Muscle oxygenation during incremental arm and leg exercise in men and women

The purpose of this study was to compare the rates of muscle deoxygenation in the exercising muscles during incremental arm cranking and leg cycling exercise in healthy men and women. Fifteen men and 10 women completed arm cranking and leg cycling tests to exhaustion in separate sessions in a counterbalanced order. Cardiorespiratory measurements were monitored using an automated metabolic cart interfaced with an electrocardiogram. Tissue absorbency was recorded continuously at 760 nm and 850 nm during incremental exercise and 6 min of recovery, with a near infrared spectrometer interfaced with a computer. Muscle oxygenation was calculated from the tissue absorbency measurements at 30%, 45%, 60%, 75% and 90% of peak oxygen uptake (VO2) during each exercise mode and is expressed as a percentage of the maximal range observed during exercise and recovery (%Mox). Exponential regression analysis indicated significant inverse relationships (P < 0.01) between %Mox and absolute VO2 during arm cranking and leg cycling in men (multiple R = -0.96 and -0.99, respectively) and women (R = -0.94 and -0.99, respectively). No significant interaction was observed for the %Mox between the two exercise modes and between the two genders. The rate of muscle deoxygenation per litre of VO2 was 31.1% and 26.4% during arm cranking and leg cycling, respectively, in men, and 26.3% and 37.4% respectively, in women. It was concluded that the rate of decline in %Mox for a given increase in VO2 between 30% and 90% of the peak VO2 was independent of exercise mode and gender.     

Metabolic efficiency during arm and leg exercise at the same relative intensities

This study was conducted to compare gross efficiency (GE), net efficiency (NE), work efficiency (WE), and delta efficiency (DE) between arm crank and cycle exercise at the same relative intensities. Eight college-aged males underwent two experimental trials presented in a randomized counterbalanced order. During each trial subjects performed three intermittent 7-min exercise bouts separated by 10-min rest intervals on an arm or semirecumbent leg ergometer. The power outputs for the three bouts of arm crank or cycle exercise corresponded to 50, 60, and 70% of the mode-specific VO2peak. GE, NE, and WE were determined as the ratio of Kcal.min-1 equivalent of power output to Kcal.min-1 of total energy expended, energy expended above rest and energy expended above unloaded exercise, respectively. DE was determined as the ratio of the increment of Kcal.min-1 of power output above the previous lower intensity to the increment of kcal.min-1 of total energy expended above the previous lower intensity. GE and NE did not differ between arm crank and cycle exercises. However, WE was lower (P < 0.05) during arm crank than cycle exercise at 50, 60, and 70% VO2peak. DE was also lower (P < 0.05) during arm crank than cycle exercise at delta 50-60 and at delta 60-70% VO2peak. It is concluded metabolic efficiency as determined by work and delta efficiency indices was lower during arm crank compared with cycle exercise at the same relative intensities. These findings add to the understanding of the difference in metabolic efficiency between upper and lower body exercise.     

Maximal oxygen uptake during exercise with various combinations of arm and leg work

Oxygen uptake (VO2) was determined in 10 males during the following types of maximal exercise (work time: about 5 min): uphill running, bicycling, arm work (cranking), and combined arm work and bicycling (A + L). The A + L exercise was performed in four different ways, the arms doing 10%, 20%, 30%, or 40% of the same total rate of work; and also with the maximal bicycle work load plus either maximal or submaximal arm work. VO2 was the same in running as in all types of A + L exercise, except when the arm work load was 10% and 40% of the total rate of work, where VO2 was 2.5% (P less than 0.05) and 9.4% (P less than 0.001) lower, respectively. Bicycle VO2 was lower than VO2 in running but equal to A + L VO2 when arm work intensity was 40% of the total rate of work. It is concluded that VO2 during maximal exercise a) to a certain extent depends on the exercising muscle mass, b) is lower than the oxygen-consuming potential of the muscles involved in A + L exercise, and c) in A + L exercise is influenced by the ratio of arm work to total rate of work and the subject's fitness for arm work and bicycling.     

