Anterior cruciate ligament injury leads to increased sagittal tibial translation, and perceptions of instability and low confidence in the knee joint are common. Many patients have remaining problems despite treatment and are forced to lower their activity level and prematurely end their career in sports. The effect of ACL reconstruction and/or rehabilitation on dynamic knee stability is not completely understood. The overall aim of this thesis was to study the dynamic knee stability during and after rehabilitation in individuals with ACL injury. More specific aims were 1) to elaborate an evaluation method for muscle strength, 2) to evaluate the effect of exercises in closed and open kinetic chain, and 3) to evaluate dynamic knee stability in patients with ACL deficiency or ACL reconstruction. Sagittal tibial translation and knee flexion angle were measured using the CA‐4000 computerised goniometer linkage. Muscle activation was registered with electromyography. The intra‐ and inter‐rater reliability of 1 repetition maximum (RM) of seated knee extension was clinically acceptable. The inter‐rater reliability of 1RM of squat was also acceptable, but the intra‐rater reliability was lower. The systematic procedure for the establishment of 1RM that was developed can be recommended for use in the clinic. One specific exercise session including cycling and a maximum number of knee extensions and heel raises did not influence static or dynamic sagittal tibial translation in uninjured individuals. A comprehensive rehabilitation program with isolated quadriceps training in OKC led to significantly greater isokinetic quadriceps strength compared to CKC rehabilitation in patients with ACL deficiency. Hamstring strength, static and dynamic translation, and functional outcome were similar between groups. Five weeks after ACL reconstruction, seated knee extension produced more anterior tibial translation compared to the straight leg raise and standing on one leg. All exercises produced less or equal amount of anterior tibial translation as the 90N Lachman test. Five weeks after the ACL reconstruction the static and dynamic tibial translation in the ACL reconstructed knee did not differ from the tibial translation on the uninjured leg. Patients in the early phase after ACL injury or ACL reconstruction used a joint stiffening strategy including a reduced peak knee extension angle during gait and increased hamstring activation during activity, which reduces the dynamic tibial translation. Patients with ACL deficiency that completed a four months rehabilitation program used a movement pattern that was more close to normal.

Muscular fatigue limits athletic performance as well as activities of daily living that require repetitive or sustained contractile activity. The decrease in force output or inability to maintain a given force level during fatigue occurs as the result of neural and muscle physiological factors. In contrast to muscle fatigue, potentiation is an increase in muscle force following voluntary muscle activity. The simultaneously occurring processes of potentiation and fatigue influence force output. The aims of this research were to investigate parameters used to potentiate muscle via electrical stimulation and voluntary contraction, and to better understand how muscle force is sustained, we studied single motor unit firing patterns and force potentiation following muscular endurance training. In study 1, electrical stimulation trains matched for pulse number of various frequencies and of increasing pulse number at a given frequency were administered to determine the effects of these stimulation parameters and of the force-time integral (FTI) produced during the train on potentiation magnitude. No difference in potentiation magnitude was found across trains of matched pulse number for frequencies of 15, 25, 30 and 50 Hz. Potentiation increased as pulse number increased and there was a positive correlation between potentiation and the FTI. In study 2, we measured maximal potentiation following conditioning contractions (CC) of 25%, 50% and 100% maximal voluntary contraction (MVC) and during a 25% MVC fatigue task, pre-post 8 weeks of muscular endurance training. Results showed significant potentiation for all CC intensities. Potentiation increased as CC intensity increased and CC duration required to achieve maximal potentiation decreased as CC intensity increased. Muscular endurance training resulted in increased maximal potentiation, and potentiation was greater during the fatigue task after training. Potentiation was also correlated to endurance time. In study 3, the effects of muscular endurance training on motor unit firing rates were investigated. There was a small increase in mean motor unit firing rates during the course of the fatigue task after training. This research contributes to our understanding of muscular force production and muscular endurance. The findings suggest that motor unit firing frequency and force potentiation may contribute to enhanced muscular endurance. / text

