Categories and frequencies of leisureactivities employed by 156 randomly selected males and females aged 40-44, 50-54, 60-64 were investigated by structured interviews and were related to leisuresatisfaction, to experienced health and socio-economic status. In equal numbers (15) of males and females from each group and in 24 males (60 +_6 years) with intermittent claudication (Cl) isokinetic plantar flexion performance was investigated with registrations of peak torque (PT), contractional work (CW), active range-of-motion (RoM) and integrated electromyograms from all threee triceps surae heads. Subjects performed a few maximum plantarflexions at different velocities of angular motion and also up to 200 consecutive plantar flexions at 60 °/s. The males aged 40-44 were re -investigated after two years additionally using electromyographic power frequency analyses. Leisure choice was mainly age and sex independent and extensively included outdoor activities. Leisure satisfaction was positively associated with relative frequency of activities. Symptoms of bodily discomfort, in particular backpain, were quite common and apparently caused relatively low level of mutual leisure activities. Thus, with in this age span, leisure activities appear rather rigid but often successfully, adhered to . Common ailments influence partnership mutuality negatively. Plantar flexion PT and CW are adequately p re dicta ble by sex, age and crural circumference. Uniformly a 3:2 male/female ratio characterizes mechanical output and iEMG. The latter is velocity independent. Output decreases with increasing age. Hence the output/excitation balance (CW/iEMG) is age, but not sex, dependent. CI-patients produce less PT and CW than do controls. Independently of this disease, of age and sex, PT and CW describe parallel negative exponential functions of velocity. During repeated manoeuvres plantar flexion output and iEMG initially drop, there after to maintain nearly steady-state levels. Throughout up to 200 contractions CW/iEMG was unaltered in the clinically healthy. Test/re-test with two years interval yielded nearly identical results. Leftshifts in mean power frequency in parallel with output-drop imply that the latter probably is due to FT-motor unit fatigue. For CW, but not for PT, the drop became slower and the (relative) steady-state level higher with increasing age, indicating significant increase in endurance with age. In the Cl-patients, output, but not excitation, decreased after a few repititions. Therefore, CW/iEMG fell dramatically, implying intramuscular fatigue. Taken together with findings of close associations between total cumulated work and measured/expected maximum walking tole rance it is suggested that measurements of CW and calculations of CW/iEMG are of clinical value. / <p>Härtill 5 uppsatser</p> / digitaliserinlg@umu.se

Yes / The mechanical output at the ankle provides key contribution to everyday activities, particularly step/stair ascent and descent. Age-related decline in ankle functioning can lead to an increased risk of falls on steps and stairs. The rising up-on-the-toes (UTT) 30-second test (UTT-30) is used in the clinical assessment of ankle muscle strength/function and endurance; the main outcome being how many repetitive UTT movements are completed. This preliminary study describes how inertial measurement units (IMUs) can be used to assess the UTT-30. Twenty adults (26.2 ± 7.7 years) performed a UTT-30 at a comfortable speed, with IMUs attached to the dorsal aspect of each foot. Use of IMUs’ angular velocity signal to detect the peak plantarflexion angular velocity (p-fAngVelpeak) associated with each repeated UTT movement indicated the number of UTT movements attempted by each participant. Any UTT movements that were performed with a p-fAngVelpeak 2SD below the mean were deemed to have not been completed over a sufficiently ‘full’ range. Findings highlight that use of IMUs can provide valid assessment of the UTT 30-second test. Their use detected the same number of attempted UTT movements as that observed by a researcher (average difference, -0.1 CI, -0.2 – 0.1), and on average 97.6 ± 3.1% of these movements were deemed to have been completed ‘fully’. We discuss the limitations of our approach for identifying the movements not completed fully, and how assessing the consistency in the magnitude of the repeated p-fAngVelpeak could be undertaken and what this would indicate about UTT-30 performance.

