Respiratory responses to static muscular work

Abstract

The respiratory responses to sustained hand-grip contraction at four tension levels, graded in per cent of maximal voluntary contraction (MVC), were investigated. An increased ventilation was always observed prior to the work, and explained as an element in the alarm-defense reaction. The typical response pattern during and after work was a steady increase during contractions above the 20% MVC level. The ventilatory peak was observed at the end of the work, then a gradual return to resting level took place during the recovery period. A hyperventilation took place at tensions above the 20% MVC level. The chemical environment of the contracted muscles was altered, as is evident from the finding of lowered venous pH and P V O 2 , and elevated P V O 2 and lactate concentration. The level of blood gases in arterial blood remained unchanged, and a nervous reflex mechanism in addition to cortical influence is proposed as an explanation of the hyperventilation.