Fall is one of the best times of year. Cooler temps, leaves changing colors, holidays and events, good food, and football. However, the days get shorter, weather can be great, but also unpredictable, maybe kids and sports take over your weekends, and if you had a training plan, raced, or just rode your bike a lot over the summer, maybe you are experiencing a little burnout or lack of motivation. If this is you, no worries. You can still make gains, maintain (even improve) fitness, and, most importantly, still enjoy riding your bike this Fall without those 2-3+ hour rides.
How? One way is to focus on increasing your anaerobic threshold (AT).
What is AT?
AT is one of the most important benchmarks in endurance sports. It is king when it comes to endurance performance.
AT refers to the intensity (speed or power) at which the production rate of lactate in the muscle equals the clearance rate of lactate. The by-product of burning glycogen is lactate. As you increase intensity, you rely more on glycogen to produce ATP, therefore you are producing more lactate. Lactate is cleared from the bloodstream but as intensity (power/speed) increases, lactate production exceeds clearance and begins to accumulate in the blood stream. The power/speed at which lactate begins to accumulate is your AT.
AT marks the highest possible intensity, which can be sustained without accumulating lactate. In the graph to the right, you can see the lactate production (red line) and lactate concentration (yellow line) increases gradually as intensity increases, then a sudden spike at 278 watts (red arrow and circle). At intensities above 278 watts, this athlete will produce more lactate than can be cleared. This is the athlete’s AT (maximum intensity at which lactate production equals lactate clearance). Once crossing the AT, you rely more heavily on your glycolytic system for energy, and you are exercising on borrowed time. The accumulation of blood lactate will hinder your muscles’ ability to contract, and you will be forced to slow down or stop.
In other words, when you raise the intensity of an exercise and all a sudden your legs start burning, breathing becomes labored so you can’t say more than a word or 2 between breaths, heart rate ratchets up 5-10 bpm, and everything in you is saying slow down, you have just crossed your AT.
AT vs FTP: AT
AT and your functional threshold power (FTP), which is commonly defined as the highest sustainable intensity (power or heart rate) you can do for 40-60 minutes. This is a metric you can use if you do not have access to a lab for AT testing, or see below to estimate your AT with power or heart rate.
Why Increase Your AT
Increasing your AT means you will be able to ride with greater power output or speed without accumulating lactate. The more work you can do before reaching lactate threshold, the better. If the pace you can hold at your lactate threshold is higher than the pace your competitor can hold at his or her lactate threshold, you go faster, reach the finish first, and win. If racing isn’t your thing and you simply want to hang with your friends without getting dropped, whether it be the beginner ride or weekly throw down, increasing your AT get you there.
Many athletes avoid training to increase AT. It requires a focus, attention to intensity, and a little suffering. The great thing is that you can do a threshold workout fairly quick, where you get the suffering done in short intervals, adequate rest in between, and before you know it, the session is over. You can even incorporate AT work into a group ride by pushing the pace at the front or charging up a long climb. The key is steady-pacing keeping the intensity just below your AT (or right at your FTP).
Workouts geared at increasing your AT are great for Fall when time for cycling might be less and motivation wanes. Workouts can be done in just 75 minutes on a trainer, spin bike, or outdoors. Importantly, the “life balance” that cycling frequently threatens remains stable (increase cycling, gain fitness but maybe other parts of life suffer - upset significant other, less time with friends, productivity wanes, etc.).
Estimating Your AT
Don’t know your AT? No problem. Remember AT is the maximum intensity at which lactate production equals lactate clearance. It is a measurable physiological number, however it requires a testing lab, lactate reader, test protocol, and someone to administer the test.
You can estimate your AT by the following steps:
Find a mostly flat stretch of road 1.5-3 miles long (5-10k) and perform 2 maximal efforts.
Record your average power and/or heart rate.
Take your average power and/or heart rate and multiply by 0.9. Most of us average about 10% above threshold for 1.5-3mi efforts. This is your estimated AT power or heart rate.
How to Increase Your AT
For 10 weeks, incorporate a few of the following workouts to get in at least 60-100 minutes of AT work per week.
Here are some workouts that target your AT:
1. AT Intervals Just below AT, 5-20 minute intervals. The workout is less than 2 hours and would look something like the figure to the right: 20 minute warm up followed by 5X8 minute threshold intervals (for the athlete above, 8 minutes @270-290 watts) with 4 minutes rest between intervals and a 10-20 minute cool down. This is a total of 40 minutes of AT work.
If your estimated AT heart rate is 182bpm, then your target interval heart rate is 170-180 bpm, just under your estimated AT heart rate.
If you are new to this training, start with 5x5 minute intervals then increase time each week. Increase interval time and reduce interval number over the 10 week block (for example, 5x5min, 5x8min, 4x10min, 4x12min, 3x15min, 2x20min, 3x20min).
Incorporate a 20 second spike every 2-3 minutes during intervals. Vary the cadence of the spike, in the saddle and out of the saddle to help you create range at your AT.
2. Hard group rides: Attend a weekly group ride? Take part in the efforts at the front of the rotation. Instead of sitting in and drafting, push yourself, get in the rotation for as long as you can then go back and rest in the pack until you are ready to go again.
You can also train AT in a group by steady pacing up the climbs right below AT. This is great if there are a three to five 5-20 minute climbs.
3. Cyclocross race: Possibly the most entertaining way to increase your AT. Cyclocross is performed full gas at an intensity you can hold for 30 minutes to 1 hour with spikes of power to get over obstacles, slight rest periods (if you corner well), then more full gas. You train multiple energy systems during a cyclocross race and spend a good deal of time pushing your limits at AT. Plus you get the opportunity to support local racing and heckle your friends!
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