VO2 max is the defining measure of cardiorespiratory fitness and aerobic performance capacity. The ability to see your current fitness level and track changes over time is a game-changer. It can help you set appropriate goals, evaluate progress and determine the effectiveness of your training. It can also provide the motivation you need to keep going and to reach your goals. The Firstbeat analytics engine embedded in your Garmin watch reliably estimates your VO2 max by identifying, analysing and interpreting meaningful performance data during your run. The pace you are running is placed into the context of how hard your body is working to produce your performance. For the most part, the relationship between internal and external workloads (intensity of effort versus the pace you are running) is linear and stable. To run faster, your body needs to work harder. Smart analytics is capable of recognising good data to ensure that only the most meaningful parts of your performance are used to evaluate your fitness level. In practical terms, this means that you don’t need to worry about speeding up, slowing down, climbs, descents or stopping at intersections. You just run as you normally would, without the need for any special fitness testing protocols. Measured in terms of VO2 max, your fitness level combined with insight from your activity history provide valuable context for personalising training effect feedback, estimating recovery time, defining the optimal range for your weekly training load and determining your current training status. There are certain environments, however, in which your body must work harder than normal to keep up the pace. Good examples are runs performed in hot and humid conditions or at high altitudes. When paired with your compatible smartphone, This includes, for example, the feedback you get from the Training Status data screen, which interprets changes in your VO2 max in light of your current Training Load and activity history. If unrecognised and unaccounted for, a measurable decrease in aerobic performance capacity resulting from altitude or an unusually hot day could change your Training Status to Unproductive or Overreaching. In addition to letting you see how well your body is adjusting to the environment, recognising and accounting for the influence that environment has on your performance improves the reliability of other metrics. This means more meaningful feedback in a growing number of tough environments. This includes, for example, the feedback you get from the training status data screen, which interprets changes in your VO2 max in light of your current training load and activity history. Left unaccounted for, the effects of uneven terrain or a measurable decrease in aerobic performance from altitude or a hotter than normal environment could mistakenly identify your training status as unproductive or overreaching. Trail Running The ever-changing conditions of trail running pose significant challenges for both you and your performance data. Special attention is necessary to account for the extra effort that rugged and variable terrain often demands. On select Garmin GPS watches, this is now achieved by feeding accelerometer data into the Firstbeat analytics engine powering VO2 max estimation on your Garmin watch. This allows changing conditions underfoot to be incorporated into the analysis of performance versus how hard your body is working. How long does it take to acclimate to heat and humidity? The speed at which your body acclimates to elevated temperatures depends on several factors. One of the most significant factors is the difference between the conditions you are acclimating to and your normal environment. The bigger the change, the longer it takes to adapt. Another factor is the frequency and duration of your workouts and time spent outdoors in the new environment. The acclimation processes are triggered by your direct exposure to the environment. Evidence shows that prolonged daily outdoor exposures to challenging climates can produce the necessary adaptations in as little as 1 to 2 weeks. Athletes with a higher VO2 max typically adapt to challenging climates at a much faster rate, sometimes decreasing the acclimation period by as much as half. Physiological Adaptations That Result From Acclimation
- Physiological Adaptations That Result From Acclimation
- Improved sweating
- Improved cardiovascular stability (ability to sustain blood pressure and cardiac output)
- Better fluid-electrolyte balance
Race Time Prediction
How long it will take to finish a race has an impact on some important decisions. Pace, nutrition, attire and even your playlist can be affected by how long you will be out there running. Recognizing the value of this information, Garmin and Firstbeat have taken strides in the effort to provide reliable race time predictions you can trust. Your ability to produce energy aerobically, measurable terms of VO2 max, is a significant factor in your race performance. This knowledge, along with real-world data about the sustainability of effort across various intensities, provides the foundation of your predicted finish times for various distances. Once a VO2 max is established, your device can provide a target race time based on your current state of fitness. Projected race times can be viewed for 5K, 10K, half-marathon and marathon distances, which will get faster or slower as your fitness goes up or down. At all race distances, but especially in longer races such as marathons, there are many important and necessary factors for success that go beyond just aerobic fitness; that’s why it is important to complete proper training for an event to give yourself the best shot at reaching your predicted race times. And remember, these times are just predictions, but they give you a good idea of the kind of performances you can reasonably expect, given your physiological data. They also provide a terrific goal to try and reach.
