Complex sentence: He began his athletic career by running in the Young Athletes League for his local club, Rotherham Harriers and his 800 m time of 1 minute 53.3 seconds has been the Under 17 record since 1979.
Split into simpler sentences: He began his athletic career by running in the Young Athletes League for his local club, Rotherham Harriers. His 800 m time of 1 minute 53.3 seconds has been the Under 17 record since 1979.