Twelve weeks of exercise training increases muscle function and walking capacity in elderly predialysis patients and healthy subjects.

Muscle function declines with age and progressive uraemia. We examined whether elderly predialysis patients could improve thigh muscle function, walking capacity, and functional mobility to the same extent as elderly healthy subjects when participating in 12 weeks of individual muscle endurance exercises for the thigh as well as in a low-intensive group programme. The uraemic exercise and comparison groups comprised 16 patients (age 76 +/- 7 years, glomerular filtration rate 18 +/- 5 ml/min) and 9 patients (age 72 +/- 6 years, glomerular filtration rate 16 +/- 5 ml/min), respectively. The healthy exercise and comparison groups comprised 18 subjects (age 75 +/- 7 years) and 5 subjects (age 79 +/- 4 years), respectively. Muscular strength, dynamic endurance, walking capacity, and functional mobility increased significantly in both the uraemic and the healthy exercise groups after 12 weeks of regular muscle endurance exercise training, whereas there was no significant change in static muscle endurance and quality of life in either group. None of the values changed for the uraemic comparison group nor the healthy comparison group during the observation period. Elderly predialysis patients had lower muscle function and mobility as compared with elderly healthy subjects, but were able to improve both after 12 weeks of exercise training to the same extent as elderly healthy subjects.

Effects of continuous stretching on cell proliferation and collagen synthesis in human burn scars.

Hypertrophic and contracted scars are common complications of deep and partial thickness burns, and the usual way to prevent them is to stretch the burn are actively as well as passively. However, little has been written about the effects of stretching on burn scar tissue at a cellular and molecular level. The stretching usually results in an increased area of skin, and a central question is whether this is caused by stimulation of cell proliferation or decreased cell density, which could lead to impaired quality of the skin. In the present study a new in vitro model was developed and used to study the effects of stretching on the proliferative activity as well as on the synthesis of collagen in human burn scars. Proliferation was measured quantitatively by thymidine incorporation and spatially by immunohistochemistry. The net proliferation in the burn scar was decreased after one day, and significantly decreased after six days of continuous stretching (p = 0.02). However, immunohistochemistry showed increased proliferation in the basal layer of the epidermis while the proliferative activity in the dermal cells was inhibited. Collagen synthesis was decreased after six days of stretching whereas no effect was shown after one day. These findings indicate that static stretching of a human burn scar results in inhibition of proliferation in dermal cells leading to a low cell density in the dermis which, combined with increased collagen synthesis, could lead to reduced biomechanical strength.

Inter-rater reliability of the 1992 international standards for neurological and functional classification of incomplete spinal cord injury.

AIMS: To determine the inter-rater reliability in scoring sensory and motor function and in defining sensory and motor levels in incomplete spinal cord injury, using the revised 1992 International Standards for Neurological and Functional Classification of Spinal Cord Injury (ISCSCI-92) and to determine the effect on raters agreement of one standardising assessment. METHODS: Two physicians and two physiotherapists at the Spinal Cord Injury Unit, Karolinska Hospital, classified 23 patients according to the ISCSCI-92. Kappa values were calculated. RESULTS: Kappa values varied from 0 to 0.83 (poor to very good) for the pin-prick scores, from 0 to 1 for the light touch scores and from 0 to 0.89 for motor function after the standardising assessment. Kappa values for sensory and motor levels were fair to poor after the standardising assessment. The results showed improvement in degree of agreement in 35/46 dermatomes for scoring pin-prick, in 15/42 for light touch, in 14/19 segments for motor function and for three out of four sensory and motor levels. CONCLUSION: This study indicates a weak inter-rater reliability for scoring incomplete SCI lesions using the ISCSCI-92.

Effects of high resistance training in patients with myotonic dystrophy.

Nine ambulatory subjects with myotonic dystrophy participated in a supervised 12-week progressive high-resistance training program. Knee extensor muscles were trained 3 times a week with free weights, 3 x 10 repetitions at 80% of 1RM. One leg was randomly chosen for training and the other served as control. Six patients completed the training program. In the trained leg, 1RM increased from 16.4 +/- 3.4 kg to 21.8 +/- 2.6 kg (p = 0.0002). There was no difference between pre- and post-training concentric or eccentric isokinetic values at 30 degrees/second in either leg. Muscle biopsy from m. vastus lateralis in the trained leg revealed no systematic difference in the degree of histopathological abnormalities before and after training. After training, there was a tendency toward increase in cross-sectional area of type I muscle fibres. However, the number of subjects was too small to draw conclusions regarding the effects of training on the histopathological changes. Magnetic resonance imaging revealed no difference in the m. quadriceps area after training. In conclusion, patients with myotonic dystrophy improved their muscle strength without any observed negative side effects after a 12-week high-resistance training program.

