Male Flat Jockeys Do Not Display Deteriorations in Bone Density or Resting Metabolic Rate in Accordance With Race Riding Experience: Implications for RED-S

Abstract

Despite consistent reports of poor bone health in male jockeys, it is not yet known if this is a consequence of low energy availability or lack of an osteogenic stimulus. Given the rationale that low energy availability is a contributing factor in low bone health, we tested the hypothesis that both hip and lumbar bone mineral density (BMD) should progressively worsen in accordance with the years of riding. In a cross-sectional design, male apprentice (n=17) and senior (n=14) jockeys (matched for body mass and fat free mass) were assessed for hip and lumbar spine BMD as well as both measured and predicted resting metabolic rate (RMR). Despite differences (P<0.05) in years of race riding (3.4 ± 2 v 16.3 ± 6.8), no differences were apparent (P>0.05) in hip (-0.9 ± 1.1 v -0.8 ± 0.7) and lumbar Z-scores (-1.3 ± 1.4 v -1.5 ± 1) or measured RMR (1459 ± 160 v 1500 ± 165 kcal.d-1) between apprentices and senior jockeys, respectively. Additionally, years of race riding did not demonstrate any significant correlations (P>0.05) with either hip or lumbar spine BMD. Measured RMR was also not different (P>0.05) from predicted RMR in either apprentice (1520 ± 44 kcal.d-1) or senior jockeys (1505 ± 70 kcal.d-1). When considered with previously published data examining under-reporting of energy intake and direct assessments of energy expenditure, we suggest that low BMD in jockeys is not due to low energy availability per se, but rather, the lack of an osteogenic stimulus associated with riding.

Full text

“Male Flat Jockeys Do Not Display Deteriorations in Bone Density or Resting Metabolic Rate in Accordance With Race
Riding Experience: Implications for RED-S” by Wilson G, Martin D, Morton JP, Close GL
International Journal of Sport Nutrition and Exercise Metabolism
© 2018 Human Kinetics, Inc.
Note: This article will be published in a forthcoming issue of
the International Journal of Sport Nutrition and Exercise
Metabolism. This article appears here in its accepted, peer-
reviewed form; it has not been copyedited, proofed, or
formatted by the publisher.
Section: Original Research
Article Title: Male Flat Jockeys Do Not Display Deteriorations in Bone Density or Resting
Metabolic Rate in Accordance With Race Riding Experience: Implications for RED-S
Authors: George Wilson, Dan Martin, James P. Morton and Graeme L. Close
Affiliations: Research Institute for Sport and Exercise Sciences, Liverpool John Moores
University, Liverpool, United Kingdom.
Running Head: Jockeys, BMD and RED-S
Journal: International Journal of Sport Nutrition and Exercise
Acceptance Date: January 19, 2018
©2018 Human Kinetics, Inc.
DOI: https://doi.org/10.1123/ijsnem.2017-0371

“Male Flat Jockeys Do Not Display Deteriorations in Bone Density or Resting Metabolic Rate in Accordance With Race
Riding Experience: Implications for RED-S” by Wilson G, Martin D, Morton JP, Close GL
International Journal of Sport Nutrition and Exercise Metabolism
© 2018 Human Kinetics, Inc.
Male flat jockeys do not display deteriorations in bone density or resting metabolic rate
in accordance with race riding experience: implications for RED-S
George Wilson1, Dan Martin1, James P Morton1 and Graeme L Close1
1Research Institute for Sport and Exercise Sciences
Liverpool John Moores University
Liverpool, UK
L3 3AF
Address for correspondence:
Professor Graeme L. Close
Research Institute for Sport and Exercise Sciences
Liverpool John Moores University
Liverpool, UK
L3 3AF
g.l.close@ljmu.ac.uk
0151 904 6266
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“Male Flat Jockeys Do Not Display Deteriorations in Bone Density or Resting Metabolic Rate in Accordance With Race
Riding Experience: Implications for RED-S” by Wilson G, Martin D, Morton JP, Close GL
International Journal of Sport Nutrition and Exercise Metabolism
© 2018 Human Kinetics, Inc.
