The program says 100 kg for three sets of five. You walk in after four hours of sleep and a long day. The program still says 100 kg.
Most of us lift it anyway, grind through it, and call it discipline. Sometimes that is right. Sometimes it just means the day you were flat turns into a week you are sore.
There is a simpler way to decide. Your warm-ups already tell you how the day is going. You only need to measure one of them.
The idea
At a weight you know well, your bar speed is fairly steady from week to week. On a good day the bar moves a bit faster than usual. On a flat day it moves slower.
So pick one warm-up weight, measure how fast you move it every session, and let that number nudge the working weight up, keep it where it is, or bring it down.
You are not chasing a perfect formula. You are comparing you today with you on a normal day.
Pick your check weight
Choose one weight from your normal warm-up, heavy enough to mean something but light enough that it never tires you. For a squat with a 100 kg working weight, something around 70 kg works.
Use the same weight every session for that lift. If the check weight changes, the comparison is gone.
Film it the same way every time
Prop the phone side-on at bar height, still, with the plates and the whole bar path in frame. Do not hold it. Film the set in the SpeedTrackr Android app, or film it with the normal camera and import the clip afterwards. The app then gives bar speed for every rep in m/s.
For squats, bench and deadlifts, read the mean speed. Two or three reps is enough. Do them with the same intent every time: controlled down, as fast as you can up.
Build your normal
For the first two or three sessions, just record. Do not change anything yet. The first set at a new weight is shown as the baseline to beat, which is exactly what you want here: a number that says what normal looks like for you at that weight.
After a few sessions you will have a rough normal range. Write it down. For example, 70 kg usually moves somewhere around the same speed, give or take a little.
Read it before the working sets
Now each session you do the check set and look at the best mean speed.
Faster than your usual range: today is a good day. Do the planned weight, and if the plan allows it, add a small jump.
Inside your usual range: do what the program says.
Clearly slower than your usual range: keep the plan's sets and reps but take some weight off, or cut a set. Do not test a max.
The rule I use is to change the load in small steps and only when the speed is clearly outside the normal range. One slightly slow rep is not a bad day. A whole check set well below normal usually is.
Pair it with the set itself
The check set tells you where to start. During the working sets, the speed of the reps tells you when to stop. If the bar slows a lot inside a set, that set is done, even if there are reps left on the plan.
Together they replace a lot of guessing with two simple questions: how fast did the warm-up move, and how much did the set slow down?
Keep it comparable
Same lift, same check weight, same depth or range of motion, same camera spot. Do the check set at the same point in your warm-up, not after something else has already tired you.
If you coach a group, turn on Coach Mode and pick the athlete before each set, so every check set lands on the right athlete's page. Coach Mode works in the Android app and on the web app. Each athlete gets their own normal range, because their check weights and speeds are their own.
One last thing. This is a phone filming a bar, read from video. It is a practical way to compare an athlete with themselves on the same setup, which is all you need to decide whether today is a push day or a hold day.
The Android app is on Google Play: https://play.google.com/store/apps/details?id=com.speedtrackr.reactionpro
On an iPhone or a laptop, use the web app: https://www.speedtrackr.com/auth/login