Magnetic resonance imaging of lower extremity muscles and isokinetic strength in foot dorsiflexors in patients with prior polio.

The thigh and lower leg of six patients with prior polio were examined using magnetic resonance imaging (MRI), and the strength of their weak foot dorsiflexors was measured isokinetically. Spinecho images of the lower extremities were visually evaluated on a semi-quantitative four-point scale, and T1 and T2 relaxation times of the lower leg anterior compartment were analysed. There were prominent MRI signs of randomly distributed muscle degeneration. The high signal intensity changes in the affected muscles on T1-weighted images and T1 and T2 values indicated replacement of muscle fibres with fat and the accumulation of tissue water, respectively. MRI findings were compared with isokinetic strength in foot dorsiflexor muscles. Foot dorsiflexor peak torque values at 30 deg/s ranged from 6 to 29 Nm. There was no significant correlation between MRI visual scoring, T1 and T2 relaxation times and peak torque values at 30 deg/s. However, the most severe MRI changes with visual scoring and T2 relaxation times were observed in the patients with the most pronounced muscle weakness.

Fatigue of chronically overused motor units in prior polio patients.

This study was undertaken to investigate the mechanisms underlying fatigue of chronically overused motor units (MUs). The force of the tibialis anterior muscle (TA) and the firing properties of single MUs were studied during prolonged maximum voluntary effort in 10 prior polio patients selected such that daily living required all residual TA power. Almost all TA fibers were hypertrophic type I. Activities of intermyofibrillar succinate dehydrogenase (SDH) and calcium-stimulated myofibrillar adenosine triphosphatase (ATPase) were measured in single TA fibers from a representative patient. Neither insufficient motoneuron activation nor peripheral blocking of the electrical impulse played a major role in the loss of force during prolonged contraction or for slow recovery after contraction. The ratio of SDH to calcium-stimulated ATPase, representing the relation between energy resynthesis and energy utilization, was significantly (P < 0.001) lower in prior polio patients (0.230 +/- 0.096) compared to control (0.515 +/- 0.097) type I fibers.

Contractile properties in single muscle fibres from chronically overused motor units in relation to motoneuron firing properties in prior polio patients.

The relation between motoneuron firing rate in vivo and maximum velocity of unloaded shortening (Vmax) and myosin isoform composition in single chemically skinned muscle fibres was investigated in chronically overused motor units. Ten patients with loss of a large proportion of the motoneuron pool due to a prior polio lesion and compensatory overuse of residual neurones were studied and compared with normal individuals. The tibialis anterior muscle (TA) was chosen and prior polio patients who used all residual TA motor units at high rates during the normal step cycle were selected. In prior polio patients, all motor units fired at approximately 40 Hz when maximum voluntary force was reached. A common firing rate of 30 Hz yielded 70-90% maximum force. In normal subjects, on the other hand, maximum TA force was reached when low threshold units fired at 25-30 Hz and high threshold units at 50 Hz. Myosin heavy chain (MHC) and light chain (MLC) isoforms were resolved by 6% and 12% sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE), respectively, and quantified densitometrically. In the whole biopsy cross-sections, types I, IIA and IIB MHC proportions were 97, 3 and 0% in a typical prior polio patient and 65, 25 and 10% in an age- and sex-matched control subject. Vmax differed significantly (p < 0.001) between type I fibres from the patient (0.54 +/- 0.12 ML/s) and the control subject (0.29 +/- 0.08 ML/s). The composition and relative contents of essential and regulatory MLC isoforms differed in single type I MHC fibres from the control subject and prior polio patient. 65% of the fibres co-expressed the fast and slow isoform of the regulatory light chain (MLC2) in the patient, while this combination was only observed in one of the control type I fibres. All prior polio fibres with a Vmax higher than 0.45 ML/s, except one, co-expressed MLC2s and MLC2f and the only control fibre co-expressing the slow and fast MLC2 isoform had the highest Vmax (0.50 ML/s) among control fibres. On the other hand, a high relative content of MLC3 was not associated with a high Vmax in type I MHC fibres. It is suggested that the composition of fast and slow isoforms of MLC2 has a significant modulatory influence on Vmax within type I MHC fibres. This combination of MLCs and high Vmax in type I MHC fibres is probably induced by chronic motor unit overuse and an altered motoneuron firing pattern.

Efficacy of botulinum toxin for cervical dystonia. A comparison of methods for evaluation.

