Effects of dynamic leg exercise on subcutaneous blood flow rate in the lower limb of man

Subcutaneous blood flow (SBF) was studied simultaneously in the upper arm at heart level and in the lower limb during positional changes and during leg exercise in seven healthy males. SBF was estimated by local clearance of ¹³³Xenon registered by portable cadmium telluride detectors. Venous pressure was recorded directly on dorsum on the foot. Changing the position from supine to head-up tilt, SBF decreased by 43% (P < 0.01) at the arm level, 40% at the thigh (P < 0.01), 47% at the calf (P < 0.01) and decreased by 51 % at the ankle level (P < 0.01). Performing 20 heel-raisings per min in nearly erect posture, SBF increased by 96% at the thigh (P < 0.01), 25% at the calf (P > 0.1) and increased by 18% at the ankle level (P > 0.1). At 40 heel-raisings per min SBF increased by 99% at the thigh (P < 0.01), 121% at the calf (P < 0.01), but only 44% at the ankle level (P > 0.1). During leg exercise subcutaneous vascular resistance was significantly increased at arm and ankle levels. In contrast, a vasodilatory response was noticed at the thigh and calf levels and seemed associated with a decrease in local venous pressure to below the trigger level of the sympathetic veno-arteriolar reflex mechanism. In conclusion, SBF in the lower limb of man was increased during exercise. The increase in SBF could only partly be ascribed to the concomitant increase in perfusion pressure. The local blood flow response seemed modified by changes in sympathetic nervous activity and metabolic rate.     

Increased sympathetic tone in forearm subcutaneous tissue in primary hypothyroidism

Sympathetic reflex regulation of subcutaneous blood flow (SBF) in the forearm was studied in eight patients with primary hypothyroidism. Diastolic arterial pressure was greater than or equal to 95 mmHg in five patients. SBF was determined by local clearance of Na99mTcO4. Sympathetic vasoconstriction normally seen after lowering the forearm 40 cm below heart level was absent since SBF only decreased by 4% (+/- 7%, P greater than 0.1) during these conditions. In head-up vertical position we noticed a diminished baroreceptor response as SBF at heart level was reduced by 11% (+/- 7%, P greater than 0.1) compared to supine position. After proximal local anaesthesia SBF increased by 351% (+/- 81%, P less than 0.01) and disclosed a normal vasoconstrictor response as SBF was reduced by 53% (+/- 5%, P less than 0.01) during arm lowering. Five of the treated patients were restudied in the euthyroid state. Mean arterial pressure was reduced in mean by 20 mmHg (+/- 6 mmHg, P less than 0.02) during treatment and a significant vasoconstriction was observed both during arm lowering (SBF = -52% (+/- 6%, P less than 0.02)) and in head-up vertical position (SBF = -45% (+/- 11%, P less than 0.02)). In conclusion sympathetic vasoconstrictor activity in adipose tissue is markedly increased in primary hypothyroidism. Sympathetic tone and arterial pressure are reduced during treatment.     

The effect of acute exercise with increasing workloads on inactive muscle blood flow and its heterogeneity in humans

The distribution of blood flow between active and inactive skeletal muscles has been sparsely studied in humans. Here we investigated non-exercising leg blood flow in six healthy young women during intermittent isometric one leg knee extension exercise with increasing workloads. Positron emission tomography was used to measure blood flow in hamstring muscles of the exercising leg, and whole thigh muscles as well as its knee extensor and hamstring compartment of the resting leg. Mean blood flow to the hamstrings of the exercising leg (5.8?±?2.6?ml/100?g/min during the highest exercise workload) and whole thigh muscle of the resting leg (7.1?±?3.8?ml/100?g/min) did not change significantly from rest (4.0?±?0.7 and 4.7?±?1.9?ml/100?g/min, respectively) to exercise, but flow heterogeneity increased substantially at increasing workloads. Importantly, during the highest exercise workload, mean blood flow in the knee extensors of the resting leg decreased (5.5?±?3.0?ml/100?g/min at rest and 3.4?±?2.0?ml/100?g/min during exercise, p?<?0.01) while flow heterogeneity increased (28?±?8% at rest and 83?±?26% during exercise, p?<?0.05). Conversely, in hamstring muscles of the resting leg blood flow increased from 3.9?±?1.0?ml/100?g/min at rest to 11.5?±?6.8?ml/100?g/min during exercise (p?<?0.05) while flow heterogeneity increased from 30?±?7 to 58?±?19% (p?<?0.05). In conclusion, while mean whole thigh muscle blood flow of the resting leg remains at resting level during one leg exercise of the contralateral leg, redistribution of blood flow between muscle parts occurs within the thigh. Based on previous studies, nervous constraints most probably act to cause this blood flow distribution.     

