The State of the Regional Blood Flow in the Upper Extremity after Dosed Physical Exercise

The effect of local isometric exercise on hand and forearm blood flow was studied. With maximum muscular exercise performed by both males and females, a decrease in hand and forearm blood flow was due to vasoconstriction caused by the mechanical pressure of working muscles. With 75 and 50% loads, marked hyperemia was observed in the main and microcirculatory vessels in the hand and forearm, which was rather long-lasting in the hand because of the difficulty of the forearm venous outflow. The minimum loads affected mainly the microcirculation, and no significant hemodynamic changes in main vessels were observed. The exercise performed at 50% of maximum muscular force was taken as an optimum load in kinesotherapeutic programs.     

Effect of Acute Exposure to Moderate Altitude on Muscle Power: Hypobaric Hypoxia vs. Normobaric Hypoxia

When ascending to a higher altitude, changes in air density and oxygen levels affect the way in which explosive actions are executed. This study was designed to compare the effects of acute exposure to real or simulated moderate hypoxia on the dynamics of the force-velocity relationship observed in bench press exercise. Twenty-eight combat sports athletes were assigned to two groups and assessed on two separate occasions: G1 (n = 17) in conditions of normoxia (N1) and hypobaric hypoxia (HH) and G2 (n = 11) in conditions of normoxia (N2) and normobaric hypoxia (NH). Individual and complete force-velocity relationships in bench press were determined on each assessment day. For each exercise repetition, we obtained the mean and peak velocity and power shown by the athletes. Maximum power (P_max) was recorded as the highest P_mean obtained across the complete force-velocity curve. Our findings indicate a significantly higher absolute load linked to P_max (∼3%) and maximal strength (1RM) (∼6%) in G1 attributable to the climb to altitude (P<0.05). We also observed a stimulating effect of natural hypoxia on P_mean and P_peak in the middle-high part of the curve (≥60 kg; P<0.01) and a 7.8% mean increase in barbell displacement velocity (P<0.001). No changes in any of the variables examined were observed in G2. According to these data, we can state that acute exposure to natural moderate altitude as opposed to simulated normobaric hypoxia leads to gains in 1RM, movement velocity and power during the execution of a force-velocity curve in bench press.     

Regulation of External Respiration and Gas Exchange during a 20-Day Exposure to Sessions of Intermittent Normobaric Hypoxia

A study was made of the effects of a 20-day course of intermittent normobaric hypoxia (INH) on the parameters of gas exchange and the regulation of respiration in healthy volunteers. A phasic change in oxygen consumption at rest was observed: it decreased on the 10th day of the INH course and increased on the 20th day, with a parallel increase in the efficiency of pulmonary ventilation. According to the hypercapnic test, the ventilatory response threshold decreased, whereas ventilatory sensitivity increased; these effects were most pronounced during the first ten days of INH training and still detectable in recovery. It was assumed that the first phase of training (up to the tenth day) is associated with compensatory activation of pulmonary ventilation owing to an increase in peripheral and central chemosensitivity to the CO₂ stimulus. In the second phase, which was associated with further slight changes in the parameters of external respiration, the gas exchange level is restored owing to an adaptive increase in efficiency of oxygen utilization in cells and tissues.     

PP and PT Intervals and TP Segment in Human Electrocardiogram under Experimental Acute Normobaric Hypoxia

Seven male volunteers aged 22–27 years took part in the laboratory experiment for the determination of body response to acute normobaric hypoxia where they inhaled an oxygen–nitrogen gas mixture (9% of О₂) for 25 min. At least 100 cardiac cycles at each of six experimental time points have been recorded by using an electrocardiogram (ECG) recording technique in standard lead II. Mean heart rate (±SD) before hypoxia was 64 ± 2 bpm; the duration of the PP interval was 0.94 ± 0.07 s, that of the PT interval was 0.51 ± 0.02 s, and that of the TP segment was 0.41 ± 0.07 s. Five minutes after hypoxia, it has been found that heart rate (HR) increased by 19%; the duration of the PP and PT intervals and TP segment decreased by 16%, 6%, and 30%, respectively. Twenty minutes after hypoxia, all the parameters reached their initial values. Five and fifteen minutes after hypoxia, HR reached 59 ± 3 bpm; PP interval and TP segment increased by 9% and 14%, respectively, compared to the initial values; PT interval was the same as the initial value at the baseline. The correlation coefficient r_p (PP/PT) was 0.10–0.54; r_p (PP/TP) was 0.94–0.99. The intervals PP and TP were found to be identical.     

