EARLY DEVELOPMENT OF EMG LOCALIZED MUSCLE FATIGUE IN HAND MUSCLES OF PATIENTS WITH CHRONIC HEART-FAILURE

Background: Patients with chronic heart failure (CHF) frequently compl ain of fatigue and exercise intolerance that are not directly related to the severity of cardiac failure. A not well-defined muscle function impairment is generally considered the cause of such symptoms. The fr equency compression of electromyographic (EMG) signal power spectrum d uring isometric contractions is commonly accepted as an index of the f atigue occurring in the muscle (localized muscle fatigue). Purpose and Methods: The purpose of the study was to evaluate muscle fatigue deve lopment in a selected group of CHF patients by studying the compressio n of the EMG signal power spectrum. The first dorsal interosseus of th e right, dominant hand was investigated at two levels of contraction: 40% and 80% of the maximal voluntary contraction (MVC). Results: In CH F patients there was early development of localized muscle fatigue dur ing the high level of contraction (80% of MVC). Conclusion: This study demonstrates the presence of an early development of localized muscle fatigue in CHF patients and confirms the possibility of an increased glycolytic metabolism. Moreover, the changes seem to show that muscle impairment is not limited to large muscles, but also occurs in small m uscles of the hands, frequently used during daily activities. Finally, this study confirms the validity of EMC spectral analysis techniques in evaluating muscle fatigue of CHF patients, suggesting a possible us e in the rehabilitation of such patients when the technique is correct ly used. (C) 1998 by the American Congress of Rehabilitation Medicine and the American Academy of Physical Medicine and Rehabilitation.