Between 6-8 months is generally when most toddlers sit up on their own
Since someone would be performing wind sprint activities, it is guaranteed when performing any activity is to get better overtime so I would say to "work above your target heart rate"
Avoid smoking and using tobacco products. Be physically active every day. Eat a heart-healthy diet. Keep a healthy weight. Keep your blood pressure healthy. Keep your total cholesterol healthy. Keep your blood sugar healthy.
