Temperature responses to electrically induced cycling in spinal cord injured persons

PURPOSE

The purpose of the study was to investigate the core temperature responses to the induction of electrical exercise and to clarify whether an increase in temperature could be responsible for some of the observed reactions to acute and repeated exposure to electrical muscle stimulation.

METHODS

The paralyzed thigh and gluteal muscles were stimulated electrically with surface electrodes in seven persons with transection of the spinal cord. By this means, they were able to pedal a lower extremity ergometer at 50 revolutions per minute for 30 min. Skin surface, esophageal (Tes), rectal (Tre), and muscle temperature in m. quadriceps were measured with thermocouples.

RESULTS

The average rate of oxygen consumption was 0.91 +/- 0.16 L.min-1, and the heart rate after 20 min was 123 +/- 9 bpm during the electrically induced exercise. The involuntary, induced exercise led to increases in core temperature, whereas skin surface temperature was the same before and after exercise. Average Tes and Tre both rose 0.7 degrees C from, respectively, 36.6 +/- 0.2 and 36.9 +/- 0.1 degrees C, and muscle temperature increased even more: 2.9 degrees C from 33.9 +/- 0.3 degrees C.

CONCLUSION

It is suggested that these increased temperatures may act as stimuli, directly or, through resulting release of humoral factors, and elicit the changes in heart rate, as well as the previously observed adaptive changes after electrically induced exercise, e.g., in muscle fiber size, and capillarization.

Leg uptake of calcitonin gene-related peptide during exercise in spinal cord injured humans

Exercise-induced increases in cardiac output (CO) and oxygen uptake (VO2) are tightly coupled, as also in absence of central motor activity and neural feedback from skeletal muscle. Neuromodulators of vascular tone and cardiac function - such as calcitonin gene related peptide (CGRP) - may be of importance. Spinal cord injured individuals (six tetraplegic and four paraplegic) performed electrically induced cycling (FES) with their paralyzed lower limbs for 29 +/- 2 min to fatigue. Voluntary cycling performed both at VO2 similar to FES and at maximal exercise in six healthy subjects served as control. In healthy subjects, CGRP in plasma increased only during maximal exercise (33.8 +/- 3.1 pmol l(-1) (rest) to 39.5 +/- 4.3 (14%, P<0.05)) with a mean extraction over the working leg of 10% (P<0.05). Spinal cord injured individuals had more pronounced increase in plasma CGRP (33.2 +/- 3.8 to 46.9 +/- 3.6 pmol l-1, P<0.05), and paraplegic and tetraplegic individuals increased in average by 23% and 52%, respectively, with a 10% leg extraction in both groups (P<0.05). The exercise induced increase in leg blood flow was 10-12 fold in both spinal cord injured and controls at similar VO2 (P<0.05), whereas CO increased more in the controls than in spinal man. Heart rate (HR) increased more in paraplegic subjects (67 +/- 7 to 132 +/- 15 bpm) compared with controls and tetraplegics (P<0.05). Mean arterial pressure (MAP) was unchanged during submaximal exercise and increased during maximal exercise in healthy subjects, but decreased during the last 15 min of exercise in the tetraplegics. It is concluded that plasma CGRP increases during exercise, and that it is taken up by contracting skeletal muscle. The study did not allow for a demonstration of the origin of the CGRP, but its release does not require activation of motor centres. Finally, the more marked increase in plasma CGRP and the decrease in blood pressure during exercise in tetraplegic humans may indicate a role of CGRP in regulation of vascular tone during exercise.

