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

Statistical analysis of RR series variability in spinal cord injured persons

Disabled persons with spinal cord injury are prone to cardiovascular dysfunction and an increased risk of cardiovascular disease. Rehabilitation of the disabled person is a critical task as it involves multiple therapies. Physical exercise is an important component of rehabilitation, and depends on cardiovascular health. Reduced RR variability is a marker of poor cardiac health. Time domain RR variability analysis of 38 normal healthy subjects and 20 spinal cord injured subjects has been carried out and compared. In this study, RR intervals were recorded in three different modes or positions: supine, sitting and five-second rhythm respiration. At a time of 150 s RR interval data were acquired in each mode and analysed. Statistical parameters (mean, HR, STD, NN50 and pNN50) were calculated. It was observed that most of the indices were significantly and substantially altered in spinal cord injured persons.

Effects of compression stockings on sympathetic activity and heart rate variability in individuals with spinal cord injury

OBJECTIVE

To investigate whether wearing graduated compression stockings (GCS) could affect the sympatho-adrenergic and heart rate variability (HRV) responses at rest and after a strenuous wheelchair exercise in individuals with spinal cord injury (SCI).

DESIGN

Crossover trial.

SETTING

Department of Physical Medicine and Rehabilitation, Saint Etienne, France.

PARTICIPANTS

Nine men with SCI (five with low paraplegia: LP, four with high paraplegia: HP).

INTERVENTIONS

Two maximal wheelchair exercise tests: with and without GCS (21 mmHg).

MAIN OUTCOME MEASURES

HRV measurements: high frequency (HF), low frequency (LF), and LF/HF ratio. Norepinephrine (NOR) and epinephrine (EPI), at rest and post-exercise. Secondary measures were: blood pressure, heart rate, maximal power output, oxygen uptake, stroke volume, cardiac output, at rest, during and after exercise.

RESULTS

When wearing GCS: LFnu(wavelet-post) significantly increased and HFnu(wavelet-post) significantly decreased (P < 0.05) in SCI subjects, leading to an enhance ratio of LF(wavelet)/HF(wavelet) and a significantly increased in NOR(rest) (P < 0.05).

CONCLUSIONS

GCS induces an enhanced sympathetic activity in individuals with paraplegia, regardless of the level of the injury. Enhanced post-exercise sympathetic activity with GCS may help prevent orthostatic hypotension or post-exercise hypotension.

31st g. Heiner sell lectureship: secondary medical consequences of spinal cord injury

Persons with spinal cord injury (SCI) have secondary medical consequences of paralysis and/or the consequences of extreme inactivity. The metabolic changes that result from reduced activity include insulin resistance with carbohydrate disorders and dyslipidemia. A higher prevalence of coronary artery calcification was found in persons with SCI than that in matched able-bodied controls. A depression in anabolic hormones, circulating testosterone and growth hormone, has been described. Adverse soft tissue body composition changes of increased adiposity and reduced skeletal muscle are appreciated. Immobilization is the cause for sublesional disuse osteoporosis with an associated increased risk of fragility fracture. Bowel dysmotility affects all segments of the gastrointestinal tract, with an interest in better defining and addressing gastroesophageal reflux disease and difficulty with evacuation. Developing and testing more effective approaches to cleanse the bowel for elective colonoscopy are being evaluated. The extent of respiratory dysfunction depends on the level and completeness of SCI. Individuals with higher spinal lesions have both restrictive and obstructive airway disease. Pharmacological approaches and expiratory muscle training are being studied as interventions to improve pulmonary function and cough strength with the objective of reducing pulmonary complications. Persons with spinal lesions above the 6th thoracic level lack both cardiac and peripheral vascular mechanisms to maintain blood pressure, and they are frequently hypotensive, with even worse hypotension with upright posture. Persistent and/or orthostatic hypotension may predispose those with SCI to cognitive impairments. The safety and efficacy of anti-hypotensive agents to normalize blood pressure in persons with higher level cord lesions is being investigated.

Comparison of 24-hour cardiovascular and autonomic function in paraplegia, tetraplegia, and control groups: implications for cardiovascular risk

BACKGROUND

Fluctuations in 24-hour cardiovascular hemodynamics, specifically heart rate (HR) and blood pressure (BP), are thought to reflect autonomic nervous system (ANS) activity. Persons with spinal cord injury (SCI) represent a model of ANS dysfunction, which may affect 24-hour hemodynamics and predispose these individuals to increased cardiovascular disease risk.

OBJECTIVE

To determine 24-hour cardiovascular and ANS function among individuals with tetraplegia (n=20; TETRA: C4-C8), high paraplegia (n=10; HP: T2-T5), low paraplegia (n=9; LP: T7-T12), and non-SCI controls (n=10). Twenty-four-hour ANS function was assessed by time domain parameters of heart rate variability (HRV); the standard deviation of the 5-minute average R-R intervals (SDANN; milliseconds/ms), and the root-mean square of the standard deviation of the R-R intervals (rMSSD; ms). Subjects wore 24-hour ambulatory monitors to record HR, HRV, and BP. Mixed analysis of variance (ANOVA) revealed significantly lower 24-hour BP in the tetraplegic group; however, BP did not differ between the HP, LP, and control groups. Mixed ANOVA suggested significantly elevated 24-hour HR in the HP and LP groups compared to the TETRA and control groups (P<0.05); daytime HR was higher in both paraplegic groups compared to the TETRA and control groups (P<0.01) and nighttime HR was significantly elevated in the LP group compared to the TETRA and control groups (P<0.01). Twenty-four-hour SDANN was significantly increased in the HP group compared to the LP and TETRA groups (P<0.05) and rMSSD was significantly lower in the LP compared to the other three groups (P<0.05). Elevated 24-hour HR in persons with paraplegia, in concert with altered HRV dynamics, may impart significant adverse cardiovascular consequences, which are currently unappreciated.

