Tag: ATP-PC

Durations to think about in training

How long can you sprint? Why is the first minute of your parkrun fast? Why do we train differently for a 10K and a marathon?

Each of these questions is determined by what is going on in the body and its capacities. While the exact figure can be a touch higher or lower for you – especially depending on whether you’re well-trained or badly trained – overall they’re numbers that help structure your training. With time and focus you should be able to get a sense of exactly where your numbers are.

8-10secs Sprinting energy

Sprinting is powered by the phosphocreatine energy system, which is sometimes abbreviated to ATP-PC, or called the Anaerobic Alactic energy system. I like to call it the Sprinter’s energy system because that’s more meaningful and tells you what it does.

It produces energy quickly and allows you to move very fast but it doesn’t last long. For a distance runner, it’s useful for getting off the start line or finding a sprint finish or mid-race surge. Surprisingly it’s also the energy system you call upon when you get up off the couch to go make a cup of tea!

This is the system that kicks in when you do interval work – especially if you set off fast.

1min30 Anaerobic limitation

Beyond the sprinter’s energy system detailed above, there is a secondary anaerobic energy system. Its names include Fast Glycolysis, Anaerobic Glycolysis and Lactic Acid energy system. It’s what 400m runners use in their races and is a big contributor to the 800m.

For distance runners, they’re using it when they run intervals at the track which last within this timeframe. Being anaerobic it gets you out of breath and you find yourself puffing. This isn’t to say there isn’t some contribution from the aerobic system but for anyone with good speed, it’s mostly coming anaerobically.

For most parkrunners, you’ll see the first 1-2mins are quick and then their pace drops away. This is because they’ve mostly run on anaerobic energy and then they’re having to rely on the aerobic.

8min Running at VO2max

V02max is a scientific measure of your aerobic capacity. The body takes in oxygen through the lungs, the heart pumps the oxygen around in the bloodstream for the muscles to use. There is a limit to how much oxgyen you can transport and exercise scientists finding this out by doing treadmill tests and collecting the air their subject breathes in and out. I did a VO2max test at college and it is not a pleasant experience. It’s nice enough at the slower speeds but once you get up to speed and are beginning to exceed your VO2max, you quickly begin to accumulate oxygen debt and then you’re hanging on mentally to continue running as the treadmill pushes you. Eventually you have to stop, or I suppose you could collapse and fall off the back of the treadmill if you have the willpower to push on!

In real terms, we have the ability to run at our VO2max pace for up to eight minutes. We can go faster for shorter periods of time, we can go slower for longer. Reigning Olympic 1500m champion, Jakob Ingebrigtsen set the 2-mile world record in June 2023 at 7:54 which means he was running on his VO2max for the race. A world-class woman like Sifan Hassan has run 3,000m in 8:18; so she’s probably thereabouts.

None of this makes a lot of sense from the ordinary runner’s perspective other than to recognise that a high aerobic capacity is very helpful for good distance running. Even when you have talent it takes time to build this aerobic capacity.

12min – steady state reached

Another thing I learned at college was a phrase used by one of the physiology lecturers “it takes twelve minutes to reach steady state”. As I wasn’t a distance runner at the time or interested in physiology/biology lectures, it didn’t mean much to me. It probably doesn’t to you.

What it means in practical terms is that this is how long, on average, it takes for the body to warm-up. If you go running off down the road your legs may feel good but your breathing will struggle. You’ll settle down after a few minutes but it actually takes longer for the body to properly warm-up.

Personally I take a good 15-mins or so to reach a point where my speed has picked up and my breathing can cope. Other runners may take a little less than twelve minutes. Either way there’s two offshoots to this – firstly your quick jog down the path and back for a minute at parkrun isn’t a proper warm-up. Secondly if you’re going out for a run and it only lasts 20 minutes you’re not actually getting lots of training benefit from it. Of course this applies more to regular, committed runners who do significant volumes of training than those who only run once or twice per week.

40min – optimal production of human growth hormone

During exercise the body produces many hormones but let’s focus on human growth hormone. As the name implies this is important for repair, growth and replenishment within the body after a bout of hard exercise.

