As a physical therapist, I am very concerned about the impact of competitive sports on growing bodies (you can see more about that in this back post). However, I am equally concerned with the rising rates of obesity, Type II Diabetes, and lack of exercise in our youth. Statistics from the Center for Disease Control and Prevention show that less than half of children ages 12 to 15 are aerobically fit. You can see more in the National Public Radio news article entitled, “Are American Teens Becoming Even Wimpier Than Before?”
In the past, I have also wondered about the physical fitness levels of many homeschooled children. There was a study done recently regarding physical fitness levels of homeschooled children versus children that attended school. It was published in The Old Schoolhouse Magazine and posted on Facebook sometime during this spring, but I cannot find a link to it. The research had a small sample number as I recall, so it may not be completely conclusive, but the results were that the homeschooled children were NOT as physically fit.
Why would this be?
I have always thought that in school, at least a child may be walking to a bus stop (unless they are driven to school). They may be walking around the building from class to class or down to the cafeteria or to the art room. That could be one possibility. I am not sure if P.E. makes a huge difference since many districts seem to be cutting back on that and recess, but that could be another possibility.
I think it is very important that we make movement a priority for our children, starting in the early years and moving forward. It is often an area that we do not intend to neglect, but perhaps we find the daylight hours going fast homeschooling multiple children and caring for a home.
1. If physical fitness, truly vigorous physical fitness, is a priority for you and your spouse/partner, then your children will be more likely to want to emulate that. It can be hard when children are very small, but it can be done and as children grow, physical fitness and movement encompasses the entire family.
2. Family fitness matters. Plan weekend hikes. Take one afternoon a week and hike somewhere with other homeschool families but try to actually move, not just putter. 
Push a little on bike rides or walks or family runs for distance for older children. Play tag or soccer in the backyard as a family. Encourage and set up neighborhood kickball games, or four square.
3. Think about activities that are not competitive, but will get your child moving throughout the day.
4. Screen time is not helpful for increasing physical fitness. Time spent on a screen is time that could be used toward movement. We all have a certain number of hours in a day – where is your priority for yourself and your family?
5. Some activities, such as Scouts or 4-H, may have movement built in in terms of earning badges or participating in activities.
6. Check out what is in your area – the local YMCA, your local chapter of Girls On The Run or a similar organization. Your local state park system may also have opportunities to earn badges or be part of a club for cycling, paddling or mountain biking.
7. Encourage movement during the day. Running around the house and yard may be enough for smaller children under the age of 9, but children ages 9 and up really need some vigorous movement where they are sweating! Needs for physical fitness change with developmental level.
8. How many steps do you take a day? That may give you an idea of how much general activity is going on in your household. You can buy a pedometer for very little money in almost any drugstore at this point and then all you have to do is shoot for more steps than you took yesterday.
9. Remember things such as the President’s Challenge are open to homeschoolers as well. See this link to get started: https://www.presidentschallenge.org/participate/ed-homeschoolers.shtml
10. Get moving every day by including physical fitness in your homeschool planning. Assign it a time so it actually happens!
Tell me your favorite ways to get moving during your day for you and your children. Super points for ideas for our slower moving teens who want to sleep later.
Many blessings on getting moving,
Carrie
The Parenting Passageway 
Many of the homeschooled children I know are dedicated athletes, and infact their homeschooling supports their sporting schedule in a way regular schooling wouldn’t. I would say that allowing (encouraging) young children to play freely outside is the best method of guiding them towards a physically active future, perhaps even involving serious sports.
Amen! Being physically fit is so important. I really appreciate your reminders to that, and your summer parenting project idea.
There is this homeschool PE curriculum called Family Time Fitness which is pretty good. They had a coupon code a while back where you could get the first core for free, and we’ve had fun with it. We are a pretty active family already, but it’s fun to have something structured with new things to do every day (not that I ever remember to do it that often :P). I always make sure that my son is having fun, so it’s never something we have to do, but he always wants to do it.