Effects of isometric elbow flexion on electromyographic spike analysis

The main objective of this research was to examine the relationship between surface electromyographic (SEMG) spike activity and force. The secondary objective was to determine to what extent subcutaneous tissue impacts the high frequency component of the signal, as well as, examining the relationship between measures of SEMG spike shape and their traditional time and frequency analogues. A total of96 participants (46 males and 50 females) ranging in age (18-35 years), generated three 5-second isometric step contractions at each force level of 40, 60, 80, and 100 percent of maximal voluntary contraction (MVC). The presentation of the contractions was balanced across subjects. The right arm of the subject was positioned in the sagittal plane, with the shoulder and elbow flexed to 90 degrees. The elbow rested on a support in a neutral position (mid pronation/mid supination) and placed within a wrist cuff, fastened below the styloid process. The wrist cuff was attached to a load cell (JR3 Inc., Woodland, CA) recording the force produced. Biceps brachii activity was monitored with a pair of Ag/AgCI recording electrodes (Grass F-E9, Astro-Med Inc., West Warwick, RI) placed in a bipolar configuration, with an interelectrode distance (lED) of 2cm distal to the motor point. Data analysis was performed on a I second window of data in the middle of the 5-second contraction. The results indicated that all spike shape measures exhibited significant (p < 0.01) differences as force increase~ from 40 to 100% MVC. The spike shape measures suggest that increased motor unit (MU) recruitment was responsible for increasing force up to 80% MVC. The results suggested that further increases in force relied on MU III synchronization. The results also revealed that the subcutaneous tissue (skin fold thickness) had no relationship (r = 0.02; P > 0.05) with the mean number of peaks per spike (MNPPS), which was the high frequency component of the signal. Mean spike amplitude (MSA) and mean spike frequency (MSF) were highly correlated with their traditional measures root mean square (RMS) and mean power frequency (MPF), respectively (r = 0.99; r = 0.97; P < 0.01).

A study of thermal decompositions of an allylic hydroperoxide /|nby Thomas A. McCarrick. -- 260 St. Catharines [Ont.] : Dept. of Chemistry, Brock University,

The thermal decomposition of 2,3-di~ethy l - J-hydr operox y- 1 - butene , p r epared f rol") singl e t oxygen, has been studied i n three solvents over the tempe r a ture r ange from 1500e to l o00e and t!1e i 111 t ial ~oncentrfttl nn r Ange from O. 01 M to 0.2 M. Analys i s of the kine tic data ind ica te s i nduced homolysis as the n ost probRble mode of d e composition, g iving rise to a 3/2 f S order dependence upon hy d.roperoxide concent :r8.tl on . Experimental activation e nergies for the decomposition were f ound to be between 29.5 kcsl./raole and 30.0 k cal./mole .• \,iith log A factors between 11 . 3 and 12.3. Product studies were conducted in R variety of solvents a s well as in the pr esence of a variety of free r adical initiators . Investigation of the kinetic ch a in length indicated a chain length of about fifty. A degenerat i ve chain branching mechanism 1s proposed which predicts the multi t ude of products which Rre observed e xperimentally as well as giving activation energies and log A factors si~il a r to those found experimentally .