Maintaining a constantheart rate and power output is key to unleashing your perfect race.
Aerobic endurance is the most basic physical ability required to prepare for a long distance event. The next most important is muscular endurance, which is built on an aerobic endurance foundation.
Aerobic endurance fitness is the ability to maintain a steady effort for hours at a time with minimal fatigue. This means working below your anaerobic threshold. When your aerobic endurance is exceeded and fatigue sets in then one of two situations develops:
* either your heart rate begins to drift up (cardiac drift) as you maintain speed/power
* or your power output (on the bike) or speed (on the run) drifts down at a steady hr
In fact, both your heart rate and output can be affected. When aerobic endurance is at a competent level, both of these markers of fatigue remain relatively stable, with no upward or downward drifting for several hours. However the opposite is also true and if you don’t develop the most basic element of fitness – aerobic endurance – then power output or speed slowly descends even though heart rate remains relatively stable. This is known as ‘aerobic decoupling’.
An excessive amount of decoupling when riding or running steadily at your goal race effort is a sure sign of inadequate aerobic endurance. So what is an excessive amount? This is a little subjective but it is generally considered to be more than 5%
Watts and HR
The graphs below illustrate examples of heart rate and power variation over a 4hr steady-state bike ride.
The first example shows an athlete with reduced aerobic endurance resulting in 11.5% decoupling.
The second graphs shows an athlete with good aerobic endurance, shown by the minimal deviation in heart rate and power output over the first half compared to the second.
Work it out
Begin by finding your average heart rate and power or speed for each half of your workout.
Then figure out the ratio between the two. To do this, divide the average bike power or run speed by the average heart rate for each half. Subtract the second half quotient from the first half quotient and divide the answer by the first half quotient.
The result is your percentage of decoupling.
Now yes this sounds complicated to work out but it’s really not – just follow the example at the bottom of the graphs
Be aware that your aerobic fitness is specific to a given duration. So you may remain coupled for 2hrs at race effort, but beyond that begin to decouple. This demonstrates that you have only about 120mins of race-specific aerobic fitness, which is fine if you race Olympic-distance or shorter but inadequate for Ironman distance.
Iron-distance competitors should decouple no more than 5% for four hours while riding at goal effort and for two hours of race-like running. When this is achieved your aerobic endurance is well established.
Output-to-input ratio
Another way of gauging aerobic endurance progress is to compare your long workout output (bike power or run speed) with your workout input (heart rate). Dividing output by input also tells you how you’re progressing aerobically.
It’s simple maths. Just look at your power meter to see what your average power was for a steady ride at goal pace. Divide that by your average heart rate and you have the ratio. The same can be done for running by finding your average speed and dividing it by your average heart rate.
Do this for each of your long, race-like aerobic endurance rides and runs, and note the ratios in your training log. You should notice that the ratios become higher. Of course, there will be times when the ratio goes in the wrong direction. That’s to be expected for many reasons but the trend over several weeks should be upward.
Keep tabs
It’s a good idea to monitor both of these aerobic endurance tools throughout your training sessions – regardless of what part of the season you’re in – and it’s especially important when undertaking goal-intensity targeted workouts or race pace workouts.
As for sessions to improve your aerobic endurance:-
At least six long, aerobic endurance workouts in each sport, in an eight-week period prior to peaking for the race, even if you have minimal decoupling and your output-to-input ratio improves significantly sooner than that.
These workouts may be part of a combined bike/run session. For the bike-focused effort, warm up for 10mins or so as you build to your long-course power or heart-rate goal. Ride for up to 4hrs. Finish with a run of about 15mins at your planned race pace.
Adapted from an article by Debbie Graham
Comments