Cardiovascular responses to arm static exercise in men with thoracic spinal cord lesions

Isometric muscle contraction (static exercise) induces circulatory response. Static exercise in individuals with thoracic spinal cord injury (TSCI) induces cardiovascular response and blood redistribution to the non-exercising muscles. The aim of our study was to determine the circulatory response during arm static exercise in individuals with TSCI and able-bodied (AB) controls. Mean blood pressure (MBP), heart rate (HR), cardiac output (CO), leg skin blood flow (SBF), and leg muscle blood flow (MBF) were recorded noninvasively, total peripheral resistance (TPR) was estimated by dividing MBP by CO, and hormonal changes were measured before, during and after static 35% maximal voluntary contraction (MVC) of the arm flexor muscles in seven male individuals with TSCI (T7–T11) and seven age-comparable AB control (32.2 ± 7.6 and 31.0 ± 4.7 years, respectively). The 35% MVC was similar in TSCI and AB individuals (107.3 ± 28.2 and 101.0 ± 22.5 N, respectively). HR, CO, MBP, TPR, SBF and MBF increased in both groups during arm static exercise. Plasma epinephrine concentration increased during arm static exercise in AB controls only (P < 0.05). Circulation to leg muscles was similar in TSCI and AB individuals and the lack of sympathetic vasoconstriction in the paralyzed leg area did not alter the cardiovascular responses during 35% MVC of arm static exercise. We conclude that sympathetic vasoconstriction in the resting leg area did not contribute to the pressor reflex during 35% MVC of arm static exercise.     

Changes in muscle sympathetic nerve activity and calf blood flow during combined leg and forearm exercise

In order to examine efferent sympathetic nerve control of the peripheral circulation during exercise, muscle sympathetic nerve activity (MSNA), calf blood flow (CBF), heart rate (HR), blood pressure (BP) and oxygen uptake were measured during combined foot and forearm exercise. An initial period of rhythmic foot exercise (RFE) (60 min^-1 at 10% of maximal voluntary contraction (MVC) was followed by the addition of rhythmic handgrip exercise (RFE+OCCL) (60 min at 30% of MVC) and by forearm ischaemia after handgrip exercise while continuing RFE (RFE + OCCL). During RFE, CBF in the working leg, HR and oxygen increased respectively by 560%, 121% and 144% when compared with the control rest period, but MSNA (burst rate) was reduced by 13% (P > 0.05) and BP was unchanged. During RFE+RHG, HR, BP and oxygen uptake were greater than during RFE alone. There was no change in CBF, but a significant increase occurred in calf vascular resistance (CVR) and MSNA increased to 121% of the control level. During RFE + OCCL, MSNA, CVR and BP were all higher than during RFE alone, whereas HR and oxygen uptake decreased slightly, although they remained higher than the control values. The increase in CVR in the working leg and the rise in BP during RFE+RHG or RFE+OCCL might be linked to enhancement of MSNA, which may have been reflexly evoked by input from muscle metabolic receptors in the working forearm.     

