To assess the body composition of recreational cold-water swimmers, to determine if cold-water
swimmers have an increased % body fat when compared to average Americans, and to examine the relationships between
body composition and total swim distance and time in the water per swim.
Following 3 months of swimming regularly in cold water in the San Francisco Bay (water temperature range:
9.6° C [49.3° F] to 12.6° C [54.7° F]) during the winter months, body mass index (BMI), % body fat (assessed by
circumference technique), and surface/volume ratio were measured in 88 subjects (70 men and 18 women). The total
cumulative swim distance was recorded by each subject and each subject estimated his or her average time in the water
For all subjects, averages were as follows: total swim distance in 3-month period (miles[km]): 50.3 [81.0] ± 17.6
[28.3] (range 40 [64.4] – 154 [247.8]), average estimated time in the water per swim (minutes): 32.5 ± 7.9 (range 17 -60),
age (years): 52.3 ± 10.1 (range: 24-76), BMI (kg/ m2): 25.8 ± 3.4 (range:19.0-37.1), % body fat: 22.6 ± 6.7 (range: 6.9-
42.4), surface/volume ratio(m2/L): .0259 ± .0023 (range: .0200-.0311). Compared to corresponding American 50th
percentile values, the % fat of men was modestly lower (Median of the difference =-1.6%; P=0.007); the % fat of women
was modestly higher, but not statistically different (Median of the difference =1.7%; P<0.1). There was a marginal nonlinear
correlation between % fat and average estimated time in the water per swim (Coef.=0.007; P=0.048). No body
composition variable correlated with total swim distance (P>0.1 for all variables).
Our results suggest that recreational cold-water swimmers do not have an increased % body fat when
compared to average Americans, and individuals with a wide variety of body types are able to swim recreationally in cold
water. The marginal correlation between % fat and average estimated time in the water suggests that leaner swimmers
voluntarily limit time in cold water.