Marathon running transiently increases c-Jun NH2-terminal kinase and p38 activities in human skeletal muscle

We examined the pattern of activation and deactivation of the stress-activated protein kinase signalling molecules c-Jun NH2-terminal kinase (JNK) and p38 kinase in skeletal muscle in response to prolonged strenuous running exercise in human subjects. Male subjects (n = 14; age 32 +/- 2 years; VO2,max 60 +/- 2 ml kg-1 min-1) completed a 42.2 km marathon (mean race time 3 h 35 min). Muscle biopsies were obtained 10 days prior to the marathon, immediately following the race, and 1, 3 and 5 days after the race. The activation of JNK and p38, including both p38alpha and p38gamma, was measured with immune complex assays. The phosphorylation state of p38 (alpha and gamma) and the upstream regulators of JNK and p38, mitogen-activated protein kinase kinase 4 (MKK4) and mitogen-activated protein kinase kinase 6 (MKK6), were assessed using phosphospecific antibodies. JNK activity increased 7-fold over basal level immediately post-exercise, but decreased back to basal levels 1, 3 and 5 days after the exercise. p38gamma phosphorylation (4-fold) and activity (1.5-fold) increased immediately post-exercise and returned to basal levels at 1, 3 and 5 days following exercise. In contrast, p38alpha phosphorylation and activity did not change over the time course studied. MKK4 and MKK6 phosphorylation increased and decreased in a trend similar to that observed with JNK activity and p38gamma phosphorylation. Prolonged running exercise did not affect JNK, p38alpha, or p38gamma protein expression in the days following the race. This study demonstrates that both JNK and p38 intracellular signalling cascades are robustly, yet transiently increased following prolonged running exercise. The differential activation of the p38 isoforms with exercise in human skeletal muscle indicates that these proteins may have distinct functions in vivo.

[Electric stimulation in muscle training of the lower extremities in persons with spinal cord injuries]

Spinal cord injured persons have limited possibilities to perform physical training. By use of computerized, feed-back controlled electrical stimulation of the gluteal, the hamstrings and the quadriceps muscles cycle ergometry can be performed by the spinal cord injured individual. The cardiovascular demands of this training is higher than with voluntary upper body training using the intact innervated muscles. The inactivity related conditions caused by the spinal cord injury are reversed in part by regular electrically stimulated training. An increase is seen in maximal oxygen consumption, in the insulin stimulated glucose uptake and in the muscular mass and bone mineral content of the lower extremities. Electrically induced cycle ergometry is thoroughly investigated, relatively safe, but time consuming. As this training in addition results in the same well being as seen by training in able bodied individuals it can be recommended for motivated patients.

Type IV collagen and its degradation in paralyzed human muscle: effect of functional electrical stimulation

The purpose of this study was to evaluate the effects of spinal cord injury (SCI) and functional electrical stimulation (FES) of paralyzed muscles on type IV collagen content and proteins involving its degradation, which is initiated by matrix metalloproteinase (MMP)-2 and -9 and regulated by their tissue inhibitors (TIMPs)-2 and -1. Ten SCI subjects participated in an 18-month program of functional electrical stimulation (FES) of their leg muscles. Needle biopsies were taken from the vastus lateralis muscle before and at various times during the training period, and from able-bodied controls. Type IV collagen concentration was unaltered. ProMMP-2 level of SCI subjects before the training period tended to be higher than able-bodied controls and was significantly above the control level after FES. MMP-9 concentration was unchanged. The results suggest accelerated type IV collagen turnover in skeletal muscle of SCI individuals especially after FES as a part of adaptive process of the muscle.

Evidence for a role of FGF-2 and FGF receptors in the proliferation of non-small cell lung cancer cells

