Ever looked at some of the performance data on your fitness watch and wondered what the heck it all means? If so, you’re not alone. To help get a clearer picture of what all the different performance metrics mean for us as part-time athletes, we talk to ultra-distance trail runner Bennie Roux and get his pragmatic take on things.

Okay, so you’re really into your sport and realise you need to adopt a more scientific approach to your training. So you diligently do your research; you talk to mates, read boring specification lists and watch copious video reviews online. Finally, the big day arrives, it’s time to head out and get yourself a cool fitness watch – it could be a top-of-the-line Fenix 5X or, if you’re on a budget, maybe an older Fenix 3 that’s now going for a steal. All good so far. Bursting with excitement, you un-box your shiny new investment while fantasising about finishing the Comrades or Cape Epic in record time.

“I’m sorted,” you figure, as you head out for your first few runs or rides. You feel great, and you’re sure all the fancy algorithms inside your expensive watch are helping, but how exactly is a complete mystery. Scrolling through the many data fields, you feel like a monkey reading Dawkins – you can see the words and pretty coloured graphs, but nothing’s sinking in; you may as well be reading gobbledygook.

But don’t stress. If you’re new to performance metrics, coming to terms with what it all means is just part of the game. What you need is a mentor, someone you trust with plenty of experience who can explain the ropes. With that in mind, we talked to one of the most hardcore sportsmen we know – NavWorld Ambassador and legendary ultra-distance trail runner Bennie Roux – to get his take on things and help fill you in.

VO2 Max
Understanding your VO2 Max score is relatively easy. Simply put, low scores represent poor fitness levels, while higher scores show you’re getting fitter and can give yourself more of a push. On a technical level, it describes the maximum rate at which you can bring oxygen into your body, transport it to your muscles and then use it for efficient aerobic energy production.

However, bear in mind, there’s a genetic component to how well your body can utilise oxygen, so two equally fit individuals could have completely different scores – a little fact worth remembering come race day. “Asking friends ‘what’s your VO2 Max?’ is a fun game most of us runners play”, explains Roux, laughing. “The best is when your mate’s VO2 Max is higher than yours and you beat him!”

It’s also worth remembering that, to get exact readings, you really need to be on a treadmill in a lab, with a mask on your face so proper measurements can be taken. Says Roux. “Knowing this, I take what my watch says with a pinch of salt. However, I do find it a good general indicator of my fitness levels.”

Race Predictor
What Race Predictor does is run your VO2 Max score through complicated algorithms to calculate how long it would take you to run or ride a specific distance. Projected race times can be viewed for 5 km, 10 km, half-marathon and marathon distances, and will either get faster or become slower, mirroring your fitness level as it goes up or down. However, these times are just predictions – many factors come into play on race day, how fit you are, is just one of them. That said, they do give you a good idea of what to reasonably expect on the day.

The way Roux sees it, Race Predictor times provide a good indicator of what you’re capable of. They’re also a real aid in training, as they provide attainable goals you know you can chase. However, he points out: “This metric needs data, you can’t just put on a new watch and expect immediate results. You have to run with it for at least a week to get any benefit.”

Performance Condition
Performance Condition indicates how well you’ve recovered from your last training session and hence, how well you can expect to perform now. During the first 6 to 20 minutes of your run, this metric analyses pace, heart rate and heart rate variability. The number it then spits out is a real-time assessment, comparing your current state against your VO2 Max score when at rest. Simply put, the higher the number, the better you can expect to perform. Conversely, if you notice numbers starting to fall after pushed yourself hard for a while, chances are you’re getting an early warning – indicating that you might need to adjust your tactics before you “hit the wall” or pick up an injury.

What Roux likes about this metric is that it answers the age-old sporting dilemma “Should I train hard today, or just go for an easy jog?” However, when using this feature, he advises you try and run on a flat road. “When running uphill, you naturally run slower and your heart rate climbs, causing the sensors to think your condition’s much worse than it actually is,” he explains. Roux does not use this on race day though, saying “When stage racing I rather switch it off. Having your watch beep ‘Poor Recovery’ at you six minutes into your run can be very demoralising.”

