Time to exhaustion at VO(2)max is related to the lactate exchange and removal abilities.

The aim of the present study was to investigate the relationships between lactate exchange and removal abilities and the capacity to prolong exercise, as assessed by the time to exhaustion (Tlim) at a work rate corresponding to VO(2)max (Pa max ). The individual blood lactate recovery curves obtained for 13 untrained subjects after 5 min 90 % Pa max exercise were fitted to the biexponential time function: La(t) = La(0) + A(1) (1-e (-gamma(1) x t) + A(2) (1-e (-gamma(2) x t), where t is time into the recovery, La(0) is the arterialized lactate concentration measured at the end of the exercise, gamma(1) and gamma(2) are velocity constants denoting the lactate exchange and removal abilities, respectively. Tlim was positively related to gamma(1) and gamma(2) (r = 0.60, p < 0.05 and r = 0.56, p < 0.05, respectively) but was negatively related to La(0) (r = 0.75, p < 0.01). gamma()1 was positively related to the capillary density (r = 0.69, p < 0.01) and to the number of capillaries per type I fiber area (r = 0.62, p < 0.05). It was concluded that 1) high lactate exchange and removal abilities would allow continuing a high-intensity exercise for a longer duration, and 2) a high capillary density may explain the associated high lactate exchange ability.

Effect of hyperoxia on aerobic and anaerobic performances and muscle metabolism during maximal cycling exercise.

The hyperoxia-improved tolerance to maximal aerobic performance was studied in relation to exercising muscle metabolic state. Five students were submitted to four different tests on a cycle ergometer, each being conducted under normoxia and hyperoxia (60% FiO2) on separate days: Test 1, a progressive exercise until exhaustion to determine the maximal work load (Wmax) which was unchanged by hyperoxia; Test 2, an exercise at Wmax (287 +/- 12 W) until exhaustion to determine the performance time (texh) which was elevated by 38% under hyperoxia but exhaustion occurred at the same arterial proton and lactate concentrations; Test 3 (S-Exercise test) consisted of cycling at Wmax for 90% normoxic-texh (4.8 +/- 0.5 min under both O2 conditions) then followed by a 10-s sprint bout during which the total work output (Wtot) was determined; Wtot was elevated by 15% when exercising under hyperoxia; Test 4 (M-Exercise test) consisted also of cycling at Wmax for 4.8 +/- 0.5 min with blood and muscle samples taken at rest and at the end of the exercise to compare the level of different metabolites. During hyperoxic M-Exercise test, glycogen was twice more depleted whereas glucose-6-phosphate and lactate were less accumulated when compared with normoxia. No significant differences were observed for pyruvate, phosphocreatine and muscle/blood lactate ratio between the two conditions. Conversely to normoxia, levels of ATP, ADP and total NADH were maintained at their resting level under 60% FiO2. These data lead us to suppose a higher oxidation rate for pyruvate and NADH in mitochondria, thereby lowering the metabolic acidosis and allowing a better functioning of the glycolytic and contractile processes to delay the time to exhaustion.

Performance and fibre characteristics of human skeletal muscle during short sprint training and detraining on a cycle ergometer.

The ergometric effect of sprint training and detraining was studied in relation to muscle fibre changes in seven students trained during 9 weeks on a cycle ergometer. Before and after training and after 7-week detraining, they performed a force-velocity test on a friction-loaded cycle ergometer. On these three occasions, muscle samples were taken from vastus lateralis muscle at rest for histochemical analysis. The training-induced shift of the force-velocity relationship was such that the increase in maximal velocity (vmax) was greatest against high braking forces (FB) with unchanged vmax with no load. This was associated with higher maximal power output (28%) and peak force (16%). The increased maximal mean power output to reach a maximal velocity during a short sprint was obtained against a 23% higher optimal FB (FB,Wmax). At the same time, a considerable hypertrophy in fast twitch b (FTb) fibres was observed. All these changes were maintained after detraining. The training-induced changes in vmax reached against FB1Wmax(vm2Wmax) allowed us to produce evidence for two particular sub-groups in which inverse fibre conversions were observed. In subgroup A, the lowered post-training vm,Wmax was associated with a decrease in both FTa and FTb fibres. Conversely, the vm,Wmax, increase in subgroup B was associated with a higher percentage of FT fibres as the result of increased FTa fibres and decreased FTb fibres. Thus, the fibre hypertrophy associated with a unidirectional fibre translation [FTb-->FTa-->slow twitch (ST)] toward fibres with a high thermodynamic efficiency would result mainly in increased force qualities, whereas the bidirectional fibre translation (ST-->FTa<--FTb) would allow enhancement of both force and velocity properties.