Basic fibroblast growth factor (FGF-2) has been implicated in the progression of human tumours via both autocrine and paracrine (angiogenic) activities. We investigated the expression of FGF-2 and FGF receptors (FGFR-1 to -4) in NSCLC cell lines (N = 16), NSCLC surgical specimens (N = 21) and 2 control cell lines. Our data show that almost all NSCLC cells produce elevated levels of FGF-2 and FGFR in vitro and in vivo. FGF-2 expression did correlate with a short doubling time as well as with potent anchorage-independent growth of NSCLC cell lines. In contrast with control cells, NSCLC cells did not secrete considerable amounts of FGF-2 into the extracellular space. Expression levels of FGFR-1 and -2 in NSCLC cell lines correlated with FGF-2 production. FGFR were located at the plasma membranes in some low FGF-2-producing NSCLC and control cell lines. These cells were sensitive to the proliferative effect of recombinant FGF-2 (rFGF-2). In NSCLC cell lines with an enhanced FGF-2 production, representing the majority studied, FGFR localisation was predominantly intracellular. These cells were insensitive to both the proliferative effect of rFGF-2 and growth inhibition by FGF-2-neutralising antibodies. In contrast, several agents antagonised FGF-2 intracellularly impaired growth of almost all NSCLC cell lines. Our data suggest a role of FGF-2 and FGFR in the growth stimulation of NSCLC cells possibly via an intracrine mechanism.

In vitro cell culture systems as the basis for an extracorporeal blood purification strategy in multiorgan failure treatment

Multiorgan failure (MOF) based on septic processes is very common but prognostically an extremely severe disease that has to be treated exclusively under intensive care conditions. Extracorporeal blood purification (ECBP) using specific and efficient systems such as the microspheres based detoxification system (MDS) (Artif Organs 1996;20:420) could improve significantly the situation of MOF in terms of the efficient removal of endotoxins as well as key mediators such as tumor necrosis factor alpha (TNF alpha). The purpose of the study was to test the effectiveness of endotoxin and cytokine removal to blunt cellular response. In terms of the in vitro principle methodology, isolated peripheral blood mononuclear cells (PBMC) were incubated with endotoxins and a selective endotoxin adsorbent, which was added at various times (immediately or 30, 60, 120, 240, or 360 min) after the onset of incubation. TNF alpha release of monocytes was measured following a standard procedure after 20 h. Human TNF alpha was incubated with cultured human endothelial cells with and without a specific TNF alpha adsorbent (polyclonal antibodies coated on polystyrene particles). The results showed that after the initial addition of endotoxins, the activation of monocytes can be stopped within 120 min by addition of endotoxin adsorbents. In addition, specific TNF alpha adsorbents are able to prevent intercellular adhesion molecule 1 (ICAM-1) expression of endothelial cells, therefore avoiding activation of endothelial cells. In conclusion, cell culture models are suitable to simulate cell interaction in MOF. Specific adsorbents are able to reduce or block pathophysiologically relevant cell interactions, and the time frame for effective ECBP seems to be very short, and therefore, efficiency must be high.

Improved physical performance after orthotopic liver transplantation

Orthotopic liver transplantation (OLT) has become a frequently used treatment for end-stage liver disease and acute liver failure, and liver function is markedly improved after transplantation. However, no studies have investigated the development in physical capacity after OLT. On this basis, the aim of the present study is to study the influence of OLT on physical fitness during the first postoperative year. Twenty-three men with a mean age of 45.1 years (range, 24 to 62 years) and 15 women with a mean age of 44.6 years (range, 21 to 62 years) were included in the study. Preoperative maximal oxygen uptake (VO2max) during graded ergometer bicycling, isokinetic knee extension/flexion moments, and functional performance (i.e., 6-minute walking distance and standardized transfers and squats) was measured. Preoperative fitness and strength was 40% to 50% less than expected in the age-matched general population. Post-OLT, all patients underwent a supervised exercise program for 8 to 24 weeks. Follow-up data showed a significant increase in all tested physical performance parameters after OLT. Six months post-OLT, VO2max had increased 43%; knee strength, 60% to 100%; and functional performance, 22% to 27%. One year postsurgery, general health was improved and perceived as excellent or good in all patients. All patients were independent in activities of daily living, and the level of physical activity increased after OLT. No further improvement in either physical performance parameters or self-assessed parameters was seen beyond 6 months after OLT. In conclusion, these findings indicate that OLT combined with a supervised post-OLT exercise program improves physical fitness, muscle strength, and functional performance in individuals with chronic liver disease.