Abstract
Despite consistent reports of poor bone health in male jockeys, it is not yet known if this is a
consequence of low energy availability or lack of an osteogenic stimulus. Given the rationale
that low energy availability is a contributing factor in low bone health, we tested the hypothesis
that both hip and lumbar bone mineral density (BMD) should progressively worsen in
accordance with the years of riding. In a cross-sectional design, male apprentice (n=17) and
senior (n=14) jockeys (matched for body mass and fat free mass) were assessed for hip and
lumbar spine BMD as well as both measured and predicted resting metabolic rate (RMR).
Despite differences (P<0.05) in years of race riding (3.4 ± 2 v 16.3 ± 6.8), no differences were
apparent (P>0.05) in hip (-0.9 ± 1.1 v -0.8 ± 0.7) and lumbar Z-scores (-1.3 ± 1.4 v -1.5 ± 1) or
measured RMR (1459 ± 160 v 1500 ± 165 kcal.d-1) between apprentices and senior jockeys,
respectively. Additionally, years of race riding did not demonstrate any significant correlations
(P>0.05) with either hip or lumbar spine BMD. Measured RMR was also not different (P>0.05)
from predicted RMR in either apprentice (1520 ± 44 kcal.d-1) or senior jockeys (1505 ± 70
kcal.d-1). When considered with previously published data examining under-reporting of
energy intake and direct assessments of energy expenditure, we suggest that low BMD in
jockeys is not due to low energy availability per se, but rather, the lack of an osteogenic
stimulus associated with riding.
Keywords: energy availability, metabolic rate, jockeys
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“Male Flat Jockeys Do Not Display Deteriorations in Bone Density or Resting Metabolic Rate in Accordance With Race
Riding Experience: Implications for RED-S” by Wilson G, Martin D, Morton JP, Close GL
International Journal of Sport Nutrition and Exercise Metabolism
© 2018 Human Kinetics, Inc.
Introduction
The relative energy deficiency in sport syndrome (RED-S) was recently developed in
recognition that male athletes display evidence of impaired physiological function that may be
related to low energy availability (Mountjoy et al., 2014). Jockeys are unique amongst
professional athletes in that they have to make weight daily and to do so they commonly
undertake periods of food deprivation (Wilson, Drust, Morton, & Close, 2014). In this regard,
we (Wilson et al., 2013a; Wilson, Hill, Sale, Morton, & Close, 2015a; Wilson et al., 2015b)
and others (Dolan et al., 2012; Greene, Naughton, Jander, & Cullen, 2013; Jackson et al., 2017;
Leydon & Wall, 2002; Poon, O'Reilly, Sheridan, Cai, & Wong, 2017; Waldron-Lynch et al.,
2010; Warrington et al., 2009) have consistently reported that male flat jockeys present with
low bone mineral density (BMD), with Z-scores often lower than -1. Such low bone densities
are often considered to be due to a combination of nutritional factors including low energy
availability and sub-optimal micronutrient intake (Dolan et al., 2011; Greene et al., 2013;
Martin, Wilson, Morton, Close, & Murphy, 2017; Wilson et al., 2014; Wilson et al., 2013b) as
well as a potential loss of calcium (Barry et al., 2011) due to the forced daily sweating that is
often utilised as a technique to achieve daily riding weight (Warrington et al., 2009; Wilson et
al., 2014). As such, low BMD is a continual cause of concern for jockey athlete-welfare
considering the increased risk of fracture in the event of a fall (Dolan et al., 2012; Jackson et
al., 2017; Wilson et al., 2012; Wilson et al., 2015b).
