Tucked away in the 5e Player's Handbook, on page 176, is a small paragraph detailing a variant encumbrance rule. You're still weighed down and can't move if you carry 15x your Strength score. But now there are gradations. If you carry 10x your Strength, your Speed is -20, and at 5x Strength your Speed is -10. I can just see the poor, heavily encumbered gnome waddling along at a Speed of 5.
To help the players manage these encumbrance levels, I added some small boxes to the bottom of the character sheet where they can write down their encumbered, heavily encumbered, and overloaded levels.
It turns out that, with just their starting gear, all of the PCs in my game were encumbered, so they all suffered a -10 penalty to Speed. This proved a rude awakening for the players, and has become somewhat an area of focus in the sessions. In future posts I'll outline how I use cards to help players more easily calculate their equipment load, and how the lowly backpack has found a center stage tactical role.