No effect of antioxidant supplementation in triathletes on maximal oxygen uptake, 31P-NMRS detected muscle energy metabolism and muscle fatigue

A double-blind placebo-controlled cross-over trial was undertaken to evaluate the effect of antioxidant supplementation on maximal oxygen uptake during bicycling, 31-phosphorus nuclear magnetic response spectroscopy (31P-NMRS) detected muscle energy metabolism during plantar flexion and muscle fatigue evaluated by 1-s electrical stimulation at low (10 Hz) and high (50 Hz) frequency. Seven male triathletes received daily oral antioxidant supplementation in capsule form including 100 mg coenzyme Q10 (CoQ10), 600 mg ascorbic acid and 270 mg alpha-tocopherol or placebo over a 6-week interval. Serum concentration of CoQ10 was significantly higher in the antioxidant phase (1.80+/-1 microg x ml(-1), mean +/- SD) than control (0.9+/-0.21 microg ml(-1)) or placebo phase (0.9+/-0.3 microg x ml(-1)) (P<0.01). Maximal oxygen uptake was 63.8+/-3.0 ml x min(-1) x kg(-1) in the control phase, and did not change significantly in the antioxidant (67.6+/-10.8 ml x min(-1) x kg(-1)) or the placebo phase (61.9+/-4.5 ml x min(-1) x kg(-1)). The combined 31P-NMRS/low frequency fatigue test (plantar flexion of the foot) did not show differences in the gastrocnemius muscle pH (6.77+/-0.14), phosphocreatine reduction at the end of exercise (23+/-14% of rest) and half-time for recovery of phosphocreatine (33+/-12 sec) between the placebo and the antioxidant trial. No difference in muscle fatigue at 10 Hz electrical stimulation was found between the three phases. In conclusion, the results demonstrate no effect of antioxidative vitamin supplementation on maximal oxygen uptake, muscle energy metabolism or muscle fatigue in triathletes.

Heart rate during exercise with leg vascular occlusion in spinal cord-injured humans

Feed-forward and feedback mechanisms are both important for control of the heart rate response to muscular exercise, but their origin and relative importance remain inadequately understood. To evaluate whether humoral mechanisms are of importance, the heart rate response to electrically induced cycling was studied in participants with spinal cord injury (SCI) and compared with that elicited during volitional cycling in able-bodied persons (C). During voluntary exercise at an oxygen uptake of approximately 1 l/min, heart rate increased from 66 +/- 4 to 86 +/- 4 (SE) beats/min in seven C, and during electrically induced exercise at a similar oxygen uptake in SCI it increased from 73 +/- 3 to 110 +/- 8 beats/min. In contrast, blood pressure increased only in C (from 88 +/- 3 to 99 +/- 4 mmHg), confirming that, during exercise, blood pressure control is dominated by peripheral neural feedback mechanisms. With vascular occlusion of the legs, the exercise-induced increase in heart rate was reduced or even eliminated in the electrically stimulated SCI. For C, heart rate tended to be lower than during exercise with free circulation to the legs. Release of the cuff elevated heart rate only in SCI. These data suggest that humoral feedback is of importance for the heart rate response to exercise and especially so when influence from the central nervous system and peripheral neural feedback from the working muscles are impaired or eliminated during electrically induced exercise in individuals with SCI.

The natural killer cell response to exercise in spinal cord injured individuals

In order to evaluate exercise-induced changes in natural killer (NK) and other immunocompetent cells in spinal cord injured individuals, immunological competent blood cells and stress hormones were followed in five paraplegic and six quadriplegic subjects in relation to 30 min electrically stimulated cycling exercise. The leukocyte and lymphocyte concentrations increased during exercise. In the recovery period, the concentration of neutrophils increased, whereas the lymphocytes decreased. The percentage and concentration of NK cells increased during exercise in the paraplegic group and returned to pre-exercise level 2 h after, whereas no changes were seen in these measures for the quadriplegic group. No changes in activated CD38+ NK cells appeared. Unstimulated and interferon-alpha or interleukin-2 stimulated NK cell activity increased during exercise and returned to pre-exercise level 2 h after with no distinction between paraplegics and quadriplegics. The concentrations of plasma growth hormone and catecholamines increased during exercise, with the rise in epinephrine being more pronounced in paraplegic than in quadriplegic subjects, indicating a difference between the groups in sympathetic nervous system integrity. The sympathoadrenal activity is concluded to be responsible for recruitment of NK cells to the blood during exercise.

