Patrick Mucci

Exercise-Induced Arterial Hypoxaemia in Athletes

AbstractDuring exercise, healthy individuals are able to maintain arterial oxygenation, whereas highly-trained endurance athletes may exhibit an exercise-induced arterial hypoxaemia (EIAH) that seems to reflect a gas exchange abnormality. The effects of EIAH are currently debated, and different hypotheses have been proposed to explain its pathophysiology. For moderate exercise, it appears that a relative hypoventilation induced by endurance training is involved. For high-intensity exercise, ventilation/perfusion (V̇A/Q̇) mismatching and/or diffusion limitation are thought to occur. The causes of this diffusion limitation are still under debate, with hypotheses being capillary blood volume changes and interstitial pulmonary oedema. Moreover, histamine is released during exercise in individuals exhibiting EIAH, and questions persist as to its relationship with EIAH and its contribution to interstitial pulmonary oedema. Further investigations are needed to better understand the mechanisms involved and to determine the long term consequences of repetitive hypoxaemia in highly trained endurance athletes.

Evaluation of quality of life in elderly healthy subjects after aerobic and/or mental training.

This study proposed different techniques of mental rehabilitation to healthy elderly subjects in order to assess the results in terms of subjectively perceived changes in quality of life. Thirty-two elderly subjects (60-76 years) were assigned to one of the four groups: aerobic training, mental training, combined aerobic and mental training and a control group. Before and after 2 months of training, all subjects took two memory tests. After training, a French validated questionnaire of quality of life was administered individually. Memory parameters such as logical memory (P<0.05), paired associated learning (P=0.05) and memory quotient (P=0.01) were enhanced in all groups except the control group, but in terms of quality of life all the elderly subjects were dissatisfied. VO(2max) and ventilatory threshold were significantly improved in the two groups who were engaged in a physical training program (AT and AMT) and these improvements were associated with a better quality of life in the domain of functional life. Association of the two techniques did not enhance the results for cognitive function. In conclusion, despite objective improvement in cognitive function, all subjects reported dissatisfaction in terms of improvement in quality of life, whatever their assigned group. Nevertheless, an improvement in quality of life was acknowledged after aerobic training for the physical component of functional life.

Continuous vs. Interval Aerobic Training in 8- to 11-Year-Old Children

Baquet, G, Gamelin, F-X, Mucci, P, Thévenet, D, Van Praagh, E, and Berthoin, S. Continuous vs. interval aerobic training in 8- to 11-year-old children. J Strength Cond Res 24(5): 1381-1388, 2010-The aim of the present study was to show if the use of continuous-running training vs. intermittent-running training has comparable or distinct impact on aerobic fitness in children. At first, children were matched according to their chronological age, their biological age (secondary sexual stages), and their physical activity or training status. Then, after randomization 3 groups were composed. Sixty-three children (X 9.6 ± 1.0 years) were divided into an intermittent-running training group (ITG, 11 girls and 11 boys), a continuous-running training group (CTG, 10 girls and 12 boys), and a control group (CG, 10 girls and 9 boys). Over 7 weeks, ITG and CTG participated in 3 running sessions per week. Before and after the training period, they underwent a maximal graded test to determine peak oxygen uptake (peak &OV0312;o2) and maximal aerobic velocity (MAV). Intermittent training consisted of short intermittent runs with repeated exercise and recovery sequences lasting from 5/15 to 30/30 seconds. With respect to continuous training sessions, repeated exercise sequences lasted from 6′ to 20′. Training-effect threshold for statistical significance was set at p < 0.05. After training, peak &OV0312;o2 was significantly improved in CTG (+7%, p < 0.001) and ITG (+4.8%, p < 0.001), whereas no difference occurred for the CG (−1.5%). Similarly, MAV increased significantly (p < 0.001) in both CTG (+8.7%) and ITG (+6.4%) with no significant change for CG. Our results demonstrated that both continuous and intermittent-running sessions induced significant increase in peak &OV0312;o2 and MAV. Therefore, when adequate combinations of intensity/duration exercises are offered to prepubertal children, many modalities of exercises can successfully be used to increase their aerobic fitness. Aerobic running training is often made up of regular and long-distance running exercises at moderate velocity, which causes sometimes boredom in young children. During the developmental years, it seems therefore worthwhile to use various training modalities, to make this activity more attractive and thus create conditions for progress and enhanced motivation.

Evidence for an inadequate hyperventilation inducing arterial hypoxemia at submaximal exercise in all highly trained endurance athletes.

