No abstract

Haemodynamic responses to maximal exercise were similar for both exercise modes in individuals with cervical spinal cord injury. The lower cardiac output in individuals with cervical spinal cord injury compared with able-bodied individuals at equivalent workloads reflects the inability of the circulatory system to increase stroke volume.

During increased ventilation, inspiratory rib cage muscles have been suggested to take over part of diaphragmatic work after the diaphragm fatigues. We investigated the extent to which this proposed change in muscle recruitment is associated with changes in the relative contribution of chest wall compartments to tidal volume (V(T)). Thirteen healthy subjects performed 1 h of fatiguing normocapnic hyperpnoea. Chest wall volumes were assessed by optoelectronic plethysmography. While breathing frequency increased (43±3 to 56±5 breaths min(-1), p=0.006) and V(T) decreased during normocapnic hyperpnoea (2.6±0.2 to 1.9±0.1l, p<0.001), the relative contribution of chest wall compartments to V(T) remained unchanged (pulmonary rib cage: 48±9 versus 51±14%; abdominal rib cage: 24±4 versus 23±9%; abdomen: 28±8 versus 26±9%; all p>0.05). In conclusion, fatiguing respiratory work is not associated with a change in compartmental contribution to V(T), even in the presence of a change in breathing pattern. AbstractDuring increased ventilation, inspiratory rib cage muscles have been suggested to take over part of diaphragmatic work after the diaphragm fatigues. We investigated the extent to which this proposed change in muscle recruitment is associated with changes in the relative contribution of chest wall compartments to tidal volume (V T ). Thirteen healthy subjects performed 1 h of fatiguing normocapnic hyperpnoea. Chest wall volumes were assessed by optoelectronic plethysmography. While breathing frequency increased (43 ± 3 to 56 ± 5 breaths·min -1 , p = 0.006) and V T decreased during normocapnic hyperpnoea (2.6 ± 0.2 to 1.9 ± 0.1 l, p < 0.001), the relative contribution of chest wall compartments to V T remained unchanged (pulmonary rib cage: 48 ± 9 versus 51 ± 14%; abdominal rib cage: 24 ± 4 versus 23 ± 9%; abdomen: 28 ± 8 versus 26 ± 9%; all p > 0.05). In conclusion, fatiguing respiratory work is not associated with a change in compartmental contribution to V T , even in the presence of a change in breathing pattern.