SummaryThe primary objective is the description of bone mineral density (BMD) and body composition in newly licensed jockeys. One in three male, flat jockeys has a very low bone mineral density. Further research is needed to assess the short-term risk of fractures and long-term health implications of these findings.IntroductionDescribe bone mineral density (BMD) and body composition in entry-level male and female, flat and jump jockeys in Great Britain.MethodsData was collected on jockeys applying for a professional jockey license between 2013 and 2015. Areal BMD at the spine, femoral neck (FN), total hip and body composition were assessed by dual-energy X-ray absorptiometry (DXA) scan. We examined differences between BMD and body composition by gender and race type (flat or jump). Volumetric bone mineral apparent density (BMAD) of the spine and FN was also calculated to account for group differences in bone size.ResultsSeventy-nine male flat jockeys (age 18.5 ± 1.9, BMI 19.0 ± 1.4), 69 male jump (age 20.7 ± 2.0, BMI 20.6 ± 1.3) and 37 female flat jockeys (age 19.3 ± 2.0, BMI 20.8 ± 1.7) took part in this study. Spine BMD Z-scores ≤−2 for male flat, male jump and female flat jockeys were 29, 13 and 2.7%, respectively. Spine BMD was lower in male than female flat jockeys (p<0.001). All BMD scores were lower in male flat compared to male jump jockeys (p<0.001). Body fat percent (BF %) was lower in male flat jockeys compared to male jump and female flat jockeys (p<0.05). Lean mass index (LMI) was lower in male flat compared to male jump jockeys (p<0.001).ConclusionsMale flat jockeys had a significantly lower BMD, LMI and BF% compared to jump jockeys and female flat jockeys. Male flat jockeys had lower spine BMD scores than females. Individual bone maturation may influence these findings. Further investigation into the relevance of low BMD and altered body composition on jockey health is required.Electronic supplementary materialThe online version of this article (doi:10.1007/s00198-017-4086-0) contains supplementary material, which is available to authorized users.
Go is a popular statically-typed industrial programming language. To aid the type safe reuse of code, the recent Go release (Go 1.18) published early 2022 includes bounded parametric polymorphism via generic types. Go 1.18 implements generic types using a combination of monomorphisation and call-graph based dictionary-passing called hybrid. This hybrid approach can be viewed as an optimised form of monomorphisation that statically generates specialised methods and types based on possible instantiations. A monolithic dictionary supplements information lost during monomorphisation, and is structured according to the program’s call graph. Unfortunately, the hybrid approach still suffers from code bloat, poor compilation speed, and limited code coverage. In this paper we propose and formalise a new non-specialising call-site based dictionary-passing translation. Our call-site based translation creates individual dictionaries for each type parameter, with dictionary construction occurring in place of instantiation, overcoming the limitations of hybrid. We prove it correct using a novel and general bisimulation up to technique. To better understand how different generics translation approaches work in practice, we benchmark five translators, Go 1.18, two existing monomorphisation translators, our dictionary-passing translator, and an erasure translator. Our findings reveal several suggestions for improvements for Go 1.18— specifically how to overcome the expressiveness limitations of generic Go and improve compile time and compiled code size performance of Go 1.18.
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