Haemodynamic changes induced by submaximal exercise before a dive and its consequences on bubble formation

Objectives

To evaluate the effects of a submaximal exercise performed 2 h before a simulated dive on bubble formation and to observe the haemodynamic changes and their influence on bubble formation.

Participants and methods

16 trained divers were compressed in a hyperbaric chamber to 400 kPa for 30 min and decompressed at a rate of 100 kPa/min with a 9 min stop at 130 kPa (French Navy MN90 procedure). Each diver performed two dives 3 days apart, one without exercise and one with exercise before the dive. All participants performed a 40 min constant‐load submaximal and calibrated exercise, which consisted of outdoor running 2 h before the dive. Circulating bubbles were detected with a precordial Doppler at 30, 60 and 90 min after surfacing. Haemodynamic changes were evaluated with Doppler echocardiography.

Results

A single bout of strenuous exercise 2 h before a simulated dive significantly reduced circulating bubbles. Post‐exercise hypotension (PEH) was observed after exercise with reductions in diastolic and mean blood pressure (DBP and MBP), but total peripheral resistance was unchanged. Stroke volume was reduced, whereas cardiac output was unchanged. Simulated diving caused a similar reduction in cardiac output independent of pre‐dive exercise, suggesting that pre‐dive exercise only changed DBP and MBP caused by reduced stroke volume.

Conclusion

A single bout of strenuous exercise 2 h before a dive significantly reduced the number of bubbles in the right heart of divers and protected them from decompression sickness. Declining stroke volume and moderate dehydration induced by a pre‐dive exercise might influence inert gas load and bubble formation.Decompression sickness (DCS) is caused by circulating bubbles of inert gas in blood and tissues resulting from supersaturation during decompression. As exercise may increase the production of bubbles due to mechanical movement of body structures, intense physical exercise before diving has long been considered an additional risk factor for DCS.¹ Recently, several studies have indicated that this notion needs updating. It has been reported that exercise training weeks before dives could reduce the incidence of neurological DCS in pigs² and rats.³ Doppler‐detected venous gas emboli (VGE) are widely used as an indicator of decompression stress in man. Although bubbles are frequent after symptom‐free dives, the occurrence of many bubbles is clearly linked to a high risk of DCS.⁴ It has been demonstrated that aerobically trained runners seemed to be at lower risk for venous bubbling than sedentary participants.⁵ Moreover, recent studies in rats have shown that a single bout of high‐intensity exercise 20 h before a simulated dive reduced bubble formation and prevented death, with no effect at any other time—that is 48, 10, 5 and 0.5 h before the dive.^6,7 A human study supported these animal data, in which 12 divers performed a single bout of submaximal aerobic exercise 24 h before a simulated dive.⁸ It is speculated that the main mechanism of exercise‐induced suppression of bubble formation could be related to nitric oxide (NO) production.^6,9 However, it is not clear why this effect could be seen only within a window approximately 24 h before the dive. In fact, we have previously shown in a study of 16 divers that a short pre‐dive latency with a submaximal exercise performed 2 h before a simulated dive can also be protective.¹⁰ This work aims to confirm the previous study with a well‐calibrated exercise. After reviewing the current hypothesis, this report is the first to suggest that haemodynamic changes and moderate dehydration induced by a pre‐dive exercise might influence inert gas load and bubble formation.     

Plongée à l'air avec la table de décompression MN 90. Bilan de 12 années d'utilisation par la Marine française : à propos de 61 accidents de désaturation de 1990 à 2002

Objective. – Decompression MN 90 Table is used for air diving by military divers and both sports divers in France. In the aim to confirm MN 90 safety, we studied 61 decompression sicknesses observed in the French Navy for 1990–2002.Method. – Each year 1800 divers carry out 150 000 dives ± 10%. Divers are 1600 ship divers (dives less than 35 m-sub-water) and 200 mine clearance divers (dives up to 60 msw max). Each accident must be notified and data are recorded into a database.Results. – The total risk is estimated at 1 accident/30 000 dives. We observed no death and only 2 divers with persistent neurological deficits. We found spinal decompression sickness: 66%, cerebral 23%, inner ear 8% and joint bends 3%. Neurological accidents are purely sensitive for 65%. The evolution was favourable for 97% after early hyperbaric recompression at 400 kPa. One hundred percent respected the MN90 procedure. Water temperature, age, effort during diving, repetitive dive were not found as risk factors. A right-to-left shunt was present for only 30% of type II accident. The main result of the study is that 54% of accidents concerned only 200 mine clearance divers with a risk estimated at 1 accident/3000 dives for 45–60 msw depths.Conclusion. – MN90 decompression procedure is safe for a young population of trained military divers with a low risk of accident. The major risk factor seems to be the depth. Studies are necessary to optimize the decompression for deep air diving.     