Caffeine ingestion and metabolic responses of tetraplegic humans during electrical cycling

Normally, caffeine ingestion results in a wide spectrum of neural and hormonal responses, making it difficult to evaluate which are critical regulatory factors. We examined the responses to caffeine (6 mg/kg) ingestion in a group of spinal cord-injured subjects [7 tetraplegic (C5-7) and 2 paraplegic (T4) subjects] at rest and during functional electrical stimulation of their paralyzed limbs to the point of fatigue. Plasma insulin did not change, caffeine had no effect on plasma epinephrine, and there was a slight increase (P < 0. 05) in norepinephrine after 15 min of exercise. Nevertheless, serum free fatty acids were increased (P < 0.05) after caffeine ingestion after 60 min of rest and throughout the first 15 min of exercise, but the respiratory exchange ratio was not affected. The exercise time was increased (P < 0.05) by 6% or 1.26 +/- 0.57 min. These data suggest that caffeine had direct effects on both the adipose tissue and the active muscle. It is proposed that the ergogenic action of caffeine is occurring, at least in part, by a direct action of the drug on muscle.

Bone fracture during electrical stimulation of the quadriceps in a spinal cord injured subject

We report a fracture through the lateral femoral condyle of a paraplegic subject caused by electrical stimulation (ES). The subject was a 50-year-old man who 4 years earlier had sustained a complete spinal cord injury (SCI) at level T6. The fracture occurred during ES-induced measurement of maximal isometric torque of the quadriceps with the knee flexed at an angle of 90 degrees. ES was delivered through surface electrodes with biphasic square wave pulses from a constant current stimulator. The torque was calculated to be 93Nm, corresponding to 20.8kg at the ankle. The regional bone mineral density of the entire lower extremities was .83g/cm2, corresponding to 60% of sex- and age-matched able-bodied reference values. Several factors are suspected to have contributed to the fracture: maximal ES in combination with a muscle spasm, severe osteoporosis, increased muscular strength induced by regular ES cycling (twice a week), and testing position with the knee locked in 90 degrees flexion. The risk of fracture as well as various precautions are discussed and should be taken into consideration in future studies.

Lactate/H+ transport in skeletal muscle from spinal-cord-injured patients

In order to evaluate the effect of prolonged muscle inactivity on sarcolemmal lactate/H+ transport in humans, the lactate/H+ transport capacity was determined in the thigh muscle of spinal-cord-injured (SCI) individuals. The lactate transport rate was measured in sarcolemmal giant vesicles produced by collagenase treatment of muscle biopsies obtained from the vastus lateralis muscle. Six SCI subjects with total loss of motor and sensory functions of their lower limbs participated in the study. The duration of the injury ranged from 2 to 15 years. The total lactate transport rate in the muscle of SCI patients was 46.5 +/- 2.6 pmol.cm-2.s-1 (mean +/- SEM), which corresponds to a 17% lower (P < 0.05) transport rate than that found in healthy, untrained subjects. The estimated carrier-mediated lactate/H+ transport capacity was approximately 26% lower in the SCI patients than in healthy, untrained subjects. The observed muscle lactate/H+ transport capacity of SCI individuals is in accordance with a positive correlation between the capacity of the lactate/H+ transporters and the percentage occurrence of slow-twitch fibres in a muscle, although there seems to be a wide range of transport capacities within each fibre type. The present results show that the sarcolemmal lactate/H+ transport capacity is lower in SCI individuals than in normally physically active subjects, which indicates that prolonged muscle inactivity reduces the lactate/H+ transport capacity of human muscle.