Effect of sodium citrate on performance and metabolism of human skeletal muscle during supramaximal cycling exercise.

The aim of this study was to examine whether the alkalosis-induced improvement in supramaximal performance could be explained by a less-altered muscle metabolic status. Eight subjects first performed exhausting exercise at 120% peak oxygen uptake after ingesting either a placebo (PLC) or sodium citrate (CIT) at a dose of 0.5 g.kg-1 body mass to determine exhaustion time (texh). They then, performed exercise (Lim-EX) at the same relative intensity lasting PLCtexh minus 20 s in both treatments. Samples were taken from vastus lateralis muscle at rest (90-min after the ingestion) and at the end of Lim-EX. Arterial blood samples were obtained at rest (immediately prior to and 90 min after ingesting the drug) and during the 20-min post-exercise recovery. The texh was significantly increased by CIT [PLC 258 (SD 29) s, CIT 297 (SD 45) s]. The CIT raised the rest [citrate] in blood [PLC 0.11 (SD 0.01) mmol.l-1, CIT 0.34 (SD 0.07) mmol.l-1] and in muscle [PLC 0.78 (SD 0.23) mmol.kg-1 dry mass, CIT 1.00 (SD 0.21) mmol.kg-1 dry mass]. Resting muscle pH and buffering capacity were unchanged by CIT. The same fall in muscle pH was observed during Lim-EX in the two conditions. This was associated with similar variations in both the cardio-respiratory response and muscle energy and metabolism status in spite of a better blood acid-base status after CIT. Thus, CIT would not seem to allow the alkalinization of the muscle cytosolic compartment. Though sodium citrate works in a similar way to NaHCO3 on plasma alkalinization and exercise performance, the exact nature of the mechanisms involved in the delay of exhaustion could be different and remains to be elucidated.

Enzyme adaptations of human skeletal muscle during bicycle short-sprint training and detraining.

The effect of sprint training and detraining on supramaximal performances was studied in relation to muscle enzyme adaptations in eight students trained four times a week for 9 weeks on a cycle ergometer. The subjects were tested for peak oxygen uptake (VO2peak), maximal aerobic power (MAP) and maximal short-term power output (Wmax) before and after training and after 7 weeks of detraining. During these periods, biopsies were taken from vastus lateralis muscle for the determination of creatine kinase (CK), adenylate kinase (AK), glycogen phosphorylase (PHOS), hexokinase (HK), phosphofructokinase (PFK), lactate dehydrogenase (LDH) and its isozymes, 3-hydroxy-acyl-CoA dehydrogenase (HAD) and citrate synthase (CS) activities. Training induced large improvements in Wmax (28%) with slight increases (3%) in VO2peak (P < 0.10). This was associated with a greater glycolytic potential as shown by higher activities for PHOS (9%), PFK (17%) and LDH (31%) after training, without changes in CK and oxidative markers (CS and HAD). Detraining induced significant decreases in VO2peak (4%), MAP (5%) and oxidative markers (10-16%), while Wmax and the anaerobic potential were maintained at a high level. This suggests a high level in supramaximal power output as a result of a muscle glycogenolytic and glycolytic adaptation. A long interruption in training has negligible effects on short-sprint ability and muscle anaerobic potential. On the other hand, a persistent training stimulus is required to maintain high aerobic capacity and muscle oxidative potential. This may contribute to a rapid return to competitive fitness for sprinters and power athletes.

Use of the force-velocity test to determine the optimal braking force for a sprint exercise on a friction-loaded cycle ergometer.