Twenty patients with cervical dystonia were treated during one year with repeated intramuscular injections of botulinum toxin. The outcome was evaluated comparing subjective global rating with relative changes in degree of pain on the Visual analogue scale (VAS), degree of dysfunction due to dystonia, and quality of life according to the Nottingham health profile (NHP). Objective measurement of dystonic position and movement ability was performed using a goniometer, semiquantitatively noted as scores according to Fahn and Tsui. Before treatment, the degree of impaired life quality on the NHP did not correlate with the Tsui score of dystonic posture, but significantly with the Fahn score (p < 0.01) which also includes data on pain. Significant improvement after treatment was seen for all parameters (p < 0.05). Global subjective rating correlated significantly with improved posture according to the Tsui score (p < 0.05), but not with reduced pain or degree of dysfunction. The results suggest that the efficacy of botulinum toxin in cervical dystonia is best evaluated using a combination of the VAS for pain and the Tsui score for dystonic posture and movement ability.

Electromyographic single motor unit potentials after repeated botulinum toxin treatments in cervical dystonia.

Electromyographic (EMG) single motor unit potentials (MUPs) of the sternomastoid muscles (STM) were made before and after repeated treatment with botulinum type A toxin (Bx) for cervical dystonia. Post-treatment examinations were 6-25 weeks after the latest injection, when symptoms and EMG interference pattern had recurred and signs of denervation were scarce. Concentric needle EMG records of 200 motor unit potentials in 10 patients showed reduced durations and areas after treatment (P < 0.05). Increased polyphasia or satellite potentials were not observed. Macro-EMG records of 110 MUPs in 6 patients showed reduced amplitudes and areas in the injected STM when compared to the untreated side (P < 0.05). Fibre density was within the same range (1.0-1.2). The results indicate that the pattern of the terminal innervation is mainly restored even after repeated Bx treatments, but the number or size of active muscle fibres within the motor unit is reduced. The clinical relapse could be due to recovery of the original nerve terminals, or to nerve sprouts closely imitating the blocked terminal nerve twigs or both.

Isokinetic strength, macro EMG and muscle biopsy of paretic foot dorsiflexors in chronic neurogenic paresis.

Ten ambulatory patients with chronic dorsiflexor paresis due to prior poliomyelitis or lumbar root (LV) lesion and without recent decline of the foot dorsiflexor strength were examined with isokinetic strength measurement, macro EMG and muscle biopsy. Isokinetic strength measurement showed peak torques at 30 degrees/s angular velocity ranging 6-44 Nm and at 240 degrees/s 1-10 Nm. Mean of individual median macro EMG motor unit potential amplitudes was 2020 microV (SD 1040) which was 5-10 times higher than expected values in healthy subjects. Muscle biopsies showed a mean type 1 fibre proportion of 91% (SD 14) and a mean type 1 fibre area of 8561 microns 2 (SD 2773) which was about 2 times larger than those observed in healthy subjects. Peak torque and both motor unit potential amplitude and area were inversely correlated at 30 (p < 0.01 and p < 0.025), 60 (p < 0.025 and p < 0.025) and 120 (p < 0.05 and p < 0.05) degrees/s angular velocity, as were peak torque and type 1 muscle fibre proportion at 30 (p < 0.05) and 60 (p < 0.05) degrees/s angular velocity. Peak torque or macro EMG parameters were not correlated to muscle fibre area. The data suggest that the remaining muscle strength was directly correlated to the degree of collateral sprouting and that about half of it could be attributed to compensatory muscle fibre hypertrophy.

Torque-velocity relation and muscle fibre characteristics of foot dorsiflexors after long-term overuse of residual muscle fibres due to prior polio or L5 root lesion.

Isokinetic foot dorsiflexion strength and muscle biopsy data from eight patients with overuse of tibialis anterior muscle (TA) fibres due to weakness after prior polio or L5 root lesion were compared to data from age and sex matched, healthy subjects. Concentric peak torque at an angular velocity of 30 degrees/s was 6-24 Nm in the patients and 15-34 Nm in the controls (p < 0.01). Muscle biopsies from TA showed a significantly higher proportion of type 1 fibres in the patients as compared to the controls (p < 0.005). The type 1 fibres in the patients had a significantly larger cross-sectional area than in the controls (p < 0.005). The type 1 fibre proportion and relative area were inversely correlated to the relative concentric torque produced at 180 degrees/s (p < 0.05) and 240 degrees/s (p < 0.05) compared to that produced at 30 degrees/s in the controls but not in the patients. However, the relative concentric torque produced at 180 degrees/s and 240 degrees/s compared to that produced at 30 degrees/s was not significantly different in the patients and the controls. This indicates that the contractile properties of the overused muscle fibres do not change in parallel with the histochemical fibre type.