Elastic stockings, performance and leg pain recovery in 63-year-old sportsmen.

This study was undertaken to determine whether or not elastic compression stockings (ECS) can be used in elderly sportsmen to increase performance and leg pain recovery between two maximal exercises. For 2 weeks, 12 trained elderly cyclists, 63 (3) years old, performed two 5-min maximal exercises, Plim1 and Plim2, separated by an 80-min recovery period, twice a week with a 2-day rest interval. During the 80-min recovery period, they randomly wore or did not wear grip-top ECS Ganzoni-Sigvaris. ECS exerted a 44 hPa pressure at the ankle. Blood lactate concentrations, hematocrit, and plasma volume were measured after a 60-min rest and every 20 min during recovery. Leg sensations were assessed with a questionnaire. The decrease in maximal power between Plim1 and Plim2 was lower when wearing the ECS during the 80-min recovery period; when expressed as a percentage of Plim1, the difference reached 2.1 (1.4)%, P < 0.01. Between the two exercises, blood lactate concentrations and hematocrit were significantly decreased when wearing ECS. The increase in plasma volume was not significant. The 12 cyclists stated that wearing the ECS had a positive effect on their leg pain. Ten of the cyclists thought that it could have influenced their performance. However, no relationship was found between the gain in performance and the leg pain sensation. It was concluded that wearing ECS during an 80-min recovery period significantly increased subsequent performance. This was associated with a reduction in lactate and hematocrit.

Air plethysmography: an alternative method for assessing peripheral circulatory adaptations during spaceflights.

A new approach to the study of peripheral vascular hemodynamics in microgravity was initiated by designing an alternative methodology: air plethysmography (AP). This is the only technique that enables the quantification of vascular hemodynamics from gross measurements performed on the limbs. This paper reports a description of the device and of the measurement protocol. A comparative study showed that AP yields results that are well correlated, although not in agreement, with those obtained by means of the reference method in the laboratory (mercury strain gauge plethysmography, MSGP; for venous capacity, correlation coefficient r = 0.8, P < 0.0001, limits of agreement--0.9 ml.100 ml-1 and 1.4 ml.100 ml-1; for arterial flow index, correlation coefficient r = 0.7, P < 0.0006, limits of agreements -20.4 ml.min-1 and 37.2 ml.min-1; for half-emptying time, correlation coefficient r = 0.9, P < 0.0001, limits of agreement -0.88 s and 0.77 s), and that are characterized by good reproducibility (coefficient of variation in general lower than 12%). Preliminary findings during spaceflight, on board the Mir Space Station, yielded data that is expected to improve our knowledge of vascular deconditioning in conditions of weightlessness.

Use of thigh pressure cuffs to modulate simulated microgravity-induced changes in the skin measured with high-resolution B-scan ultrasound.

OBJECTIVE: The aim of the present study was to evaluate the fluid shift in a simulated microgravity experiment and to test the use of thigh cuffs to help alleviate the problem. METHODS: The change in skin thickness was assessed by a 20 MHz B-scan ultrasound device. This was performed on eight volunteers who underwent two successive 7-day periods of -6 degrees anti-orthostatic bed-rest, with or without the daytime use of thigh cuffs. The thigh cuffs were used to counteract the development of facial oedema. RESULTS: In the control group (without thigh cuffs), the results showed a steady increase in skin thickness of the combined dermis and hypodermis of the forehead and a reduction of the thickness of this tissue on the tibia. For the countermeasure group, although thigh cuffs were only employed during the daytime - being removed at night - their use reduced the amplitude and kinetics of the fluid shift, resulting in greater beneficial effects at the end of the day than early in the morning. CONCLUSION: These results of objective measurements of skin made using a non-invasive high frequency ultrasonography method confirm reports by cosmonauts of a reduction in facial oedema and a more 'comfortable' adaptation to microgravity by the use of thigh cuffs during space flight. This system is potentially promising for investigating fluid shifts in the skin and may prove useful in the evaluation of some oedematous skin diseases, as well as their therapy.

Effects of aerobatics flight on oxygen consumption and heart rate control: influence on autonomic cardiovascular regulation during recovery.

