Estimation of body fat percentage in jockeys: implications for a weight category sport

The assessment of body composition in horse racing, a unique weight-restricted sport, provides an important health and performance indicator. The accuracy of skinfold prediction equations at estimating % body fat (% BF) was compared with dual-energy X-ray absorptiometry (DXA) data in a group of professional Irish jockeys (age 27.5 ± 7.7 years). Body composition was assessed in seventy-two male professional jockeys (flat n=35 and national hunt n=37) using standardised guidelines for skinfold thickness at 8 sites and DXA body fat assessment. Hydration status was assessed using urine specific gravity (Usg) to determine if participants were euhydrated and male specific prediction equations (Durnin and Womersley, Evans, Lohman, Reilly, Withers and Zemski) were selected to estimate % BF. Jockey-group specific equations were developed using the collected dataset. The selected equations underestimated % BF with variability between equations ranging from 7% to 10% compared to the DXA % BF of 15%. Flat jockeys were significantly lighter and shorter (p < 0.05) compared to national hunt jockeys resulting in the need for individual jockey-specific equations. The Flat and National Hunt Jockey specific equations demonstrated overall agreement accounting for 84% and 83% variance, respectively. Caution must be taken when using existing prediction equations due to the variability of % BF relative to DXA. Jockey-specific equations offer an alternative method for interpreting estimated body fat %.