Effet d'un entraînement en endurance sur les concentrations de l'IGF-1 plasmatique chez le rat

Introduction

The aim of this study was to determine the effects of endurance training on IGF-1, corticosterone and insulin levels in male sedentary and trained rats.

Facts

IGF-1 concentrations decrease after training (p < 0.05), those of corticosterone increase (p < 0.01) whereas insulin levels remain stable.

Conclusion

A short period of endurance training leads to catabolic state with a decrease in IGF-1 concentrations and increase in corticosterone levels.     

Évolution chez l'homme de l'Insulin-Like Growth Factor-I dans le liquide interstitiel musculaire suite à un exercice en résistance

Introduction

The impact of resistance exercise on the growth of the vastus lateralis was assessed through interstitial microdialysis measurement of free Insulin-like Growth Factor-I at +3 h30, +4 h50 and +6 h after exercise in 4 healthy subjects.

Results

We observed 3 h30 after exercise an interstitial increase in 3 over 4 subjects, and thereafter a progressive decrease. In the mean time, free or total plasma concentrations did not change.

Conclusion

Resistance exercise seemed to induce an early increase of muscle interstitial free Insulin-like Growth Factor-I in order to initiate muscle growth by an autocrine – paracrine way.     

Diving-induced venous gas emboli do not increase pulmonary artery pressure

Venous gas emboli are frequently observed in divers even if proper decompression procedures are followed. This study was initiated to determine if pulmonary artery pressure increases in asymptomatic divers, which could increase the risk of arterial embolization due to passage of venous gas emboli from the right to the left side of the heart. Recordings of venous gas emboli and estimation of pulmonary artery pressure by non-invasive transthoracic echocardiography were applied in 10 recreational scuba diving volunteers before and 20, 40, 60, and 80 min after simulated dives to 18 m (80 min bottom time) in a hyperbaric chamber. The ratio between pulmonary artery acceleration time and right ventricular ejection time was used as an estimate of pulmonary artery pressure. None of investigated divers had signs of decompression sickness. Despite the post-dive presence of the venous gas emboli, measured in the region of the pulmonary valve annulus (mean=1.71 bubbles.cm-2, 40 min after dive), the ratio between pulmonary artery acceleration time and right ventricular ejection time did not decrease, but actually increased (from 0.43+/-0.06 to 0.49+/-0.06, 40 min after dive; p<0.05), suggesting a decrease in pulmonary artery pressure after the dive. We conclude that diving-induced venous gas bubbles do not cause significant changes in the central circulation which could increase the risk of arterial embolization.     

Analyse de variables permettant la détermination du niveau d'un cycliste

Aims

We aimed to define a mathematical model allowing to foresee the level of a cyclist.

Methods

One hundred (and) six cyclists were classified according to their level and some of their physiological characteristics were measured with the threshold (4 mmol of lactate) and with the maximum values of their oxygen flow.

Results

To the threshold, power, lactatemy, age and size allow to foresee the level with an error rate of 27% ; to the maximum values, the criteria are development, flow in oxygen, lactatemy and age (error rate of 31%).

Conclusion

These results indicate that our mathematical model allows to envisage the level.     

Administration de courte durée de prednisolone et sécrétion d'érythropoïétine

Introduction

The aim of the study is to assess the effects of a short-term therapeutical prednisolone intake on erythropoietin (EPO) secretion.

Synthesis

We studied, according to a double-blind, randomized cross-over protocol, the effects of a 7 day prednisolone intake (60 mg/day) in 10 healthy male subjects on hematocrit, EPO and hemoglobin concentrations. No significant change was found between the treatments (prednisolone/placebo) in the parameters investigated.

Conclusion

In view of the results obtained, short-term therapeutic glucocorticoid intake did not induce any enhancement of erythropoiesis via EPO stimulation that can result in ergogenic advantage during submaximal exercise.     

Propriétés psychométriques d'un questionnaire de mesure de l'activité physique chez l'enfant scolarisé âgé de six à dix ans : QAPE-semaine

Aims

To elaborate a physical activity questionnaire for school children aged between 6 and 10 years (QAPE-semaine) and to study the psychometric properties (face validity, acceptability, test-retest reproducibility, criterion validity).

