# Predicted 1RM accuracy

In how far is a predicted one repetition maximum (1RM) accurate if there are several seconds between reps?

For example using this website.

Example: Let's say I do 10 x 150kg on the deadlift with average rep time of 9 sec (time from first rep to last pull divided by reps).

Is there a formula that takes rep time into account? If not, which rep time is acceptable between repetitions to call it a set / so the predicted 1RM works?

• i would suggest the tags: "theory" and "1RM" or "one-rep-max" Commented Oct 20, 2015 at 13:30

## 1 Answer

First of all, the accuracy of 1RM calculators is never going to be exact. A 1RM is inherently unpredictable. To my knowledge they are not rigorously tested against different pseudo-rest periods between reps in a set.

I sometimes take several breaths between reps of a squat. The bar is still on my shoulders, though, so it's still a set. In a high-rep context (for which 1RM calculators already become inaccurate) like towards the end of a heavy 20-rep squat workout, I might take five or six fast breaths. In a deadlift, it's normal to take a breath or two and reset one's grip between reps and still call it a set.

An average of 9 seconds between reps for a 10-rep set is pretty far into territory that I would consider not a set in the normal sense. But the distinction is extremely vague, especially for exercises where you're still holding the bar. For a deadlift, where those pauses between reps are complete rest, I'd say they firmly don't count as a set and are more like a cluster of singles.

• I might be wrong, but I think he meant the entire set of 10 reps takes 9 seconds. Commented Oct 20, 2015 at 21:18
• @AlexL I wondered that, but OP defined it as "time from first rep to last pull divided by reps" and 150kg is exactly the spot where a lot of people start saying "HOLY HELL THIS IS HEAVY" and taking a looooong time between reps Commented Oct 20, 2015 at 21:50
• it is not exaclty the time between reps. it is the avg time from one pull to the other (so pulling time itself is included). the drop is included as well, although to short to consider, I think. Commented Oct 21, 2015 at 8:19
• @haywire Whoops, I missed that. It's still on the long side, which is to be expected for a 10RM effort, but it's in the realm of reasonable. I will say that a 10RM attempt has a lot of variance in predicting a 1RM attempt, but 6-7 seconds between reps in the deadlift is a bit long but reasonable to consider a set. Commented Oct 21, 2015 at 8:43
• @DaveLiepmann: My next question, i case you are interested: fitness.stackexchange.com/questions/27748/… Commented Oct 21, 2015 at 10:33