There is a dearth of knowledge on the functional organization of the anatomically complex human masseter muscle. Limited physiological studies suggest a functional organization which may differ significantly from human limb muscles. The present studies aimed to examine the putative relationship between structure and function in the human masseter muscle as a basis for understanding function and dysfunction in human jaw muscles. In the first experiment single motor unit (SMU) activity was recorded from pairs of recording sites distributed throughout the masseter muscle. In each case SMU activity at a chosen location was used as a reference to search for synchronized SMU activity at another selected site. The locations of the needle tips were estimated in 3-dimensions (3-D) by means of an optical system, then transferred to 3-D reconstructions derived from Magnetic Resonance images. This approach permitted calculation of the linear distances between verified muscle recording sites. The mean separation of the sites from which synchronous SMU activity could be recorded was 8.8±3.4mm. The putative territories had a preferred orientation in the antero-posterior axis. Motor unit territories were larger than described previously, and appeared to be related to anatomical compartments. The second experiment involved recording activity from stereotactically mapped masseter SMUs. In each case, the lowest sustainable firing frequency (LSFF) was reached by slow increases and decreases in voluntary firing rate, followed by sustained firing at the lowest possible rate. Pulse-discrimination and digital sampling of consecutive inter-spike intervals (ISIs) were then used to measure LSFF for 2-6 separate occlusal and postural tasks to which each unit contributed. There were significant differences between mean ISIs for the tasks performed by most units, which suggests descending drive to masseter units is highly task-dependent. There were also regional differences in unit task specificities. In the third paradigm, reflex SMU activity was recorded from units in the masseter muscle and the inferior head of the lateral pterygoid muscle. Bipolar electrodes fixed to the gingiva near the maxillary canine delivered single pulses of 1ms duration at sub-noxious levels of intensity. At constrained firing frequencies (10, 15Hz), pulses were injected sequentially, with increasing delays, after preselected spikes. More profound inhibition occurred in units firing at 10 than 15Hz. There were significant differences in masseter inhibitory responses when the unit task varied. Reflex inhibition in masseter and lateral pterygoid SMUs is highly frequency-dependent, and also task-dependent in masseter units. The fourth study involved recording activity from SMUs in the masseter muscle. A midline load cell was fixed to the incisor teeth and aligned either perpendicular (P) or 30 degrees anterior (A) to the occlusal plane, without altering jaw position. A rigid spike-triggered averaging (STA) paradigm was used to extract the contribution of individual SMUs to the overall force at load cell orientations P and A. Spikes preceded or followed by an interval of less than 100ms were rejected prior to averaging. At background bite forces from 0.06-8N, the isometric forces apparently developed by individual units varied randomly with load cell orientations, (P range 36.2±19.6mN; A range 38.2±28.4mN). All units could be fired slowly with varying degrees of muscle coactivation, in some instances without contact on the load cell. The use of STA as a method for determining SMU tension in the masseter muscle appears to be task-dependent and in the presence of coactivation may be inappropriate. The findings collectively indicate the heterogeneous nature of SMU behaviour in the human masseter muscle which is consistent with internal muscle compartments based on anatomical features and functional behaviour. There thus appear to be both physiological and anatomical substrates for differential motor control of selected regions of the human masseter muscle. / Dentistry, Faculty of / Graduate

Power and strength training, using conventional techniques, has been studied by several researchers. Investigations into the use of different training methods and their effect on power and strength development are continually being studied and re-assessed. Recently, the use of faradic or electrical stimulation has become an interesting alternative method, although much controversy surrounds this technique. It has been reported by Johnson et al. (1977) and Kots (1977) that faradic stimulation is used with success as part of a strengthening program by elite Soviet athletes. The combined effects of a program consisting of exercise as well as electrical stimulation was undertaken to determine the muscular power and strength potentials. The main objective of this study was to compare power and strength changes between equated groups employing the following training techniques: electrical stimulation plus isokinetic exercise, isokinetic exercise and electrical stimulation, respectively. Twenty-seven, moderately trained, female subjects, nine per group, were tested on three separate occasions. During the first session, height, weight, left and right quadriceps power evaluation, time to peak tension of the muscle contraction at the four velocities :(30, 100, 180 and 0 degrees per second) and two thigh girth measurements were determined. The three groups were equated for power after the pretest was conducted. The second and third testing sessions assessed the power and time to peak tension of the non-dominant leg at the four velocities and patellar and gluteal thigh girths. A significant difference for power was found between the pre and post tests and the pre and mid tests for the combined groups during the six week period of training. Although no difference was found between each of the three groups, the results indicated that programs involving electrical stimulation and isokinetic exercise, isokinetic exercise and electrical stimulation only, are potentially effective in improving muscular power and strength in normal subjects. The study revealed that one method was not superior to another after six weeks of training. There was significant power differences between the pre and post tests and pre and mid tests at the slow isokinetic speeds of 30° and 0° per second. Since the training was conducted at the speeds of 30° and 0° (isometric) per second, the slow testing speeds reflected neural adaptation and muscular recruitment when the specificity of training theory is considered. These findings imply that power and strength training benefits are limited to speeds used during training. During the six week training period, time to peak maximal torque and hypertrophy of the quadriceps muscle group did not alter significantly when examining the means of all three groups. / Education, Faculty of / Curriculum and Pedagogy (EDCP), Department of / Graduate