Energy expenditure and metabolism during exercise in persons with a spinal cord injury

Resting energy expenditure of persons with a spinal cord injury (SCI) is generally lower than that seen in able-bodied (AB) individuals due to the reduced amounts of muscle mass and sympathetic nervous system available. However, outside of clinical studies, much less data is available regarding athletes with an SCI. In order to predict the energy expenditure of persons with SCI, the generation and validation of prediction equations in relation to specific levels of SCI and training status are required. Specific prediction equations for the SCI would enable a quick and accurate estimate of energy requirements. When compared with the equivalent AB individuals, sports energy expenditure is generally reduced in SCI with values representing 30-75% of AB values. The lowest energy expenditure values are observed for sports involving athletes with tetraplegia and where the sport is a static version of that undertaken by the AB, such as fencing. As with AB sports there is a lack of SCI data for true competition situations due to methodological constraints. However, where energy expenditure during field tests are predicted from laboratory-based protocols, wheelchair ergometry is likely to be the most appropriate exercise mode. The physiological and metabolic responses of persons with SCI are similar to those for AB athletes, but at lower absolute levels. However, the underlying mechanisms pertaining to substrate utilization appear to differ between the AB and SCI. Carbohydrate feeding has been shown to improve endurance performance in athletes with generally low levels of SCI, but no data have been reported for mid to high levels of SCI or for sport-specific tests of an intermittent nature. Further research within the areas reviewed may help to bridge the gap between what is known regarding AB athletes and athletes with SCI (and other disabilities) during exercise and also the gap between clinical practice and performance.

Estimating MET values using the ratio of HR for persons with paraplegia

The current compendium of physical activity (CPA) cannot be applied to persons with disabilities due to the lack of physical activity (PA) they are regularly engaged in and inaccurate MET values when applied to persons with disabilities.

PURPOSE

The purposes of this study were (a) to determine whether HR ratio during PA and resting can be used to accurately predict MET values of PA in persons with paraplegia, (b) to compare individual calibration (IC) with group calibration (GC) in error reduction, and (c) to examine prediction generalizability through a cross-validation design.

METHODS

Twenty-seven participants (aged 18-45 yr) with complete and incomplete paraplegia at T6 to L4 participated in this study. Oxygen uptake (VO2) and HR were measured simultaneously at rest and during 10 PA using indirect calorimetry and a Polar HR monitor. Predicted METs were calculated using the HR ratio for six activities by applying regression analysis by group (GC) and individuals (IC), respectively. The derived equations were then cross-validated using the four other activities, and corresponding METs were calculated. Absolute error rates (AC), paired t-test, and correlation (r) were used to determine the absolute and relative difference between observed and predicted METs.

RESULTS

The overall correlation coefficient (r) between HR ratio and observed METs was 0.77 using group regression and 0.93 +/- 0.05 using individual regression. GC (R2 = 0.59, AC = 0.07%-65.25%) was less accurate than IC (R2 = 0.90 +/- 0.10, AC = 1.64%-10.26%). Cross-validation results also showed higher correlations for IC (r = 0.90 in IC and 0.72 in GC) between observed and predicted METs.

CONCLUSIONS

HR ratio was able to accurately predict METs of persons with paraplegia. IC estimated METs more accurately than GC.

Effect of carbohydrate ingestion on exercise performance and carbohydrate metabolism in persons with spinal cord injury

Carbohydrate ingestion during exercise and as a pre-exercise bolus improves exercise performance in able-bodied athletes. Little is known about the potential for carbohydrate ingestion to improve exercise performance in athletes with spinal cord injury (SCI), nor the potential physiological limitations of such a practice resulting from an SCI. Therefore, this study investigated the effects of carbohydrate ingestion on exercise performance in physically active and athletic persons with SCI. Six participants with complete SCI (neurological level of lesion ranging from C(6) to T(7)) and normal glucose tolerance were studied twice during 60 min of arm cranking at 65% of peak oxygen consumption followed by a 20-min time trial with the ingestion of either a carbohydrate drink (CHO trial: 0.5 g CHO kg(-1) body weight in 500 ml) or placebo (PLA trial) applied in a double-blind counter-balanced manner. The participants with tetraplegia had sufficient neurological function to permit voluntary arm-cranking exercise. There was no difference in time-trial performance between CHO and PLA trials (P > 0.05). The results suggest that carbohydrate ingestion in persons with SCI does not improve exercise performance.

Exercise testing using upper extremity ergometry in pediatric spinal cord injury

PURPOSE

To describe an upper extremity ergometer test for children with spinal cord injury (SCI) and examine differences based on injury level for peak heart rate (HR peak), oxygen uptake (VO 2 peak/kg), and peak power output per kilogram (W peak/kg).

METHODS

Twenty-nine children with motor complete SCI participated. Nine had low cervical (C7, C8), 9 had upper thoracic (T1-T4), and 11 had mid/low thoracic (T5-T11) SCI. HR peak, VO2 peak/kg, and W peak/kg were compared based on these 3 injury level groupings.

RESULTS

HR peak (p = 0.013), VO 2 peak/kg (p = 0.041), and W peak/kg (p = 0.001) differed between groups. The mid/low thoracic group had the highest values for each variable.

CONCLUSIONS

The differences in HR peak, VO 2 peak/kg, and W peak/kg were consistent with exercise effects reported for adults with SCI. Further research is needed to develop an appropriate standardized ergometric test for children with SCI.

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.

The longitudinal relationship between lipid profile and physical capacity in persons with a recent spinal cord injury

STUDY DESIGN

A multicenter prospective cohort study.

