Non-exercised Limb Research Articles

Moderate Heat Pain is Less Unpleasant After Brief Intense Eccentric Exercise

Acute exercise can reduce sensitivity to painful stimuli, but the role of eccentric actions in this response is unknown. Research has focused on post-exercise changes in pain intensity and less is known about affective aspects of pain. PURPOSE: The aim was to explore the effects of brief, intense non-dominant arm eccentric exercise on affective and sensory aspects of heat pain sensitivity elicited both in dermatomes of the exercised limb (forearm) and those of a non-exercised limb (lower leg). METHODS: Maximal voluntary concentric contraction strength (MVCCS) of the non-dominant elbow flexors was obtained from ten untrained women who then lowered a dumbbell 18 times with their non-dominant arm. The weight lowering involved three sets of 6 reps at intensities equal to MVCCS. The mean (± SD) absolute weight in each set was18.5 (± 5 lbs), 18.5 (± 5 lbs) and 18.3 (± 5 lbs), respectively. Pain ratings using the intensity and unpleasantness forms of the Descriptor Differential Scale (DDS) were made in response to thermal stimuli applied before and immediately after eccentric exercise. A 30 × 30 mm thermode (TSA-II NeuroSensory Analyzer, Medoc) was used to present heat stimuli to the skin for 2 seconds. Thermal stimuli were applied to a total of 12 unique non-dominant limb sites - six volar forearm (3 medial, 3 lateral) and six posterior lower leg sites. Three randomly ordered temperatures (45, 47, & 49 °C) were applied twice to both leg and arm sites. The criterion used for analysis was the mean of two total DDS intensity and DDS affect scores at each temperature. Six women controls were pre- and post-tested under conditions identical to the treatment group except that no eccentric exercise was performed. RESULTS: Treatment [Eccentric Exercise versus Control] × Time [Pre versus Post] ANOVAs, controlling for arm pain intensity during the MVCCS (0-100 visual analog scale), were not significant for the pain intensity responses at the arm or the leg sites. Significant interactions were found for arm (F1,13=4.714, p=.049) and leg (F1,13=7.066, p=.02) affect ratings at 49 °C. Post-hocs showed lower post-test ratings for exercisers (p <.02). CONCLUSION: Intense, short duration arm eccentric exercise can reduce the unpleasantness of moderate intensity heat stimuli applied to the skin of both an exercised arm and a non-exercised leg.

The Impact Of Exercise On Derived Central Measures Obtained From The Sphygmocor Device

PURPOSE: To investigate whether measures derived from the SphygmoCor device and its associated transfer function are influenced by exercise-induced alterations in vascular tone. To do this, measurements were taken from either the exercised or the contra-lateral non-exercised limb, during repeated and identical incremental hand-grip protocols. METHODS: Eight male subjects performed 3, 3-minute bouts of handgrip exercise, on two occasions. The exercise intensities were set at: 3kg and 5kg, with a final 1.5kg bout performed during cuff ischaemia (1.5Isch). Blood pressure waveforms were recorded from the radial artery of either the exercised or non-exercised limb using applanation tonometry (SphygmoCor) during a 90 s rest period immediately after each exercise bout. Central blood pressures and augmentation indices, an index of arterial stiffness, were derived using the peripheral waveform and the inbuilt SphygmoCor transfer function (TF). RESULTS: Augmentation index (AIx) was consistently ∼10% higher in the exercised arm during all trials compared to the non-exercised lim. Similarly, there was a consistent and significant difference (∼3 mmHg; P<0.05) between exercised and non-exercised arms for the derived central systolic and mean arterial blood pressures. CONCLUSION: Despite similar central haemodynamic responses to the identical bouts of exercise, AI and well as central systolic and mean arterial blood pressures derived from applanation tonometry at the peripheral radial artery were statistically different when assessed at the exercising arm versus the non-exercising arm. Changes in vascular tone with exercise may modify the intrinsic characteristics of the vessel wall and could compromise the assumptions underlying transfer functions used to derive central measures using applanation tonometry.