Slow volume changes in calf and thigh during cycle ergometer exercise

Summary To study the transcapillary fluid movements in the human lower limb in the upright body position and during muscle exercise, the slow changes in thigh and calf volumes were measured by mercury-in-rubber-strain gauge plethysmography. Measurements were carried out on 20 healthy volunteers while sitting, standing and doing cycle ergometer exercise at intensities of 50 and 100-W. A plethysmographic recording of slow extravascular volume changes during muscle exercise was possible because movement artefacts were eliminated by low-pass filtering. While standing and sitting the volumes of both thigh and calf increased due to enhanced transcapillary filtration. While standing the mean rate of increase was 0.13%·min^–1 in the calf and 0.09%·min^–1 in the thigh. During cycle ergometer exercise at 50 and 100 W, the calf volume decreased with a mean rate of –0.09%·min^–1. In contrast, the thigh volume did not change significantly during exercise at 50 W and increased at 100 W. Most of the increase occured during the first half of the experimental period i.e. between min 2 and 12, amounting to +0.6%. Thus, simultaneous measurements revealed opposite changes in the thigh and calf. This demonstrates that the conflicting findings reported in the literature may have occured because opposite changes can occur in different muscle groups of the working limb at the same time. Lowered venous pressure, increased lymph flow and increased tissue pressure in the contracting muscle are considered to have caused the reduction in calf volume during exercise. In accordance with the literature the increases in thigh volume are explained as a result of the enhanced metabolism of the thigh muscles, which do most of the work during cycling: increased metabolism led to local hyperosmolality, which in turn caused an osmotic transcapillary fluid shift into the extravascular space. To some extent an enhanced transcapillary filtration associated with the exercise hyperaemia, might have made a additional contribution to the fluid accumulation.     

The effect of arm training on thermoregulatory responses and calf volume during upper body exercise

Purpose

The smaller muscle mass of the upper body compared to the lower body may elicit a smaller thermoregulatory stimulus during exercise and thus produce novel training-induced thermoregulatory adaptations. Therefore, the principal aim of the study was to examine the effect of arm training on thermoregulatory responses during submaximal exercise.

Methods

Thirteen healthy male participants (Mean ± SD age 27.8 ± 5.0 years, body mass 74.8 ± 9.5 kg) took part in 8 weeks of arm crank ergometry training. Thermoregulatory and calf blood flow responses were measured during 30 min of arm cranking at 60 % peak power (W _peak) pre-, and post-training and post-training at the same absolute intensity as pre-training. Core temperature and skin temperatures were measured, along with heat flow at the calf, thigh, upper arm and chest. Calf blood flow using venous occlusion plethysmography was performed pre- and post-exercise and calf volume was determined during exercise.

Results

The upper body training reduced aural temperature (0.1 ± 0.3 °C) and heat storage (0.3 ± 0.2 J g^?1) at a given power output as a result of increased whole body sweating and heat flow. Arm crank training produced a smaller change in calf volume post-training at the same absolute exercise intensity (?1.2 ± 0.8 % compared to ?2.2 ± 0.9 % pre-training; P < 0.05) suggesting reduced leg vasoconstriction.

Conclusion

Training improved the main markers of aerobic fitness. However, the results of this study suggest arm crank training additionally elicits physiological responses specific to the lower body which may aid thermoregulation.     

Effect of vein pump activation upon muscle blood flow and venous pressure in the human leg

The effect of vein pump activation upon superficial venous pressure and blood flow in human skeletal muscle tissue was studied in 7 healthy subjects. Blood flow was measured in the anterior tibia muscle by the local ¹³³Xe washout technique. The subjects were placed on a steeply tilted couch in nearly erect position. The vein pump in gastroenemius-soleus muscles was activated by heel-raisings. and the anterior tibial muscle remained relaxed during this procedure. Blood flow in the resting anterior tibial muscle was constant before, during and after 20 heel-raisings per min. A more heavy exercise with 40 heel-raisings per min increased blood flow about 100%. This increase in blood flow was absent during venous stasis (40 mmHg), and in areas infiltrated with lidocaine. It is concluded, that intense dynamic exercise in gastrocnemius-soleus muscles, in erect humans, increased blood flow considerably in another crural muscle remaining in the resting state. The present study strongly suggests, that the observed increase in blood flow, was associated with a decrease in regional subfascial venous pressure to below the threshold level of the local sympathetic veno-arteriolar reflex.     