Training Effect
Chances are if you bought a fitness watch you train because you want results. Here’s the thing though: Because of how our bodies work, the type of training you do now determines the type of results you can expect to see in the future. This metric gives you a sneak peek into how each training session is expected to influence your future fitness levels – allowing you to ascertain whether your routine’s stuck in a rut or not.

“One of the traps many runners fall into is running the same distance at the same pace every day. It’s a mistake I’ve made myself,” says Roux. “Your body becomes so conditioned to your predictable training routine, that all you ever end up being good at is training. It never produces better racing times. I view Training Effect as a big help in this regard.”

This metric builds over the course of your workout and gets updated in real time. Making it a great on-the-go resource, allowing you to structure your current training session on the spot. For example, it’ll let you know when you can push harder, or indicate that you need to slow down before you wander into the overreaching zone – where the end results will probably be more damaging than helpful.

EPOC
Excess post-exercise oxygen consumption (EPOC) is a bit of a mouthful, here’s what it means: It’s a phenomenon where, for a period of time after exercise, your body continues to use oxygen at a higher rate than it would otherwise at rest. This makes sense. When you exercise, you disturb your body’s usual state, and this disturbance requires your body do some extra work to get things back to normal. In fact, the whole point of training is that after exercise, your body will build itself back up to normal, and then some. It’s that “and then some” – also called “supercompensation” – that helps turn you into a fitter and faster athlete.

Since the oxygen used by your body is related directly to the amount of energy it uses, the EPOC measurement is perfect for calculating how much your body’s normal state (homoeostasis) is disturbed by each session of exercise. In other words, it’s a great measure of exercise volume, as it quantifies how much work your body has to do to get back to normal and then some. Says Roux, “Although not as accurate as a lab test, it does provide useful info regarding how well and quickly you’ll recover.”

Aerobic Training Effect
This one’s all about building endurance. Unsurprisingly, it’s also one of Roux’s favourites. He explains, “I love this metric. I’m an ultra marathon athlete and need to focus a lot of my training towards increasing my aerobic fitness, or endurance capabilities.”

In layman’s terms, aerobic training helps improve the ability of your body’s cardiovascular system to absorb and transport oxygen. Benefits from this increased oxygen flow include increased stamina and endurance. It also utilises fat for energy – which is a good thing, too.

What the Aerobic Training Effect metric does is measure the aerobic benefit derived from your exercise sessions – which should correlate with the fitness improvement you expect to get from them. By measuring the EPOC accumulated during exercise, it can assess your fitness level and training habits. For example, when you completely smash a difficult run, you’ve probably given yourself a bigger dose of aerobic exercise and, therefore, a bigger training effect. Typically, as you get fitter, you need larger “doses” of exercise to continue seeing any improvement. Fortunately, the 0-to-5 scale the metric uses to display its results is simple to understand; 0 – none, 1 – minor, 2 – maintaining, 3 – improving, 4 – highly improving, 5 – overreaching.

Anaerobic Training Effect
While there isn’t a specific metric tied to it, the performance aspect most easily associated with Anaerobic Training Effect is your ability to perform and repeat sprints. A soccer match, where the back-and-forth game is punctuated with sudden flurries of high-intensity action, is a good example.

Anaerobic training is good for increasing your ability to sprint and better resist fatigue. It’s also something Roux swears by. “I think it’s of vital importance for endurance athletes to also focus on improving their speed. Anaerobic workouts are great for maintaining your speed and power.”