Methods

The questionnaire measures physical activities at school, during leisure-time and other activities. Three scores are calculated: variety of physical activities, intensity and sedentary. The questionnaire was pre-tested to study the content validity, and was administered twice to 185 children from two elementary schools. The validity was studied by comparing the results of the questionnaire outcomes with a one day-recall (QAPE-hier) filled out in two occasions (to measure activities during a non school-day and a school-day). The statistic used was the intraclass correlation coefficient (ICC).

Results

The QAPE-semaine was acceptable. The ICC for the reproducibility of variety of physical activities, intensity and sedentary scores were 0.54, 0.47 and 0.68, respectively; and 0.54, 0.56 and 0.64 for the criterion validity of variety of physical activities, intensity and sedentary scores, respectively. All the ICC were significant (P < 0.0001).

Conclusion

The psychometric properties of the QAPE-semaine are satisfactory (moderate to good). Its administration in classes with school professor's help seems however essential.     

Traumatismes de l'épaule chez les joueurs français de rugby de haut niveau

Aim of the study

Specify the frequency and the type of injuries of the shoulder arising during the practice of professional rugby in France. Outcomes were studied according to the treatments performed.

Materials and methods

It is a matter of a retrospective study on 154 players of high level. Any shoulder injury endured during the practice of rugby was registered. The age of the player, his experience, his position on the field, the type of injury, the game phase, the treatment and eventual residual disability were specified.

Results

Ninety-eight players (64%) reported at least one injury of the shoulder. Thirty (19%) reported at least two injuries on the same shoulder. The acromio-clavicular joint injuries were the most frequent (49%). The treatment was medical in most of the cases. A rest of 17 days in average was noted. All the players came back to their better level. Instability of the gleno-humeral joint was retrieved by 15% of the players. A secondary treatment by surgical stabilization was noted in more than half of the cases. The rest was in average of one week after the injury. It was in average of 4 months after surgery. A significant persistent discomfort was retrieved by 43% of the non operated cases and by 27% of the operated cases.Different other injuries were noted: 17 clavicular fractures, 6 sterno-clavicular sprains, 5 rotator cuff injuries and 4 muscular contusions.

Discussion

Injuries of the shoulder are frequent among high level rugby players and represent an important source of morbidity. Injuries of the acromio-clavicular joint are the most frequent. The medical treatment allows a quick return to sport without level loss in mostly cases. Gleno-humeral instability represents the second traumatism in terms of frequency. A secondary treatment by surgical stabilization is preferable.     

L’utilisation d’un nouveau système d’enregistrement de fréquence cardiaque battement à battement pour l’analyse traditionnelle de variabilité de fréquence cardiaque

Introduction

The measurement of Heart Rate Variability (HRV) is widely used in the field of sport's sciences. However, the analysis which rises from these measurements requires equipment that conform to those conditions outlined by the Task force of 1996.

Purpose

The purpose of the present study was: 1) to determine the accuracy of a new heart rate “beat to beat” recorder; Polar RS 800 (Polar Electro Oy, Kempele, Finlande); 2) and whether the quality of the tachogram is sufficient for traditional analysis of HRV.

Device and methods

Heart rate was recorded on 15 persons (eight men, seven women) in three different situations, simultaneous with this device and a gold standard (ADInstruments, Castle Hill, Australia, else Novacor, Rueil-Malmaison, France). Signals are synchronized and compared with Bland and Altman method to asses the accuracy. HRV analysis is made and the same comparison method was applied.

Conclusion

This device enables measurements of R-R intervals with a precision of ± 1 to 5 ms, and is sufficient to analyse HRV without bias.     

Effet du port d'une combinaison intégrale et d'une trifonction sur la vitesse de nage et l'amplitude du cycle de bras en triathlon

Introduction

The purpose of this study was to compare the influence of complete wetsuit and tri-function on the swimming speed and arm stroke characteristics in crawl by triathletes.

Synthesis

Seven triathletes have executed three randomised trials of 400 m front crawl at maximal intensity: without wetsuit, complete wetsuit and tri-function.

Conclusion

Results pointed out that the complete suit allows a significant improvement of the performance and of the distance per cycle by report the swimming with a tri-function.     

Observance du suivi médical obligatoire par les sportifs de haut niveau lorrains

Objectives

To measure high level athletes' level of compliance of their medical follow-up (in reference to the French law) and exploring their perception of it.

Method

Data were collected by self-questionnaire among the 614 high level athletes in the Lorraine region (East of France).