Oxygen consumption (VO2) and blood pressure regulation were measured on five pilots during and after normal training aerobatics flights of a mean duration of 35 min. The acceleration vector along the longitudinal axis of the body (Gz) ranged from + 6.5 Gz to -3.5 Gz. VO2 was continuously monitored by a miniature telemetric system (K2). Heart rate (fc), the abdominal muscle electromyogram (EMG) and Gz levels were recorded synchronously on a magnetic tape recorder. A tilt test was performed pre- and post-flight to evaluate fc and blood-pressure variability. The left forearm blood flow was measured by strain-gauge plethysmography. The mean VO2 during flight was 1.2 l x min(-1), with a peak VO2 of 2.1 l x min x fc ranged between 55 and 165 beats x min(-1) and showed a progressive increase under the effect of + Gz, with a sudden fall during -Gz. The abdominal muscle EMG indicated the occurrence of muscle contraction under Gz load. Maximal responses were observed during the Gz phase. Comparison between pre- and post-flight data showed lower post-flight systolic blood pressure with higher fc. Before flight, upright tilt induced a significant increase in low/ high frequency fc, as assessed using spectral analysis. This change was suppressed after flight. In summary, these data show that aerobatics flight leads to enhanced energy expenditure, mainly because of increased skeletal muscle work. The post-flight tilt test showed that aerobatic flight favors parasympathetic drive and, consequently, modifies blood pressure regulation during recovery. This action may decrease + Gz tolerance to a second aerobatics flight performed shortly after the first.

Intense endurance training on heart rate and blood pressure variability in runners.

UNLABELLED: Physical training with incomplete recovery times can produce significant fatigue. A study of cardiovascular responses showed that there is a sympathetic and a parasympathetic form of fatigue. PURPOSE: The purpose of this experimentation was to measure the effects of intense endurance training on autonomic balance through a spectral analysis study of the heart rate (HR) and systolic blood pressure (SBP). METHODS: Eight elite runners were tested twice: after a relative rest period (RRP) of 3 wk and after an 12-wk intense training period (ITP) for endurance. At the end of each phase, the subjects were tested by means of a VO2max test and a tilt-table test. RESULTS: The resting heart rate (HR) variability was lower (P < 0.001) in the intensive training phase. Likewise, there were differences in the low-frequency (0.04-0.150 Hz; LF) and high-frequency (0.150-0.500 Hz; HF) components and the LF/HF ratio of the HR spectral analysis. The LF spectral power was significantly lower in the supine position (P < 0.05) during ITP. Upright tilting was accompanied by a 22.6% reduction in HF values during the rest period, whereas in ITP the HF spectral power rose by 31.2% (P < 0.01) during tilt, characterizing a greater parasympathetic system control. Sympathetic control represented by the LF/HF ratio regressed markedly (P < 0.01) in response to the tilt test in ITP. CONCLUSIONS: The spectral analysis of SBP in the high frequencies shows that the changes in cardiac parameters are coupled with a decrease in sympathetic vasomotor control (-18%) and a reduction in diastolic pressure (-3.2%) in the response to the tilt test at the end of ITP. Spectral analysis could be a means of demonstrating impairment of autonomic balance for the purpose of detecting a state of fatigue that could result in overtraining.

Contributory factors to orthostatic intolerance after simulated weightlessness.

Various factors may contribute to orthostatic intolerance (OI) observed after space flights or simulated weightlessness such as bed rest experiments: individual physical and physiological factors (arterial blood pressure (BP), height), physiological changes induced by real or simulated weightlessness (hypovolaemia, increase in venous distensibility), and space flight or simulation conditions (duration and counter-measure application). Our purpose was to test which of these factors were dominant in contributing to the OI. This was assessed in 47 healthy men participating in bed rest experiments of 4, 14, 28, 30 and 42 days, with or without counter-measures (medical stockings, lower-body negative pressure (LBNP), LBNP + muscular exercise). Nineteen subjects did not finish the orthostatic test (60 degrees head-up tilt or stand test) after bed rest. The occurrence of OI was associated with greater height, low resting BP, greater changes in resting lower-limb venous distensibility throughout the bed rest, and absence of counter-measures.

