Complex sentence: It was during this time that the whole of ski jumping as a sport heralded a major transition in technique: until the early 1990s most athletes used the parallel style, in which the skis were held close together and parallel to each other.
Split into simpler sentences: It was during this time that the whole of ski jumping as a sport heralded a major transition in technique. Until the early 1990s most athletes used the parallel style, in which the skis were held close together and parallel to each other.