PT  - JOURNAL ARTICLE
AU  - Elisabeth C. Eberle
AU  - Thomas Wüthrich
AU  - Christina M. Spengler
TI  - Diaphragm and quadriceps muscle fatigue in self-paced cycling exercise of different durations
DP  - 2011 Sep 01
TA  - European Respiratory Journal
PG  - p2109
VI  - 38
IP  - Suppl 55
4099  - http://erj.ersjournals.com/content/38/Suppl_55/p2109.short
4100  - http://erj.ersjournals.com/content/38/Suppl_55/p2109.full
SO  - Eur Respir J2011 Sep 01; 38
AB  - Introduction: Individuals are believed to pace cycling intensity in a time trial (TT) such that the level of quadriceps muscle fatigue (QF) attained is similar independent of cycling conditions. We aimed to assess whether diaphragm fatigue (DF), known to affect leg muscle fatigue, would also reach similar levels between different tests.Methods: 12 healthy, young athletes (67.1±6.3 ml min-1 kg-1) performed 15 and 30min cycling time trials (15TT, 30TT; randomised), on two different days. DF and QF were assessed by measuring reductions in esophageal and gastric (transdiaphragmatic) pressure/quadriceps force during magnetic phrenic/femoral nerve stimulation after exercise relative to before (ΔPdi,tw; ΔQtw).Results: The average degree of ΔPdi,tw did not differ -21.2±12.8% (15TT) vs. -17.6±9.3% (30TT; p=0.228) while ΔQtw of the shorter and more intensive test -34.0±5.7% (15TT) was significantly larger than that of the longer test -29.5±6.9% (30TT; p=0.044). Individual between-test differences of ΔPdi,tw did not correlate with those of ΔQtw. However, individual ΔPdi,tw of both TTs taken together significantly correlated with the workload of the finish (last 30 s) relative to the maximal workload (R2=0.30; p=0.005).Conclusion: The present work does not support the notion that the level of QF is the same, independent of cycling TT conditions. Knowing that DF develops early during exercise, these findings may indicate that DF possibly affected finish intensity via afferent feedback from the fatigued diaphragm, attenuating central motor output to working limb muscles.