At the beginning of any run the production of this hormone begins to ramp up and at an hour it has reached its highest level at 600% of where the body started out – a sixfold increase. At forty minutes we’re already at 550% so while the next twenty minutes will raise the level higher, if you’re time pressed or out for a recovery run this is the optimal duration. You’re getting close to the maximum but in only two-thirds of the time.

Combine this with my comments above on warm-up taking twelve minutes and you can see why a run lasting at least thirty minutes is beneficial.

1hr – limit at lactate threshold

The lactate threshold is much talked about. It’s sometimes calculated as the fastest pace which you can run in an hour, something of a self-defining quantity. Once you go past the hour, the pace has to drop and you’ll be into Steady State and closer to marathon pace. While you wouldn’t train at this pace frequently or for this duration, it is worth knowing that when you’re putting together endurance training sessions, it’s good to go out for an hour.

1hr30 – glycogen depletion

If you’re training at a decent pace or you’re aerobically inefficient then you can expect your glycogen stores to run out somewhere around an hour and a half. This is why elite marathoners take on fuel during races. Even though they’re highly efficient, when they’re due to run for over two hours, their glycogen stores won’t quite be able to last them running at marathon pace for that long.

Running out of glycogen is the infamous “hitting the wall”. That usually takes place around twenty miles which fits with elite runners having stores for around 1hr40-45. Often they start a race a little slower and therefore preserve their stores.

With training the body learns to store more glycogen but to achieve that you have to get the body to deplete its stores or close to it in training. If you keep doing long runs taking gels or supping energy drinks the body has no need to learn to store more.

2hr30 to 3 hours – diminishing training returns

In their Hansons’ Marathon Method book, the Hanson discuss why long training runs lasting over three hours are not beneficial to runners. I detailed some of this in the 20-mile myth. Their point is the longer you run for, the more damage the body has to recover from. Slower marathon runners are prone to spending four hours or more on their Long Runs week after week which leaves them struggling for motivation and the body to recover. It’s best not to run too often for longer than 2hr30.

With many of these variables, training improves them. An untrained sprinter may have a ATP-PC system that only lasts a few seconds initially, like their Lactic Acid system. Distance runners can extend the time they spend at VO2max or lactate threshold pace.

Efficiency and my postman

I often say “Hello” to my postman, if he doesn’t look too busy I’ll engage him in conversation or give him a wave as I zoom by in the car. Before Christmas there were a couple of days where I received post at around 4pm. This being later than usual, I chased after him with a couple of mince pies and commiserated about the long hours he was doing and asked what time he’d started and finished. He said he was arriving at the sorting office just after 6am; doing a couple of trips back there pushing his trolley up the hill and on the longest day had delivered his last letter at 4:45pm, arriving back in the office at 5:07pm. He delivers six days per week.

I once did a spot of leaflet delivering to local houses and was tired after two hours of it. On paper, it doesn’t seem much, walking around, occasionally climbing two or three steps to a door, and sometimes bending down to a low letterbox. By the time I finished I was tired and hungry and I’d only done my local roads. I’d estimate my postman’s route is three times bigger than what I’d done.

So you’d think he’s superfit from all that walking and to an extent, he is. You rarely see an overweight postman or woman. It’s an active job. Yet when I looking at that fitness from a running perspective, he’s not going to go out and run a sub-3 marathon without some other training. What’s he’s got is functional fitness for a specific task – walking at low speeds, pushing a trolley with letters and parcels and the ability to do some step-ups. He could probably go out and do a charity walk or ultra with ease.

This is the mistake many people make as they get older. They think that if they do lots of walking or playing golf, it’s keeping them fit but it’s really not doing that much because there’s very little exertion taking place. Same with people cycling bikes along the promenade or cycle paths. If you don’t push yourself, the body becomes efficient at what it does.

We can begin to get an idea of how efficiency works by looking at things through a biological / chemical perspective. For muscles to contract they need to be fuelled by a substance called ATP which the body sources or creates from its fuel stores using one of four energy pathways. I’ll give an overview of the four here but if you want to jump past the details, the info relevant to the remainder of this post is in the summary lower down.

