References:
https://www.mayoclinic.org/healthy-lifestyle/fitness/in-depth/exercise-intensity/art-20046887
https://www.simplilearn.com/tutorials/css-tutorial/how-to-add-css-to-html
https://tenor.com/view/humanheart-beating-chambers-realistic-gif-21056658
https://gifdb.com/gif/running-cartoon-sticker-exercise-tb6rd0zslf305nzz.html
https://developer.mozilla.org/en-US/docs/Web/API/Element/innerHTML
https://www.cdc.gov/healthyweight/assessing/index.html
https://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/index.html
https://www.w3schools.com/html/html_links.asp
https://mdbootstrap.com/freebies/login-page/
https://github.com/mdbootstrap/bootstrap-5-login-cover-template/blob/main/login-cover.html
https://www.health.harvard.edu/staying-healthy/5-of-the-best-exercises-you-can-ever-do