A group of 15 untrained male subjects pedalled on a friction-loaded cycle ergometer as fast as possible for 5-7 s to reach the maximal velocity (vmax) against different braking forces (FB). Power was averaged during a complete crank rotation by adding the power dissipated against FB to the power necessary to accelerate the flywheel. For each sprint, determinations were made of peak power output (Wpeak), power output attained at vmax (Wvmax) calculated as the product of vmax and FB and the work performed to reach vmax expressed in mean power output (Wvmax). The relationships between these parameters and FB were examined. A biopsy taken from the vastus lateralis muscle and tomodensitometric radiographs of both thighs were taken at rest to identify muscle metabolic and morphometric properties. The Wpeak value was similar for all FB. Therefore, the average of values was defined as corrected maximal power (Wmax). This value was 11% higher than the maximal power output uncorrected for the acceleration. Whereas the Wmax determination did not require high loads, the highest Wvmax value (Wmax) was produced when loading was heavy, as evidenced by the Wvmax-FB parabolic relationship. For each subject, the braking force (FB,Wmax) giving Wmax was defined as optimal. The FB,Wmax, equal to 0.844 (SD 0.108) N.kg-1 bodymass, was related to thigh muscle area (r = 0.78, P < 0.05). The maximal velocity (vm,Wmax) reached against this force seemed to be related more to intrinsic fibre properties (% fast twitch b fibre area and adenylate kinase activity). Thus, from the Wmax determination, it is suggested that it should be possible to predict the conditions for optimal exercise on a cycle ergometer.

Effects of training in normoxia and normobaric hypoxia on human muscle ultrastructure.

The adaptive response of skeletal muscle to training in normoxia and in severe normobaric hypoxia was studied. The first group of five male subjects trained for 3 weeks on a bicycle (2 h/day, 6 days/week) in normoxia (Control training, Con T). A second group of five subjects trained in an ambient FIO2 decreasing progressively from 12.7% to a final level of 10.0% (hypoxic training, Hyp T). Fourteen months later, these subjects trained in normoxia at the same absolute power (normoxic training, Nor T). Peak oxygen consumption (VO2 max) was measured in normoxic and hypoxic conditions. Biopsies from the vastus lateralis muscle were analysed for fibre size, capillary and ultrastructural composition. Nor T had no effect on muscle tissue or VO2 max. Con T increased volume density of total mitochondria and lipids by 36 and 135% respectively (P < 0.05). Hyp T induced a 10% increase (P < 0.05) in peak VO2 max measured in hypoxia. Mean fibre cross-sectional area, interfibrillar mitochondrial volume density and capillary-to-fibre ratio were increased (P < 0.05) by 10, 42 and 13% respectively in the Hyp T group. These results suggest that training at the same relative workload in normoxia and hypoxia have similar, but not identical, effects on muscle tissue. If training in normoxia is carried out at the same absolute workload as in severe hypoxia, no significant effects are observed.

Ergometric and metabolic adaptation to a 5-s sprint training programme.

The effects of 7 weeks of sprint training (repeated 5-s all-out sprints) on maximal power output (Wv,max) determined during a force-velocity test and a 30-s Wingate test (Wpeak) were studied in ten students [22 (SD 2) years] exercising on a cycle ergometer. Before and after training, muscle biopsies were taken from vastus lateralis muscle at rest for the ten subjects and immediately after a training session for five of them. Sprint training induced an improvement both in peak performances by 25% (Wv,max and Wpeak) and in the 30-s total work by 16%. Before sprint training, the velocity reached with no load (v0) was related to the resting muscle phosphocreatine (PCr) stores (r = 0.87, P < 0.001). The training-induced changes in v0 were observed only when these PCr stores were lowest. This pointed to a possible limiting role of low PCr concentrations in the ability to reach a high velocity. The improvement in performances was linked to an increase in the energy production from anaerobic glycolysis. This result was suggested in muscle by the increase in lactate production measured after a training session associated with the 20% higher activity of both phosphofructokinase and lactate dehydrogenase. The sprint training also increased the proportion of slow twitch fibres closely related to the decrease in fast twitch b fibres. This result would appear to demonstrate an appropriate adaptive reaction following high-intensity intermittent training for the slow twitch fibres which exhibit a greater oxidative capacity.

Pre-acclimatization to high altitude using exercise with normobaric hypoxic gas mixtures.

