Major limitations to exercise performance
3 important questions on Major limitations to exercise performance
Write down a list of arguments that favour the proposition that inadequate energy supply to the respiratory and locomotor muscles is THE major limitation to exercise performance in patients with COPD.
Evidence to support this proposition (Aliverti and Macklem:
High work of breathing (Wresp) in COPD eventually leads to:
1. vasoconstriction in peripheral muscles (via respiratory muscle metaboreflex) -> plateau in limb muscle perfusion -> lactic acid production at low exercise level -> low exercise performance -> disuse -> lower oxidative capacity of the peripheral muscles
2. derecruitment of expiratory muscles (learned response) -> dynamic hyperinflation Additional evidence: administration of oxygen/heliox/non-invasive ventilation reduces Wresp -> more energy for locomotor muscles -> better exercise performance
High work of breathing (Wresp) in COPD eventually leads to:
1. vasoconstriction in peripheral muscles (via respiratory muscle metaboreflex) -> plateau in limb muscle perfusion -> lactic acid production at low exercise level -> low exercise performance -> disuse -> lower oxidative capacity of the peripheral muscles
2. derecruitment of expiratory muscles (learned response) -> dynamic hyperinflation Additional evidence: administration of oxygen/heliox/non-invasive ventilation reduces Wresp -> more energy for locomotor muscles -> better exercise performance
Write down a list of arguments that favour the proposition that lower limb muscle dysfunction is THE major limitation to exercise performance in patients with COPD.
1. Evidence to support this proposition (Debigare and Maltais, J Apply Physiol 2008): Quadriceps strength strongly correlates with exercise capacity, independent of FEV1
2. Exercise limitation persists after lung transplantation with complete restoration of ventilatory capacity
3. Weak COPD patients can hardly improve exercise tolerance with bronchodilation 4. Exercise training improves exercise tolerance by improving lower limb muscle function
2. Exercise limitation persists after lung transplantation with complete restoration of ventilatory capacity
3. Weak COPD patients can hardly improve exercise tolerance with bronchodilation 4. Exercise training improves exercise tolerance by improving lower limb muscle function
Write down a list of arguments that favour the proposition that dynamic hyperinflation is THE major limitation to exercise performance in patients with COPD
Evidence to support this proposition (O’Donnell and Webb, J Apply Physiol 2008): Dynamic hyperinflation -> low inspiratory reserve volume (IRV) -> mechanical constraints/impaired cardiovascular function -> alveolar hypoventilation and increased dyspnea
Additional evidence:
1. bronchodilators improve exercise tolerance by reducing (dynamic) hyperinflation 2/ bronchodilation reduces oxygen cost of breathing (Wresp), improves respiratory muscle strength and efficiency
Interventions like lung volume reduction surgery, oxygen therapy and exercise training improve operating lung volumes (IC and IRV), dyspnea sensation and exercise performance
Additional evidence:
1. bronchodilators improve exercise tolerance by reducing (dynamic) hyperinflation 2/ bronchodilation reduces oxygen cost of breathing (Wresp), improves respiratory muscle strength and efficiency
Interventions like lung volume reduction surgery, oxygen therapy and exercise training improve operating lung volumes (IC and IRV), dyspnea sensation and exercise performance
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