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Query: UMLS:C0015672 (fatigue)
 51,768 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Percutaneous intramuscular electrodes and a portable multichannel system were used to restore the function of the paralyzed lower extremities in six patients with complete paraplegia. The total number of inserted electrodes was 168. All of the patients could stand, two could walk in parallel bars, and two could walk with a walker. The rate of breakage of electrodes was only 0.6% in our series. There were 10 (6.0%) superficial infections, and 10 (6.0%) movement of electrodes which required reimplantation. The results suggest that the ultrafine intramuscular electrode is practical for long term use with paraplegic patients. Although the system can be used for paraplegic patients during the activities of daily living, it will be necessary to develop a closed-loop controller to reduce the amount of stimulation to the extensor muscles and extend the endurance of upright activity to reduce fatigue.
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PMID:Clinical experience of functional electrical stimulation in complete paraplegia. 889 29

A minimal set of muscles (8 to 16) were identified as candidates for implantation in a clinical system to provide walking function to individuals with complete paraplegia using functional electrical stimulation (FES). Three subjects with complete motor and sensory paraplegia had percutaneous intramuscular electrodes implanted in all major muscles controlling the trunk, hips, knees, and ankles. Stimulation patterns for walking with FES were generated for different sets of eight and 16 muscles. The quality and repeatability of the resulting gait produced by walking patterns consisting of various combinations of muscles were determined. Most eight-channel stimulation patterns resulted in scissoring or insufficient hip flexion, preventing forward progression. One eight-channel system allowed a maximum speed of 0.1 m/s with a cadence of 22 steps/min and a stride length less than 0.3 m. Improved walking performance was observed with 16 channels of stimulation. This ranged from slow step- to gait at 0.1 m/s to smooth reciprocal gait at 0.5 m/s. In all three subjects, the favored combination of 16 channels included erector spinae for trunk extension; gluteus maximus, posterior portion of adductor magnus and hamstrings for hip extension; tensor fasciae latae and either sartorius or iliopsoas for hip flexion; vastus lateralis/intermedius for knee extension; and tibialis anterior/peroneous longus for ankle dorsiflexion. In one subject the 16-channel FES system provided repeatable day-to-day gait averaging 0.4 m/s, 58 steps/min and a stride length at 0.8 m. A maximum repeatable walking distance with 16 channels was 34 m. Multiple 34-m trials were possible with minimal rests between walks. Fatigue of both the hip extensors and upper body was a limiting factor. The selection of target muscles for implantation is critical to the performance of FES systems. This study provides guidelines to muscle selection for walking with FES based on objective measures of gait performance. The findings indicate that a 16-channel FES system for total implantation is feasible for repeatable short distance, independent, walker-support walking in paraplegia.
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PMID:Muscle selection and walking performance of multichannel FES systems for ambulation in paraplegia. 908 82

A new concept of device, termed the weight-bearing control (WBC) orthosis, has been designed with three major needs in mind; a rigid frame that supports the user's body weight, a special hip joint device that reciprocally propels each leg forward, a gas powered foot device that varies the sole thickness of the device for foot/floor clearance, and control system of the orthosis. A paraplegic (T7 level complete paraplegia, sensory evoked potential silent, response to electro-stimulation on the cortical area of the brain also silent) who has tested this WBC orthosis has been able to walk without fatigue at a high speed for a greater distance than before. In walking tests of this WBC orthosis, he achieved a maximum walking speed of 34.1 m/min for a distance of 10 metres. The walking distance reached 521 m with an average walking speed of 21.2 m/min without rest on one small tank of CO2 liquid gas, measuring 10 cm in length and 3 cm in diameter.
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PMID:A new concept of dynamic orthosis for paraplegia: the weight bearing control (WBC) orthosis. 945 97

