Power Versus Stamina in Triathlon Training

Being an endurance athlete for over half of my life, I can safely say I’ve trained the majority of those years the wrong way. I thought, ”I’m an endurance runner so I need solid endurance.”  What I had no knowledge of was the need for stamina … and even more importantly … the need for power.

Don’t confuse stamina with endurance.  

Endurance is the ability to go as long as possible at whatever pace necessary to achieve said longevity. Stamina, on the other hand, is the percentage of threshold power you can maintain during your expected race time.  

For example, if your goal for a half ironman is to complete the bike leg in two and half hours, stamina would be the measurement of what watts or what heart rate you should be sustaining in order to achieve that goal and still have a good run.  

This is why knowing your threshold power is so key.  We use that as a basis for our expected stamina.

I’ll use the half iron bike leg example again to expand. Let’s say to achieve a 2.5 hour bike time, you’ll be using 75% of your threshold power over that time (remember that threshold power is the maximum power you can sustain for up to 1 hour).  But think about this.  If you can increase your stamina, then it’s possible you could be holding 80% of the threshold power for the same amount of time.  Such a change would obviously result in you completing the bike portion in a shorter amount of time.  

On the flip side, what if you increase your threshold power?  Well, if your stamina stays the same (75%), then you’re still holding more power during the 2.5 hours.  Holding more power equals greater speed.  Thus, once again, completing the 56 mile bike leg will take less time.  Now imagine increasing both threshold power AND stamina!  The results compound and you become significantly faster!

Ok, hold on a second.  Let’s not get ahead of ourselves.  

The caveat to this reality is that no matter who you are, increasing stamina can only go so far.  No one, and I mean no one, can hold 100% of their threshold (T) power for the duration of an ironman.  The idea is illogical because the very definition of threshold power is that this is your max for one hour.  To hold 100% of your T power for over an hour is a paradox.  That would simply mean you have incorrectly measured your original T power.  

In other words, a plateau of stamina exists for all of us.

Now for threshold power, on the other hand, technically there are no limitations.  It can grow as high as your physical body will allow it.  Yes, there’s obviously a plateau since no one can be infinitely strong, but logically we’re not limited by a percentage.  The higher your threshold power, the faster you will go at a constant percentage of stamina.  

This is the number one reason why you should always focus on increasing threshold (T) power BEFORE increasing stamina.

The truth of the matter is most athletes will naturally gain the necessary stamina needed for their triathlon simply by doing any sort of training.  The capability of holding 75-80% of threshold power is not necessarily something that most athletes can’t do for their long distance race.  What they’re mostly restricted by is their T power cap.


Elevating power first is what will encourage the growth of your stamina later.  It’s nearly impossible to increase both at the same time.  This is because if you’re putting in long sessions, you’ll need to recover from them.  You don’t have the capacity to build power.  Attempting both results in overtraining and burn out.

TriDot hones in on this fact.  We keep the long sessions shorter in the beginning so we can increase your threshold power first.  Then we build stamina later.  It’s impossible to not produce results in this manner.

Need proof?  Let’s go back to the bike leg example.  Say before TriDot your T power was 200W and for a half iron race you were able to hold 80% of that.  That would mean you held 160W for that race.  Let’s throw in a race time of 3 hours 6 minutes for that wattage (of course we know this would vary greatly depending on terrain, rider weight, aerodynamics, etc.).  

If you increase your T power from 200W to 225W and by race day we’re able to maintain your stamina for the new T at 80%, then that would mean your new race power is 180W.  This puts your bike leg time at most likely 8-10 minutes faster!

Think about how exciting this is.  With an increased T power, you will effectively be training for a shorter duration race.  You no longer have to maintain that stamina percentage for 10 minutes longer than you’ll now be racing.  

Now imagine if you were able to raise your stamina from 80% to 82% for the race.  That’s a 5W increase.  Another minute saved in the half distance right there.  And increasing stamina is easier when you’re a more powerful athlete.  The science is undeniable.  It’s essentially a “rich get richer” effect.

TriDot training takes advantage of this smarter approach.  We factor in every detail about the athlete and focus on building their T power first.  The maintained or increased stamina comes later and is an extension of the foundational training.  Therefore, the key words to live by are:

Obtain the power then learn how to sustain the power.

This will lead you to train the right way.


 Fast before far.  Strong before long.

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