OBJECTIVE

To determine the longitudinal relationship between physical capacity and lipid profile in persons with spinal cord injury (SCI) during and 1 year after rehabilitation.

SETTING

Eight Dutch rehabilitation centers with a specialized SCI unit.

METHODS

A total of 206 subjects with SCI (78 with tetraplegia) participated. The longitudinal relationship between lipid profiles (total cholesterol (TC), high- (HDL) and low-density lipoprotein (LDL) and triglycerides (TG) and physical capacity (peak power output (POpeak), peak oxygen uptake (VO2peak), and muscle strength) was investigated during inpatient SCI rehabilitation (start, 3 months later, discharge) and 1 year after discharge. A correction was made for the possible confounding variables age, body mass index, gender, time since injury, lesion level and completeness.

RESULTS

HDL and the ratios LDL/HDL and TC/HDL showed a significant and favorable relationship with VO2peak, POpeak and muscle strength. TG was positively related to POpeak and muscle strength.

CONCLUSIONS

More favorable lipid profiles were seen in people with a higher physical capacity after correction for personal and lesion characteristics. Therefore, improving the physical capacity by being active during daily life or in sport may further improve the lipid profile and thus reduce the risk for coronary heart disease.

Control of heart rate variability by cardiac parasympathetic nerve activity during voluntary static exercise in humans with tetraplegia

Heart rate (HR) is controlled solely by via cardiac parasympathetic outflow in tetraplegic individuals, who lack supraspinal control of sympathetic outflows and circulating catecholamines but have intact vagal pathways. A high-frequency component (HF; at 0.15–0.40 Hz) of the power spectrum of HR variability and its relative value against total power (HF/Total) were assessed using a wavelet transform to identify cardiac parasympathetic outflow. The relative contribution of cardiac parasympathetic and sympathetic outflows to controlling HR was estimated by comparing the HF/Total-HR relationship between age-matched tetraplegic and normal men. Six tetraplegic men with complete cervical spinal cord injury performed static arm exercise at 35% of the maximal voluntary contraction until exhaustion. Although resting cardiac output and arterial blood pressure were lower in tetraplegic than normal subjects, HR, HF, and HF/Total were not statistically different between the two groups. When tetraplegic subjects developed the same force during exercise as normal subjects, HF and HF/Total decreased to 67–90% of the preexercise control and gradually recovered 1.5 min after exercise. The amount and time course of the changes in HF/Total during and after exercise coincided well between both groups. In contrast, the increase in HR at the start of exercise was blunted in tetraplegic compared with normal subjects, and the HR recovery following exercise was also delayed. It is likely that, although the withdrawal response of cardiac parasympathetic outflow is preserved in tetraplegic subjects, sympathetic decentralization impairs the rapid acceleration of HR at the onset of exercise and the rapid deceleration following exercise.

The relationship between perceived exertion and physiologic indicators of stress during graded arm exercise in persons with spinal cord injuries

OBJECTIVE

To examine the relationship between psychologic cues of somatic stress and physiologic responses to exercise in persons with paraplegia and tetraplegia.

DESIGN

Repeated measures with 2 comparison groups.

SETTING

Academic medical center.

PARTICIPANTS

Forty-two subjects between 18 and 69 years of age with motor-complete spinal cord injury (SCI) resulting in paraplegia or tetraplegia (American Spinal Injury Association grades A and B).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Subjects underwent peak graded arm ergometry during which heart rate, oxygen consumption (VO2), minute ventilation (VE), and ratings of perceived exertion (RPE) (Borg Categorical 6-20 Scale) were measured at successive work rate increments from baseline to fatigue.

RESULTS

There were inconsistent associations among the outcomes. For subjects with tetraplegia, RPE related positively to heart rate at the initial work rate, but there were no other significant correlations. For subjects with paraplegia, RPE did not correlate significantly with heart rate, VO2, or VE. VO2 and Ve related positively at the first and last work rates. In general, heart rate, VO2, and Ve increased as the exercise intensity increased, and were more pronounced in subjects with paraplegia. While RPE values increased with increasing work rates for each group, we found no differences between groups.

CONCLUSIONS

Our findings contradict the well-accepted relationships between RPE and both heart rate and VO2 during exercise by people without disabilities, and challenge the use of RPE as a valid psychophysiologic index of perceived exertion in persons with SCI.

Cardiovascular Health and Fitness in Persons with Spinal Cord Injury

There are many issues after spinal cord injury that have an impact on cardiovascular health and fitness. This article discusses many of the secondary conditions and changes that occur and how they are affected by maintenance of an active lifestyle. It also discusses many of the benefits and difficulties individuals face in maintaining a regular exercise program after spinal cord injury.

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.

Attenuation of natural killer cell activity during 2-h exercise in individuals with spinal cord injuries

DESIGN

Non-randomized study.

OBJECTIVE

To determine natural killer cell cytotoxic activity (NKCA) to 2-h arm ergometer exercise in persons with spinal cord injuries (SCI) and the underlying mechanism of such response.

SETTING

University of Occupational and Environmental Health, Japan.

METHODS

We examined NKCA response to 2-h arm crank ergometer exercise at 60% of maximum oxygen consumption (VO(2max)) in SCI and able-bodied persons. NKCA and plasma concentrations of prostaglandin E(2) (PGE(2)), adrenaline and cortisol were measured before, during and immediately after the exercise. The study included seven subjects with SCI between Th11 and L4 and six able-bodied persons.

RESULTS

NKCA in able-bodied subjects increased (P<0.05) at 60 min of exercise and immediately after the exercise, and remained elevated up to 2 h after exercise. However, NKCA in SCI decreased (P<0.05) immediately after exercise but recovered at 2 h after exercise. Plasma adrenaline in both groups increased significantly (P<0.05) immediately after exercise and returned to baseline level 2 h after the exercise. Plasma cortisol in both groups remained constant throughout the study. In SCI, PGE(2) significantly increased immediately after 2 h exercise and returned to the baseline level 2 h after exercise; however, it remained unchanged during the test in able-bodied subjects.