Effects of prior arm exercise on pulmonary gas exchange kinetics during high-intensity leg exercise in humans

The activation of MAPKs is controlled by the balance between MAPK kinase and MAPK phosphatase activities. The latter is mediated by a subset of phosphatases with dual specificity (VH-1 family). Here, we describe a new member of this family encoded by the puckered gene of Drosophila. Mutations in this gene lead to cytoskeletal defects that result in a failure in dorsal closure related to those associated with mutations in basket, the Drosophila JNK homolog. We show that puckered mutations result in the hyperactivation of DJNK, and that overexpression of puc mimics basket mutant phenotypes. We also show that puckered expression is itself a consequence of the activity of the JNK pathway and that during dorsal closure, JNK signaling has a dual role: to activate an effector, encoded by decapentaplegic, and an element of negative feedback regulation encoded by puckered.     

Time-of-day effects in maximal anaerobic leg exercise

The pathogenesis of AIDS is a complex and prolonged process that is affected by a variety of cofactors, including the abuse of both intravenous and smoked (crack) cocaine. The exact mechanisms by which cocaine facilitates this disease are yet to be proven, but likely include a combination of increased risk due to cocaine-related social behaviours, a wide-ranging capacity for cocaine to suppress the immune system, and an effect of cocaine on the infectivity and replication of HIV. While sometimes contradictory, both human and animal studies document that cocaine alters the function of natural killer (NK) cells, T cells, neutrophils and macrophages, and alters the ability of these cells to secrete immunoregulatory cytokines. In addition to these effects on the immune system, cocaine also enhances the infectivity and/or replication of HIV when tested using human cells in vitro.     

H-reflex and F-wave potentials in leg and arm muscles

The systematic analyses of secondary muscle potentials of H-reflex and F-wave type were done in multicentric study. The examinations were carried out in healthy volunteers with 9 muscles analysed on the legs and 9 on the lower arms and hands. The H-reflex potential was found regularly in thigh muscles (vastus medialis 100%, biceps femoris 97%, semitendinosus 93%). Less frequently but still with high incidence it appeared in posterior lower leg muscles (soleus 93%, caput mediale gastrocnemii 73%). In anterior tibial muscle and extensor digitorum brevis it did not appear at all. Only exceptionally it was found in short peroneal muscle (3%) and occasionally, only on proximal nerve stimulation, in flexor hallucis brevis. The similar distribution pattern was found in lower arm and hand muscles with analysis on both sides. In flexor digitorum superficialis (73-70%) and flexor carpi radialis (73-57%) the percentage of H-potential muscles was the highest, in flexor carpi ulnaris (47-40%) lesser but still remarkable. Brachioradialis (37-30%) and extensor digitorum communis (27-27%) percentage decreased further. The even more distal, pronator quadratus (21-20%) and abuctor digiti minimi (17-17%) presented as muscles with low incidence of H-reflex positivity. In extensor indicis proprius (3%) the lowest H-potential incidence was found and in opponens pollicis no H-potential at all. F-waves if evaluated as "F-frequency" follow the similar distribution pattern. The lowest "F-frequency" was found on the legs in anterior tibial, short peroneal and extensor digitorum brevis muscles. In the last one more than one half of stimuli failed to evoke the F-potential. Those are the muscles in which H-potentials almost never appeared. The highest "F-frequency" was recorded in thigh, posterior lower leg muscle and flexor hallucis brevis. Some of the examinees displayed in almost all examined muscles H-potential (6 of 30), the others (9 of 30) had it in neither one or in a single muscle. It looks like as if a kind of H-reflex or F-wave individuals exist. If the H- or F-potentials distribution pattern got projected on the homunculus in quadrupedal position the following idea appears. The thigh muscles, the plantar flexors of the feet and hand and finger flexors are first of all tonic muscles mostly involved in standing or holding. The extensors of the foot/toes, respectively of hand/fingers interrupt phasically the sustained action of standing by lifting the foot/hand from the ground. The muscles with mostly tonic function produce much H-reflexes, transitional forms or at least F-wave with high "F-frequency". Is that a kind of phylogenetical remnants, better developed in the motorically less differentiated legs? Have the H-reflex muscles if compared with F-wave muscles different motor units structure? Have they different motoneurons, with different liability to produce recurrent discharges?     

