I spoke with Durham yesterday.
Tomorrow will be 96 hours.
What should I do?
What soreness have you had, if any whatsoever?
Zero? When you're stretching it, zero?
I think you do just like or ACL return to play: 20 meters.
Maybe 10 efforts of 20 meters and that's it.
Plus, I’ve got a little crew going on today.
Tom, what are you running today?
2k, and I’ll be doing six 100 meter runs as well.
-And, Davey, what are you doing? -I'm doing four 400s.
So, different distances.
I thought today would be a perfect chance to talk about fatigue and what causes it.
With something like a one, a two, or a 3k run,
your biggest limits are going to be your ability to process oxygen,
so your VO2 max; and your lactate threshold,
your ability to buffer and handle metabolite build up.
There isn’t a clean-cut line between energy systems.
They're all inter-playing all the time.
When it comes to your VO2 max -
or sometimes it's called Maximum Aerobic Speed -
is the most amount of oxygen your body can consume,
process, and use, to produce ATP.
If you go above this point,
your body starts demanding and using more energy
than you can produce aerobically.
This is called your anaerobic threshold.
Sometimes it’s called the lactate threshold, or the lactate inflection point.
Above this point is where your body starts accumulating metabolic by-products.
With 400s, the biggest limit to your ability
now, 400 is tough. It’s like the toughest distance run.
The reason for that is the metabolite build up.
There are two key metabolites slowing you down here.
The first is hydrogen ions,
which are produced as a by-product of turning glucose into pyruvic acid.
These hydrogen ions are normally good for us,
but in the absence of enough oxygen,
they start causing acidosis in the muscles,
which slows down the contraction rate.
The second is inorganic phosphate.
As we break down ATP, we form inorganic phosphate and energy.
This inorganic phosphate has an absolute love affair
with calcium, which I'll talk about soon.
With your hundreds, your strength and power
are still going to play a massive role,
but your phosphocreatine stores are also going to come into play as well.
Our muscles use ATP to create energy.
If we didn’t, our cells would die.
The fastest way to replace that ATP is with a compound called phosphocreatine.
That phosphocreatine donates one of its phosphate molecules
back to the ADP to recreate ATP.
Our muscles have enough PCr for about six to 10 seconds of high-intensity work.
Once that runs out, our body has to rely on anaerobic glycolysis,
which is a much slower and less efficient form of energy production.
With something like a single 20-meter sprint,
there isn’t, really, anything going on here causing fatigue.
The biggest limits to your performance are going to be your technique,
your strength, and your power.
But when it comes to repeat 20s, or repeat anything, really,
one of the biggest factors at play is your sarcoplasmic reticulum’s
ability to resequester calcium.
This is where things get really nerdy, but bear with me.
Our brain sends a signal down the axon to the muscle cell.
That signal then travels across down your T-tubule,
which promotes the release of calcium from this thing
called the sarcoplasmic reticulum or the SR.
That calcium is then released and it then acts on your actin and myosin
clearing the way to create the sliding filaments that we know so well.
Remember before, how I mentioned inorganic phosphate loves calcium?
Well, those two kind of partner up inside the muscle cell.
When they partner up, that calcium can’t be reabsorbed back into the SR,
which means we can't repeat and recycle that contraction process.
With any repeat sprints, it’s not like these factors are independent.
They all interplay and work together.
Davey, good luck for your fourth.
I don’t envy Davey doing four 400s at all.
Also, Pete, you were supposed to be doing the 400s.
So, Davey kind of hates you now.