Your doctors would be able to answer your question concerning health much better than me. But higher water retention goes hand in hand with higher blood pressure logically. On your original question, I was trying to think back to what I knew from physiology, water/mineral, mineral-corticoids etc, and ions (Na+) role in activation of the nervous system (extracellular fluid). Cannot think of Na+ direct role in strength or muscle mass, other than deficiency would lead to possible lowered physical performance during exercise.