Zone 1 Endurance Training On Shoshone Route, Grand Canyon Natilonal Park

The primary goal for endurance athletes is to be able to exercise at low to moderate intensities for hours at a time. Endurance training requires that the majority of the training be done in the Endurance Zone (below the aerobic threshold (AeT). At this intensity, fat metabolism provides more than half of the energy needed for movement. The body metabolizes fat stores for an almost unlimited supply of energy and processes lactate faster than it is produced. The lower intensity training also reduces the stress to the musculoskeletal system so that you can train more often. Another important aspect of Endurance Zone training is that it raises the aerobic threshold over time. This allows training at higher intensities for longer times while still using fat as a primary energy source and processing lactate faster than it is produced.

Keeping Intensity In Check With A Heart Rate Monitor

I highly recommend beginning athletes train with a chest strap heart rate monitor to keep Endurance Zone workouts below the aerobic threshold (it is very easy to drift above the AeT into the Threshold Zone without a monitor!). The Wahoo Tickr with the Wahoo fitness app is the one I use. One of the best features is the ability to download your workout directly to Training Peaks with a single push of the button on the app. To get your target heart rates for Endurance Zone, the MAF 180-age formula is a good way to conservatively estimate the upper end of the Endurance Zone. More information on this: Estimating Aerobic Threshold MAF 180 Formula.

Stay In The Zone With The Talk Test

When training in the Endurance Zone, you should be able to speak comfortably. The ability to speak in full sentences, recite the alphabet, speak for 10 seconds is considered comfortable. This is often referred to as “conversational pace”. As long as you can speak comfortably, you are almost definitely below the aerobic threshold. As you approach the upper end of  the Endurance Zone and the aerobic threshold, talking in complete sentences becomes more challenging. 

Assessing Endurance Zone With Nose Breathing

A good way to quickly assess that you are training below your aerobic threshold in the backcountry is the ability to breathe through your nose. If you are below the aerobic threshold, you should be able to easily breathe through your nose. As intensity approaches the upper end of the Endurance Zone and the aerobic threshold, nose breathing becomes deep and steady.

Endurance Zone training should make up the majority of your training volume (80+% of training time) if your goal is any activity lasting multiple hours. Next weeks article will discuss the Aerobic Threshold in detail.  If you have any questions, please send me an email at james@adventureperformancetraining.com.

Ventilatory Threshold And Training Intensity

Ventilatory Threshold And Training Intensity

Ventilatory threshold is a great tool for estimating training intensity in the field. The Talk Test was first used by Professor John Grayson of Oxford University in 1939. The talk test was used to advise English mountaineers to “climb no faster than you can talk”. In more recent times, it is referred to as “conversation pace”. Recent research has found a close correlation exists between the ability speak and training intensity.

Below Ventilatory Threshold 1 (<VT1)

Below VT1, the majority of energy production comes from fat and lactate is easily metabolized. The ability to speak comfortably and carry on a conversation is a good way to assess if you are below VT1/aerobic threshold in training and in the mountains. The ability to speak in full sentences, recite the alphabet or speak for 10 seconds is considered comfortable. As you approach the aerobic threshold/VT1, talking in complete sentences will become more challenging.

Ventilatory Threshold 1 (VT1)

Ventilatory Threshold 1 is the point at which ventilation starts to increase in a non-linear fashion. It is the point of transition where the body is using more carbohydrates than fat for energy production. It is also the point at which lactate is produced faster than it can be cleared by the body. At Ventilatory Threshold 1, continuous talking is no longer comfortable. Conversation will become limited to a few words at a time to short sentences. Training at VT1 is approximately the highest intensity that can be sustained for one to two hours of exercise in well trained athletes.

Ventilatory Threshold 2 (VT2)

VT2 is a close approximation to OBLA (onset of blood lactate accumulation). OBLA is the point that blood lactate accumulates faster than the body can metabolize it. Talking at VT2 will be limited to a few words. Training at VT2 is approximately the highest intensity that can be sustained for 30-60 minutes in well trained individuals.

Above Ventilatory Threshold 2 (>VT2)

Exercise above VT2 is very high intensity training. Above VT2, talking is almost impossible. Exercise above VT2 can be sustained for 30 seconds to a few minutes (in elite athletes) due to an accumulation of blood lactate. The higher the intensity you train at above VT2, the shorter the amount of time you can sustain that intensity.

Ventilatory thresholds are a powerful tool for endurance athletes to quickly assess training intensity in the field. Knowing if your pace is sustainable for seconds, minutes or hours is crucial to success on an all day or multi-day endurance effort in the mountains.


Estimating Aerobic Threshold MAF 180 Formula

estimating aerobic threshold

Every endurance athlete should know what the aerobic threshold is and spend most of their training time below that threshold. One way to measure intensity is with a heart rate monitor. Estimating Aerobic Threshold (AeT) using the MAF (Maximum Aerobic Function) 180 Formula will give you a conservative threshold heart rate. The MAF Formula was extensively researched and developed by Dr. Phil Maffetone in the early 1980s. Unlike the popular 220-age formula, it takes health and fitness factors into account.

Estimating Aerobic Threshold using the MAF 180 formula has two easy steps.

Step 1: Subtract your age from 180.

Step 2: Modify the number from Step 1 based on health and training history.