After knee surgery, the development of leg strength and size to its original levels are important requirements in the recovery. The major aim in the rehabilitation of a meniscectomy is to return the injured limb to its original size by a program of active exercises. Failure to do this may result in limited activity and re-injury to the knee joint A program of electrical stimulation has been found to be effective in controlling muscle atrophy during the time of denervation in animals and humans (in animals - Schimrizk et a 1976; Herbison et al, 1973, 1971; Stillwell et al, 1962 and Guttman and Guttman, 1942; in humans - Osbourne, 1951 and Jackson and Seddon, 1945). At the present time no studies have been done to determine if electrical stimulation will be effective in controlling muscle atrophy in normally innervated muscles during the period of immobilization. The purpose of this investigation was to determine the effects of a 10-12 day program of electrical stimulation on the control of muscle atrophy and strength loss during the period of immobilization. A subproblem of this investigation was to determine the relationship between muscle atrophy and strength loss. The subjects for this study were eighteen patients undergoing a meniscectomy operation (mean age 22.7 yrs.). Subjects were rated according to strength per body weight and assigned to a control or an experimental group. The experimental group participated in a five session program of electrical stimulation in addition to a standard physiotherapy program. The control group participated only in the standard physiotherapy program. The electrical stimulation consisted of five sessions each lasting ten minutes. Ninety muscle contractions were made during the ten minute session. The sessions were held on weekdays within a 10-12 day period of the operation. The first session was held 48 hours after the operation. In the first two sessions the leg was stimulated at the immobilized angle and in the remaining three sessions the leg was stimulated at 115 degrees of extention. All subjects were tested one day prior to the operation and at the end of the 10-12 day period for thigh volume and maximal isometric leg strength. The following hypotheses were tested for significance at the .05 level. 1. The use of electrical stimulation in addition to the standard physiotherapy program will show less muscle atrophy as compared to the standard physiotherapy program. 2. The use of electrical stimulation in addition to the standard physiotherapy program will maintain a higher level of original isometric strength as compared to the standard physiotherapy program. 3. There is a positive linear relationship between muscle atrophy and strength loss. Analysis of variance revealed that hypothesis #1 is supported at the .01 level and hypothesis #2 is not supported at the .05 level of significance. The Pearson Product Moment Correlation showed that hypothesis #3 is supported when the two groups were combined and for the control group only at the .01 level of significance, but not for the treatment group only, at the .05 level. / Education, Faculty of / Curriculum and Pedagogy (EDCP), Department of / Graduate

The muscle spindle is invested by a capsule of continuous, multilayered perineural epithelium, creating a periaxial space around the intrafusal muscle fibres and their innervation. The ultrastructural permeability of the muscle spindle capsule was assessed in anterior tibialis muscles of adult mice after systemic injection of the exogenous protein tracer, horseradish peroxidase (HRP). After varying time intervals ranging from 2 to 240 minutes, anesthetized animals were systemically perfused with fixative. Muscles were then removed and processed by routine cytochemical methods in order to demonstrate the distribution of peroxidase activity. While bare capillaries were never encountered within the intracapsular periaxial space of the muscle spindle, they frequently and intimately abut against its outer perineural capsule. Two minutes after injection of HRP, reaction product was localized in capillary endothelial plasmalemmal vesicles, just prior to its accumulation in the tissue space immediately surrounding the subjacent capsular perineurium in the equatorial region. In the polar region of the muscle spindle capsule, however, there was evidence of reaction product in the periaxial space at the same two minute time period. Ten minutes after administration of the tracer, a small population of perineural vesicles contained HRP. At the 12.5 minute interval, the sarcolemmae and T-tubules of polar intrafusal muscle fibres were subsequently labelled. Equatorial (sensory) regions of muscle spindles appeared to be relatively less permeable to the entrance of the tracer than more distal polar regions. By 15 minutes post-injection, HRP was seen traversing the perineural capsule in equatorial zones; and by 30 minutes, perineural and Schwann cell phagocytosis of the exogenous protein was extensive. / Medicine, Faculty of / Cellular and Physiological Sciences, Department of / Graduate