[Effect of upright tilt on venous hemodynamics in rat after three-week tail suspension]. / Effet d'une mise en orthostatisme sur l'hemodynamique veineuse chez le rat apres trois semaines de suspension.

The aim of this work was to know if the venous tone measured in vivo in rat was decreased after 3-week tail suspension, a ground-based model to simulate the effects of microgravity. Arterial and venous pressure measurements during upright tilt did not show any cardiovascular deconditioning. A longer period of tail suspension appears to be necessary to induce changes in venous tone.

Venous tone and repeated +Gz accelerations.

The purpose of the present work was to study in vivo in rat the consequences of repeated exposures to sustained +Gz centrifugations on the venous pressure and on the venous tone, that one evaluated by measuring the equilibrium pressure of all vessels in the circulation when the flow is null or MCFP (mean circulatory filling pressure).

The venous tone is not altered after three-week tail suspension in rats.

Cardiovascular deconditioning observed in humans during spaceflight has been suggested to be related in part to changes in venous compliance, mechanisms including skeletal muscle deconditioning. However, increased venous compliance was observed during very short term simulations (24 to 48 hours), and during an over 28-day simulation the hyperdistensibility tended to decrease whereas the muscular changes were still present (2). In the first case, muscular changes can not explain the venous alterations because of the short delay. In the second case, the relationship between muscular and venous alterations disappeared. Finally, it is suggested that factors other than muscular ones could explain the changes in venous compliance observed during spaceflights. The fact that orthostatic hypotension has never been observed after hindlimb suspension in the rat raises issue with the use of tail-suspended rats as a valid model for the study of the mechanisms involved in cardiovascular deconditioning induced by spaceflight in humans. However, in vitro altered responsiveness of the vena cava to norepinephrine were observed in rat after spaceflight and tail suspension. The purpose of the experiments was to verify if any change occurs in venous tone measured in vivo in rats after three-week tail suspension.

Changes in leg vein filling and emptying characteristics and leg volumes during long-term head-down bed rest.

Leg venous hemodynamics [venous distensibility index (VDI), arterial flow index (AFI), half-emptying time (T1/2)], and leg volumes (LV) were assessed by mercury strain-gauge plethysmography with venous occlusion and volometry, respectively, in seven men before, during, and after 42 days of 6 degrees head-down bed rest. Results showed a high increase in VDI up to day 26 of bed rest (+50% vs. control at day 26, P < 0.05), which tended to subside thereafter (+20% increase vs. control value at day 41, P < 0.05). VDI changes were associated with parallel changes in T1/2 (+54% vs. control at day 26 of bed rest, P < 0.05, and +25% vs. control at day 41, P < 0.05) and with a decrease in AFI (-49% at day 41 vs. P < 0.05). LV continuously decreased throughout bed rest (-13% vs. control at day 41, P < 0.05) but was correlated with VDI only during the first month of bed rest. These results show that during long-term 6 degrees head-down bed rest alterations of leg venous compliance are associated with impairment of venous emptying capacities and arterial flow. Changes in skeletal muscle mass and fluid shifts may account for venous changes during the first month of bed rest but, subsequently, other physiological factors, to be determined, may also be involved in leg venous hemodynamic alterations.

Filling and emptying characteristics of lower limb venous network in athletes. Study by postural plethysmography.

