 While single bouts of EIPH may not even be apparent to the rider, owner or trainer of a horse unless an endoscopic examination is undertaken, the effect on performance within a single race appears to be significant but relatively subtle.In a 2005 study, horses finishing races with grade 4 EIPH were on average 6 metres behind those finishing with grade 0.However, the effect of repeated bouts of EIPH that occur with daily training may lead to more significant changes and a greater degree of tissue damage over time with consequent loss of lung function.