For a real-time assessment of your current ability to perform, look at your performance condition. During the first 6 to 20 minutes of your run, this metric analyses pace, heart rate and heart rate variability. The resulting number is a real-time assessment of the deviation from your baseline VO2 max, with each point on the scale representing about 1% of your VO2 max. The higher the number, the higher you can expect to perform. Keep in mind that your results may vary a bit during your first few runs with a new device, since it’s still learning your fitness level. This will stabilise, and then checking your performance condition will become a reliable day-to-day indicator of your capability. In addition to the alert during the first part of your run, you can add performance condition as a data field to your training screens, and keep an eye on it as your run unfolds. The value may move around slightly as you encounter hills or strong winds, but it will trend down once you have been going hard for a while if the run starts to take a toll on you. This is an objective way to keep an eye on how your ability to perform is or isn’t declining as you go, because it’s telling you if your body is working harder than normal to run at your current pace. So, performance condition can give you a bit of an early “wall” warning and allow you to adjust your tactics before you hit that wall too hard.
If you’re like most people, you train because you want results. Because of how our bodies work, the type of training you do determines the type of results you can expect and the types of performances you will be well prepared for in the future. Training effect is the metric that gives you a sneak peek at how each training session is expected to impact your future fitness levels. Of course, to get the full benefits of your training, it’s important to incorporate a proper recovery schedule. One of the most common usages of training effect is to coordinate and balance workouts that maintain and improve your current fitness level (see VO2 max). Training effect builds over the course of your workout and is updated in real time. This means you can use it as an on-the-go resource to tailor your workout to your needs. You can push yourself harder when you are striving to improve and slow down before you wander into the overreaching range, where the results may not be what you wanted.
Aerobic Training Effect
Aerobic training: * Develops aerobic energy production * Utilization of fat for energy * Endurance and stamina * Prolonged performance capacity Available on select Garmin watches, this measures the aerobic benefit of exercise, which should correlate with the fitness improvement you expect to get from it. When you crush a difficult run, you’ve likely given yourself a bigger dose of aerobic exercise and, therefore, a bigger training effect. What good is this information for you? Well, training effect uses your heart rate to measure the accumulated intensity of exercise on your aerobic fitness and gives you a good indication of whether you’re maintaining your current fitness level or improving it. Aerobic training effect is the same as the original training effect feature offered on many earlier Garmin watches, except the scale has been modified slightly to account for — let’s face it — those really short or really easy activities that have no meaningful training effect. In other words, we added a “0” at the bottom of the scale. Technically speaking, aerobic training effect is the excess post-exercise oxygen consumption EPOC accumulated during exercise, mapped onto a 0-to-5 scale that accounts for your fitness level and training habits. Typically, as you get fitter, you need larger “doses” of exercise to continue seeing improvement. So, while an exercise session generating an EPOC of 60 ml-O2/kg might have given you a great training benefit when you were out of shape, it might not do very much for you once you have whipped yourself into wickedly good shape. Training effect reflects this reality by giving a higher number in the first case than in the second case. Note: The training effect scale for both aerobic and anaerobic is: 0 – None, 1 – Minor, 2 – Maintaining, 3 – Improving, 4 – Highly Improving, 5 – Overreaching.
