I doubt one year of indoor rowing would cause much of a difference. I suspect in most cases it is the result of years of increased pressure on the aorta over time. In my case, in addition to intense exercise over a few decades, I have worked at a stressful job with long hours for over 25 years. Since being diagnosed, I have noticed that my blood pressure will go up when things get intense at work and/or when I am fatigued at the end of a long day.