Paddling specify exercises
“Paddling is part of a unique group of sports (including swimming, rock climbing, and cross-country skiing) that require unique and unnatural movements. Consequently, only a limited amount of non-specific training will enhance performance and as athletes become more experienced, the benefits of non-specific training are greatly diminished. Thus, the specificity of fitness training increases in importance for the moreexperienced and elite athletes.”
Taken from Eacoaching.
In other words, the best way for experienced paddlers to improve is to paddle more.