What Muscles are Actually Firing??

I’m a research guy. 
To me, well done research trumps anecdotal gym “bro science” any day. 
Show me some evidence in the form of good research, and I’m willing to test it in the lab (aka the Emerge workout floor) to see if it sticks in a real-world test. 
One of the most interesting research topics (for me at least) are the studies using EMG machines to measure the electrical impulses of muscle. (During rest and contraction). 
Basically, in these studies the EMG is recording what muscles are firing and to what extent. 
Here is a list of a few common exercises with the EMG activity (a summary) of the primary muscles involved. Of note is that many of these are considered “ab” exercises. It is important to minimize the recruitment of the hip flexors (especially the psoas) when attempting to train these muscles. The hip flexors are normally already short, over recruited muscles that, for 90% of people, need no extra work…
1) Side plank- 
Works the side of the hip (glute medius) as much or MORE than its works the abs and obliques. 
Glute Medius = Core 
2) Bent knee sit ups-
Works the hip flexors (psoas) equally to the abs. 
Hip Flexors = Core
3) Straight leg raises-
Works the hip flexors TWICE as much as it does the abs. 
As a matter of fact, a PUSH UP from the toes activates the abs almost equally to the straight leg raise. 
Hip Flexors > Abdominals
4) Bent knee curl up (crunch)-
Activates the abs SIX times as much as the hip flexors, and more so than the sit up. 
Abdominals > Hip Flexors
5) Dead Lift- 
a moderately loaded deadlift (150-250 pounds) activates the obliques, abdominals, and hip flexors equally (and at a relatively low level). The erector muscles of the back are activated SIX times as much. 
Spinal Erectors > Abdominals
These are just a few examples, and there are many more (many were a big surprise to me!)
I’ll be doing a brief article every week based on current evidence/research in the fitness field. 
It’s Your Turn. Emerge. 
Matt Pirtle MA CSCS