Individual Variation in the Reduction of Heart Rate and Performance at Lactate Thresholds in Acute Normobaric Hypoxia

Abstract

Heart rate monitoring and lactate measurements are used to control exercise intensity during training at moderate altitude although there is some uncertainty about hypoxia-induced changes in these parameters at equivalent submaximal exercise intensities compared to normoxia. To study the influence of acute normobaric hypoxia (FiO₂ 0.15) on heart rate and performance at the individual anaerobic lactate threshold (IAT), at the 4 mmol · l^-1 threshold (AT) and at an intensitiy requiring 80 % of V·O_2max measured in the respective environment, 20 endurance-trained male athletes performed an incremental treadmill test in normoxia and normobaric hypoxia. During exercise in normobaric hypoxia, heart rate and velocity were significantly (p < 0.001) reduced with a wide individual variation at the IAT (range: - 1 to - 17 min^-1, - 0.3 to - 3.5 km · h^-1), at the AT (- 2 to - 13 min^-1, - 0.2 to - 3.3 km · h^-1) as well as at an intensity requiring 80 % of V·O_2max (0 to - 18 min^-1, - 1.1 to - 3.7 km · h^-1). Relative V·O₂ at the lactate thresholds expressed as a percentage of V·O_2max was not significantly different compared to normoxia (86 ± 6 % vs. 84 ± 5 %, IAT; 90 ± 5 % vs. 88 ± 6 %, AT), but also showed a considerable individual variation. In conclusion, heart rate and performance have to be reduced individually to a varying extent during exercise in a hypoxic environment in order to achieve an equivalent intensity compared to exercise in normoxia.

