Brian Shaw Uses Hydrostatic Submersion Testing to Learn His Bodyfat Percentage

Four-time World’s Strongest Man (WSM) champion Brian Shaw revealed that he is undergoing a six-week physique transformation. Shaw underwent hydrostatic testing to accurately assess his body fat percentage and documented it in a video published on his YouTube channel on Feb. 1, 2024.

Hydrostatic submersion testing, also known as underwater weighing, measures body density to estimate body composition. Per the Journal of American Dietetic Association, “Hydrostatic weighing…provides an accurate, acceptable, and convenient alternative method for body composition assessment.” (1)

Unlike DEXA scans, which can vary in accuracy based on an individual’s leanness, hydrostatic testing offers a more reliable benchmark for body fat measurement, regardless of one’s fitness levels and body composition. Check out how Shaw did it below:

Before his hydrostatic test, Shaw had to remove three buckets of water from the tank to accommodate his body volume without causing spillage or inaccuracies in the test results. Shaw stands 6’8″ tall and weighs approximately 400 pounds.

This adjustment ensured that the water displaced by Shaw’s body would accurately measure his body density, which is crucial for calculating body fat percentage. Shaw was instructed to submerge himself completely underwater and exhale as much air out of his lungs as possible to sink below the water’s surface. 

The hydrostatic test requires an individual to start blowing out air while their head is still above water and continue exhaling until they are fully submerged and have completely emptied their lungs.

The hydrostatic testing method is built upon Archimedes’ principle of buoyancy, which “states that when a body is partially or totally immersed in a fluid, it is buoyed up by a force equal to the weight (volume) of the fluid that is displaced by the body. (i.e., as the body is submerged, it displaces water, which in turn produces the buoyancy force.” (2)

Shaw underwent four submersions to obtain precise body fat percentage readings. The initial measurement revealed 19.4 percent. The second scored 18.3 percent. The third resulted at 17.8 percent. The final submersion showed 17.6 percent.

Shaw expressed satisfaction with the results, having hoped to be sub-20 percent body fat before the test. As Shaw embarks on his six-week transformation challenge, the results of this hydrostatic test serve as a baseline to measure his progress. Shaw will undergo another hydrostatic test at the end of six weeks to assess his improvements. 

Shaw is scheduled to make his mixed martial arts (MMA) debut on Feb. 17, 2024, at Lusail Stadium in Qatar. The reigning WSM champ Mitchell Hooper and 2017 WSM winner Eddie Hall are also on the card, set to fight each other.


Heath, E. M., Adams, T. D., Daines, M. M., & Hunt, S. C. (1998). Bioelectric impedance and hydrostatic weighing with and without head submersion in persons who are morbidly obese. Journal of the American Dietetic Association98(8), 869–875.

Torres-Ronda L, Del Alcázar XS. The Properties of Water and their Applications for Training. J Hum Kinet. 2014 Dec 30;44:237-48. doi: 10.2478/hukin-2014-0129. PMID: 25713684; PMCID: PMC4327375.

Featured image: @shawstrength on Instagram

The post Brian Shaw Uses Hydrostatic Submersion Testing to Learn His Bodyfat Percentage appeared first on BarBend.


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