I don't know about any scientific research, but anecdotally I have a much harder time doing cardio now compared to pre-LL.
I used to be able to run a sub-5:30 mile, but now I can't even finish a mile at a 10:00 pace (which is slower than my marathon pace pre-LL). My heart rate will go over 190 BPM at that pace and I'm a bit concerned about getting a heart attack or something so I don't push myself. I can pretty much only do elliptical, biking, hiking, and casual sports for cardio (though I'm much more of a bodybuilder when it comes to the gym anyway).
I don't regret doing LL one bit though in terms of sports though. My days of distance running were long past before I even started LL (I hadn't run any half or full marathons for over 5 years as of my surgery date). I can still play a lot of different sports with friends and have fun in the amateur leagues I participate in and I'm still in very good shape visually so it's not a concern to me.
99% of the time modern humans don't need to run more than 30 seconds anyway (to catch the train or w/e)