Cardiovascular responses to external compression of human calf muscle vary during graded metaboreflex stimulation

This study investigated the cardiovascular response to a standard external muscle compression during concomitant muscle metaboreflex stimulation of varying intensity in human calf muscle. Eleven healthy male subjects (mean (s.d.) age, 26 (5.6) years; height, 177 (5) cm; weight, 74.3 (6.8) kg) were seated in an isometric dynamometer with the angle of the knee at 90 deg, and the angle of the ankle at 85 deg. After a 150-s rest period, subjects were asked to either perform isometric plantar flexion at 20, 30, 40, 50, 60, 70 or 80% of previously determined maximum isometric contractile force (MVC) for 90 s, or to sit at rest for this period. A thigh cuff maintained circulatory occlusion throughout the exercise period and for 180 s post exercise. After 60 s of post-exercise circulatory occlusion (PECO), a calf cuff was inflated to 300 mmHg for 60 s followed by a further 60 s of PECO alone after which the thigh cuff was deflated. During PECO the mean arterial pressure (MAP) increase from rest was dependent upon the preceding exercise intensity (P < 0.001). Compression elicited a further significant change in MAP, and the magnitude of this change from the PECO baseline was also dependent upon the preceding exercise intensity (P < 0.01). These results are compatible with activation of a metabolically sensitised population of mechanoreceptive afferents in human muscle during external compression.     

Body regional heat pain thresholds using the method of limit and level: a comparative study

Purpose

The purpose of this study was to compare cutaneous heat pain thresholds using the method of limit and level.

Methods

Sixteen young males (23.2 ± 3.2 year, 174.9 ± 4.9 cm, and 70.1 ± 8.6 kg) participated in this study. The thermode temperature increased at a constant rate of 0.1 °C s⁻¹ from 33 °C for the method of limit, whereas the method of level consisted of 3 s heat pulses increasing from 44 °C to 50 °C in 100 s separated by 5 s intervals. All measurements were conducted on 14 body regions (the forehead, neck, chest, abdomen, upper back, upper arm, forearm, waist, hand, palm, thigh, calf, foot, and sole) in 28 °C, 35% relative humidity.

Results

The results are as follows. Heat pain thresholds were on average 3.2 ± 2.1 °C higher for the method of level than for the method of limit (P < 0.05). Second, the correlation coefficient between values by two methods was 0.819 (P < 0.01). Third, lower body regions (thigh, calf, and sole) had higher heat pain thresholds than upper body regions (chest) by the method of level only (P < 0.05). Fourth, body regional subcutaneous fat thickness showed no relationship with heat pain thresholds except the upper arm.

Conclusion

These results indicated that cutaneous heat pain thresholds vary based on the type of heat stimuli and body regions. The method of limit could be applied for predicting accumulated thermal pain starting from moderate heat, whereas the method of level may be applicable for predicting acute heat pain to flames or high heat.

     

High-energy phosphate metabolism in the calf muscle of healthy humans during incremental calf exercise with and without moderate cuff stenosis

It is known that the relevance of a peripheral stenosis for muscle function increases with exercise. Our intention was to investigate the impact of a moderate cuff stenosis (CS) at 120 mmHg of the superficial femoral artery on high-energy phosphate (HEP) metabolism during isotonic, incremental calf exercise. Serial phosphorus 31 magnetic resonance spectroscopy (31P MRS) and velocity-encoded phase-contrast MR imaging (VEPC MRI) were carried out in each leg of ten healthy male volunteers. Each leg underwent four increments of calf exercise (2, 3, 4 and 5 W) followed by recovery during separate exercise sessions with and without a CS at 120 mmHg. The serial 31P MRS measurements had a time resolution of 10 s. VEPC MRI was performed at the end of each increment during separate sessions. During all increments, we detected significant differences (P < 0.05) in the phosphocreatine (PCr) time constants and the amount of PCr hydrolysis between the sessions without and with CS. Regarding the time courses of the PCr, inorganic phosphate (Pi) and pH level, we observed significant differences (P < 0.002) during exercise and recovery. During both conditions, the end-increment PCr levels as well as blood flow correlated significantly with the mechanical power. The PCr time constants during exercise significantly correlated with the intramuscular pH, but not with blood flow or mechanical power. However, the PCr recovery time constants correlated significantly with blood flow and end-exercise pH. Our study shows that reduction of blood flow due to a peripheral stenosis results in a prolongation of PCr time constants, decreased PCr and pH level as well as increased Pi level during exercise. We believe that 31P MRS during incremental exercise might provide additional information for assessing the relevance of a peripheral stenosis and its impact on muscle function.     

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 vasodilatation 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.     

