Free plasma catecholamines in spinal cord injured persons with different injury levels at rest and during exercise

Differential behavioral and neurochemical effects of exercise, reboxetine and citalopram with the forced swim test

AIMS

In this study, we investigated whether short-term exercise, known to promote hippocampal brain-derived neurotrophic factor (BDNF) expression, would also enhance activity in the Porsolt forced swim test (FST), a model for assessing antidepressant efficacy. We also wished to determine whether exercise combined with antidepressants would be more effective at modifying behavior in the FST than either intervention alone. In parallel with this, we also expected that these interventions would preserve post-stress levels of BDNF, and that antidepressants designed to selectively enhance noradrenergic or serotonergic neurotransmission (reboxetine or citalopram, respectively) would have differential effects on behavior and BDNF expression.

MAIN METHODS

Male Sprague-Dawley rats were treated with exercise (voluntary wheel running), reboxetine, citalopram, or the combination of exercise and each antidepressant, for 1 week. At the end of this period, a subset of animals from each treatment group underwent the FST. Post-stress levels of hippocampal BDNF mRNA were then quantified via in situ hybridization.

KEY FINDINGS

Our results indicate that while both exercise and antidepressant treatment preserved post-stress levels of hippocampal BDNF mRNA, each intervention led to a unique behavioral profile in the FST. We found that antidepressant treatment increased swimming time in the FST, but that exercise decreased swimming time. While the combination of reboxetine-plus-exercise led to an increase in climbing and diving, citalopram-plus-exercise reduced these behaviors.

SIGNIFICANCE

It is possible that active behaviors during the FST, though specific to antidepressant medications, may not reflect increased hippocampal BDNF expression or other survival- associated benefits.

Pulmonary function and spinal cord injury

Injury to the cervical and upper thoracic spinal cord disrupts function of inspiratory and expiratory muscles, as reflected by reduction in spirometric and lung volume parameters and static mouth pressures. In association, subjects with tetraplegia have decreased chest wall and lung compliance, increased abdominal wall compliance, and rib cage stiffness with paradoxical chest wall movements, all of which contribute to an increase in the work of breathing. Expiratory muscle function is more compromised than inspiratory muscle function among subjects with tetraplegia and high paraplegia, which can result in ineffective cough and propensity to mucus retention and atelectasis. Subjects with tetraplegia also demonstrate heightened vagal activity with reduction in baseline airway caliber, findings attributed to loss of sympathetic innervation to the lungs. Significant increase in airway caliber following inhalation of ipratropium bromide, an anticholinergic agent, suggests that reduction in airway caliber is not due to acquired airway fibrosis stemming from repeated infections or to abnormal hysteresis secondary to chronic inability of subjects to inhale to predicted total lung capacity. Reduced baseline airway caliber possibly explains why subjects with tetraplegia exhibit airway hyperresponsiveness to methacholine and ultrasonically nebulized distilled water. While it has been well demonstrated that bilateral phrenic nerve pacing or stimulation through intramuscular diaphragmatic electrodes improves inspiratory muscle function, it remains unclear if inspiratory muscle training improves pulmonary function. Recent findings suggest that expiratory muscle training, electrical stimulation of expiratory muscles and administration of a long-acting beta(2)-agonist (salmeterol) improve physiological parameters and cough. It is unknown if baseline bronchoconstriction in tetraplegia contributes to respiratory symptoms, of if the chronic administration of a bronchodilator reduces the work of breathing and/or improves respiratory symptoms. Less is known regarding the benefits of treatment of obstructive sleep apnea, despite evidence indicating that the prevalence of this condition in persons with tetraplegia is far greater than that encountered in able-bodied individuals.

Immunity and cognition: what do age-related dementia, HIV-dementia and 'chemo-brain' have in common?

Until recently, dogma dictated that the immune system and the central nervous system (CNS) live mostly separate, parallel lives, and any interactions between the two were assumed to be limited to extreme cases of pathological insult. It was only a decade ago that T cells in the injured brain were shown to play a protective rather than a destructive role. In this article, we explore the role of the immune system in the healthy brain, focusing on the key function that T lymphocytes have in the regulation of cognition. We discuss candidate mechanisms underlying T cell-mediated control of cognitive function in human cognitive diseases associated with immune decline, such as age- and HIV-related dementias, 'chemo-brain' and others.

