Sammendrag
Congestive heart failure (CHF) is characterized by low work capacity caused not only by the failing heart but possibly also by alterations in the skeletal muscles. This study investigates whether skeletal muscles of CHF patients are more fatigable than those of healthy subjects (HS) during intermittent isometric exercise. To minimize any limitation of performance by restricted cardiac output, exercise was performed by one leg¿s quadriceps muscle. Six CHF patients and six age matched healthy subjects performed right leg intermittent 6 seconds isometric knee extensor contractions every 10 seconds. The workload was chosen so that the subject was exhausted after 7-18 min. Maximal voluntary contraction (MVC) and electrical stimulation of the muscle at 20 and 50 Hz were performed before the exercise, at 3 and 9 min of exercise, and immediately after exhaustion. MVC tended to be lower in CHF patients compared to HS. When corrected for a lower muscle cross sectional area (CSA), there was no difference. MVC per CSA fell by 35 ±18 (mean ±SD) and 28 ±12 % for CHF and HS respectively from rest to exhaustion which was not significantly different (NS). Absolute workload, but not relative or time to exhaustion, was significantly different for CHF patients compared to HS (216 ¿64 N vs. 312 ¿71 N, p
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