Elderly oarsmen have larger trunk and thigh muscles and greater strength than age-matched untrained men

To evaluate whether regularly performed rowing exercise affects the trunk muscles size and function, and to examine the effect of rowing exercise on thigh muscle size and function in elderly rowers, we compared the cross-sectional area (CSA) and strength of these muscles in elderly male rowers and in age-matched untrained men. Participants were 16 elderly rowing-trained men (ROW age, 67.8 ± 2.3 years) and 18 elderly untrained men (CON 66.2 ± 3.0 years). CSA was measured by MRI in the trunk and thigh muscles. Isometric trunk flexion force and leg extension power were measured. ROW had a 20% larger total trunk muscle CSA than CON (P < 0.01); rectus abdominis was 27% larger, psoas major 64% larger, and erector spinae 14% larger in ROW than in CON (P < 0.05–0.001). Isometric trunk flexion force was related to the CSA of the rectus abdominis (r = 0.777, P < 0.001) and psoas major (r = 0.694, P < 0.001), and was 42% larger in ROW than in CON (P < 0.001). However, force adjusted for the CSA of the muscles did not differ significantly between CON and ROW. In ROW, the CSA was 13% larger in the total thigh muscles (P < 0.01), and leg extension power was 43% higher than in CON (P < 0.001). These results suggest that rowing exercise is a favorable training modality for the trunk muscles, especially psoas major and that it improves thigh muscle size and function in elderly men.     

Changes in lower limb muscle cross-sectional area and tissue fluid volume after transition from standing to supine

Lower limbs show acute fluid shift in response to transition from upright to supine body position. It is hypothesized that this would affect tomographic estimations of muscle mass and composition. Seven healthy subjects were investigated during the initial 120 min of bed rest, using repeated computerized tomography (CT) and continuous bioelectrical impedance analysis (BIA). Thigh and calf muscle cross-sectional area (CSA) decreased (P < 0.05) by 1.9 and 5.5% whereas fat CSA decreased (P < 0.05) by 4.1 and 4.4%, respectively. Radiological density (RD) of muscle showed a simultaneous increase (P < 0.05) by 4.8% in calf but not (P > 0.05) in thigh. No changes occurred (P > 0.05) in muscle or fat CSA or muscle RD in either thigh or calf between the first and second hour of bed rest. Fluid shift, as estimated by BIA, showed an exponential decay in thigh (τ_th = 30 min) and calf (τ_c2 = 37 min) by 2.5 and 8.7%, respectively, from first to 120 min of bed rest. Moreover, the calf showed an initial rapid (τ_c1 = 8 s) 2.2% decrease. The demonstrated short-term changes in leg CSA were more pronounced in the calf than in the thigh. They were similar in muscle and subcutaneous fat. These fluid shifts merit consideration when tomographic imaging techniques are used to estimate muscle mass and composition.     

Oxygen uptake and blood flow of the lower limb in maximal treadmill and bicycle exercise

Summary The present study was undertaken to compare the effects of maximal treadmill and bicycle exercise on maximum oxygen uptake and blood flow in the lower extremity. Mean maximum oxygen uptake in maximal treadmill exercise was higher than that in bicycle exercise (p<0.001). Mean values and standard errors of blood flow measured immediately after maximal treadmill and bicycle exercise in the thigh were 39.1±4.0 and 44.2±2.8 ml/100 ml·min, the difference not being significant. However, a significant difference in blood flow in the calf measured immediately after both types of exercise was observed (p< 0.001). Blood flow in the thigh immediately after bicycle exercise was significantly higher than that in the calf (p<0.001), whereas the difference between thigh and calf in treadmill exercise was small and statistically not significant. Leg blood flow, the average value of blood flow of the thigh and calf added together, was used as an index of blood flow in the lower extremity. It was found that the leg blood flow was significantly higher on the treadmill than with bicycle exercise (p<0.05). From these results, it is suggested that the lower maximum oxygen uptake observed during bicycle exercise as compared with treadmill exercise seems to be due to a lower blood flow in the lower limb.     