  • If you have or are recovering from a major illness/injury (heart disease, any operation or hospital stay, etc.) or are on any regular medication, subtract 10.
  • If you are injured, have a medical condition, get two or more colds or flus per year, have allergies or asthma, or are just getting back into consistent endurance training, subtract 5.
  • If you have trained consistently (at least 4 times per week) for up to two years without any of the problems above, keep the number the same (180 minus your age).
  • If you have trained for more than two years without any of the problems listed above and have progressed without injury, add 5.

Take the number obtained in Step 2 and use that as the upper limit heart rate for aerobic training.


45 year old athlete who is just getting back into endurance training.


For the athlete in the example above, training within a heart rate range of 10-15% of 130 (13-20 beats or 110-130) will give a good estimate to stay in the aerobic zone. This will build endurance and keep the intensity low enough to train/exercise more often while reducing the chance of injury.

Next weeks article will go into how to assess if you are below your aerobic threshold using the talk test. This test doesn’t require a heart rate monitor and is an effective way to check your intensity when you are in the backcountry.


Signs Of Heat Illness

The author well into the upper limits of heat exhaustion. Only 100 in the shade.
The author well into the upper limits of heat exhaustion. Only 100 in the shade.

Knowing the early signs of heat illness and taking action can help prevent the progression to life threatening conditions. If you push a little too hard, don’t eat or drink enough or just pushed the envelope on the time of day you trained, I have listed below some of the common heat related illnesses and initial treatments for each.

Heat Cramps

Heat cramps are an early indication that you are exercising at an intensity that you are not adapted to for the temperature. Symptoms of heat cramps are cramping in the muscle groups used during exercise. Treatment for heat cramps includes: remove person from the hot environment and loosen tight fitting clothing, rest cramping muscles, rehydrate until cramping ceases and snack on foods high in electrolytes including sodium and potassium.

Heat Exhaustion

Heat exhaustion is a progression of heat illness in which the body loses significant amounts of fluid and electrolytes because of heavy sweat loss and inability of the cardiovascular system to compensate for the increased exertion level. Symptoms of heat exhaustion include: headaches, dizziness, cool and moist skin, rapid pulse, shallow breathing and cramps. Treatment involves moving to shade/air conditioned environment and loosen any tight clothing, especially on the face and neck. Have the affected person lie down, rest, drink water and eat foods high in electrolytes. Cool the body with fanning, wetting clothes, etc.

Heat Stroke

Heat stroke is a life threatening condition of severe hyperthermia (elevated body temperature) caused by excessive exposure to natural or artificial heat. Symptoms of heat stroke include: rapid pulse, altered mental status, extreme body heat with little or no sweating, unconsciousness and dry skin. Treatment for heat stroke includes aggressive, immediate cooling of patient, including moving to shade, remove excess clothing, pouring water onto head and torso, and fanning. This is a severe medical condition, send someone for help while continuing cooling.


Hyponatremia is caused by high water intake, low sodium intake and high electrolyte loss through sweating, causing a drop in blood sodium levels. Symptoms of hyponatremia are frequent urination, high water intake with little salty food, headache, nausea, vomiting and muscle cramps. Treatment for hyponatremia includes eating salty food, and evacuate if mental status decreases.

A bit of prevention and training strategy can keep you healthy and on track. Stay hydrated, fueled and rest often in the summer!

Training In The Heat

So happy to be at Phantom Creek after a brutal hike across Utah Flats in the Grand Canyon on the approach to climb Isis Temple.
So happy to be at Phantom Creek after a brutal hike across Utah Flats in the Grand Canyon on the approach to climb Isis Temple.

The human body is an amazing machine that is capable of adapting to a variety of extreme environments. From a physiological perspective, heat stress has the potential to develop into a life threatening condition rapidly if you fail to adjust your training program. It is far safer to progress slowly as summer temperatures rise and prevent heat related illnesses than having to recover from one. Try incorporating the following tips into your training strategy to prepare for training in the heat.

Avoid training between 10AM and 4PM outside

The majority of heat related illnesses occur during these hours. Training in the direct sunlight can also increase the temperature by 15-20 degrees or more. Your body is simply incapable of sustaining high intensity under these conditions. Time your training/movement around these hours. One of our favorite tactics in the desert is to do a dawn patrol, starting  by headlamp and trying to finish by 10am.

Avoid training when temperature is above 90F and 60% humidity

Increases in humidity negatively affect the bodies’ ability to cool itself through perspiration. When the humidity levels exceed 60%, sweat evaporates at a slower rate causing the body to retain heat.

Take the time to acclimatize

Acclimatization is vitally important when training in environments hotter than you are accustomed to. Allow at least 10-14 days to acclimate to increased heat and exertion levels. Studies have shown that bodies adapting gradually to elevated heat and training intensity can dramatically lower electrolyte loss through sweat and becoming more efficient at managing internal hydration levels.

Lower your intensity

Decrease intensity when training, especially during the acclimatization period. Hydration losses can greatly exceed the bodies’ ability to absorb water. Lowering intensity decreases these losses and can help prevent heat related illnesses.

Wear the right clothing for training in the heat

Wear light weight, light colored and loose fitting clothing. If your training brings you near a water source, SOAK your clothes and body to shed heat and speed the evaporative cooling process.

Training in the heat is possible if you are willing to make some modifications to your normal training routine. Prevention of heat illness should take priority over intensity of training during these times. I strongly encourage you to apply these simple guidelines to your training in hot environments. It can mean the difference between recovering at home or in the emergency room. Be safe out there this summer.

Related Article: Signs Of Heat Illness