Muscle homeostasis and regeneration are complex cellular processes orchestrated by muscle stem cells and their interaction with their stem cell microenvironment. The fate of a muscle stem cell is influenced by different conditions such as muscle injury, cold stress, or disease. During extensive muscle repair and in the context of muscular dystrophy, we identified the critical function of the Epidermal Growth Factor Receptor (EGFR) in establishing cell polarity and in turn the efficient formation of myogenic progeny able to repair muscle. Using a novel drug screen, we identified the p53 protein to regulate muscle stem cell fate decision to repress the formation of brown adipose tissue as a means to regulate whole-body metabolism. To increase the impact of our research we also optimized protocols evaluating mouse satellite cell transplantation to delineate stem cell hierarchy and developed a new paradigm to model human muscle stem cell fate to better translate our findings into the clinical arena. These findings reveal the tunable nature of stem cell fate decisions and highlight the development of research tools to accelerate the translation of research findings to improve human health.

BACKGROUND: Strategic limb occlusion applied after exercise (PEIC) may expedite recovery, not just in directly affected tissue, but over the entire body via circulating factors. METHODS: Twenty active college-age males took part in a single-blind randomized crossover design. Participants underwent intervention and SHAM treatments after strenuous exercise sessions. Peak Torque production and soreness measures were gathered directly before and 24-hours after two exercise sessions. STATISTICAL ANALYSES: A 2 x 2 repeated measures analysis of variance with sidak corrections (significance of p<0.05) was used to analyze peak torque and VAS scores. RESULTS: Significance was not observed between any associated pre- and post-peak torque test (p > 0.05). Post-treatment VAS scores were statistically higher than pre-treatment for all conditions except pre-and post-intervention in the direct leg (P = 0.096). DISCUSSION: The application of PEIC was not associated with any significant differences in peak torque production or soreness measures.

No description available.

ABSTRACT The aim of my thesis is to further investigate the mechanisms underlying inflammatory muscle pain. Despite numerous studies investigating the mechanisms of inflammatory hyperalgesia, little is known of the mechanisms underlying inflammatory muscle hyperalgesia. Using rats as experimental animals, I investigated inflammatory hyperalgesia in muscle and compared it to that of inflamed cutaneous tissue. I injected carrageenan, a plant-origin polysaccharide, into leg muscle and into the hind paw of rats, and measured the behavioural response, as well as cytokine changes, in both plasma and inflamed tissue. Carrageenan induced inflammatory hyperalgesia but the cytokine cascade was not the same in muscle and cutaneous tissue. At no time following carrageenan injection was muscle tumour necrosis factor alpha (TNF-&) concentration elevated above that of muscle injected with saline. TNF-& is a key inflammatory mediator in cutaneous tissue, but apparently not in muscle. Interleukin-1) (IL-1)) and interleukin-6 concentrations also were different during muscle inflammation compared to those of cutaneous inflammation. IL-1) and IL- 6 concentrations, following carrageenan injection, were elevated later in muscle compared to in cutaneous tissue. IL-1) is a potent sensitizer of nociceptors in cutaneous tissue, and also may play an important role in sustaining muscle pain, but it is unlikely to be an initiator of the inflammatory muscle hyperalgesia. In the course of comparing muscle hyperalgesia and cutaneous hyperalgesia, I aimed to identify whether these differences in cytokine concentrations were unique to muscle tissue or if similar differences in cytokine concentrations existed between the hind paw and other cutaneous sites. To explore an alternative cutaneous tissue site, I injected carrageenan into the rat tail and measured the behavioural response, changes in cytokine concentrations and histological changes. Elevations of pro-inflammatory cytokines occurred concurrently with the infiltration of leukocytes into the inflamed tail tissue with the thermal and mechanical hyperalgesia similar to that found in the hind paw. Different mechanisms therefore appear to underlie muscle and cutaneous inflammatory hyperalgesia, regardless of the site used to investigate cutaneous inflammation. One of the consequences of the poor understanding of muscle pain is the lack of a reliable regimen for treating human muscle pain, including delayedonset muscle soreness (DOMS). DOMS, which has a partial inflammatory pathogenesis, is not relieved by non-selective cyclo-oxygenase inhibitors. This phenomenon may be that prostaglandins are not produced peripherally or centrally, when muscle tissue is damaged. I investigated the effect of inhibiting cyclo-oxygenase-2, the isoform released during inflammation, on DOMS in human volunteers. I found that rofecoxib, a cyclo-oxygenase-2 inhibitor, did not attenuate DOMS and nor did tramadol, a central-acting analgesic. The neurochemical pathway underlying DOMS therefore appears to be distinct from the pathways which underlie pain and hyperalgesia in other syndromes. Future research should include investigations into the central mechanisms of muscle pain and blocking the action of IL-1) and CINC-1 both peripherally and centrally may prove a beneficial target for the treatment of clinical muscle pain.

