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

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

• Performing a fuzzy search may retrieve terms with similar spellings: (((("synchronism swimming") or ("synchronising swimming"))) or ((("synchronize swimming") or ("synchronizing swimming"))))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: (((("synchronism swimming") OR ("synchronising swimming"))) OR ((("synchronize swimming") OR ("synchronizing swimming")))).
• Removing quotes may allow a broader search: (((( synchronism swimming ) or ( synchronising swimming ))) or ((( synchronize swimming ) or ( synchronizing swimming )))).
• Adding a wildcard symbol may retrieve word variants: (((("synchronism swimming") or ("synchronising swimming"))) or ((("synchronize swimming") or ("synchronizing swimming"))))*.