Training Notes: What Is 'Anaerobic Threshold' and Why Are Zones Important In Training?

There tends to be two types of training mindsets that I have seen.  First you have the "put in time every day at the go pace" - these are the people that crank out hours and hours of work at the same effort,on the same routes, same distances, same result.  Then there are the people who train by purpose of the workout and are versed in terms like threshold, tempo, long and steady, speedwork/fartlek, cadence/turnover and drill focused efforts.

Many people naturally gravitate toward the more moderate-intensity cardio sessions under the assumption that they’re working hard enough to see results. Gym-goers, runners, cyclists alike tend to find this mid-range effort the sweet spot that they stay in. The truth is that you’re probably not getting the most out of your workout if you’re not monitoring your heart rate and considering your anaerobic threshold (AT) or Lactic Threshold Heart Rate (LTHR), the point at which your body shifts from aerobic to anaerobic activity and starts burning primarily carbs as fuel. As a coach and mentor I like to meet my clients where they are. If they are starting out in their fitness journey then we go for total active time with a focus on consistency.  No matter the level of athletic ability and desire, consistency is key for growth and injury prevention. You absolutely can be successful training for an event by focusing on putting in the time however where you spend the time is important. 

We want to make every effort count and we do that via identifying your AT and creating your workout zones. 

ASSESSMENT OF BASELINE

The most accurate way to determine your AT/LTHR requires a heart-rate monitor and professional assistance (like the assessments available at many health clubs). Lifetime Fitness offers different Aerobic Metabolic Assessments that do this very efficiently and run about $175 out the door for the test and the mask. If that’s not in your budget, then a do-it-yourself method can provide a good estimate — and help you get closer to meeting your fitness goals. 

ESTIMATE OF AT/LTHR WITH HEART RATE MONITOR

To find your AT/LTHR, I have my clients use Joe Friel's method by doing an all our time trial.  The process is easy even if you have never done anything like this before. You do a 30-minute time trial all by yourself (no training partners and not in a race). It should be done as if it was a race for the entire 30 minutes but at 10 minutes into the test, click the lap button on your heart rate monitor. When done, look to see what your average heart rate was for the last 20 minutes. That number is an approximation of your AT/LTHR.


CALCULATING THE ZONES

In order to determine your training zones, take the % and multiple by your LTHR.  The below zones represent different physiological markers for the energy systems and for exercise intensity. It is also key to note that your Zones will be different based on sport so I have included the two most popular types of cardio for reference - standing exercises such as running, skiing and elliptial, and then sitting exercises such as cycling, rowing, etc.  

For activities where you are on your feet (running, elliptical, skiing, etc.)

• Zone 1 Less than 85% of LTHR
• Zone 2 85% to 89% of LTHR
• Zone 3 90% to 94% of LTHR
• Zone 4 95% to 99% of LTHR
• Zone 5 100% to 102% of LTHR
• Zone 6 103% to 106% of LTHR
• Zone 7 More than 106% of LTHR

For activities where you are sitting (bike, row machine)

• Zone 1 Less than 81% of LTHR
• Zone 2 81% to 89% of LTHR
• Zone 3 90% to 93% of LTHR
• Zone 4 94% to 99% of LTHR
• Zone 5 100% to 102% of LTHR
• Zone 6 103% to 106% of LTHR
• Zone 7 More than 106% of LTHR
  
  

For example, if your AT/LTHR is estimated at 150 BPM, then your running zones would look like this:

• Zone 1 Less than 127BPM
• Zone 2  127 to 133 BPM
• Zone 3 134 to 141 BPM
• Zone 4 141 to 149 BPM
• Zone 5 150 to 153 BPM 
• Zone 6 153 to 159 BPM
• Zone 7 More than 159 BPM

EXPLANATION OF THE ZONES​

Zone 1: Recovery Zone (Aerobic Threshold or Lactate Threshold)

Zone 1 is the exercise intensity at which anaerobic energy pathways start to operate. Zone 1 is primarily used for light recovery workouts (increasing blood flow to muscles to improve recovery from previous hard training sessions). It can also be used as a guide while warming up or for cooling down.


Zone 2: Aerobic Base 1

Zone 2 is the primary exercise intensity for long duration events (8-12 hours in duration). Training in Zone 2 increases aerobic capacity, fatty acid oxidation, and recruitment of Type IIa muscle fibers for aerobic function. 


Zone 3: Aerobic Base 2

Zone 3 is the primary exercise intensity for events lasting 3-8 hours in duration. The physiological benefits for Zone 3 training is similar to Zone 2 but recovery time is often greater.


Zone 4: Sub-Anaerobic Threshold

For events lasting 1-3 hours in duration Zone 4 is the primary training zone. Training in this zone increases muscular endurance.


Zone 5: Anaerobic Threshold (Lactate Threshold 2)

This is the zone where an athlete will begin to "redline".  It will be the primary intensity in events lasting 20-60 minutes in duration. Training volume above this effort level will be limited due to increased acidosis, however will improve the body’s buffering ability and clearance of lactate. This in turn will increase the Anaerobic Threshold


Zone 6: Aerobic Capacity

This zone is primarily trained using intervals (short periods of high intensity typically followed by rest periods of equal or greater length) and is great for increasing VO2 max, the body's ability to uptake oxygen into the bloodstream. 


Zone 7: Maximal Anaerobic Capacity

Zone 7 is at or near maximum effort. Like Zone 6 it is trained using intervals and is great for increasing both VO2 max and AT. Because intensity is at or near maximum effort, the duration of intervals at this zone is very short. Here heart rate is not a good indicator of Zone 7 training and your Rate of Perceived Exertion (RPE) is preferred. 

TRAINING WITH YOUR ZONES

Each zone has its purpose and place in training however not all zones are to be trained in at all times.  A bulk of training should be in the Zones 2 and 3, with the use of Zone 1 for warm ups and recoveries.  Going into Zones 5-7 are key for increasing the base line, and should be used with specific purpose and timing based on desired goals and place in the training plan. 

Popular High Intensity Interval Training (HIIT) programs and classes such as Orange Theory are based around working out in varying zones and are a good model of showing how adding some intensity with purpose can result in major growth in fitness and performance.  

But what if I am not ready for intensity?  That is fine!  You can use knowledge of your AT/LTHR to help you in your "putting the time in" workouts too!  A good general rule is to try to stay below your AT/LTHR for 80% of each workout to burn fat, and just above it for 20% of the time to improve fitness. 

Retest every six to eight weeks to maintain an accurate measurement. Your AT/LTHR is a highly individualized number; it will decline as you age and change based on your overall fitness level at any given time.

Happy Training!