By analysing both heart rate and speed (or power, if you’re on a bike), this feature quantifies the anaerobic contributions made to EPOC during these periods of exertion. The higher the anaerobic training effect, the better you’re doing. High-intensity intervals, for example, have been shown to improve several aspects related to your ability to perform. By analysing the type of workout you did, it can tell you more precisely how the session helped. For example, if it detected you’d completed several high-speed repeats, you might get a score of 3.5 saying, “This activity improved your anaerobic capacity and speed due to several high-speed/power repeats.”

Lactate Threshold
Your lactate threshold is that particular level of effort was you begin to feel it and fatigue starts to accelerate. For a well-trained runner, this usually occurs when they’re at about 90-percent of their maximum heart rate and running somewhere between a 10 km and half-marathon race pace. For the less experienced, the lactate threshold is often below the 90-percent maximum heart rate mark.

Knowing your lactate threshold lets you train with more precision. Many coaches prescribe some running at lactate threshold as part of one’s overall training program. That’s because your lactate threshold is the single best way to determine your capacity to keep on going. As your ability to cover longer distances at faster paces increases, you’ll see increases in your lactate threshold. This metric is also valuable for recognising any personal training zones that will help boost your performance.

Some Garmin models can detect your lactate threshold either through a guided workout or automatically during a normal run. Either way, by gathering heart rate data across a range of paces, the device will estimate your lactate threshold both in terms of running pace and heart rate level in beats per minute. “This is probably the one feature I love most about my new Fenix 5,” says Roux. “I do a Lactate Threshold test once a month, and also use the information during my races.”

Recovery Time
Allowing your body adequate time to recover between training bouts is critical. Unfortunately, this is an often overlooked aspect of the training process. “Remember, we train to be better athletes, not to become better at training,” says Roux. “To reach your full physical potential, it’s always better to train when your body’s fully recovered. Otherwise, you’re just wasting your time.”

Keeping track of your recovery levels will reveal when training hard is beneficial, and ensure all your effort is rewarded with the results you wanted to see. After each workout, your device shows the number of hours before you’ll be back to near 100-percent and capable of performing another hard session or running a race. The calculation is produced using a unique digital model of your physiology. It utilises a combination of the session’s training effect score, performance and fitness level assessments (conducted during the session) and the number of hours of recovery time remaining on your clock from your previous workout. Roux’s advice: “Even if it says something drastic, like you’ve got to put your feet up for three days, just do it.”

Training Load
Want to see the bigger picture? Then this is where you need to go. Training Load is a measure of the total volume of your training for the last 7 days. Your compatible Garmin device then compares this weekly training load to your longer-term training load – taking into account your fitness level – and indicates what range you’re operating in. “This is always nice to see, especially when you’re training towards a specific goal. Know when to work harder, or when to take a rest day is a huge help,” says Roux.

Granted, pushing yourself is the way to get results. But Roux points out that, by overreaching and training too hard, there’s also a good chance you’ll pick up an injury. His advice: Always watch your training load, checking to see if you’re doing too much or too little.

The available training load ranges are:
High: Based on your current fitness level and recent training habits, your training load may be too high to produce positive results.
Optimal: This range is ideal for maintaining and improving your fitness level. Keep up the good work!
Low: Your training load is low for your current fitness level and training habits. If you stay in this range you’re unlikely to see further improvement.

Training Status
Training status is the first feature offered by Garmin that truly analyses not only your current run, but also your longer-term training habits. Providing you with powerful insights into how your training’s really going. Says Roux, “I like this metric because it takes very technical data and presents it in a simplified way. I also find it very helpful when chasing goals as it prevents me from over training.”

The dynamic and interwoven nature of our physiology often makes the process of training seem more like art than science. On the surface, what we expect isn’t always what we get, and what we get isn’t always what we expect. For example, when you stop training, your fitness level decreases. However, depending on your previous training load, a break from normal training may actually result in increased fitness. Similarly, it’s expected that regular hard training will improve our fitness levels but, watch out — push too hard too often, and your fitness level will start to decrease.

