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Biomedical subjects

L Laurencelle

Publications and source records attributed to L Laurencelle.

18 recordsLinked to original sources
PubMed1990

Hematological variations at rest and during maximal and submaximal exercise in a cold (0 degree C) environment.

The affect of negative thermal stress on hematological variables at rest, and during submaximal (sub ex) and maximal exercise (max ex) were observed for young males who volunteered in two experimental sessions, performed in cold (0 degree C) and in normal room temperature (20 degrees C). At rest, hematological variables such as RBC and derivates Hb and Hct were significantly increased (P less than 0.05) during cold stress exposure, while plasma volume decreased. The findings of this study suggest that the major factor inducing hypovolemia during low thermal stress can be imputed to local plasma water-shift mechanisms and especially to a transient shift of plasma water from intra- to extravascular compartments. Rest values for WBC and platelets (Pla) were also slightly increased during cold stress exposure. However this increase can partly be related to hemoconcentration but also to the cold induced hyperventilation activating the lung circulation. Maximal exhaustive exercise induced, in both experimental temperatures, significant (P less than 0.05) increments of RBC, Hb, Hct, and WBC while plasma volume decreased. However, Pla increase was less marked. On the other hand, cold stress raised slightly the observed variations of the different hematological variables. Submaximal exercise induced a similar, though non-significant, pattern for the different hematological variables in both experimental conditions. Observed plasma volume (delta PV%) reduction appears during exercise. However cold stress induced resting plasma volume variations that are transferred at every exercise level. Neither exercise nor cold inducement significantly modified the hematological indices (MCH, MCV, MCHC). In conclusion hematological variables are affected by cold stress exposure, even when subjects perform a physical activity.

Acclimatization↗
PubMed1990

Physiological adjustments of facial cooling during exercise.

Physiological and metabolic output responses to facial cooling during a graded maximal exercise and a prolonged submaximal exercise lasting 30 min at 65% VO2 max were investigated in five male subjects. Pedalling on a cycle ergometer was performed both with and without facial cooling (10 degrees C, 4.6 M.S-1). Facial cooling at the end of greated maximal exercise apparently had no effect on plasma lactate (LA), maximal oxygen consumption (VO2 max), maximal heart rate (HR max), rectal temperature (Tre), work load, lactate threshold (LT), ventilatory threshold (VT) and onset of blood lactate accumulation (OBLA). However, the response to facial cooling after prolonged submaximal exercise is significantly different for heart rate and work load. The results suggest that facial wind stimulation during maximal exercise does not produce a stress high enough to alter the metabolic and physiological responses.

Adaptation, Physiological↗
PubMed1989

Metabolic and hormonal responses during exercise at 20 degrees, 0 degrees and -20 degrees C.

This study was designed to clarify the effects of cold air exposure on metabolic and hormonal responses during progressive incremental exercise. Eight healthy males volunteered for the study. Informed consent was obtained from every participant. The following protocol was administered to each subject on three occasions in a climatic chamber in which the temperature was 20 degrees, 0 degree or -20 degrees C with relative humidity at 60% +/- 1%. Exercise tests were conducted on an electrically braked ergocycle, and consisted of a progressive incremental maximal exercise. Respiratory parameters were continuously monitored by an automated open-circuit sampling system. Exercise blood lactate (LA), free fatty acids (FFA), glucose levels, bicarbonate concentration (HCO-3), acid-base balance, plasma epinephrine (E) and norepinephrine (NE) were determined from venous blood samples obtained through an indwelling brachial catheter. Maximal oxygen uptake was significantly different between conditions: 72.0 +/- 5.4 ml kg-1 min-1 at 20 degrees C; 68.9 +/- 5.1 ml kg-1 min-1 at 0 degree C and 68.5 +/- 4.6 ml kg-1 min-1 at -20 degrees C. Workload, time to exhaustion, glucose levels and rectal temperature decreased significantly at -20 degrees C. Catecholamines and lactate values were not significantly altered by thermal conditions after maximal exercise but the catecholamines were decreased during rest. Bicarbonate, respiratory quotient, lactate and ventilatory thresholds increased significantly at -20 degrees C. The data support the contention that metabolic and hormonal responses following progressive incremental exercise are altered by cold exposure and they indicate a marked decrease in maximal oxygen uptake, time to exhaustion and workload.