Orthostatic circulatory disorders of the left leg. Angiographic and lymphangiographic evidence

The absorption, distribution and excretion of piromidic acid and its ethyl ester were investigated in the rat. When administered orally the ethyl ester was well absorbed and subsequently hydrolysed, giving much higher blood and tissue concentration than a corresponding dose of the parent compound. The antimicrobial activity of urine and bile samples was also investigated.     

Recognition of electrocardiographic left arm/left leg lead reversal

The electrocardiographic error of left arm/left leg lead reversal is difficult to identify. PI amplitude greater than PII as a terminal positive component to PIII may diagnose 90% of such errors.     

Cardiovascular and metabolic responses to electrical stimulation-induced leg exercise in spinal cord injury

Electrical stimulation-induced leg muscle contractions provide a useful model for examining the role of leg muscle neural afferents during low-intensity exercise in persons with spinal cord-injury and their able-bodied cohorts. Eight persons with paraplegia (SCI) and 8 non-disabled subjects (CONTROL) performed passive knee flexion/extension (PAS), electrical stimulation-induced knee flexion/extension (ES) and voluntary knee flexion/extension (VOL) on an isokinetic dynamometer. In CONTROLs, exercise heart rate was significantly increased during ES (94 +/- 6 bpm) and VOL (85 +/- 4 bpm) over PAS (69 +/- 4 bpm), but no changes were observed in SCI individuals. Stroke volume was significantly augmented in SCI during ES (59 +/- 5 ml) compared to PAS (46 +/- 4 ml). The results of this study suggest that, in able-bodied humans, Group III and IV leg muscle afferents contribute to increased cardiac output during exercise primarily via augmented heart rate. In contrast, SCI achieve raised cardiac output during ES leg exercise via increased venous return in the absence of any change in heart rate.     

Oxygen uptake transients at the onset and offset of arm and leg work

The halftimes (t1/2) of the VO2 on-and off-responses have been determined on 4 moderately active subjects (1) in arm cranking (VO2 congruent to 1 1/min). (2) in leg pedaling at 4 graded submaximal (VO2 congruent to 0.8 to 2.51/min) work loads, and (3) when superimposing arm cranking on preexisting leg pedaling, both in the supine and in the upright position. In supine experiments the mean t1/2 of the VO2 on-response was longer for arm cranking than for leg pedaling (64 vs 44-49 sec) at equal VO2; however, at the same percentage of arm and leg VO2 max the respective t1/2 were similar. In sitting experiments all t1/2 of the VO2 on-response were shorter than when supine, but the t1/2 for the arms were still slightly longer than those for the legs. When arm cranking was superimposed on preexisting leg pedaling, the t1/4 for arms was reduced both in supine (from 64 to 35-38 sec) and in the sitting position (from 44 to 40 sec). The halftime of the VO2 off-response were much shorter (20-32 sec) than those of the on-response and similar in all experiments. In all conditions the O2 deficits at work onset were considerably larger than the fast component of the corresponding O2 debts during the first minutes of recovery. The difference was totally accounted for by anaerobic glycolysis occurring early during the VO2 on-response, particularly in arm exercise. It is concluded that at submaximal work loads the O2 deficit is accounted for the fast component of the O2 debt plus the O2 equivalent of the early lactate production.     

Muscle quality. I. Age-associated differences between arm and leg muscle groups

To determine the differences between arm and leg muscle quality (MQ) across the adult life span in men and women, concentric (Con) and eccentric (Ecc) peak torque (PT) were measured in 703 subjects (364 men and 339 women, age range 19-93 yr) and appendicular skeletal muscle mass (MM) was determined in the arm and leg in a subgroup of 502 of these subjects (224 men and 278 women). Regression analysis showed that MQ, defined as PT per unit of MM, was significantly higher in the arm ( approximately 30%) than in the leg across age in both genders (P < 0.01). Arm and leg MQ declined at a similar rate with age in men, whereas leg MQ declined approximately 20% more than arm MQ with increasing age in women (P 相似文献   

Hemodynamic and regional blood flow responses to nicotine at rest and during exercise

