Average Muscle Fiber Conduction Velocity Research Articles

The muscle fiber conduction velocity and power spectra in familial hypokalemic periodic paralysis.

Surface EMG has been used to determine the average muscle fiber conduction velocity (MFCV) and power spectra of the m. biceps of 10 patients and 15 asymptomatic offspring of a large kinship with familial hypokalemic periodic paralysis (HOPP). The MFCV of the patients was 3.37 +/- 0.35 m/sec (mean +/- SD, n = 9), the median frequency (Fmed) of the power spectra was 55.0 +/- 5.8 Hz (mean +/- SD, n = 9), both values are significantly (P0.001, Student's t-test) lower than the control values: MFCV = 4.55 +/- 0.33 m/sec; Fmed = 88.6 +/- 15.5 Hz (mean +/- SD). In 6 of the 15 asymptomatic relatives, the surface EMG results were also abnormal. It is concluded that the MFCV is reduced in familial HOPP. This results in a predominantly low-frequency content of the power spectra, thereby providing a new model for studying the relationship between the MFCV and the frequency spectrum of surface EMG. Asymptomatic relatives that have inherited the disease probably can be detected with this method.

On-line measurement of muscle fibre conduction velocity: analysis and optimization of performance

Measurement of the average muscle fibre conduction velocity from surface electromyographic signals has important applications in the study of muscle fatigue and in ergonomics. In this paper, a two-channel hardware polarity correlator (which estimates 256 correlation coefficients per channel at a sampling rate of 18.58 kHz) and a specially designed surface electrode unit, are used to investigate various factors affecting the measurement reliability: electrode dimensions; EMG preprocessing to make the estimated correlation function more suitable for time delay measurement; and the manner in which velocity estimates, measured simultaneously from two different sections of the same muscle, are related. All the tests were performed on the biceps brachii when under medium tension; some tests involved tensions which led to muscle fatigue. Results showed that smaller electrode dimensions (i.e. smaller electrode units) and EMG preprocessing to increase its effective bandwidth, give more reliable measurements. Further, it was found that the estimated mean velocity is dependent on the location of the electrode unit on the muscle, and that at certain locations no reliable estimates can be obtained. The preliminary results obtained with muscle fatigue indicate that the estimated conduction velocity decreases, but not uniformly, across the muscle.

Changes of the average muscle fiber conduction velocity during a varying force contraction

The average conduction velocity of muscle fibers measured with a surface electrode has been reported to increase with the level of contraction force. To clarify the factors causing this increase, the authors decomposed the interference surface EMG signal into its constituent motor unit action potentials and compared the average conduction velocity with the conduction velocity measured at the individual discharges of motor units. The conduction velocity within individual motor units increased with the contraction force and contributed to the increase of the average conduction velocity. However, the increase of the conduction velocity within motor units was relatively small and was insufficient to cause the increase of the average conduction velocity. This result indicates that the motor units recruited at higher thresholds of force should have higher conduction velocities.

Relationship between average muscle fibre conduction velocity and EMG power spectra during isometric contraction, recovery and applied ischemia.

The relationship between muscle fibre conduction velocity (MFCV) and the power spectrum of surface EMGs in 3 human volunteers was studied during isometric contractions at 40% maximum voluntary contraction. In addition, the recovery of these two parameters was measured during short lasting contractions at the same force level every 30 s. The recovery phase was also studied during ischaemia, thereby preventing the recovery of MFCV. The mean MFCV was calculated by the cross-correlation method. The measurements were facilitated by a real-time estimation of the cross-correlation and the MFCV and by a graphic display of the digitised signal. During contraction a nearly linear relation was found between MFCV and the median frequency of the power spectrum (MPF). During recovery this relationship was lost in one subject: MPF restored much faster then MFCV. During recovery under ischemia MFCV did not recover, but MPF recovered partially in all subjects. It is concluded that the shift of the power spectrum to lower frequencies during fatigue cannot be explained by changes in MFCV alone. Central mechanisms also influence the power spectrum and studying the recovery of local muscle fatigue during ischemia may separate these influences from that of MFCV on the power spectrum during fatigue.

Muscle metabolism during isometric exercise performed at constant force.

Muscle metabolism during isometric exercise performed at constant force.

Effect of prior activity on properties of different types of motor units.

Effect of prior activity on properties of different types of motor units.C B Olson, and C P Swett JrC B Olson, and C P Swett JrPublished Online:01 Jan 1971https://doi.org/10.1152/jn.1971.34.1.1MoreSectionsPDF (3 MB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited BySpike-triggered average torque and muscle fiber conduction velocity of low-threshold motor units following submaximal endurance contractionsDario Farina, Lars Arendt-Nielsen, and Thomas Graven-Nielsen1 April 2005 | Journal of Applied Physiology, Vol. 98, No. 4Activity-independent neural influences on cat soleus motor unit phenotypes29 July 2002 | Muscle & Nerve, Vol. 26, No. 2Motor unit behaviour and contractile changes during fatigue in the human first dorsal interosseus1 August 2001 | The Journal of Physiology, Vol. 534, No. 3Pattern of Pulses That Maximize Force Output From Single Human Thenar Motor UnitsC. K. Thomas, R. S. Johansson, and B. Bigland-Ritchie1 December 1999 | Journal of Neurophysiology, Vol. 82, No. 6Posttetanic potentiation of human dorsiflexorsDeborah D. O’Leary, Karen Hope, and Digby G. Sale1 December 1997 | Journal of Applied Physiology, Vol. 83, No. 6Effects of high-frequency (500–1,000 Hz), indirect stimulation on slow and fast muscle relevant to orthotic applicationsJournal of Electromyography and Kinesiology, Vol. 2, No. 3A comparison of electromyographic and mechanical fatigue properties in motor units of the cat hindlimbBrain Research, Vol. 327, No. 1-2The fast twitch motor units of cat ankle flexors. 1. Tripartite classification on basis of fatigabilityBrain Research, Vol. 134, No. 1The effect of activation history on tension production by individual muscle unitsBrain Research, Vol. 109, No. 3Properties of motor units in the first deep lumbrical muscle of the cat's footBrain Research, Vol. 98, No. 1The motor units of cat medial gastrocnemius: Speed-size relations and their significance for the recruitment order of motor unitsBrain Research, Vol. 91, No. 2Histochemical composition, contraction speed and fatiguability of rat soleus motor unitsJournal of the Neurological Sciences, Vol. 20, No. 2 More from this issue > Volume 34Issue 1January 1971Pages 1-16 https://doi.org/10.1152/jn.1971.34.1.1PubMed4250555History Published online 1 January 1971 Published in print 1 January 1971 Metrics

Conduction velocity in ischemic muscle: effect on EMG frequency spectrum.

Conduction velocity in ischemic muscle: effect on EMG frequency spectrum.