Lipid profiles of persons with paraplegia and tetraplegia: sex differences

BACKGROUND/OBJECTIVE

To examine the lipoprotein profiles of men and women with paraplegia and tetraplegia. Impairment of the sympathetic nervous system (dependent on the level of injury) and the extent of physical capacity and activity were correlated with the lipid profile in men with spinal cord injury (SCI). Sex-related differences of the lipoprotein profiles could be found in nondisabled and premenopausal women with SCI mainly because of the different effects of sexual hormones.

METHODS

Lipoprotein profiles of 112 participants with SCI (32 premenopausal women, 80 men) were analyzed and correlated to sex, lesion level, and physical performance capacity.

RESULTS

Women with tetraplegia or paraplegia showed significantly higher levels of high-density lipoprotein and lower ratios of total cholesterol to high-density lipoprotein-cholesterol compared with men with corresponding lesion levels, without a difference in peak oxygen consumption. Concentrations of very-low-density lipoproteins were lower in women with paraplegia than in men with paraplegia; no differences were found in total cholesterol, low-density lipoprotein-cholesterol, and triglycerides. Sex-independent elevations in total cholesterol and low-density lipoprotein-cholesterol were associated with paraplegia, and sex-independent elevations in triglyceride levels were associated with tetraplegia.

CONCLUSIONS

Persons with SCI showed sex-related differences in their lipoprotein profiles. Independent of physical fitness, the lipoprotein profile of premenopausal women with SCI did not exhibit the adverse lipoprotein characteristics observed in men with SCI, probably because of the influence of sexual hormones independent of lesion level.

Autonomic Nervous System Dysfunction After Spinal Cord Injury

The autonomic nervous system (ANS) plays a key role in the regulation of many physiologic processes, mediated by supraspinal control from centers in the central nervous system. The role of autonomic dysfunction in persons with spinal cord injuries is crucial to understand because many aspects of the altered physiology seen in these individuals are directly caused by ANS dysregulation.

Mechanisms of blood pressure and heart rate variability: an insight from low-level paraplegia

It is still unclear whether the low-frequency oscillation in heart rate is generated by an endogenous neural oscillator or by a baroreflex resonance. Our aim was to investigate this issue by analyzing blood pressure and heart rate variability and the baroreflex function in paraplegic subjects with spinal cord injury below the fourth thoracic vertebra. These subjects were selected because they represent a model of intact central neural drive to the heart, with a partially impaired autonomic control of the vessels. In our study, arterial blood pressure and ECG were recorded in 33 able-bodied controls and in 33 subjects with spinal cord lesions between the fifth thoracic and the fourth lumbar vertebra 1) during supine rest (lowest sympathetic activation), 2) sitting on a wheelchair (light sympathetic activation), and 3) during exercise (moderate sympathetic activation). Blood pressure and heart rate spectra, coherence, and baroreflex function (sequence technique) were estimated in each condition. Compared with controls, paraplegic subjects showed a reduction of the low-frequency power of blood pressure and heart rate, and, unlike controls, a 0.1-Hz peak did not appear in their spectra. Sympathetic activation increased the 0.1-Hz peak of blood pressure and heart rate and the coherence at 0.1 Hz in controls only. Paraplegic subjects also had significantly lower baroreflex effectiveness and greater blood pressure variability. In conclusion, the disappearance of the 10-s oscillation of heart rate and blood pressure in subjects with spinal cord lesion supports the hypothesis of the baroreflex nature of this phenomenon.