Relationships between Cerebral Blood Flow Dynamics and Bioelectric Activity of the Human Brain in Experimental Acute Hypoxia

The relationships between the parameters of oxygen content in the body (hemoglobin saturation with oxygen and trancutaneous oxygen tension), central hemodynamics (cardiac output), and cerebral hemodynamics (cerebral blood flow rate) were studied during a hypoxic test (inhalation of an oxygen–nitrogen mixture containing 8% oxygen for 15 min). Special attention was paid to the relationships between the dynamics of cerebral blood flow and cerebral bioelectric activity measured by EEG parameters. It was demonstrated that the trancutaneous oxygen tension decreased to a greater extent than the hemoglobin saturation with oxygen and the cerebral blood flow increased to a greater extent than the cardiac output. The increase in cerebral blood flow and the increase in the indices and power of and EEG waves in the course of hypoxia were strongly positively correlated with each other in most subjects. However, if these parameters were considered in the series of subjects, the degree of the increase in the indices and power of and waves in different subjects was negatively correlated with the increase in the cerebral blood flow. The results are explained in terms of redistribution of blood flow in the body to provide a better oxygen supply to the brain and optimization of the ratios between the cerebral oxygen consumption and the functional load on the system of oxygen supply.     

Changes in the Central Regulation of the Respiratory Function after a Single Session of Intermittent Normobaric Hypoxia

Correlations between EEG findings and external respiration and gas exchange indices recorded prior to and after a single session of intermittent normobaric hypoxia were calculated by means of the Neirokartograf (MBN) program. Changes in the central regulation of respiration were observed for a period of more than one hour. The hypoxia caused a decline in EEG coherence in the left hemisphere and a decrease in the statistically significant correlations between the bioelectric rhythms of the , , and ranges and the external respiration and gas exchange indices.     

Role of Nitric Oxide Synthase in the Infarct-Limiting Effect of Normobaric Hypoxia

Journal of Evolutionary Biochemistry and Physiology - The study was carried out in male Wistar rats. Animals were randomly divided into normoxic control groups and groups exposed to normobaric...     

Aging Contributes to Inflammation in Upper Extremity Tendons and Declines in Forelimb Agility in a Rat Model of Upper Extremity Overuse

We sought to determine if tendon inflammatory and histopathological responses increase in aged rats compared to young rats performing a voluntary upper extremity repetitive task, and if these changes are associated with motor declines. Ninety-six female Sprague-Dawley rats were used in the rat model of upper extremity overuse: 67 aged and 29 young adult rats. After a training period of 4 weeks, task rats performed a voluntary high repetition low force (HRLF) handle-pulling task for 2 hrs/day, 3 days/wk for up to 12 weeks. Upper extremity motor function was assessed, as were inflammatory and histomorphological changes in flexor digitorum and supraspinatus tendons. The percentage of successful reaches improved in young adult HRLF rats, but not in aged HRLF rats. Forelimb agility decreased transiently in young adult HRLF rats, but persistently in aged HRLF rats. HRLF task performance for 12 weeks lead to increased IL-1beta and IL-6 in flexor digitorum tendons of aged HRLF rats, compared to aged normal control (NC) as well as young adult HRLF rats. In contrast, TNF-alpha increased more in flexor digitorum tendons of young adult 12-week HRLF rats than in aged HRLF rats. Vascularity and collagen fibril organization were not affected by task performance in flexor digitorum tendons of either age group, although cellularity increased in both. By week 12 of HRLF task performance, vascularity and cellularity increased in the supraspinatus tendons of only aged rats. The increased cellularity was due to increased macrophages and connective tissue growth factor (CTGF)-immunoreactive fibroblasts in the peritendon. In conclusion, aged rat tendons were overall more affected by the HRLF task than young adult tendons, particularly supraspinatus tendons. Greater inflammatory changes in aged HRLF rat tendons were observed, increases associated temporally with decreased forelimb agility and lack of improvement in task success.     