Anaerobic Training Effect
Anaerobic training: * Develops anaerobic energy production * Sprinting abilities * Fatigue resistance * Maximal performance capacity While there isn’t a specific metric tied to it, the aspect of performance most easily associated with anaerobic training effect is your ability to perform and repeat sprints. The flow of a football game is a good point of reference here, where the activity of the game is punctuated with sudden flurries of high-intensity activity. Your body’s most efficient method of transforming fuel into energy requires oxygen, but sometimes your demand for energy exceeds the rate at which enough oxygen is immediately available. Luckily, your body has a backup process ready and waiting. While not nearly as efficient, the anaerobic energy process can jump into action and keep you going. The downside is that it becomes depleted quickly. Whereas aerobic training effect ties nicely with increasing your aerobic fitness level — expressed in terms of VO2 max — things are a little more complicated with accounting for improvements on the anaerobic side of things. By analysing both heart rate and speed (or power, in the case of cycling) the anaerobic training effect feature quantifies the anaerobic contribution to EPOC made during these periods of exertion. The higher the anaerobic training effect, the greater expected benefit to your anaerobic athletic capability. High-intensity intervals, for example, have been shown to improve several components related to your ability to perform, and anaerobic training effect quantifies this for you. However, the feature goes one step further. By analysing the type of workout you did, it can tell you more specifically how the workout helped you. For example, if it were detected that you completed several high-speed repeats, you might get an anaerobic training effect of 3.5 saying, “This activity improved your anaerobic capacity and speed due to several high-speed/power repeats.”
Training Effect Samples
The following table should give you an idea of the typical aerobic and anaerobic training effect you can expect from a good workout.
|Run Type||Typical Aerobic TE||Typical Anaerobic TE|
|Long, slow distance||2.0 - 3.0Maintaining Aerobic Fitness||0No Anaerobic Benefit|
|20-minute threshold||3.5+Improving Lactate Threshold||0No Anaerobic Benefit|
|Lactate threshold intervals||3.0+Improving Lactate Threshold||0 - 2.0Minor Anaerobic Benefit|
|Sprint intervals10 x 50m @|
150-200% VO2 max
|0 - 2.0Minor Aerobic Benefit||2.0 - 3.0Maintaining Speed|
|Speed intervals10 x 400m @|
100-105% VO2 max
|2.0 - 4.0Improving Aerobic Fitness||3.0 - 4.0Improving Economy and Anaerobic Fitness|
|Speed intervals10 x 400m @|
110-115% VO2 max
|2.0 - 4.0Improving VO2 Max||4.0+Highly Improving|
|800m race||2.0+Maintaining Aerobic Fitness||2.5+Maintaining Anaerobic Fitness|
|5K race||3.5+Improving VO2 Max||1.0 - 2.0Minor Anaerobic Benefit|
|10K race||4.0+Highly Improving VO2 Max||0.0 - 2.0Minor Anaerobic Benefit|
|Note that the above training effect values and phrases are illustrative examples. Your experience may differ depending on your personal training habits. For example, if you incorporate strides or faster fartleks into your distance runs, these can add an anaerobic training effect.|
|As with many Garmin Firstbeat features, it may take several training sessions for the watch to learn your fitness parameters and produce the most accuraute results. While the device is still learning about you, you may see uncharacteristic training effect values.|
Your lactate threshold is that specific level of effort or pace when fatigue accelerates. For a well-trained runner, this usually occurs when they’re at about 90% of their maximum heart rate corresponding to a pace somewhere between 10K and half-marathon race pace. For a less experienced runner, the lactate threshold is often below 90% of maximum heart rate. Select Garmin devices 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 a running pace and a heart rate level in beats per minute. For best results, it’s very beneficial to go for several runs after first taking the watch into use in order for your device to accurately learn your overall fitness level. Then, once this is well established, subsequent lactate threshold results will be more accurate than they might be initially. Historically, athletes hoping to utilise their lactate thresholds to personalise their training regimens needed blood testing to assess the amount of lactate accumulating during their training sessions. This process limited the number of athletes who had access to this valuable training information. The Firstbeat method of lactate threshold detection used in Garmin devices relies on the fact that your respiration rate — how hard you are breathing — can be detected through analysis of your heart rate variability. The process of inhalation and exhalation produces tiny changes in the interval between heartbeats (HRV). When these variations are decoded and combined with other performance data, your device can recognise the simultaneous changes in your heart rate to indicate when you are performing above your lactate threshold. How can this help you? Your lactate threshold is the single best determinant of your endurance performance capacity. As your ability to cover long distances at a faster pace increases, you’ll see increases in your lactate threshold. This metric is also a valuable resource for recognising the personal training zones that will boost your individual performance. That’s because your training will be based on real physiological state transitions in your body instead of arbitrary percentages of your maximum heart rate. Knowing your lactate threshold lets you train with more precision. Many coaches prescribe some running at lactate threshold as part of an overall training program. The lactate threshold feature in compatible Garmin devices helps you determine where your threshold is — without paying for an expensive lab test involving multiple blood samples.