Vasoconstriction in active calf persists after discontinuation of combined exercise with high-intensity elbow flexion

The present study aimed to determine whether vasoconstriction in active calf occurring during combined exercise diminished or persisted when added low- and high-intensity elbow flexion exercise ceased and single leg exercise continued. Six active women (mean age, 21.2 years) participated in this study. During 10-min plantar flexion exercise at 10% of maximum voluntary contraction (MVC), elbow flexion exercise at 10% MVC was added over the 3rd and 4th min. Calf blood flow did not change significantly upon superimposition and cessation of this elbow flexion exercise. However, when elbow flexion exercise at 50% MVC was added during the 7th and 8th min, calf blood flow above the resting value (2.23±0.23 mL 100 mL^-1 min^-1) decreased significantly (P<0.05) from 6.72±0.87 (6th min) to 5.14±1.36 mL 100 mL^-1 min^-1 after 2 min of combined exercise and was accompanied by a similar change in the non-exercising calf blood flow value. The vascular conductance of the exercising calf decreased significantly (P<0.01) from 6.48±1.08 (6th min) to 3.11±1.27 mL 100 mL^-1 min^-1 mmHg^-1 at the end of the 2nd min of combined plantar flexion exercise with elbow flexion exercise at 50% MVC. After elbow flexion exercise at 50% MVC was discontinued and plantar flexion exercise at 10% MVC alone was performed, the vascular conductance in the exercising calf remained significantly low for the next 2 min. These results indicate that the vasoconstriction induced by adding high-intensity arm exercise is persistent, suggesting a major contribution of metabo-receptor-mediated vasoconstriction rather than central command- and mechano-receptor-mediated vasoconstriction.     

Influence of concurrent exercise or nutrition countermeasures on thigh and calf muscle size and function during 60 days of bed rest in women

AIM: The goal of this investigation was to test specific exercise and nutrition countermeasures to lower limb skeletal muscle volume and strength losses during 60 days of simulated weightlessness (6 degrees head-down-tilt bed rest). METHODS: Twenty-four women underwent bed rest only (BR, n = 8), bed rest and a concurrent exercise training countermeasure (thigh and calf resistance training and aerobic treadmill training; BRE, n = 8), or bed rest and a nutrition countermeasure (a leucine-enriched high protein diet; BRN, n = 8). RESULTS: Thigh (quadriceps femoris) muscle volume was decreased (P < 0.05) in BR (-21 +/- 1%) and BRN (-24 +/- 2%), with BRN losing more (P < 0.05) than BR. BRE maintained (P > 0.05) thigh muscle volume. Calf (triceps surae) muscle volume was decreased (P < 0.05) to a similar extent (P > 0.05) in BR (-29 +/- 1%) and BRN (-28 +/- 1%), and this decrease was attenuated (P < 0.05) in BRE (-8 +/- 2%). BR and BRN experienced large (P < 0.05) and similar (P > 0.05) decreases in isometric and dynamic (concentric force, eccentric force, power and work) muscle strength for supine squat (-19 to -33%) and calf press (-26 to -46%). BRE maintained (P > 0.05) or increased (P < 0.05) all measures of muscle strength. CONCLUSION: The nutrition countermeasure was not effective in offsetting lower limb muscle volume or strength loss, and actually promoted thigh muscle volume loss. The concurrent aerobic and resistance exercise protocol was effective at preventing thigh muscle volume loss, and thigh and calf muscle strength loss. While the exercise protocol offset approximately 75% of the calf muscle volume loss, modification of this regimen is needed.     

Does 20-min arm crank ergometer exercise increase plasma interleukin-6 in individuals with cervical spinal cord injury?

