Tucked away in a corner building on Northwest Mulholland Drive in Roseburg is a small, unassuming gym regularly visited by about 100 seniors. They aren’t there to become thin, hard-bodied workout enthusiasts. Some of them have suffered serious falls or hope to prevent them. Others have had heart attacks or surgeries and are improving their strength and cardiac health. The Active Life Fitness Center, where these seniors gather, has its own challenges. The center is struggling financially and in danger of having to close its doors. Manager Holly Locke said she hopes the gym will survive because it provides a …