Giving your body a chance to recover properly ensures you gain the maximum training benefit from your efforts. It also reduces injury risk and helps avoid the lasting consequences of overtraining syndrome. Recovery time is a countdown timer that reveals when you can expect to be fully recovered and ready to benefit from a substantial challenge. This countdown timer is updated at the end of each activity. The amount of time added to your recovery timer is determined through analysis of the duration and intensity of your recorded activity interpreted in light of your current fitness level and activity history. Any time remaining on your countdown timer at the start of a new activity is also taken into consideration. For the most part, similar performances require similar amounts of recovery time, but sometimes it takes longer than normal to bounce back. An unusually hard workout or race performance is a good example. Another is when there is a sudden increase in your 7-day training load compared to normal. The shock of rapidly increasing your training load in a short period of time can produce residual fatigue, simultaneously increasing injury risks and the length of time it takes to bounce back. A common misconception about recovery time is that it recommends complete rest until it has counted down to zero. Instead, recovery time is meant to indicate the time until you can expect to be sufficiently recovered for a hard workout. Many times an easy run or ride is OK – even beneficial – when your recovery time still shows considerable time remaining until complete recovery. The amount of recovery time normally prescribed after a workout is now being adjusted based on new consideration from training effect and training load data.
What is training load? Training load is an EPOC-based feature that helps you keep track of the combined strain of all your activities recorded with heart rate data. Your Garmin watch and Garmin Connect™ online fitness community provide views of your training load on a per-activity (for newer devices) and 7-day basis so you can see the immediate impact of each activity and your overall acute training load over the last week. Your chronic (4-week) training load is another load measure used internally in calculations for other features such as training status and training load focus. EPOC is an acronym for excess post-exercise oxygen consumption. It allows us to measure the impact of physical activity on your body in terms of the amount of restorative and adaptive work your body needs to perform after an activity. This is the work your body does to restore the dynamic equilibrium known as homeostasis. Oxygen consumed is an indirect indicator of the amount of energy your body uses to put itself back together and better prepare you for the next challenge. Measuring the amount of extra oxygen your body uses after a workout compared to normal is how physiologists and sports scientists get a clear picture of the impact of an activity. The Firstbeat analytics engine embedded in your Garmin watch capably predicts the accumulation of EPOC in real time by analyzing heartbeat data and applying advanced mathematical modeling and machine learning.
Training Load Focus
During your activity with compatible devices, your performance is analysed in real time to reveal the physiological impact of your activity and to understand the underlying efforts that produce it. This is achieved through understanding how various intensities and changes in intensity support and trigger adaptations in your body. Anaerobic training load (purple): The number on the top row and accompanying coloured bar show how much of your training load over the past 4 weeks was the result from anaerobic efforts. The key to increasing your anaerobic training load is doing activities that get your heart rate up quickly. These are typically high-intensity bursts of effort that are sustained for anywhere from several seconds to a couple of minutes at a time, mixed with low- to moderate-intensity recovery intervals during which your heart rate declines. Incorporating HIIT sessions into your programme is a good way to make sure you get enough of your training load from anaerobic efforts. • Key example: Sprint interval runs High aerobic training load (orange): The number on the middle row and accompanying coloured bar reveal how much of your training load of the past 4 weeks was the result of sustained moderately high- to high-intensity activity. This is the strain that accumulates during efforts where your heart rate was significantly elevated and you maintained that high level of intensity for a few minutes up to — in some cases — more than 30 minutes. • Key example: Tempo runs Low aerobic training load (light blue): The bottom number and accompanying coloured bar show how much of your training load over the past 4 weeks was produced during sustained low-intensity efforts. This is the portion of your training load that accumulates during “conversational pace” efforts, meaning that you are working but still able to talk and maintain a conversation. • Key example: Long slow runs
Making the Most of Training Load Focus
The training load focus data screen provides you not only with a graphical depiction of how your training load is distributed among the 3 major intensity categories, but with qualitative feedback as well.