Mechanisms of osteoporosis in spinal cord injury

Osteoporosis is a known complication of spinal cord injury (SCI), but its mechanism remains unknown. The pathogenesis of osteoporosis after SCI is generally considered disuse. However, although unloading is an important factor in the pathogenesis of osteoporosis after SCI, neural lesion and hormonal changes also seem to be involved in this process. Innervation and neuropeptides play an important role in normal bone remodelling. SCI results in denervation of the sublesional bones and the neural lesion itself may play a pivotal role in the development of osteoporosis after SCI. Although upper limbs are normally loaded and innervated, bone loss also occurs in the upper extremities in patients with paraplegia, indicating that hormonal changes may be associated with osteoporosis after SCI. SCI-mediated hormonal changes may contribute to osteoporosis after SCI by different mechanisms: (1) increased renal elimination and reduced intestinal absorption of calcium leading to a negative calcium balance; (2) vitamin D deficiency plays a role in the pathogenesis of SCI-induced osteoporosis; (3) SCI antagonizes gonadal function and inhibits the osteoanabolic action of sex steroids; (4) hyperleptinaemia after SCI may contribute to the development of osteoporosis; (5) pituitary suppression of TSH may be another contributory factor to bone loss after SCI; and (6) bone loss after SCI may be caused directly, at least in part, by insulin resistance and IGFs. Thus, oversupply of osteoclasts relative to the requirement for bone resorption and/or undersupply of osteoblasts relative to the requirement for cavity repair results in bone loss after SCI. Mechanisms for the osteoporosis following SCI include a range of systems, and osteoporosis after SCI should not be simply considered as disuse osteoporosis. Unloading, neural lesion and hormonal changes after SCI result in severe bone loss. The aim of this review is to improve understanding with regard to the mechanisms of osteoporosis after SCI. The understanding of the pathogenesis of osteoporosis after SCI can help in the consideration of new treatment strategies. Because bone resorption after SCI is very high, intravenous bisphosphonates and denosumab should be considered for the treatment of osteoporosis after SCI.

Performance diagnostics in handbiking during competition

STUDY DESIGN

Case study in handbiking under competition conditions.

OBJECTIVE

To investigate exercise-induced, metabolic, pulmonary, cardiovascular and energetic reactions of a paraplegic athlete during a city marathon.

SETTING

City marathon Cologne, Germany.

SUBJECT

We tested a 27-year-old male athlete from the German national team. The handicap of the athlete was a complete traumatic spinal cord injury ASIA/IMSOP Grade A at the level of the fourth thoratic vertebra (Th4).

METHOD

In the competition, the athlete used his own race handbike whose crank system had been exchanged for a power measurement system with registering option. For measuring ventilatory gas parameters during exercise, a portable spirometric system was used. The athlete managed to finish the marathon race in 1:48:54 h.

RESULTS

The mean oxygen uptake (VO2) during the marathon was 1580 ml/min, with a maximum value of 2535 ml/min. The mean heart frequency was 137 bpm with a maximum of 157 bpm. During the race the mean energy consumption was 463 kcal/h with a maximum of 758 kcal/h. Prior to the race, the blood lactate value was 2.9 mmol/l; after 10 km 4.4 mmol/l; after 20 km 2.9 mmol/l, and after 30 km 2.9 mmol/l.

CONCLUSION

Competition-oriented handbikers should concentrate on exercise units of long duration at low intensities--like marathon runners or cyclists--in order to improve their aerobic performance capacity. However, it has to be pointed out that paraplegic athletes develop relatively high metabolic intensities in competition and that the variability of their physiological parameters is considerably high.

Exercise as a Health-Promoting Activity Following Spinal Cord Injury

Spinal cord injury is a catastrophic event that immeasurably alters activity and health. Depending on the level and severity of injury, functional and homeostatic decline of many body systems can be anticipated in a large segment of the paralyzed population. The level of physical inactivity and deconditioning imposed by SCI profoundly contrasts the preinjury state in which most individuals are relatively young and physically active. Involvement in sports, recreation, and therapeutic exercise is commonly restricted after SCI by loss of voluntary motor control, as well as autonomic dysfunction, altered fuel homeostasis, inefficient temperature regulation, and early-onset muscle fatigue. Participation in exercise activities also may require special adaptive equipment and, in some instances, the use of electrical current either with or without computerized control. Notwithstanding these limitations, considerable evidence supports the belief that recreational and therapeutic exercise improves the physical and emotional well-being of participants with SCI. This article will examine multisystem decline and the need for exercise after SCI. It will further examine how exercise might be used as a tool to enhance health by slowing multisystem medical complications unique to those with SCI. As imprudent exercise recommendations may pose avoidable risks of incipient disability, orthopedic deterioration, or pain, the special risks of exercise misuse in those with SCI will be discussed.

