaphragm plays a dual role in both respiration and postural/movement control.
• Understanding the interplay between respiration and movement is crucial for exercise physiology and rehabilitation.