Pre-acclimatization was conducted using a new method elaborated in our laboratory, combining high intensity exercise while breathing hypoxia normobaric gas mixtures. The training consisted in a daily training during three weeks, 6 days a week, two hours a day, on bicycle ergometer. Eighteen subjects aging 22.2 +/- 1.4 years (11 males, 7 females) were matched in two similar groups: one group trained in normoxic conditions (NG) while the other group (HG) trained with a progressive decrease of the fraction of inspired oxygen (from 12.2% to 10.0%). Maximal oxygen uptake (VO2max) were measured before and after the protocol period in both hypoxic (VO2max H, FIO2 = 10.4%) and normoxic (VO2max N) conditions, for the 2 groups. Training induced a similar O2max N increase in the two groups. The ratio VO2max H/VO2max N was calculated. As expected, in NG group, this ratio decreased significantly (from 63.9 +/- 4.3 to 57.5 +/- 3.1%, p < 0.01) after the training period compared to the initial value, diminution associated with an elevation of VO2max N (from 48.4 +/- 9.0 to 52.9 +/- 9.0 ml.min-1 x kg-1, p < 0.01). Conversely, in HG group, this ratio was not significantly diminished (from 61.7 +/- 3.8 to 60.5 +/- 5.2%, NS) in spite of a similar increase of VO2max N (from 47.5 +/- 5.5 to 50.7 +/- 4.9 ml.min-1 x kg-1, p < 0.01). This does not follow the diminution of the ratio usually described when VO2max N reach higher values.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of arginine aspartate on the exercise-induced hyperammoniemia in humans: a two periods cross-over trial.

To investigate the effect of the ingestion of arginine aspartate (AA) in the decrease of the exercise-induced accumulation of ammonia in plasma, 11 voluntary subjects took part in a cross-over study where AA effect was tested against placebo. Both treatments were randomly administered in a double-blind procedure. To ensure the subjects would be able to present reproducible exercise-testing results during repetitive sessions, they were involved before the experiment in a cycle ergometer training program during 8 weeks. This training determined a significant 14% increase (P less than 0.001) in maximal oxygen uptake (VO2 max). The treatments were administered during 10 days and the two treatments were separated by a 10 day-wash-out period. A 45 min-cycle ergometer test was performed at 80% VO2 max during the 10th day of each treatment to measure plasma ammonia (p[NH4+]) and total blood lactate (b[lact]) concentrations at rest and at the 15th, 30th and 45th min of exercise (determinations of changes from rest; delta p[NH4+] and delta b[lact]). Both concentrations were unchanged between AA and placebo at rest but a significant lesser delta p[NH4+] was found under AA at the 15th min of exercise only (P less than 0.05). On the other hand, an order effect was found for delta p[NH4+] between the two periods of randomized treatment that was interpreted as a remaining training effect. This effect was highly significant at the 30th and 45th min of exercise (P less than 0.001). It was concluded that AA effect was minor with regard to the training effect. As it was not located at the same time of exercise, AA effect would not consequently have the same functional origin (postulated increase in the peripheral clearance of ammonia) than those of training (decrease in muscle production of ammonia).

The energetics of middle-distance running.

In order to assess the relative contribution of aerobic processes to running velocity (v), 27 male athletes were selected on the basis of their middle-distance performances over 800, 1500, 3000 or 5000 m, during the 1987 track season. To be selected for study, the average running velocity (v) corresponding to their performances had to be superior to 90% of the best French v of the season. Maximum O2 consumption (VO2max) and energy cost of running (C) had been measured within the 2 months preceding the track season, which, together with oxygen consumption at rest (VO2rest) allowed us to calculate the maximal v that could be sustained under aerobic conditions: vamax = (VO2max - VO2rest) x C-1. The treadmill running v corresponding to a blood lactate of 4 mmol.l-1 (vla4), was also calculated. In the whole group, C was significantly related to height (r = -0.43; P less than 0.03). Neither C nor VO2max (with, in this case, the exception of the 3000 m athletes) were correlated to v. On the other hand, vamax was significantly correlated to v over distances longer than 800 m. These v were also correlated to vla4. However vla4 occurred at 87.5% SD 3.3% of vamax, this relationship was interpreted as being an expression of the correlation between vamax and v. Calculation of vamax provided a useful means of analysing the performances. At the level of achievement studied, v sustained over 3000 m corresponded to vamax.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of endurance training on hyperammonaemia during a 45-min constant exercise intensity.

Eleven laboratory-pretrained subjects (initial VO2max = 54 ml.kg-1.min-1) took part in a study to evaluate the effect of a short endurance training programme [8-12 sessions, 1 h per session, with an intensity varying from 60% to 90% maximal oxygen consumption (VO2max)] on the responses of blood ammonia (b[NH+4]) and lactate (b[la]) concentrations during progressive and constant exercise intensities. After training, during which VO2max did not increase, significant decreases in b[NH+4], b[la] and muscle proton concentration were observed at the end of the 80% VO2max constant exercise intensity, although b[NH+4] and b[la] during progressive exercise were unchanged. On the other hand, no correlations were found between muscle fibre composition and b[NH+4] in any of the exercise procedures. This study demonstrated that a constant exercise intensity was necessary to reveal the effect of training on muscle metabolic changes inducing the decrease in b[NH+4] and b[la]. At a relative power of exercise of 80% VO2max, there was no effect of muscle fibre composition on b[NH+4] accumulation.

