Rubuta ci gaba don wannan sakin layi - Ta fara wasan motsa jiki na nakasassu yana da shekaru 11, ta lashe lambar zinare bakwai a cikin wasanni da yawa. A shekara ta 2008, tana da shekaru 14, an zaɓe ta ne don wakiltar Burtaniya a Wasannin Paralympic na bazara a Beijing, inda ta kammala ta 11 a cikin mata F42-46 javelin. Ita ce mafi ƙanƙanta a cikin tawagar Burtaniya ta 2008. A shekara mai zuwa ta lashe lambar yabo ta farko lokacin da ta yi gasa a gasar zakarun duniya ta matasa ta IWAS ta 2009 a Switzerland, inda ta lashe azurfa a cikin F46 discus da tagulla a cikin javelin F46. 2009 ita ce shekara ta ƙarshe da Arnold ya yi gasa a gasar zakarun duniya a cikin faya-fayan, yana mai da hankali sosai kan javelin. A shekara mai zuwa ta inganta lambar yabo ta javelin lokacin da ta dauki azurfa a gasar zakarun duniya ta IWAS ta 2010 sannan ta dauki zinare a gasar zakarun duniya ta 2011 wanda aka gudanar a Dubai. A shekara ta 2011 Arnold ya tashi zuwa babban matakin da ke wakiltar Burtaniya a gasar zakarun duniya ta IPC
a New Zealand; ta gama na uku a cikin javelin F46, ta dauki lambar tagulla. A cikin 2012, ta ɗauki lambar azurfa a Gasar IPC. An rubuta mafi kyawunta a F46 javelin a 35.88m a watan Yunin 2012 a Gasar Wasanni ta Wales a Cardiff, wanda ya sanya ta a matsayin ta biyu a duniya a cikin wasanta na shiga wasannin Paralympics na 2012. An ƙara mafi kyawun Arnold a Wasannin Paralympic na 2012 a London tare da jefa 36.27m. A ranar 22 ga Yuli 2013, Arnold ya yi gasa a Gasar Cin Kofin Duniya ta IPC a Lyon. Ta lashe zinare tare da jefa nasara na 37.45m, ta ci gaba da inganta rayuwarta.