Main results

Response rate was 66.8%. In 2006, approximately a third of the athletes did not benefit from the two medical examinations carried out by a sport doctor. The great majority did benefit neither from dietetic assessment, nor of nutritional council. More than half of them stated that they had no psychological assessment. An athlete on five said that he did not have an electrocardiogram. All of these exams or assessments are however obligatory according to the French law. In 5% of the cases, the follow-up detected a health problem, generally a cardiac anomaly. The majority of the athletes felt that the follow-up was not a waste of time, not very constraining and that it was complete. Their positions were doubtful on its capacities to prevent wounds or to improve sporting performances.

Conclusion

A nation-wide study should be undertaken to check these worrying results in France.     

Effets d'une complémentation nutritionnelle en vitamines et minéraux sur la chute de force et les marqueurs biologiques consécutifs à un exercice excentrique chez des personnes âgées

Purpose

The effects of vitamins and minerals complex supplementation on maximal voluntary contraction decrease (FMV) and biological markers following an eccentric exercise at old people.

Method

Sixteen elderly subjects took either placebo (Pl group) or vitamins and minerals (Isoxan Senior, NHS, Rungis, France) (group S) for 21 d before an eccentric exercise and for 3 d after the exercise. The FMV and surface EMG activity (RMS) of the vastus lateralis (VL), vastus médialis (VM) and rectus fémoris (RF) were recorded before (Pre), immediately after (Post), 24 h (Post 24) and 48 h (Post 48) after the exercise. CCVThe creatine kinase (CK), lactate déshydrogénase, malondialdéhyde, and tumor necrosis Factor (TNFα) levels were analyzed.

Results

The reduced MVC (S: 11,2 ± 4,8%; Pl: 17,8 ± 10,4%, P < 0,01) after exercise was associated with a significant reduction in RMS VL, RMS VM and RMS RF values for both groups. A faster FMV recovery appeared at 48 h for the S group (P < 0.05). CK and TNFα values increased in post-exercise.

Conclusion

A dietary supplementation of a vitamin and mineral complex does not attenuate the loss of contractile function immediately after the running exercise, and it may accelerate the recovery of maximal force capacity after 48 h by limiting the post-exercise pro-inflammatory processes.     

Comparative data from 2250 male and female sports divers: diving patterns and decompression sickness

BACKGROUND: The aim of the study was to compare the diving habits and histories of men and women in recreational scuba diving. METHODS: More than 10,000 questionnaires were circulated to recreational divers in the United Kingdom. Retrospective, broad-based information was requested concerning general health, smoking, alcohol, recreational drug use, diving habits and histories, and physician-confirmed and self-diagnosed episodes of decompression sickness (DCS). Data relating only to women were also gathered. Questionnaires were anonymous. RESULTS: Over four years, 2250 divers responded, 47% of whom were women. Of the 458,827 dives reported, 310% were by women. Differences in diving habits were observed between men and women, which included number of dives per annum, maximum depths dived, and dives with extra stops. When the level of experience was taken into account in this study group, the estimated rate of DCS in men was 2.60 times greater than for women. CONCLUSIONS: In this study, comparison between men and women in recreational diving differed from the initial evaluation when underlying factors were taken into account. Future studies should attempt to control for underlying factors in the data gathering and data analysis.     

Effets d'une restriction hydrique et alimentaire prolongée (ramadan) sur la performance et les réponses cardiovasculaires au cours d'un exercice incrémental en milieu tropical chaud

Backgroung

Previous studies showed that maximal oxygen uptake and maximal heart rate were not different during prolonged fasting (ramadan) compared to normal feeding period. However, the effect of ramadan on the blood pressure response during incremental exercise has not been investigated.

Objective

This study aimed to evaluate the evolution of blood pressure during incremental trial in ramadan period.

Methods

Twelve young trained male aged 24 ± 4 yrs participated as voluntary subjects. Their anthropometric parameters, maximal aerobic power and maximal heart were measured in fasting and in normal feeding periods during incremental trial on cycle ergometer.

Results

No significant difference was observed in any anthropometric parameter. Maximal aerobic power of fasting period was significantly less (P < 0,05) compared to normal feeding. Heart rate at rest, at maximal exercise and during a 15 min period of recovery was not significantly affected. Systolic blood pressure of fasting period at maximal power was significantly lower than during the control period (P < 0,05).

Conclusion

Ramadan negatively influences the capacity of maximal power and cardiovascular response at maximal power.     

Clinical observation: Beau's lines on fingernails after deep saturation dives.

