This is part of an ongoing series from PhinneyWood’s own Seattle Strength & Performance
Strength training is becoming increasingly popular and the importance of “lifting heavy” for bone density and muscle loss with aging is heavily discussed topic. But how heavy is “heavy” enough to get those results? There’s a lot of space between “too easy” and “too heavy,” and finding that sweet spot is one of the most important skills you can develop as a strength trainer. Don’t fret — we’re here to help! But first, a few disclaimers before we get into it:
- If you’re lifting any weights at all with the intention of lifting heavy – you’re doing great! Something is always better than nothing.
- The only “non-negotiable” here is that you participate in progressive overload by doing slightly more over time. If you’re brand new to lifting weights, you probably don’t need to stress too much about if the weights are heavy enough, you just need to go lift them.
- Too heavy too soon can also be an issue as it increases your risk for injury. The goal of this blog post is to help you figure out a starting point, but if your weights are increasing (even slowly) over time, you’re doing great! Keep going!
Here are three practical ways to figure out if the weight you’re using is actually heavy enough.
1. Ask Yourself How Many More Reps You Could Have Done (or literally try it!)
This is the simplest gut-check there is, and it’s more revealing than most people realize. This strategy is called “Reps in Reserve” or RIR and it’s a scale of 1-10 that many coaches use to assign intensity or difficulty to exercises. To determine your RIR, at the end of your last set, pause and ask yourself honestly: “If I absolutely had to, how many more reps could I have done with good form?” Not sloppy, grinding reps — clean ones.
Or even better – next time you’re in the gym, try it out! Especially for exercises that don’t pose a big safety risk of failing (think dumbbell exercises, machines, etc.). Our guess? You’re way stronger than you think! If your answer (or result) is five or more, the weight is probably too light. If your answer is zero, depending on your training age, the weight might be too heavy! Training to failure is a good tool for certain goals, but probably not important or worth the potential risk in the first 6 months of strength training.
A good general target is finishing your last set feeling like you had about two to three reps left in the tank. You’re not completely spent, but you couldn’t have gone much further without your form breaking down. That zone, where you could’ve done a few more but wouldn’t want to, is where you want to spend most of your training time.
Reps in Reserve is a useful mental model because it shifts the focus from the number on the weight to the actual demand being placed on your individual body. Two people can lift the same dumbbell and have completely different experiences depending on their strength level. What matters isn’t the specific number: it’s how challenging it is for you.
2. Watch the Speed of the Weight
A second option is to watch the speed of your reps, which can tell you a lot about whether the weight is in the right range.
Here’s the general pattern: if the weight moves very quickly and easily through the full range of motion and the last rep looks just as easy as the first one, the weight is probably too light. If it slows down toward the end of your set but you’re still able to complete the reps with good form, you’re in a good spot. If the weight grinds to a near stop and your form starts to fall apart, it’s likely too heavy for that rep range.
A practical way to use this: on your first rep of a set, notice how fast the weight moves. Now compare that to your last rep. Some slowdown is normal and expected — that’s fatigue doing its job. But if your last rep moved at about the same speed as your first, the weight probably isn’t heavy enough to create the kind of demand that builds strength over time.
On the flip side, if the weight starts moving slowly from rep one and your form is breaking down early in the set, scale back. Grinding through poor reps with a weight that’s too heavy isn’t getting you to your goals quicker, it’s likely just more risky.
3. Rate It on a Scale of 1 to 10
This one is called RPE (Rate of Perceived Exertion) and it’s a very useful tool in strength training once you get the hang of it, although it does take some time to get used to.
The concept is straightforward. After a set, you rate how hard it felt on a scale of 1 to 10. A 1 would be barely any effort at all and a 10 would be absolute maximum effort, nothing left, couldn’t do another rep if your life depended on it. RPE is also the inverse of RIR which we talked about earlier. An RPE of 10 is a RIR of 0, make sense?
For most strength training purposes, you want to be working in the 7 to 8 range on your working sets. A 7 means it was challenging but you had a few reps left. An 8 means it was hard and you had maybe two reps left. A 10 is true failure which can be useful occasionally, but not where most people should be living most of the time.
The beauty of RPE is that it accounts for everything going on in your body on a given day. We don’t always feel the same. Sleep, stress, nutrition, and how recently you trained all affect how hard a given weight feels. RPE lets you auto-regulate on a day when everything feels heavier than usual; an RPE of 8 might look different than it does on a great day, and that’s okay. The scale travels with you.
It takes a little practice to calibrate and most people tend to underestimate their RPE at first, rating things as harder than they actually are. But over time it becomes a genuinely reliable internal compass for training intensity and allows you to adjust to how your body is feeling on a given day. Bodies are not machines
Putting It All Together
These three tools work best when you use them together. After a set, ask yourself: how many reps did I have left? How did the weight move? What was my RPE? Over time you’ll start to build an intuitive sense of what “heavy enough” actually feels like for you.
The goal isn’t to go as heavy as possible all the time. The goal is to train at an intensity that’s challenging enough to drive progress, sustainable enough to repeat week after week, and safe enough to keep you in the gym for the long haul.
SSP has six strength training locations across Seattle — Queen Anne, Phinney Ridge, West Seattle, Ballard, Mercer Island, and Wedgwood. If you’re curious about what training with a coach looks like, we offer a free introductory assessment to get you started. Learn more at seattlesp.com.