- Shortage: You are lacking exercise in a training intensity category.
- Balanced: Your training is well distributed across different levels of intensity.
- Focus: Your training variety is reasonably well structured but is particularly focused in one area.
In addition to the above 3 categories of load focus feedback, it is also possible to get feedback that your overall training load is too low (“Below Targets”) or too high (“Over Targets”). Balance Is Needed for a Strong Foundation When your training load is both optimal and balanced, it means that you are active enough to support and gradually improve your fitness level, and that the composition of your activities is diverse enough to provide a solid foundation for future improvement. It means that your activities include enough time spent at high- and low-intensity aerobic efforts along with dynamic efforts to help enhance your explosive performance capabilities. Focus for Winning Every athlete knows that preparation is the key to success, and to be successful you must recognize and prepare for the unique demands of the challenge you face. With a balanced foundation in place, you can start to focus and guide the composition of your training load toward a performance profile that matches your ambition or phase of your periodization schedule. Confirming that your training is properly targeted through training load focus gives you confidence that you are on the right track. When understood and utilised properly, this data can be transformed into your personal road map for achieving your goals and performing at a high level in a wide variety of pursuits. You can easily see when your training activities are lacking in one or more areas, and once you have a strong foundation in place, you are able to shoot for the stars by ensuring the composition of your training activities match up with the specific real-world demands of the challenge you want to tackle. Training Load: Training Effect Label of Primary Benefit In newer compatible products, you can get an idea of how your run or ride affects your training load focus as soon as you save your activity. A new colour-coded label added to the training effect summary screen describes the primary benefit of what you have just done and where you can mostly expect it to contribute. Note that the background of these labels are colour coded (purple, orange and light blue) to match the anaerobic, high aerobic and low aerobic bars used for your training load focus. When a recorded activity has no meaningful impact in one of the intensity categories, or it cannot be identified, the label background is simply grey, and no descriptive text is displayed. At the bottom of this screen, you can also see the training load for the activity.
Heat and Altitude Acclimation
Environmental factors can have a substantial impact on your performance. At higher altitudes and in hot, humid conditions, your body is forced to work much harder than normal to produce the same performance as it would in more comfortable environments. However, exposure to these challenging conditions triggers a natural acclimation process. Acclimation is a physiological transition that helps you perform in new, more challenging conditions. Select Garmin devices automatically recognise when you are at higher altitudes or are being active in hotter conditions. Heat and altitude acclimation insights are provided based on activities performed above 800 meters (2,625’) and for temperatures above 22 C (72 F). This environmental information comes from a combination of GPS and weather reports from your paired compatible smartphone. Your body simply can’t and won’t change overnight. Acclimation takes time and requires repeated exposure to the environment. Once you leave challenging conditions behind, your body starts to return to normal. Your Garmin device understands this process and combines environmental and performance data to reveal your current acclimation status. Keeping tabs on it helps you adjust your expectations and performance goals. Automatically recognising and accounting for the relationship between environment and performance also ensure the integrity of your training data. Struggling to keep your normal pace during a heat wave doesn’t necessarily mean your cardiorespiratory fitness (VO2 max) has dropped. Similarly, needing to catch your breath during a trip to the mountains doesn’t mean your training has been unproductive. How long does it take to acclimate to heat and humidity? The speed at which your body acclimates depends on several factors. One of the most significant factors is the difference between the conditions you are acclimating to and your normal environment. The bigger the change, the longer it takes to adapt. Another factor is the frequency and duration of your workouts. Evidence shows that prolonged daily outdoor exposure to challenging climates can produce the necessary adaptations in as little as 1 to 2 weeks. Athletes with a higher VO2 max typically adapt to challenging climates at a faster rate, sometimes decreasing the acclimation period by as much as half. Specifics of Heat Acclimation Athletic performance involves transforming the energy stored in proteins, carbohydrates and fats. This produces heat. During intense physical activity, your body can rival a 1,000-watt space heater in terms of heat production. Getting rid of this excess heat is necessary for maintaining a normal, healthy body temperature. Circulating blood close to the skin allows heat to escape. This natural cooling process becomes more efficient as you sweat, because the evaporation of sweat has a natural cooling effect on your skin.
