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There are several terms in training articles that get thrown around in confusing ways: aerobic threshold, lactate threshold, anaerobic threshold, aerobic capacity, VO2 Max, anaerobic capacity, and functional threshold power or pace. Many of these terms have definitions that are quite similar to each other, with minute differences that matter in the field of sports science, but are basically equivalent for athletes training. These terms all fit into three main categories that are important for us to understand as endurance athletes.

Aerobic threshold (AeT)

The aerobic threshold is defined as the intensity of exercise at which lactate levels in the blood begin to rise from their baseline. Lactate accumulation indicates that the metabolic pathways that are fueling our muscles with energy have begun to shift to a combination of aerobic and anaerobic mechanisms, and if the intensity that we are working at stays the same, or increases, lactate will continue to build. This is in effect an endurance limiter. Aerobic capacity is essentially the same term – it refers to the amount of work that can be performed before the athlete reaches their AeT.

Lactate Threshold (LT)

Lactate Threshold is the level of intensity at which lactate in the blood reaches 4 millimoles/liter. This is a tiny amount and is something that requires a blood test during exercise in a lab to determine. The more useful definition for athletes is that it is the intensity at which lactate production exceeds its removal. This is also the defining line above which, exercise can only be sustained at that intensity for short periods of time before fatigue and slowing set in. Consider this the upper-end limit to endurance. While the definitions are slightly different, this is essentially the same thing as Anaerobic Threshold (AnT) anaerobic capacity, and functional threshold. They all refer to the point at which the metabolic pathways switch to a primarily anaerobic pathway that burns glycogen (carbohydrates), and the ability to sustain that intensity will be limited.

VO2 Max

VO2 Max refers to the maximum amount of oxygen that the body can utilize for energy during an all-out effort that is well above their AnT. Theoretically, the better your body is at delivering oxygen to where it needs to go, and the better adapted your muscle cells are to exercise, the more oxygen they will be able to utilize to make ATP (energy) and the more energy they will have to do work. Sounds simple enough right? VO2 Max has been a big focus in endurance sports for a long time, partly because it is easily quantifiable. However, ask elite coaches, such as those at Uphill Athlete, and they will tell you that VO2 Max doesn’t correlate very well to performance, and seems largely determined by genetics. Athletes for decades spent considerable effort training to increase their VO2 max, but recent studies suggest that that time would be better spent increasing the aerobic threshold.

Why do these terms matter? One dispels a popular myth related to training (VO2 Max), while the other two are the categories where we as athletes have the greatest abilities to affect our metabolic and motor pathways to achieve better performance. The balance of aerobic threshold and lactate threshold training that we do as we prepare for a large climb will determine how we perform. We’ll be diving into these two topics in more depth in the coming weeks so stay tuned!

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There are several great resources that provide a lot more information on these topics. For this article, we pulled from Joe Friel’s blog and from the recent book, Training for the Uphill Athlete, from the folks at Uphill Athlete. We can’t recommend the book enough if you are serious about training for endurance mountain sports!

Comments? Questions? Share your thoughts here in the comments!

Hello all,

Today we woke to perfect weather to hit the trail. A mellow walk past yak corrals took us to our first uphill. A little more breathing and some sweat brought us to a downhill trend to the river crossing. Before we crossed, the team enjoyed an ice cold foot soak. Shortly after the river it was tea time. The saying out here might go Dal Bhat power 24 hour but I think for us its hot tea power 24 hour. After filling our energy tanks with tea we madr our way up the last hill of the day. The top of the hill brings us to a special place, the climbers memorial. A sadness fills this place but also brings to reality the risks taken to climb mountains. After acknowledging those who have fallen we continued our journey to Lobuche. Not far from the town we pass by the Lobuche peak Basecamp. We gaze at our objective but first we must go to Everest Basecamp. A little training in the evening brought us to dinner. A birthday cake surprise wrapped up our day with smiles and chocolate covered mouths. Another good day in the books and more to follow. 

Goodnight all,

RMI Guides Adam, Hannah, and team

While not everybody reached the summit of Aconcagua today, we all soaked in the entire experience. It was a perfect day to simply be in the mountains. Stars illuminating the landscape this morning. A windless day with not a cloud in the sky. Shadows creeping across peaks far in the distance, helping gauge the time of day. It was very easy to be distracted from the strenuous climbing by the surrounding beauty.

Till next time,

RMI Guide Luke Wilhelm

High Intensity Interval Training, often referred to popularly as HIIT training, have been featured in a few recent studies that concluded that a short HIIT workout was as or more effective at promoting cardiovascular health than steady state activity. The first paragraph of a recent New York Times article reads:

Think you’re too busy to work out? We have the workout for you. In minutes, high-intensity interval training (HIIT) will have you sweating, breathing hard and maximizing the health benefits of exercise without the time commitment. Best of all, it’s scientifically proven to work.

Despite the recent attention, interval training is not anything new to seasoned athletes and coaches who have understood the benefits of repetitive high intensity workouts for a long time. Many of the recent studies have focused on previously sedentary people trying to improve basic cardiovascular health, rather than on elite athletes striving towards a performance goal. With that said, we have and continue to encourage climbers to utilize interval training (by it’s nature high intensity) as part of a well-designed training program.

Interval training can accomplish a wide array of tasks and works best when the focus of a workout is clear:

Longer intervals, from 5 to 8 minutes, at 70 – 85% of max heart rate work to improve the lactate threshold, the body’s ability to metabolize and clear lactate build up from muscle cells, increasing the amount of work that the body can perform sustainably. A good example is an elite level marathon runner, who is able to sub six-minute miles for over two hours during a race. The intensity that they are working at is very high, yet the body is able to sustain it over a very prolonged period of time.

Shorter intervals, from 20 seconds to a few minutes, performed at 85 – 95% of max heart rate (very intense!) increase the body’s anaerobic threshold, it’s ability to perform work while in oxygen deficit. Think Olympic swimmer in the 50-meter butterfly: the intensity that they race at surpasses the body’s ability to clear lactic acid and to provide enough oxygen to the muscle cells for them to continue that pace for a long period of time. The race is very short, however, and for that 20-something seconds, their muscles are able to put out an immense amount of power in oxygen deficit.

It may seem as though interval training isn’t as applicable to our sport of mountaineering. We tend not to sustain the very high levels of output, but instead operate for far longer periods at moderate intensity. It is the very definition of an endurance sport. Interval training provides other physiological adaptations however that go beyond the abilities of the skeletal muscles. Interval training is shown to increase cardiac output, by increasing the size of the left ventricle, the stroke volume and the overall contractility of the heart. Increased cardiac output supplies more blood to muscle cells, delivering more oxygen and removing more waste. Additionally, interval training has been shown to increase the size and density of mitochondria in the muscle cells. Mitochondria use oxygen to convert glucose to ATP (the cells’ energy source). Both of these adaptations help endurance athletes go longer, faster and with less effort, and ultimately help us in the mountains.

Interval training is harder on your body than traditional steady state workouts and requires longer to recover from as well. Therefore, too heavy of a focus on interval training can lead to overtraining and injury. More of a good thing isn’t necessarily better. It’s important to realize that a good training plan maintains a balance of high intensity workouts and lower intensity steady state workouts.

As part of the recent HIIT hype, people have championed the fact that HIIT gets more done in less time, even as little as 10 minutes. This may be true for an average person whose goal is to improve overall cardiac health, but for athletes working towards goals in the mountains, remember that there are no short cuts. Time invested in your training will lead to a more enjoyable and successful climb.

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Questions? Comments? Share your thoughts here!