You are currently viewing Adaptation


Zone 3 is too much pain for too little gain.
Let’s tease this apart a bit to gain more understanding.

• Zone 3, in a five-zone exercise intensity model, is the workload often called ‘tempo’ or ‘threshold work’, meaning that the intensity is just below Ventilatory Threshold 2 (VT2) and the Anerobic Threshold (AnT), which is the approximate boundary between zone 3 and zone 4. Above VT2/AnT is where interval sessions are typically done.

• Pain refers to more than just the sensation of experience; it’s the overall cost to the body: i.e. substrate (fuel) utilisation, tissue health, overall stress and recovery time required.

• The amount of adaptation that can occur, for most athletes, with zone 3 work is much less than the body can get out of it. This isn’t to say that zone 3 workouts don’t have their place, especially for elite athletes with years of continuous training and a very solid aerobic and strength foundation. It’s just that a vast majority of athletes hang out in this territory far too much.

❝ Many people think that if they suffer more by going harder it’ll give the best adaptation. The problem is that ‘the harder, the better’ doesn’t generate as strong a signal as duration. Longer (duration) is better.❞
~Dr Stephen Seiler
Why you should train like a pro, Mid Life Athlete, Jason Smith & Greg Ryan, 2021.05.17



Why does training mostly at low intensity (zones 1 & 2) provide the best aerobic fitness gains, and do so for athletes of all levels and in a huge variety of sports—ones that last only a few minutes up to many days, or longer? Dr Seiler clarifies:

i. We have fundamentally under-appreciated the importance of duration in eliciting the signals for adaptation at the cellular level.

ii. There’s a balance between signal and stress. Athletes tend to focus on ‘the single workout’ and lose sight of the forest of workouts. Sustainability is what gives improvement—the basket of hundreds of workouts by being healthy, and consistently layering workouts on each other.

iii. Energy availability. Training too much at higher intensities leads to constant glycogen depletion thereby limiting adaptation [because the immune system that repairs the body after workouts requires glycogen], whereas longer sessions that burn more fat (via training at lower intensities) provide good [adaptation] signal without glycogen depletion.

Lactate Testing

If we can stay healthy, have better recovery and achieve more workouts in a year it’s usually going to be associated with better development and more consistent performance.
~Dr Stephen Seiler

One of the adaptations we’re looking for is metabolic oxidisation (the type of fuel used for energy). Training below Ventilatory Threshold 1 (VT1) and the Aerobic Threshold (AeT), which delineate the the boundary between zone 2 and zone 3, “pushes the oxidation curve to the right”. This means that burning fat as the primary substrate occurs at increasingly higher intensities, which equates to less reliance on glucose as a substrate and therefore less lactate production. Over time, this allows more total work to be done because all energy systems are available, both for longer durations and at higher intensities. “Even at lower heart rate intensities there’s still a significant metabolic flux going on”, explains Dr Seiler.

As stated above, there’s nothing wrong with doing a tempo/threshold session. But the athlete has to ensure it’s the goal of the session. Athletes are often given a heart rate or effort range within which to perform the session. Unfortunately, the upper edge of that prescription becomes a perceived target to reach and maintain instead of an absolute ‘no cross’ line. Jan Olbrecht PhD, in his book “The Science of Winning”, was very clear that once an athlete enters the yellow (zone 3) or red (zone 4) there are several stress responses that are turned on; at that point, the entire session must be classified as hard, not aerobic, base building.

To help myself avoid falling into this trap, at the start of a workout, I typically let my body warm up over 15 to 45 minutes as I move closer to the lower, prescribed boundary. I’ll either continue to train at that level or aim for the middle of the prescribed range. I can drop it down to the lower end of the range if some part of my body isn’t feeling happy on that day or just not ready yet for that session without feeling like I’m not achieving the desired stimulus. Hanging out in the middle of the prescribed zone also provides a buffer for when I’m feeling spry and want to open up the throttle a bit, or if I’m daydreaming about podiums, get carried away, and my heart rate increases.

The take-home point is that you improve over a long time, but you can serve up demise in a very short amount of time. Know what your goals are for each session and for the years to come. Take inventory of your body and mind. Train smart.

❝ True (lasting) endurance adaptations are so small & so slow that they are imperceptible in the short term.❞
~Alan Couzens

✌️ ∙ 🌱 ∙ 🙏