The posterior chain is the driving force behind power in the stroke.
The chain is comprised of the primary muscles of the back including the lower back, glutes, hamstrings, and calves.
A weakness in the chain leads to the smaller muscles over compensating for poor movement patterns and ultimately lower back ache when paddling. So before you change your technique or paddle length ensure your engine is firing on all cylinders. 

Being able to recruit the right muscles are all important. If larger muscles don’t fire ( such as the glutes and hip flexors) the smaller muscles take up the slack and lead to problems further down the road so if you spend hours behind a desk or lack mobility in your hips ( another blog altogether) assessing  proper form and then recruiting the right muscles will help.