The recognised training states are as follows:
Peaking: You are in ideal race condition! Your recently reduced training load is allowing your body to recover and fully compensate for earlier training. Be sure to think ahead, since this peak state can only be maintained for a short time.
Productive: Keep up the good work! Your training load is moving your fitness in the right direction. Be sure to plan recovery periods into your training to maintain your fitness level.
Maintaining: Your current training load is enough to maintain your fitness level. To see improvement, try adding more variety to your workouts or increasing your training volume.
Recovery: Your lighter training load is allowing your body to recover, which is essential during extended periods of hard training. You can return to a higher training load when you feel ready.
Unproductive: Your training load is at a good level, but your fitness is decreasing. Your body may be struggling to recover, so pay close attention to your overall health, including stress, nutrition and rest.
Detraining: You’ve been training much less than usual for a week or more, and it’s affecting your fitness. Try increasing your training load to see improvement.
Overreaching: Your training load is very high and has become counterproductive. Your body needs a rest. Give yourself time to recover by adding lighter training to your schedule.
No Status: You typically need a week or two of training history, including recent activities with VO2 max results from running or cycling, before we can determine your training status.

Heart Rate Variability (HRV)
Your heart doesn’t beat in a perfectly regular rhythm like a metronome. In fact, beat-to-beat variations in your heart rate are healthy and completely normal. Here’s what’s going on: Your heart’s controlled by your autonomic nervous system (ANS), or the involuntary part of your nervous system. There are 2 branches of the ANS; the sympathetic and parasympathetic. The sympathetic branch is active when you’re under some kind of stress. It’s the part of your body that puts all systems on alert. In contrast, the parasympathetic branch is more relaxed, and just hums along when you’re relaxed and not about to get side-swiped by a minibus taxi.

“Your heart rate variability a great way to assess how your body handles training and holistic stress, and also indicates how ready your body is for training or racing,” explains Roux. But he cautions, “You have to be diligent and measure this on a regular basis in order to make good use of it.”

Here’s a bit of biology to wrap your head around: When the sympathetic branch is more active, your heart rate typically increases, and it beats in more regular rhythm – meaning HRV decreases. On the other hand, when the parasympathetic branch is more active, your heart rate decreases, beating when it gets around to it to meet your body’s needs. In other words, HRV increases. Because of these characteristics, HRV is a great indicator of the balance between the activity of the 2 branches of the ANS, making it an indirect measurement of stress. Higher HRV means lower stress. However, although HRV decreases as you begin to exercise and continues to decline as you go harder, it still yields useful information even when you’re running fast.

HRV Stress Test (Stress Score in older products)
If you’re wondering whether your body’s ready for another hard run, or in need of something more casual, it might be time to check your stress score. When you’re fresh and rested inside and out, you’re better able to absorb the after effects of a tough workout. However, that same workout could be counterproductive when you’re tired, or on the verge of over training. Your stress score is calculated during a 3-minute test, during which your HRV is analysed. The resulting stress score is displayed as a number from 0 – 100, with a lower number indicating a lower stress state.

“What it does is look at the time between your heart beats and how much they differ,” explains Roux. “It’s a great way to assess how much stress your body’s still under and how ready you are for training. But for it to mean something, you need to keep track of it daily – you need to make a study of it.”

Note: When taking the HRV Stress Test make sure you remain standing, as this makes it more reliable. If you’re lying down, low or moderate levels of stress may not be revealed, but standing puts a slight load on your cardiovascular system. Although this load is subtle, it nonetheless causes a meaningful drop in HRV when you have a moderate amount of stress compared to very low levels – allowing you to accurately ascertain where you’re at. – (c) 2017 NavWorld

About The Author

Sean Woods

Originally a photographer for the Star newspaper in the bad old days, Sean Woods turned to writing after the first democratic elections in '94. The career shift paid serious dividends, culminating in him becoming associate editor for Popular Mechanics magazine with a number of technology writing awards under his belt. His interests include anything to do with boats, motorcycles and all those fancy tech gadgets that help the modern world go around.

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