ATP-PC or Alactic Anaerobic energy system

A small amount of ATP is stored and readily available for fuelling high intensity activity. Energy is created very fast, so the muscles are able to work fast. But there’s a limited quantity of the substances used in the ATP breakdown and rebuilding process so it’s exhausted after around ten seconds. This is why it’s sometimes referred to as the sprinter’s system. Those guys and gals are quick but they can’t last even one lap of the track. For distance runners, this energy pathway isn’t very useful other than for a quick start off the line, or a kick at the end of a race.

Anaerobic Glycolysis or Fast Glycolysis

Carbohydrates stored (as glycogen) in the muscles and liver can be broken down to release glucose. Each molecule of glucose, when broken down by Anaerobic or Fast Glycolysis, creates 2 ATP. When we talk of anaerobic exercise, it’s usually this system we’re talking about (although the ATP-PC system is also covered, but as I wrote it’s mostly irrelevant to distance runners).

Aerobic Glycolysis or Slow Glycolysis

Usually referred to as the aerobic system, this takes a molecule of glucose and breaks it down to create 36-38 ATP. To create this quantity (much higher than the Anaerobic version) it uses oxygen in the breakdown and goes through more steps hence it powers muscles slightly slower. This is why a marathon, which is run almost purely using this pathway, is never going to be as fast as the runner’s 5K.

Lipolysis or fat-burning

The other part of the aerobic system is fat-burning. Depending on the type of fat and how long its molecular chain is, a molecule of fat breaks down to produce 120-140 ATP. Again it needs oxygen but the reason why it produces so much ATP is because it goes through even more steps and chemical reactions to achieve it. This is why ultra-running is even slow than marathon running!

Summary

ATP-PCInstant energy for 10 seconds
Anaerobic / fast glycolysis2 ATP
Aerobic / slow glycolysis36 – 38 ATP
Lipolysis / fat-burning120 – 140 ATP

Enough jargon, let’s get back to postal deliveries …

What I’m about to describe is more of an analogy than physically possible. Firstly the numbers are wrong in magnitude – there are billions of ATP being processed in each muscle cell to keep the body alive. Secondly the body doesn’t use one energy system exclusively at any one moment, it’s often a mixture of them all. Putting the technicalities aside, let’s use those ATP numbers to begin to get an idea about efficiency.

When I went delivering leaflets as an untrained delivery worker, let’s say I was only using the Anaerobic / Fast glycolysis system. After two minutes I’d used up the fuel I’d created and was having to break down more. It’s no wonder then that, after two hours of delivering leaflets, I arrived home feeling tired and hungry – I’d used up my fuel stores and exhausted the muscles sixty times over. Such a big effort probably triggered a stimulus to adapt to a more efficient, aerobic pathway.

If I’d stuck at the delivering for a few weeks, my body would have adapted aerobically and I’d have found myself able to last over thirty-five minutes, almost forty minutes, using the same quantity of fuel I’d previously used anaerobically in two minutes. So now if I was out for two hours – what had previously required sixty refills would only need three to fourr. The job would feel much easier and I’d likely arrive home feeling less hungry.

If like my postman, I was doing this job six times per week for months on end my body would go a step further and begin to get efficient at fat-burning. Suddenly all the energy which had been used up in two minutes on my first day out would now be more than enough to last for over two hours (120 – 140 minutes). Or to put it the other way around. When my postman was delivering for over ten hours at Christmas time, he was able to fuel it with the same level of food that I would use up in ten minutes of delivering leaflets.

And in a nutshell that is efficiency and why, as runners we get faster at running if we train effectively. We go from sweating, gasping and wanting to stop while running at ten minute mile pace to being able to jog aerobically at that pace.  We arrive home feeling fresher, less tired and without so much hunger. Suddenly on our runs we have more energy available to run further and push harder. But if, like my postman, all you ever do is go at one speed then you won’t get any faster, only more efficient. It’s why once the body has adapted from running anaerobically at one pace to running it aerobically, doing some speedwork recruits the next level and begins the process all over again.