Despite the well-documented reports of low BMD, it remains questionable if jockeys
are athletes who truly exhibit symptoms of RED-S. Indeed, measured RMR does not differ
from predicted RMR (Cunningham & Johns, 1980) either before (Wilson et al., 2015a; Wilson
et al., 2015b) or after dietary interventions (Wilson et al., 2015b). Furthermore, when
considering the potential impact of low energy availability on endocrine function, it is
noteworthy that male flat jockeys display testosterone, insulin-like growth factor 1 and sex
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“Male Flat Jockeys Do Not Display Deteriorations in Bone Density or Resting Metabolic Rate in Accordance With Race
Riding Experience: Implications for RED-S” by Wilson G, Martin D, Morton JP, Close GL
International Journal of Sport Nutrition and Exercise Metabolism
© 2018 Human Kinetics, Inc.
hormone binding globulin values all within normal ranges (Wilson et al., 2015b). Previous
reports of low energy availability have also been largely ascertained from analysis of self-
reported food diaries (Dolan et al., 2011; Leydon & Wall, 2002; Wilson et al., 2013b; Wilson,
Sparks, Drust, Morton, & Close, 2013c), a method often critiqued for their reliability
(Braakhuis, Meredith, Cox, Hopkins, & Burke, 2003; Dhurandhar et al., 2015) and under-
reporting (Poslusna, Ruprich, de Vries, Jakubikova, & van't Veer, 2009). Moreover, energy
intakes of jockeys are significantly higher when food intake has been monitored via a wearable
camera as opposed to the traditional food diary approach (O'Loughlin et al., 2013). Further
evidence for likely under-reporting of energy intake is also provided by our recent assessment
of energy expenditure (via doubly labelled water) of male flat jockeys. Indeed, although self-
reporting of energy intake was estimated at approximately 1500 kcal.d-1, energy expenditure
was calculated as 2500 kcals.d-1 but yet body mass did not significantly change during a four
month data collection period (Wilson et al., 2017).
When taken together, it is therefore difficult to ascertain if the low BMD consistently
observed in jockeys is in fact due to low energy availability and/or the lack of a consistent
osteogenic stimulus arising from years of non-weight bearing activity due to riding. Regardless
of the precise contribution of each of the aforementioned factors, it could therefore be
hypothesised that symptoms of RED-S should progressively worsen in accordance with the
years of race riding. With this in mind, the aim of the present study was to assess both measured
and predicted RMR as well as hip and lumbar spine BMD in a cohort of apprentice and senior
professional male flat jockeys.
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“Male Flat Jockeys Do Not Display Deteriorations in Bone Density or Resting Metabolic Rate in Accordance With Race
Riding Experience: Implications for RED-S” by Wilson G, Martin D, Morton JP, Close GL
International Journal of Sport Nutrition and Exercise Metabolism
© 2018 Human Kinetics, Inc.
Methods
Subjects
Thirty-one male professional flat jockeys currently race riding in Great Britain (GB)
provided informed written consent to participate in this study. Apprentice jockeys (n=17) were
classified as those jockeys who were race riding at the time of the study with a ‘claim-weight-
allowance’ of 3, 5 or 7 lb. This ‘claim’ is a reduction of weight from the allocated competition
race weight for newly licensed professional riders who had not ridden a specified number of
race winners, in order to incentivise racehorse trainers with a more favourable racing weight
(lower), thus providing more chances for these riders. The senior jockey group (n=14) consisted
of those jockeys who had reached a specified total of winners negating their ‘claim’. This group
did include a 21-year-old jockey who had been successful in a comparably short race riding
career and had therefore reached the senior categorisation in a relatively short time span. At
the time of the study, none of the jockeys were taking any prescribed medication or nutritional
supplements though three jockeys (all senior jockeys) were smokers. The study received ethical
approval from the National Research Ethics Service. A comparison of age, race riding
experience and anthropometrical characteristics are shown in Table 1.
Design
In a cross-sectional design, both apprentice and senior jockeys (matched for body mass,
fat mass and fat free mass) were assessed for both resting metabolic rate (RMR) and hip and
lumbar spine BMD.