Thermoregulation and Blood Circulation in Adults during Short-Term Exposure to Extreme Temperatures

Two groups of male and female subjects aged 36–50 years were examined prior to and after short-term exposure to extreme temperatures. One group was exposed to heating in a sauna, and the other was exposed to cooling in ice-cold water. In both cases, the changes in some indices of thermoregulation and blood circulation approximated critical values. It is therefore concluded that, in adults, such procedures are stressful and dangerous for health.     

Effect of Short-Term Intermittent Normobaric Hypoxia on the Regulation of External Respiration in Humans

Baseline external respiration and gas exchange values, as well as ventilatory thresholds and sensitivity to the O₂ and CO₂ stimuli in hypoxic and hypercapnic tests, were measured 1 h before and after a session of intermittent normobaric hypoxia (INH) (six repetitions with a 5-min inhalation of a gas mixture (10% O₂) alternating with a 3-min inhalation of atmospheric air). After an INH session, the background CO₂ level in the lungs increased by 10%. In the hypercapnic test, the actuation threshold of the ventilatory response did not change, whereas ventilatory sensitivity increased. The maximal pulmonary ventilation and the corresponding critical CO₂ level in the lungs also increased at the end of the test. In the hypoxic test, the ventilatory response occurred at a decreased level of blood oxygenation after an INH session, the pulmonary ventilation level being decreased and the CO₂ content in the lungs being increased at the end of the test. The data obtained evidence the maintenance of changed gas homeostasis for 1 h after an INH session. In this process, control of respiration was effected, with the hypoxic drive being weakened and the peripheral chemoreceptor sensitivity being decreased. The hypercapnic drive also increased, which may be determined by readjustment in the central mechanisms of respiratory regulation.     

Morphological and Functional Changes in Overweight Persons under Combined Normobaric Hypoxia and Physical Training

Functional and morphological changes were studied in overweight persons in tests with various combinations of normobaric hypoxia and physical training. It was shown that normobaric hypoxia combined with training can be used for increasing physical working capacity and aerobic capacity in overweight persons. A combination of physical training and breathing hypoxic gas mixtures was demonstrated to be the most effective method of correcting and increasing the physiological functional potential in overweight persons.     

Influences of Normobaric Hypoxia Training on Physical Fitness and Metabolic Risk Markers in Overweight to Obese Subjects

Previous studies suggested that hypoxia and exercise may have a synergistic effect on cardiovascular and metabolic risk factors. We conducted a single blind study in overweight to obese subjects to test the hypothesis that training under hypoxia (HG, n = 24, FiO₂ = 15%) results in similar or even greater improvement in body weight and metabolic risk markers compared with exercise under normoxia (NG, n = 21, FiO₂ = 21%). After an initial metabolic evaluation including incremental exercise testing, subjects trained in normoxic or hypoxic conditions thrice weekly over a 4‐week period at a heart rate corresponding to 65% of maximum oxygen uptake (VO_2max). The experimental groups were similar at the start of the investigation and weight stable during the training period. Subjects in the hypoxia group trained at a significantly lower workload (P < 0.05). Yet, both groups showed similar improvements in VO_2max and time to exhaustion. Respiratory quotient and lactate at the anaerobic threshold as well as body composition improved more in the hypoxia group. We conclude that in obese subjects, training in hypoxia elicits a similar or even better response in terms of physical fitness, metabolic risk markers, and body composition at a lower workload. The fact that workload and, therefore, mechanic strain can be reduced in hypoxia could be particularly beneficial in obese patients with orthopedic comorbidities.     

