Lower back pain when exercising...

Definitely stretch your hamstrings and butt as well.

I have lower back issues and they are aggravated by running. I was told it is the action of the leg extending back that aggravates it. Are you running? There are lots of street he's you can do for your lower back my favourite is laying down and bringing your knees to your chest.mm

Also try doing core exercises. Pilates is great and when my back was at it's worst when I did Pilates it was the only time I wasn't in pain. Luckily one of my best friends teaches Pilates so I could do it a lot.

Ditto to what Stars said but to elaborate a bit on her response here is my suggestion that has helped me in these situations. Yoga can be tricky and if you male our ego sometimes gets in the way but it is awesome! BTW I'm chubby too so even us chubby folks can fix the issue!

I do not have chronic low back issues, however, from time to time it will flare up something fierce. When that happens it's a very tough few days. This happened a couple of months back when I started doing P90X3 after a "winter break"! During one of the workouts I started to feel the tightening early on and by the end it was unbearable so I stopped for the day. The next day it felt 10X worse and figured I messed something up so I went to the Doc. Now this may not be relevant to you if you had a major injury but figured I would share. Doc also advised to not stop working out as it'll just come back again since he determined it was not disc related.

What I found out was that there are so many tiny muscles throughout our Core area that all work in concert with each other. Some are for push, some for pull, some stabilize, etc. If any of them get out of whack the pain is often referred to the lower back. This is especially true in the case of people that have desk jobs, two of the primary culprits are the Psoas (it's partner is the Illiacus and combined they're often referred to as he Iliopsoas) as well as the Piriformis. Then you have the major ones most know about with your hamstrings, glutes, IT band.

Unlike many of the common muscles that we can touch these are buried deep. For example, the Psoas connects from your lumbar spine (lower back) to the top of the femur (thigh bone). Normally this muscle is long (think standing upright) but if you sit a lot this muscle can often times shorten. You do your wonderful workouts, it stresses it and alas lower back pain surfaces as the muscle is essentially pulling your back and hips closer together as if in a sitting position since that's what it's been trained to do (trained as in sitting for long periods of time).

Same type of situation with the Piriformis which stabilizes your hips and is deep under your Glutes. Good thing is if you hit the Psoas with stretches you'll get the Piriformis and many of the other muscles in this region. A foam roller is great as well. Just sit on it and roll back and forth...that's your Piriformis. This is not to say these are the only sources as it could also be tight hamstrings, tight back muscles, tight IT band and any of those lovely muscles in and around the Core area.

There are tons on Psoas stretches out on the net you could find to incorporate into your program. Same thing for Piriformis, Hamstrings, Glutes, etc. Pull a few of those together for each muscle group and use it as a DAILY program. You will notice that some of the stretches you'll find are repeated in all of them so definitely use those. Don't just target one muscle group...get them all. Figure out a 15 - 20 minute stretch program and do that at least 3X's a week and in my case I did this DAILY for 2 weeks before working out. Pain was pretty much gone after the 1st couple of days.

That is what worked for me and my exercise induced lower back pain. Lastly, FWIW, P90X3 (i'm not a coach but a user) has a dynamic stretching program called Dynamix. Check Youtube as someone may have taped their full workout on there. Follow that as it incorporates just about every stretch you'll find when looking for the stretches I suggested above. I actually scrapped what I found and just used that program. Note, this is a 30 minute dynamic (i.e. moving) stretching program so you get a little more calorie burn than your typical stretching.

There are so many different anatomical and physiological reasons for back pain that you really don't know how to address the problem without a proper diagnosis. This could be something as simple as tight hamstrings or being too heavy or something as bad as radiculopathy, degenerative disc disease or rheumatoid arthritis. As of now, there's really no way of knowing what to do.