Expression of cardiovascular and behavioural components of conditioned fear to context in T4 spinally transected rats

A spinal cord transection at the fourth thoracic level (T4) results in paraplegia. It also removes supraspinal control of sympathetic outflow to most viscera and their blood vessels but spares the heart. We studied the effects of such a transection on the expression of the conditioned fear response to context, which includes freezing, 22 kHz ultrasonic vocalisations, a marked pressor response and a slowly rising tachycardia. Rats implanted with radiotelemetric probes were fear conditioned, tested, then transected at T4 and finally re-tested 4 weeks after transection. Baseline blood pressure in transected animals was the same as in intact animals but baseline heart rate was 127 bpm higher. There were clear signs of fear in the transected animals: although freezing occurred in the upper part of the body only, there was a 3 fold increase in the number of ultrasonic vocalisations, most probably due to paralysis of abdominal muscles that made expirations shorter and therefore more frequent. The pressor response of fear was initially the same as in intact animals but controls revealed that this was due to handling during transfer to the aversive context. The rest of the pressor response was markedly reduced (70%) confirming that it depends in large part on a sympathetically mediated increase in vascular resistance in the lower part of the body. The cardiac response was characterized by an initial bradycardia followed by a marked tachycardia, which is consistent with a baroreceptor-mediated reflex response to the altered pressor changes. Finally, none of these changes was observed when the same experiment was repeated in sham transected animals. Thus, the pressor response of fear is in large part mediated by the thoracic cord below T4 and the baroreflex is not inhibited but maintained during conditioned fear.

Respostas cardio-respiratórias em pacientes com traumatismo raquimedular

O objetivo desta pesquisa foi investigar as variáveis cardio-respiratórias (Pa, FC, VO2, VCO2 e Ve) durante a Estimulação Elétrica Neuromuscular (EENM) do quadríceps em portadores de lesão medular. Participaram da pesquisa dez pacientes (cinco paraplégicos e cinco tetraplégicos). O protocolo do teste consistiu em 10 minutos de repouso, 20 minutos de EENM dos quadriceps e 10 minutos de recuperação. Durante a EENM foram constatados baixos valores de VO2 e VCO2. Os paraplégicos apresentaram rápida cinética dos gases e os tetraplégicos lenta cinética dos gases. Houve o aumento da Pa sistólica e da FC. Ainda, os valores das variáveis cardio-respiratórias foram inversamente relatadas para o nível de lesão, ou seja, quanto maior o nível de lesão, menor os valores. Portanto, a maioria dos pacientes apresentaram algumas limitações nas respostas cardio-respiratórias, indicando realização de exercício exaustivo, mas apresentaram capacidade de realização de exercício induzido artificialmente, possivelmente devido aos benefícios da EENM.

Energy expenditure in chronic spinal cord injury

PURPOSE OF REVIEW

Obesity is a common secondary complication of chronic spinal cord injury and is associated with adverse metabolic sequelae. Because positive energy balance is the fundamental cause of obesity, we herein review the current knowledge pertaining to total daily energy expenditure, including resting metabolic rate, the thermic effect of food, and physical activity, in the spinal cord injury population.

RECENT FINDINGS

Commonly used equations to predict resting metabolic rate overestimate measured requirements in chronic spinal cord injury by 5-32%. Measured resting metabolic rate is 14-27% lower in persons with spinal cord injury versus those without, due to decreased fat-free mass and sympathetic nervous system activity in this population. However, preliminary evidence suggests that neither the metabolic activity of the fat-free body, nor the obligatory phase of the thermic effect of food is different between those with and without injury. Physical activity levels, especially in those with tetraplegia and complete lesions, are lower than recommended or lower than those of able-bodied persons.

SUMMARY

New equations to predict resting metabolic rate should be validated and prospectively tested in a large sample of men and women with complete and incomplete paraplegia and tetraplegia. Whether the facultative phase of the thermic effect of food is different between those with and without SCI remains to be elucidated. Persons with chronic spinal cord injury, and perhaps those with tetraplegia and complete lesions especially, should be encouraged to engage in increased frequency, intensity and/or duration of physical activity. Future research efforts should explore the effects of level and completeness of neurological lesion on resting metabolic rate, thermic effect of food, and physical activity.