Elements of an individuals occupational exposure, such as their posture can affect their comfort during work, and also their long term musculoskeletal health. Knowledge as to the extent of the influence of particular aspects of the exposures can help in providing guidance on risk evaluation, and direct future technical design focus. In many situations the exposures interact, and even if the effects of individual exposures are understood, the interactions are often less so. This is certainly the case with off-road driving exposures. Specific investigations have focussed on the effects of vibration exposure, resulting in the development of international standards and guidelines on measurement and evaluation of exposure. Consideration of the posture of the operator can be accomplished through postural assessment tools, although none of the currently available methods are developed specifically for use within a vehicle environment. The issues of both the posture of the operator and the seated vibration exposure are particularly apparent in off-road agricultural driving environments, where the driving task dictates that operator is often required to maintain specific postures whilst also exposed to whole-body vibration. In agriculture, many of the tasks require the operator to maintain axially rotated postures to complete the task effectively. The analysis of the combined effects of the axial rotation of the operator and the whole-body vibration exposure has been limited to a few studies within the literature, and is currently poorly understood. The overall aim of the thesis was to assess the influence of axial rotation and whole-body vibration on the musculoskeletal discomfort of the neck and trunk, in order that the true extent of the exposure risk may be evaluated. A field study was conducted to determine the common characteristics of some typical exposures, to provide a basis for the laboratory studies. A survey of expert opinion was conducted, examining the knowledge and experience of experts in assessing the relative influence of axial rotation and whole-body vibration on operators musculoskeletal health. The main investigations of the thesis are focussed in the laboratory, where the objective and subjective effects of axial rotation (static and dynamic) and whole-body vibration were investigated. Objective measures included the investigation of muscular fatigue in response to exposures. The tasks investigated in the field study indicated that the exposures often exceed the EU Physical Agents Exposure Limit Value, and that the axial rotation is a large component of the postures required. The survey of expert opinion concluded that combined exposure to axial rotation and whole-body vibration would increase the risks of lower back pain, and that acknowledgement of combined exposures should be included when assessing for risk. The results of the laboratory studies indicated that the greatest discomfort was present when subjects were exposed to axial rotation in the neck and shoulders. Out of the 8 muscles investigated, at most 6 of the 8 indicated fatigue during an experimental exposure. The muscle group which was affected most by the exposures was the m. trapezius pars decendens. Findings demonstrated that when subjects were exposed to axial rotation and whole-body vibration they indicated discomfort and their muscles fatigued. However, there was poor correlation between the sites of discomfort and the location of muscular fatigue. The discomfort findings suggest that there is an increased risk of discomfort from experiencing axial rotation together with whole-body vibration. Investigations of muscular fatigue do not substantiate this finding.

Abstract Background. The pre-exhaustion (PE) method is a way to target a stronger muscle in a multi-joint exercise by isolating the stronger muscle immediately before the multi-joint exercise. It has been shown that this principle give greater magnitude of muscular activation in the synergistic secondary mover. There is also some indications that the PE method gives a greater neuromuscular activation of the primary mover when PE the synergist. If there are any differences between men and women in muscle activity has never been investigated before. Men have a greater absolute strength than women, especially in their upper body. There are still conflicting results if they also have greater relative strength. Aim. The purpose of the present study was to investigate if there were any neuromuscular differences between men and women when PE triceps brachii before bench press and if there was any differences in relative strength during 10RM bench press. Methods. 15 men and 15 women was randomly signed up in two different protocols. Protocol 1 started with bench press at 10 repetition maximum (10RM) and after five minutes of recovery, they performed the pre-exhaustion exercise (triceps extensions to failure) immediately before a second round of bench press with the same load on the barbell. Protocol 2 started with triceps extensions to failure immediately before bench press at their 10RM. They also had five minutes of recovery before they performed 10 repetitions of bench press. The magnitude of muscular activation were collected with surface electromyography and then processed through average root mean square (RMS). The values were normalized to muscular voluntary isometric contraction (MVIC) and expressed as percent of MVIC. The muscles that was analysed was triceps brachii (TB), pectoralis major (PM) and deltoideus anterior (DA). Results. The results showed that women had a statistically significantly higher muscular activity in all three muscles; PM (p=0.001) TB (p=0.023) and DA (p=0.047) after pre-exhaustion of TB before bench press compared to only bench press. Men showed only a statistical significant higher activation in PM (p=0.003) and a trend of higher activation in DA (p=0.061). There was a statistically significant difference in muscle activity between women and men in TB (p=0.015) but not in DA (p=0.902) and PM (p=0.436). There was no statistically significant difference between relative strength (volume load/fat free mass) (p=0.775) nor number of repetitions in bench press after PE of TB (p=0.713) between the sexes. Conclusion. The main findings in this study is that it was a statistically significant difference in neuromuscular activity in TB between men and women when PE was applied to TB before the bench press compared to bench press only, but no difference in relative strength.