Altitude - athletes - lactate threshold - oxygen uptake - ventilation

References

• 1 Adams W C, Bernauer E M, Dill D B, Bomar Jr J B. Effects of equivalent sea-level and altitude training on V·O_2max and running performance.  J Appl Physiol. 1975;  39 262-266
• 2 Bailey D M, Davies B, Romer L, Castell L, Newsholm E, Gandy G. Implications of moderate altitude training for sea-level endurance in elite distance runners.  Eur J Appl Physiol. 1998;  78 360-368
• 3 Billat V L, Lepretre P M, Heubert R P, Koralsztein J P, Gazeau F P. Influence of acute moderate hypoxia on time to exhaustion at the vV·O_2max in unacclimatized runners.  Int J Sports Med. 2003;  24 9-14
• 4 Bouissou P, Guezennec C Y, Defer G, Pesquies P. Oxygen consumption, lactate accumulation, and sympathetic response during prolonged exercise under hypoxia.  Int J Sports Med. 1987;  8 266-269
• 5 Brosnan M, Martin D T, Hahn A G, Gore C J, Hawley J A. Impaired interval exercise responses in elite female cyclists at moderate simulated altitude.  J Appl Physiol. 2000;  89 1819-1824
• 6 Burtscher M, Nachbauer W, Baumgartl P, Philadelphy M. Benefits of training at moderate altitude versus sea level training in amateur runners.  Eur J Appl Physiol. 1996;  74 558-563
• 7 Coen B, Schwarz L, Urhausen A, Kindermann W. Control of training in middle- and long-distance running by means of the individual anaerobic threshold.  Int J Sports Med. 1991;  12 519-524
• 8 Dickhuth H-H, Yin L, Niess A, Röcker K, Mayer F, Heitkamp H-C, Horstmann T. Ventilatory, lactate-derived and catecholamine thresholds during incremental treadmill running: relationship and reproducibility.  Int J Sports Med. 1998;  20 122-127
• 9 Dill D B, Adams W C. Maximal oxygen uptake at sea level and at 3090 m altitude in high school champion runners.  J Appl Physiol. 1971;  30 854-859
• 10 Emonson D L, Aminuddin R L, Wight R L, Scroop G C, Gore C J. Training-induced increases in sea level V·O_2max and endurance are not enhanced by acute hypobaric exposure.  Eur J Appl Physiol. 1997;  76 8-12
• 11 Foster C, Fitzgerald D J, Spatz P. Stability of the blood lactate-heart rate relationship in competitive athletes.  Med Sci Sports Exerc. 1999;  31 578-582
• 12 Fulco C S, Rock P B, Cymerman A. Improving athletic performance: is altitude residence or altitude training helpful?.  Aviat Space Environ Med. 2000;  71 162-171
• 13 Heck H, Mader A, Hollmann W. Justification of the 4 mmol · l^-1 threshold.  Int J Sports Med. 1985;  6 117-130
• 14 Heitkamp H-C, Holdt M, Scheib K. The reproducibility of the 4 mmol/l lactate threshold in trained and untrained women.  Int J Sports Med. 1991;  12 363-368
• 15 Koistinen P, Takala T, Martikkala V, Leppäluoto J. Aerobic fitness influences the response of maximal oxygen uptake and lactate threshold in acute hypobaric hypoxia.  Int J Sports Med. 1995;  26 78-81
• 16 Lawler J, Powers S K, Thompson D. Linear relationship between V·O_2max and V·O_2max decrement during exposure to acute hypoxia.  J Appl Physiol. 1988;  64 1486-1492
• 17 Levine B D, Stray-Gundersen J. “Living high - training low”: Effect of moderate-altitude acclimatization with low-altitude training on performance.  J Appl Physiol. 1997;  83 102-112
• 18 Mairbäurl H, Schobersberger W, Humpeler E, Hasibeder W, Fischer W, Raas E. Beneficial effects of exercising at moderate altitude on red cell oxygen transport and on exercise performance.  Pflügers Arch. 1986;  406 594-599
• 19 Meeuwsen T, Hendriksen I JM, Holewijn M. Training-induced increases in sea-level performance are enhanced by acute intermittent hypobaric hypoxia.  Eur J Appl Physiol. 2001;  84 283-290
• 20 Milledge J S. High altitude. Harries M, Williams C, Stansih WD, Micheli LJ Oxford Textbook of Sports Medicine. New York, Oxford, Tokyo; Oxford University Press 1996: 217-230
• 21 Mizuno M, Juel C, Bro-Rasmussen T, Mygind E, Schibye B, Rasmussen B, Saltin B. Limb skeletal muscle adaptation in athletes after training at altitude.  J Appl Physiol. 1990;  68 496-502
• 22 Niess A M, Fehrenbach E, Strobel G, Roecker K, Schneider E M, Buergler J, Fuss S, Lehmann R, Northoff H, Dickhuth H H. Evaluation of stress responses to interval training at low and moderate altitudes.  Med Sci Sports Exerc. 2003;  35 263-269
• 23 Pugh L GCE. Athletes at altitude.  J Physiol. 1967;  192 619-646
• 24 Robergs R A, Quintana R, Parker D L, Frankel C C. Multiple variables explain the variability in the decrement in V·O_2max during acute hypobaric hypoxia.  Med Sci Sports Exerc. 1998;  30 869-879
• 25 Roskamm H, Landry F, Samek L, Schlager M, Weidemann H, Reindell H. Effects of a standardized ergometer training program at three different altitudes.  J Appl Physiol. 1969;  27 840-847
• 26 Stegmann H, Kindermann W. Comparison of prolonged exercise tests at the individual anaerobic threshold and at the fixed anaerobic threshold of 4 mmol · l^-1 lactate.  Int J Sports Med. 1982;  3 105-110
• 27 Stegmann H, Kindermann W, Schnabel A. Lactate kinetics and individual anaerobic threshold.  Int J Sports Med. 1981;  2 160-165
• 28 Terrados N, Jansson E, Sylven C, Kaijser L. Is hypoxia a stimulus for synthesis of oxidative enzymes and myoglobin?.  J Appl Physiol. 1990;  68 2369-2372
• 29 Terrados N, Melichna J, Sylven C, Jansson E, Kaijser L. Effects of training at simulated altitude on performance and muscle metabolic capacity in competitive road cyclists.  Eur J Appl Physiol. 1988;  57 203-209
• 30 Terrados N, Mizuno M, Andersen H. Reduction in maximal oxygen uptake at low altitudes; role of training status and lung function.  Clin Physiol. 1985;  5 75-79
• 31 Wolski L A, McKenzie D C, Wenger H A. Altitude training for improvements in sea level performance. Is there scientific evidence or benefit?.  Sports Med. 1999;  22 251-263