Comparison of incremental and steady state tests of endurance training.

To compare the results obtained by incremental or constant work load exercises in the evaluation of endurance conditioning, a 20-week training programme was performed by 9 healthy human subjects on the bicycle ergometer for 1 h a day, 4 days a week, at 70-80% VO2max. Before and at the end of the training programme, (1) the blood lactate response to a progressive incremental exercise (18 W increments every 2nd min until exhaustion) was used to determine the aerobic and anaerobic thresholds (AeT and AnT respectively). On a different day, (2) blood lactate concentrations were measured during two sessions of constant work load exercises of 20 min duration corresponding to the relative intensities of AeT (1st session) and AnT (2nd session) levels obtained before training. A muscle biopsy was obtained from vastus lateralis at the end of these sessions to determine muscle lactate. AeT and AnT, when expressed as % VO2max, increased with training by 17% (p less than 0.01) and 9% (p less than 0.05) respectively. Constant workload exercise performed at AeT intensity was linked before training (60% VO2max) to a blood lactate steady state (4.8 +/- 1.4 mmol.l-1) whereas, after training, AeT intensity (73% VO2max) led to a blood lactate accumulation of up to 6.6 +/- 1.7 mmol.l-1 without significant modification of muscle lactate (7.6 +/- 3.1 and 8.2 +/- 2.8 mmol.kg-1 wet weight respectively). It is concluded that increase in AeT with training may reflect transient changes linked to lower early blood lactate accumulation during incremental exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of endurance training on capillary supply of human skeletal muscle on two age groups (20 and 60 years).

Two groups of human subjects were submitted to a 20-week endurance training program (1 h a day, 4 days a week, 70-80% max VO2). The first group (G20) consisted of eight 22 +/- 3 years male students, the second group (G60) was composed of seven still very physically active elderly male subjects (62 +/- 4 years). Training significantly increased max VO2 by 15% in G20 and 7% in G60. Muscle samples taken from the vastus lateralis muscle before and after training were histochemically stained for fibre-typing (myofibrillar ATPase), capillary supply and fibre area measurements (amylase PAS and NADH-TR). Fibre-type distribution was unchanged with training. Capillary density (cap X mm-2) increased significantly in both groups from 316 +/- 42 to 396 +/- 73 in G20 and from 308 +/- 48 to 409 +/- 55 in G60. This enhancement of capillary supply was linked to the proliferation of capillaries in G20 where the number of capillaries in contact with ST and FTa fibres (CC) significantly increased from 4.6 to 5.9 and from 4.8 to 6.1 respectively. No significant changes in fibre areas were found in G20. On the contrary, G60 did not show any significant sign of capillary growth (CC unchanged) whereas fibre areas significantly decreased in ST (6,410 to 5,520 micron 2) and FTa fibres (5,830 to 5,090 micron 2). A methodological evaluation of fibre-area measurement was described, with confirmation of the data. It was concluded that this study may illustrate the trainability of skeletal muscle of elderly men in a possibly different way to that seen in a younger age group.

Lactate determination with the lactate analyser LA 640: a critical study.

Using the new method of sample preparation developed by the manufacturer in 1979, the lactate analyser LA 640 now provides reliable measurements of blood lactic acid from blood micro-samples of 20 microliters within 2 min. Reproducibility is comparable to that obtained by spectrophotometric assay with +/- 0.2 mmol . l-1 for 95% confidence limits. High accuracy was also obtained with 95% linked confidence limits within +/- 0.19 mmol . l-1 and +/- 0.46 mmol . l-1 for blood lactate concentrations of from 2-4 and 7-9 mmol . l-1 respectively. Due to a lactate concentration increase of 0.5 mmol . l-1 . h-1 in whole blood kept at 20 degrees C, the blood must be immediately diluted in the buffer haemolysing solution after withdrawal. This diluted sample can then be stored at room temperature without alteration, provided the concentration in the dilution is lower than 0.8 mmol . l-1. For serial successive measurements, a new sample can be tested before the electrode current reaches its background value.

