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Biomechanical efficiency is decreased in heart failure during low‐level steady state and maximal ramp exercise
Author(s) -
Levy Wayne C.,
Maichel Barbara A.,
Steele Natalie P.,
Leclerc Kenneth M.,
Stratton John R.
Publication year - 2004
Publication title -
european journal of heart failure
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.149
H-Index - 133
eISSN - 1879-0844
pISSN - 1388-9842
DOI - 10.1016/j.ejheart.2004.02.010
Subject(s) - heart failure , medicine , watt , cycle ergometer , cardiology , physical therapy , heart rate , blood pressure , power (physics) , physics , quantum mechanics
Background: Previous studies of biomechanical efficiency (external work/energy input – Watt/O 2 consumed) in heart failure (HF) using cardiopulmonary exercise testing (CPET) and magnetic resonance spectroscopy (MRS) have had discordant results with increased efficiency by CPET and decreased efficiency by MRS. Aims: Compare biomechanical efficiency of HF subjects and normal controls during steady state (SS=35 W for 6 min) and ramp cycle ergometer exercise. The hypothesis was that HF subjects would have impaired biomechanical efficiency that correlated with HF symptoms. Methods: Biomechanical efficiency used the actual V o 2 during exercise and recovery. Gross (V o 2 above zero), Net (V o 2 above the resting V o 2 ) and Work (V o 2 above the unloaded pedaling V o 2 ) efficiencies were calculated. Results: HF subjects had an 18% higher V o 2 during SS exercise ( P =0.029). Biomechanical efficiency was reduced during SS exercise (gross −15%, P =0.019, net −15%, P =0.062, and work −35%, P =0.002). Gross Efficiency during SS exercise had the strongest correlation with HF symptoms ( r =0.55). During ramp exercise gross (−26%), net (−10%) and work (−8%) biomechanical efficiency were all reduced (all P< 0.05). The slope of the V o 2 /Watt relationship during ramp exercise had the best correlation with HF symptoms ( r =0.46). Conclusions: HF subjects have an increased O 2 cost/Watt during SS and ramp exercise that correlates with HF symptoms of fatigue and breathlessness. Methods to improve biomechanical efficiency in HF subjects by exercise training or medications may improve the symptoms and the impaired exercise capacity associated with HF.