We hypothesized that nicotine compromises cardiovascular responses to dynamic exercise. Hemodynamic variables were measured in conscious miniswine before and at 2 min of nicotine infusion (20 micrograms.kg-1.min-1; i.a.; N = 6) during resting conditions. Mean arterial pressure elevations (MAP; 14%) and plasma nicotine concentrations (49 +/- 7 ng.ml-1) were similar to those elicited by cigarette smoking in humans. In addition, nicotine increased systemic vascular resistance (SVR; 56%), the heart rate x systolic blood pressure product (RPP; 11%), and regional vascular resistance in the left-ventricular, renal, and splanchnic circulations, while cardiac output decreased (CO; 23%) and skeletal muscle blood flow and vascular resistance were unaffected. Plasma norepinephrine and epinephrine increased by approximately 30% and 90%, respectively. On separate days, the same hemodynamic responses were measured before and at 20 min of treadmill running during vehicle or nicotine infusion for the last 2 min of exercise (N = 10). Nicotine increased MAP (6%), SVR (14%), and RPP (3%), and elevated vascular resistance in the proximal colon and pancreas. Moreover, compared to exercise + vehicle, norepinephrine and epinephrine increased by approximately 13% and 24%, respectively, during exercise + nicotine infusion. These findings suggest that the detrimental effects of nicotine observed at rest are minimized during exercise. Nicotine's effects may be reduced during exercise by competition from local vasodilators in the heart and active musculature, and/or by differing activation of sympathetic nerve activity.     

Impedance cardiography applied to maximal arm cranking exercise: a matter of sampling and processing strategy

PURPOSE: A new ensemble-averaging (EA) approach was developed with the goal of investigating central hemodynamics by transthoracic impedance cardiography during maximal arm cranking. This EA procedure of the first time derivative of impedance changes (dZ/dt) over several cardiac cycles differs from previously reported techniques with respect to cycle selection strategy, according to fixed criteria, and processing methods. METHODS: First, the primary elements of the Kubicek stroke volume (SV) formula, as determined by EA, were compared with the values determined by the standard hand-processing (HP) method over a large range of cardiac outputs. RESULTS: Results showed a very high reliability for ventricular ejection time (r = 0.996), (dZ/dt)min (r = 0.995), SV (r = 0.977), and heart rate (r = 0.999). Second, the EA procedure was applied to six subjects performing a continuous, multistage arm cranking test to volitional fatigue. The present technique allowed for an effective filtering of movement and breathing artifacts of the original signal. Thus, interpretation of the dZ/dt wave form was convenient, even at maximal arm cranking power outputs up to 120 W. Stroke volume ranged from 63.83 to 127.18 mL.beat-1, showing no significant variations with oxygen consumption. Cardiac output increased linearly with oxygen uptake, reaching a mean maximal value of 16 L.min-1. CONCLUSION: The present procedure opens a new field of application to impedance cardiography, permitting to measure cardiac output during maximal arm cranking exercise.     

Central modifications of reflex parameters may underlie the fastest arm movements

Descending and reflex pathways usually converge on common interneurons and motoneurons. This implies that active movements may result from changes in reflex parameters produced by control signals conveyed by descending systems. Specifically, according to the lambda-model, a fast change in limb position is produced by a rapid change in the threshold of the stretch reflex. Consequently, external perturbations may be ineffective in eliciting additional reflex modifications of electromyographic (EMG) patterns unless the perturbations are relatively strong. In this way, the model accounts for the relatively weak effects of perturbations on the initial agonist EMG burst (Ag1) usually observed in fast movements. On the other hand, the same model permits robust reflex modifications of the timing and shape of the Ag1 in response to strong perturbations even in the fastest movements. To test the model, we verified the suggestion that the onset time of the Ag1, even in the fastest movements, depends on proprioceptive feedback in a manner consistent with a stretch reflex. In control trials, subjects (n = 6) made fast unopposed elbow flexion movements of approximately 60 degrees (peak velocity 500-700 degrees/s) in response to an auditory signal. In random test trials, a brief (50 ms) torque of 8-15 Nm either assisting or opposing the movement was applied 50 ms after this signal. Subjects had no visual feedback and were instructed not to correct arm deflections in case of perturbations. In all subjects, the onset time of the Ag1 depended on the direction of perturbation: it was 25-60 ms less in opposing compared with assisting load conditions. Assisting torques caused, at a short latency of 37 ms, an additional antagonist EMG burst preceding the Ag1. The direction-dependent effects of the perturbation persisted when cutaneous feedback was suppressed. It was concluded that the direction-dependent changes in the onset time and duration of the Ag1 as well as the antagonist activation preceding the Ag1 resulted from stretch reflex activity elicited by the perturbations rather than from a change in the control strategy or cutaneous reflexes. The results support the hypothesis on the hierarchical scheme of sensorimotor integration in which EMG patterns and movement emerge from the modification of the thresholds and other parameters of proprioceptive reflexes by control systems.     