[Use of the LA 640 for a simple method of measuring the concentration of muscle lactate]. / Utilisation du LA 640 pour une méthode simple de mesure de la concentration du lactate musculaire.

A simple technique was elaborated for the measurement of muscle lactate concentration. It was tested on samples of muscle vastus lateralis taken by the Bergström (1962) needle biopsy technique at the end of 20 min exercise bouts corresponding to 60-70% of Vo2 max. The biopsies were freshly frozen in liquid nitrogen, powdered and weighed in a cryostat at -20 degrees C. The extraction were made by saponine and the lactate measured in the saponine solution by an electrochemical-enzymatic method (LA 640). The results concern: the time of taking the biopsies and the freezing time (27 +/- 11 s and 34 +/- 9 s respectively); the accuracy of weighing (inducing a 1% uncertainty in the final result); a comparison of the saponine extraction with the perchloric acid extraction and a checking of the extraction capacity of the former; the accuracy of the whole measurement (the mean relative confidence limits are +/- 8-10%; the reproducibility of the technique through measurement of the variation coefficient (18%) calculated on measurements performed at a 15 days interval in 6 trained subjects. The discussion of the results and their comparison with those of the literature lead to the conclusion that the described method is suitable for muscle lactate measurements.

Endurance training, VO2 max, and OBLA: a longitudinal study of two different age groups.

This study examined the effect of a 20-week training program of two groups: six middle-aged men (37 +/- 4 yrs) (GIT) and six young male subjects (20 +/- 1 yrs) (GIIT). The training program consisted of bicycle ergometer exercise, 1 h/day, 3.5 days/week at a work load corresponding to 80%-85% of HR max. Before (S0) and at the end of the training program (S20), measurements of VO2 max, maximal work load (MWL), net efficiency, onset of blood lactate accumulation, absolute (OBLAW), and relative to MWL (OBLA %) were made on GIT and GIIT groups and on a third group (21 +/- 2 yrs) (GIIC), used as a control. Muscle fiber composition of m. vastus lateralis was studied after training for GIT and before and after the training period for GIIT and GIIC. VO2 max (ml X kg-1 X min-1), which was initially similar in GIT and GIIT (49 ml X kg-1 X min-1), increased significantly by 8% in GIT and by 19% in GIIT. OBLAW increased significantly to the same level in the two groups (38% and 42%, respectively). OBLA % increased significantly (20%) in GIT only. In the groups studied (GIIT), no change was observed for muscle fiber composition. % ST fiber type did not correlate to OBLAW or OBLA % S0 values nor to OBLAW and OBLA % changes during training. This leads to the conclusion that age and the initial physical fitness were the two major factors affecting the outcome of this endurance training program upon the two groups. Further research is needed to establish which of these two factors is the most influential.

[Changes in the affinity of oxygen for hemoglobin during general anesthesia]. / Variations de l'affinité de l'oxygène pour l'hémoglobine au cours de l'anesthésie générale.

The well known effects of the lowering of the intraerythrocyte 2, 3, diphosphoglycerate (2, 3, DPG) level and hypothermia, on the affinity of oxygen for hemoglobin, lead the authors to study the influence of these parameters on this affinity during general anesthesia. The following observations were made in 15 adult subjects, undergoing prolonged general anaesthesia (average time: 3 hrs. 10 minutes): the dissociation curve of oxyhemoglobin (DCO) by the method of mixing, the intraerythrocyte 2,3, DPG level, the hemoglobin concentration and arterial blood parameters (PO2, PCO2, pH). These measurements were recorded before and after the general anaesthesia. The results were the following: a significant reduction of P50, measured under standard conditions (from 27.64 +/- 1.74 torr to 25.57 +/- 2.28, p less than or equal to 0.01) associated with a decrease in 2,3, DPG (from 0.94 +/- 0.31 mol/mol Hb at 0.64 +/- 0.24 p less than 0.01). Among the factors responsible for this variation in the affinity, it was proved that the volume of blood transfused was of importance as well as a decrease in body temperature during the operation. When the temperature is made to vary from 37 degrees C to 35 degrees C. the P50 ranges from 25.57 +/- 2.28 to 22.86 +/- 0.97 (p less than 0.01). To conclude the authors underline the importance of hypothermia and the volume of blood transfused (average time of preservation = 15 days) on the effects of the affinity of oxygen for hemoglobin.