Golf
A day on the links is a great way to catch up with old friends, and you can still do it with a portable concentrator and an extra battery pack in case the game runs long.
Consider renting a cart to prevent over-exertion and schedule a day when rain isn't in the forecast to keep your portable oxygen concentrator dry.
Despite Mark Twain's observation that "Golf is a good walk spoiled," there's nothing like the satisfaction of sinking a long putt then celebrating at the 19th hole.
Walking
Speaking of walking, this activity requires no gear besides some sturdy, comfortable shoes and your lightweight concentrator, like the ARYA Mini.
If you've been sedentary and your doctor is urging you to get some exercise, start with a walk to the mailbox or around the block to gauge your stamina. If you have balance issues, consider using a wheeled walker with a basket and flip-up padded seat in case you need to stop and rest.
As you increase you walking range, whether to the neighborhood store or around a nearby park, consider bringing a cell phone or get a walking buddy to keep you motivated. If weather is an issue, walk the local mall; many shopping centers are open before the stores just for this purpose.
Gardening
When the weather gets warm and spring is in the air, you may miss the feel of potting soil between your fingers and the satisfaction of pulling out all those pesky weeds.
There's no reason not to get out there and work your garden even if you're on oxygen therapy.
Consider getting a gardener's bench or a padded knee rest, available at most home improvement stores, to keep the stooping and knee pain down to a minimum.
Remember to bring a water bottle with you, if you're working in the sun, to stay well hydrated, and get your children or grandchildren to help with the big bags of potting soil; they'll get repaid in fresh tomatoes and zucchini.
Fishing
You've seen those bumper stickers: "The worst day of fishing is better than the best day at work."
Whether you're an experienced fly fisherman or just want an activity to do with your five-year-old grand kid, fishing is a great way to enjoy the outdoors, and you can still do it while on oxygen therapy.
Don't forget to bring an extra battery pack just in case the day gets long. Consider using a wheeled cooler for hauling the bait or that mess of fish at the end of the day.
Remember, with a little bit of planning, you can easily and effortlessly incorporate a portable oxygen device into your outdoor activities and keep up a level of energy you may not have thought possible. Give it a try!