Heidi Klum tries to work out every day.The 39-year-old model doesn't have much free time as she raises her four kids, Leni, eight, Henry, seven, Johan, six, and Lou, three, but tries to incorporate exercise into whatever she is doing in order to keep fit.She said: "My schedule is always really hectic so I try to incorporate exercise into my everyday routine as much as possible. Whether we're jumping on the trampoline in the backyard or taking our dogs Freddie and Max for a hike, my kids definitely keep me in shape."The 'America's Got Talent' judge thinks it is important to stay in shape for the sake of her own self-esteem.She added to America's OK! magazine: "Having been in the fashion industry for many years it is important for me to stay in shape, plus with my busy schedule it helps me to stay energised throughout the day. And like any woman, I want to feel attractive and confident so I can wear hot dresses and heels and always be date night ready."