Everyone is different. My back is always better with swimming, in particular, doing flip turns helps. I also feel better after raking leaves (lots of bending not unlike flip turns). However, a lot of people stay away from flip turns and activities like raking because they cause back problems. Sometimes I'm a little stiff in the back/hips after a long ride but running is always fine. Since I haven't been swimming, I've been doing yoga which probably also helps. Not for everyone's taste but since you say it is muscular, I like the books of John Sarno (It's all in your head).

Granted it's a difficult time to do so, but I'd focus on the back pain with a qualified bike fitter and physical therapist instead of looking for different options.

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I think you need to focus on the fact that the more cardio you do, the more tightness you will theoretically get from your body. If you bike 2hrs and run 1hr, you're going to be tight. The lower back is going to take a lot of this tightness and you have to do things to loosen up like stretching or yoga or salt baths, etc. to do the inverse of the activity that you have been doing. For someone like David Goggins, he reflected on the fact that he was go-go-go for years and his body eventually became a ball of tightness that he eventually had to stretch out and loosen up to remain in balance.

Some people stretch to avoid injury - others have to stretch post activity to just loosen up. Its not like you even have to do it right after the activity, but just do some stretching activities at some point in the day to relive the general tight spring that you have wound up in your back and body.

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Yes your probably right. I never stretched or had any warm up routine. Just go-go-go. I guess I need to include a daily short yoga routine and core routine.

Swimming tends to help my lower back issues. Not sure if it stretches me out but when I ramp up the swimming the back pain goes way down.

My back pain and SI joint pain improved and pretty much went away, when I started to use a reverse hyper machine and lowered and extended my bars more.

We are all a bit different, but likely repetitive motions in same plane tends to weaken glutes. So work them, check bike fit, learn proper hip hinge. Even running if glutes weak will transfer to low back. Good websites are plenty but I have used Ready State, Upright Health, Run Smart online. Many are free in youtube reruns.

I think you need to address the issue and not figure out what cardio you can do that won't aggravate it. Try stretching int hte evenings for at least ten minutes before bed. If that doesn't work, see a PT to see what muscle groups are too weak that may be causing the back to tighten up. For me it is glute medius that needs strengthening.

Get a plank routine going to strengthen your core...

Started doing 15-20 mins of core and yogis in the evening. I’m doing downward dog, 3-5 mins of planks, push ups, 10-20 glute bridges, cobra pose, and balancing table. Hopefully that will be enough. Anything else I should consider? I want to up the core so maybe some more planking. Interesting enough, my back is starting to feel better. I stopped biking so maybe this was the culprit but hopefully if I can keep this routine going everyday I’ll be stronger/flexible for the bike.

Any other suggestions?

First, I'd second the advice to get professional attention. A few other thoughts...

If you sit a lot for work you might benefit from a standing desk.

It's possible your lower back is uncomfortable off the bike because you are in a folded-up position and that more linear body positions will help (as is normal for running and swimming). You could try jumping rope if linear body positions seem better. Also, you might be able to stair-climb (don't lean forward too much), or treadmill hike at max incline, or use an elliptical machine without discomfort -- and all of these will transfer to cycling muscles.

I would not recommend a rowing erg.

Swimming or other linear-posture activities might *not* help if the lower back muscles are crampy/knotty and this is what you mean by "tight" -- because engaging the erector spinae muscles to keep the body linear might simply be uncomfortable for extended periods of time.

Hip rotation and posture are very important for the whole posterior chain including your lower back, and affected by length and strength of hamstrings, glutes, quads, other hip muscles, and abs. How do your hips align when you run or stand (look up anterior vs posterior pelvic tilt)? Excessive tilt in either direction can lead to stress and discomfort in your lower back. Consider training your flexibility and strength in all of the main muscle groups that maintain pelvic orientation, focusing on those that are either weak or tight (but not actively injured) to begin with.

I think you're asking the wrong question for two reasons:
1. The priority should be sorting out your back, not implementing a work-around.
2. All lower back pain is not the same, and similarly the activities that aggravate it differ. So, no one can answer your question beyond suggesting experiments.

I have some minor facet joint issues in my lower back. When I'm in good shape I rarely have pain, but I've had a couple of bad spells in the last two years since my son was born, no doubt as a result of lifting him in bad positions from time to time. A crazy baby is not a stable load! The one thing that does NOT make my back worse when it's irritated, is cycling. In fact I often felt better after a ride. Running on the other hand was very risky.

Go to a physio and/or get a bike fit to try and identify the problem.
Back problems typically don't just go away without consequences. Don't make it worse.
I injured my back 18 years ago but since it wasn't too bad I ignored it for the couple of years. By the time I saw a physio the original issue was no longer causing pain, but I'd changed my posture slightly to protect that original injury and the strain from the poor posture had caused some thickening of the vertebrae causing minor impingement on nerves exiting the spine at the lower back. The original injury is fully recovered, but there's no reversing the secondary damage. It's not the end of the world but I'd rather not have to live with a temperamental back. Don't make the same mistake. Deal with it early before you cause bigger problems. Most people end up with back problems of some sort, but do what you can to avoid, delay, or minimise them. A bad back can really screw up your life!

I have found that core training helped my low back. It could also be a coincidence that I was just getting back on the bike after shoulder surgery and winter, and got used to being back on the bike after 6-7 months. But I think core training really helped.

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