In vivo cell-mediated immunity and vaccination response following prolonged, intense exercise

Epidemiological and experimental studies have shown increased frequency and severity of infections after intense, long-term exercise. This study examines whether an in vivo impairment of the cell-mediated immunity and antibody production can be demonstrated after intense, long-term exercise. Twenty-two male triathletes performed one-half an ironman (group A). Vaccinations with tetanus and diphtheritis toxoid and purified pneumococcal polysaccharide were given after the exercise. Furthermore, a skin test with seven different antigens was applied on the forearm. Antibody titers were measured before and 2 wk after the exercise. The skin test was read 48 h after the application. Eleven non-exercising triathletes (group B) and 22 moderately trained men (group C) were used as control groups. Group A revealed a significantly lower skin test response to the tetanus antigen than both groups B and C. In group A, a smaller cumulative response (sum of the diameters of indurations and number of positive skin test spots) was found than in both groups B and C. No differences in antibody titers were found among the three groups. Thus, the in vivo cell-mediated immunity was impaired in the first days after prolonged, high intensity exercise, whereas there was no impairment of the in vivo antibody production measured 2 wk after vaccination.

Increased bone mineral density after prolonged electrically induced cycle training of paralyzed limbs in spinal cord injured man

Spinal cord injured (SCI) individuals have a substantial loss of bone mass in the lower limbs, equaling approximately 50% of normal values in the proximal tibia, and this has been associated with a high incidence of low impact fractures. To evaluate if this inactivity-associated condition in the SCI population can be reversed with prolonged physical training, ten SCI individuals [ages 35.3 +/- 2.3 years (mean +/- standard error [SE]); post injury time: 12.5 +/- 2.7 years, range 2-24 years; level of lesion: C6-Th4; weight: 78 +/- 3.8 kg] performed 12 months of Functional Electrical Stimulated (FES) upright cycling for 30 min per day, 3 days per week, followed by six months with only one weekly training session. Bone mineral density (BMD) was determined before training and 12 and 18 months later. BMD was measured in the lumbar spine, the femoral neck, and the proximal tibia by dual energy absorptiometry (DEXA, Nordland XR 26 MK1). Before training, BMD was in the proximal tibia (52%), as well as in the femoral neck, lower in SCI subjects than in controls of same age (P < 0.05). BMD of the lumbar spine did not differ between groups (P > 0.05). After 12 months of training, the BMD of the proximal tibia had increased 10%, from 0.49 +/- 0.04 to 0. 54 +/- 0.04 g/cm2 (P < 0.05). After a further 6 months with reduced training, the BMD in the proximal tibia no longer differed from the BMD before training (P > 0.05). No changes were observed in the lumbar spine or in the femoral neck in response to FES cycle training. It is concluded that in SCI, the loss of bone mass in the proximal tibia can be partially reversed by regular long-term FES cycle exercise. However, one exercise session per week is insufficient to maintain this increase.

Long-term adaptation to electrically induced cycle training in severe spinal cord injured individuals

