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

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

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