The impact of exercise on derived measures of central pressure and augmentation index obtained from the SphygmoCor device

The purpose of this study was to investigate whether measures derived from the SphygmoCor device and its associated transfer function are influenced by exercise-induced alterations in vascular tone. Measurements were taken from either the exercised or the contralateral nonexercised limb during repeated and identical incremental hand-grip protocols. Eight male subjects performed three 3-min bouts of hand-grip exercise on two occasions. The exercise intensities were set at 3 kg, 5 kg, with a final 1.5-kg bout performed during cuff ischemia (1.5Isch). Blood pressure waveforms were recorded from the radial artery of either the exercised or nonexercised limb using applanation tonometry (SphygmoCor) during a 90-s rest period immediately after each exercise bout. Central blood pressures and augmentation indexes (AIx), an index of arterial stiffness, were derived using the peripheral waveform and the inbuilt SphygmoCor transfer function (TF). AIx was consistently approximately 10% higher in the exercised arm during all trials compared with the nonexercised limb. Similarly, there was a consistent and significant difference ( approximately 3 mmHg; P < 0.05) between exercised and nonexercised arms for the derived central systolic and mean arterial blood pressures. Despite identical bouts of exercise, AIx and central systolic and mean arterial blood pressures derived from applanation tonometry at the peripheral radial artery were statistically different when assessed at the exercising arm vs. the nonexercising arm. Changes in vascular tone with exercise may modify the intrinsic characteristics of the vessel wall and could compromise the assumptions underlying transfer functions used to derive central measures using applanation tonometry.

Transient increase in femoral arterial blood flow to the contralateral non-exercising limb during one-legged exercise

We studied the effect of exercise intensity and duration on blood flow to the non-exercising leg during one-legged dynamic knee extension. Femoral arterial blood flow (FBF) to the non-exercising leg, blood pressure (BP), and heart rate (HR) were monitored during one-legged dynamic knee extension exercise at 15, 30, and 45% maximal voluntary contraction (MVC) in seven healthy females. There was an interaction between exercise intensity and duration for FBF and FVC (P < 0.01). During the initial phase of contralateral leg exercise at all intensities, FBF and femoral vascular conductance (FVC) of non-exercising leg increased, and the increase was larger at higher intensities (P < 0.01). After initial vasodilatation, FBF and FVC decreased to baseline, which suggests the vasoconstriction. However, FBF and FVC gradually increased during exercise at 15% MVC. We conclude that transient vasodilatation at the onset of exercise is followed by gradual change to vasoconstriction in non-exercising limb during dynamic one-legged exercise and these changes are exercise intensity- and duration-dependent.

Enhanced corticomotor excitability with dynamic fatiguing exercise of the lower limb in multiple sclerosis

To determine if task performance and fatigability during rapid repetitive exercise of the lower limb differ in a group of MS subjects compared to a control group, and what central changes accompany the development of fatigue and the period of recovery. Transcranial magnetic stimulation (TMS) was used to compare motor evoked potential (MEP) responses between 10 clinically definite MS subjects (7F, 33-64 years of age; EDSS <or= 4; MRC grade >or= 4/5) and 13 control subjects during and after 5 bouts of a 15-second maximum rate foot-tapping task performed at 1 minute intervals. Maximum voluntary contraction (MVC) force of ankle dorsiflexion was lower (15 %) in the MS group compared to controls; however there were no differences in the rate of foot tapping. The rate of foot tapping decreased during each bout of exercise to a comparable degree in both groups, but there was no overall deterioration in performance across the 5 repeat bouts in either group. MS subjects showed a greater decline in strength than controls after exercise (20.7+/-7.7% vs. 6+/-3.6%; p<0.05). MEP amplitude increased significantly for the exercised limb in both groups, but the increase was greater in MS subjects (65.9+/-27% vs. 31+/-19.6%; MS vs. control; p<0.05). MEP amplitude also increased for the non-exercised limb in controls (40.6+/-15.6%, p<0.01) but not in MS subjects. Mild to moderately affected MS subjects can perform a fatiguing exercise requiring a high level of central motor control but this is associated with a greater strength loss and increase in corticomotor excitability compared to unaffected individuals. Central adaptive processes are likely to have a significant role in maintaining task performance in MS.

