If your log file was created without a growth factor (either percentage or maximum size )-- a most unusual configuration. That said unless your database has undergone a significant increase in activity, i.e. many new rows inserted, many updates and deletes, and this level of activity is NOT expected to be repeated, shrinking the log file can be deleterious as noted by George Sibbald

and as with any fragmented file the time for IO operations will increase. Further if the size is a result of normal operations, after shrinking the log file it will just grow again. Remember the log file is truncated as a part of normal operation of the database engine (check points) and in the Simple backup mode. The freed up space is reused. So attempt to learn what the normal every day operational size is and leave the log file alone.