CONCLUSION

Our results suggested that increase of PGE(2) in SCI partially contributes to NKCA.

Cardiovascular disease in spinal cord injury: an overview of prevalence, risk, evaluation, and management

Cardiovascular disease is a growing concern for the spinal cord-injured (SCI) population. For long-term SCI, morbidity and mortality from cardiovascular causes now exceeds that caused by renal and pulmonary conditions, the primary causes of mortality in previous decades. Although risk estimates commonly used for ambulatory individuals have not been established from follow-up studies in SCI, nearly all risk factors tend to be more prevalent in SCI subjects compared with ambulatory subjects. These risks include a greater prevalence of obesity, lipid disorders, metabolic syndrome, and diabetes. Daily energy expenditure is significantly lower in SCI individuals, not only because of a lack of motor function, but also because of a lack of accessibility and fewer opportunities to engage in physical activity. Autonomic dysfunction caused by SCI is also associated with several conditions that contribute to heightened cardiovascular risk, including abnormalities in blood pressure, heart rate variability, arrhythmias, and a blunted cardiovascular response to exercise that can limit the capacity to perform physical activity. Thus, screening, recognition, and treatment of cardiovascular disease should be an essential component of managing individuals with SCI, and judicious treatment of risk factors can play an important role in minimizing the incidence of cardiovascular disease in these individuals. This article reviews the cardiovascular consequences of chronic SCI, including the prevalence of cardiovascular disease and risk factors unique to these individuals, and provides a synopsis of management of cardiovascular disease in this population.

Response to Exercise in Paraplegics and Able Bodied Subjects: A New Formula to Estimate the Theoretical Oxygen Uptake

Purpose:

To compare the response to physical exercise between subjects with spinal cord injury (SCI) and able-bodied (AB) subjects with the objective of developing a new formula for the indirect calculation of oxygen consumption (VO2).

Subjects:

20 individuals with paraplegia below Th6and 22 AB subjects have participated in the study.

Measures:

A graded work test was performed on an arm ergometer, starting with 10 w and increasing the power in 10 w each minute up to maximal effort. SCI group present a lower response to the different workloads with respect to the AB group.

Results:

In the SCI group, a statistical association was found between workload and VO2(r = 0.956,P< 0.001). The proposed equation to calculate the theoretical VO2was the following: 0.487 + (0.013 · watts performed).

Conclusions:

SCI males, respect to AB subjects, show differences in ventilatory response to exercises. We propose a new formula for the indirect calculation of VO2in relation to workload.

Cholinergic bronchomotor tone and airway caliber in tetraplegic patients

STUDY DESIGN

Case-control study.

OBJECTIVES

To evaluate the resting airway caliber in subjects with tetraplegia; to define the participation of cholinergic innervation in this condition; and to determine if baclofen modifies this pattern.

SETTING

A rehabilitation hospital, Brasília, Brazil.

METHODS

We studied 18 tetraplegic patients, with complete motor loss between C4 and C8, and 18 healthy control subjects by measuring airway conductance, before and after inhaled ipratropium bromide.

RESULTS

At baseline, the pulmonary function parameters revealed mild-to-moderate restrictive impairment in tetraplegic patients as defined by decreases in total lung capacity and predicted percent of slow vital capacity. The average baseline specific airway conductance (sGaw) was less in tetraplegic patients (0.25+/-0.11) than in the control group (0.41+/-0.10 l/s/cm H(2)O) (P<0.0001). All patients had improved post-bronchodilator sGaw >or=40% compared with only four of the 18 controls (P<0.001). The average increase for tetraplegic patients was 235% (+/-93) versus 25% (+/-24) for controls (P<0.0001). Analysis of variance for repeated measurements showed significant difference in sGaw between the control and spinal cord injury (SCI) groups (P<0.0001) following bronchodilator challenge, but found no difference for total gas volume. No difference for mean basal sGaw and bronchodilator challenge was encountered comparing tetraplegic patients using baclofen to those not using it.

CONCLUSIONS

Cervical SCI patients have a reduced baseline conductance compared to controls. Marked improvement occurs after an inhaled anticholinergic drug. This behavior was not affected by the use of baclofen. The study adds support to the hypothesis of an increased cholinergic bronchomotor tone in tetraplegic patients.

The individual relationship between heart rate and oxygen uptake in people with a tetraplegia during exercise

STUDY DESIGN

Descriptive study.

OBJECTIVE

To examine the individual heart rate-oxygen uptake (HR-VO(2)) relationship during exercise in persons with tetraplegia (TP).

SETTING

Rehabilitation Centre Heliomare, Wijk aan Zee, The Netherlands.

METHODS

The HR-VO(2) relationship was determined in untrained subjects with motor complete TP (C5 or C6, n=10 and C7 or C8, n=10) during a discontinuous graded exercise hand cycle test. The mean HR and VO(2) of the final 60 s of 2-min exercise blocks were used for calculation of the individual correlation coefficient and the standard error of the estimate (SEE).

RESULTS

Two subjects of the C5-C6 group were not able to complete the test. Individual Pearson's correlation coefficients (r) ranged from 0.68 to 0.97 and SEE from 2.6 to 22.4% VO(2)-Reserve (VO(2)R). The mean Pearson's r and SEE were 0.81+/-0.12 and 10.6+/-5.6% VO(2)R in the C5-C6 group and 0.91+/-0.07 and 7.0+/-3.2% VO(2)R in the C7-C8 group, respectively. Two subjects of the C5-C6 group and six subjects of the C7-C8 group attained a linear HR-VO(2) relationship with an acceptable SEE (< or =6.0%) and r (>0.90).