High-tone extensor thrust is common to those with cerebral palsy and those suffering spinal cord injuries. It is a muscle-control phenomenon that causes the body to straighten spastically. One goal of this thesis is to design a dynamic seating system that moves with respect to the wheelchair frame, allowing the seat to move with the user during an extensor thrust and reduce forces. One unique challenge is that the seat needs to remain rigid during normal functional activities and only become dynamic when an involuntary thrust is detected. A second goal of this thesis is to design a control scheme that is able to differentiate between these two types of motion. These design goals are initially investigated with a hinged-seatback system, instrumented with sensors to allow for the detection of thrusts and to actively control seating components. A full seating system is then built to allow for full-body extensor thrusts, involving the seatback, seat bottom, and leg rest of the wheelchair. This system is analyzed for effectiveness of reducing forces on the body during an extensor thrust. Another serious problem for this segment of the population is pressure ulcers. These are caused by prolonged pressure on the skin from weight-bearing bony prominences. Various seating system configurations are known to help with pressure relief. The three standard configurations for a chair are tilt, recline, and standing. The final goal of this thesis is to measure and compare the effectiveness of these three methods for their ability to relieve pressure on the seat bottom. To accomplish this, a powered wheelchair with built-in capabilities for recline and standing is mounted to a tilting mechanism. Test subjects are used to experimentally compare the effectiveness of each method for pressure reduction using pressure mats on all weight-bearing surfaces. A 2D model is also developed and validated with the experimental results.

The series of experiments comprising this thesis investigate how neural inputs arising from higher motor centres (e.g., the motor cortex) and the periphery are translated into a variety of activation patterns of alpha motoneurones during the performance of various muscle contraction types. The thesis consists of six chapters, with the first chapter providing an introduction to the research program, and the final chapter giving a summary of the main research findings. Chapter 2 to 5 each represent stand-alone scientific works. The study presented in Chapter 2 examined whether the soleus (SOL) H-reflex is modulated during shortening contractions in a manner that has been observed for isometric contractions. It was revealed that no significant correlation was found between the SOL H-reflex and increasing plantar flexion torque during shortening contractions (ρ = −0.07, P = 0.15), while a strong positive correlation was observed for the isometric conditions (ρ = 0.99, P < 0.01). Furthermore, no modulation in the H-reflexes via paired stimuli in voluntary shortening contractions suggested that the level of homosynaptic post-activation depression (HPAD) did not change in response to the varying levels of activation in voluntary shortening contractions. Therefore, Ia-excitatory input is likely to be reduced during shortening contractions at increasing intensities, possibly due to a centrally regulated increase in presynaptic inhibition. The study described in Chapter 3 investigated corticospinal-evoked responses in triceps surae muscles during voluntary contractions at varying strengths. Motor-evoked potentials (MEPs) and cervicomedullary motor-evoked potentials (CMEPs) were elicited in the SOL and medial gastrocnemius (MG) muscles using magnetic stimulation over the motor cortex and cervicomedullary junction during voluntary plantar flexions with the torque ranging from 0 to 100% of a maximal voluntary contraction (MVC). In both SOL and MG, MEP and CMEP amplitudes [normalized to maximal M wave (Mmax)] showed an increase, followed by a plateau, over the greater part of the contraction range with responses increasing from 0.2 to 6% of Mmax for SOL and from 0.3 to 10% of Mmax for MG. It was suggested that increases in the evoked responses from the triceps surae muscle over a greater range of contraction strengths than for upper limb muscles, probably stems from differences in the pattern of motor unit recruitment and rate coding for these muscles, and the strength of the corticospinal input. In Chapter 4, in an attempt to investigate how the recruitment and rate coding of motor unit organisation can affect the responsiveness of gross evoked potentials to artificial excitatory stimuli, a computer simulation was performed based upon a physiologically plausible model of the motoneurone. The simulation revealed that the force level where the evoked response commences to decline corresponds approximately to the upper limit of recruitment of motor units. This observation was consistent no matter whether firing rates for low-threshold units exceed those for high-threshold units. Since the simulated results were consistent with previous observations in both individual (single motor unit) and population (motoneurone pool) terms, the proposed model is physiologically plausible and can be useful to predict the evoked EMG response via artificial stimulation protocols, thereby inferring the underlying neural mechanisms occurring at the motoneurone pool during voluntary movements. The study presented in Chapter 5 determined the recruitment range and discharge behaviours in the SOL motor units, and examined the possible influence of persistent inward currents (PICs) on SOL motor unit recruitment and discharge rates. Forty-two clearly identified motor units from five subjects revealed that soleus motor units are recruited progressively from rest to contraction strengths close to 95% of MVC, with low-threshold motor units discharging action potentials slower at their recruitment and with a lower peak rate than later recruited high-threshold units. This observation is in contrast to the ‘onion skin phenomenon’ often reported for the upper limb muscles. Based on positive correlations of the peak discharge rates, initial rates and recruitment order of the units with the magnitude of the onset-offset hysteresis (i.e., a difference in discharge rate between recruitment and de-recruitment) and not PIC contribution, we conclude that discharge behaviours among motor units appear to be related to a variation in an intrinsic property other than PICs.