PURPOSE The majority of highly trained endurance athletes with a maximal oxygen uptake greater than 60 mL x min(-1) x kg(-1) develop exercise-induced hypoxemia (EIH). Yet some of them apparently do not. The pathophysiology of EIH seems to be multifactorial, and one explanatory hypothesis is a relative hypoventilation. Nevertheless, conflicting results have been reported concerning its contribution to EIH. The aim of this study was to compare the cardiorespiratory responses to maximal exercise of highly trained endurance athletes demonstrating the same aerobic capacity without EIH (N athletes) and with EIH (H athletes). METHODS Ten N athletes and twelve H athletes performed an incremental exercise test. Measurements of arterial blood gases and cardiorespiratory parameters were performed at rest and during exercise. RESULTS All athletes presented a significant decrease in PaO2 (P < 0.05) from rest up to 80% VO2max associated with an increase in PaCO2, both findings consistent with a relative hypoventilation. Then the H athletes, who had a greater training volume per week and a higher second ventilatory threshold than the N athletes (respectively, 17 +/- 1.1 vs 13.1 +/- 0.7 h x wk(-1); 91.8 +/- 1.7 vs 86.1 +/- 1.8% VO2max), presented a continuous PaO2 decrease up to VO2max. This was associated with a widening (Ai-a)DO2. CONCLUSION This study showed that a relative hypoventilation, probably induced by a high level of endurance training, induced hypoxemia in all athletes. However, a nonventilatory mechanism, perhaps related to the volume of training, seemed to affect gas exchanges beyond the second ventilatory threshold in the H athletes, thereby enhancing EIH.

Interleukins 1-beta, -8, and histamine increases in highly trained, exercising athletes.

PURPOSE Exercise-induced hypoxemia (EIH) in highly trained athletes is associated with an increase in histamine release (%H) during exercise. Certain cytokines, known as histamine-releasing factors, are capable of interacting with basophils and/or mast cells to cause the release of histamine. The aim of this study was to determine whether the increased histamine release in highly trained athletes is related to a high plasma level in interleukin-1 beta (IL-1beta), IL-3, or IL-8 in arterial blood. METHODS These parameters were measured in 11 endurance athletes (23.2 +/- 1.2 yr (mean +/- SEM)) known to develop exercise-induced hypoxemia and 11 control subjects (25.0 +/- 1.1 yr) at rest, during an incremental exhaustive exercise test, and at the fifth minute of recovery. RESULTS Histamine release increased between rest and maximal exercise in the athletes (P < 0.01), showing a strong correlation with EIH (r = 0.76, P < 0.01) and was unchanged in the controls. IL-3 plasma concentration was not altered with training and/or with exercise. Circulating IL-8 levels were not different between trained and untrained subjects at any testing level and increased at maximal exercise in both groups (P < 0.01). IL-1beta plasma levels were higher in athletes than in controls (P < 0.05) at each testing level and increased during exercise only in the athletes (P < 0.05). CONCLUSION An elevated concentration of IL-1beta in plasma and its association with increased IL-8 levels during exercise may partly explain the increase in %H associated with EIH in highly trained athletes. Histamine, IL-8, and IL-1beta releases during exercise reflect an inflammatory reaction, which is probably involved in EIH.

Effect of ageing on the ventilatory response and lactate kinetics during incremental exercise in man

Abstract We investigated the effects of age on breathing pattern, mouth occlusion pressure, the ratio of mouth occlusion pressure to mean inspiratory flow, and venous blood lactate kinetics during incremental exercise. Mouth occlusion pressure was used as an index of inspiratory neuromuscular activity, and its ratio to mean inspiratory flow was used as an index of the “effective impedance” of the respiratory system. Nine elderly male subjects [mean (SD) age: 68.1 (4.8) years] and nine young male subjects [mean (SD) age: 23.4 (1.3) years] performed an incremental exercise test on a bicycle ergometer. After a warm-up at 30 W, the power was increased by 30 W every 1.5 min until exhaustion. Our results showed that at maximal exercise, power output, breathing pattern, and respiratory exchange values, with the exception of tidal volume and the “effective impedance” of the respiratory system, were significantly higher in the young subjects. The power output and oxygen consumption values at the anaerobic threshold were also significantly higher in the young men. At the same power output, the elderly subjects showed significantly higher values for minute ventilation, respiratory equivalents for oxygen uptake and carbon dioxide output (CO2), mean inspiratory flow, occlusion pressure and lactate concentration than the young subjects. At the same CO2 below the anaerobic threshold (0.5, 0.75, 1.00 and 1.25 l · min−1), minute ventilation and lactate concentration were also significantly higher in the elderly subjects. We observed a significantly higher minute ventilation at CO2 values of 0.5, 0.75, 1.00 (P < 0.001) and 1.25 l · min−1 (P < 0.05) in the elderly men, and a significantly higher lactate concentration at CO2 values of 1.00 (P < 0.05) and 1.25 l · min−1 (P < 0.01). In conclusion, the ventilatory response in elderly subjects is elevated in comparison with that in young subjects, both below and above the anaerobic threshold. This study demonstrates for the first time that this ventilatory increase, both below and above the threshold, is partly due to an increased lactate concentration.