Not surprisingly, it’s much easier for your body to get rid of excess heat on a cool, crisp morning compared to a hot, humid summer afternoon. Your environment matters. Acclimation triggered by hotter climates focuses on improving the efficiency of your body’s natural cooling systems. This includes adaptations that allow you to sweat more and start sweating faster. It also includes changes that allow more blood to flow quickly just below the surface of your skin. Other key adaptations include changes to your cardiovascular system and electrolyte balance that add stability and help withstand the increased stress of hydration-dehydration cycles. Specifics of Altitude Acclimation At an elevation of 10,000’ (3,000 meters), the amount of oxygen in the air is only about 70% compared to sea level. This means your heart, lungs and circulatory system need to work much harder at higher altitudes to deliver a similar amount of oxygen to your muscles for aerobic energy production. Adaptations triggered by exposure to high-altitude environments focus on increased lung capacity and increasing the amount of oxygen carrying red blood cells in your blood supply. Pressure increases in the arteries running through your lungs, which forces the circulation of blood into areas of your lungs that aren’t normally used at lower altitudes. The additional red blood cells allow more oxygen than normal to be carried to your muscles with each heartbeat. The fact that these performance-boosting adaptations are not immediately reversed upon return to lower altitudes is the basis for high-altitude training for athletes.
Training status is the first feature offered by Garmin that truly analyses not only today’s run but also your longer-term training habits. This provides you with powerful insight into how your training is really going. If other metrics offer you a window into the process, training status knocks down the walls to let you enjoy the panoramic view. Is your current training intense enough, or long enough, to help improve your fitness? How do you know if you’re working hard enough to make a difference in the long run or if you’re not pushing yourself hard enough? Training status helps you make decisions about future training by automatically taking into account changes in fitness level, your current acute (7-day) training load and any change in training load with respect to previous training. In essence, it tells you the effectiveness of your current training and provides guidance to help you improve your training decisions. Provided by Firstbeat, the calculation utilises several dimensions of a personalised model of your physiology. Changes in your VO2 max fitness level in light of your recent training loads over time indicate the effectiveness of your 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. To explain in simple terms, when you stop training, your fitness level will decrease, but depending on your previous training load, a break from normal training routines may result in an increase in fitness level. 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 due to the overtraining phenomenon. As an example of how this works, imagine that you’ve been training consistently for a number of weeks, and your fitness with normal, small day-to-day ups and downs is nevertheless increasing. This trend is automatically identified and your current training will be classified as “productive.” Similarly, you could find yourself training very hard but with your fitness starting a pattern of decline. In this situation, your training would be identified as “overreaching,” and additional recovery will be recommended. The recognised training states are below. 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.
HRV Stress Test Stress Score in Older Products
If you’re wondering whether your body is ready for a hard run or in need of a lighter effort, 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 training effect from a tough workout. However, the same hard workout can be counterproductive if you’re tired or on the verge of overtraining. Your stress score is calculated during a 3-minute test during which your heart rate variability HRV is analysed. The resulting stress score is displayed as a number from 0 to 100, with a lower number indicating a lower stress state. This measurement helps you assess what level of activity your body is ready for. More accurate results are gathered by taking the test at the same time and under the same conditions every day (recommended prior to the workout, not after.) This also helps you get a feel for your own day-to-day and week-to-week variations. You are required to stand to take the HRV stress test, because that makes the test more sensitive to low and medium levels of stress. When you are lying down, moderate levels of stress may not be revealed, but standing puts a slight load on your cardiovascular system. That load causes a meaningful drop in HRV when you have a moderate amount of stress compared to very low stress.
