Influences of ventilation on maximal isometric force of the finger flexors.

Force production may be influenced by the phase of ventilation during which force is exerted. To examine the potential influences of ventilation on variability in maximal force measurements, we recorded peak isometric forces of the finger flexors during normal breathing, forced inspiration, forced expiration, and the Valsalva maneuver in 14 healthy adult subjects. The peak force increased significantly from forced inspiration to forced expiration (about 10%). Both forced expiration and inspiration resulted in increases in the flexor/extensor cocontraction ratio, whereas the Valsalva maneuver had no significant effects on maximal force or cocontraction ratio. Thus, this study clearly demonstrates the effects of ventilation on maximal finger force-generating capability. Ventilation needs to be controlled for accurate assessments of maximal force.