End-expiratory (EELV) and end-inspiratory (EILV) lung volumes as a percentage of total lung capacity (TLC), tidal volume (V_T) and inspiratory capacity (IC) before (Baseline), 5 minutes after the start of constant-load cycling (5 min) and at exhaustion (Exh) (Panel A).

<p>Changes in IC during the same conditions (Panel B). *, significant differences from Baseline (P<0.05).  </p

Correlation of the percentage reduction from baseline in transdiaphragmatic pressure evoked during cervical magnetic stimulation (ΔP_di,tw) with the percentage reduction from Baseline in quadriceps strength evoked during femoral magnetic stimulation immediately after exhaustive constant load cycling (ΔQ_tw; Panel A).

<p>Correlation of ΔP_di,tw (Panel B) and the percentage reduction from Baseline of gastric pressure evoked during thoracic magnetic stimulation immediately after exhaustive constant load cycling (ΔP_ga,tw ; Panel C) with the reduction in IC at exhaustion (ΔIC).</p

Individual changes in quadriceps strength evoked by femoral magnetic stimulation (Q_tw; Panel A), transdiaphragmatic pressure evoked by cervical magnetic stimulation (P_di,tw; Panel B) and gastric pressure evoked by thoracic magnetic stimulation (P_ga,tw; Panel C) from before (Baseline) the constant-load cycling to immediately after exhaustion (Exh).

<p>The thick line indicates the group average reduction. The dotted line indicates the 15% reduction threshold for significant amount of muscle fatigue. *, significant group difference from Baseline (P<0.05).</p

Arterial oxygen saturation (SpO₂) during free breathing (FB) and during 20 min of PEEP-10 breathing at 4,350m of altitude.

<p>* significantly different compared to FB (*** p < 0.001). </p

Minute ventilation in all experimental conditions.

<p>See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0085219#pone-0085219-g001" target="_blank">Figure 1</a> for abbreviations. * significant difference between two conditions (p < 0.05).</p

Arterial blood oxygen saturation (S_pO₂) in all experimental conditions.

<p>FB, free breathing with no PEEP device; PEEP-0/5/10, Positive end expiratory pressure at 0, 5 and 10 cmH₂O; T10, same ventilatory level as measured in PEEP-10 condition but without PEEP device; PLB, pursed lips breathing. * significant difference between two conditions (* p < 0.05, **, p < 0.01, *** p < 0.001).</p

Changes in quadriceps oxyhemoglobin concentration (O₂Hb, expressed as delta from the free breathing condition immediately before) in all experimental conditions.

<p>See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0085219#pone-0085219-g001" target="_blank">Figure 1</a> for abbreviations. * significant difference between two conditions (*p < 0.05, **p < 0.01).</p

Expiratory esophageal and gastric pressure swing (P_es min-max and P_ga min-max) in all experimental conditions.

<p>See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0085219#pone-0085219-g001" target="_blank">Figure 1</a> for abbreviations. * significant difference between two conditions (*p < 0.05, **p < 0.01, ***p < 0.001).</p