Spinal cord injured (SCI) individuals most often contract their injury at a young age and are deemed to a life of more or less physical inactivity. In addition to the primary implications of the SCI, severe SCI individuals are stigmatized by conditions related to their physically inactive lifestyle. It is unknown if these inactivity related conditions are potentially reversible and the aim of the present study was, therefore, to examine the effect of exercise on SCI individuals. Ten such individuals (six with tetraplegia and four with paraplegia; age 27-45 years; time since injury 3-23 years) were exercise trained for 1 year using an electrically induced computerized feedback controlled cycle ergometer. They trained for up to three times a week (mean 2.3 times), 30 min on each occasion. The gluteal, hamstring and quadriceps muscles were stimulated via electrodes placed on the skin over their motor points. During the first training bouts, a substantial variation in performance was seen between the subjects. A majority of them were capable of performing 30 min of exercise in the first bout; however, two individuals were only able to perform a few minutes of exercise. After training for 1 year all of the subjects were able to perform 30 min of continuous training and the work output had increased from 4 +/- 1 (mean +/- SE) to 17 +/- 2 Kilo Joules per training bout (P < 0.05). The maximal oxygen uptake during electrically induced exercise increased from 1.20 +/- 0.08 litres per minute measured after a few weeks habituation to the exercise to 1.43 +/- 0.09 litres per minute after training for 1 year (P < 0.05). Magnetic resonance cross sectional images of the thigh were performed to estimate muscle mass and an increase of 12% (mean, P < 0.05) was seen in response to 1 year of training. In biopsies taken before exercise various degrees of atrophy were observed in the individual muscle fibres, a phenomenon that was partially normalized in all subjects after training. The fibre type distribution in skeletal muscles is known to shift towards type IIB fibres (fast twitch, fast fatiguable, glycolytic fibres) within the first 2 years after the spinal cord injury. The muscle in the present investigation contained of 63% myosin heavy chain (MHC) isoform IIB, 33% MHC isoform IIA (fast twitch, fatigue resistant) and less than 5% MHC isoform I (slow twitch) before training. A shift towards more fatigue resistant contractile proteins was found after 1 year of training. The percentage of MHC isoform IIA increased to 61% of all contractile protein and a corresponding decrease to 32% was seen in the fast fatiguable MHC isoform IIB, whereas MHC isoform I only comprised 7% of the total amount of MHC. This shift was accompanied by a doubling of the enzymatic activity of citrate synthase, as an indicator of mitochondrial oxidative capacity. It is concluded that inactivity-associated changes in exercise performance capacity and skeletal muscle occurring in SCI individuals after injury are reversible, even up to over 20 years after the injury. It follows that electrically induced exercise training of the paralysed limbs is an effective rehabilitation tool that should be offered to SCI individuals in the future.

Viscoelastic stress relaxation during static stretch in human skeletal muscle in the absence of EMG activity

The present study sought to investigate the role of EMG activity during passive static stretch. EMG and passive resistance were measured during static stretching of human skeletal muscle in eight neurologically intact control subjects and six spinal cord-injured (SCI) subjects with complete motor loss. Resistance to stretch offered by the hamstring muscles during passive knee extension was defined as passive torque (Nm). The knee was passively extended at 5 degrees/s to a predetermined final position, where it remained stationary for 90 s (static phase) while force and integrated EMG of the hamstring muscle were recorded. EMG was sampled for frequency domain analysis in a second stretch maneuver in five control and three SCI subjects. There was a decline in passive torque in the 90-s static phase for both control and SCI subjects, P < 0.05. Although peak passive torque was greater in control subjects, P < 0.05, there was no difference in time-dependent passive torque response between control (33%) and SCI (38%) subjects. Initial and final 5-s IEMG ranged from 1.8 to 3.4 microV.s and did not change during a stretch or differ between control and SCI subjects. Frequency domain analysis yielded similar results in both groups, with an equal energy distribution in all harmonics, indicative of 'white noise'. The present data demonstrate that no measurable EMG activity was detected in either group during the static stretch maneuver. Therefore, the decline in resistance to static stretch was a viscoelastic stress relaxation response.

Assessing individual differences in constructive versus destructive responses to anger across the lifespan

Scenario-based, self-report measures were developed to assess how people characteristically experience and manage anger from middle childhood through adulthood. The Anger Response Inventories (ARIs) for children, adolescents, and adults each assess (a) anger arousal, (b) intentions, (c) cognitive and behavioral responses, and (d) Long-term consequences. Several independent studies provide support for the reliability and validity of the ARIs. Theoretically consistent patterns of correlations were observed with (a) global self-report measures of hostility, aggression, and anger-management strategies (adult version); (b) teacher reports of behavioral and emotional adjustment (child and adolescent versions); and (c) self- and family-member reports of behaviors on specific anger episodes (adolescent and adult versions). Findings from additional personality and developmental studies are summarized, further supporting construct validity.