The systolic (SP) and diastolic (DP) blood pressure and heart rate (HR) responses during a fatiguing isometric contraction of either the handgrip or quadriceps muscles was measured in 139 paraplegic patients divided into five groups (having injuries at T4, T12 and L1-L3 and suffering complete paraplegia and having injuries at T4 but showing incomplete hemiplegia or paraplegia) and 25 controls. While all handgrip exercise was maintained by voluntary effort, only the controls were able to make a voluntary contraction of their quadriceps muscles; the paraplegics had isometric contractions of their quadriceps muscles elicited by functional electrical stimulation (FES). The endurance of the handgrip exercise was not significantly different among the controls and any one of the five experimental groups (control group endurance = 151 s, average paraplegic group endurance = 141 s) while it was higher in the leg muscles (P < 0.05 controls 133 s, paraplegics 111 s). All subjects showed a linear increase in SP and DP throughout the duration of the handgrip exercise, pressure increasing from rest to fatigue by 55-56 mmHg. The controls, subjects with a complete and incomplete spinal cord injuries at T4 showed similar SP and DP increases during leg exercise, both the SP and DP response was eliminated in the T12 and L1-L3 injury groups. The HR increased during fatiguing isometric handgrip contractions from an average resting value of 82 to a maximum of 121 beats x min(-1) in both the controls and paraplegic subjects. However, while the HR increased to a slightly higher level of 127 beats x min(-1) at the end of the contraction of the leg muscles in the controls, the increase in HR during FES exercise was modest, increasing by an average of only 6 beats x min(-1) in the paraplegic group.
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PMID:Blood pressure and heart rate response to isometric exercise: the effect of spinal cord injury in humans. 1171 79

Complete spinal cord injury (SCI) is characterized, in part, by reduced fatigue-resistance of the paralyzed skeletal muscle during stimulated contractions, but the underlying mechanisms are not fully understood. The effects of complete SCI on skeletal muscle Na(+),K(+)-adenosine triphosphatase (ATPase) concentration, and fiber type distribution were therefore investigated. Six individuals (aged 32.0 +/- 5.3 years) with complete paraplegia (T4-T10; 1-19 years since injury) participated. There was a significantly lower Na(+),K(+)-ATPase concentration in the paralyzed vastus lateralis (VL) when compared to either the subjects' own unaffected deltoid or literature values (from our laboratory, utilizing the same methodology) of VL Na(+),K(+)-ATPase concentration for the healthy able-bodied (141.6 +/- 50.0, 213.4 +/- 23.9, 339 +/- 16 pmol/g wet wt., respectively; P < 0.05). There was also a significant negative correlation between the Na(+),K(+)-ATPase concentration in the paralyzed VL and years since injury (r = -0.75, P < 0.05). These findings are clinically relevant as they suggest that reductions in Na(+),K(+)-ATPase contribute to the fatigability of paralyzed muscle after SCI. Unexpectedly, the VL muscles of our subjects had a higher proportion of their area represented by type I fibers compared to literature values for the VL of the healthy able-bodied (52.6 +/- 25.3% vs. 36 +/- 11.3%, respectively; P < 0.05). As all our subjects had upper motor neuron injuries and, therefore, experienced muscle spasticity, our findings warrant further investigation into the relationship between muscle spasticity and fiber type expression after SCI.
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PMID:Na+,K+-ATPase concentration and fiber type distribution after spinal cord injury. 1469 96

Standing by means of functional electrical stimulation (FES) after spinal cord injury is a topic widely reported in the neurorehabilitation literature. This practice commonly uses surface stimulation over the quadriceps muscle to evoke knee extension. To date, most FES neuroprostheses still operate without any artificial feedback, meaning that after a fatigue-driven knee buckle event, the stimulation amplitude or pulse width must be increased manually via button presses to re-establish knee-lock. This is often referred to as 'hand-controlled (HC) operation'. In an attempt to provide a safer, yet clinically practical approach, this study proposed two novel strategies to automate the control of knee extension based on the kinematic feedback of four miniaturised motion sensors. These strategies were compared to the traditional HC strategy on four individuals with complete paraplegia. The standing times observed over multiple trials were in general longer for the automated strategies when compared to HC (0.5-80%). With the automated strategies, three of the subjects tended to need less upper body support over a frame to maintain balance. A stability analysis based on centre of pressure (CoP) measurements also favoured the automated strategies. This analysis also revealed that although FES standing with the assistance of a frame was likely to be safe for the subjects, their stability was still inferior to that of able-bodied individuals. Overall, the unpredictability of knee buckle events could be more effectively controlled by automated FES strategies to re-establish knee-lock when compared to the traditional user-controlled approach, thus demonstrating the safety and clinical efficacy of an automated approach.
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PMID:Efficacy and stability performance of traditional versus motion sensor-assisted strategies for FES standing. 1934 49