Leg volume changes were assessed in healthy volunteers by mercury strain gauge postural plethysmography in order to study the effects of different types of physical training on lower limb venous distensibility and emptying. Seven endurance trained subjects (E), seven muscle strength trained subjects (M) and seven sedentary subjects (S) were submitted to a tilt table test. The test measured leg filling volumes FV (ml.100 ml-1) during 30 head-up tilt, half-emptying time T1/2 (seconds) and venous output at the 6th second of emptying (VO6) (ml.100 ml-1.min-1) during return to horizontal position. Comparative tests were made using an ANOVA test. Results showed significantly higher values for FV and VO6 in E (FV: 3.9 +/- 0.2 ml.100 ml-1 in E vs 2.5 +/- 0.2 and 2.2 +/- 0.2 ml.100 ml-1 in M and S, respectively; VO6: 9.2 +/- 1.1 ml.100 ml-1.min-1 in E vs 6.9 +/- 0.7 and 5.5 +/- 0.5 ml.100 ml-1.min-1 in M and S, respectively) whereas no significant differences were observed between groups for T1/2. M and S had the same physiological responses to orthostatic stress. Endurance training seems to increase lower limb venous distensibility without affecting venous emptying and venous return from the lower limbs. These results suggest that the greater venous distensibility in endurance-trained subjects does not result from alterations of the visco-elastic properties of deep vein walls and that it is probably a physical response to hypervolemia consecutive to chronic aerobic training.

[Vascular deconditioning (correction of deconditionring) in microgravity: results obtained in the french spationaut during the spatial mission EO 22]. / Deconditionnement vasculaire en microgravite: resultats obtenus sur la spationaute francaise au cours de la mission spatiale EO 22.

First results on changes in vascular physiology in the first french spationaut during the French-russian spatial mission CASSIOPEE are reported in this paper. The data, obtained by Air Plethysmography during flight, evidence at the level of lower limbs alterations of venous filling and emptying characteristics (the latter particularly depending on the muscular pump function of the calf) and of capillary circulation.

[PHYSIOLAB project for CASSIOPEE: the space cardiovascular exploratory laboratory]. / Projet PHYSIOLAB pour CASSIOPEE: le laboratoire d'exploration fonctionnelle cardiovasculaire de l'espace.

The French Health Defense Service is concerned by the finalization and the implementation of the PHYSIOLAB laboratory. In July 1996, PHYSIOLAB will participate to the french--russian mission CASSIOPEE. It is a functional exploratory laboratory which will support a programm of scientific experiments whose aim is to better understand cardiovascular deconditioning under weightlessness and to implement medical monitoring of cosmonauts during next french-russian space missions. In this paper, functional and scientific aims, and structure of PHYSIOLAB are described.

Plethysmography with optoelectronic sensors: comparison with mercury strain gauge plethysmography.

The study and follow-up of certain physiological adaptations in microgravity, particularly vascular and venous ones, require the use of reliable equipment that yields results well correlated with data provided by equipment usually used in clinical examinations. The purpose of the present study was to evaluate the reproducibility of results obtained using a new type of plethysmography, plethysmography with optoelectronic sensors or volometry, and to verify whether these results correlate with those yielded by mercury strain gauge plethysmography. The plethysmograph is a device which permits measuring limb volume by means of an infra-red light transmitter-receiver system that calculates cross-sectional areas at 220 successive points of a given limb segment. Calf venous capacity (calf volume measured after 50 mm Hg venous occlusion in the thigh) was measured on 27 subjects using volometry and mercury strain gauge plethysmography used as reference method. Results showed a good correlation (r = 0.8, p < 0.001) and a statistically identical reproducibility between the two methods even though venous capacity measurements obtained using these two techniques were not superimposable because they did not use the same model for limb volume measurements. Volometry therefore appears to be a technique of interest for the future, to monitor vascular and muscular physiological parameters in astronauts during long-term microgravity exposure.

Leg venous hemodynamics and leg volumes during a 42 day -6 degrees head-down bedrest.

Seven healthy subjects were submitted to a 42-day head down bedrest, where leg venous compliance (venous distensibility index VDI) and leg volumes were assessed by mercury strain gauge plethysmography with venous occlusion and optoelectronic plethysmography, respectively. Plethysmographic and volometric measurements were made, before, during (at days 1, 4, 7, 14, 21, 26, 34 and 41), and after bedrest (days 1, 4, 7, 11 and 30 of the recovery period). Results showed a continuous decrease in leg volumes throughout bedrest, when VDI increased until day 26 of bedrest, and then decreased afterwards. The recovery period was characterized by a rapid return of VDI to prebedrest levels while leg volumes progressively normalised. These results showed that leg venous compliance changes are not always dependent upon skeletal muscle changes, and that factors other than size of muscle compartment are able to determine increases in leg venous compliance during long-term bedrest.