CONCLUSIONS

The HR-VO(2) relationship appeared linear in only eight out of 18 subjects. An individual analysis of the HR-VO(2) relationship is necessary to determine whether HR can be used to quantify exercise intensity. The use of HR to prescribe training intensity should be reconsidered in persons with TP.

SPONSORSHIP

This study is supported from a grant by ZON-MW.

Physical capacity in wheelchair-dependent persons with a spinal cord injury: a critical review of the literature

STUDY DESIGN

Review of publications.

OBJECTIVE

To assess the level of physical capacity (peak oxygen uptake, peak power output, muscle strength of the upper extremity and respiratory function) in wheelchair-dependent persons with a spinal cord injury (SCI).

SETTING

Erasmus MC, University Medical Centre Rotterdam, The Netherlands.

METHODS

Pubmed (Medline) search of publications from 1980 onwards. Studies were systematically assessed. Weighted means were calculated for baseline values.

RESULTS

In tetraplegia, the weighted mean for peak oxygen uptake was 0.89 l/min for the wheelchair exercise test (WCE) and 0.87 l/min for arm-cranking or hand-cycling (ACE). The peak power output was 26 W (WCE) and 40 W (ACE). In paraplegia, the peak oxygen uptake was 2.10 l/min (WCE) and 1.51 l/min (ACE), whereas the peak power output was 74 W (ACE) and 85 W (WCE). In paraplegia, muscle strength of the upper extremity and respiratory function were comparable to that in the able-bodied population. In tetraplegia muscle strength varied greatly, and respiratory function was reduced to 55-59% of the predicted values for an age-, gender- and height-matched able-bodied population.

CONCLUSIONS

Physical capacity is reduced and varies in SCI. The variation between results is caused by population and methodological differences. Standardized measurement of physical capacity is needed to further develop comparative values for clinical practice and rehabilitation research.

Effect of a convenient single 90-mg pamidronate dose on biochemical markers of bone metabolism in patients with acute spinal cord injury

BACKGROUND/OBJECTIVE

To describe the biochemical and adverse effects of a convenient single 90 mg pamidronate dose in patients with acute spinal cord injury (SCI) and compare these effects with those observed in a previous similar study using a 30 mg/d x 3-day pamidronate dosing regimen.

STUDY DESIGN

Retrospective cohort study.

SETTING

University-based rehabilitation center in New York City.

METHODS

A total of 32 patients with SCI were evaluated for biochemical response and adverse events associated with pamidronate therapy. All patients were screened at or near admission for acute rehabilitation, received calcium (1,000 mg daily) and calcitriol (0.25 micrg daily) therapy daily, and on day 4, received a single dose of pamidronate, 90 mg by intravenous infusion, over 4 hours. Serum calcium and phosphate levels were closely monitored, and 2 weeks after pamidronate, biochemical bone markers were re-evaluated.

RESULTS

Responses of biochemical markers of bone resorption (N-telopeptide and 24-hour urinary calcium excretion) to pamidronate 90 mg were consistent with an antiresorptive effect, although less than that observed with a 30 mg/d x 3-day pamidronate dosing regimen. The frequency of hypocalcemia was greater, and hypophosphatemia was less than the 30 mg/d x 3-day pamidronate dosing regimen. Fever was more frequent (78%) with the 90-mg single dose of pamidronate compared with the 30 mg/d x 3-day pamidronate dosing regimen (20%).

CONCLUSIONS

Single-dose pamidronate 90 mg is effective at reducing biochemical markers of bone hyperresorption in patients with acute SCI but is associated with a greater incidence of fever compared with a 30 mg/d x 3-day dosing regimen.

Cardiorespiratory responses during passive walking-like exercise in quadriplegics

STUDY DESIGN

Cross-sectional and comparative investigation using quadriplegics (QP) and nondisabled subjects (ND).

OBJECTIVE

To evaluate cardiorespiratory responses during passive walking-like exercise (PWE) in QP.

SETTING

National Rehabilitation Center for Persons with Disabilities in Japan.

METHOD

The subjects were seven male QP with complete lesion (age: 27.0 +/- 5.4, injured level: C6-C7) and six male ND (age: 26.3 +/- 4.5). Cardiorespiratory responses were measured until voluntary fatigue during PWE, the rhythmical activity of paralyzed lower limbs synchronized with arm movements.

RESULTS

There were no significant differences in oxygen consumption (VO(2)), pulmonary ventilation (VE), heart rate (HR) and oxygen pulse (O(2) pulse) between QP and ND during PWE. ND showed increased ventilatory equivalent for oxygen (VE/VO(2) ratio) during exercise, while QP showed a significantly greater respiratory rate (RR) during exercise than ND (P < 0.05).

CONCLUSION

PWE elicited an increase in VO(2) with workload increment in QP similar to ND. However, higher RR suggested the intrinsic dysfunction of RR control during submaximal exercise in QP. From these results, it was thought that respiratory response would be the restriction factor of efficient oxygen transportation during PWE in QP.

Plasma glutamine concentration in spinal cord injured patients

Glutamine, a non-essential amino acid, is the most important source of energy for macrophages and lymphocytes. Reduction in its plasma concentration is related with loss of immune function, as leukocyte proliferation and cytokine production. It is well known that glutamine is largely produced by the skeletal muscle which is severely compromised as a consequence of the paralysis due to the damage of the spinal cord. In spinal cord injury (SCI) patients, infections, such as pneumonia and sepsis in general, are a major cause of morbidity and mortality. In comparison with the control group, a 54% decrease in plasma glutamine concentration was observed as well as a decrease in the production of TNF and IL-1 by peripheral blood mononuclear cells cultivated for 48 h in SCI patients. Therefore, we propose that a decrease in plasma glutamine concentration is an important contributor to the immunosuppression seen in SCI patients.

