The Reliability and Adaptive Responses of Gross Efficiency in Hot Ambient Conditions

Abstract

This study evaluated the reliability and adaptive responses of cycling gross efficiency (GE) performed at different intensities, across 3 trials in simulated hot (~30°C) temperatures. Twelve cyclists performed 3 hot (30±0.7ºC and RH of 50±2.9%) GE sessions, comprising 3 sub-maximal work rates of 150 W, 200 W and 250 W (5-min each), separated by 24-h. Paired t-tests revealed no changes (P>0.05) in GE between trials. 95% limits of agreement demonstrated random error in GE ranging from 1.71% (250 W; trials 1–2) to 2.32% (200 W; trials 1–2), leading to a total error of -2.45%. The coefficient of variation (CV%) ranged from 3.1±0.4% (250 W; trials 1–2) to 4.0±0.5% (200 W; trials 1–2). Among non-acclimated, well-trained cyclists, GE did not change between consecutive submaximal cycling bouts performed in the heat. The reliability of GE when cycling in the heat (CV=3.1–4.0%) is similar to that reported among cyclists in thermoneutral environments. Whilst the interpretation of GE reliability was dependent on the adopted statistical technique, it can be small enough to detect typical changes owing to heat exposure.

Key words

thermoregulation - acclimation - temperature - oxygen consumption - cycling

• References

• 1 Atkinson G, Nevill AM. Statistical methods for assessing measurement error (reliability) in variables relevant to sports medicine. Sports Med 1998; 26: 217-238
• 2 Batterham A, Atkinson G. How big does my sample need to be? A primer on the murky world of sample size estimation?. Phys Ther Sport 2005; 6: 153-163
• 3 Carter J, Jeukendrup AE. Validity and reliability of three commercially available breath-by-breath respiratory systems. Eur J Appl Physiol 2002; 86: 435-441
• 4 Chen TI, Tsai PH, Lin JH, Lee NY, Liang MT. Effect of short-term heat acclimation on endurance time and skin blood flow in trained athletes. Open Access J Sports Med 2013; 4: 161-170
• 5 Corbett J, Barwood MJ, Ouzounoglou A, Thelwell R, Dicks M. Influence of Competition on Performance and Pacing during Cycling Exercise. Med Sci Sports Exerc 2012; 44: 509-515
• 6 Coyle EF. Improved muscular efficiency displayed as Tour de France champion matures. J Appl Physiol 2005; 98: 2191-2196
• 7 Daanen HA, van Es E, de Graaf JL. Heat strain and gross efficiency during endurance exercise after lower, upper or whole body precooling in the heat. Int J Sport Med 2006; 27: 379-388
• 8 Drust B, Rasmussen P, Mohr M, Nielsen B, Nybo L. Elevations in core and muscle temperature impairs repeated sprint performance. Acta Physiol Scand 2005; 183: 181-190
• 9 Ebert TR, Martin DT, Bullock N, Mujika I, Quod MJ, Farthing LA, Burke LM, Withers RT. Influence of hydration status on thermoregulation and cycling hill climbing. Med Sci Sports Exerc 2007; 39: 323-329
• 10 Garby L, Astrup A. The relationship between the respiratory quotient and the energy equivalent of oxygen during simultaneous glucose and lipid oxidation and lipogenesis. Acta Physiol Scand 1987; 129: 443-444
• 11 Garrett AT, Rehrer NJ, Patterson MJ. Induction and decay of short-term heat acclimation in moderately and highly trained athletes. Sports Med 2011; 41: 757-771
• 12 Garrett AT, Creasy R, Rehrer NJ, Patterson MJ, Cotter JD. Effectiveness of short-term heat acclimation for highly trained athletes. Eur J Appl Physiol 2012; 112: 1827-1837
• 13 Greenleaf JE. Lack of artificial acclimatization to heat in physically fit subjects. Nature 1964; 203: 1072
• 14 Harriss DJ, Atkinson G. Ethical standards in sport and exercise science research: 2014 update. Int J Sports Med 2013; 34: 1025-1028