Experimental Procedures
After arriving in the laboratory in an overnight fasted state, jockeys were assessed for
hydration status, BMD and RMR. Hydration status was assessed from a mid-flow urine sample
by measuring urine osmolality (UO) using a handheld refractometer (Atago, USA). Jockeys
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“Male Flat Jockeys Do Not Display Deteriorations in Bone Density or Resting Metabolic Rate in Accordance With Race
Riding Experience: Implications for RED-S” by Wilson G, Martin D, Morton JP, Close GL
International Journal of Sport Nutrition and Exercise Metabolism
© 2018 Human Kinetics, Inc.
were then measured for height and weight (Seca, Germany) wearing shorts and underwent a
measure of whole body composition, hip bone density and lumbar spine bone density using
dual-energy X-ray absorptiometery (DXA) scan (Hologic, USA) for classification of Z-scores,
matched for age, sex and ethnicity. Jockeys were firstly asked to lie in a supine position and
had their left foot affixed with Velcro to a Perspex triangular platform to invert the head of the
left femur for measurement of hip bone density. Secondly, a box was placed under the popliteal
crease of both knees of each jockey at a ~90° for assessment of lumbar bone density. Finally,
an assessment of full body composition was undertaken in the supine position with inverted
feet secured with micropore surgical tape (Nexcare, UK) to allow for greater analysis of the
neck of the femur. All measurements were performed within 12 minutes. Jockeys were then
required to have resting metabolic rate (RMR) measured in a supine position using indirect
calorimetry (Metalyser, USA). Jockeys were required to lie down for an initial 15 minutes
before testing to allow for the dissipation of movement from the DXA analysis to the metabolic
unit. Data was then collected for a further 30 minutes and using the protocol as described
previously (Wilson et al., 2015a; Wilson et al., 2015b).
Statistical analysis
All data was analysed using SPSS Statistics for Windows (version 22.0 IBM, USA).
Data was checked for normality and independent t-tests were used to compare data between
apprentice and senior jockeys as well as for comparing measured RMR versus predicted RMR
(Cunningham, 1980). Correlations between years of race riding and hip / lumbar spine BMD
were made using Pearson’s correlation coefficient to ascertain the linearity between the two
specific variables. All comparison data were reported as means (SD) and statistical significance
was set at P≤0.05 level, with R2 values reported for correlation coefficient scores.
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“Male Flat Jockeys Do Not Display Deteriorations in Bone Density or Resting Metabolic Rate in Accordance With Race
Riding Experience: Implications for RED-S” by Wilson G, Martin D, Morton JP, Close GL
International Journal of Sport Nutrition and Exercise Metabolism
© 2018 Human Kinetics, Inc.
Results
Overview of baseline characteristics
A comparison of age, racing experience and anthropometric characteristics between
apprentice and senior jockeys is shown in Table 1. Apprentice jockeys were significantly
younger and had less years of race riding experience than senior jockeys. Although apprentice
jockeys were significantly taller than senior jockeys, there were no significant differences in
body mass, fat mass (both absolute and percent) and fat free mass between populations.
Additionally, urine osmolality was not significantly different between apprentice and senior
jockeys.
Resting metabolic rate (RMR)
A comparison of RMR between apprentice and senior jockeys is shown in Figure 1.
There was no significant difference (P=0.48) in RMR between apprentice (1459 ± 161 kcal.d-
1) and senior jockeys (1501 ± 165 kcal.d-1) (see Figure 1A). In addition, measured RMR did
not significantly differ from predicted RMR in either apprentice (1459 ± 161 versus 1520 ± 44
kcal.d-1; P=0.18) or senior jockeys (1501 ± 165 versus 1505 ± 70 kcal.d-1; P=0.92) (see Figure
1B and C, respectively).
Hip and lumbar spine bone mineral density
There was no significant difference in either hip Z-score (-0.9 ± 1.1 versus -0.8 ± 0.7;
P=0.84) or lumbar spine Z-score (-1.3 ± 1.4 versus -1.5 ± 1.0; P=0.70) between apprentice and
senior jockeys, respectively (see Figure 2 A and B). Years of race riding did not display any
significant correlation with either hip (R2 = 0.01; P=0.72) or lumbar spine Z-score (R2 = 0.04;
P=0.29) (see Figure 2 C and D).
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“Male Flat Jockeys Do Not Display Deteriorations in Bone Density or Resting Metabolic Rate in Accordance With Race
Riding Experience: Implications for RED-S” by Wilson G, Martin D, Morton JP, Close GL
International Journal of Sport Nutrition and Exercise Metabolism
© 2018 Human Kinetics, Inc.
