PMC

A, calculated mechanical advantages (•) and computed changes in airway pressure (ΔP_ao, bars) of the parasternal intercostal muscles in interspaces 2–5. B, mechanical advantages (•) and ΔP_ao (bars) of the triangularis sterni muscle in interspaces 2–6. The mechanical advantages were calculated by dividing the fractional changes in muscle length (ΔL/L) by the inspiratory capacity, and are expressed as percentage changes per litre; a negative mechanical advantage indicates an inspiratory effect, while a positive mechanical advantage indicates an expiratory effect.

x-axis = % tooth row; y-axis = MA (mechanical advantage).

Individual plantarflexor effective mechanical advantage curves throughout 20–90% of stance for children who idiopathically toe-walk

A, the mechanical advantage is plotted against the mean number of motor unit spikes during inspiration (i.e. neural drive) for different regions of the parasternal intercostals (•) and external intercostals (○). There is a strong linear relation between the mechanical advantage and neural drive for each muscle (r²= 0.99). The line for parasternal intercostals has been extrapolated to predict the mechanical advantage of the muscle fibres in the first space (marked as a cross). Note that the medial and lateral (marked as a square) portions of the 2nd parasternal intercostal muscle have a similar mechanical advantage. Note also that there is an appropriately low neural drive to the ventral portion of the 3rd external intercostals, which has a low mechanical advantage compared to the dorsal portion. This figure is modified from . B, the gradients of mechanical advantage and inspiratory drive are shown schematically for the parasternal intercostals and the external intercostals. The letters L, R, P and A refer to left, right, posterior and anterior, respectively.