Walking after doing nothing in a heatwave

During summertime the heat is almost unbearable. Maria regrets walking outside in such weather conditions after spending some time doing nothing. It feels like her body is out of practice.  

Her legs are swollen and she is dehudrated. When she was out of her house she even felt like she would faint. Probably because of the heat and the exhaustion. She wonders if this was the right choice or that she overestimated her strength and endurance.