Heart Rate Variability HRV
Your heart does not beat in a perfectly regular rhythm as would a metronome, and, in fact, beat-to-beat variations in your heart rate are healthy and normal. To understand more about how Garmin and Firstbeat use heart rate variability to give you better information about the state of your body, start with why heart rate variability exists. Your heart is controlled by your autonomic nervous system (ANS), which is the involuntary part of your nervous system. Furthermore, there are 2 branches of the ANS called the sympathetic and parasympathetic branches. The sympathetic branch of your ANS is active when you’re under some kind of stress. It is the part of your ANS that puts all systems on alert. By contrast, the parasympathetic branch is the more relaxed part that just hums along when you are relaxed and not about to be charged by a mountain lion. 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, and it beats when it gets around to it to meet the body’s needs, but not on such a strict schedule as when the sympathetic branch is in charge. 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 autonomic nervous system, and therefore it’s an indirect measurement of stress. Higher HRV means lower stress. There are many different statistical methods used to characterise HRV, but the HRV stress test (formerly called stress score) feature makes life a lot easier by putting your stress on an easy-to-understand 0-to-100 scale specifically designed to be another tool for you to assess how your body is doing and how it’s handling training stress and life stress. 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. Available on some Garmin devices, the lactate threshold feature uses a Firstbeat feature that looks for a point of increasing HRV that corresponds closely to your lactate threshold heart rate.
Excess post-exercise oxygen consumption is the phenomenon where for a period of time after exercise, your body will continue 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 to do some extra work to put things back to normal. In fact, the point of training is that after exercise, your body will build itself back up to normal and then some. It is the “and then some” — also called “supercompensation” — that makes you a little fitter and faster than you were before. Since the oxygen used by your body is related directly to the amount of energy it uses, the EPOC measurement is perfect for quantifying how much your body’s normal state (homeostasis) is disturbed by a session of exercise. In other words, EPOC is a great measure for exercise volume or dose, since it quantifies how much work your body had to do to get back to normal — and then some. Directly measuring EPOC requires fancy laboratory equipment and a lot of time. However, Firstbeat created a patented method for estimating EPOC from your heart rate data during exercise. These EPOC estimates are at the core of how we determine your training effects, weekly training load and training status.
Ground Contact Time
This is the amount of time in each step that you spend on the ground while running. Ground contact time is typically pretty short, so it is measured in milliseconds. In fact, ground contact time tends to be especially short for elite runners, they will often have ground contact times of less than 200 ms. Virtually all experienced runners have ground contact times under 300 ms, likely because they have learned to “pick up” their feet quickly and not to over-stride as they are landing. Over-striding describes a running style where the foot lands too far in front of the body leading to braking forces at impact and, typically, longer ground contact times.
Ground Contact Time Balance
By monitoring the balance between your left and right foot ground contact time (GCT), this measures your symmetry as you run. On your Garmin watch, it’s always displayed as a percentage greater than 50% with an arrow to the left or right, to show which foot is on the ground longer. For most people, a more symmetrical running form is preferable. Colour gauges on Garmin watches and Garmin Connect™ show how balanced you are compared to other runners. Many runners report that GCT balance tends to deviate farther from 50/50 when they run up or down hills, when they do speed work or when they are fatigued. Anecdotally, some runners also notice that injuries are reflected in greater imbalance.
Simply put, this is how many steps you take per minute, counting both feet. It’s a commonly measured running metric and can tell you a lot about your form. For example, at a given pace, quicker cadence and shorter stride length result in smaller forces at many places throughout the body, such as at the ankles, knees and hips. The reduced magnitude of these forces is widely believed by experts to also reduce injury risk. It’s clear that running cadence can be increased only so far, but for more injury prone runners in particular, working on increased cadence could be beneficial. An often-cited target for running cadence is 180 steps per minute, though taller runners tend to have somewhat slower cadence. Interestingly, higher cadence is also associated with lower vertical oscillation and shorter ground contact time.
Another key part of measuring your running form — stride length — is how far you travel with each left and right step. It’s shown at the end of your run or as an in-activity data field you can view as you run. Later, you can view this data in more detail on Garmin Connect™ to see how your stride length varies with your pace, cadence, elevation or other metrics. Your stride length is dependent on a number of factors, including body morphology, muscular strength and flexibility.