Discussion
Despite consistent reports of low BMD in male jockeys, it is not yet known if male
jockeys exhibit true symptoms of the relative energy deficiency in sport syndrome (RED-S).
Given the rationale that low energy availability is a contributing cause to low BMD, the aim of
the present study was to test the hypothesis that both hip and lumbar spine BMD should
progressively worsen in accordance with the years of riding. Importantly, we demonstrate no
differences in hip or lumbar spine Z-score between apprentice and senior jockeys and also
observed no associations between years of race riding and BMD. In addition, RMR was not
different between jockey cohorts whilst measured RMR was also not different from predicted
RMR in either apprentice or senior jockeys.
A well-documented negative consequence associated with RED-S is low BMD
(Mountjoy et al., 2014). Given that jockeys have to make weight daily, it has therefore been
suggested that jockeys are an athletic population especially sensitive to exhibit symptoms of
RED-S including impaired BMD (Wilson et al., 2014). Confirming previous data from our
group and others (Dolan et al., 2012; Greene et al., 2013; Leydon & Wall, 2002; Poon et al.,
2017; Waldron-Lynch et al., 2010; Warrington et al., 2009; Wilson et al., 2013b; Wilson et al.,
2015a; Wilson et al., 2015b), we also report that the BMD of the jockeys studied here was
significantly lower than clinical norms. Indeed, we report that 20 of the 31 jockeys
demonstrated low bone mass (Z-score <-1) (Barrack, Fredericson, Tenforde, & Nattiv, 2017)
in the lumbar region (10 apprentice and 10 senior) with 13 jockeys also presenting with low
bone mass at the hip (6 apprentice and 7 senior).
Nonetheless, despite the consistent reports of low BMD in jockeys, it is not yet certain
whether such data are true symptoms associated with RED-S. Indeed, we observed no
differences in hip or lumbar spine Z-scores between apprentice and senior jockeys as well as
reporting no positive association between years of race riding and BMD (see Figure 2). The
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“Male Flat Jockeys Do Not Display Deteriorations in Bone Density or Resting Metabolic Rate in Accordance With Race
Riding Experience: Implications for RED-S” by Wilson G, Martin D, Morton JP, Close GL
International Journal of Sport Nutrition and Exercise Metabolism
© 2018 Human Kinetics, Inc.
latter point is especially important considering that in some cases, senior jockeys presented
with 20-30 years of race riding experience. For example, when comparing jockeys who had
ridden for the longest periods (i.e. >20 years) with the least experienced jockeys (i.e. <1 year),
it is clear that such individuals display similarly low BMD at both the hip and lumbar spine. In
consideration of other symptoms of RED-S, we also observed no differences in RMR between
apprentices or senior jockeys as well as no differences in measured versus predicted RMR in
either cohort (see Figure 1). When such findings are considered with previous data highlighting
marked evidence of under-reporting of energy intake (O'Loughlin et al., 2013) as well as direct
assessments of energy expenditure (Wilson et al., 2017), it remains questionable if male
jockeys truly exhibit low energy availability. Indeed, despite the potential impact of low energy
availability on endocrine function, we also previously reported that male flat jockeys display
testosterone, insulin-like growth factor 1 and sex hormone binding globulin values all within a
clinically normal range (Wilson et al., 2015b). Given the cross-sectional nature of the study,
and the lack of a control group (given that there is no appropriate control group for jockeys)
we cannot exclude the possibility however that the jockeys experienced an initial reduction in
BMD during their adolescent years and this state has persisted without further significant
reductions. Future studies may now wish to assess BMD in adolescent jockeys prior to them
commencing significant amounts of horse riding.
