Plank Press & Sore Lower Back

I added HS2 last week and just finished my second session of it yesterday, completing PE1 Pike Pull Step 4. Since I don't have stall bars, I subbed Jeff curls with a 20lb kettlebell for PE1>iM (something I've done quite often over the past year through the Manna progressions). 

This morning, my lower back is quite sore. I've been doing Foundation One & Two for over a year now six days a week with high intensity and have progressed well. This is the first time I have had any sensation of 'pain' that might affect the quality of my workouts. 

My questions is -- is the Plank Press that different an exercise that it would cause this type of lower back pain? Anyone else awakened to DOMS as a result of starting HS2 PE1. Leigh Kettle -- I know you just started the same thing. How's your lower back feeling?

Thanks, all!

The Jefferson curl probably was the cause.

the question is: have you already mastered the JC? with how much weight? when? it is the JC on your current warm up?

Alessandro -- you are probably correct. I would say I wasn't doing a true JC curl as much as I was using the kettlebell to take me into a pike standing on a weight bench to simulate the iM. So it was a much shorter range of motion where I did four sets of five compressions. While JC isn't part of my current warm-up (I do the daily limber with the addition of several of the MS and FS stretches), I am on PE9 of Manna which I do twice a week and use 35lbs for the iM.

The pain I'm feeling now is located at the base of my spine and I'm walking like I'm about to deliver a baby! Should be OK in a day or two, but it still sucks.

Alessandro -- I just realised this may also relate to my workout from the day before. I did the mastery test for SLS SE1. While the Hawaiian Squat was quite comfortable, the Shoulder Bridge Leg Curl iM was a very different movement. Trying to replicate it now quite exacerbates my back pain -- so it may be the culprit. That or the combination of starting two new progressions on back-to-back days,

i'm happy to hear that, keep us updated!