Secretion Pores in Human Endothelial Cells during Acute Hypoxia

Weibel-Palade bodies (WPB) are endothelial vesicles that store von Willebrand factor (vWF), involved in the early phase of hemostasis. In the present study we investigated the morphodynamics of single WPB plasma membrane fusion events upon hypoxic stimulation by using atomic force microscopy (AFM). Simultaneously, we measured vWF release from endothelial cells to functionally confirm WPB exocytosis. Exposing human endothelial cells to hypoxia (pO2 = 5 mm Hg) we found an acute (within minutes) release of vWF. Despite acute vWF release, potential cellular modulators of secretion, such as intracellular pH and cell volume, remained unchanged. We only detected a slight instantaneous increase of cytosolic Ca2+ concentration. Although overall cell morphology remained virtually unchanged, high resolution AFM images of hypoxic endothelial cells disclosed secretion pores, most likely the loci of WPB exocytosis on luminal plasma membrane. We conclude that short-term hypoxia barely alters overall cell morphology and intracellular milieu. However, at nanometer scale, hypoxia instantaneously switches the smooth luminal plasma membrane to a rough activated cell surface, covered with secretion pores that release vWF to the luminal cell surface.     

Zinc Dyshomeostasis in Cardiomyocytes after Acute Hypoxia/Reoxygenation

This study aimed to assess the protective roles of polysaccharides from Agaricus blazei Murill (ABP) against cadmium (Cd)-induced damage in chicken livers. A total of 80 Hy-Line laying chickens (7 days old) were randomly divided into four groups (n = 20). Group I (control) was fed with a basic diet and 0.2 ml saline per day, group II (Cd-treated group) was fed with a basic diet containing 140 mg/kg cadmium chloride (CdCl₂) and 0.2 ml saline per day, group III (Cd + ABP-treated group) was fed with a basic diet containing 140 mg/kg CdCl₂ and 0.2-ml ABP solution (30 mg/ml) per day via oral gavage, and group IV (ABP-treated group) was fed with 0.2-ml ABP solution (30 mg/ml) per day via oral gavage. The contents of Cd and malondialdehyde (MDA), the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX), the messenger RNA (mRNA) levels of inflammatory cytokines and heat shock proteins (HSPs), the protein levels of HSPs, and the histopathological changes of livers were evaluated on days 20, 40, and 60. The results showed that Cd exposure resulted in Cd accumulating in livers and inhibiting the activities of antioxidant enzymes (SOD and GSH-PX). Cd exposure caused histopathological damage and increased the MDA content, the mRNA levels of inflammatory cytokines (TNF-α, IL-1β, and IL-6) and HSPs (HSP27, HSP40, HSP60, HSP70, and HSP90) and the protein levels of HSPs (HSP60, HSP70, and HSP90). ABP supplementation during dietary exposure to Cd reduced the histopathological damage and decreased the contents of Cd and MDA and the expression of inflammatory cytokines and HSPs and improved the activities of antioxidant enzymes. The results indicated that ABP could partly ameliorate the toxic effects of Cd on chicken livers.     

急性低氧对高原土生动物藏系绵羊血气的影响

为了探讨急性低氧时藏系绵羊(Ovis aries)的血气特点,揭示其低氧适应机制,将7只雄性藏系绵羊和5只雄性移居绵羊分别置于高低压氧舱内,测定模拟海拔0、2 300和4 500 m时各动物清醒状态下的血气指标。用热稀释法测定心输出量。使用血气分析仪和EG7血样板,测定动脉及混合静脉血的血气指标,按Ficks方法计算氧耗量。结果显示,随着模拟海拔高度的升高,藏羊和移居羊的动静脉血氧饱和度(So2)、氧分压(Po2)、二氧化碳分压(Pco2)都呈明显下降趋势(P<0.05),血红蛋白浓度(Hb)、血液pH、心输出量及氧耗量虽无明显的差异性改变,但它们在4 500 m处的绝对值是增加的。在相同海拔,藏羊的Hb明显低于移居羊(P<0.05),4 500 m时藏羊的动脉血氧饱和度(Sao2)及组织摄氧量显著高于移居羊(P<0.05)。表明藏羊在急性低氧时表现出的高Sao2及高组织摄氧量,低Hb、低pH是它适应高原低氧的生理基础。     

Linear Blood Velocity in Arteries of the Brain Hemispheres in Left-Handers and Right-Handers during Hypoxia

Transcranial Doppler ultrasonography was used to measure the linear blood velocity (LBV) in the middle cerebral artery (MCA) of the right and left hemispheres in right-handers and left-handers who were breathing a gas mixture with 10% oxygen through a mask at normal barometric pressure. No interhemispheric differences were found in left-handers before hypoxia. The maximum systolic velocity was higher in the MCA of the left hemisphere in right-handers. Left-handers had a higher LBV in the right hemisphere than did right-handers. LBV in the MCA of both hemispheres increased in both left-handers and right-handers as a result of hypoxia. Aggravation of hypoxia caused a decrease in LBV in the left hemisphere in right-handers.     

