Re: Question about rowing
1. Yes. High intensity is the way to make faster adaptations.
Why do you think a lot of the good/elite CFers can put up sub 1:30 and even sub 1:20 times in 500m row with very little directly C2 rowing AND poor technique.
TBH, you need to train both though. The elite marathons DO their distance work, but they also focus on intervals and sprints too. Running ~4:10 minute miles for 26 miles is no joke. You gotta have the speed too.
2. No, it's not a core violation.
The power from your legs is transmitted through your core (lower back, abdominal, lumbar area) to the arms which are holding onto the thing you are rowing with.
The main job of the core here is to resist the forces that is exerted on the top half the of the body and the lower half of the body. Your arms are being pulled towards the rower and your legs are pushing away from the rower.. your core resists the arms so that you move backwards pulling the chain away from the rower more.
This is similar to swinging sports such as baseball and golf where the HIPS are generating all of the power, and the core is resisting the action/reaction from contact with the ball.