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document
Impact of preinduced quadriceps fatigue on exercise response in chronic obstructive pulmonary disease and healthy subjects . Exercise intolerance in chronic obstructive pulmonary disease ( COPD ) results from a complex interaction between central ( ventilatory ) and peripheral ( limb muscles ) components of exercise limitation . The purpose of this study was to evaluate the influence of quadriceps muscle fatigue on exercise tolerance and ventilatory response during constant-workrate cycling exercise testing ( CWT ) in patients with COPD and healthy subjects . Fifteen patients with COPD and nine age-matched healthy subjects performed , 7 days apart , two CWTs up to exhaustion at 80 % of their predetermined maximal work capacity . In a randomized order , one test was performed with preinduced quadriceps fatigue and the other in a fresh state . Quadriceps fatigue was produced by electrostimulation-induced contractions and quantified by maximal voluntary contraction and potentiated twitch force ( TwQ ( pot ) ) . Endurance time and ventilatory response during CWT were compared between fatigued and fresh state . Endurance time significantly decreased in the fatigued state compared with the fresh condition in COPD ( 356 +/- 69 s vs. 294 +/- 45 s , P < 0.05 ) and controls ( 450 +/- 74 s vs. 340 +/- 45 s , P < 0.05 ) . Controls showed significantly higher ventilation and end-exercise dyspnea scores in the fatigued condition , whereas , in COPD , fatigue did not influence ventilation or dyspnea during exercise . The degree of ventilatory limitation , as expressed by the Ve/maximum voluntary ventilation ratio , was similar in both conditions in patients with COPD . We conclude that it is possible to induce quadriceps fatigue by local electrostimulation-induced contractions . Our findings demonstrate that peripheral muscle fatigue is an additional important factor , besides intense dyspnea , that limits exercise tolerance in COPD .
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Intervention_Physical
constant-workrate cycling exercise testing ( CWT )
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Intervention_Physical
CWTs
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Outcome_Physical
maximal voluntary contraction
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Outcome_Other
potentiated twitch force ( TwQ ( pot )
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Outcome_Physical
)
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Outcome_Other
Endurance time
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Outcome_Physical
and
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Outcome_Other
ventilatory response
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Outcome_Other
Endurance time
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Outcome_Other
ventilation and end-exercise dyspnea scores
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Outcome_Other
ventilatory limitation
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Outcome_Physical
Ve/maximum voluntary ventilation ratio
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Participant_Condition
preinduced quadriceps fatigue
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Participant_Condition
chronic obstructive pulmonary disease
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Participant_Condition
chronic obstructive pulmonary disease ( COPD )
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Participant_Sample-size
Fifteen patients
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Participant_Condition
COPD
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Participant_Condition
patients with COPD
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Participant_Condition
peripheral muscle fatigue