Going to the gym is intimidating enough, but not knowing how to pick the right weight to use for an exercise can make a novice’s trip to the gym even more uncomfortable. If you grab too light of a weight, you’ll feel you wasted your time, while too heavy of a weight can lead to injury.

But it is very important to grab the right weight. In a 12-week long study published in the Journal of Applied Physiology, researchers found that subjects gained the most strength when using a weight that corresponded to 70% of their 1 repetition maximum (meaning 70 % of the heaviest weight they could lift in the exercise).