If you want a long-term cardio challenge that will force you to add some machines to your mix that you might not normally use, you can join in what my workout buddies and I just started (we made it up - it's not some big national club or anything): The Race Across America

There are 10 events, with the distance in between filled in by cardio (with various exchange rates, see below - it's not like I'm going to make you do 5000 miles of cardio). Except for event 10, none of the events or stages have to be completed in one workout.

Event 1: Hike the 4.5 mile trail out of Quoddy Head State Park (the easternmost point of the lower 48) - 4.5 miles on the treadmill at half the maximum incline (running outdoors on very hilly terrain can be substituted).

Stage 1: 557 miles from Quoddy Head to Manhattan (no, you don't have to do 557 miles - see the exchange rates below)

Event 2: Climb the Empire State Building - 117 flights of stairs on the Stairmaster

Stage 2: 220 miles from Manhattan to the Lower Potomac

Event 3: Row the lower Potomac - 90 km on the rowing machine

Stage 3: 505 miles from the Chesapeake to the Great Smoky Mountains

Event 4: Hike to the observation point at Clingman's Dome (7.5 miles on the treadmill at maximum incline with a 10 lb. weight in a backpack)

Stage 4: 448 miles from the Smokies to Memphis, TN (BBQ ribs optional)

Event 5: swim the Mississippi River - 4 miles in the pool (or open water)

Stage 5: 284 miles from Memphis to St. Louis

Event 6: Climb the Arch - 68 floors on the Stairmaster

Stage 6: 926 miles from St. Louis to the Alamo

Event 7: Survive the 13 day siege at the Alamo - 5 spin or advanced cross-training classes

Stage 7: 1228 miles from the Alamo to the Grand Canyon

Event 8: Hike into the Grand Canyon and raft down the Colorado River - walk or run 8 miles, row 32 km on the rowing machine

Stage 8: 394 miles from the Grand Canyon to Death Valley

Event 9: Hike across Death Valley to the top of Mt. Whitney - walk 10 miles on flat ground (or treadmill with no incline), five miles at half the maximum incline, and five miles at the maximum incline

State 9: 542 miles from Death Valley to Alcatraz

Event 10 (must be completed in one workout, in order): Escape from Alcatraz - 30 pullups, 2 mile run, 1 mile swim, 10 mile bike

Conversions for the stage miles are below: note that you can work on a stage while working on that event. For example, you can earn miles toward Stage 4 while working on Event 4, but you cannot earn miles toward Stage 5 until you have completed Event 4 and started Event 5. Conversions apply to stages, not events. For example, the four-mile swim for Event 5 has to be an actual four miles.

Conversions for stages:
Cross-training class: 30 miles for medium intensity, 45 for advanced
Cycling: 5 miles of credit for each mile biked
Spin Class: 150 miles for a one-hour spin class
Hiking (requires backpack): 10 miles of credit per mile hiked
Pilates/Ab training: 25 miles per class
Power Yoga: 25 miles per class
Racquetball: 25 miles per hour
Rowing machine: 30x
Running (elliptical): 10 miles of credit per mile of running
Running (track or treadmill): 15x
Running (outdoors): 20x
Swimming: 5 miles credit per 40m of swimming
Tennis: 20 miles per hour
Walking (track/machine): 5x
Walking (outdoors): 7x

There are no prizes, just the satisfaction of making it all the way to the end.