Design a vibrant fitness promotional poster featuring a compelling black and white image of a muscular figure posing confidently, captured with a 50mm lens to highlight sharp details and depth. Utilize dramatic lighting with high contrast, employing a key light to accentuate the figure's muscles and a backlight for a striking halo effect. The subject should be posed with arms crossed or flexing, exuding strength and determination. Overlay the poster with powerful phrases like "STAY FIT NOT STILL" and "NO MORE EXCUSES, JOIN US TODAY" in bold, sans-serif typography, using bright colors such as electric blue and vibrant orange to create a striking contrast against the black and white image. Ensure the text is large and eye-catching, with a gradient or shadow effect for enhanced readability. At the bottom, leave space for a logo and website link, ensuring it is clear and unobtrusive. The overall aesthetic should be motivational and energetic, drawing viewers in and inspiring action.