Here are excellent deadlift variations and Jefferson curls for building mobility in the posterior chain area (lower back, glutes, hamstrings).
Deadlifts are amazing strength builders for the posterior side of the body, but with little tweaks they can also be incredibly useful for developing posterior mobility.
The deadlift variations demonstrated here will work flexibility (pike) and strength at the same time turning the deadlifts into a real mobility exercise.
You can expect to see great benefits in overall lower body/back health, but also a massive boost in sports, martial arts and plyometric work (explosiveness comes mostly from the hips).
These are Jefferson curls and they are commonly used by gymnasts to develop posterior mobility.
The back is supposed to round. Lower the weight as low as you can, hold it there a couple of seconds and then pull yourself up. That's one repetition. You can do Jefferson curls for 5 to 15 repetitions per set.
Start light - just a plain stick is enough in the beginning. Later you can gradually increase the weight. Some are able to Jefferson curl their entire bodyweight so the sky's the limit here.
Elevated Romanian Deadlift
Elevated romanian deadlifts are another amazing way to strengthen the posterior chain.
The legs stay relatively straight (you can also do the romanian deadlift exercise with locked stiff legs) and you just pull the weight up with a straight back like you would do in a conventional deadlift.
For beginners who aren't very flexible, the romanian deadlift alone will be enough. Start light (40 to 80 kilos) and do the exercise for 5 to 10 repetitions.
Eventually you can start elevating your legs (by placing plates beneath your feet for example) to increase the range of motion and thus the effectiveness of the exercise.
Elevated Snatch-Grip Deadlift
By using a snatch-grip (wide grip), you increase the range of motion of the deadlift because you need to pull from a lower position.
Your upper back (especially the upper trapezius muscles) and grip strength are also developed very nicely.
Similar to the previous progressions, start light and do the deadlift for 5 to 10 repetitions per set.
Train hard, stay safe.