Frédéric Lemaître

Effect of cold or thermoneutral water immersion on post-exercise heart rate recovery and heart rate variability indices

This study aimed to investigate the effect of cold and thermoneutral water immersion on post-exercise parasympathetic reactivation, inferred from heart rate (HR) recovery (HRR) and HR variability (HRV) indices. Twelve men performed, on three separate occasions, an intermittent exercise bout (all-out 30-s Wingate test, 5 min seated recovery, followed by 5 min of submaximal running exercise), randomly followed by 5 min of passive (seated) recovery under either cold (CWI), thermoneutral water immersion (TWI) or control (CON) conditions. HRR indices (e.g., heart beats recovered in the first minute after exercise cessation, HRR(60)(s)) and vagal-related HRV indices (i.e., natural logarithm of the square root of the mean of the sum of the squares of differences between adjacent normal R-R intervals (Ln rMSSD)) were calculated for the three recovery conditions. HRR(60)(s) was faster in water immersion compared with CON conditions [30+/-9 beats min(-)(1) for CON vs. 43+/- 10 beats min(-)(1) for TWI (P=0.003) and 40+/-13 beats min(-)(1) for CWI (P=0.017)], while no difference was found between CWI and TWI (P=0.763). Ln rMSSD was higher in CWI (2.32+/-0.67 ms) compared with CON (1.98+/-0.74 ms, P=0.05) and TWI (2.01+/-0.61 ms, P=0.08; aES=1.07) conditions, with no difference between CON and TWI (P=0.964). Water immersion is a simple and efficient means of immediately triggering post-exercise parasympathetic activity, with colder immersion temperatures likely to be more effective at increasing parasympathetic activity.

Quality of life and obesity class relationships.

The aim of this study was to quantify the impact of obesity class on Health-Related Quality Of Life (HRQOL) and Total daily Energy Expenditure (TEE). 69 obese individuals were self-selected to 1 of 3 groups based upon Body Mass Index (BMI). Anthropometric parameters (height, weight, waist and hip circumference, fat mass, lean body mass), biological parameters (high density lipoprotein, low density lipoprotein, triglycerides, glycaemia, total cholesterol), and resting energy expenditure were assessed for each group. The Short Form Health Survey (SF-36) questionnaire and Hospital Anxiety Depression (HAD) scale were used to measure HRQOL, and TEE was estimated by Kurpads method. Class 3 obesity was associated with greater impairment of the physical aspects of the SF-36 (37.2±11.3), greater depression risk (8.2±4.1), and higher TEE (30.0±7.9 Kcal·day (-1)·kg (-1)) than the lower obesity classes. No difference was observed among the 3 groups in the mental and psychosocial aspects of HRQOL. Impaired physical functioning was correlated with fat mass, age, waist circumference, glycaemia control and bodily pain. TEE was positively correlated with BMI, weight, fat mass and lean body mass. The obesity class had a negative impact on the physical health aspect of HRQOL, depression risk and energy expenditure. These impairments were associated with excess fat mass, waist circumference and glycaemia parameters.

Effect of breathing pattern on arm coordination symmetry in front crawl.

Seifert, L, Chehensse, A, Tourny-Chollet, C, Lemaitre, F, Chollet, D. Effect of breathing pattern on arm coordination symmetry in front crawl. J Strength Cond Res 22(5): 1670-1676, 2008-This study analyzed the relationship between breathing pattern and arm coordination symmetry in 11 expert male swimmers who performed the front crawl at their 100-m race pace using seven randomized breathing patterns. Two indexes of coordination (IdCP and IdCNP) and a symmetry index (SI) based on the difference of IdCP − IdCNP were calculated. IdCP calculated the lag time between the beginning of arm propulsion on the nonpreferential breathing side and the end of arm propulsion on the preferential breathing side; IdCNP did the converse. The IdCP and IdCNP comparisons and the SI showed coordination asymmetries among the seven breathing patterns. Specifically, breathing to the preferential side led to an asymmetry, in contrast to the other breathing patterns, and the asymmetry was even greater when the swimmer breathed to his nonpreferential side. These findings highlight the effect of breathing laterality in that coordination was symmetric in patterns with breathing that was bilateral, axed (as in breathing with a frontal snorkel), or removed (as in apnea). One practical application is that arm coordination asymmetry can be prevented or reduced by using breathing patterns that balance the coordination.

New Molecular Knowledge Towards the Trigemino-Cardiac Reflex as a Cerebral Oxygen-Conserving Reflex

The trigemino-cardiac reflex (TCR) represents the most powerful of the autonomous reflexes and is a subphenomenon in the group of the so-called “oxygen-conserving reflexes”. Within seconds after the initiation of such a reflex, there is a powerful and differentiated activation of the sympathetic system with subsequent elevation in regional cerebral blood flow (CBF), with no changes in the cerebral metabolic rate of oxygen (CMRO2) or in the cerebral metabolic rate of glucose (CMRglc). Such an increase in regional CBF without a change of CMRO2 or CMRglc provides the brain with oxygen rapidly and efficiently. Features of the reflex have been discovered during skull base surgery, mediating reflex protection projects via currently undefined pathways from the rostral ventrolateral medulla oblongata to the upper brainstem and/or thalamus, which finally engage a small population of neurons in the cortex. This cortical center appears to be dedicated to transduce a neuronal signal reflexively into cerebral vasodilatation and synchronization of electrocortical activity; a fact that seems to be unique among autonomous reflexes. Sympathetic excitation is mediated by cortical-spinal projection to spinal preganglionic sympathetic neurons, whereas bradycardia is mediated via projections to cardiovagal motor medullary neurons. The integrated reflex response serves to redistribute blood from viscera to the brain in response to a challenge to cerebral metabolism, but seems also to initiate a preconditioning mechanism. Previous studies showed a great variability in the human TCR response, in special to external stimuli and individual factors. The TCR gives, therefore, not only new insights into novel therapeutic options for a range of disorders characterized by neuronal death, but also into the cortical and molecular organization of the brain.

