Long slow distance (LSD) is when you exercise for a long time at a slow pace. Imagine you are walking to the store with your mom. You know it will take a long time to get there, but you are not in a rush, so you walk slowly. That is LSD!
When people do LSD exercises, they usually do them for a long time, like running for 30 minutes or more, or biking for an hour or more. They also do them at a slow pace that they can keep up with for a long time, without getting too tired.
LSD exercises are good for your body because they help you build endurance, which means you can keep going for longer without feeling tired. It also helps your heart get stronger, which is important because your heart is what pumps your blood around your body.
So, next time you go for a long walk or bike ride with your family, remember that you are doing LSD exercises and helping your body get stronger!