You could ask a friend or significant other for help but probably don't want to rely on them every single day... for the rest of your life. Here, a quick trick that quite literally has your back.
What you need: Your arms and a bottle of lotion.
What you do: After showering, apply a strip of lotion to the backs of your forearms. Starting at your lower back, crisscross your arms in a windshield wiper motion to distribute the lotion evenly across the middle of your back (which is typically the spot that's most difficult to reach). Moisturize the tops of your shoulders and upper back as you normally would.
Why it works: While your hands can only reach so far, your forearms are much longer and cover more surface area in a few swipes.
Pro tip: Don't forget to show your neck and décolleté some love as well. The skin there is prone to aging because it's super thin and is almost always exposed to the sun. Just make sure to use gentle, upward stroking motions so as not to pull or tug on the delicate area.