The brick exercise, often known as a bike-run or swim-bike workout, may be done in a variety of ways (or any combination). What are the benefits of this training for triathletes?
You’ll probably hear ten different responses if you ask ten triathletes why a brisk exercise is termed a “brick.” Another, more straightforward explanation: When blogging about his bike-run and run-bike workouts while preparing for a duathlon, Dr. Matt Brick invented the phrase. Regardless of why it’s termed a brick, this back-to-back combination exercise is quite effective. While the bike-run, also known as a run-off-the-bike (ROTB), is the most popular brick exercise for triathletes, a brick may also include a run-bike-run or even a swim-bike. Many triathletes use brick training to accustom their legs to the shaky sensation that comes when they get off the bike and begin to run. However, it’s a fantastic opportunity to work on race simulation efforts, nutrition, and transitions.
Source: https://www.triathlete.com/training/get-to-know-the-brick-workout/