Heart rate variability and altitude: implications for training

Transcription

1 Heart rate variability and altitude: implications for training Julien V Brugniaux Department of Physiology and Biophysics University of Calgary Alberta, Canada Acknowledgments University Paris 13 Jean-Paul Richalet Paul Robach Laurent Schmitt Aurélien Pichon Jérémy Cornolo Funding French Ministry of Sports International Olympic Committee Centre National de Ski Nordique, Prémanon, France 1

2 Oxygen transport O 2 CO 2 Pulmonary ventilation O 2 CO 2 Alveolo-capillary transfer of oxygen Right heart Left heart Transport of oxygen by the blood cell O 2 oxygen consumption CO 2 Diffusion of oxygen to the tissues Aerobic production of energy Cardiovascular function Hormonal control (long-term regulation) Epinephrine Norepinephrine Nervous control (short-termterm regulation) Sympathetic Parasympathetic 2

3 Autonomic nervous system Parasympathetic (ParaS) Sympathetic (S) Acetylcholine Norepinephrine HRV - Origin Blood pressure variations during the respiratory cycle induces variability into HR? respiratory sinus arrhythmia Mean R-R intervall variability Controlled breathing (15 breaths/min) Spontaneous breathing from Bernardi et al. 2001, J Hypertens;19:

4 What is HRV? R R P P T T P T T Q S Q S Time The duration between 2 heart beats (RR interval in msec) ) is not constant HRV - Analysis Temporal analysis? Quantitative description of the paras modulation? Long-term monitoring Spectral analysis? Qualitative information on the characteristics (amplitude, frequency) of the HR oscillations? Useful for non stationary signals, such as exercise or orthostatism 4

5 Spectral analysis Slow oscillations Fast oscillations RR Intervals (msec) Power spectrum (msec 2 /Hz) Time Frequency RR Intervals (msec) Power spectrum (msec 2 /Hz) Time Frequency Power spectrum (msec 2 /Hz) RR Intervals (msec) Time Frequency Spectral analysis V L F LF RR I n t e r v a l (msec) POWER SPECTRUM (msec 2 /Hz) HF Very Low Frequency (VLF) Supine Standing Hz Low Frequency (LF) Hz Time High Frequency (HF) Hz POWER SPECTRUM (msec 2 /Hz) Frequency Supine Frequency Standing position 5

6 Physiological significance Very Low Frequency? long term mechanisms of regulation Low Frequency? its physiological interpretation remains controversial? reflects both sympathetic and paras modulations High Frequency? parasympathetic influence associated with breathing frequency (respiratory sinus arrhythmia) LF/HF ratio? represents sympathovagal balance? a high LH/HF ratio = sympathetic predominance (orthostatic test) Acute hypoxia 6

7 Acute hypoxia pulmonary afference medulla? Ve. Carotid body Hypoxia? PaO 2? HR and Q. Arch of Aorta Local vasodilation due to? PaO 2 counteracts sympathetic vasoconstriction? Peripheral Vasodilation? Blood Pressure from Levine 2001, in: Handbook of clinical neurology;75: Sympathetic activity and HR control? ß-blockade * P<0.05 vs. sea level Mazzeo et al. 1994, Metabolism;43:

8 Effect on HRV & P<0.05 vs. spontaneous br * P<0.05 vs. Baseline; * P<0.01 from Bernardi et al. 2001, J Hypertens;19: Effect on HRV Decrease in HF Increase in LF (related( to respiratory frequency) LF/HF ratio is usually increased, so is the sympathetic modulation Controlled breathing (15 breaths/min) Decrease in total spectrum power of HRV Spontaneous breathing from Bernardi et al. 2001, J Hypertens;19:

9 Exercise HRmax is decreased Submaximal HR is increased * P<0.05 vs. normoxia P<0.05 vs. untrained Mollard et al. 2007, Eur J Appl Physiol;100: Exercise Increase in HR is not limited by ß-sympathetic or parasympathetic blockade Potential role of the a 1 -adrenergic receptor stimulated by NAd ß-sympathetic inhib. (propranolol) normoxia ß-sympathetic inhib. (propranolol) hypoxia? control normoxia? control hypoxia (FiO 2 =0.125%)? parasympathetic inhib. (glycopyrrolate) normoxia? parasympathetic inhib. (glycopyrrolate) hypoxia from Hopkins et al. 2003, J Physiol;550.2:

10 Chronic hypoxia Chronic hypoxia pulmonary afference medulla? Ve. Carotid body Hypoxia? PaO 2?? HR? Q. Arch of Aorta ß-downregulation M-upregulation? Peripheral Vasodilation? Blood Pressure from Levine 2001, in: Handbook of clinical neurology;75:

11 Sympathetic activity Days in altitude * P<0.05 vs. baseline (normoxia) P<0.05 vs. baseline (notmoxia) Mazzeo et al. 1998, J Appl Physiol;84: Sympathetic activity H1: 2 days at 4,350m H2: 13 days btwn 850-4,800m H3: 21 days at 4,800m * P<0.05 vs. SL; ** P<0.01 vs. SL Richalet et al. 1988, J Appl Physiol;65:

12 Cardiac receptors ß-adrenergic receptors Muscarinic receptors * P<0.05 Normoxia vs. Hypoxia in LV # P<0.05 Normoxia vs. Hypoxia in RV Favret et al. 2001, Am J Physiol Regul Integr Comp Physiol;280:730-8 Parasympathetic activity Relative increase due to paras blockade is greater at altitude vs. seal level (109% vs. 86%, resp.) Enhanced parasympathetic neural activity accounts for the lowering of HR? Sea level Control? Sea level Glycopyrrolate? 5,260m Control? 5,260m Glycopyrrolate 9 wks at 5,260m * P<0.05 Sea Level vs. 5,260m Control + P<0.05 Sea Level vs. 5,260m Glycopyrrolate Power output (Watts) Boushel et al. 2001, Circulation;104:

13 Heart Rate * P<0.05 vs. sea level Mazzeo et al. 1994, Metabolism;43: Effect on HRV 1 day, 1 wk at 4,970m 5,050m Total spectrum power is increased? HF? LF * P<0.05 vs. sea level Perini et al. 2003, Eur J Appl Physiol;90: from Bernardi et al. 1998, Clin Sci (Lond);95:

14 Exercise HRmax is decreased for altitudes above 3,500m, due to: - decreased response to catecholaminergic stimulation (ß-( adrenergic receptors) - increased parasympathetic tone 9 wks at 5,260m Power output (Watts) * P<0.05 Sea Level vs. 5,260m Control + P<0.05 Sea Level vs. 5,260m Glycopyrrolate? Sea level Control? Sea level Glycopyrrolate? 5,260m Control? 5,260m Glycopyrrolate Boushel et al. 2001, Circulation;104: Intermittent hypoxia 14

15 Intermittent hypoxia Models of intermittent hypoxic exposure are multiple: - sleep apnea - altitude workers (Peru for example) - intermittent hypoxic training Intermittent hypoxic exposure is different from repeated acute exposures to hypoxia or discontinuous chronic hypoxia Remnant effect of hypoxia * P<0.05 vs. baseline + P<0.05 hypoxia vs. hypercapnia FiO 2 =0.12% P<0.05 vs. SL P<0.05 vs. RSL Remnant effects last longer after continuous than discontinuous hypoxia from Boussuges et al. 2000, Am J Respir Crit Care Med;161: from Xie et al. 2001, J Appl Physiol;91:

16 Acute Exercise Mechanisms * P<0.05 untrained vs. trained * P<0.05 vs. pre exercise Greiwe et al. 1999, J Appl Physiol;86:531-5 Tsuchimochi et al. 2002, Am J Physiol Heart Circ Physiol;283:

