The brick workout offers many benefits for triathletes and multi discipline endurance sport athletes. As Wikipedia states: Triathletes train for this phenomenon through transition workouts known as "bricks": back-to-back workouts involving two disciplines. For most triathletes the normal brick is to combine a bike followed by run workout to simulate race conditions. I am not sure how brick derived it's name for the workout, but just assumed it was that your legs feel like they have bricks in them when you begin running immediately following a bike ride.
It is key workout form many triathletes to simulate the feeling on running with tired legs. Many of you know what the feeling is like the first mile or two during an Ironman when you fly through the transition area and head out on the run. I add different bricks to my normal training program to "mix" it up and not just do the same bike/run bricks. They all have the benefit of training the body and mind to push through when your tired.
Here are a couple different bricks compared to the normal bike/run to add some variety to your training:
Swim/Bike - this workout is an important transition that is often overlooked by many of us.
Swim 3000-4000 meters straight swim (the last 500 meters pick up the pace to be faster than race pace) get out of the water and immediately get on the Bike and ride 75 miles above (Ironman race pace)
Run/Swim - This workout is tougher than you think. Run 3-4 hours (marathon pace) on trails (carry a pair of swim googles with you) and end the run if possible at a pool/lake and swim a set of 5X500 meters at Ironman swim pace. Make sure you keep up the electrolytes as it's easy to get those nasty calf cramps in the water!
Triple Brick - This is one of my favorites to build mental strength to push through the tired legs. Bike 3 hours hard pace and immediately follow with 1000 Hindu Squats (yes your quads will feel like mush) then head out to a 2 hour run on trails. The final 30 minutes of the run do 10 hill repeats (steep and short). These final hill repeats will be brutal but if you can build up to 10 over a period of time the long term strength benefits become significant and can help when you need to push at the end of race during the run.
There are so many versions of Brick workouts and consider different varieties to keep it fun! The brick workout's benefit are immense for all endurance athletes