Response of the arterial blood pressure of quadriplegic patients to treadmill gait training

Blood pressure pattern was analyzed in 12 complete quadriplegics with chronic lesions after three months of treadmill gait training. Before training, blood pressure values were obtained at rest, during treadmill walking and during the recovery phase. Gait training was performed for 20 min twice a week for three months. Treadmill gait was achieved using neuromuscular electrical stimulation, assisted by partial body weight relief (30-50%). After training, blood pressure was evaluated at rest, during gait and during recovery phase. Before and after training, mean systolic blood pressures and heart rates increased significantly during gait compared to rest (94.16 +/- 5.15 to 105 +/- 5.22 mmHg and 74.27 +/- 10.09 to 106.23 +/- 17.31 bpm, respectively), and blood pressure decreased significantly in the recovery phase (86.66 +/- 9.84 and 57.5 +/- 8.66 mmHg, respectively). After three months of training, systolic blood pressure became higher at rest (94.16 +/- 5.15 mmHg before training and 100 +/- 8.52 mmHg after training; P < 0.05) and during gait exercise (105 +/- 5.22 mmHg before and 110 +/- 7.38 mmHg after training; P < 0.05) when compared to the initial values, with no changes in heart rate. No changes occurred in blood pressure during the recovery phase, with the lower values being maintained. A drop in systolic pressure from 105 +/- 5.22 to 86.66 +/- 9.84 mmHg before training and from 110 +/- 7.38 to 90 +/- 7.38 mmHg after training was noticed immediately after exercise, thus resulting in hypotensive symptoms when chronic quadriplegics reach the sitting position from the upright position.

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.

Exercise Prescription in Subjects With Spinal Cord Injuries

OBJECTIVE

To evaluate the effect of training with ergometers on subjects with spinal cord injury (SCI) in the postacute phase.

DESIGN

Cohort study.

SETTING

A spinal unit at a physical medicine and rehabilitation institute.

PARTICIPANTS

Twenty-one subjects with SCI in the postacute phase as a consecutive sample were chosen on a strict first-come, first-chosen basis. All patients completed the study.

INTERVENTIONS

A 6-week (5d/wk, 90 min/d) program consisting of exercises with the ergometers formulated (as intensity and duration) for each patient on the basis of the results obtained in specific cardiovascular tests.

MAIN OUTCOME MEASURES

Parameters of workload levels, as well as hematologic and hormonal parameters, recorded during the first 6 weeks of training.

RESULTS

The workload performed during the training showed an initial increase, but it reached a plateau in week 4. No statistically meaningful variations in the workload emerged between the fourth and the sixth weeks of monitoring. There were no hematologic or hormonal signs of overtraining.

CONCLUSIONS

Strengthening and aerobic rehabilitation programs for patients with subacute SCI should be limited to 4 weeks, followed by an independent maintenance exercise program. The strengthening program is safe for these patients.

Cardiovascular control during voluntary static exercise in humans with tetraplegia

The purpose of the present study was 1) to investigate whether an increase in heart rate (HR) at the onset of voluntary static arm exercise in tetraplegic subjects was similar to that of normal subjects and 2) to identify how the cardiovascular adaptation during static exercise was disturbed by sympathetic decentralization. Mean arterial blood pressure (MAP) and HR were noninvasively recorded during static arm exercise at 35% of maximal voluntary contraction in six tetraplegic subjects who had complete cervical spinal cord injury (C(6)-C(7)). Stroke volume (SV), cardiac output (CO), and total peripheral resistance (TPR) were estimated by using a Modelflow method simulating aortic input impedance from arterial blood pressure waveform. In tetraplegic subjects, the increase in HR at the onset of static exercise was blunted compared with age-matched control subjects, whereas the peak increase in HR at the end of exercise was similar between the two groups. CO increased during exercise with no or slight decrease in SV. MAP increased approximately one-third above the control pressor response but TPR did not rise at all throughout static exercise, indicating that the slight pressor response is determined by the increase in CO. We conclude that the cardiovascular adaptation during voluntary static arm exercise in tetraplegic subjects is mainly accomplished by increasing cardiac pump output according to the tachycardia, which is controlled by cardiac vagal outflow, and that sympathetic decentralization causes both absent peripheral vasoconstriction and a decreased capacity to increase HR, especially at the onset of exercise.

Foot Cooling Reduces Exercise-Induced Hyperthermia in Men with Spinal Cord Injury

The number of individuals with spinal cord injury (SCI) participating in sports at recreational and elite levels is on the rise. However, loss of autonomic nervous system function below the lesion can compromise thermoregulatory capacity and increase the risk of heat stress relative to able-bodied (AB) individuals.

PURPOSE

To test the hypotheses that exercise in a heated environment would increase tympanic temperature (TTY) more in individuals with SCI than AB individuals, and that foot cooling using a new device would attenuate the rise in TTY during exercise in both groups.

METHODS

Six subjects with SCI (lesions C5-T5) and six AB controls were tested in a heated environment (means +/- SEM, temperature = 31.8 +/- 0.2 degrees C, humidity = 26 +/- 1%) for 45 min at 66% +/- 5 of arm cranking VO2peak and 30 min of recovery on two separate occasions with foot cooling (FC) or no foot cooling (NC) in randomized order.