Ventilation response to CO2 and exercise-induced hypoxaemia in master athletes

Abstract Exercise-induced hypoxaemia (EIH) in master athletes may be related to a diminished exercise hyper- pnoea. The aim of this study was to determine whether EIH is associated with a change in the sensitivity of the ventilation response to activation of the central chemoreceptors. The ventilation response to CO2 was measured in nine elderly untrained men (UT) [mean age 66.3 (SEM 3.1) years] and nine master athletes (MA) [mean age 62.7 (SEM 0.8) years] at rest, during moderate exercise (40% maximal oxygen uptake, V˙O2max), and during strenuous exercise (70% V˙O2max) using the rebreathing method. Our results showed that the ventilation response to CO2 did not differ with endurance training and/or exercise, that the threshold of the CO2 response (Th) increased with exercise (P < 0.001), that the increase in Th in MA was higher than in UT between rest and moderate exercise [ΔTh0–40: 8.55 (SEM 1.8) vs 3.06 (SEM 1.72) mmHg, P < 0.05], and that ΔTh0–40 and Th during moderate exercise were negatively correlated with arterial O2 saturation during maximal exercise (r = 0.50, P<0.05). We concluded therefore that exercise-induced hypoxaemia in master athletes may not be due to a lower ventilation response to CO2, but may be partly related to a greater increase in Th during moderate exercise.

Evidence of Exercise-Induced Arterial Hypoxemia in Prepubescent Trained Children

Exercise-induced arterial hypoxemia (EIAH) is a recognized phenomenon in highly trained adults. Like adult athletes, prepubescent trained children may develop high-level metabolic demand but with a limited lung capacity in comparison with adults. The purpose of this investigation was to search for evidence of EIAH in prepubescent trained children. Twenty-four prepubescent (age: 10.3 ± 0.2 y) trained children (10.0 ± 0.7 h of weekly physical activity) performed pulmonary function tests and a graded maximal exercise test on a cycle ergometer. EIAH was defined as a drop of at least 4% from resting level arterial oxygen saturation (Sao2) measured by pulse oximetry. EIAH was observed in seven children. Forced vital capacity (FVC), ventilatory response to exercise (ΔV˙E/ΔV˙co2), and breathing reserve at maximal exercise were significantly lower, whereas tidal volume relative to FVC was higher in hypoxemic children than in nonhypoxemic children; weekly physical activity and maximal oxygen uptake were similar. Moreover, positive relationships were found between Sao2 at maximal exercise and breathing reserve (r = 0.56; p < 0.05) or volume relative to FVC (r = 0.70; p < 0.01). EIAH may occur in prepubescent trained children with a relatively low maximal oxygen uptake (42 mL · min−1 · kg−1); however, the mechanisms remain unclear and need to be investigated more accurately.

Aerobic fitness influences cerebral oxygenation response to maximal exercise in healthy subjects.

The study examined whether the aerobic fitness level modifies the cerebral oxygenation response to incremental ramp exercise, and more specifically the decline in cerebral oxygenation from heavy exercise up to maximal intensities. 11 untrained (VO2max 47.3±4.0 mL min(-1) kg(-1)) and 13 endurance-trained (VO2max 61.2±8.0 mL min(-1) kg(-1)) healthy men performed a maximal ramp cycle exercise. Left prefrontal cortex oxygenation (ΔHbO2) was monitored by near-infrared spectroscopy. A cerebral oxygenation threshold decline (ThCOx) during exercise was determined. ThCox occurred in all subjects but for higher VO2 (mL min(-1) kg(-1)) in endurance-trained than in untrained subjects (P<0.01). At submaximal exercise intensity corresponding to ThCOx, ΔHbO2 was higher in endurance-trained than in untrained subjects (P<0.05). VO2 at ThCox was related to VO2 at respiratory compensation point (n=24, r=0.93, P<0.001) and to VO2max (n=24, r=0.92, P<0.001). These findings indicate that above the respiratory compensation point the prefrontal O2 demand exceeds the supply in untrained and in endurance-trained subjects. In addition, the occurrence of ThCOx was delayed to higher absolute exercise intensities in endurance-trained in relation with their higher VO2max than untrained men. These results demonstrated that aerobic fitness influences cerebral oxygenation during exercise.

Faster pulmonary oxygen uptake kinetics in children vs adults due to enhancements in oxygen delivery and extraction.

This study aimed to examine if the faster pulmonary oxygen uptake (VO2p) phase 2 in children could be explained by increased O 2 availability or extraction at the muscle level. For that purpose, O 2 availability and extraction were assessed using deoxyhemoglobin (HHb) estimated by near‐infrared spectroscopy during moderate‐intensity constant load cycling exercise in children and young adults. Eleven prepubertal boys and 12 men volunteered to participate in the study. They performed one maximal graded exercise to determine the power associated with the gas exchange threshold (GET) and four constant load exercises at 90% of GET. VO2p and HHb were continuously monitored. VO2p, HHb, and estimated capillary blood flow ( Q ˙ cap ) kinetics were modelled after a time delay and characterized by the time to achieve 63% of the amplitude (τ) and by mean response time (MRT: time delay + τ), respectively. Mean values of τ for VO2p (P < 0.001), of MRT for HHb (P < 0.01) and of MRT for Q ˙ cap (P < 0.001) were significantly shorter in children. Faster VO2p kinetics have been shown in children; these appear due to both faster O 2 extraction and delivery kinetics as indicated by faster HHb and Q ˙ cap kinetics, respectively.