Weighing In: Exploring Body Composition Trends in Professional Jockeys. Written by Jemima Turley.
My background:
From a young age, I have always been passionate about sports. That passion stayed with me throughout school, and when the time came to choose a college course, a friend suggested I look into Health and Performance Science at University College Dublin (UCD). I had never heard of it, but it turned out to be the perfect fit: a course focused on improving athletic performance through sport and exercise science. During my time at UCD, I completed a semester abroad at Purdue University in Indiana, where I got to further my studies in a completely new environment, complete my personal training certification, and develop a greater interest in nutrition and strength and conditioning.
As the final year of my undergraduate studies approached, I knew I wanted to continue my studies and specialise further within the field of sports and exercise, particularly in nutrition. That led me to Maastricht University, where I began an MSc. in Human Movement Sciences with a specialisation in Sports and Nutrition. I found the adaptation to the new academic style quite challenging, as there was a big emphasis on problem-based learning and critical thinking, but it pushed me to challenge myself personally and academically.
As part of the Master’s, I began a 24-week research internship in February under the supervision of Dr. Sarahjane Cullen at Dublin City University (DCU). During this time, I conducted a systematic review titled “Body Composition Changes in Professional Jockeys Over Time: A Systematic Review”, where I was fortunate to present my findings at the inaugural Irish Sport and Exercise Science (ISESA) conference. I was awarded the best oral presentation among the 40 MSc., MRes., and Ph.D. students who showcased their research.
Currently, I am working on my thesis to complete my MSc., which focuses on the relationship between jockey body composition and weight-making practices. In the coming weeks, I will be starting an internship with the PESS programme at the University of Limerick, working on a project which will explore supplementation use in jockeys.
Research Project:
My research project, titled “Body Composition Changes in Professional Jockeys Over Time: A Systematic Review”, focused on how jockeys' body composition has changed over the years. Horse racing is split into two different categories in which jockeys compete: flat and National Hunt racing (NH). Both categories require their jockeys to “make weight” before each competition. As the weight classes for each category differ, the analysis focused on both jockey groups separately. To “make weight”, jockeys often resort to various harmful methods of rapid weight loss (RWL) such as saunas, excessive exercise, hot baths, and fluid restriction. Jockey’s body composition is taken regularly, using both Dual-energy X-ray Absorptiometry (DXA) and skinfold thickness using calibrated skinfold callipers.
Over the years, medical practitioners had noticed increases in jockeys' body fat percentage (BF%) from DXA scans; however, it remained unclear what was exactly happening. If BF% was increasing, that could make reaching the weight limits more challenging, eventually leading to an increased use of RWL methods.
Therefore, the aim was to evaluate jockeys' body composition over time using both DXA and skinfold thickness to determine if changes were occurring.
The systematic review was guided by the PRISMA 2020 guidelines and the Cochrane Handbook. A search string was developed based on the inclusion and exclusion criteria. These included: Professional jockeys, year range relevant to changes in body composition, and studies reporting various body composition outcomes. Papers that did not separate flat and NH jockeys, or reported them as a single jockey group, were excluded.
The main databases used were PubMed and Web of Science. The PRISMA 2009 flow diagram was used to visualise the screening process:
168 records were identified
142 were excluded during screening
26 full-text articles were assessed
13 met the inclusion criteria and were analysed
The Newcastle Ottawa Scale, adapted for cross-sectional studies, was used to assess risk of bias in the 13 included studies.
Key body composition trends were visualised through line charts and summary tables, tracking changes in BF%, fat mass (FM), lean mass (LM), and skinfold thickness across the years. The numbers recorded below represent the change from the first recorded body composition variable in the included literature to the most recent.
For flat racing jockeys:
BF% increased from 9% to 15% from 2009 to 2021
FM increased from 4.4 kg to 8 kg from 2012 to 2021
LM showed inconsistent trends, initially decreasing from 49.4 kg in 2012 to 42.5 kg in 2017, but later rebounding back up to 45.7 kg in 2021
The sum of 7 skinfolds showed minimal changes over time, with a slight decrease from 44.3 mm to 42.4 mm from 2009 to 2018.
For NH jockeys:
BF% increased from 10.4% to 15.3% from 2009 to 2021.
FM increased, though less dramatically than in flat racing, from 8.7 kg to 9.6 kg from 2012 to 2021.
LM trends were again inconsistent, initially declining from 53.7 kg to 50.7kg from 2012 to 2017, but later increasing to 53.4 kg in 2021.
There were insufficient data to determine the change in the sum of 7 or 8 skinfolds.
Take-Homes and Applications:
These findings reveal a consistent upward trend in BF% and FM among both flat and NH jockeys. In flat racing, BF% measured by DXA has steadily increased, while the sum of 7 skinfolds has remained relatively unchanged. This raises an important question: If subcutaneous fat is not increasing, what is? A possible explanation is a rise in visceral fat, which would appear on a DXA scan but would not be detected using skinfold measurements. This is particularly concerning as increases in visceral fat are linked to various health risks such as cardiovascular disease and type II diabetes. While this is a possibility, the differences between DXA and skinfold results may reflect limitations in the measurement techniques or other contributing factors. For now, the reasoning behind this discrepancy remains unclear.
Despite the limited data and small sample sizes, the findings may have significant implications for medical practitioners and sports nutritionists working with jockeys. Now that we know a change is occurring, the next step is to explore the underlying causes of increased BF% and FM through future research.
Author Bio
Jemima Turley
I am currently completing a research internship at Dublin City University as part of my Master’s in Human Movement Sciences with a specialisation in Sports and Nutrition at Maastricht University. I graduated from University College Dublin last September with a degree in Health and Performance Science. Alongside my studies, I work part-time as a CrossFit coach and personal trainer, and I am set to complete my ISAK Level 1 Body Composition Accreditation this month. I am passionate about both nutrition and exercise and aim to continue developing my career in the sports and exercise science field.
Undergraduate degree in Health and Performance Science at University College Dublin
Email: jemimat2003@gmail.com