Respiratory muscle performance with stretch-shortening cycle manoeuvres: maximal inspiratory pressure-flow curves.
OBJECTIVE
To test the hypothesis that the maximal inspiratory muscle (IM) performance, as assessed by the maximal IM pressure-flow relationship, is enhanced with the stretch-shortening cycle (SSC).


METHODS
Maximal inspiratory flow-pressure curves were measured in 12 healthy volunteers (35 +/- 6 years) during maximal single efforts through a range of graded resistors (4-, 6-, and 8-mm diameter orifices), against an occluded airway, and with a minimal load (wide-open resistor). Maximal inspiratory efforts were initiated at a volume near residual lung volume (RV). The subjects exhaled to RV using slow (S) or fast (F) manoeuvres. With the S manoeuvre, they exhaled slowly to RV and held the breath at RV for about 4 s prior to maximal inspiration. With the F manoeuvre, they exhaled rapidly to RV and immediately inhaled maximally without a post-expiratory hold; a strategy designed to enhance inspiratory pressure via the SSC.


RESULTS
The maximal inspiratory pressure-flow relationship was linear with the S and F manoeuvres (r2 = 0.88 for S and r2 = 0.88 for F manoeuvre, P < 0.0005 in all subjects). With the F manoeuvre, the pressure-flow relationship shifted to the right in a parallel fashion and the calculated maximal power increased by approximately 10% (P < 0.05) over that calculated with the S manoeuvre.


CONCLUSIONS
The maximal inspiratory pressure-flow capacity can be enhanced with SSC manoeuvres in a manner analogous to increases in the force-velocity relationship with SSC reported for skeletal muscles.
Tzelepis
G E
GE
Department of Pathophysiology and Laiko General Hospital, University of Athens Medical School, Athens, Greece. gtzelep@med.uoa.gr
Zakynthinos
S
S
Mandros
C
C
Tzelepis
E
E
Roussos
C
C
D000328:Adult; D004576:Electromyography; D006801:Humans; D007320:Inspiratory Capacity; D009119:Muscle Contraction / Q000502:physiology*; D012129:Respiratory Function Tests; D012132:Respiratory Muscles / Q000502:physiology*; D012143:Respiratory Physiological Phenomena