Powerlifting makes your muscles stronger - but not the muscles in your lower back
Powerlifters squat and dead lift with considerable weights, but this does not make the muscles in their lower back any stronger. British sports scientists at Southampton Solent University discovered this. Yet we know from experimental studies [PeerJ. 2015;3:e878.] that the development of those muscles counteracts lower back complaints. Should powerlifters who want to protect their lower back include hyper-extensions in their training routines?
The British studied 13 competitive powerlifters [NCPL], 10 recreational powerlifters [CPL] and 36 recreational athletes who did not do weight training [RECT]. All subjects were male.

The powerlifters were about 10 kilos heavier than the recreational athletes, and the competitive powerlifters were able to squat and deadlift with heavier weights than the non-competitive powerlifters.Results
In their lab, the researchers used a device like the one below to determine how strong the lower back muscles of the men were. Although the powerlifters were more muscular and stronger across the board than the other men, there was no difference between the strength that the three groups could develop.

ILEX strength = isolated lumbar extension strength.


"There is currently little evidence showing that progressively increasing strength in the powerlifts, especially the squat and deadlift, will increase lumbar extensor strength", write the researchers."As such, though effective in developing strength in the specific lifts, coaches and exercise professionals should at present not prescribe nor promote the squat and deadlift, as well as their derivatives, as effective exercises to strengthen the lumbar extensors."
"It is unclear the exact impact that specifically training the lumbar extensors has upon powerlifting performance itself. However, if a goal is to specifically target and attempt to strengthen the lumbar extensors, powerlifters may benefit from including specific isolated lumbar extension training."
J Strength Cond Res. 2018;10.1519/JSC.0000000000002722.