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Physiological correlates of endurance time variability during constant-workrate cycling exercise in patients with COPD.

Vivodtzev I, Gagnon P, Pepin V, Saey D, Laviolette L, Brouillard C, Maltais F - PLoS ONE (2011)

Bottom Line: W(peak), VO2(peak), VO2(VT), MVC, leg fatigue at end of CET, and HR(CET)/HR(peak) were lower in group 1 than in group 2 or 3 (p≤0.05).VO2(VT) and leg fatigue at end of CET independently predicted T(end) in multiple regression analysis (r = 0.50, p = 0.001).A large fraction of the variability in T(end) was not explained by the physiological parameters assessed in the present study.

View Article: PubMed Central - PubMed

Affiliation: Centre de Recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, Canada.

ABSTRACT

Rationale: The endurance time (T(end)) during constant-workrate cycling exercise (CET) is highly variable in COPD. We investigated pulmonary and physiological variables that may contribute to these variations in T(end).

Methods: Ninety-two patients with COPD completed a CET performed at 80% of peak workrate capacity (W(peak)). Patients were divided into tertiles of T(end) [Group 1: <4 min; Group 2: 4-6 min; Group 3: >6 min]. Disease severity (FEV(1)), aerobic fitness (W(peak), peak oxygen consumption [VO2(peak)], ventilatory threshold [VO2(VT)]), quadriceps strength (MVC), symptom scores at the end of CET and exercise intensity during CET (heart rate at the end of CET to heart rate at peak incremental exercise ratio [HR(CET)/HR(peak)]) were analyzed as potential variables influencing T(end).

Results: W(peak), VO2(peak), VO2(VT), MVC, leg fatigue at end of CET, and HR(CET)/HR(peak) were lower in group 1 than in group 2 or 3 (p≤0.05). VO2(VT) and leg fatigue at end of CET independently predicted T(end) in multiple regression analysis (r = 0.50, p = 0.001).

Conclusion: T(end) was independently related to the aerobic fitness and to tolerance to leg fatigue at the end of exercise. A large fraction of the variability in T(end) was not explained by the physiological parameters assessed in the present study. Individualization of exercise intensity during CET should help in reducing variations in T(end) among patients with COPD.

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Related in: MedlinePlus

Selected correlates of endurance time.Group mean values for i) peak workrate (Wpeak) and peak oxygen consumption (peak) during incremental exercise (panel A); ii) quadriceps strength assessed during magnetic stimulation of the femoral nerve (Twq) and maximal voluntary contraction (MVC) (panel B) and iii) symptom scores at the end of constant-workrate cycling exercise test (CET) (panel C) in group 1 (Tend<4 min, black bars), group 2 (Tend = 4–6 min, bright grey bars) and group 3 (Tend>6 min, dark grey bars) patients. * p≤0.02 versus group 2; † p≤0.01 versus group 3.
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pone-0017007-g002: Selected correlates of endurance time.Group mean values for i) peak workrate (Wpeak) and peak oxygen consumption (peak) during incremental exercise (panel A); ii) quadriceps strength assessed during magnetic stimulation of the femoral nerve (Twq) and maximal voluntary contraction (MVC) (panel B) and iii) symptom scores at the end of constant-workrate cycling exercise test (CET) (panel C) in group 1 (Tend<4 min, black bars), group 2 (Tend = 4–6 min, bright grey bars) and group 3 (Tend>6 min, dark grey bars) patients. * p≤0.02 versus group 2; † p≤0.01 versus group 3.

Mentions: Patients in group 1 had lower aerobic fitness than group 2 and/or 3 when considering Wpeak, peak (Figure 2a) and VT (Table 3). MVC was lower in group 1 as compared with group 2 (Figure 2b). Twq (Figure 2b) and the fall in Twq after CET (Table 3) were not different across the three groups.


Physiological correlates of endurance time variability during constant-workrate cycling exercise in patients with COPD.

Vivodtzev I, Gagnon P, Pepin V, Saey D, Laviolette L, Brouillard C, Maltais F - PLoS ONE (2011)

Selected correlates of endurance time.Group mean values for i) peak workrate (Wpeak) and peak oxygen consumption (peak) during incremental exercise (panel A); ii) quadriceps strength assessed during magnetic stimulation of the femoral nerve (Twq) and maximal voluntary contraction (MVC) (panel B) and iii) symptom scores at the end of constant-workrate cycling exercise test (CET) (panel C) in group 1 (Tend<4 min, black bars), group 2 (Tend = 4–6 min, bright grey bars) and group 3 (Tend>6 min, dark grey bars) patients. * p≤0.02 versus group 2; † p≤0.01 versus group 3.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3046138&req=5

pone-0017007-g002: Selected correlates of endurance time.Group mean values for i) peak workrate (Wpeak) and peak oxygen consumption (peak) during incremental exercise (panel A); ii) quadriceps strength assessed during magnetic stimulation of the femoral nerve (Twq) and maximal voluntary contraction (MVC) (panel B) and iii) symptom scores at the end of constant-workrate cycling exercise test (CET) (panel C) in group 1 (Tend<4 min, black bars), group 2 (Tend = 4–6 min, bright grey bars) and group 3 (Tend>6 min, dark grey bars) patients. * p≤0.02 versus group 2; † p≤0.01 versus group 3.
Mentions: Patients in group 1 had lower aerobic fitness than group 2 and/or 3 when considering Wpeak, peak (Figure 2a) and VT (Table 3). MVC was lower in group 1 as compared with group 2 (Figure 2b). Twq (Figure 2b) and the fall in Twq after CET (Table 3) were not different across the three groups.

Bottom Line: W(peak), VO2(peak), VO2(VT), MVC, leg fatigue at end of CET, and HR(CET)/HR(peak) were lower in group 1 than in group 2 or 3 (p≤0.05).VO2(VT) and leg fatigue at end of CET independently predicted T(end) in multiple regression analysis (r = 0.50, p = 0.001).A large fraction of the variability in T(end) was not explained by the physiological parameters assessed in the present study.

View Article: PubMed Central - PubMed

Affiliation: Centre de Recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, Canada.

ABSTRACT

Rationale: The endurance time (T(end)) during constant-workrate cycling exercise (CET) is highly variable in COPD. We investigated pulmonary and physiological variables that may contribute to these variations in T(end).

Methods: Ninety-two patients with COPD completed a CET performed at 80% of peak workrate capacity (W(peak)). Patients were divided into tertiles of T(end) [Group 1: <4 min; Group 2: 4-6 min; Group 3: >6 min]. Disease severity (FEV(1)), aerobic fitness (W(peak), peak oxygen consumption [VO2(peak)], ventilatory threshold [VO2(VT)]), quadriceps strength (MVC), symptom scores at the end of CET and exercise intensity during CET (heart rate at the end of CET to heart rate at peak incremental exercise ratio [HR(CET)/HR(peak)]) were analyzed as potential variables influencing T(end).

Results: W(peak), VO2(peak), VO2(VT), MVC, leg fatigue at end of CET, and HR(CET)/HR(peak) were lower in group 1 than in group 2 or 3 (p≤0.05). VO2(VT) and leg fatigue at end of CET independently predicted T(end) in multiple regression analysis (r = 0.50, p = 0.001).

Conclusion: T(end) was independently related to the aerobic fitness and to tolerance to leg fatigue at the end of exercise. A large fraction of the variability in T(end) was not explained by the physiological parameters assessed in the present study. Individualization of exercise intensity during CET should help in reducing variations in T(end) among patients with COPD.

Show MeSH
Related in: MedlinePlus