The Benefits of Increasing Cumulative Work
As Jonathon Sullivan notes in his discussion of the work of McBride, Haines, and Kirby in The Year in Strength Science 2011, warm-up sets may (or may not) contribute to development of maximum power:
if you train to actually increase your weight on explosive lifts, won’t you also be training your 60% lifts long the way, as you warm up to your new 1RM?
So those 60% and 80% sets may be developing bar speed or simply assisting your development by increasing your training volume.
I don't worry as much about specific percentages on the way up, preferring to use readily available jumps in plates. So if your weight set is stocked, as many are, with 25s and 45s, I recommend using those instead of spending time in the weight room doing arithmetic. So for the 250 pound squat singles I did the other day, I warmed up with:
- 225x2 (more for a form check from a friend than as a warm-up)
- 250x1 several times
Note that step 4 could very well have been replaced or supplemented with 185x5. So, because I literally don't know what percent those warm-up sets were of my work sets, I'll calculate them now:
- Bar weight, as SS prescribes. This is 18% for the nerdy among ye. Note that I only did one set, though sometimes I do two, or one set of 8-10.
- 90% (though 74%--185 pounds--would've been normal for me)
- "100%", but though I was doing singles it definitely isn't my 1RM. I have no clue what my 1RM squat is, though I assume it's between 260 and, say, 290.
So though not an exact match, 36 is pretty close to 40, and 54 is pretty close to 60, and 74 is pretty close to 80. So hey!--it looks like being "lazy" with the plates worked out.
However, yes, this does mean that there are thresholds where I have to decide whether I'm going to add A Whole New Warm-Up Set. A week or so ago I had to decide to add a ~185 set, because I had been jumping from ~135 to the low 200s without an intermediate step.
If a trainee is struggling with their max sets, and is also on the threshold where they should be adding an additional warm-up set, caution may be warranted. This is where the SS method may best mine: by keeping the number of warm-up sets constant, one avoids major disruptions to what really matters, that is, your work sets.
While on Starting Strength, the goal is to maximize the success and progress of your work sets. One hears cries of Work Sets Uber Alles! and Linear progression will rescue you from the depths of weakness! and so on. That's a valid approach. If that's your method--and I've had success with it--I'd hew close to the prescribed warm-up percentages, take the increases in weight in stride, and don't worry too much about adding 5 pounds to your warm-up sets. It won't matter much.
However, I've also had success with making sure that my warm-up sets involve a little volume too. That's why I use my "add the plates that are easiest to add" method. This ensures that I get practice with the lift, and that I get plenty of training volume in even if I burn out on my work sets, or if the work sets have low volume (such as when I do high-intensity doubles or triples).
It's your call. But I wouldn't fret about the difference between warming up with 150 and 155. For instance, in the following scenario with a work weight of 205#:
40% warmup set would be 82#, round to nearest 5# plate = 80#. Next week working weight is 207.5#, 40% rounded to nearest 5# plate is 85#. 5 reps with 5# more = 25# more volume for 40% set. No big deal. But if the same rounding happened for the 60% and 80% sets, you could be doing up to 50# more volume
Fifty pounds of volume across three sets that aren't close to your work weight are nothing to worry about. The things that you should worry about is too much volume too close to your work sets. For example, a set of 5 at 190 might be too much for that work weight of 205. So might five sets of 135. But adding five pounds to each warm-up set? You'll be able to handle it.