Validation of estimated muscle fiber conduction velocity with the normalized peak-averaging technique.

To estimate muscle fiber conduction velocity (MFCV), the normalized peak-averaging technique was developed along with complementary software and reported in a previous study. Electromyograms were recorded from the vicinity of end-plate zones (EMG data 1) and a site farther from the end-plates and distal tendons (EMG data 2) of biceps brachii muscles using surface array electrodes during 50% maximal voluntary isometric contractions in ten healthy volunteers. The MFCV values obtained with normalized peak-averaging technique were compared to those obtained with the cross-correlation technique and examined by computer simulation of the MFCV distribution. The MFCV values obtained with normalized peak-averaging technique highly correlated with those obtained with cross-correlation technique in both EMG data 1 and EMG data 2. It was also confirmed that MFCV values obtained from EMG data 1 were distributed much more widely than those obtained from EMG data 2. These results show the clinical usefulness of normalized peak-averaging technique for the detailed assessment of MFCV.

Muscle fiber conduction velocity estimation by using normalized peak-averaging technique.

In order to compute the muscle fiber conduction velocity (MFCV) and to clarify how action potentials are conducted, the normalized peak-averaging technique (NPAT) was newly employed together with computer softwares. Twelve pairs of surface electromyograms were selected from biceps brachii muscles during contraction at a level of 50% of the maximum voluntary isometric contraction in seven healthy volunteers. The techniques to compute MFCV from the time delay of the peaks (P-NPAT) and from the cross correlation (CC-NPAT) of averaged pulses were compared to the cross-correlation technique (CCT). The spread rate of averaged pulses was computed to estimate the spread of MFCVs in different motor units. Tri-phasic averaged pulses were obtained clearly by averaging more than 500 detected pulses. The P-NPAT and CC-NPAT highly correlated with the CCT in the computed MFCVs. The MFCVs obtained by P-NPAT were generally larger than those obtained by CCT, and the spread rates had in the definite values. These results suggest that the MFCV could be computed and the spread of MFCVs would be estimated from averaged pulses. The MFCV of a patient with myotonic dystrophy was also studied, and it was suggested that the NPAT would be clinically useful.

Relationship between the oxygen uptake during cardiopulmonary exercise testing and left ventricular function in patients with acute myocardial infarction.

The relationship between exercise capacity and left ventricular function has been evaluated in 35 patients with acute myocardial infarction (34 males and 1 female; mean age 55.5 ± 7.1 years). Single photon emission computed tomography (SPECT) was used to measure left ventricular function in the acute phase (4.9 ± 2.2 days after onset) and the chronic phase (188.5 ± 22.9 days after onset). More than 10% left ventricular dilatation from the acute phase to the chronic phase was defined as remodeling (RM) and the subjects were divided into 2 groups: RM and non-RM. Cardiopulmonary exercise testing was performed at 1 month (1M), 3 months (3M) and 6 months (6M) after onset. In the RM group, anaerobic threshold (AT) and peak oxygen uptake (Peak ) did not change significantly. In the non-RM group, AT was 15 ± 1 (ml/min/Kg) at 1M, 16 ± 2 at 3M and 18 ± 4 at 6M. Peak was 26 ± 3 (ml/min/Kg) at 1M, 30 ± 2 at 3M and 32 ± 3 at 6M. Both parameters in the chronic phase increased significantly compared with those at 1M (p<0.002 and p<0.0001). Thus, change in exercise capacity would correlate with change in left ventricular function.