External mechanical compression reduces regional arterial stiffness

Acute aerobic and resistance exercise has been shown to reduce local muscular artery stiffness in the exercised limb while having no effect on the non-exercised limb. The stimulus for these modulations may be related to local muscular compression of underlying vasculature. The purpose of this study was to examine arterial stiffness before and after a series of locally applied external mechanical compressions designed to be similar to the resistance exercise concentric/eccentric duty cycle. One rapidly inflatable cuff was placed around the upper thigh and another around the calf of the left leg in 18 healthy, young (24 +/- 1 years) participants (female n = 10). Cuffs were inflated to a supra-systolic pressure of 200 mmHg for 4 s followed by a 2-s rapid deflation period. One "set" consisted of 12 inflation/deflation cycles. Six sets of 12 compression cycles were performed. Pulse wave velocity (PWV) was used to measure central stiffness (carotid to femoral) and peripheral stiffness (femoral to dorsalis pedis of both legs) before and 10 min after mechanical compressions. No change was found in central PWV (6.2 +/- 0.3 m/s to 6.3 +/- 0.3 m/s, P > 0.05). Peripheral PWV in the non-compressed leg did not change (8.5 +/- 0.4 m/s to 8.3 +/- 0.4 m/s, P > 0.05) while peripheral PWV in the compressed leg significantly decreased from pre to 10 min post (8.6 +/- 0.3 m/s to 7.6 +/- 0.3 m/s, P < 0.05). External compression reduced local artery stiffness of the compressed limb while having no effect on arterial stiffness of the non-compressed limb or central artery stiffness.

Isometric handgrip training does not improve flow-mediated dilation in subjects with normal blood pressure

Isometric HG (handgrip) training lowers resting arterial BP (blood pressure), yet the mechanisms are elusive. In the present study, we investigated improved systemic endothelial function as a mechanism of arterial BP modification following isometric HG training in normotensive individuals. This study employed a within-subject repeated measures design primarily to assess improvements in BA FMD (brachial artery flow-mediated dilation; an index of endothelium-dependent vasodilation), with the non-exercising limb acting as an internal control. Eleven subjects performed four 2-min unilateral isometric HG contractions at 30% of maximal effort, three times per week for 8 weeks. Pre-, mid- and post-training resting ABP and BA FMD (exercised arm and non-exercised arm) were measured via automated brachial oscillometry and ultrasound respectively. BA FMD (normalized to the peak shear rate experienced in response to the reactive hyperaemic stimulus) remained unchanged [exercised arm, 0.029+/-0.003 to 0.026+/-0.003 to 0.029+/-0.004%/s(-1) (pre- to mid- to post-training respectively); non-exercised arm, 0.023+/-0.003 to 0.023+/-0.003 to 0.024+/-0.003%/s(-1) (pre- to mid- to post-training respectively); P=0.22]. In conclusion, improved systemic endothelial function is unlikely to be responsible for lowering arterial BP in this population.

Effects of graded levels of exercise on ipsilateral and contralateral post-exercise resting rectus femoris mechanomyography

Mechanomyography has shown that "resting" muscle is mechanically active, with greater activity after vigorous exercise. This experiment studied the post-exercise resting mechanomyography activity that results from different levels of exercise; the effects of exercise levels on the contralateral non-exercised limb; and the effects of resting muscle length on post-exercise resting mechanomyographic activity. Ten healthy volunteers had mechanomyography recordings over both mid-rectus femoris, at rest, before and after sets (1, 5, 10, 20, and 30 repetitions) of right leg extensions on an isokinetic dynamometer at 60 s(-1). Sets were performed a week apart, after only sedentary activity during the previous two hours. No definite threshold effect was shown. There was a linear correlation between mechanomyography and work done (R = 0.61, P < 0.01). There was a positive correlation of change of activity between the two thighs (R = 0.62, P < 0.01), with the non-exercised thigh demonstrating about half the activity of the exercised thigh. Finally, we observed that mechanomyographic activity was greater when rectus femoris muscle length was shorter (i.e. when the leg was extended versus flexed). We conclude that resting mechanomyography increases with increasing work and that there is a cross-over for increase in mechanomyography in the non-exercised leg, suggesting a neural mechanism. The greater mechanomyographic activity at shorter muscle lengths suggests that muscle that is less stretched could more freely oscillate, producing higher MMG amplitudes. Altered activity of the muscle spindle gamma loop or Golgi tendon apparatus may also play a role in altered activity with different muscle length.

