Complex sentence: The handicapper works out what mark or handicap the runner will have according to their previous performances in the sprint, currently the most a runner may be handicapped is 10 metres, although this is occasionally increased to 11.
Split into simpler sentences: The handicapper works out what mark or handicap the runner will have according to their previous performances in sprint events. Currently the most a runner may be handicapped is 10 metres, although this is occasionally increased to 11.