17 Kinetic + after: Rapid drop in CSNA precedes HR decrease + after: Gradual decrease in HR with no change in CSNA? mid to late: Both CSNA and HR are elevated? initial: Increase in CSNA precedes tachycardia from Tsuchimochi et al. 2002, Am J Physiol Heart Circ Physiol;283: HRV: methodological consideration 60% of PVO 2 max 70% of PVO 2 max Power spectrum density (ms²/hz) Frequency (Hz) Time (sec) Power spectrum density (ms²/hz) Frequency (Hz) Time (sec) 80% of PVO 2 max Power spectrum density (ms²/hz) Frequency (Hz) Time (sec) from Pichon et al. 2004, Med Sci Sports Exerc;36:

18 HRV: methodological consideration The major influence of ventilation challenges the validity of standard HRV indices for assessing autonomic control of heart rate during strenuous exercise ** P<0.01 vs. rest from Pichon et al. 2004, Med Sci Sports Exerc;36: Time course of recovery from exercise HR (time constant) recovery from an acute exercise is faster in subjects with moderate training load, whatever their fitness level Early recovery depends on the intensity of the exercise a P<0.05; aa P<0.01 IV 85 vs. IV 93 or CO 80 vs. CO 93 b P<0.05 IV 85 vs. CO 85 IV: 7x3min of vvo 2 max, 2min rec. CO: 21min of vvo 2 max Kaikkonen et al. in press, Scand J Med Sci Sports from Buchheit et al. 2006, Am J Physiol Heart Circ Physiol;291:

19 Remnant effect of exercise The elevated resting HR post-exercise, associated with a high sympathetic modulation, can last for up to 24h before the race 1 night after the race 75km X-country ski 2 nights after the race 75km X-country ski A parasympathetic rebound is observed between 24 and 48h post-exrecise (long and intense) from Hautala et al. 2001, Clin Physiol;21: Remnant effect of exercise - trained vs. untrained? Control group? Training groups at rest 10min after exercise 20min after exercise * P<0.05 vs. before training from Yamamoto et al. 2001, Med Sci Sports Exerc;33:

20 Remnant effect of exercise - trained vs. untrained Correlation between baseline HF component and response to 8 wk of aerobic training? Moderate-volume training group? High-volume training group Importance of HRV measurement to design individual training plans from Hautala et al. 2003, Am J Physiol Heart Circ Physiol;285: Endurance Training 20

21 Moderate intensity - total power of HRV Neurovegetative activity, as represented by power spectrum (PSD), is greater in athletes than in sedentary individuals Sedentary senior 12mo of training Young individual 6mo of training from Okazaki et al. 2005, J Appl Physiol;99: Moderate intensity sympathetic activity Sympathetic component is decreased after training 8wk 6 session/wk 70-80% of HRmax 30 or 60min/session from Tulppo et al. 2003, J Appl Physiol;95:

22 Moderate intensity paras activity and HR Parasympathetic component is increased after training from Tulppo et al. 2003, J Appl Physiol;95: High intensity sympathetic activity Increase in the sympathetic component with high intensity training, rapidly reversible 50% TL: 50% of the maximum training load (TL), ~3mo before WC 100% TL: 100% of the maximum TL, ~20d before WC W-CHAMP: during the competition, TL markedly reduced * P<0.05 among the different recording sessions from Iellamo et al. 2004, Med Sci Sports Exerc;36:

23 High intensity parasympathetic activity Decrease in the parasympathetic component with high intensity training detrained After ~3mo of training ~20d before WC Increase in the LF power Increase in HR associated with the conditioning period from Iellamo et al. 2002, Circulation;105: Over-reaching Can be characterized by: - a decreased total power of HRV with a LF predominance - an increased supine HR - a slow cardiac recovery from exercise But has also been described as inducing paras modulation Can be considered as normal fatigue and not necessary associated with a drop in performance Can be observed during conditioning period of training when non-pathological 23