Contralateral muscle fatigue in human quadriceps muscle: evidence for a centrally mediated fatigue response and cross-over effect

The purpose of this investigation was to examine the effects of voluntary muscular fatigue in one lower limb and determine whether a 'cross-over' of fatigue is evident in the contralateral limb. Twenty-eight subjects (13 males and 15 females) performed a series of voluntary and evoked isometric contractions of both the dominant (exercised) and non-dominant (non-exercised) leg extensor muscles, prior to and after a fatigue protocol consisting of a 100-s sustained maximal isometric contraction (MVC) performed by the dominant limb only. Force values and surface electromyography (EMG) from the vastus lateralis muscle were obtained allowing for the determination of twitch and compound action potential (M-wave) values. Maximal twitch tension and peak-to-peak amplitude were significantly decreased after the fatigue test in the dominant limb, as was maximal voluntary force (approximately 65 N reduction), EMG activity (approximately 0.1 mV decrease) and voluntary activation (approximately 17% decline). However, no significant changes were observed in the non-dominant limb with respect to twitch and M-wave properties nor in MVC force. The voluntary activation of the non-dominant limb decreased significantly by 8.7% after the fatigue test, which was performed only on the dominant limb. The results of the present study suggest that the decrease in force production in the exercised limb was primarily related to peripheral fatigue mechanisms, with central fatigue making a lesser contribution. Centrally mediated mechanisms appear to be the sole contributor to fatigue in the non-exercised limb suggesting an anticipatory fatigue response and a 'cross-over' of central fatigue between the exercised and non-exercised contralateral limb.

The effects of unilateral muscle fatigue on bilateral physiological tremor

The aim of this study was to examine the post-exercise effects of fatiguing the wrist extensor muscles of a single arm on postural tremor and muscle activity in both arms. Previous research has shown that, for neurologically normal subjects, the tremor seen within a single limb segment is uncorrelated to that seen contralaterally. However it has been speculated that some bilateral relation does exist, and that the nature of the relation may only become evident under conditions where the neuromuscular system is perturbed. To further investigate this potential bilateral relation, seven healthy subjects were required to adopt a bilateral postural pointing position after exercise-induced fatigue of the wrist extensor muscles of a single arm. Tremor from the forearm, hand and finger segments of each arm, surface EMG activity from extensor digitorum (ED) of each arm, and blood lactate data were collected prior to and after the exercise intervention. The main result was that fatiguing the distal muscles of one arm resulted in a bilateral increase in both the physiological tremor and ED activity. The change in tremor was confined to the index finger with no change in the tremor for the hand or forearm segments of either arm. While three peaks were seen in the frequency profile of the finger tremor, the effects of fatigue were confined to an increase in the peak power of the neurally generated 8-12 Hz tremor component. The contralateral increase in muscle activity was also reflected by a change in the frequency profile of the EMG output, with an increase in the peak power of both muscles following exercise of the wrist extensors of a single arm. The bilateral increases in physiological tremor and EMG activity of ED were only observed during the bilateral pointing task, with no changes in tremor or EMG activity seen for the non-exercised limb during the unilateral exercise protocol. The specificity of the resultant increases in the neurally generated 8-12 Hz component of finger tremor amplitude and EMG activity, coupled with the lack of any changes in tremor for the more proximal arm segments, indicate that these bilateral effects were mediated by an increase in the central neural drive to both limbs. Together this set of results challenges the general assumption of bilateral independence of tremor production, and further illustrate the task dependent nature of exercise-induced fatigue.

Muscle metaboreflex is blunted with reduced vascular resistance response of nonexercised limb in patients with chronic heart failure

Background Exercise-mediated muscle metaboreflex (MMR) activates the sympathetic nervous system afferently and may play an important role in the reduction in blood flow in nonexercised limb, thus enhancing exercised skeletal muscle blood flow (ie, normal regional blood flow redistribution during exercise). However, few data are available to describe the relationship between MMR and peripheral vascular control during exercise in congestive heart failure (CHF). The aim of this study was to determine whether MMR is impaired in CHF, and, if so, whether MMR is related to clinical severity of CHF and to changes in nonexercised limb vascular resistance in CHF. Methods and results Eleven CHF patients and 9 healthy age- and gender-matched controls were examined. All subjects performed a rhythmic handgrip exercise test at 50% of maximal voluntary contraction for 3 minutes on 2 occasions with and without postexercise upper arm regional circulatory occlusion (RCO/non-RCO). Changes in systolic blood pressure were measured and plotted against protocol time for both RCO and non-RCO. The area under each curve was estimated, and the calculating difference in the area between RCO and non-RCO was regarded as MMR. In addition, changes in calf vascular resistance were measured continuously by plethysmography after the handgrip test and the area differences between the RCO and non-RCO data was taken to represent MMR-provoked resistance changes in the nonexercised limb. During the handgrip exercise, systolic blood pressure increased similarly on the 2 occasions for both groups. MMR was significantly lower in CHF patients than in controls (68.2 ± 23.1 versus 160.4 ± 29.6 arbitrary units; P < .05). Decrease in MMR activity was related to clinical severity of CHF (controls, 160.4 ± 29.6; New York Heart Association class II, 87.6 ± 29.8; New York Heart Association class III, 34.3 ± 34.8 arbitrary units; P < .05). The increase in calf vascular resistance between RCO and non-RCO protocols in the control group was significant (+146.5 ± 38.0 arbitrary units; P < .05), whereas the difference in the CHF group was not significant (−72.9 ± 126.9 arbitrary units; not significant). Conclusions Exercise-induced MMR control in mild to moderate CHF is impaired in association with a blunted increase in nonexercised limb vascular resistance. This suggests that blunted MMR activity impairs regional blood flow redistribution and may contribute in part to exercise intolerance in this disorder.