Headache is a common complaint in society and is related to personal, biomechanical and socioeconomic circumstances. In current literature trigger-points (TrPs) in the majority of the muscles of the face and neck contributing to tension-type headache (TTH) have been evaluated, except the TrPs of the masseter muscles. The aim of this studyis to determine the association between myofascial (TrPs) in the masseter muscle group and episodic tension-type headache (ETTH). Fourteen subjects with ETTH were matched with same sex and same age subjects not suffering from headache acting as the control group. The diagnostic criteria as described by Simons and Travel (1999) were used in the objective tests to diagnose the TrPs in the masseter muscles. Subjective tests included a disability questionnaire, National stress awareness day stress questionnaire, (NSAD stress questionnaire), a precipitating and aggravating factors questionnaire. Active TrPs were found in 92.86% of ETTH group and 7.14% had latent TrPs. Within the control group 7.14% had active TrPs, 14.29% latent TrPs and 78.37% had no TrPs.Differences in the presence of masseter TrPs between the ETTH and control group were significant with p-value <0.001. All the questions asked in the headache disability questionnaire evaluating headache frequency, intensity and severity were significantwith p-value<0.005. The NSAD stress questionnaire revealed statistical significant values for questions pertaining to muscular aches and pains and subjectively subjects claimed that theyfelt tension at work. The precipitating questionnaire showed that physical activity, stress / tension and reading were significant precipitating factors for developing a tension-type headache. The aggravating questionnaire only showed light as an aggravating factor. Stress and tension had 100% “yes”answers in the ETTH group.Weather as an aggravating factor had 100% “no” answersfrom the control group.Physical activity, driving and noise had relative high percentages of “yes”answers from the ETTH group and higher probability scores for being an aggravating factor whencomparing the ETTH and control group, but were not found to be statistically significant. Myofascial TrPs in the masseter muscle group contribute to the origin and or maintenance of ETTH.

A research report submitted to the Faculty of Health Sciences, University of the Witwatersrand, in partial fulfillment of the requirements for the degree of Master of Science in Medicine in the field of Biokinetics Johannesburg, 2017 / Background: Patellofemoral pain (PFP) is a common knee complaint associated with pain around the patella. Research has identified altered electromyographic (EMG) activity of the knee muscles in individuals with PFP compared to a healthy population (Briani et al., 2016). Purpose: The purpose of this observational study was to identify the EMG activity of the quadriceps muscle during functional activities in participants experiencing PFP and participants with no PFP. Methods: The onset and sequence timing including the ranking and Q-angle in relation to the rectus femoris (RF), vastus medialis obliquus (VMO) and vastus lateralis (VL) activity was measured with surface EMG in 17 PFP participants and 17 controls during a sit to stand, squat, and step up and step down. Results: The RM-ANOVA discovered a significant difference in the onset of VMO compared to RF muscle between the activities in the PFP group (-0.11 to 0.07 sec; p = 0.03) and the healthy group (-0.18 to -0.03; p = <0.01), as well as the VL compared to the RF muscle in the PFP group (-0.07 to 0.13 sec; p = <0.01). Significant differences were shown comparing the ranking of EMG onset for the quadriceps muscle to each activity in the healthy group (p = <0.01 to 0.04), and in the PFP group for the sit to stand (p = 0.01). Onset of VMO activity was predominantly ranked first in the healthy group (56%) and the VL in the PFP group (44%). A Mann-Whitney U-test shown a significant relationship in the healthy group between the Q-angle and the VMO, VL and RF muscles during the step down activity (r = -0.53 to -0.55; p = 0.02 to 0.03). Conclusion: This study confirms that the quadriceps muscle responds differently to different functional activities in the PFP and healthy population respectively. The healthy group tend to utilize the VMO first, compared to the PFP group with altered onset of quadriceps activation. Furthermore, the greater the Q-angle is, the earlier the onset of quadriceps muscle will be in the healthy group. This relationship was not found in the PFP group. / MT2017