Adult↗
PubMed1989

Effects of selective cooling of the facial area on physiological and metabolic output during graded maximal or prolonged submaximal exercise.

Physiological and metabolic output responses to facial cooling during a graded maximal exercise and a prolonged submaximal exercise lasting 30 min at 65% VO2 max were investigated in five male subjects. Pedalling on a cycle ergometer was performed both with and without facial cooling (10 degrees C, 4.6 m s-1). Facial cooling at the end of graded maximal exercise apparently had no effect on plasma lactate (LA), maximal oxygen consumption (VO2 max), maximal heart rate (HR max), rectal temperature (Tre), work-load, lactate threshold (LT), ventilatory threshold (VT) and onset of blood lactate accumulation (OBLA). However, the response to facial cooling after prolonged submaximal exercise is significantly different for heart rate and work-load. The results suggest that facial wind stimulation during maximal exercise does not produce a stress high enough to alter the metabolic and physiological responses.

Adult↗
PubMed1989

Decision making in sport: the effect of stimulus-response probability on the performance of a coincidence-anticipation task.

The purpose of the present study was to evaluate the quality of a motor response for different levels of expectancy and time constraint, in a two-choice coincidence-anticipation task. The probability of each of the two events likely to be presented were varied across different levels as well as the speed of the stimulus to be intercepted. The results indicated that neither the choice reaction time (CRT) and movement time, nor the performance of coincidence-anticipation were affected by the probability of the stimulus for the low and moderate stimulus speeds. However, when the stimulus traveled at a high speed a trade-off took place. The CRT decreased as the probability of the event increased, whilst the proportion of response initiation errors increased for the low probability events. This trade-off resulted in a better coincidence-anticipation as the probability of the event increased. The results obtained in the present experiment are clearly different from those obtained in a classic CRT-deadline paradigm, in that the trade-off observed between CRT and response initiation errors was far less pronounced in the coincidence-anticipation task. This difference was attributed to the higher negative consequences associated with a response initiation error in a coincidence-anticipation task. It is thus concluded that the tasks used to study the nature of the decision processes taking place in sports and sports-like situations must have some ecological validity to be of some help for the practitioner.

Adult↗
PubMed1988

Extent and limits of cerebral adjustment to early section or congenital absence of the corpus callosum.

The ability to effect inter- and intrahemispheric comparisons of visual and tactile stimuli was studied in 4 callosotomized patients and 6 callosal agenesis subjects using response accuracy and response times to determine the extent of cerebral adjustment to functional or congenital absence of the corpus callosum. The visual tasks involved within- and between-fields presentation of pairs of colours and shapes. The tactile tasks required uni- and bimanual comparisons of 3 categories of stimuli (size, shape and texture) of increasing difficulty. Older callosotomized children showed disconnection deficits similar to those reported in adult split-brain patients, whereas both acallosal subjects and our youngest patient with complete callosal transection demonstrated a high level of accuracy in the interhemispheric tasks. However, all patients required considerably more time to accomplish the cross-integration of relatively complex visual and tactile information which seems to be one of the major limitations of the compensatory mechanisms. The results also indicate that the quality of transfer differs between the acallosal and early-callosotomized patients in relation to the sensory modality studied. Thus, visual cross-matching was found to be superior to bimanual matching for the callosotomized group, whereas intermanual comparisons proved to be more efficient than visual integration in the acallosals. These divergent findings suggest not only that different compensatory mechanisms may be operating in visual and tactile transfer, but also that the same mechanisms may be utilized differently by the two populations deprived of the use of callosal connections.

Adolescent↗
PubMed1988

Lactate threshold and onset of blood lactate accumulation during incremental exercise after dietary modifications.

