Influence of isocapnic hyperpnoea on maximal arm cranking performance.

Isocapnic hyperpnoea has been shown to reliably produce fatigue of the diaphragm. The aim of the present study was to investigate whether incremental isocapnic hyperpnoea (IH(incr)) impairs the arm exercise performance and alters the breathing pattern during subsequent maximal incremental arm cranking. Nine healthy volunteers performed an arm cranking test with prior IH(incr) (AC(IH)) and without prior IH(incr) (AC(control)). Minute ventilation ( V(E)), tidal volume ( V(T)), breathing frequency ( f(b)), O(2) uptake ( VO(2)), CO(2) elimination ( VCO(2)), respiratory exchange ratio (RER) and end-tidal partial pressure of CO(2) ( P(ET)CO(2)) were measured at three different time intervals ( t(1): the average of the 3.30th min to the 6.30th min, t(2): 1 min before the end, t(3): peak value) and expressed as mean (SD). V(T) at t(1) and at t(3) was significantly ( P<0.05) lower during AC(IH) [AC(control): t(1): 1.3 (0.5) l, t(p): 1.9 (0.3) l; AC(IH): t(1): 1.1 (0.3) l, t(p): 1.6 (0.3) l]. f(b) at t(1) and t(2) was significantly ( P<0.05) higher during AC(IH) [AC(control): t(1): 23 (4) breaths min(-1), t(2): 42 (14) breaths min(-1); AC(IH): t(1): 27 (5) breaths min(-1), t(2): 48 (14) breaths min(-1)]. The maximal voluntary ventilation (MVV), measured before and immediately after the IH(incr), demonstrated a small but significant decrease from 157 (15) l min(-1) to 150 (14) l min(-1) ( P<0.05) after the IH(incr). In conclusion, rapid shallow breathing occurred during maximal arm cranking exercise after IH(incr). The alteration was irrespective of the workload and had already occurred at the start of exercise.