The effect of sleep deprivation and exercise load on isokinetic leg strength and endurance

Isokinetic leg strength and fatigue were measured in 24 male U.S. Marine Corps volunteers in a simulated sleep loss and unusually heavy work scenario. Knee extension and flexion peak torque (PT) were measured at three isokinetic speeds (1.57, 2.62 and 3.66 rad.s-1) followed by 45 consecutive maximal reciprocal contractions at 3.14 rad.s-1 to measure fatigue index (FI). All subjects were retested 2 days later following 30-h sleep deprivation (SD). The exercise group (n = 12) spent 25 1-h sessions performing computer tasks, filling out questionnaires and walked 1.61 km with a 50% gross body mass pack load, during each of the 25 sessions. The control group (n = 12) did likewise but did not exercise. Repeated measures ANOVA indicated that flexion PT at 1.57 rad.s-1 decreases (P < 0.013) after SD. Exercise did not affect FI but did decrease PT. It was concluded that carrying a 50% load produces decrements in PT for both extension and flexion but more so for flexion. SD affected PT but had no effect on FI.     

Central effects of clonazepam

The effects of oral administration of clonazepam, a new benzodiazepine derivative (F. Hoffmann-La Roche), on the central nervous system were compared with those of diazepam and several anticonvulsants in mice and rats. 1) Clonazepam exhibited a moderate inhibitory effect on the locomotor activity observed with open-field situation in mice and no effect in rats, while it inhibited markedly the rearing behavior in both animals, the duration of action being approximately six hours. 2) Clonazepam potentiated the methamphetamine-induced hyper-locomotor activity in mice whereas trimethadione had no effect. 3) Clonazepam inhibited with a moderate potency the conditioned avoidance response and response to a fixed-ratio (FR 20) schedule of food reinforcement in rats, the potency being a little weaker than that of diazepam. 4) The muscle relaxant effect of clonazepam determined by the traction test was slightly more potent as compared with that of diazepam. Thiopental hypnosis was markedly potentiated after clonazepam. 5) The clonic (CL), tonic-flexor (TF) and extensor convulsions (TE) induced by pentetrazol were strongly inhibited after clonazepam in mice, anticonvulsant potency against CL and TE of clonazepam being approximately 23 and 21 times stronger than that of diazepam, 3333 and 3846 times that of trimethadione, and over 3047 and 178 times that of phenytoin, respectively. Clonazepam reduced markedly CL and TE elicited by bemegride with about 12 to 14 times stronger potency than diazepam. On the contrary, the anticonvulsant effect of clonazepam against TE of maximal electroshock seizure evoked by supramaximal current was weak, the potency being 0.71 times weaker than that of phenacemide, 0.14 times than phenytoin and 0.24 times than phenobarbital. By the combined administration of clonazepam with other anticonvulsants such as trimethadione and phenytoin against pentetrazol convulsion, and phenacemide, phenytoin and phenobarbital against maximal electroshock seizure, the antagonistic effect of these anticonvulsants was potentiated by 4 to 5 times. 6) The acute toxicity (LD50) of clonazepam was weak but that of phenacemide or phenytoin was potentiated to a certain degree by combined administration with clonazepam. The results suggest that clonazepam has a psychopharmacological profile similar to that of benzodiazepines with a particularly potent anticonvulsant effect on pentetrazol and bemegride convulsions, and the anticonvulsant effect is synergic with that of other anticonvulsants.     

