Fatigue in Adapted Systems. In: Gandevia SC, Enoka RM, Mccomas AJ, Stuart DG, Thomas CK, Pierce PA, editors. Fatigue. Boston: Springer US; 1995. pp. 429-56. [DOI: 10.1007/978-1-4899-1016-5_34]

The association between metabolic syndrome and pressure ulcers among individuals living with spinal cord injury

OBJECTIVE

The objective of this study was to identify the relationship between metabolic syndrome (MetS) and pressure ulcers (PrU), after controlling for demographic and injury characteristics, socioeconomic factors, health behaviors and fatigue among participants with spinal cord injury (SCI).

METHODS

This cross-sectional study recruited 350 participants with SCI from a hospital in the western region of the USA. Blood tests and physical examination were performed. Waist circumference, high-density cholesterol, triglycerides, blood pressure and fasting glucose were used to diagnose MetS according to Criteria for Clinical Diagnosis of Metabolic Syndrome defined by the American Heart Association. All other variables were self-reported. Three-stage multivariate logistic regression models were conducted to evaluate the effects of three sequential sets of predictors, including demographic/injury, socio-environmental/behavioral and health factors, basing the order of analysis on the Theoretical Risk and Prevention Model.

RESULTS

The prevalence of PrU and MetS was 11.0% (n=36) and 35.3% (n=115), respectively. Ethnicity, smoking, alcohol consumption and MetS were statistically associated with PrU in the full model. Participants who were non-Hispanic (odds ratio (OR)=10.30, 95% confidence interval (CI): 3.46-30.65), smokers (OR=2.69, 95% CI: 1.00-7.27) and drank over 30 drinks per month (OR=5.26, 95% CI: 1.24-22.26) had greater odds of having a PrU compared with those who were Hispanic, non-smokers and non-drinkers, respectively. We also observed a positive association between MetS and PrU (OR_MetS=3.71, 95% CI: 1.45-9.52), even after controlling for all other factors.

CONCLUSION

Participants who had MetS had higher odds of PrU than those without MetS after adjusting for multiple covariates. Unhealthy behaviors such as smoking and excess drinking were positively associated with PrU.

Symptom burden in persons with spinal cord injury

OBJECTIVE

To determine (1) the frequency, severity, and reported course of 7 symptoms in persons with spinal cord injury (SCI) and (2) the association between these symptoms and patient functioning.

DESIGN

Postal survey.

SETTING

Community.

INTERVENTION

A survey that included measures of the frequency, severity, and recalled course of pain, fatigue, numbness, weakness, shortness of breath, vision loss, and memory loss, as well as a measure of community integration and psychologic functioning was mailed to a sample of persons with SCI. One hundred forty-seven usable surveys were returned (response rate, 43% of surveys mailed).

MAIN OUTCOME MEASURES

The frequency and average severity of each symptom was computed, and the frequencies of each type of reported course were noted. Analyses estimated the associations among the symptoms, and between symptom severity and measures of patient functioning.

RESULTS

The most common symptoms were pain, weakness, fatigue, and numbness. All symptoms were reported to remain the same or to get worse more often than they were reported to improve once they began. Pain, weakness, fatigue, and memory loss were the symptoms most closely associated with patient functioning.

CONCLUSIONS

Patients with SCI must deal with a number of secondary complications in addition to any disability caused by the injury itself. Of 7 symptoms studied, pain, weakness, and fatigue appeared to be most common and most closely linked to patient social and mental health functioning. Research is needed to identify the causal relationships between perceived symptoms and quality of life in patients with SCI and to identify effective treatments for those symptoms shown to impact patient functioning.

High intensity exercise increases expression of matrix metalloproteinases in fast skeletal muscle fibres

Metalloproteinases (MMPs) are proteolytic enzymes that function in the extracellular matrix to degrade connective tissues. While it is clear that exercise-induced injury in skeletal muscle promotes increased expression of MMPs, the relationship between exercise intensity and expression of MMPs in muscles is unknown. These experiments tested the hypothesis that exercise-induced expression of matrix metalloproteinases (MMP-2 and MMP-9) is dose-dependent such that high-intensity endurance exercise increases MMP expression whereas low-intensity endurance exercise will not promote MMP expression in skeletal muscles. Female rats (4 months old) completed 2 weeks of treadmill running at either low (18 m min(-1); approximately 50% maximum oxygen consumption rate ) or high intensity (32 m min(-1); approximately 70% ; up to 50 min day(-1)). Non-running, sedentary animals served as controls. Muscle mRNA and protein levels of MMP-2 and MMP-9 were assessed in gastrocnemius, quadriceps and soleus muscles by reverse transcriptase-polymerase chain reaction and Western blotting, respectively. Results indicate that exercise did not alter MMP-9 in any of these skeletal muscles. Further, our data reveal that low-intensity exercise did not alter the expression of MMP-2 in any of the muscles investigated. In contrast, high-intensity exercise increased both mRNA and protein levels of MMP-2 in skeletal muscles containing a high percentage of fast type II fibres (i.e. gastronemius and superficial quadriceps). These results support the hypothesis that high-intensity exercise is required to promote the expression of MMP-2 in skeletal muscles and that the influence of exercise on MMP-2 expression is dominant in muscles containing a high percentage of fast fibres.

