In order to effectively train to failure when doing cardio work, you need to define what it means to fail. While collapsing into unconsciousness is certainly failure, it probably isn't wise to allow this to be the only way you assess whether or not you've worked hard enough. We need some other metric--or measure of performance--to how hard we're working.

One common way to measure intensity is by using the RPE scale. RPE stands for 'rated perceived exertion' and is a subjective measure of how hard you're working. The scale runs from 0 (doing nothing at all) to 10 (working very, very hard) and some training programs (and many group fitness classes) will use it to prescribe intensity: "this next interval you should be working at an 8, people!" The problem with the RPE is that it really only tells you how hard you feel like you're working, not how hard you actually are working. This method of assessment lacks the consistency and objectivity to really be useful.

Objective metrics allow for a clear definition of what failure means for a given workout. They provide a limited amount of accountability and also allows for tracking performance between workouts. It's true that a slippery slope still exists in the sense that you can fail under the given metric without actually being very close to your limit, but bringing some objectivity to the process is better than having none at all. An objective metric is also important in that it serves as the load which you adjust as your fitness improves to ensure continued progress.

Again the specific choice of an objective metric is up to you--while various workouts and environments might favor different metrics, most of the time the decision will be based on preference. As long as the metric is able to be manipulated in isolation as you improve, it is suitable. Here are some objective metrics for common training disciplines:

• Running (treadmill)
  
  • Pace for time
  • Pace for distance
  • Incline at given pace (for distance or time)
• Running (outdoor)
  • Time for set distance, with certain rest interval
  • Set distance in certain time, with set rest interval (400 meters in 90 sec)
• Biking (indoor)
  • Wattage (can be used outdoor too with a power meter)
  • RPM at a certain level (holding 90 RPM at a certain level)
• Biking (outdoor)
  • Distance in set time
  • Time to certain distance
  • Strava or similar (see user tip below!)
• Swimming
  • Time for distance, with set rest interval
  • lengths per time (for longer time intervals)
• Rowing (indoor)
  • time (pace) for 500 meters [Concept rowers]
  • time to distance or distance per time
• Other indoor cardio equipment: level for set program

Objective assessment metrics won't always need to be used. Sometimes you'll just to go out for a time trial type effort--a good hard run or bike. But you will need to use them often as they form the basis for 'Baseline Workouts' (BW), which are a key component to One Hour Series training protocols. We'll cover Baseline Workouts on the next page.