Transverse furrows, or Beau's lines, were noted in the fingernails of all 6 divers following a deep saturation dive to apressure equal to 1100 feet (335 meters) ofsea water (3,370 kPa), and in 2 of6 divers following a similar dive to 1000 feet (305 meters) of sea water (3,164 kPa). Both dives took place at the Ocean Simulation Facility of the Navy Experimental Diving Unit in Panama City, Florida. The divers breathed a partial pressure of 0.40 - 0.44 atm abs (40.5 - 44.6 kPa) oxygen, with the balance helium, during most of the time under pressure. All divers performed hard work on bicycle ergometers during the dives. Four of the divers on the first dive were treated during the dive for pain-only decompression sickness. Beau's lines have been reported in numerous medical conditions such as typhus, rheumatic fever, malaria, myocardial infarction, and other severe metabolic stresses. To the author's knowledge this is the first report of Beau's lines associated with saturation diving.     

Analyse de l'électrocardiogramme et de l'échocardiographie de 181 footballeurs professionnels tunisiens

Objectives

The aim of our work was to determine the frequency of various cardiovascular abnormalities and atypical aspects observed in Tunisian competitive athletes.

Material and methods

Our population was constituted of 181 professional football players (average age 23.1 ± 3.9 years) consulted in “Centre National de la Médecine et des Sciences de Sport” of Tunis with to obtain medical certificate authorizing professional football practice.

Results

Electrocardiogram was strictly normal in 67 players (37%). Twenty-nine players had conduction abnormalities. Repolarisation abnormalities were noted in 20 players. Echocardiography was normal in 129 players (71.3%). Ten cases of valvular heart disease were found. The mean left ventricular end-diastolic diameter was 53 ± 4 mm and the mean left ventricular mass was 202.6 ± 42.7 g. The mean relative wall thickness was 0.380. The left ventricular hypertrophy was present in 42 players.

Conclusion

Cardiovascular abnormalities found in electrocardiogram and echocardiography in the Tunisian professional football players are comparable with those usually observed in elite athletes.     

Blood biochemical parameters in women during long-term simulated hyperoxic diving up to 8 ATA.

Nowadays an increasing number of women are participating in recreational diving. A special recompression treatment table for delayed pulmonary barotrauma or decompression sickness was developed by V.V. Smolin in the Institute for Biomedical Problems (IBMP, Russia). The aim of our study was to investigate the effect of simulated dives (similar to this recompression treatment table) on biochemical parameters of healthy women. Three healthy female volunteers participated in long-term simulated diving to 8 ATA (0.8 MPa). Blood samples for determination of the biochemical substrate levels and activity of blood enzymes using a Reflotron analyzer were obtained at the control period, at the beginning of decompression and at the post dive period. No significant changes of serum levels of glucose, triglycerides, cholesterol, HDL cholesterol and urea were found during this experimental period or in comparison with the predive values. There were no significant changes in ALT activity in two volunteers but there was some tendency for an insignificant decrease in AST activity. One of the volunteers had a considerable increase in AST and ALT activities 15 h after the dive, probably due to a modified diet outside the experiment conditions. Thus, the long-term simulated diving recompression treatment table did not lead to a shift in the woman's serum biochemical status. However, it remains necessary to consider probable dysfunction of liver due to hyperbaric exposure.     

Field trials of no-decompression stop limits for diving at 3500 m

INTRODUCTION: In 1990, Bo?azi?i University (Istanbul, Turkey) launched an altitude diving program to develop techniques and safe decompression profiles for diving at high terrestrial altitudes. Following pioneering diving expeditions to lakes at high elevations in 1990-1992, it was deemed necessary to calculate new tables. METHODS: Bottom time limits for dives requiring no decompression stops (no-d) were calculated for 3500 m using linear extrapolation of U.S. Navy M-values decreased by 4 ft of sea water (M4 limits). These limits were tested for 15, 18, 21, 24, 27, and 30 m of depth by diving in the Great Sea Lake at Mt Ka?kar (3412 m) with 10 dives per profile. RESULTS: The mean decompression sickness (DCS) risk estimated from precordial bubble scores (Spencer Scale) ranged from 0.3% to 2.8% per profile. After three expeditions, 165 dives had been achieved with a cumulative bottom time of 3199 min. No DCS occurred in dives that adhered to the M4 no-d limits. However, two cases of Type I and one case of Type II DCS were encountered where the divers accidentally exceeded those limits. DISCUSSION: Considering the estimated risk of DCS and the relatively small number of trials, a more conservative approach was used to develop a final set of high altitude dive tables. This conclusive approach used continuous compartment half-lives. It is based on fitting a surface of allowable supersaturation limits using the empirical M-values from existing tables as well as our altitude diving data, together with an added constraint that forces calculated M-values to stay below the available M-value data.