RESULTS

During exercise and recovery in both trials, SCI TTY was elevated above baseline (P < 0.001) but more so in the NC versus FC trial (1.6 +/- 0.2 degrees C vs 1.0 +/- 0.2 degrees C, respectively, P < 0.005). Within the AB group, TTY was elevated above baseline for both trials (P < 0.001) with peak increases of 0.5 +/- 0.2 degrees C and 0.3 +/- 0.2 degrees C for NC and FC, respectively. TTY, face, and back temperature were higher in both SCI trials compared with AB trials (P < 0.05). Heart rate during exercise and recovery was lower in the SCI FC versus SCI NC (P < 0.05).

CONCLUSION

These results suggest that extraction of heat through the foot may provide an effective way to manipulate tympanic temperature in individuals with SCI, especially during exercise in the heat.

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.

Cardiovascular responses to endotracheal intubation in patients with acute and chronic spinal cord injuries

Endotracheal intubation usually causes transient hypertension and tachycardia. We investigated whether the cardiovascular responses to intubation change as a function of the time elapsed in patients with spinal cord injury. One-hundred-six patients with traumatic complete spinal cord injury were grouped into acute and chronic groups according to the time elapsed (less than and more than 4 wk after injury) and into those with quadriplegia and paraplegia according to the level of injury (above C7 and below T5): acute quadriplegia, n = 26; chronic quadriplegia, n = 27; acute paraplegia, n = 24; and chronic paraplegia, n = 29. Twenty-five patients with no spinal cord injury served as controls. Systolic arterial blood pressure (SAP), heart rate, and plasma concentrations of catecholamines were measured. The intubation did not affect SAP in either the acute or chronic quadriplegics, but it significantly increased SAP in both acute and chronic paraplegics. Heart rate was significantly increased in all groups; however, the magnitude of change was less in acute quadriplegics than in the other groups. Plasma concentrations of norepinephrine increased in every group but the acute quadriplegics. The magnitude of increase was attenuated in chronic quadriplegics, accentuated in acute paraplegics, and similar in chronic paraplegics when compared with controls. The incidence of arrhythmias did not differ among groups. We conclude that the cardiovascular and catecholamine responses to endotracheal intubation may change as a function of the time elapsed and the level of spinal cord injury.

IMPLICATIONS

Cardiovascular and catecholamine responses to endotracheal intubation may differ according to the time elapsed and the level of injury in patients with complete spinal cord injury.

Cardiac homeostasis is independent of calf venous compliance in subjects with paraplegia

The purpose of this study was to examine cardiac hemodynamics during acute head-up tilt (HUT) and calf venous function during acute head-down tilt (HDT) in subjects with paraplegia compared with sedentary nondisabled controls. Nineteen paraplegic males (below T6) and nine age-, height-, and weight-matched control subjects participated. Heart rate, stroke volume, and cardiac output were assessed using the noninvasive acetylene uptake method. Venous vascular function of the calf was assessed using venous occlusion plethysmography. After supine measurements were collected, the table was moved to 10 degrees HDT followed by the three levels of HUT (10, 35, and 75 degrees ) in random order. Cardiac hemodynamics were similar between the groups at all positions. Calf circumference was significantly reduced in the paraplegic group compared with the control group (P < 0.001). Venous capacitance and compliance were significantly reduced in the paraplegic compared with control group at supine and HDT. Neither venous capacitance (P = 0.37) nor compliance (P = 0.19) increased from supine with 10 degrees HDT in the paraplegic group. A significant linear relationship was established between supine venous compliance and supine cardiac output in the control group (r = 0.80, P < 0.02) but not in the paraplegic group. The findings of reduced calf circumference and similar venous capacitance at supine rest and 10 degrees HDT in the paraplegic group imply that structural changes may have limited venous dispensability in individuals with chronic paraplegia. Furthermore, the lack of a relationship between supine venous compliance and supine cardiac output suggests that cardiac homeostasis does not rely on venous compliance in subjects with paraplegia.

Allometric cascade: a model for resolving body mass effects on metabolism

Expanding upon a preliminary communication (Nature 417 (2002) 166), we here further develop a "multiple-causes model" of allometry, where the exponent b is the sum of the influences of multiple contributors to control. The relative strength of each contributor, with its own characteristic value of b(i), is determined by c(i), the control contribution or control coefficient. A more realistic equation for the scaling of metabolism with body size thus can be written as BMR=MR(0)Sigmac(i)(M/M(0))(bi), where MR(0) is the "characteristic metabolic rate" of an animal with a "characteristic body mass", M(0). With M(0) of 1 unit mass (usually kg), MR(0) takes the place of the value a, found in the standard scaling equation, b(i) is the scaling exponent of the process i, and c(i) is its control contribution to overall flux, or the control coefficient of the process i. One can think of this as an allometric cascade, with the b exponent for overall energy metabolism being determined by the b(i) and c(i) values for key steps in the complex pathways of energy demand and energy supply. Key intrinsic factors (such as neural and endocrine processes) or ecological extrinsic factors are considered to act through this system in affecting allometric scaling of energy turnover. Applying this model to maximum vs. BMR data for the first time explains the differing scaling behaviour of these two biological states in mammals, both in the absence and presence of intrinsic regulators such as thyroid hormones (for BMR) and catecholamines (for maximum metabolic rate).

The effect of locomotor training combined with functional electrical stimulation in chronic spinal cord injured subjects: walking and reflex studies

With the new developments in traumatology medicine, the majority of spinal cord injuries sustained are clinically incomplete and the proportion is likely to continue to rise. Thus, it is necessary to continue to develop new treatment and rehabilitation strategies and understand the factors that can enhance recovery of walking following spinal cord injury (SCI). One new development is the use of functional electrical stimulation (FES) device to assist locomotion. The objective of this review is to present findings from some recent studies on the effect of long-term locomotor training with FES in subjects with SCI. Promising results are shown in all outcome measures of walking, such as functional mobility, speed, spatio-temporal parameters, and the physiological cost of walking. Furthermore, the change in the walking behavior could be associated with plasticity in the CNS organization, as seen by the modification of the stretch reflex and changes in the corticospinal projection to muscles of the lower leg. In conclusion, recovery of walking is an increasing possibility for a large number of people with SCI. New modalities of treatment have become available for this population but most still need to be evaluated for their efficacy. This review has focused on FES assisted walking as a therapeutic modality in subjects with chronic SCI, but it is envisaged that the care and recovery of SCI in the early phase of recovery could also be improved.