This study was designed to clarify the effects of dietary modifications on the lactate threshold (LT) and on the onset of blood lactate accumulation (OBLA) during progressive incremental exercise. Six healthy males volunteered for the study. Informed consent was obtained from every participant. The following protocol was administered to each subject on three occasions: a 48-h period of mixed dieting (53% carbohydrates, 30% lipids, 17% proteins) preceding the first exercise test, immediately followed by a 48-h period of either a carbohydrate-rich (68% CHO, 23% lipids, 9% proteins) or a fat-rich (19% CHO, 57% lipids, 26% proteins) iso-caloric diet leading to the second exercise and separated from the third test by a 12-days period. Exercise tests were conducted on an electrically-braked ergocycle, and consisted of a progressive incremental maximal exercise. Respiratory parameters were continuously monitored by an automated open circuit sampling system. Exercise blood lactate (LA), free fatty acids (FFA), glucose levels and acid-base balance were determined from venous blood samples obtained through an indwelling brachial catheter. Peak lactate values, workload and performance time were not significantly altered by imposed diets. Furthermore, dietary modifications had no significant effect on LT, OBLA fixed at 4 mmol and ventilatory threshold. Increased pH and FFA mobilization were observed with fat-rich diet, while CHO-rich diet markedly increased the respiratory exchange ratio (R). It is concluded that LT and OBLA are not significantly altered by fat or CHO enrichment of diets.

Adult↗
PubMed1988

[Protection of the eyes in racket sports].

A survey was conducted on 1032 racket sport players from 10 randomly selected racket sport centers in Quebec during the month of October 1985. The use of protective eye glasses was found to be higher in racketball (70.2%) and squash (45.8%) than in badminton (8.8%) or tennis (3.5%). While a little less than 60% of protective eye glasses were equipped with unbreakable lenses, 40% of protective glasses were simple eye guards, containing no lens at all. Hence a large number of players assumed that they had adequate protection while wearing simple eye guards or their everyday normal glasses. Gender differences did not seem to affect the use of protective eye glasses. A general observation was that the older the player the better the eye protection, whereas novice players tended to be less prepared to use the protective glasses. The use of protective eye glasses was found to be compulsory in close to 46% of racketball centers and in 25% of squash clubs.

Adolescent↗
PubMed1983

[Decision strategy as a function of event probability: 2. Latency of the decision and covering the field].

A fair number of studies have been conducted in order to assess the effect of event probability on decision strategy in a two choice reaction time (CRT) task. Results showed that increasing the probability of an event from 0.5 to 0.8 did not affect CRT. In fact, a significant decrease in CRT was obtained only when one of the two stimuli reached a probability of 0.9. It was concluded from these studies that subjects used a very conservative decision strategy. It should be pointed out that in these studies the instructions given to subjects emphasized both speed and accuracy of response. In many sport situations however, a player must choose speed of response over accuracy. For example the tennis player who knows that the opponent will smash the ball either to his right or hs left. The purpose of the present study was to determine whether or not in such situations the defensive player might not choose a less conservative decision strategy than that presented earlier. Fourteen subjects were submitted to a two CRT task, where the probability of each event and the time allotted (TA) to complete the appropriate response were systematically manipulated. The results obtained for each level of TA were similar to those discussed earlier. More specifically, a significant decrease in CRT was obtained only when one of the two possible events reaches a probability of 0.9. However, it appeared that, reducing TA forced subjects to reduce CRT and to base their responses more and more on anticipation than on reaction.

Decision Making↗
PubMed1983

[Decision strategy: effect of probability of the results and of the allowed time on choice reaction time and on movement time].

In many sport activities, the speed with which a performer can complete the required response is an important determinant of performance. In order to minimize this time an individual can initiate and execute the response faster. A number of studies (Alain & Proteau, 1977; Proteau & Dugas, 1982; Régnier & Salmela, 1980) in which individual was to move for two meters in a choice reaction time task have shown that, when the probability of one of the two events was 0,9, the movement time (MT) was significantly reduced. The results may perhaps be explained by the fact that subjects shifted their weight during the foreperiod (FP) preceding the stimulus and then facilitated the movement execution (reflected by a lower MT). The present experiment was designed to test the second possibility. Subjects initiated their responses from a dynamographic platform. The independent variables were the probabilities of the two events and the time allowed for subjects to complete the response. Results indicated that when the probability of one of the two events was sufficiently high (0,9), subjects did shift their weight during the FP in order to produce a faster response. The results supported the fact that subjects, in sport like situations, prepare themselves, at least partially, but only when the probability of the event is very high.

Decision Making↗