This study looks at how children with blood clots (called deep venous thrombosis, DVT) and lung clots (pulmonary embolism, PE) are affected over time. Children can join if they are 8 to 21 years old and can speak English. The study takes place in Dallas and involves different tests over a 3-day visit at 12 weeks and 12 months. These include exercise and lung tests, heart and lung scans, muscle scans, and blood tests. Participants also fill out several questionnaires. Some children are part of a control group who either have restrictions on exercise or are healthy.

• Time Commitment: Two visits over 12 months.
• Tests and Procedures: Includes exercise tests and MRI scans.
• Eligibility: Must be able to speak English and fit age criteria.

Children cannot join if they have heart or kidney problems, certain diseases like diabetes, are pregnant, or have severe asthma. If a child had a blood clot before or can't take blood thinners, they also can't join. The study aims to better understand these conditions in children, but it's important to consider the time and tests involved.