#75 - Physiology of exercise in extreme environments: sex as a biological variable with Dr Nisha Charkoudian
Dec 3, 2023
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Dr Nisha Charkoudian, expert on effects of extreme environments on exercise capacity, discusses dehydration, effects of humid vs dry environments, importance of including both sexes in studies, and thermoregulation and blood pressure with aging. Very interesting chat.
Including diverse populations in exercise research is crucial for generalizability and reducing health disparities.
Understanding the physiological responses and adaptations to extreme environments, such as heat and altitude, is essential for individual health and performance.
Recognizing and managing the biological differences between men and women in blood pressure and body temperature regulation is important for optimizing exercise performance and safety.
Deep dives
Including Diversity in Exercise Research
The podcast episode emphasizes the importance of including diverse populations in exercise research. Historically, studies have focused primarily on young, white males, leading to a lack of generalizability and potential health disparities. Associate Professor Nisha Sharkudian discusses the need to consider sex as a biological variable, highlighting sex differences in responses to exercise, particularly in extreme environments. While it may not always be possible to have an equal representation of males and females in studies, leaving a subgroup for comparison can provide valuable insights. The conversation also emphasizes the need for more research on older populations and the importance of considering individual differences in cardiovascular regulation and thermoregulation.
Understanding Extreme Environments
The podcast explores extreme environments, including extreme heat, extreme cold, and high altitude. With the increasing attention on climate change, understanding the physiological responses and adaptations to these environments is crucial. Professor Nisha Sharkudian discusses her work in identifying the physiological pathways and how they can be improved to enhance individual health and performance in extreme environmental exposures. The conversation also emphasizes the impact of environmental factors like humidity on thermoregulation and the role of vasodilation and blood pressure regulation in maintaining body temperature.
Sex Differences in Blood Pressure and Body Temperature Regulation
The discussion delves into the biological differences between men and women in blood pressure and body temperature regulation, specifically in extreme environments. Research has shown that women tend to have lower blood pressure and more vasodilation response compared to men, potentially aiding in heat dissipation. However, women are also at a higher risk of orthostatic intolerance in the heat, where low blood pressure can lead to dizziness or fainting upon standing up. Recognizing and managing these differences is important in optimizing exercise performance and safety for both men and women.
Importance of including women in research studies
It is crucial to include women in research studies, even if there may be constraints or limitations in terms of funding or controlling for the menstrual cycle. Research has shown that women's thermoregulatory responses, such as sweating and adaptation to heat acclimation, differ from men. However, these differences do not impact the risk of heat illness. The inclusion of women in research studies allows for a more comprehensive understanding of human physiology and avoids the tendency to consider men as the default human.
The influence of progesterone on core temperature
Progesterone, particularly during the mid-luteal phase of the menstrual cycle, has been found to elevate body core temperature in women. This shift results in a higher baseline temperature during the second half of the menstrual cycle, commonly known as the luteal phase. While the mechanisms behind this thermogenic effect are not fully understood, there is a correlation between progesterone levels and higher core temperature. However, the sensation of feeling cold does not necessarily indicate that a person is actually cold, as there can be a distinction between perceived temperature and actual temperature.
Dr Glenn McConell chats with Associate Professor Nisha Charkoudian from the US Army Research Institute of Environmental Medicine, Natick, Massachusetts, USA. She is an expert on the effects of extreme environments on exercise capacity. We talked about dehydration, electrolytes, effects of humid vs dry environments etc. We also discussed the importance of considering sex as a biological variable. This included including both sexes in studies even if underpowered to examine both. We then discussed the importance of conducting more studies on thermoregulation and blood pressure with aging. A very interesting chat. 0:00. Introduction 3:45. What is the definition of extreme environments? 5:05. Who gets the hottest/has the most issues with heat? 9:00. Effects of humid vs dry environments and hydration 12:05. Should drink until urine is clear before a race? 16:10. Should people worry about electrolytes? 20:44. Sex as a biological variable. Women not more fragile etc 23:30. Sex differences in heat acclimation 25:20. No difference in risk of heat stroke between the sexes 25:50. If no difference then just study one sex? 27:38. Need to include women even if small sample 32:34. Even if underpowered it’s ok to include both sexes 40:20. Gender vs sex, binary vs non binary etc 42:00. Women and blood flow/blood pressure/heat etc 49:05. Body surface area and heat/cold 52:01. Progesterone and body core temperature 54:25. Aging and thermogerulation 57:35. Takeaway messages 1:00:44. Outro Inside Exercise brings to you the who's who of research in exercise metabolism, exercise physiology and exercise’s effects on health. With scientific rigor, these researchers discuss popular exercise topics while providing practical strategies for all. The interviewer, Emeritus Professor Glenn McConell, has an international research profile following 30 years of Exercise Metabolism research experience while at The University of Melbourne, Ball State University, Monash University, the University of Copenhagen and Victoria University. He has published over 120 peer reviewed journal articles and recently edited an Exercise Metabolism eBook written by world experts on 17 different topics (https://link.springer.com/book/10.1007/978-3-030-94305-9). Connect with Inside Exercise and Glenn McConell at: Twitter: @Inside_exercise and @GlennMcConell1 Instagram: insideexercise Facebook: Glenn McConell LinkedIn: Glenn McConell https://www.linkedin.com/in/glenn-mcconell-83475460 ResearchGate: Glenn McConell Email: glenn.mcconell@gmail.com Subscribe to Inside exercise: Spotify: shorturl.at/tyGHL Apple Podcasts: shorturl.at/oFQRU YouTube: https://www.youtube.com/@insideexercise Anchor: https://anchor.fm/insideexercise Google Podcasts: shorturl.at/bfhHI Anchor: https://anchor.fm/insideexercise Podcast Addict: https://podcastaddict.com/podcast/4025218 Not medical advice
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