Maintaining Cardio while Fixing Imbalances

I know this isn’t strictly and “injury” and it’s also not strictly strength-training related, but I figured I’d ask here because there’s a lot of knowledge floating around on this forum.

It’s also kind of a long story – don’t worry, there’s a tl/dr at the end.

I’m a rising fourth-year rower, in college. I’d never done any serious athletics before, but I’d been moderately active up until that point. However, I quickly developed a case of the dreaded lower crossed syndrome, which I proceeded to reinforce over the next three years. After two years of frustrating stagnation and knee and back pain, and then another year wasted in orthotics (with an ignorant greedy podiatrist), I finally managed to dig up the info I needed on why I was so weak and how I ought to fix it.

I’ve already stopped rowing/erging entirely, since I can’t take more than two strokes without my hip flexors tightening up and my glutes shutting down. Cycling and running are okay for a short while but by the 30 minute mark I’ve completely reverted to Neanderthal mode and I can’t do a damn thing about it. I have no idea how swimming will affect this.

I started Starting Strength three weeks ago, but I got the flu last week and erased much of the neurological reconditioning I’d done until that point. Going forward I’m going to keep the weights light and reps much higher than Rippetoe suggests to be sure my muscle imbalances don’t carry over.

However, I’ve got a problem – I absolutely must keep my cardio up until the school year starts. We’re going to be tested on the erg (6k, 22-23 minutes) on the first or second day back in practice, and if I don’t pull a personal best there’s a good chance I may be cut. This would not only be humiliating (since some of my best friends are also my teammates) but would also be a horrible way to end my career in a sport for which I’ve spent thousands of dollars, devoted countless hours to training 5-10 times a week, and given up a good chunk of my social life.

The erg test will probably be on September 1. I’d like to do Neanderthal No More, which will carry me nicely through August. And yes, I know I will get fitter and more biomechanically efficient, but how can I spent the next 7 weeks in “pre-hab” without entirely abandoning my cardio base? Will swimming be okay or will it mess me up like the other stuff?

tl/dr – how do I keep up cardio without worsening my APT and upper/lower crossed syndromes? swimming, maybe, but i’d like confirmation

swimming sounds good if you can do strokes that dont hurt.

Have you tried an elliptical? not to be like its a pussy machine or whatever, but maybe it wont hurt you and you can jack up the resistance and train really hard and at least get your heart rate up real good on that.

Maybe high incline walking?

not great options but much better than nothing.

GPP: sled, backwards stair climbing (you can add banding in the waist to engage your glutes even more), swiming (breast stroke, back stroke)
Rowing: just do lots of pulling, but look for exercises where you angage your glutes like in kneeling position.