כשעומד מברך: ברוך אתה ה' אלוקינו מלך העולם, זוקף כפופים
When a person stands up straight --when he or she wakes up in the morning-- recites the blessing, zoqef kefufim, "Blessed are You, HaShem our God, King of the universe, Who raises up those who are bowed down".
The words zoqef kefufim are found in Tehilim (146:8). There, King David praised God for helping the suffering righteous, out of His love for them. HaShem defends them, feeds them, delivers them and among other things, He helps them to stand up (zoqef), when they are so exhausted, humiliated, troubled or oppressed that their bent backs (kefufim) can not stay straight.
Also, in the famous Psalms, Tehila leDavid (145. aka, ashre yoshebe betekha) David haMelekh praises HaShem Who supports all those who are about to fall, and straightens up all those who are bent down, providing them food and sustenance.
In birkot hashachar, the Rabbis used this Biblical expression, zoqef kefufim, and applied it beyond the concept of people who need God's help to come up from their suffering. It is all of us who also use HaShem's help to stand up every morning. Following the idea of seeing God's intervention in every micro-activity we perform each morning, when we get out of our bed and stand erected on the floor we express our praise to HaShem saying this blessing. When sleeping, most people (see here) adopt a fetal position, i.e., lying curled on one side with legs bent. Therefore, we praise HaShem for the fact that we can stand in an erected position, which according to rabbi Hayim Palagge (yafe laleb), is one of the features that distinguish us, human beings, from animals.