Regulation of glucose turnover and hormonal responses during electrical cycling in tetraplegic humans

To examine the importance of blood-borne vs. neural mechanisms for hormonal responses and substrate mobilization during exercise, six spinal cord-injured tetraplegic (C5-T1) males (mean age: 35 yr, range: 24-55 yr) were recruited to perform involuntary, electrically induced cycling [functional electrical stimulation (FES)] to fatigue for 24.6 +/- 2.3 min (mean and SE), and heart rate rose from 67 +/- 7 (rest) to 107 +/- 5 (exercise) beats/min. Voluntary arm cranking in tetraplegics (ARM) and voluntary leg cycling in six matched, long-term immobilized (2-12 mo) males (Vol) served as control experiments. In FES, peripheral glucose uptake increased [12.4 +/- 1.1 (rest) to 19.5 +/- 4.3 (exercise) mumol.min-1.kg-1; P < 0.05], whereas hepatic glucose production did not change from basal values [12.4 +/- 1.4 (rest) vs. 13.0 +/- 3.4 (exercise) mumol.min-1.kg-1]. Accordingly, plasma glucose decreased [from 5.4 +/- 0.3 (rest) to 4.7 +/- 0.3 (exercise) mmol/l; P < 0.05]. Plasma glucose did not change in response to ARM or Vol. Plasma free fatty acids and beta-hydroxybutyrate decreased only in FES experiments (P < 0.05). During FES, increases in growth hormone (GH) and epinephrine and decreases in insulin concentrations were abolished. Although subnormal throughout the exercise period, norepinephrine concentrations increased during FES, and responses of heart rate, adrenocorticotropic hormone, beta-endorphin, renin, lactate, and potassium were marked. In conclusion, during exercise, activity in motor centers and afferent muscle nerves is important for normal responses of GH, catecholamines, insulin, glucose production, and lipolysis. Humoral feedback and spinal or simple autonomic nervous reflex mechanisms are not sufficient. However, such mechanisms are involved in redundant control of heart rate and neuroendocrine activity in exercise.

Hormonal and metabolic responses to electrically induced cycling during epidural anesthesia in humans

Hormonal and metabolic responses to electrically induced dynamic exercise were investigated in eight healthy young men with afferent neural influence from the legs blocked by epidural anesthesia (25 ml of 2% lidocaine) at L3-L4. This caused cutaneous sensory anesthesia below T8-T9 and complete paralysis of the legs. Cycling increased oxygen uptake to 1.90 +/- 0.13 (SE) l/min, and fatigue developed after 22.7 +/- 2.7 min. Compared with voluntary exercise at the same oxygen uptake and heart rate, concentrations of blood and muscle lactate (musculus vastus lateralis) as well as plasma potassium increased more while muscle glycogen decreased more during electrically induced exercise. Hepatic glucose production always rose during exercise. However, during involuntary exercise with sensory blockade, it did not match the rise in peripheral glucose uptake and plasma glucose decreased (P < 0.05). Plasma glycerol increased less in electrically induced vs. voluntary exercise, and free fatty acids and beta-hydroxybutyrate decreased only during electrically induced exercise. Epinephrine, growth hormone, adrenocorticotropic hormone, and cortisol levels were higher during involuntary vs. voluntary exercise (P < 0.05). In conclusion, neural and humoral mechanisms exert redundant control with regard to responses of catecholamines and pituitary hormones (growth hormone and adrenocorticotropic hormone). In contrast, neural input from motor centers and feedback from working muscle are important for glucose production and lipolysis during exercise in humans. Humoral feedback is apparently not sufficient to trigger normal mobilization of extramuscular fuel stores.