Your inner ear has two main functions: hearing and balance. The balance part, also known as the vestibular system, relies in part on a bunch of rock-like crystals called otoliths, which is Greek for \u201cear stones.\u201d When your head moves, gravity makes these crystals move around; their motion is detected by small hairs that then signal to your brain which direction and how quickly your head is moving.<\/p>\n
This motion-sensing system is important to help you avoid fainting whenever you stand up. As you change your body position, gravity will cause your blood to redistribute itself within your body, tending to pool in your legs when you\u2019re vertical. That can leave insufficient blood\u2014and oxygen\u2014to fuel your brain, which is what makes you feel lightheaded. To prevent that, the body responds by constricting blood vessels and pumping your heart harder and faster. This response is triggered in part (though not exclusively) by signals from the otoliths.<\/p>\n
Ray and his colleagues put their volunteers through a fairly rigorous training program that ramped up to two long runs or rides of 60 minutes and two interval sessions each week. The program worked: the runners increased their VO2 max<\/a>, a measure of aerobic fitness, by an impressive 25 percent, and the cyclists increased by 20 percent. Average resting heart rate dropped from 61 to 53 beats per minute in the runners, and from 65 to 55 in the cyclists. In the control group, by contrast, none of the fitness parameters changed.<\/p>\n To measure the sensitivity of the otoliths, the researchers put their subjects through a procedure called \u201chead-down rotation,\u201d which basically involves lying on your stomach with your head dangling off the end of a table while the scientist moves your head around to shake the otoliths up. Then they used electrodes to measure the nerve signals traveling from the brain to the calf muscles: the idea is that these signals would tell the blood vessels in the calves to constrict if you were about to stand up. Sure enough, the signals decreased dramatically after eight weeks of running, but didn\u2019t change after eight weeks of cycling or not exercising.<\/p>\n Here\u2019s what that data looked like, where \u201cMSNA\u201d (muscle sympathetic nerve activity) is how much nerve signaling there was during the head-down rotation:<\/p>\n They also estimated blood flow in the calf muscles by measuring how much the calves swelled, and found a similar pattern: triggering the otoliths with head-down rotation caused a reduction in blood flow to the calves by constricting blood vessels, but this response was suppressed after eight weeks of running.<\/p>\n The conclusion of the study is that it\u2019s not fitness alone that alters your response to standing suddenly. Instead, there\u2019s something specific to running\u2019s up-and-down motion that seems to make your brain pay less attention to motion signals from your otoliths. This doesn\u2019t mean it\u2019s the only reason for headrushes, but it suggests that it\u2019s one of them. It\u2019s worth noting that the cyclists in this study were on stationary bikes, so it\u2019s possible that real-world cycling might have a little more side-to-side motion that might have a similar effect\u2014though you\u2019d still expect it to be much less than from running.<\/p>\n As an aside, another situation where runners sometimes feel lightheaded and collapse is at the end of long races. This is also a situation where the heart is having trouble getting enough oxygen to the brain, and it used to be blamed on dehydration. But it generally seems to happen right after people stop running, which suggests<\/a> that it\u2019s actually a problem of blood distribution. When you\u2019re running, your blood vessels are dilated, and the squeezing of your calf muscles with each step pushes blood from your legs back to your heart. When you stop running, your blood vessels are still wide open but this calf-muscle pump suddenly stops, so blood pools in your legs and you feel faint. The takeaway: keep moving after you cross the finish line.<\/p>\n As for the takeaway from the otolith study, it\u2019s neat to understand what\u2019s happening, and it\u2019s somewhat reassuring to know that it doesn\u2019t mean there\u2019s something wrong with my heart or blood-pressure regulation. Is it a problem to have less sensitive otoliths? I\u2019m not sure. I couldn\u2019t find any evidence that runners have worse balance in general than other athletes or the general population. It would be interesting to see data on that. I\u2019m also curious about whether there\u2019s any link between how smooth your running stride is and how sensitive your otoliths are. If so, that might be the nudge I need to finally try to smooth out my notoriously (some would say comically) bouncy running stride. For now, I\u2019ll just take my time getting off the couch.<\/p>\n For more Sweat Science, sign up for the email newsletter<\/a> and check out my new book The Explorer\u2019s Gene: Why We Seek Big Challenges, New Flavors, and the Blank Spots on the Map<\/a>.<\/p>\n","protected":false},"excerpt":{"rendered":"Published December 15, 2025 09:13AM \u201cWhoa, headrush!\u201d Over the years, I\u2019ve gotten very familiar with that sensation: a…\n","protected":false},"author":2,"featured_media":351632,"comment_status":"","ping_status":"","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[34],"tags":[76663,97,80377,132298,80379,155637,70096],"class_list":{"0":"post-351631","1":"post","2":"type-post","3":"status-publish","4":"format-standard","5":"has-post-thumbnail","7":"category-health","8":"tag-editor-awise","9":"tag-health","10":"tag-parent_category-health","11":"tag-tag-endurance-training","12":"tag-tag-evergreen","13":"tag-tag-sweat-science","14":"tag-type-article"},"_links":{"self":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts\/351631","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/comments?post=351631"}],"version-history":[{"count":0,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/posts\/351631\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/media\/351632"}],"wp:attachment":[{"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/media?parent=351631"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/categories?post=351631"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.newsbeep.com\/us\/wp-json\/wp\/v2\/tags?post=351631"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}![\"Running](\"https:\/\/www.newsbeep.com\/us\/wp-content\/uploads\/2025\/12\/graph.jpg\"\/)
Running but not cycling lowers the response of your inner-ear balance organs. (Photo: Courtesy \u2018Journal of Applied Physiology\u2019)<\/p>\n