Exercise Recommendations for Individuals with Spinal Cord Injury

Persons with spinal cord injury (SCI) exhibit deficits in volitional motor control and sensation that limit not only the performance of daily tasks but also the overall activity level of these persons. This population has been characterised as extremely sedentary with an increased incidence of secondary complications including diabetes mellitus, hypertension and atherogenic lipid profiles. As the daily lifestyle of the average person with SCI is without adequate stress for conditioning purposes, structured exercise activities must be added to the regular schedule if the individual is to reduce the likelihood of secondary complications and/or to enhance their physical capacity. The acute exercise responses and the capacity for exercise conditioning are directly related to the level and completeness of the spinal lesion. Appropriate exercise testing and training of persons with SCI should be based on the individual's exercise capacity as determined by accurate assessment of the spinal lesion. The standard means of classification of SCI is by application of the International Standards for Classification of Spinal Cord Injury, written by the Neurological Standards Committee of the American Spinal Injury Association. Individuals with complete spinal injuries at or above the fourth thoracic level generally exhibit dramatically diminished cardiac acceleration with maximal heart rates less than 130 beats/min. The work capacity of these persons will be limited by reductions in cardiac output and circulation to the exercising musculature. Persons with complete spinal lesions below the T(10) level will generally display injuries to the lower motor neurons within the lower extremities and, therefore, will not retain the capacity for neuromuscular activation by means of electrical stimulation. Persons with paraplegia also exhibit reduced exercise capacity and increased heart rate responses (compared with the non-disabled), which have been associated with circulatory limitations within the paralysed tissues. The recommendations for endurance and strength training in persons with SCI do not vary dramatically from the advice offered to the general population. Systems of functional electrical stimulation activate muscular contractions within the paralysed muscles of some persons with SCI. Coordinated patterns of stimulation allows purposeful exercise movements including recumbent cycling, rowing and upright ambulation. Exercise activity in persons with SCI is not without risks, with increased risks related to systemic dysfunction following the spinal injury. These individuals may exhibit an autonomic dysreflexia, significantly reduced bone density below the spinal lesion, joint contractures and/or thermal dysregulation. Persons with SCI can benefit greatly by participation in exercise activities, but those benefits can be enhanced and the relative risks may be reduced with accurate classification of the spinal injury.

Time Course of Arterial Vascular Adaptations to Inactivity and Paralyses in Humans

PURPOSE

The aim of the present study was to assess the time course of vascular adaptations to inactivity and paralyses in humans. The spinal cord-injured (SCI) population offers a unique "human model of nature" to assess peripheral vascular adaptations and its time course to extreme inactivity and paralyses.

METHODS

Arterial diameters and red blood cell velocity of the carotid artery (CA), common femoral artery (FA), and brachial artery (BA) were measured using echo Doppler ultrasound. Fifteen SCI persons with lesions varying from 6 wk to 13 months postinjury participated in a cross-sectional study (SCI-CS), 6 SCI individuals were included for longitudinal measurements (SCI-L) at weeks 6, 8, 12, 16, 20, and 24 after the trauma, and 16 able-bodied individuals served as a control group (C).

RESULTS

Within 6 wk after the SCI, diameter (SCI-CS: 0.68 +/- 0.09 cm, SCI-L: 0.67 +/- 0.04 cm, C: 0.95 +/- 0.07 cm) and blood flow (SCI-CS: 299 +/- 112 mL x min(-1), SCI-L 279: +/- 52 mL x min(-1), C: 405 +/- 97 mL x min(-1)) of the femoral artery were significantly reduced (P < 0.001), and local femoral wall shear rate was almost doubled in SCI-CS and SC-L compared with C (P < 0.001). No further changes in femoral arterial properties were observed between week 6 and 13 months postinjury in SCI-L as well as SCI-CS. Carotid and brachial artery diameter and flow were similar in SCI and C and did not change between 6 wk and 13 months after the injury.

CONCLUSION

We conclude that the process of vascular adaptations to inactivity and paralyses in humans seems to be largely completed within weeks.