24 Over-training Can be characterized by: - a large increase in total power of HRV with a high HF activity (endurance sports) - a decreased supine HR - a fast cardiac recovery from exercise Is always associated with a decrease in performance even in the absence of autonomic symptoms 6-d training camp? before after * P<0.05 test1 vs.test2 ** P<0.01 test1 vs.test2 Hedelin et al. 2000, Med Sci Sports Exerc;32: Orthostatic hypotension Athletes have a lower tolerance to Tilt test vs. sedentary (proportional to their training status) This might be due to: - structural training adaptations:? arterial and veinous compliance,? cardiac compliance and hypertrophy,? blood volume - decrease in baroreflex sensitivity - decrease in autonomic nervous system control on baroreflex, related to the parasymathetic modulation induced by training Orthostatic hypotension can be associated with overtraining 24

25 HRV and Training Follow-up Normoxia better x Pre- and post-season differences Performance is increased,, but resting HR do not change Gender differences seem to exist? Parasympathetic activity is greater in females than in males * P<0.05 test1 vs. test2 ** P<0.01 test1 vs. test2 from Hedelin et al. 2000, Scand J Med Sci Sports;10:

26 Pre- and post-season differences resting HR is decreased and performance is increased No alteration in sympathetic or paras markers Indirect marker of HR vagal reflex control could have been improved * P<0.05 between body position # P<0.05 pre vs. post Specific training adaptation (?( in blood volume and cardiac dimension is less in swimmers than in runners) may explain these divergence These discrepancies may reflect methodological limitation in the use of HRV for long-term variations pre post from Perini et al. 2006, Eur J Appl Physiol;97: Training individualization Low: 65% of HRmax, 40min High: 85% of HRmax, 30min + warm-up/cool-down at 65%, 5min * Max 2 consequent high-intensity exercises Max 2 consequent resting days from Kiviniemi et al. 2007, Eur J Appl Physiol;101:

27 Training individualization * P<0.05 between groups P<0.05 within the groups Kiviniemi et al. 2007, Eur J Appl Physiol;101: HRV and Training Follow-up Hypoxia 27

28 Summary Hypoxia vs. Training Hypoxia Training Training HR HRV HRV total LF HRV total HF HRV total LF HF LF HF SL Acute Chronic Moderate-intensity High-intensity Opposite or cumulative effects + possible remnant effects of both hypoxia and exercise Altitude training - mild vs. moderate hypoxia * P<0.05 vs. pre-test; # P<0.05 1,200m vs. 1,850m Same relative training loads induce positive HRV adaptations (?( HF SU and LF ST ) at 1,200m and improve performance, but not at 1,850m HF sensitivity may help predict performance alteration from Schmitt et al. 2006, Int J Sports Med;27:

29 Intermittent hypoxia - LHTL What are the influences of the remaining effects of exercise and/or hypoxia? HR or S test HR or S test Exercise Rest 2 1 Hypoxia Rest time Hypoxia Rest 1 Exercise Rest time Cornolo, unpublished LHTL Remnant effects of exercise Altitude does not affect intense-exercising exercising remnant effects on HRV in a well-adapted population Living in altitude does not impair the autonomic response to training * P<0.05 ; ** P<0.01 from Cornolo et al. 2005, Med Sci Sports Exerc;37:

30 LHTL Remnant effects of hypoxia * P<0.05 before vs. after; ** P<0.01 P<0.05 LHTL vs. LLTL after * P<0.05 vs. PRE Altitude exposure counteracts aerobic training induced alterations in autonomic control, but does not prevent further enhancement at the end of the exposure Povea et al. 2005, High Alt Med Biol;6: from Cornolo et al. 2006, Eur J Appl Physiol;96: Intermittent hypoxia - LHTL HR or S test 2 1 Exercise Rest Hypoxia Rest time LHTL can not be considered as repeated acute exposures to hypoxia This needs to be taken into account to controlling training with HRV from Cornolo, unpublished 30

31 Take Home Message HRV is more useful on a day to day basis than for long-term comparison Overtraining being hard to diagnose, controlling training using HRV becomes very useful Training follow up over altitude training is even more important Few is known about the different models of intermittent hypoxia ( LH-TL, LL-TH ) 31