You are singing my song.
It's really tough to do this with only a carry on. Especially when your trips involve multiple destinations with different weather conditions and/or multiple purposes (i.e. some business, some visits with family, dining out, dressy events, etc.)
Even more so when your feet do best with many options, as mine do. I know people are always advising us to take one pair of shoes on a trip, but for me, that is just plain laughable. Even for a two day trip I would need 2 pairs minimum.
Here are a few ways I have managed it.
1. Consider how long your trip is. If your trip is very short, alter your workout schedule. Do your heavy workouts before you leave and when you return, even if those are not your usual days. Use one of your travel days as your rest day. Bring a swimsuit and swim in hotel pool (or outdoors!), go for a long walk, do light body weight exercise or yoga in your room with sock feet to stay active. This will allow you to avoid bringing workout shoes at all.
2. If this is not possible but it's still a fairly short trip, consider modifying your regular workouts so you can do them in the privacy of your room. You can do a lot with bodyweight. And maybe add a bit more NEAT (non exercise activity) to your day to step things up, so to speak.
3. If you need to bring running shoes, consider wearing them on the plane or investing in a "travel" pair of cross trainers that are a bit less less bulky than your typical shoes. A pair that will squish down really flat. Caution -- don't go too low profile if you are not used to it. That's how I gave myself an awful case of plantar fasciitis.
4. Keep using a carry on, but switch up what you use for your personal item. Instead of a "purse," bring a sizeable backpack that will still fit under the seat (best) or a large Le Pliage tote (second best) or better yet, both. (In that case, pack the Le Pliage for use as a tote at business events and use backpack on the plane.) In the backpack you can put your computer and lots of other papers etc. along with running shoes and your gym clothes. Pack a dressier bag (a flat style) in your suitcase and bring it out at destination, if needed. This has the advantage of keeping your gym stuff a bit separate from your other things. I have done this often. I use a Patagonia daypack with slot for laptop. It holds a lot more than even my largest tote and is easier to carry.
5. YES to re-wearing workout clothing (if not too disgusting) or washing workout clothes in the sink at night. They almost always dry if made of wicking fabrics. This allows you to take fewer clothing items with you.
6. If your trip is too long or includes too many other variables, let go of the carry-on idea. Life is a lot simpler. Yes, you sometimes have to wait a while for your bag at the carousel, but assuming you're not rushing to make a connection, travelling can also be a lot easier if someone else is dealing with your bag. Also, you can use waiting time to walk more in the airport. I would far rather bring regular luggage and know I'm really prepared to be active outdoors at my destination (even if I need a parka and snow boots, say) than save a few minutes at the airport.
In reality, my main strategies are 1. -- switch up workout days and find other ways to be active at destination, and 6. But I've relied on all of these at different times.