When taken together, it is therefore possible that the low BMD reported in jockeys is,
in fact, predominantly due to the lack of an osteogenic stimulus associated with years of non-
weight bearing activity due to riding activities (Olmedillas, Gonzalez-Aguero, Moreno,
Casajus, & Vicente-Rodriguez, 2012), as opposed to low energy availability per se. Whilst we
acknowledge that the apprentice jockeys presented with considerably less race riding
experience than their senior counterparts, it is noteworthy that apprentice jockeys are likely to
be from horse-racing families and hence, may have spent much of their adolescence engaged
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“Male Flat Jockeys Do Not Display Deteriorations in Bone Density or Resting Metabolic Rate in Accordance With Race
Riding Experience: Implications for RED-S” by Wilson G, Martin D, Morton JP, Close GL
International Journal of Sport Nutrition and Exercise Metabolism
© 2018 Human Kinetics, Inc.
in riding activities (Greene et al., 2013) and potentially inadequate intake of key micronutrients
important in bone development such as vitamin D and calcium (Wilson et al., 2013b). Such
loading patterns are particularly important given that peak bone mass occurs at the end of the
second decade of life (Baxter-Jones, Faulkner, Forwood, Mirwald, & Bailey, 2011). Further
studies are now required to accurately quantify the physical loading patterns, energy
availability and progression of bone mass of prospective senior jockeys throughout their
childhood and adolescence and assess if any of these variables correlate with poor bone health.
Support for a lack of an osteogenic stimulus is also provided by the observation that one of the
apprentice jockeys studied here presented with a hip and lumbar Z-score of 2.2 and 1.8,
respectively (see Figure 2). Indeed, this athlete was a former amateur boxer of international
status and hence had a training history of high load bearing activity such as daily running,
circuit based and resistance-based training. Interestingly, despite potential low energy
availability in boxers (Morton, Robertson, Sutton, & MacLaren, 2010) it is noteworthy that
amateur boxers exhibit greater bone mineral density in hip and lumbar regions (in a hierarchical
manner) when compared with age-matched recreationally active individuals and a cohort of
professional jockeys, respectively (Dolan et al., 2012). It is therefore possible that the negative
effects of transient periods of weight cycling (i.e. multiple training camps per year) on markers
of bone turnover in combat athletes (Prouteau, Pelle, Collomp, Benhamou, & Courteix, 2006)
may be offset by the high osteogenic stimulus of habitual training activities (e.g. both amateur
and professional boxers may run 5-10 km on 5-6 days per week) as well as the return to normal
body mass within 7-10 days post-contest. Furthermore, in a review of studies looking at the
influences of participation in ball sports on bone health development in young athletes,
Teneforde and colleagues concluded that activities within these sports, primarily jumping and
multi-directional movements, may serve as a pre-habilitation strategy for future stress fractures,
including for running and swimming sports, which generally are devoid of such activities
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“Male Flat Jockeys Do Not Display Deteriorations in Bone Density or Resting Metabolic Rate in Accordance With Race
Riding Experience: Implications for RED-S” by Wilson G, Martin D, Morton JP, Close GL
International Journal of Sport Nutrition and Exercise Metabolism
© 2018 Human Kinetics, Inc.
(Tenforde, Sainani, Carter Sayres, Milgrom, & Fredericson, 2015). From a clinical application
perspective, it may therefore be suggested that practitioners who advise aspiring jockeys on
injury prevention should also include such activities within their training modalities.
In contrast, an alternative explanation for the anomalies identified in the bone health of
jockeys is that jockeys are an ‘atypical’ population given that they are significantly smaller in
size and stature than the average western European male (Kidy et al., 2017). Clearly, further
studies are now warranted utilising much larger cohorts of age and weight matched athletic and
non-athletic control subjects. In addition, histochemical analysis of bone fragments (as
collected following any break or fracture) would also allow for definitive classification of
osteoporosis and osteomalacia.
In summary, we report that purported symptoms of RED-S (e.g. hip / lumbar spine
BMD and RMR) display no differences between apprentice and senior male flat jockeys and
that such parameters do not progressively worsen with years of race riding. This therefore
suggests that there is no clear association between long-term participation as a jockey and
impaired skeletal health. When considered with previously published data examining under-
reporting of energy intake and direct assessments of energy expenditure, we suggest that poor
bone health in jockeys is not due to low energy availability per se but rather, the lack of an
osteogenic stimulus associated with riding. Further studies are now required to directly test this
hypothesis using a large cohort of age and weight matched athletic and non-athletic control
subjects. Additionally, future studies should also attempt to longitudinally track the physical
loading patterns, energy availability and progression of bone mass of prospective senior
jockeys throughout their childhood and adolescence.