The trigemino-cardiac reflex in adults: own experience

The trigemino-cardiac reflex The trigemino-cardiac reflex (TCR) has previously been described in the literature as a reflexive response composed of bradycardia, hypotension and gastric hypermotility seen upon mechanical stimulation anywhere in the distribution of the trigeminal nerve [1–5]. Based on the initial rabbit neurostimulation experiments of Kumada et al. in 1977 [6], TCR was first observed by Schaller et al. in 1999 during neurosurgical operations [5]. By systematic observation, the incidence of the TCR during neurosurgical procedures around the trigeminal nerve was shown to be approximately 10–18%, independently of the surgeon who operated or the approach that was used [3,7–12]. In their key works, Schaller et al. first defined TCR in detail, and their observations are at present generally accepted [3,5,13–15].

Swim Specialty Affects Energy Cost and Motor Organization

The purpose of this study was to analyse the effect of swimmer specialty on energy cost and motor organization. The stroking parameters (velocity, stroke rate, stroke length, stroke index) and the index of coordination (IdC) of 6 elite sprinters were compared with those of 6 elite long-distance swimmers during an incremental swimming exercise test (6x300 m separated by 30 s of passive recovery) that progressively increased the energy cost. Energy cost ( C), with its aerobic ( Caero) and anaerobic ( Canaero) components, was determined by measuring oxygen uptake (VO2) and blood lactate ([La]). Motor organization was assessed by analysis of video recordings from aerial and underwater side-view cameras. The results showed that throughout the test, both groups increased C, Canaero, stroke rate and IdC and decreased Caero and stroke length (all P<0.05). On the mean of the 300-m sets, sprinters had higher values for C (14.8 VS. 12.9 J x kg (-1).m (-1)), Canaero (33.8 VS. 23.4%), [La] (5.9 VS. 3.1 mmol x L (-1)), stroke length (2.31 VS. 2.28 m) and IdC (-11.2 VS. -21.7%) and lower values for Caero (66.2 VS. 79.6%), VO2 net (2 825 VS. 2 903 mL x min (-1)), stroke rate (0.55 VS. 0.62 Hz) and stroke index (2.96 VS. 3.19 m (2) x s (-1)) than long-distance swimmers (all P<0.05). For the same relative intensity, sprinters accumulated more lactate and swam more slowly than long-distance swimmers; they showed greater change in their arm coordination but their swimming economy was lower.

The trigeminocardiac reflex – a comparison with the diving reflex in humans

The trigeminocardiac reflex (TCR) has previously been described in the literature as a reflexive response of bradycardia, hypotension, and gastric hypermotility seen upon mechanical stimulation in the distribution of the trigeminal nerve. The diving reflex (DR) in humans is characterized by breath-holding, slowing of the heart rate, reduction of limb blood flow and a gradual rise in the mean arterial blood pressure. Although the two reflexes share many similarities, their relationship and especially their functional purpose in humans have yet to be fully elucidated. In the present review, we have tried to integrate and elaborate these two phenomena into a unified physiological concept. Assuming that the TCR and the DR are closely linked functionally and phylogenetically, we have also highlighted the significance of these reflexes in humans.

Circulatory effects of apnoea in elite breath-hold divers

Aim:  Voluntary apnoea induces several physiological adaptations, including bradycardia, arterial hypertension and redistribution of regional blood flows. Elite breath‐hold divers (BHDs) are able to maintain very long apnoea, inducing severe hypoxaemia without brain injury or black‐out. It has thus been hypothesized that they develop protection mechanisms against hypoxia, as well as a decrease in overall oxygen uptake.

Static apnea effect on heart rate and its variability in elite breath-hold divers

BACKGROUND The diving response includes cardiovascular adjustments known to decrease oxygen uptake and thus prolong apnea duration. As this diving response is in part characterized by a pronounced decrease in heart rate (HR), it is thought to be vagally mediated. METHODS In five professional breath-hold divers (BHDs) and five less-trained controls (CTL), we investigated whether the diving response is in fact associated with an increase in the root mean square successive difference of the R-R intervals (RMSSD), a time-domain heart rate variability (HRV) index. HR behavior and arterial oxygen saturation (SaO2) were continuously recorded during one maximal apnea. Short-term changes in SaO2, HR, and RMSSD were calculated over the complete apnea duration. RESULTS BHDs presented bi-phasic HR kinetics, with two HR decreases (32 +/- 17% and 20 +/- 10% of initial HR). The second HR decrease, which was concomitant to the pronounced SaO2 decrease, was also simultaneous to a marked increase in RMSSD. CTL showed only one HR decrease (50 +/- 10% of initial HR), which appeared before the concomitant SaO2 and RMSSD changes. When all subject data were combined, arterial desaturation was positively correlated with total apnea time (r = 0.87, P < 0.01). CONCLUSION This study indicates that baroreflex stimulation and hypoxia may be involved in the bi-phasic HR response of BHDs and thus in their longer apnea duration.

Apnea: A new training method in sport?

The physiological responses to apnea training exhibited by elite breath-hold divers may contribute to improving sports performance. Breath-hold divers have shown reduced blood acidosis, oxidative stress and basal metabolic rate, and increased hematocrit, erythropoietin concentration, hemoglobin mass and lung volumes. We hypothesise that these adaptations contributed to long apnea durations and improve performance. These results suggest that apnea training may be an effective alternative to hypobaric or normobaric hypoxia to increase aerobic and/or anaerobic performance.