A few weeks ago, I injured my back...I believe a herniated disc. I was big on weight lifting, even though my numbers never got a chance to reach respectable levels and I followed the Stronglifts 5x5 routine. Now, I'm trying to find a replacement routine that will deliver the same or better intensity, minimize strength loss while I recover, and and get me to lose fat at least as fast as before. I have tried several exercises experimenting with how it makes my back feel, mostly trying to find the limit of weight I can lift without irritation. This has meant dropping Stronglifts, since 4 out of the 5 involves direct force on the spine.

Brief overview of my diet since that's important.
-Follow the guidelines outlined in this video: Fat Burning & Muscle Diet Plan - YouTube
-Instead of the weekend carbrefeed, I plan to do only 1 refeed day, based on the assumption that my lifting intensity won't be high enough to require 2 days
-That refeed day I moved to Friday, moving the 24 hr fast to Tuesday
-Also will have a 16 hr daily fast like LeanGains
-Cycling my calories: One day is at maintenance, another at 200 above maintenance [both high fat, high protein days], the refeed day is 400 below maintenance, the remaining eat days are 600 below maintenance, and the 24 hr fast day, I break the fast late in the evening with only 400 calories of mostly protein)

I've done my best to maintain a Stronglifts routine. My three lifting days are Friday, Sunday, and Tuesday (purposefully timed to have one land on the refeed day, while putting 2 of 3 lifting days on the weekend, the only real free time I have).
-In place of squats, I have substituted horizontal leg press, supplementing with the back extension machine because I am aware the leg press if far inferior to the squat being completing devoid of posterior work
-I've kept the bench press
-In place of barbell rows, I do pullups
-In place of barbell overhead press, I've use the overhead press machine
-In place of deadlifts, I do chinups
I've chosen to place my weight for each exercise as follows. Since minimizing strength loss is all that matters, this weight will never increase.
-Leg press: 250 lbs
-Back extension: 125 lbs (any higher hurts my back)
-Bench press: 185 lbs
-Overhead press: 100lbs
-Pullups/chinups: BW (5 sets maxed out)
5x5 is implies sets with rest in between, but if I never increase the weight, rest will become less necessary as my body becomes conditioned to that weight. So I figured it would be okay to simply make it a goal to accomplish 25 total reps of each exercise, resting on an as needed basis. It's still the same work done, right?

Sunday: After lifting, I will do a sprint session as outlined in PB fitness. I haven't yet tried sprints since my injury, so it may not come to be. If so, I will instead get my heart rate to 75% of max for 30 minutes with some steep treadmill walking (my resting heart rate is too low for walking outside to raise my heart rate significantly)

Tuesday: Even though I said I don't have much free time on the weekdays, since this is my fasting day, less time with meal prep means I can fit in 30 minutes of elevated heart rate after my lifting session.

Friday: After lifting, will once again be 30 min of elevated HR.

The remaining days (Monday, Wednesday, Thursday, and Saturday) are where I need the most analysis. Thursday is an elevated HR for 30 minutes and that's it. Saturday is the same except for a a whole 60 minutes thanks to the free time the weekend allows.

On Monday and Wednesday: I was thinking of doing some bodyweight stuff for my conditioning. I'm afraid that my lung power and endurance will go down as the weights in the gym get easier to lift. I recently found a book called Combat Conditioning. I did a workout based on it and it was a killer. I have no doubt it would improve my stamina. But it left my muscles sore the next day (a lifting day) and I hadn't even completed the workout. Matt Furey is talking about hundreds of reps of his exercises and I really wonder if it's necessary. I'm not sure I have the gumption to do his workouts even twice a week. But if I only did it once, would I even see any benefit? Would I be better off filling these two days with the less intense PB fitness training. Stamina aside, I still need to do something, probably more than once a week, for the sake of my stability and other smaller muscles, which are no longer getting worked in the gym due to my usage of mostly machines.

If you made it this far, thank you for your willingness to help.

One last thing: I'm fairly sure my injury was caused by bad squat form, which may possibly be caused from me mistakenly sucking my abs in (vs. pushing them out), but is more likely caused by low hip mobility because I sit for upwards of 14 hours a day in unergonomic classroom chairs. So I plan to foam roll all appropriate muscles as well as perform hip mobility stretches. I would prefer to do these as infrequently as possible, so please provide suggestions on where this would best fit in my routine.