The phrase "building strength" means that someone is taking actions or making efforts to become physically, emotionally, or mentally stronger. Full definition
The truth of the matter is that ab exercises are great for building strength in the abdomen. (fitnessandpower.com)
The warrior poses are perfect for building strength in the body and empowering the spirit to tackle whatever may come your way during the day! (fitbodyhq.com)
This helps build strength in the chest and shoulder muscles. (bounty.com)