<https://www.medicalrecords.com/health-a-to-z/knee-extensions-for-chronic-obstructive-pulmonary-disease-copd-multimedia>
<http://schema.org/description>
"Before starting any exercise program, talk to your health professional. He or she may ask that you do specific exercises and will help you determine how often and how long to do them and your long-term goals. Start the exercise slowly and gradually. Either keep track of how long you can do it or count the number of..."
<https://www.medicalrecords.com/health-a-to-z/knee-extensions-for-chronic-obstructive-pulmonary-disease-copd-multimedia>