Passive triceps surae stretch inhibits vasoconstriction in the nonexercised limb during posthandgrip muscle ischemia.

We investigated whether selective muscle mechanoreceptor activation in the lower limb opposes arm muscle metaboreceptor activation-mediated limb vasoconstriction. Seven subjects completed two trials: one control trial and one stretch trial. Both trials included 2 min of handgrip and 2 min of posthandgrip exercise muscle ischemia (PEMI). In the stretch trial, a 2-min sustained triceps surae stretch, by brief passive dorsiflexion of the right foot, was performed simultaneously during PEMI. Mean arterial pressure, heart rate, and forearm blood flow (FBF) in the nonexercised arm and forearm vascular conductance (FVC) in the nonexercised arm were measured. During PEMI in the control trial, mean arterial pressure was significantly greater and FBF and FVC were significantly lower than baseline values (P < 0.05 for each). In contrast, FBF and FVC during PEMI in the stretch trial exhibited different responses than in the control trial. FBF and FVC were significantly greater in the stretch trial than in the control trial (FBF, 5.5 +/- 0.4 vs. 3.8 +/- 0.4 ml x 100 ml(-1) x min(-1); FVC, 0.048 +/- 0.004 vs. 0.033 +/- 0.003 unit, respectively; P < 0.05). These results indicate that passive triceps surae stretch can inhibit vasoconstriction in the nonexercised forearm mediated via muscle metaboreceptor activation in the exercised arm.

Sympathetic nerve activity to nonactive muscle of the exercising and nonexercising limb

The purpose of this study was to determine whether efferent sympathetic nerve activity is different to resting skeletal muscles from the exercising and nonexercising limb. MSNA was measured by microneurography in both legs (peroneal nerve) in six subjects during 2 min of unilateral isometric knee extension (IKE; 10-30% of maximum voluntary contraction (MVC)) followed by postexercise circulatory occlusion (PECO). Additional studies using isometric handgrip (30% MVC) followed by PECO were performed. IKE produced significant increases in mean arterial pressure (15 +/- 2 mm Hg) and heart rate (10 +/- 2 bpm). During PECO, mean arterial pressure remained significantly elevated (6 +/- 1 mm Hg) whereas heart rate returned to control. MSNA (bursts.min-1) was not different between the two limbs during control, IKE, PECO, and recovery. Seventy-five to eighty percent of all sympathetic nerve discharges occurred simultaneously in both legs, with the remaining percentage of sympathetic nerve discharges being divided almost equally between the nonexercising and exercising leg. Isometric handgrip produced significant increases in MSNA to the two resting legs with the percent of sympathetic discharges to the two legs being similar to that during IKE. These results indicate that MSNA is similar to the resting muscle in the exercising and nonexercising leg during brief, submaximal isometric exercise (< or = 30% MVC) and postexercise muscle ischemia.