Introduction: Impaired isometric muscle strength and muscle endurance in adults with Fontan circulation has previously been reported. However, the knowledge if corresponding impairment is present in children and adolescents with Fontan circulation is scarce. Aim: The aim was to examine the isometric muscle strength and muscle endurance of the lower limbs in children and adolescents with Fontan circulation in comparison to age and sex matched controls. Method: In this cross-sectional study 43 children and adolescents (6-18 years) with Fontan circulation and 43 controls were included. Isometric knee extension and plantar flexion muscle strength was assessed using dynamometry (Newton:N). Unilateral isotonic heel-lift until exhaustion was used for evaluation of lower limb muscle endurance. Analysis on group level (n=43) and for the subgroups 6-12 years (n=18) and 13-18 years (n=25) was performed. Results: On group level the children and adolescents with Fontan circulation had impaired isometric plantar flexion strength for the left leg compared to controls (393.9±181.1N vs. 492.5±241.6N, p=0.04). In addition, they had impaired isometric knee extension strength bilaterally (right 222.8±101.1N vs. 293.0±164.9N, p=0.02, left 220.7±102.7N vs. 279.5±159.1N, p=0.05). In contrast, lower limb muscle endurance did not differ. In subgroup analysis, the impaired isometric strength was only present in the group of adolescents. Conclusion: Adolescents with Fontan circulation had impaired isometric muscle strength compared to controls. However, no corresponding differences were found in children. Further, lower limb muscle endurance did not differ. This implies that the impaired isometric muscle strength may develop during adolescence whereas the impaired muscle endurance may occur later. / Del av en multicenterstudie

This research investigates various applications of diffuse correlation spectroscopy (DCS) on in-vivo human muscle tissue, both at rest and during dynamic exercise. Previously suspected muscle tissue relative blood flow (rBF) baseline shift during extended measurement with DCS and DCS-Near infrared spectroscopy (NIRS) hybrid optical systems are verified, quantified, and resolved by redesign of optical probe and alteration in optical probe attachment methodology during 40 minute supine bed rest baseline measurements. We then translate previously developed occlusion techniques, whereby rBF and relative oxygen consumption rV̇O2 are calibrated to initial resting absolute values by use of a venous occlusion (VO) and arterial occlusion (AO) protocol, respectively, to the lower leg (gastrocnemius) and these blood flows are cross validated at rest by strain gauge venous plethysmography (SGVP). Methods used to continuously observe 0.5Hz, 30% maximum voluntary isometric contraction (MVIC) plantar flexion exercise via dynamometer are adapted for our hybrid DCS-Imagent diffuse optical flow-oximeter in the medial gastrocnemius. We obtain healthy control muscle tissue hemodynamic profiles for key parameters BF, V̇O2, oxygen saturation (StO2), deoxyhemoglobin, oxyhemoglobin, and total hemoglobin concentrations ([Hb], [HbO2], and THC respectively), as well as systemic mean arterial pressure (MAP) and pulse rate (PR), at rest, during VO/AO, during dynamic exercise and during 15 minute recovery periods. Next, we began investigation of muscle tissue hemodynamic disease states by performing a feasibility pilot study using limited numbers of controls and peripheral arterial disease (PAD) patients using the translated methods/techniques to determine the ability of our technology to assess differences in these populations.

The first two chapters are devoted to general issues relating to the Achilles tendon and brings important insights that are required for subsequent practical part. To the practical part is also devoted the following chapter. The first chapter is more of a medical nature. It explains the function and location of the Achilles tendon. Above all, the nature of the examination. Then follow chapters dealing with the assembly of functional devices for sensing the Achilles tendon reflex. This section begins in the third chapter discusses the preparation and block diagrams for the sensor and its technical solutions. The following chapter is about constructing electrical circuits, calculation of component values for the device of Achilles tendon reflex. The fifth chapter deals with the ability to view the scanned signal and the final chapter is devoted to measurements of the device on a group of volunteers.