Characteristics of the venous hemodynamics of the leg under simulated weightlessness: effects of physical exercise as countermeasure.

In order to test the hypothesis that increases in calf venous distensibility in microgravity are partly due to the changes affecting the surrounding skeletal muscles (muscular atrophy), 12 healthy volunteers were exposed for 28 d to microgravity simulated by -6 degrees head-down bed rest. Half these subjects were exposed to countermeasures during bed rest: a) repeated LBNP (Lower Body Negative Pressure) sequences starting on the 15th d with one 15 min sequence at -35 mb, every other day from the 15th until the 21st d, and then every day until the end of bed rest; b) physical training including isotonic type exercise and isometric or isokinetic work by all muscle mass of upper and lower limbs (from the 8th until the 28th d). The other six subjects forming the control group were not subjected to any countermeasure. Calf venous hemodynamics were determined by mercury strain gauge plethysmography with venous occlusion. Distensibility (delta Vmax) and venous emptying (venous outflow at the 6th s of emptying: VO6, half-emptying time: T1/2, maximum venous outflow (MVO) could also be measured. Nuclear magnetic resonance (NMR) was used to study changes in volume of calf muscles. Plethysmographic measurements made for each subject prior to, during (once a week), and after bed rest show a parallel increase in calf venous distensibility in both groups of subjects until the 20th d of bed rest. Filling and emptying times then tended to stabilize in the group treated with countermeasures (group CM) whereas high venous distensibility was observed until the end of bed rest and 5 d thereafter in the control group (group C).(ABSTRACT TRUNCATED AT 250 WORDS)

Venous distensibility and venous emptying in the legs during a 42-day -6 degrees head-down bedrest.

Exposure to actual or simulated microgravity is known to result in changes in lower limb venous compliance or distensibility which may play a role in post-bedrest or postflight orthostatic intolerance. Venous deconditioning has only been described in terms of changes in vascular compliance or distensibility. But a complete understanding of changes in venous hemodynamics and cardiovascular regulation occurring under these conditions has to take into account changes in emptying capacities of the veins which influence venous return, cardiac filling, and cardiac output regulation. Moreover, few data are available about the course of changes in venous hemodynamics for periods of simulated microgravity longer than 4 weeks. The purpose of this investigation was to measure parameters of venous compliance and venous emptying before, during, and after a 42-day period of bedrest at -6 degrees head-down tilt for a better understanding of long term venous physiological adaptation to microgravity.

Leg vein hemodynamics during bedrests simulating lunar trip.

When contemplating future trips to the Moon whose gravity is one sixth of Earth gravity, the question is to know what the adaptive changes in the lower limb venous system would be. In fact, one can suppose that the presence of a partial gravity on the Moon would be able to attenuate venous hemodynamics adaptative changes observed in microgravity. In the present experiment changes in the venous hemodynamics of lower limbs have been studied with mercury strain gauge plethysmography during a simulated Moon mission including a 4 day trip to the Moon (-6 degrees bedrest), a stay of 6 days on the Moon (+11 degrees bedrest), and a 4-day trip back to Earth (-6 degrees bedrest). It was previously demonstrated that +11 degrees bedrest was a good model to simulate the effects of lunar gravity on the cardiovascular system (Vernikos-Danellis J 1986, personnal communication).

Effects of LBNP + specific physical exercises on leg venous hemodynamics during a 28-days -6 degrees head-down bedrest.

The mechanisms underlying increased venous distensibility during exposure to microgravity are not well known yet. However, there seems to be evidence indicating that skeletal muscle changes resulting from exposure to microgravity play a very important role. The purpose of this experiment was to test the hypothesis that leg muscles could play an important role in the changes of leg venous distensibility observed in simulated microgravity. Twelve subjects were submitted for 28 days to a -6 degrees head-down bedrest. Changes in leg vein hemodynamics (filling and emptying) have been measured by mercury strain gauge plethysmography with venous occlusion. Six of these subjects trained their lower limbs with isometric and isokinetic exercises during bedrest (group CM), while the other 6 subjects (control group, C) had no training.