reckoner
Push, pull, legs. Three sessions between them cover every muscle you have, and you run them once through the week if you have three days and twice if you have six. It is the split most people mean when they say they are running a program, and the version written down most often is the six day one.
The case usually made for it is about recovery. Your pushing muscles rest while you pull, your pulling muscles rest while you squat, so nothing is asked to work hard two days running. That is a tidy story and it is not wrong. It is also not what makes the split work, and knowing what does tells you which version of it you should be running.
What choosing a split actually decides
Less than the argument about splits would suggest. A systematic review compared split routines against full body training across 14 studies and 392 people, with weekly sets matched between them, and found no meaningful difference in bench press strength, lower body strength, arm or thigh size, or lean body mass. Its own conclusion is that you can pick a routine on preference1.
The 2026 American College of Sports Medicine position stand arrives in the same place from the other direction. Reviewing the whole literature, it reports that muscle growth was not affected by training a muscle once a week against more than five times a week, once total weekly volume was equal2.
So the split is not the stimulus. The hard sets are the stimulus. The split is how you fit them into the days you actually have, and that is a real job rather than a small one.
Six days is a schedule, not a dose
Run push, pull and legs twice and every muscle you own gets two sessions a week. That is the frequency the position stand recommends outright: high effort training at least twice a week with every major muscle group involved2.
What the sixth day does not do is add stimulus by existing. Grgic and colleagues pooled 22 studies and found strength gains climbing with each extra training day, then looked only at the studies that held weekly volume equal and found the effect gone. Their reading is the useful one: train more often in order to do more work, because the work is what pays3.
Which gives you the test for your own sixth day. If it is where extra hard sets go, it is earning its place. If you took the same sets and spread them thinner, you added a commute and a warm-up and nothing else.
A split does not train you. It decides where the sets go, and the sets do the training.
Three days of push pull legs trains you once a week
The three day version is the same three sessions run once, which means every muscle you have is trained once a week. That is fine for size, on the evidence above, provided the weekly sets are all there. It is the weaker choice for strength, because frequency is one of the few variables that moves the strength answer at all2.
If three days is what you have, an upper/lower rotation or full body training reaches every muscle two or three times inside the same three sessions. You are not giving up the split so much as taking the frequency that three days can afford.
What goes wrong on push pull legs
Leg day is the one that gets missed, and on a six day week missing one leg session halves your leg training for that week while your chest keeps both of its sessions. Over a few months that is not a small asymmetry. It is the shape of most people who have run this split for a year.
The second thing is the arms. Your triceps work on every pressing set and your biceps work on every row, so both are already trained twice a week before a single curl. Isolation work is worth doing. It is worth doing knowing that it is the second helping rather than the first.
The third is order inside the session. The position stand finds that strength improves more when a lift is done at the start of a session rather than at the end2. On a push day that means the press you care about goes first, while you are fresh, and the lateral raises wait.
How to run it
- Pick the version your week can actually hold. Six days that you attend beats six days that become four with the legs missing. Four days of upper and lower is a real answer here rather than a consolation.
- Put the lift you care about first. One heavy movement per session, done while you are fresh, then the volume work behind it.
- Count sets per muscle across the week, not per session. That is the number the evidence is about, and it is the number a split moves around.
- Protect leg day. If a week has to lose a session, lose a push or a pull day, because the legs are the ones already carrying two sessions against your upper body's four.
What Reckoner does with it
Reckoner does not ask you to choose a split. It asks how many days a week you can train and which days those are, then lays the week out from that answer: fewer days means each session covers more of you, and a push, pull and legs rotation is what the top of the range gets. You can also name what you want on a given day, push, pull, legs, full body or rest, and if your goal has no such day it says so rather than quietly giving you something else.
What it does after that is the part a split cannot do. It reads what you actually lifted, set by set, applies a progression rule to each lift on its own evidence, and writes next week from the result. So the sets you missed on the second leg day are visible as missed sets rather than averaged into a good week, and the rules that decide what happens next are published rather than hidden.
Pick the split you will show up for, then stop thinking about it. The interesting question was never push pull legs against upper lower. It is whether the sets got done.