I was used to doing running and cycling but now I want to work more on my abdominal muscles. I had read from some sources that a rowing machine is good for that. From other sources I have read otherwise.
Are rowing machines such as Concept2 useful for abdominal muscles ?
When you row, you do trunk and hip flexion, which are the ab-targeting motions of a sit-up; however, the resistance is in the opposite direction as in a sit-up. This means that you'll actually target the low back, glute muscles, and hamstrings (these muscles do hip and trunk extension--scroll down to below the "Thoracic, Lumbar" header for images). That said, according to this study, you do use your abs (rectus abdominus and obliques) at the very end of your rowing motion to slow down the trunk extension movement, so you do probably use them a little bit more than on other cardio machines. I wouldn't use it as an excuse to skip out of crunches though :)
Funnily, I stumbled over this explanation on the Concept2.com site, which they retrieved from Kinesiology of the rowing stroke by Thomas Mazzone. As you can see and Barbie also explained, the only moment you use your abs, is during the recovery. The rest of the time you use a whole lot of muscles, but mostly the extensors of your back and legs and the flexors of your arms. So no, a rowing machine is a poor way abdominal exercise.
The Catch
For more explanations, read the Concept2 page or the original article.
Actually, there is something major missing from the replies you have been given, Fred, relating to how rowing machines (as opposed to rowing with oars) affect the abdominal muscles.
It is quite natural on a rowing machine to draw the pulley baton all the way into the stomach with some momentum at the finish of the stroke, with prior flexing of the abs in order to take the fairly light impact. This flexing can be stronger depending on how much momentum you want to add to the finish. The abs then relax again as you move back into the catch position.
This abs flex built into the rowing stroke is very effective in stimulating the abs and the whole core, and so I would disagree that rowing is not an excellent way of developing the abs. Indeed, for a whole body workout, this final addition to the technique covers one of the key aims of many exercisers, to stimulate the core and abs as part of a general aerobic workout.
Indeed, in an hour of moderate rowing, you will do the moderate ab flex as many 1800 times (3 strokes per calorie, total 600 cals). Now that's a serious abs workout by any standards.
The important thing is to not overdo the momentum or to be late in timing the flex, otherwise you will end up winding yourself and perhaps even bruising your abs.
But good technique throughout the rowing stroke is necessary in order to avoid injury and get the most from the exercise.
