Exercise‐induced diaphragmatic fatigue in healthy humans.

Abstract

SUMMARY1. Twelve healthy subjects (33 + 3 years) with a variety of fitness levels (maximal oxygen uptake (VO2 max) = 61+4 ml kg-1 min-', range , exercised at 95 and 85 % V02, max to exhaustion (mean time = 14 + 3 and 31+8 min, expired ventilation (VE) over final minute of exercise = 149+9 and 126 + 10 1 min-').2. Bilateral transcutaneous supramaximal phrenic nerve stimulation (BPNS) was performed before and immediately after exercise at four lung volumes, and 400 ms tetanic stimulations were performed at 10 and 20 Hz. The coefficients of variation of repeated measurements for the twitch transdiaphragm pressures (Pdi) were +7-10 % and for compound muscle action potentials (M wave) ± 10-15 %. 5. The fPdi min-' and the fP. min-' (PO, oesophageal pressure) rose together from rest through the fifth to tenth minute of exercise, after which fPdi min-' plateaued even though fPO min-', VE and inspiratory flow rate all continued to rise substantially until exercise terminated. Thus, the relative contribution of the diaphragm to total respiratory motor output was progressively reduced with exercise duration.6. We conclude that significant diaphragmatic fatigue is caused by the ventilatory requirements imposed by heavy endurance exercise in healthy persons with a variety of fitness levels. The magnitude of the fatigue and the likelihood of its occurrence increases as the relative intensity of the exercise exceeds 85 % of V02 max,

Compartmental chest wall volume changes during volitional hyperpnoea with constant tidal volume in healthy individuals

“…In a recent study of 3 our laboratory, Renggli et al (Renggli et al, 2008) showed an increase in the ratio of oesophageal to transdiaphragmatic pressure generation during prolonged normocapnic hyperpnoea suggesting a partial takeover of diaphragmatic work by inspiratory rib cage muscles, similar to what was observed during exercise (Johnson et al, 1993;Mador et al, 1993).…”

“…Although volitional measures of fatigue may be confounded by the presence of central fatigue, the decrease in end-inspiratory V rc,p with no change in the other two compartments is considered an independent indicator of inspiratory rib cage muscle fatigue. Furthermore, the few studies assessing respiratory muscle fatigue after exercise with both measurement of oesophageal and gastric pressure during nerve stimulation and during voluntary respiratory manoeuvres show a decrease in twitch pressures with smaller decreases (or no significant change) in pressures during voluntary manoeuvres (Johnson et al, 1993;Mador et al, 1993;Taylor et al, 2006;Kabitz et al, 2008;Taylor and Romer 2008).…”

“…This is seen in an over-proportional increase of oesophageal compared to transdiaphragmatic pressure generation (Johnson et al, 1993;Mador et al, 1993). Furthermore, an increased perception of respiratory exertion and the adoption of a rapid and shallow breathing pattern are often observed in the course of exercise (Kearon et al, 1991), both of which have been ascribed, at least in part, to rib cage muscle fatigue (Ward et al, 1988;Verges et al, 2006).…”

Effects of high-intensity interval training on pulmonary function

“…Expiration becomes active which requires larger muscle recruitment, and a larger amount of oxygen demanding an increase in blood flow (Babcock et al, 2002;Johnson et al, 1993;Witt et al, 2007). Evidence suggests that the demand for an increase in blood flow to the respiratory muscles during maximal or heavy exercise "steals" blood flow from the other exercising muscles through sympathetically mediated vasoconstriction (Harms et al, 1998;St.…”

Diaphragmatic function after intense exercise in congestive heart failure patients

“…Furthermore, diaphragmatic fatigue was found in normal volunteers after endurance exercise in which subjects exercised for a mean of 8 min at a V9E that was 50% of their MVV [22]. JOHNSON et al [24] suggested that high-intensity exercise should be sustained for o10 min in order to produce significant diaphragmatic fatigue. Therefore, it was felt that a workload of 60% Wpeak would be tolerated by patients and probably result in an exercise V9E of sufficient intensity (y50% MVV) and duration (8-10 min) to cause diaphragmatic fatigue.…”