Leptin response to short-term fasting in sympathectomized men: role of the SNS

We studied plasma leptin levels in six people with high-lesion spinal cord injury [SCI; body mass index (BMI) 25.9 +/- 1.5 kg/m(2), age 37 +/- 3.0 yr] and six able-bodied (AB) controls (BMI 29.1 +/- 1.9 kg/m(2), age 35 +/- 3.5 yr) before and after 12, 24, and 36 h of fasting. The plasma leptin levels significantly decreased during 36 h fasting by 48.8 +/- 4.5% (pre: 11.3 +/- 2.3, post: 6.2 +/- 1.5 ng/ml) and 38.6 +/- 7.9% (pre: 7.6 +/- 5.0, post: 4.2 +/- 1.0 ng/ml) in SCI and AB, respectively. Plasma leptin started to decrease at 24 h of fasting in the SCI group, whereas plasma leptin started to decrease at 12 h of fasting in the AB group. The current study demonstrated that plasma leptin decreased with fasting in both SCI and AB groups, with the leptin decrease being delayed in the SCI group. The delayed leptin response to fasting in the SCI group may be because of increased fat mass (%body fat, SCI: 33.8 +/- 3.0, AB: 24.1 +/- 2.9) and sympathetic nervous system dysfunction.

Changes in cerebral oxygenation and blood flow during LBNP in spinal cord-injured individuals

Spinal cord-injured (SCI) individuals, having a sympathetic nervous system lesion, experience hypotension during sitting and standing. Surprisingly, they experience few syncopal events. This suggests adaptations in cerebrovascular regulation. Therefore, changes in systemic circulation, cerebral blood flow, and oxygenation in eight SCI individuals were compared with eight able-bodied (AB) individuals. Systemic circulation was manipulated by lower body negative pressure at several levels down to -60 mmHg. At each level, we measured steady-state blood pressure, changes in cerebral blood velocity with transcranial Doppler, and cerebral oxygenation using near-infrared spectroscopy. We found that mean arterial pressure decreased significantly in SCI but not in AB individuals, in accordance with the sympathetic impairment in the SCI group. Cerebral blood flow velocity decreased during orthostatic stress in both groups, but this decrease was significantly greater in SCI individuals. Cerebral oxygenation decreased in both groups, with a tendency to a greater decrease in SCI individuals. Thus present data do not support an advantageous mechanism during orthostatic stress in the cerebrovascular regulation of SCI individuals.

Effects of an exercise program on the rehabilitation of patients with spinal cord injury

OBJECTIVES

To evaluate the impact of directed physical exercise in patients with spinal cord injury (SCI) and to measure functional independence before and after an exercise program.

DESIGN

Case series.

SETTING

Tertiary care center.

PARTICIPANTS

Thirteen volunteers with thoracic SCI.

INTERVENTION

Patients participated in a 16-week exercise program, consisting of 3 weekly 120-minute sessions. They performed mobility, strength, coordination, aerobic resistance, and relaxation activities.

MAIN OUTCOME MEASURES

The FIM instrument, arm crank exercise test, wheelchair skills, maximum strength, anthropometry (body composition measurements), and lipid levels. The results were processed by using nonparametric statistical tests.

RESULTS

After comparing the values at the beginning and end of the program, patients showed a significant increase in the following parameters: average FIM score (p < .001) 113 +/- 7.1; weight lifted in the bench press exercise (46%, p < .0001), military press (14%, p < .0002), and butterfly press exercise (23%, p < .0001), and number of repetitions for biceps (10%, p <.0001), triceps (18%, p < .0001), shoulder abductors (61%, p < .0001), abdominals (33%, p <.009), and curl back neck exercise (19%, p < .0001). The maximum resistance achieved during the arm crank exercise test increased (p < .001), and heart rate 6 minutes after the exercise test decreased (p <.05). The time required for the wheelchair skill tests significantly decreased in all the tasks. No statistically significant changes occurred in body weight (p < .154), percentage of body fat (p < .156), lean body weight (p < .158), cholesterol/high-density lipoprotein cholesterol ratio (p < .076), or maximum heart rate (p < .20). The only complication arose in a patient who developed transient sinus bradycardia and hypotension after the arm crank exercise test.

CONCLUSION

The directed exercise program had a positive impact for most of the variables of the study.

