View source for G-force

===Horizontal===
The human body is better at surviving g-forces that are perpendicular to the spine. In general when the acceleration is forwards (subject essentially lying on their back, colloquially known as "eyeballs in"),<ref>{{cite web |url=http://roland.lerc.nasa.gov/~dglover/dictionary//tables/table11.html |archive-url=https://web.archive.org/web/20080520061140/http://roland.lerc.nasa.gov/~dglover/dictionary//tables/table11.html |archive-date=20 May 2008 |title=NASA Physiological Acceleration Systems |date=20 May 2008 |url-status=dead |access-date=25 December 2012 }}</ref> a much higher tolerance is shown than when the acceleration is backwards (lying on their front, "eyeballs out") since blood vessels in the retina appear more sensitive in the latter direction.{{Citation needed|date=February 2013}}

Early experiments showed that untrained humans were able to tolerate a range of accelerations depending on the time of exposure. This ranged from as much as {{val|20|u=g0}} for less than 10 seconds, to {{val|10|u=g0}} for 1 minute, and {{val|6|u=g0}} for 10 minutes for both eyeballs in and out.<ref>[https://ntrs.nasa.gov/api/citations/19980223621/downloads/19980223621.pdf NASA Technical note D-337, Centrifuge Study of Pilot Tolerance to Acceleration and the Effects of Acceleration on Pilot Performance] {{Webarchive|url=https://web.archive.org/web/20220217014537/https://ntrs.nasa.gov/api/citations/19980223621/downloads/19980223621.pdf |date=17 February 2022 }}, by Brent Y. Creer, Captain Harald A. Smedal, USN (MC), and Rodney C. Wingrove, figure 10</ref> These forces were endured with cognitive facilities intact, as subjects were able to perform simple physical and communication tasks. The tests were determined not to cause long- or short-term harm although tolerance was quite subjective, with only the most motivated non-pilots capable of completing tests.<ref>[https://ntrs.nasa.gov/api/citations/19980223621/downloads/19980223621.pdf NASA Technical note D-337, Centrifuge Study of Pilot Tolerance to Acceleration and the Effects of Acceleration on Pilot Performance] {{Webarchive|url=https://web.archive.org/web/20220217014537/https://ntrs.nasa.gov/api/citations/19980223621/downloads/19980223621.pdf |date=17 February 2022 }}, by Brent Y. Creer, Captain Harald A. Smedal, USN (MC), and Rodney C. Vtlfngrove</ref> The record for peak experimental horizontal g-force tolerance is held by acceleration pioneer [[John Stapp]], in a series of rocket sled deceleration experiments culminating in a late 1954 test in which he was clocked in a little over a second from a land speed of Mach 0.9. He survived a peak "eyeballs-out" acceleration of 46.2 times the acceleration of gravity, and more than {{val|25|u=g0}} for 1.1 seconds, proving that the human body is capable of this. Stapp lived another 45 years to age 89<ref>[http://www.ejectionsite.com/stapp.htm Fastest Man on Earth – John Paul Stapp] {{Webarchive|url=https://web.archive.org/web/20171215201020/http://www.ejectionsite.com/stapp.htm |date=15 December 2017 }}. Ejection Site. Retrieved on 14 October 2011.</ref> without any ill effects.<ref>{{cite web |last1=Martin |first1=Douglas |title=John Paul Stapp, 89, Is Dead; 'The Fastest Man on Earth' |url=https://www.nytimes.com/1999/11/16/us/john-paul-stapp-89-is-dead-the-fastest-man-on-earth.html |website=The New York Times |access-date=29 October 2016 |date=16 November 1999 |archive-date=3 September 2023 |archive-url=https://web.archive.org/web/20230903155450/https://www.nytimes.com/1999/11/16/us/john-paul-stapp-89-is-dead-the-fastest-man-on-earth.html |url-status=live }}</ref>

The highest recorded g-force experienced by a human who survived was during the [[2003 IndyCar Series]] finale at Texas Motor Speedway on 12 October 2003, in the 2003 Chevy 500 when the car driven by [[Kenny Bräck]] made wheel-to-wheel contact with [[Tomas Scheckter]]'s car. This immediately resulted in Bräck's car impacting the catch fence that would record a peak of {{val|214|u=g0}}.<ref>{{cite web |url=http://www.news.com.au/sport/motorsport/formula-one/jules-bianchi-survived-92g-impact-in-horror-formula-one-crash/news-story/c381589f42393105511f8413c3b2fd52 |title=New details from horror crash |website=News.com.au |access-date=30 December 2017 |date=16 October 2014 |archive-date=1 December 2017 |archive-url=https://web.archive.org/web/20171201032013/http://www.news.com.au/sport/motorsport/formula-one/jules-bianchi-survived-92g-impact-in-horror-formula-one-crash/news-story/c381589f42393105511f8413c3b2fd52 |url-status=live }}</ref><ref>{{cite web |url=http://www.crash.net/indycar/news/20962/1/qa-kenny-brack.html |title=Q&A: Kenny Brack |date=13 October 2004 |website=Crash.net |access-date=30 December 2017 }}</ref>