• 15 Hettinga FJ, De Koning JJ, de Vrijer A, Wust RC, Daanen HA, Foster C. The effect of ambient temperature on gross-efficiency in cycling. Eur J Appl Physiol 2007; 101: 465-471
• 16 Hettinga F, de Koning JJ, Broersen FT, Van Geffen P, Foster C. Pacing strategy and the occurrence of fatigue in 4000-m cycling time trials. Med Sci Sports Exerc 2006; 38: 1484-1491
• 17 Hopker JG, Jobson SA, Gregson HC, Coleman DA, Passfield L. Reliability of cycling gross efficiency using the douglas bag method. Med Sci Sports Exerc 2012; 44: 290-296
• 18 Hopker JG, Coleman DA, Wiles JD. Differences in efficiency between trained and recreational cyclists. Appl Physiol Nutr Metab 2007; 32: 1036-1042
• 19 Hopkins WG, Marshall SW, Batterham AM, Hanin J. Progressive statistics for studies in sports medicine and exercise science. Med Sci Sports Exerc 2009; 41: 3-12
• 20 Horowitz JF, Sidossis LS, Coyle EF. High efficiency of type I fibers improves performance. Int J Sports Med 1994; 15: 152-157
• 21 Hulleman M, De Koning JJ, Hettinga FJ, Foster C. The effect of extrinsic motivation on cycle time trial performance. Med Sci Sports Exerc 2007; 39: 709-715
• 22 Hsu AR, Hagobian TA, Jacobs KA, Attallah H, Friedlander AL. Effects of heat removal through the hand on metabolism and performance during cycling exercise in the heat. Can J Appl Physiol 200; 30: 87-104
• 23 Libert JP, Candas V, Vogt JJ. Modifications of sweating responses to thermal transients following heat acclimation. Eur J Appl Physiol 1983; 50: 235-246
• 24 Moseley L, Jeukendrup AE. The reliability of cycling efficiency. Med Sci Sports Exerc 2001; 33: 621-627
• 25 Nielsen B, Hales JR, Strange S, Christensen NJ, Warberg J, Saltin B. Human circulatory and thermoregulatory adaptations with heat acclimation and exercise in a hot, dry environment. J Physiol 1993; 460: 467-485
• 26 Noordhof DA, de Koning JJ, van Erp T, van Keimpema B, de Ridder D, Otter R, Foster C. The between and within day variation in gross efficiency. Eur J Appl Physiol 2010; 109: 1209-1218
• 27 Nybo L. Hyperthermia and fatigue. J Appl Physiol 2008; 104: 871-878
• 28 Pandolf KB, Burse RL, Goldman RF. Role of physical fitness in heat acclimatisation, decay, and reinduction. Ergonomics 1977; 20: 399-408
• 29 Pandolf KB. Effects of physical training and cardiorespiratory fitness on exercise-heat tolerance: recent observations. Med Sci Sports Exerc 1979; 11: 60-65
• 30 Ramanathan NJ. A weighting system for mean surface temperature of the human body. J Appl Physiol 1964; 19: 521-533
• 31 Stone MR, Thomas K, Wilkinson M, Jones AM, St Clair Gibson A, Thompson KG. Effects of Deception on Exercise Performance: Implications for Determinants of Fatigue in Humans. Med Sci Sports Exerc 2012; 44: 534-541
• 32 Tatterson AJ, Hahn AG, Martin DT, Febbraio MA. Effects of heat stress on physiological responses and exercise performance in elite cyclists. J Sci Med Sport 2000; 3: 186-193
• 33 Taylor NAS, Cotter JD. Heat adaptation: guidelines for the optimisation of human performance. Int Sportsmed J 2006; 7: 1-37
• 34 Tucker R, Rauch L, Harley YXR, Noakes TD. Impaired exercise performance in the heat is associated with an anticipatory reduction in skeletal muscle recruitment. Pflugers Arch 2004; 448: 422-430
• 35 Wall BA, Watson G, Peiffer JJ, Abbiss CR, Siegel R, Laursen PB. Current hydration guidelines are erroneous: dehydration does not impair exercise performance in the heat. Br J Sports Med 2013;
• 36 Wasserman K, Whipp BJ, Koyl SN, Beaver WL. Anaerobic threshold and respiratory gas exchange during exercise. J Appl Physiol 1973; 35: 236-243