Your goal is to use a weight that is light enough for you to complete the number of reps you are trying for that exercise, but heavy enough so that you couldn’t do additional reps.
In terms of, when you should increase the weight. When you can do 2 more reps with a given weight than you started out with, for two consecutive workouts, then increase. 💪🏽
More in-depth
There's a term called technical failure where you stop once you're unable to perform more reps without sacrificing your technique and form. For 99% of people this is a good method to practice. Helping your progressively increase your performance while lowering the risk of over doing it.
Why do we not tell you what you should be able to lift?
The reality is, what you can lift on the day is dependent upon many factors. Generally you can achieve your last lifted weight but perhaps you’re more dehydrated that day (or any number of factors) that would mean you may lift less. Ultimately it’s a reminder and a figure to try and beat. Intensity and consistency will matter more.
Any time an exercise is empty it is because you have not previously logged a weight for that exact exercise. We do increase/decrease last lifts if the rep ranges change, based on your previous lifts. That again is not an exact science, more of a guide based on direct knowledge of your performance.
Any app that thinks it knows what you can lift we would be very dubious of. It’s rarely linear and rarely transferable exercise to exercise and person to person. You may have a strong machine chest press but significantly less with flat bench. Certain angles and movement patterns you may favour over others.
If you continually try to beat your last lifts either with more weight or reps (with good form) and particularly more focus and intensity on ‘really’ feeling that you’re working the target muscle. You’ll progress at a solid pace.
An example of what I do
I use the last lift as a baseline to work with.
As I work through the sets, let’s say the last few reps aren’t challenging me… I keep going, doing more reps until I’m at technical failure. Then on the next set I increase the weight and try hit the preset reps at my new personal best.
Often on the last set I end up back at the initial weight due to fatigue and not wanting to sacrifice the technique just to hit a poor rep at a higher weight.
Over time, your old last lift increases and the cycle continues until you peak. Then you ride the bottom of the rollercoaster for a period, giving everything you’ve got at your new max weight.
No swinging, slow eccentric, momentary hold on the stretch. It’s beautiful and feels amazing 😅💪
Happy training!