Skeletal muscle vascular responses in human limbs to isometric handgrip

Studies of whole limb blood flow have shown that static handgrip elicits a vasodilatation in the resting forearm and vasoconstriction in the resting leg. We asked if these responses occur in the skeletal muscle vascular bed, and if so, what is the relative contribution of local metabolic versus other mechanisms to these vascular responses. Blood flow recordings were made simultaneously in the skeletal muscle of the resting arm and leg using the Xenon-washout method in ten subjects during 3 min of isometric handgrip at 30% of maximal voluntary contraction. In the arm, skeletal muscle vascular resistance (SMVR) decreased transiently at the onset of exercise followed by a return to baseline levels at the end of exercise. In the leg SMVR remained unchanged during the 1st min of handgrip, but had increased to exceed baseline levels by the end of exercise. During exercise electromyography (EMG) recordings from nonexercising limbs demonstrated a progressive 20-fold increase in activity in the arm, but remained at baseline in the leg. During EMG-signal modelled exercise performed to mimic the inadvertent muscle activity, decreases in forearm SMVR amounted to 57% of the decrease seen with controlateral handgrip. The present study would seem to indicate that vascular tone in nonexercising skeletal muscle in the arm and leg are controlled differently during the early stages of static handgrip. Metabolic vasodilation due to involuntary contraction could significantly modulate forearm skeletal muscle vascular responses, but other factors, most likely neural vasodilator mechanisms, must make major contributions. During the later stages of contralateral sustained handgrip, vascular adjustments in resting forearm skeletal muscle would seem to be the final result of reflex sympathetic vasoconstrictor drive, local metabolic vasodilator forces and possibly neurogenic vasodilator mechanisms.

Venous responses to rhythmic exercise in contralateral forearm and calf.

Ten normal healthy subjects performed a rhythmic handgrip at 30% MVC (maximal voluntary contraction) with and without arterial occlusion of the same limb. Contralateral forearm and calf venous capacitance were simultaneously measured by venous occlusion plethysmography. During rhythmic handgrip at 30% MVC contralateral venous capacitance decreased by -7.17% in the forearm and by -5.14% in the calf. With arterial occlusion the decreases in venous capacitance were even more pronounced: contralateral forearm -14.4% and calf -13.1%. In a second set of experiments (n = 5) rhythmic handgrip at 30% MVC with arrest of the forearm circulation 5 s prior to the cessation of contraction was applied to examine the influence of chemically sensitive metaboreceptors per se on the evoked limb venoconstriction. During the postexercise arterial occlusion forearm venous volume decreased further to -30.6% whereas calf venous volume increased slightly but remained below the control value. After the cessation of the arterial occlusion both forearm and calf capacitance returned to baseline values. Thus, this study provided evidence that as well as a chemically generated reflex arising from the working muscle, central command was found to be involved in the increase in venomotor tone in the nonexercising limbs during rhythmic handgrip at 30% MVC.

Systemic and forearm vascular resistance changes after upright bicycle exercise in man.

1. Blood pressure, cardiac function and forearm blood flow following voluntary maximal upright bicycle exercise were studied in thirteen normal volunteers in a cross-over design against a control day. 2. After exercise there was a short-lived (5-10 min) increase in systolic blood pressure, peak aortic blood velocity and aortic acceleration suggesting a persistence of the positive inotropic influence of exercise. 3. Systemic vasodilation, which was seen immediately exercise stopped, lasted at least 60 min. This was associated with a reduction in diastolic blood pressure for the whole hour. After 30 min systolic blood pressure was also reduced. Heart rate and cardiac output were still significantly elevated and systemic vascular resistance still reduced at 60 min post-exercise. 4. A non-exercising limb vascular bed (forearm) showed a marked vasodilation for 1 h after predominately leg exercise indicating the presence of a vasodilatory influence affecting vascular beds other than the exercising muscle groups.

Changes in venous blood content from active and inactive hindlimb during isotonic exercise.

Venous blood samples were obtained from either exercising (n = 9) or nonexercising (n = 8) hindlimb during a progressive isotonic exercise in rabbits anesthetized with urethane and chloralose. Each experimental session consisted of 5-min nonexercise periods alternated with 6-min exercise periods, followed by a 10-min postexercise period. During each exercise period, stimulation of the distal stump of the right sciatic nerve at 1 Hz induced plantar flexions which lifted loads comparable to 2, 5, 8, 30, or 50% of an afterload at which only an isometric tension developed. Free-flowing venous blood samples were obtained before the first exercise period, during the last minute of each exercise period, and 10 min following the last exercise session. Increases in [Na+], [K+] and lactate concentration were obtained in blood from active limbs. Only lactate concentration increased in blood from nonexercising limbs, while [K+] decreased slightly. Inferences concerning the vascular volume response to this protocol would be quite different depending on the blood sampling site. Changes in blood from inactive tissue, further, may indicate only saturation of homeostatic mechanisms which normally compensate for vascular volume alterations initiated in active tissue.

Hemodynamic response to work with different muscle groups, sitting and supine.

Hemodynamic response to work with different muscle groups, sitting and supine.

Reaction in man of resistance and capacity vessels in forearm and hand to leg exercise.

Reaction in man of resistance and capacity vessels in forearm and hand to leg exercise.