Hormonal and Neuromuscular Responses to Mechanical Vibration Applied to Upper Extremity Muscles

Objective

To investigate the acute residual hormonal and neuromuscular responses exhibited following a single session of mechanical vibration applied to the upper extremities among different acceleration loads.

Methods

Thirty male students were randomly assigned to a high vibration group (HVG), a low vibration group (LVG), or a control group (CG). A randomized double-blind, controlled-parallel study design was employed. The measurements and interventions were performed at the Laboratory of Biomechanics of the University of L''Aquila. The HVG and LVG participants were exposed to a series of 20 trials ×10 s of synchronous whole-body vibration (WBV) with a 10-s pause between each trial and a 4-min pause after the first 10 trials. The CG participants assumed an isometric push-up position without WBV. The outcome measures were growth hormone (GH), testosterone, maximal voluntary isometric contraction during bench-press, maximal voluntary isometric contraction during handgrip, and electromyography root-mean-square (EMG_rms) muscle activity (pectoralis major [PM], triceps brachii [TB], anterior deltoid [DE], and flexor carpi radialis [FCR]).

Results

The GH increased significantly over time only in the HVG (P = 0.003). Additionally, the testosterone levels changed significantly over time in the LVG (P = 0.011) and the HVG (P = 0.001). MVC during bench press decreased significantly in the LVG (P = 0.001) and the HVG (P = 0.002). In the HVG, the EMG_rms decreased significantly in the TB (P = 0.006) muscle. In the LVG, the EMG_rms decreased significantly in the DE (P = 0.009) and FCR (P = 0.006) muscles.

Conclusion

Synchronous WBV acutely increased GH and testosterone serum concentrations and decreased the MVC and their respective maximal EMG_rms activities, which indicated a possible central fatigue effect. Interestingly, only the GH response was dependent on the acceleration with respect to the subjects'' responsiveness.     

Decreased Extracellular Adenosine Levels Lead to Loss of Hypoxia-Induced Neuroprotection after Repeated Episodes of Exposure to Hypoxia

Achieving a prolonged neuroprotective state following transient ischemic attacks (TIAs) is likely to effectively reduce the brain damage and neurological dysfunction associated with recurrent stroke. HPC is a phenomenon in which advanced exposure to mild hypoxia reduces the stroke volume produced by a subsequent TIA. However, this neuroprotection is not long-lasting, with the effects reaching a peak after 3 days. Therefore, in this study, we investigated the use of multiple episodes of hypoxic exposure at different time intervals to induce longer-term protection in a mouse stroke model. C57BL/6 mice were subjected to different hypoxic preconditioning protocols: a single episode of HPC or five identical episodes at intervals of 3 days (E3d HPC) or 6 days (E6d HPC). Three days after the last hypoxic exposure, temporary middle cerebral artery occlusion (MCAO) was induced. The effects of these HPC protocols on hypoxia-inducible factor (HIF) regulated gene mRNA expression were measured by quantitative PCR. Changes in extracellular adenosine concentrations, known to exert neuroprotective effects, were also measured using in vivo microdialysis and high pressure liquid chromatography (HPLC). Neuroprotection was provided by E6d HPC but not E3d HPC. HIF-regulated target gene expression increased significantly following all HPC protocols. However, E3d HPC significantly decreased extracellular adenosine and reduced cerebral blood flow in the ischemic region with upregulated expression of the adenosine transporter, equilibrative nucleoside transporter 1 (ENT1). An ENT1 inhibitor, propentofylline increased the cerebral blood flow and re-established neuroprotection in E3d HPC. Adenosine receptor specific antagonists showed that adenosine mainly through A1 receptor mediates HPC induced neuroprotection. Our data indicate that cooperation of HIF-regulated genes and extracellular adenosine is necessary for HPC-induced neuroprotection.