The Order of Command

In all my years as a fitness professional, the most common complaint brought to me from  clients is “my hamstrings and lower back are always tight.”   I wish I could tell you that stretching on its own would correct this problem, but that is just a small fraction of the imbalance.
Tight hamstrings and lower back are caused by the Transverse Abdominus (TA) and the glutes not firing properly.  If this chain of command is not in order, then your hamstrings and lower back are doing a job they were not hired to perform!!!
When our bodies begin to move, the TA SHOULD BE the first muscle to fire. Usually injuries, and negative habitual movement patterns prevent this from happening.
By creating pelvic stabilization, your torso and legs can have a proper transfer of energy to support efficient muscular engagement so your back, hamstrings and joints do not!!!
Your core is your foundation of strength.   The TA and multifidus,  are engaged through neutral spine only. Either lying supine, prone, kneeling, half kneeling, and standing.   Not to be confused with the overworked Rectus Abdominus which is a superficial muscle providing no pelvic  stablization whatsoever. Such as the forbidden stomach crunch!!!
Next in command are the glutes. Big muscle, big job.  Over active hip flexor muscles. Sitting, driving, poor training will force these muscles to work instead of the glutes.  Tight hip flexor muscles also cause an excessive lumbar curve which will keep the glutes and core muscles from activating.  Are you starting to see the pattern of pain?
When hiring a personal trainer, be sure you are working with someone whom is qualified in recognizing these imbalances, and knows how to retrain neural patterns, with the proper exercises, and myofacial work utilizing the foam roller. And of utmost importance,  trains you in body movement not just body parts.