Role of the sympathoadrenergic system in adipose tissue metabolism during exercise in humans

1. The relative roles of sympathetic nerve activity and circulating catecholamines for adipose tissue lipolysis during exercise are not known. 2. Seven paraplegic spinal cord injured (SCI, injury level T3-T5) and seven healthy control subjects were studied by microdialysis and (133)xenon washout in clavicular (Cl) and in umbilical (Um) (sympathetically decentralized in SCI) subcutaneous adipose tissue during 1 h of arm cycling exercise at approximately 60 % of the peak rate of oxygen uptake. 3. During exercise, adipose tissue blood flow (ATBF) and interstitial glycerol, lactate and noradrenaline concentrations increased significantly in both groups. Plasma catecholamine levels increased significantly less with exercise in SCI than in healthy subjects. The exercise-induced increase in interstitial glycerol concentration in subcutaneous adipose tissue was significantly lower in SCI compared with healthy subjects (SCI: 25 +/- 12 % (Cl), 36 +/- 20 % (Um); healthy: 60 +/- 17 % (Cl), 147 +/- 45 % (Um)) and the increase in ATBF was significantly lower (Cl) or similar (Um) in SCI compared with healthy subjects (SCI: 1.2 +/- 0.3 ml (100 g)(-1) min(-1) (Cl), 1.0 +/- 0.3 ml (100 g)(-1) min(-1) (Um); healthy: 2.8 +/- 0.7 ml (100 g)(-1) min(-1) (Cl), 0.6 +/- 0.3 ml (100 g)(-1) min(-1) (Um)). Accordingly, in both adipose tissues lipolysis increased less in SCI compared with healthy subjects, indicating that circulating catecholamines are important for the exercise-induced increase in subcutaneous adipose tissue lipolysis. In SCI subjects, the exercise-induced increase in subcutaneous adipose tissue lipolysis was not lower in decentralized than in sympathetically innervated adipose tissue. During exercise the interstitial noradrenaline and adrenaline concentrations were lower in SCI compared with healthy subjects (P < 0.05) and always lower than arterial plasma catecholamine concentrations (P < 0.05). 4. It is concluded that circulating catecholamines are important for the exercise-induced increase in subcutaneous adipose tissue lipolysis while sympathetic nerve activity is not.

Sympathetic nervous system activity and cardiovascular homeostatis during head-up tilt in patients with spinal cord injuries

The relationship between sympathetic nervous system activity and cardiovascular responses to head-up tilt in patients with spinal cord injuries and in able-bodied subjects was studied. Twenty-seven adults, nine in each of the three groups (tetraplegia, paraplegia, and able-bodied subjects) were tilted 70 degrees, head up, for 12 minutes after 20 minutes supine rest. Differences between steady-state measurements of mean arterial pressure, stroke volume, and sympathetic nervous system activity were estimated in both positions. Sympathetic nervous system activity was reflected by the low-frequency peak of the blood pressure variability spectrum. From supine rest to head-up tilt, low-frequency power increased in able-bodied subjects (median, 0.42 mm Hg2, p = 0.003), which was different (p = 0.015) from patients with tetraplegia and paraplegia (-0.15 and -0.10 mm Hg2, respectively). Stroke volume and mean arterial pressure decreased in patients with tetraplegia (-40% and -9 mm Hg, respectively; p = 0.008, both variables) more than in able-bodied subjects (-33%, 11 mm Hg, respectively) or patients with paraplegia (-24%, 8 mm Hg, respectively). Results indicated increased sympathetic nervous system activity during head-up tilt in able-bodied subjects, but not in patients with paraplegia or tetraplegia, whereas patients with tetraplegia, but not paraplegia, showed poorer cardiovascular homeostasis than able-bodied subjects. This suggests that patients with paraplegia maintained cardiovascular homeostasis during head-up tilt without increased sympathetic nervous system activity.

Lipoproteins and free plasma catecholamines in spinal cord injured men with different injury levels