Reliability of isolated isometric function measures in rat muscles composed of different fibre types

The present study investigated the absolute reliability (R(Ab)) of isometric measures of time-to-peak tension (TTP), half-rise time ((1/2)RT), half-fall time ((1/2)FT), twitch force (TW(f)) tetanic force (TET(f)) and the sag ratio as applied to the slow soleus (SOL) and the fast-twitch extensor digitorum longus (EDL) and medial gastrocnemius (MG) muscles of the rat hindlimb. In addition, the relationship of each individual isometric measure was examined with regard to the pattern of myosin heavy chain (MHC) isoform expression. Measures of TTP, (1/2)RT, (1/2)FT and sag ratio were negatively correlated with MHCIId(x) and MHCIIb (P < 0.0001), and positively correlated with MHCI (P < 0.0001). TW(f) and TET(f) were negatively correlated with MHCI content (P < 0.0001) and positively with MHCIId(x) (P < 0.0001) and MHCIIb (P < 0.001). Comparisons of isometric measures using a paired Student's t test revealed that they were not different between the right and left legs; all measures displayed high correlations between the left and right legs (r= 0.71-0.85, P < 0.0001). In contrast to standard tests of statistical significance, these functional measures exhibited a considerable range of R(Ab) when individual muscles were studied in only one hindlimb. When averaged across all muscles, however, the (1/2)FT, (1/2)RT, TW(f) and TTP measures possessed high overall reliability; measures of TET(f) and sag ratio were moderately reliable. The results of this study show that the isometric measures studied possess significant predictive value with regard to MHC isoform content; the left and right legs are interchangeable but display a considerable range of reliability when only one hindlimb is studied.

Electrical stimulation: can it increase muscle strength and reverse osteopenia in spinal cord injured individuals?

OBJECTIVE

To study the extent to which atrophy of muscle and progressive weakening of the long bones after spinal cord injury (SCI) can be reversed by functional electrical stimulation (FES) and resistance training.

DESIGN

A within-subject, contralateral limb, and matching design.

SETTING

Research laboratories in university settings.

PARTICIPANTS

Fourteen patients with SCI (C5 to T5) and 14 control subjects volunteered for this study.

INTERVENTIONS

The left quadriceps were stimulated to contract against an isokinetic load (resisted) while the right quadriceps contracted against gravity (unresisted) for 1 hour a day, 5 days a week, for 24 weeks.

MAIN OUTCOME MEASURES

Bone mineral density (BMD) of the distal femur, proximal tibia, and mid-tibia obtained by dual energy x-ray absorptiometry, and torque (strength).

RESULTS

Initially, the BMD of SCI subjects was lower than that of controls. After training, the distal femur and proximal tibia had recovered nearly 30% of the bone lost, compared with the controls. There was no difference in the mid-tibia or between the sides at any level. There was a large strength gain, with the rate of increase being substantially greater on the resisted side.

CONCLUSION

Osteopenia of the distal femur and proximal tibia and the loss of strength of the quadriceps can be partly reversed by regular FES-assisted training.

Exercise-induced slow waves in the EEG of cats

The aim of the present study was to investigate the early signs of fatigue. Cats were chronically implanted with electrodes in the frontal and occipital cortical areas, and a thermocouple was inserted into the nasal orifice to record respiratory rate. After a recovery of 10 days, the animals were trained for running on treadmill. On the day before recording, a catheter was tied into one of the common carotid arteries to record arterial blood pressure. The electroencephalogram (EEG), arterial blood pressure, and respiration were recorded continuously. At the time of deceleration of running high amplitude, slow waves appeared both in the sensorimotor and occipital cortical regions. The power spectra showed a significant increase in frequencies of 1-6 Hz in the sensorimotor cortex, and of 1-10 Hz in the occipital cortex, with a great increase in the total power. During rest the pre-running, brain activity reappeared gradually. The arterial blood pressure, the heart rate, and the respiratory rate were elevated during running, but no special changes occurred at the onset of the slow waves in the EEG. The blood glucose level was somewhat higher after the first 2-min running than the pre-running level. It is concluded that the appearance of slow waves in the EEG is an early manifestation of fatigue. The cardiorespiratory changes and the blood sugar concentrations play no role in the slowing of the electrocorticogram. The present results show the involvement of brain mechanisms in the onset of tiredness.