The effects of low-doses of fentanyl, buprenorphine and pentazocine on circulatory responses to endotracheal intubation

This study evaluates the effects of low-doses i.v. fentanyl, buprenorphine and pentazocine on circulatory responses of endotracheal intubation in 70 scheduled surgical patients. Patients were allocated to 5 groups randomly and 2 (n = 11) or 4 (n = 13) micrograms.kg-1 of fentanyl, 0.5 mg.kg-1 of pentazocine (n = 13), 5 micrograms.kg-1 of buprenorphine (n = 10) and saline as a control (n = 23) were administered 5 minutes before the administration of thiopental, respectively. Then, patients were intubated with 0.1 mg.kg-1 of vecuronium. Blood pressure and heart rate were recorded. Only 4 micrograms.kg-1 of fentanyl diminished circulatory responses of systolic blood pressure on the stimuli of endotracheal intubation.     

Age alters regional distribution of blood flow during moderate-intensity exercise

During dynamic exercise in warm environments, requisite increases in skin and active muscle blood flows are supported by increasing cardiac output (Qc) and redistributing flow away from splanchnic and renal circulations. To examine the effect of age on these responses, six young (Y; 26 +/- 2 yr) and six older (O; 64 +/- 2 yr) men performed upright cycle exercise at 35 and 60% of peak O2 consumption (VO2peak) in 22 and 36 degrees C environments. To further isolate age, the two age groups were closely matched for VO2peak, weight, surface area, and body composition. Measurements included heart rate, Qc (CO2 rebreathing), skin blood flow (from increases in forearm blood flow (venous occlusion plethysmography), splanchnic blood flow (indocyanine green dilution), renal blood flow (p-amino-hippurate clearance), and plasma norepinephrine concentration. There were no significant age differences in Qc; however, in both environments the O group maintained Qc at a higher stroke volume and lower heart rate. At 60% VO2peak, forearm blood flow was significantly lower in the O subjects in each environment. Splanchnic blood flow fell (by 12-14% in both groups) at the lower intensity, then decreased to a greater extent at 60% VO2peak in Y than in O subjects (e.g., -45 +/- 2 vs. -33 +/- 3% for the hot environment, P < 0.01). Renal blood flow was lower at rest in the O group, remained relatively constant at 35% VO2peak, then decreased by 20-25% in both groups at 60% VO2peak. At 60% VO2peak, 27 and 37% more total blood flow was redistributed away from these two circulations in the Y than in the O group at 22 and 36 degrees, respectively. It was concluded that the greater increase in skin blood flow in Y subjects is partially supported by a greater redistribution of blood flow away from splanchnic and renal vascular beds.     

Cerebral metabolic effects of sequential periods of hypothermic circulatory arrest

During repair of congenital heart defects, extended periods of hypothermic circulatory arrest (CA) have been shown to cause short-term cerebral metabolic and flow abnormalities as well as long-term neuropsychologic dysfunction. Occasionally, a second period of CA is required during the same operative setting to revise a complicated repair. However, the metabolic effects of two consecutive periods of CA on the brain are unclear. In this study, we compared the recovery of cerebral metabolism after 60 minutes of CA with that after two sequential 30-minute periods of CA separated by a brief period of rewarming (30'SEQ). Fifteen neonatal piglets (2 to 3 kg) were placed on cardiopulmonary bypass at 100 mL.kg-1 x min-1 and cooled to 18 degrees C. Each animal then underwent either 60 minutes of uninterrupted cardiopulmonary bypass at 18 degrees C, 60 minutes of CA, or two 30-minute periods of CA separated by a brief period of rewarming. After these experimental periods, animals were rewarmed to 37 degrees C and weaned from cardiopulmonary bypass. Data were obtained before cardiopulmonary bypass and after cardiopulmonary bypass at 37 degrees C and included measurements of cerebral blood flow by xenon 133 clearance, arterial and sagittal sinus blood gases, and cerebral metabolism (mL O2.100 g-1 x min-1). Our results demonstrated that acute recovery of cerebral metabolism was significantly impaired after 60 minutes of CA and that recovery of cerebral metabolism after two sequential 30-minute periods of CA was significantly better than after 60 minutes of continuous CA.(ABSTRACT TRUNCATED AT 250 WORDS)