Submitted in partial compliance with the requirements for the Master’s Degree in Technology: Chiropractic, Durban University of Technology, Durban, South Africa, 2016. / Purpose: Ankle sprains are amongst the most common injury sustained by athletes and the general public. When an ankle is repeatedly sprained it results in chronic ankle instability syndrome (CAIS). This repeated trauma results in disruption of the afferent nerve supply from the injured joint, which affects the motor neuron pool excitability of the peroneal and soleus muscles resulting in arthogenic muscle inhibition (AMI). Traditional treatment for CAIS focuses on rehabilitation of the affected muscles via strength and proprioceptive training. Recent literature has shown that the addition of ankle joint manipulation resulted in improved clinical outcomes in the treatment of CAIS. The mechanism on how joint manipulation affects AMI is under-investigated especially in extremity joints. Thus this study aimed to determine the immediate effect of ankle joint manipulation on peroneal and soleus muscle activity, by assessing surface electromyography (sEMG) H/M ratio to detect a change in the proportion of the total motor neuron pool being recruited, in participants with CAIS. Methods: The study utilised a quantitative, experimental, pre-test post-test study design. Forty two participants with grade I and II CAIS, aged 18-45 years, were randomly allocated into one of three groups. Group one received a single talocrural joint long axis distraction manipulation, group two received a sham manipulation and group three was the control receiving no intervention. sEMG H/M ratio measurements were taken before and immediately after the intervention using a Biopac wireless emg system. Results: The groups were comparable at baseline for age, gender, body mass index and H/M ratio measurements for the soleus and peroneal muscles (p < 0.050). Intra-group analysis of the soleus muscle H/M ratio showed no statistically significant change over time for the manipulation (p = 0.975) and sham (p = 0.056) groups, with the control group showing a statistically significant (p = 0.019) decrease in the H/M ratio. For the peroneal muscle no statistically significant (p > 0.050) differences were observed in any of the three groups. Inter-group analysis of the soleus muscle H/M ratio measurements showed no statistically significant differences between the three groups (p = 0.470; F = 1.010) over time, with Tukey’s HSD post-hoc test revealing a statistically significant (p = 0.028) difference being observed between the sham and control groups in terms of post soleus muscle H/M ratio measurements. Conclusion: This study failed to show that ankle joint manipulation affects the soleus and peroneal muscles in terms of H/M ratio measurements in participants with CAIS. There may have been a trend of an effect of the sham and manipulation interventions counteracting the muscle fatigue experienced in the control group, however further investigation is required. / M

