Heart Rate and Hydration Template New Logo...References!...
Transcript of Heart Rate and Hydration Template New Logo...References!...
The Influence of Hydration on Heart Rate
Written By: William M. Adams, MS, ATC and Douglas J. Casa, PhD, ATC
Summary of Findings • Scientific Definitions: Hypohydration is the steady-‐state condition of decreased total body
water. Dehydration is the process of losing body water (eg, during exercise). • Body mass losses as small as 2% have been shown to result in an increase in cardiovascular
strain and subsequently decrease performance during exercise.1–6 Exercise in the heat further exacerbates cardiovascular strain, thus causing further decrements in performance.7
• Results have shown that for every 1% decrease in body mass during exercise in the heat there is an increase in heart rate of 3.29 beats/min. This equates to an increase in heart rate of 10 beats/min if an athlete is 3% dehydrated.8
• Exercise at a fixed and variable intensity has shown an increase in heart rate of 3.55 and 1.39 beats/min respectively during exercise in the heat.8
• In order to maximize performance athletes should: 1) ensure proper hydration before exercise, 2) have knowledge of individual fluid needs (influenced by intensity of exercise, environmental conditions, body size, etc.) since each athlete’s fluid needs are different from one another and 3) Drink according to thirst sensation to minimize body mass losses of >2% since thirst is a good indicator of hydration status.10
-‐3 -‐2 -‐1 0 1 2 3 4 5 6 7
Change in HR per every additional 1% Change in BML (bpm/ΔBML)
Overall Armstrong 1997 Armstrong 1997 Arnaoutis 2012 Arnaoutis 2012 Below 1995 Below 1995 Casa 2010 Casa 2010 Ebert 2007 Ebert 2007 Fugii 2008 Ganio 2006 Ganio 2006 Gonzalez-‐Alonso Gonzalez-‐Alonso Gonzalez-‐Alonso Gonzalez-‐Alonso Gonzalez-‐Alonso Gonzalez-‐Alonso Gonzalez-‐Alonso Ishijima 2009 Ishijima 2009 Kenecick 2006 Kenecick 2007 Lopez 2011 Montain 1992 Montain 1992 Montain 1992 Montain 1992 Montain 1996 Montain 1996 Montain 1996 Montain 1996 Montain 1996 Wingo 2004 Wingo 2005 Wingo 2005
References 1. González-‐Alonso J, Mora-‐Rodríguez R, Below PR, Coyle EF. Dehydration markedly impairs cardiovascular function in hyperthermic endurance athletes during exercise. J Appl Physiol Bethesda Md 1985. 1997;82(4):1229–1236. 2. González-‐Alonso J, Mora-‐Rodríguez R, Below PR, Coyle EF. Dehydration reduces cardiac output and increases systemic and cutaneous vascular resistance during exercise. J Appl Physiol Bethesda Md 1985. 1995;79(5):1487–1496. 3. González-‐Alonso J, Mora-‐Rodríguez R, Coyle EF. Stroke volume during exercise: interaction of environment and hydration. Am J Physiol Heart Circ Physiol. 2000;278(2):H321–330. 4. Montain SJ, Sawka MN, Latzka WA, Valeri CR. Thermal and cardiovascular strain from hypohydration: influence of exercise intensity. Int J Sports Med. 1998;19(2):87–91. doi:10.1055/s-‐2007-‐971887. 5. Montain SJ, Coyle EF. Influence of graded dehydration on hyperthermia and cardiovascular drift during exercise. J Appl Physiol Bethesda Md 1985. 1992;73(4):1340–1350. 6. Judelson DA, Maresh CM, Anderson JM, et al. Hydration and muscular performance: does fluid balance affect strength, power and high-‐intensity endurance? Sports Med Auckl Nz. 2007;37(10):907–921. 7. Crandall CG, González-‐Alonso J. Cardiovascular function in the heat-‐stressed human. Acta Physiol Oxf Engl. 2010;199(4):407–423. 8. Adams WM, Ferraro EM, Huggins RA, Casa DJ. The Influence of Body Mass Loss on Changes in Heart Rate During Exercise in the Heat: A Systematic Review. J Strength Cond Res. In Review. 9. Casa DJ, Stearns RL, Lopez RM, et al. Influence of hydration on physiological function and performance during trail running in the heat. J Athl Train. 2010;45(2):147–156. 10. Goulet EDB. Dehydration and endurance performance in competitive athletes. Nutr Rev. 2012;70 Suppl 2:S132–136.
Practical Applications • Athletes should maintain an appropriate level of hydration prior to the start of an endurance
event and aim to minimize fluid losses during the event to attenuate any performance decrements.
• Ensuring proper hydration during exercise in the heat is of utmost importance as the added heat stress amplifies the cardiovascular strain and resulting performance decrements found with dehydration.
• Although there is a small difference in heart rate for every 1% decrease in body mass loss during variable (real-‐world competition situations) intensity exercise, overall performance in these situations is adversely affected. Someone who is exercising at a certain intensity will be exercising with a higher heart rate if they are dehydrated.
• During competition, an athlete who is hydrated is able to compete at a higher intensity with a lower heart rate, which improves overall performance.
• In competing in sports, which expose athletes to heat stress, it is important that athletes undergo a period of heat acclimatization in addition to maintaining an appropriate level of hydration. Heat acclimatization is a series of cardiovascular and other physiological adaptations that improves heat tolerance and improves the ability of athletes performing in the heat.
Looking Ahead • Further research is needed examining the effects of dehydration on heart rate during real-‐world
situations. Conclusions that have been made looking at the effects of dehydration on heart rate lack ecological and external validity as these studies occur in the laboratory setting under fixed exercise intensity, which is unrealistic when applying to competition.
• A synthesis of heart rate changes due to dehydration under varying environmental conditions is needed in order to identify the added effect of temperature on changes in heart rate with increasing levels of dehydration.