Interleukin-6 (IL-6) is produced by contracting skeletal muscles and then released into the circulation and considered to mediate the health benefits of exercise against chronic diseases. Individuals with spinal cord injury (SCI) are reported to be at higher risk of developing metabolic diseases. We investigated the IL-6 responses to 20-min arm crank ergometer exercise at 60% of maximum oxygen consumption in eight trained individuals with cervical SCI (CSCI) between C6 and C7, and eight able-bodied trained healthy subjects. The plasma concentrations of IL-6, adrenaline, prostaglandin E₂ and cortisol were measured before, immediately after the exercise, 1 and 2 h after exercise. At rest, the plasma adrenaline concentration was significantly lower in individuals with CSCI than in able-bodied subjects (P < 0.01). On the other hand, the concentration of IL-6 was significantly higher at rest in individuals with CSCI (2.18 ± 0.44 pg/ml, mean ± SEM) than the control (1.02 ± 0.22 pg/ml, P < 0.05). In able-bodied subjects, the plasma adrenaline concentration increased significantly immediately after the exercise (P < 0.01) and returned to the baseline level at 1 h after exercise, and the plasma IL-6 level increased significantly at 1 h after exercise (1.91 ± 0.28 pg/ml, P < 0.05) and returned to the baseline level at 2 h after exercise. In contrast, adrenaline and IL-6 levels were steady throughout the study in individuals with CSCI. The lack of exercise-related IL-6 response in individuals with CSCI could be due to muscle atrophy and sympathetic nervous system dysfunction.     

Thermoregulatory responses to upper body exercise

Summary The purpose of this study was to compare thermoregulatory responses between upper body and lower body exercise. Nine male subjects performed 60 min of arm crank (AC) and cycle (CY) exercise at the same absolute intensity (oxygen uptake=1.61·min^–1) and at the same relative intensity (60% of ergometer specific peak oxygen uptake) in a temperate (24 C, 20% rh) environment. During the absolute intensity experiments, rectal temperature and sweating rate responses were essentially the same for both modes of exercise. In addition, no differences were found for chest, back, arm, or thigh skin temperatures, but calf skin temperature was significantly (P<0.05) lower during arm crank than cycle exercise. During the relative intensity experiments, thermoregulatory responses were lower during arm crank than cycle exercise. In addition, we found no difference between esophageal and rectal temperature values elicited by arm crank exercise. These results indicate that the examined thermoregulatory responses are independent of the skeletal muscle mass employed and dependent upon the absolute metabolic intensity.     

Exhausting handgrip exercise reduces the blood flow in the active calf muscle exercising at low intensity

The calf and forearm blood flows (Q _calf and Q _forearm respectively), blood pressure, heart rate and oxygen uptake of six men and women were studied during combined leg and handgrip exercise to determine whether a reduction of exercise-induced hyperaemia would occur in the active leg when exhausting rhythmic handgrip exercise at 50% maximal voluntary contraction (MVC) was superimposed upon rhythmic plantar flexion lasting for 10 min at 10% MVC (P₁₀) prior to this combined exercise. The Q _calf and Q _forearm were measured by venous occlusion plethysmography during 5-s rests interposed during every minute of P₁₀ exercise and immediately after combined exercise. The muscle sympathetic nerve activity (MSNA) changes were also recorded during leg exercise alone and combined exercise. During plantar flexion performed 60 times · min^–1 with a load equal to 10% MVC (P₁₀), Q _calf was maintained at a constant level, which was significantly higher than the resting value (P < 0.001). When rhythmic handgrip contraction at 50% MVC (H₅₀) and P₁₀ were performed simultaneously, the combined exercise was concluded due to forearm exhaustion after a mean of 51.2 (SEM 5.5) s. At exhaustion, Q _calf had decreased significantly from 20.6 (SEM 3.0) ml · 100 ml^–1 · min^–1 (10th min during P₁₀ exercise) to 15.3 (SEM) ml · 100 ml^–1 · min^–1 (P = 0.001), whereas Q _forearm had increased significantly (0.001 < P < 0.01) from 8.6 (SEM 1.9) ml · 100 ml^–1 · min^–1 (10th min of P₁₀ exercise) to 26.2 (SEM 3.2) ml · 100 ml^–1 · min^–1. The mean blood pressure remained at an almost constant level during the 3rd to 10th min of P₁₀ exercise and increased markedly when H₅₀ was added. The calf vascular conductance during combined exercise decreased significantly (0.001 < P < 0.01) compared with that at the 10th min of P₁₀ alone. Although the MSNA (expressed as burst rate) remained unchanged during P₁₀ exercise for 10 min, it increased markedly when exhausting H₅₀ and P₁₀ exercise were performed simultaneously. These findings indicated that superimposition of exhausting handgrip exercise at 50% MVC caused a vasoconstriction in the exercising calf due to increased MSNA, which counteracted the vasodilatation in this active muscle.