Objectives: We evaluate the movement patterns of left-sided radicular syndrome patients on the basis of intervertebral disc herniation L4/L5 or L5/S1 and test group to verify expected verge asymmetry between selected muscles and changes in their timing. Participants: 10 patients with left-sided radicular syndrome caused by intervertebral disc herniation were objects of the reserarch L4/L5 or L5/S1 (7 men, 3 women, average age 37,4 ± 10,67 years old). 6 healthy individuals without vertebrogenic problems were part of the reserarch (2 men, 4 women, average age 27,4 ± 2,6 years old) Methods: During specific tests focused on stabilizing function of musculosceletal system, selected muscles activity was recorded for both groups by SEMG Data analysis: The variation significance between experimental and test group was evaluated by two-tailed t-test. Significance level of p=0.05 was selected for statistical hypothesis testing. Results: We have proved statistically significant asymmetry between right and left side for patients with radicular syndrom. Significant variations were found for muscles timing between group with herniation and test group. Conclusion: Selected muscles activity and involvement sequence changes (timing) were found for patients with intervertebral disc herniation during postural tests,...

Title: Effects of PNF to change the motoric stereotype of the abduction in the shoulder joint Objectives: The aim of this thesis, which is conceived as a pilot experimental study is to verify the changes in the timing of selected muscles during stereotype abduction of the shoulder after performing repetitive cyclic motion by therapeutic method PNF if a specific number of repetitions of the movement is performed. Methods: This is a pilot experimental study, which was done on seven probands, 4 men and 3 women with an average age of 26.6 years. The surface EMG muscle activity was scanned on selected muscles during the motoric testing of stereotype of the abduction of the shoulder joint before and after the PNF techniques. The EMG signal was then analyzed and we evaluated the timing of muscles before and after the PNF techniques. The results were then compared in terms of both intra-individually and inter-individually comparison. Results: Results provided contradictory answers to the fundamental questions relating to changes in the timing of selected muscles after PNF techniques. In terms of the change in intra-individually timing after PNF hypothesis was proved. But from the perspective of inter-individually comparison the hypothesis was not proved. Keywords: PNF, surface electromyography, motion...

Title: PNF technique after arthroscopic stabilization of the shoulder joint Objectives: The objective of this work is to consider the possibility of use of the proprioceptive neuromuscular facilitation technique (PNF) in early stages of rehabilitation after arthroscopic stabilization of the shoulder joint. The idea is to use the phenomen of irradiation with which this concept works. Methods: The pilot experimental group consisted of 7 healthy participants with simulated arthroscopic stabilization of the left shoulder joint. The electromyography was used to record the electric activity of musculus trapezius pars descendens, pars transversa et pars ascendens, musculus deltoideus pars acromialis, musculus infraspinatus and musculus pectoralis major pars sternocostalis on the immobilized left arm; while using the PNF technique on the peripheral parts of the immobilised arm; and on the contra lateral arm. A 5s sequence of stabilised isometric contraction was analysed and all data further normalised to Maximal Voluntary Contraction (MVC). Considering the literature the 20% increase above the MVC was defined as substantial to assure sufficient functional capacity of the muscle fibres and therefore sufficient to stop muscle atrophy during immobilisation of the arm. Results: Results of this study support...

Title: The comparative analysis of forward stroke on the slalom kayak, wildwater kayak and speed kayak The Aim: Aim of this work is the comparative analysis of forward stroke on the kayak to slalom kayak, wildwater kayak and speed kayak. Methods: For comparison, we used electromyography measurements, we have synchronized with video. Results: The results of this work we show that most differences in the forward stroke, according to timing of entries we selected muscle activation between the speed and slalom kayak. Keywords: Electromyography, forward stroke, slalom, wildwater, speed canoeing

Title: Discrimination of EMG signals from individual forearm muscles from surface EMG Abstract: Location of electrodes for sensing the forearm muscles using surface electromyography is not accurately described. It is based only on recommendations by various authors in making researches. The aim of this study was to determine the optimal placement of electrodes on the forearm and describe it to another repeatable measurements. By analyzing the amplitude of EMG recording is confirmed not only the optimal location of electrodes, but either suggested muscle synergies that are possible to analyze more deeply in other studies because a detailed examination of muscle synergies are considerable application in upper limb prosthetics Keywords: Surface electromyography, forearm muscles, amplitude analysis