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“Male Flat Jockeys Do Not Display Deteriorations in Bone Density or Resting Metabolic Rate in Accordance With Race
Riding Experience: Implications for RED-S” by Wilson G, Martin D, Morton JP, Close GL
International Journal of Sport Nutrition and Exercise Metabolism
© 2018 Human Kinetics, Inc.
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“Male Flat Jockeys Do Not Display Deteriorations in Bone Density or Resting Metabolic Rate in Accordance With Race
Riding Experience: Implications for RED-S” by Wilson G, Martin D, Morton JP, Close GL
International Journal of Sport Nutrition and Exercise Metabolism
© 2018 Human Kinetics, Inc.
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“Male Flat Jockeys Do Not Display Deteriorations in Bone Density or Resting Metabolic Rate in Accordance With Race
Riding Experience: Implications for RED-S” by Wilson G, Martin D, Morton JP, Close GL
International Journal of Sport Nutrition and Exercise Metabolism
© 2018 Human Kinetics, Inc.
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Markers of bone health, renal function, liver function, anthropometry and perception of mood:
a comparison between Flat and National Hunt Jockeys. Int J Sports Med, 34(5), 453-459.
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“Male Flat Jockeys Do Not Display Deteriorations in Bone Density or Resting Metabolic Rate in Accordance With Race
Riding Experience: Implications for RED-S” by Wilson G, Martin D, Morton JP, Close GL
International Journal of Sport Nutrition and Exercise Metabolism
© 2018 Human Kinetics, Inc.
Figure 1 – (A) Measured RMR of apprentice and senior jockeys, (B) Measured versus
predicted RMR in apprentice jockeys and, (C) Measured versus predicted RMR in senior
jockeys.
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“Male Flat Jockeys Do Not Display Deteriorations in Bone Density or Resting Metabolic Rate in Accordance With Race
Riding Experience: Implications for RED-S” by Wilson G, Martin D, Morton JP, Close GL
International Journal of Sport Nutrition and Exercise Metabolism
© 2018 Human Kinetics, Inc.
Figure 2 – (A) Hip Z-score and (B) Lumbar spine Z-score of apprentice and senior jockeys.
(C) Hip Z-score and (D) Lumbar spine Z-score plotted against years of race riding experience.
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“Male Flat Jockeys Do Not Display Deteriorations in Bone Density or Resting Metabolic Rate in Accordance With Race
Riding Experience: Implications for RED-S” by Wilson G, Martin D, Morton JP, Close GL
International Journal of Sport Nutrition and Exercise Metabolism
© 2018 Human Kinetics, Inc.
Table 1. Comparison of age, race riding experience, anthropometric characteristics and
hydration status (urine osmolality, UO) between apprentice and senior jockeys. Data are
presented as means ± SD (range). * denotes significant difference, P<0.05.
GROUP
Apprentices (n=17)
Senior (n=14)
T-test
Age (years)
19 ± 2 (17 to 24)
32 ± 7 (21 to 49)
*P=0.01
Years race riding
3 ± 2 (1 to 8)
16 ± 7 (5 to 33)
*P=0.01
Height (cm)
170 ± 5 (162 to 177)
166 ± 5 (156 to 176)
*P=0.04
Body Mass (kg)
56.2 ± 2 (46.6 to 60.4)
56.4 ± 3 (51.2 to 62.9)
P=0.83
Body fat (%)
13.7 ± 2.6 (7.6 to 18.5)
12.5 ± 1.9 (9 to 15.5)
P=0.14
Fat Mass (kg)
7.5 ± 1.7 (3.9 to 10.4)
6.8 ± 1.4 (4.9 to 10)
P=0.22
Fat Free Mass (kg)
46.4 ± 2 (44 to 51.3)
45.7 ± 3.1 (40.8 to 51.8)
P=0.48
UO (mOsmol.L-1)
816 ± 219 (200 to 1080)
704 ± 310 (200 to 1090)
P=0.31
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