Lower back pain cause is simple—we are not using our great ape bodies in the way that evolution designed them to be used. Our ancestors hunted and gathered. They moved their bodies every day and for much of the day walking, running, crouching squatting, grabbing etc. Any seats certainly didn't have backrests. All of our ancestors cores were in great shape because they were working them out nearly every waking moment. Our desire to obtain comfort has led us to "convenience ourselves to death".
I do feel the need to clarify that I'm talking about people who have already met Maslow's first and second levels. I do agree that there are people out there who lack in basic food/water, clothing, shelter, hygiene, health and safety. What I'm talking about here is essentially levels 3 and 4.
Great topic, and hopefully I'm not coming off as pedantic when I say that we really need to make a distinction between happiness (which I argue is one of the fleeting emotions no different than fear or anger or embarrassment) and fulfillment (aka serenity, inner peace, contentment). People who are fulfilled embrace all of their emotions (including happiness) without judgement or an attempt to control, and they process them by connecting with themselves and others in healthy ways, which further leads to fulfillment. We are social, emotional apes, and all of the higher order emotions exist in order to bring the social group closer together.
So when it comes to measuring good, we should be measuring fulfillment, which itself is just a proxy for healthy emotional connections with other people. See the Harvard Longitudinal Study, Blue Zones, and Awakened Ape and even what it means to be a prosocial ape as some sources that point towards this theory.