在MySQL中进行简单更新的时间确实很长

Question

I have a really simple update that for some reason is taking almost 5 secconds to update one row.

The update statement is:

UPDATE `li_webs_trans`.`li_sentances` 
SET `target_sentance` = 'вашими пільгами тепер займається відділення Управління соціальної    допомоги та допомоги на дому, вказане нижче.' 
WHERE `trans_id` = '483' 
AND `sentance_id` = '5';

The table being updated is:

CREATE TABLE `li_sentances` (
`trans_id` INT(11) NOT NULL,
`sentance_id` INT(11) NOT NULL,
`eng_sentance` VARCHAR(10000) DEFAULT NULL,
`target_sentance` VARCHAR(10000) DEFAULT NULL,
`traget_lang` VARCHAR(50) DEFAULT NULL
 ) ENGINE=MYISAM DEFAULT CHARSET=utf8

I thought that there may be some indexes updateing, but I checked and there are no indexes on the table. The rest of the database is performing as expected. The table is not super huge, only 106,000 rows. Any Idea what could be slowing down the insert?