Diaphragmatic Fatigue after Exercise in Healthy Human Subjects

Abstract

The purpose of this study was to determine whether diaphragmatic fatigue occurs after high-intensity constant-load whole-body exercise to volitional exhaustion. Ten sedentary subjects with a maximal oxygen uptake of 2.52 +/- 0.47 L/min were studied. Subjects exercised on a bicycle ergometer at 80% of their maximal working capacity until volitional exhaustion. Minute ventilation during the last minute of exercise was 89.9 +/- 13.6 L/min, which represented 50 +/- 6% of the subjects' 12-s maximal voluntary ventilation. During the last minute of exercise, mean inspiratory esophageal pressure was 18.1 +/- 5.3 cm H2O, which represented only 15 +/- 4% of the subjects' maximal static inspiratory pressure. Bilateral transcutaneous supramaximal phrenic nerve stimulation was performed before and 10, 30, 45 and 60 min after exercise. Twitch diaphragmatic pressure (twitch Pdi) was significantly decreased after exercise in seven of the 10 subjects. For the group as a whole, twitch Pdi fell from 28.9 +/- 3.7 cm H2O during control to 23.9 +/- 5.1 cm H2O at 10 min after exercise (p< 0.005). The fall in twitch Pdi was due to a significant decrease in twitch esophageal pressure from 19.6 +/- 4.3 cm H2O during control to 15.5 +/- 4.9 cm H2O (p < 0.001). Twitch gastric pressure was not significantly different: 8.7 +/- 4.0 cm H2O, compared with 9.2 +/- 3.8 cm H2O during control. Twitch Pdi recovered to 93 +/- 7% of control values at 60 min after exercise. The fall in twitch Pdi after exercise indicates that diaphragmatic fatigue can occur following heavy endurance exercise in sedentary healthy persons.

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).…”

Diaphragmatic function after intense exercise in congestive heart failure patients

“…The authors9 laboratory has considerable experience with CMS and transcutaneous electrical stimulation in normal subjects and patients [6,12,[19][20][21][22]. CMS was utilised in the present study because this method is well tolerated and technically easier to perform than transcutaneous electrical stimulation.…”

“…Normal subjects demonstrated evidence of diaphragmatic fatigue after voluntary hyperpnoea at a V9E of 60% MVV sustained for y8 min [21]. 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.…”