Position de consensus de la Société Française de Médecine du Sport concernant la directive n° 000149 du 3 avril 2001 sur les épreuves d'effort des sportifs de haut niveau

Réflexions et prise de position de la S.F.M.S. à partir des données épidémiologiques concernant l'incidence de la mort subite sur les terrains de sport, les données épidémiologiques concernant la morbidité lors des tests d'effort, sur la pertinence de l'épreuve cardiologique chez le jeune sportif, sur la limite du dépistage dans l'ensemble de la population

Effects of intermittent hypoxia on heart rate variability during rest and exercise

Changes in heart rate variability induced by an intermittent exposure to hypoxia were evaluated in athletes unacclimatized to altitude. Twenty national elite athletes trained for 13 days at 1200 m and either lived and slept at 1200 m (live low, train low, LLTL) or between 2500 and 3000 m (live high, train low, LHTL). Subjects were investigated at 1200 m prior to and at the end of the 13-day training camp. Exposure to acute hypoxia (11.5% O2) during exercise resulted in a significant decrease in spectral components of heart rate variability in comparison with exercise in normoxia: total power (p < 0.001), low-frequency component. LF (p < 0.001), high-frequency component, HF (p < 0.05). Following acclimatization, the LHTL group increased its LF component (p < 0.01) and LF/HF ratio during exercise in hypoxia after the training period. In parallel, exposure to intermittent hypoxia caused an increased ventilatory response to hypoxia. Acclimatization modified the correlation between the ventilatory response to hypoxia at rest and the difference in total power between normoxia and hypoxia (r2 = 0.65, p < 0.001). The increase in total power, LF component, and LF/HF ratio suggests that intermittent hypoxic training increased the response of the autonomic nervous system mainly through increased sympathetic activity

Altitude, heart rate variability and aerobic capacities

We analyzed the relationship between aerobic capacities and changes in heart rate variability (HRV) in Nordic-skiers during living high-training low (Hi-Lo). Eleven skiers trained for 18 days at 1200 m, sleeping at 1200 m (LL, n = 5) or in hypoxic rooms (HL, n = 6, 3 x 6 days at altitudes of 2500 - 3000 - 3500 m, 11 h·day-1). Measurements were performed before, during and two weeks after Hi-Lo. V̇O2max, peak power output were not improved in HL nor in LL, whereas V̇O2 and power at the respiratory compensation point (V̇O2RCP and PRCP) increased by 7.5% and 5.0% only in HL. Significant changes in HRV occurred only in LL, in the standing position, including a 30% (p < 0.05) increase in resting heart rate (HR), a 50% (p < 0.05) decrease in total spectral power (TP) and a 77% (p < 0.05) decrease in high frequency activity (HF). When all the subjects were pooled, the changes in HRV in the supine position were correlated to the changes in aerobic capacities, i.e., HF, LF and TP were correlated to V̇O 2RCP and HR, HF and TP were correlated to PRCP. This study confirms the relationship between HRV and changes in aerobic capacity, therefore highlighting the potential value of HRV for monitoring altitude training adaptations

Communication between mother and infant (fetus or newborn)

International audienceWe measured changes in Heart Rate Variability (H.R.V.) while mother either talked about her baby to an adult (1) or communicated directly with the baby either vocally (2) or silently (3) (n=180 fetus, n=140 neonates).We previously showed that the % of fetus reacting to silent communication (3) was equal to those reacting to a vocal emission: 38% and 37% respectively while (1) elicited only 29% of responses.Babies reacted globally less than fetuses, but with the same proportion of responses: 27% for (2), 34% for (3) and 21% for (1). Here, to compare the 3 tests, H.R.V. was averaged every 30 sec. for 5 min. before, during and after each stimulus on 100 fetuses and 70 newborns. No significant effects were observed when computing all subjects, for some entered the pre-experimental phase in an agitated state (state 3 or 4) with a high H.R.V., while others were calm with a low H.R.V. (state 1 or 2). The latter increased its variability during stimulation while the high H.R.V. group decreased it.When analyzed separately, both groups became significant in all of the series. Babies, as a group, are less significant than fetuses, but also react to all three experimental conditions, including silent communication. This last unexpected result will be discussed for mothers who stated that they made extensive use of this mode of communication with their baby

Influence of "living high-training low" on aerobic performance and economy of work in elite athletes

This study tested the effects of "living high-training low" (Hi-Lo) on aerobic performance and economy of work in elite athletes. Forty endurance athletes (cross-country skiers, swimmers, runners) performed 13-18 consecutive days of training at 1,200 m altitude, by sleeping at 1,200 m (LL, n = 20) or in hypoxic rooms with 5-6 nights at 2,500 m followed by 8-12 nights at 3,000-3,500 m (HL, n = 20). The athletes were evaluated before (pre-), one (post-1) and 15 days (post-15) after Hi-Lo. Economy was assessed from two sub-maximal tests, one non-specific (cycling) and one specific (running or swimming). From pre- to post-1: V̇O2max increased both in HL (+ 7.8%, P < 0.01) and in LL (+ 3.3%, P < 0.05), peak power output (PPO) tended to increase more (P=0.06) in HL (+ 4.1%, P < 0.01) than in LL (+ 1.9%). At post-15, V̇O2max has returned to pre-values in both groups, PPO increased more (P < 0.05) in HL (+ 8.3%, P < 0.01) than in LL (+ 3.8%), V̇O2 and power at respiratory compensation point (RCP) increased more (P < 0.05) in HL (+ 9.5%, P < 0.01 and + 11.2%, P < 0.01) than in LL (+ 3.2 and + 3.3%). Cycling mechanical efficiency (8-5%) and economy during specific locomotion (7-7%) increased (P < 0.05) in both groups. This study shows that, for a similar increase V̇O2max HL had a greater increase in PPO than LL. The efficiency of Hi-Lo is also evidenced 15 days later by higher V̇O2 and power at RCP. This study emphasizes that during the post-altitude period, economy of work greatly increases in both groups

Living high-training low : tolerance and acclimatization in elite endurance athletes

The "living high-training low" (LHTL) model is frequently used to enhance aerobic performance. However, the clinical tolerance and acclimatization process to this intermittent exposure needs to be examined. Forty one athletes from three federations (cross-country skiers, n=11; swimmers, n=18; runners, n=12) separately performed a 13 to 18-day training at the altitude of 1,200 m, by sleeping either at 1,200 m (CON) or in hypoxic rooms (HYP), with an O2 fraction corresponding to 2,500 m (5 nights for swimmers and 6 for skiers and runners), 3,000 m (6 nights for skiers, 8 for swimmers and 12 for runners) and 3,500 m (6 nights for skiers). Measurements performed before, 1 or 15 days after training were ventilatory response (HVRe) and desaturation (δSaO2e) during hypoxic exercise, an evaluation of cardiac function by echocardiography, and leukocyte count. Lake Louise AMS score and arterial O2 saturation during sleep were measured daily for HYP. Subjects did not develop symptoms of AMS. Mean nocturnal SaO2 decreased with altitude down to 90% at 3,500 m and increased with acclimatization (except at 3,500 m). Leukocyte count was not affected except at 3,500 m. The heart function was not affected by LHTL. Signs of ventilatory acclimatization were present immediately after training (increased HVRe and decreased δSaO2e) and had disappeared 15 days later. In conclusion, LHTL was well tolerated and compatible with aerobic training. Comparison of the three patterns of training suggests that a LHTL session should not exceed 3,000 m, for at least 18 days, with a minimum of 12 h day-1 of exposure