Persons with spinal cord injury (SCI) are especially prone to atherogenesis. This is partly explained by an unfavourable lipoprotein profile in these individuals. The impairment of the sympathetic nervous system, and the fact that SCI subjects are subject to extreme physical inactivity, may have an influence on their lipid profile and lipoprotein(a) concentration. We made a detailed investigation of the lipid profile as well as serum levels of adrenaline and noradrenaline in 80 men with SCI ranging from tetraplegia to low paraplegia and in 16 control subjects. The lipid profile of tetraplegics was characterized by elevated very low-density lipoprotein cholesterol and triglyceride levels and reduced high-density lipoprotein levels. In contrast, paraplegics had significantly higher low-density lipoprotein and total cholesterol levels. Tetraplegics had lower and the low-lesion paraplegics had higher adrenaline and noradrenaline levels than the high-lesion paraplegics and the control subjects. High-lesion SCI subjects also showed an extreme reduction in VO2max. The lipoprotein profile was dependent on the injury level and serum catecholamine concentrations. The lower the noradrenaline values, the lower the high-density lipoprotein cholesterol. The low-density lipoprotein also correlated to catecholamines and particularly adrenaline values. Despite the correlation between lipoprotein(a) and adrenaline, no significant differences in lipoprotein(a) were found within SCI individuals as well as between SCI individuals and control subjects, indicating the predominantly genetic determination of lipoprotein(a) and thus the cardiovascular risk. Different serum catecholamine levels due to impairment of sympathetic nervous system and VO2max levels were observed in SCI subjects. This was associated with a higher lipid risk profile for cardiovascular diseases; however, the risk profile is dependent on the lesion level.

Physical performance and cardiovascular and metabolic adaptation of elite female wheelchair basketball players in wheelchair ergometry and in competition

Spinal cord injury leads to a pronounced reduction of cardiovascular, pulmonary, and metabolic ability. Physical activity, up to and including high-performance sports, has obtained importance in the course of rehabilitation and the postclinical phase. Thirteen elite female wheelchair basketball players from the German National Basketball Team and 10 female sedentary spinal cord-injured persons were examined in the study. Heart volume was measured by an echocardiography. All subjects underwent a graded exercise test on a wheelchair ergometer. Additionally, heart rate, lactate, and player points were measured during a competitive basketball game in wheelchair basketball players. Cardiac dimensions were larger for spinal cord-injured wheelchair basketball players (620.3 ml; 9.6 ml x kg(-1)) in comparison with spinal cord-injured persons (477.4 ml; 8.2 ml x kg(-1)) but did not exceed the heart volume of untrained nonhandicapped persons. In contrast, athletes with amputations or those having had poliomyelitis reached training-induced cardiac hypertrophy in relation to body mass (713.7 ml; 13.2 ml x kg(-1)), as observed in nonhandicapped athletes. During graded wheelchair ergometry, wheelchair basketball players showed a higher maximal work rate (59.9 v 45.5 W), maximal oxygen consumption (33.7 v 18.3 ml x min(-1) x kg(-1)), and maximal lactate (9.1 v 5.47 mmol x l(-1)) without a difference in maximal heart rate and workload at AT4 than did spinal cord-injured persons. The average heart rate during the wheelchair basketball game was 151 x min(-1), and the lactate concentration was 1.92 mmol x l(-1). Female athletes with a less severe handicap and higher maximal oxygen consumption during the graded exercise test reached a higher game level in the evaluation. During the competitive basketball game, high cardiovascular stress was observed, indicating a fast aerobic metabolism; the anaerobic lactic acid capacity played a subordinate role. Wheelchair basketball is an effective and suitable sport to enhance physical performance and to induce positive physiological adaptations.

Catecholamines, heart rate, and oxygen uptake during exercise in persons with spinal cord injury

The purpose of this study was to investigate the influence of different injury levels in persons with spinal cord injury (SCI) on epinephrine (Epi) and norepinephrine (NE) at rest and during graded wheelchair exercise and the related changes in heart rate and O2 uptake (VO2). Twenty tetraplegics (Tetra), 10 high-lesion paraplegics (HLPara), 20 paraplegics with SCI below T5 (MLPara), and 18 able-bodied, nonhandicapped persons (AB) were examined. Because of the higher level of interruption of the sympathetic pathways, Tetra persons showed lower Epi and NE at rest and only slight increases during exercise compared with all other groups; the Tetra subjects' impaired cardiac sympathetic innervation caused restricted cardioacceleration and strongly reduced maximal VO2. When compared with AB persons, HLPara had comparable NE but lower Epi levels as a result of partial innervation of the noradrenergic system and denervation of the adrenal medulla. MLPara subjects showed an augmented basal and exercise-induced upper spinal thoracic sympathetic activity compared with AB subjects. The increase in heart rate in relation to VO2 was higher in HLPara because of a smaller stroke volume as a result of venous blood pooling. The different exercise response in persons with SCI is a result of the interruption of pathways in the spinal cord to the peripheral sympathetic nervous system in addition to the motor paralysis.