Why dumbbell and cable lifts stop progressing in a spreadsheet

A percentage is a share, not a weight

Your spreadsheet multiplies. That works on a heavy lift and quietly stops working on a light one, and nothing on the sheet tells you which is which.

Take a four week block. It climbs in two steps of five percentage points, from 95% of the set the client did to 105%. On a 100 kg squat each of those steps is 5 kg. On a 15 kg dumbbell curl the same two steps are 0.75 kg each, and there is no 0.75 kg jump. The smallest change you can make to that curl is a whole kilo, and most racks go up in twos.

So the multiplication is correct and the answer is unusable.

What it does to a 15 kg curl

Here are the four weeks of a 15 kg curl, straight out of the percentages, before anything is rounded:

• Week 1: 14.25 kg
• Week 2: 15 kg
• Week 3: 15.75 kg
• Week 4: 12.75 kg

Rounded, it is the same weight three times

Now round each to the nearest 2.5 kg, which is what a spreadsheet built around a barbell does:

• Week 1: 15 kg
• Week 2: 15 kg
• Week 3: 15 kg
• Week 4: 12.5 kg

The load where it starts

Three weeks at the same weight, then a lighter week. The client picks up the same dumbbell in weeks one, two and three and sees a block that does not move. The same four weeks on a 100 kg squat come out 95, 100, 105 and 85 kg, which is a block.

One step of the climb has to be at least as big as the smallest jump you can load, or it rounds away. That gives a line, and the line moves with how long the block is:

• A three week block steps 10 points at a time. Below about 10 kg it stops moving.
• A four week block steps 5 points. Below about 20 kg it stops moving.
• A five week block steps 3.33 points. Below about 30 kg.
• A six week block steps 2.5 points. Below about 40 kg.

Read it the other way

Those are worked against a 1 kg jump, the smallest change CoachBlocks will make. If the smallest dumbbell jump in your gym is 2 kg, double every number.

A longer block takes smaller steps, so a longer block needs a heavier lift before the arithmetic has anything to work with. On a 40 kg cable row, six weeks is the longest block the numbers will carry.

This is arithmetic, not coaching

It is worth being clear about whose problem this is, because it is easy to read a flat block as a programming mistake.

Nothing was mis-programmed. The percentages are the same ones that work on the squat, the rounding is the only sensible rounding, and the coach did the multiplication correctly. The lift is simply too light for a share of itself to be a loadable number. No amount of care with the spreadsheet itself fixes that, because the spreadsheet is doing exactly what it was asked.

Working in jumps instead of percentages

The way out is to stop asking for a percentage on those lifts and start asking for a jump.

A percentage answers "how much of what they did". A jump answers "what is the next thing I can actually hang on the bar". On a heavy lift the two agree. On a light lift only the second one has an answer.

Which jump belongs to which lift is yours, and it is equipment as much as anything: the dumbbells in that gym, the pin stack on that machine, whether there are micro plates in the drawer. A spreadsheet can do this, but it needs a column per lift and a different formula from the one on the squat row.

How CoachBlocks does it

Every lift carries its own step. It is the grid the weeks round to and the smallest climb the block is allowed to make, and it is a per-lift setting rather than one number for the account.

The same 15 kg curl, left on the default barbell step, comes out 15, 15, 17.5 and 12.5 kg. It climbs, but it climbs by 2.5 kg, which on a curl is a large jump.

Put it on a 1 kg step, the kilo dumbbells, and it comes out 14, 15, 16 and 13 kg. Four different weeks, each one a dumbbell that exists.

The step carries to the next block by lift name, so it is set once. What CoachBlocks will not do is pick it for you. It does not know what is on your rack.

The free program builder on this site builds four weeks from one set and lets you choose the step, so you can put a light lift through it and see both versions before changing anything.