Perhaps you should try some spelling variations:
"synchronised swimming" » "synchronize swimming", "synchronised stemming"
"synchronism swimming" » "synchronism stemming"
"synchronising swimming" » "synchronising stemming", "synchronizing swimming", "synchronisations swimming"
"synchronized swimming" » "synchronized stemming"

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: (((((("synchronised swimming") OR ("synchronism swimming"))) or ("synchronising swimming"))) or ("synchronized swimming"))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((((("synchronised swimming") OR ("synchronism swimming"))) OR ("synchronising swimming"))) OR ("synchronized swimming")).
• The words AND, OR and NOT may confuse the search; try adding quotes: "((((((\"synchronised swimming\") OR (\"synchronism swimming\"))) or (\"synchronising swimming\"))) or (\"synchronized swimming\"))".
• Removing quotes may allow a broader search: (((((( synchronised swimming ) OR ( synchronism swimming ))) or ( synchronising swimming ))) or ( synchronized swimming )).
• Adding a wildcard symbol may retrieve word variants: (((((("synchronised swimming") OR ("synchronism swimming"))) or ("synchronising swimming"))) or ("synchronized swimming"))*.