Spinal cord injury medicine. 4. Optimal participation in life after spinal cord injury: physical, psychosocial, and economic reintegration into the environment

This learner-directed module on spinal cord injury (SCI) presents a variety of perspectives of the process of personal and environmental adaptation for reintegration. Adaptation is unique to each person and does not predictably follow stages. Models used for understanding the process include biopsychosocial, ICIDH-2 (International Classification of Functioning, Disability and Health), and sector divisions of the environment. Home modification requires home (intermediate environment) evaluation and sociospatial behavioral mapping for planning and appropriation of remodeling in proportion to functional need and use. Options for access to the natural environment include specialized wheelchairs, climbing rigging, kayaks, and sail boats. Sports participation with adaptations is expanding and includes a larger variety of organizations and leagues. Economic needs are effectively anticipated with development of a life care plan. Procreative options to overcome infertility after SCI include vibratory stimulation for ejaculation, intravaginal insemination, intrauterine insemination, in vitro fertilization, and intracytoplasmic sperm injection. Approaches to requests for withdrawal of life-sustaining care include depression screening, pain evaluation, and assistance in accomplishment of person centered goals. Overall, community reintegration after SCI is continually improving because of better acceptance, accessibility, and technology for building adaptations.

OVERALL ARTICLE OBJECTIVES

(a) To review models and theories of medical intervention and disablement and (b) to demonstrate their application in rehabilitation practice by designing unique treatment plans that meet patient person-centered goals.

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.

Arterial properties of the carotid and femoral artery in endurance-trained and paraplegic subjects

In humans, the relationships of blood flow changes to structure, function, and shear rate of conducting arteries have not been thoroughly examined. Therefore, the purpose of this study was to investigate these parameters of the elastic-type, common carotid artery (CCA) and the muscular-type, common femoral artery (CFA) in long-term highly active and extremely inactive individuals, assuming that the impact of activity-induced blood flow changes on conduit arteries, if any, should be seen in these subjects. We examined 21 highly endurance-trained athletes (A), 10 paraplegic subjects (P), and 20 sedentary subjects (S) by means of noninvasive ultrasound. As a result, the CFA diameter and compliance were highest in A (9.7+/-0.81 mm; 1.84 +/-0.54 mm(2)/kPa) and lowest in P (5.9+/-0.7 mm; 0.54+/-0.27 mm(2)/kPa) compared with S (8.3+/-1.0 mm; 0.92+/-0.48 mm(2)/kPa) with P <0.01 among the groups. Both parameters correlated with each other (r = 0.62; P<0.01). Compared with A (378+/-84 s(-1); 37+/-15 s(-1)) and S (356+/-113 s(-1); 36+/-20 s(-1)), the peak and mean shear rates of the CFA were almost or more than doubled in P (588+/-120 s(-1); 89+/-26 s(-1)). In the CCA, only the compliance and peak shear rate showed significant differences among the groups (A: 1.28+/-0.47 mm(2)/kPa, 660+/-138 s(-1); S: 1.04+/-0.27 mm(2)/kPa, 588+/-109 s(-1); P: 0.65+/- 0.22 mm(2)/kPa, 490+/-149 s(-1); P<0.05). In conclusion, the results suggest a structural and functional adaptation in the CFA and a predominantly functional adaptation of the arterial wall properties to differences in the physical activity level and associated exercise-induced blood flow changes in the CCA. The results for humans confirm those from animal experiments. Similar shear rate values of S and P in the CFA support the hypothesis of constant shear stress regulation due to local blood flow changes in humans. On the other hand, the increased shear rate in the CFA in P indicates an at least partially nonphysiological response of the arterial wall in long-term chronic sympathectomy due to a change in local blood flow.

Catecholamine response to exercise in individuals with different levels of paraplegia

The purpose of this study was to investigate the effect of the level of injury on the serum level of norepinephrine (Nor) and epinephrine (Epi) at rest and after maximal exercise in individuals with paraplegia. Twenty-six male spinal cord-injured subjects with complete paraplegia for at least 9 months were divided into two groups of 13 subjects each according to the level of injury, i.e., T1-T6 and T7-T12. Serum Nor and Epi concentrations were measured by HPLC-ECD, at rest (PRE) and immediately after a maximal ergospirometric test (POST). Statistical analysis was performed using parametric and non-parametric tests. Maximal heart rate, peak oxygen uptake, and PRE and POST Nor were lower in the T1-T6 than in the T7-T12 group (166 +/- 28 vs 188 +/- 10 bpm; 18.0 +/- 6.0 vs 25.8 +/- 4.1 ml kg(-1) min(-1); 0.54 +/- 0.26 vs 0.99 +/- 0.47 nM; 1.48 +/- 1. 65 vs 3.07 +/- 1.44 nM). Both groups presented a significant increase in Nor level after exercise, while only the T7-T12 group showed a significant increase in Epi after exercise (T1-T6: 0.98 +/- 0.72 vs 1.11 +/- 1.19 nM; T7-T12: 1.24 +/- 1.02 vs 1.89 +/- 1.57 nM). These data show that individuals with paraplegia above T6 have an attentuated catecholamine release at rest and response to exercise as compared to subjects with injuries below T6, which might prevent a better exercise performance in the former group.