This reflects the amount of “bounce” in each step while you run. Measured at the torso, it tells you, in centimeters, how much distance you are travelling up and down with each step. Many running coaches believe that lower vertical oscillation is more economical, because less energy is wasted going up and down. Garmin has researched many runners of all different levels. In general, more experienced runners tend to have lower vertical oscillation. However, faster paces often come at a cost of somewhat higher vertical oscillation. Vertical ratio (see below) takes this into account. Another advantage of lower vertical oscillation is that it typically means less stress on the lower body at impact.
This reflects your running efficiency based on how well you propel yourself forward with each stride. Vertical ratio is the amount of “bounce” in your stride, divided by your stride length, then expressed as a percent. Since stride length is the horizontal movement of running, it’s the benefit of the action, whereas vertical oscillation is one of the energy costs of running. A low vertical ratio number indicates a small cost for a large benefit. That means more efficient running.
For years, elite cyclists have used power data as the most reliable way to measure the actual exercise load of their ride. Now you, too, can train with power on your runs by downloading the Running Power app from the Connect IQ™ store onto your compatible watch. The Running Power app accounts for multiple factors to provide a more accurate and responsive exercise load calculation. Developed by Garmin Labs, the Running Power app taps into metrics — such as pace, vertical oscillation, grade and even local wind conditions — to calculate the amount of power you’re applying at the ground as you run. When you know how much power you’re expending from minute to minute and mile to mile, you’re better able to pace yourself, which can help keep you from tiring out too quickly. Think of your body’s energy as the battery of your smartphone. You can turn up the screen’s brightness all the way, but, as a result, the battery won’t last as long. Or you can conserve battery by dimming the screen and getting a longer battery life. Likewise, by getting to know your body and its power output while running in different conditions, you can monitor this data to conserve your energy. For marathons and other long-distance runs, this can help you fine-tune your training and performance on race day. This running power model from Garmin determines the propulsive power applied at the road by considering the major components of the work done during running. These components, how they change and the data used to compute them are listed in the table below.
|Component of Running Power||What is it?||Source of Data Used to Compute|
|Kinetic Power||Power required to change your pace||Speed from the watch|
|Potential Power||Power required to run up or down a hill||Elevation data from the barometer on the watch|
|Vertical Oscillation Power||Power required for vertical oscillation on each step||Running dynamics from an HRM-Run™, HRM-Tri™ or Running Dynamics Pod|
|Horizontal Oscillation Power||Power required for horizontal oscillation on each step (you brake a bit when you hit the ground, then accelerate again as you push off)||Speed from the watch Running dynamics from an HRM-Run, HRM-Tri or Running Dynamics Pod|
|Wind/Air Power||Power to overcome air resistance — greater if running into a headwind and less if you are running with the wind at your back|
- Speed from the watch
- Heading from the watch
- Reported wind conditions from weather services
- Barometric data to detect local conditions
|Note: The equations to compute these components of running power also require some constant values such as your weight, acceleration due to gravity and the density of air.|
Following are examples of the contributions of the components of running power from a tester with cadence in the range of 162-182, vertical oscillation 6.2 – 8.9 cm, and GCT in the range of 262 – 296 ms. This chart isolates some of the elements that contribute to running power to illustrate their effects on the total. In reality, multiple elements move together. For example, as you speed up, your cadence typically also increases and your GCT decreases. On an uphill, you might slow down and your vertical oscillation may decrease. The app is continually accounting for all these elements to compute the total running power. So what does this mean for you? As you run, you will see that running power responds quickly when you speed up or slow down. You’ll also find that running power is higher when you’re running up hills than when you’re running at the same pace on flat ground. Similarly, running power will decrease when you run down a hill — though not by as much. In this way, you can use running power in addition to pace to help manage your effort over varying terrain. With the wind power feature enabled, the Running Power app can even help you gauge your effort when running on a windy day. Wind can have a large effect on the effort required to maintain your usual pace, which shouldn’t surprise you if you’ve ever run into a stiff headwind. The Running Power app uses your heading from GPS and reported wind conditions for your area, augmented by data from the barometer on your watch, to determine how much wind you’re likely experiencing. Try running back and forth on a windy stretch of road and you will see how much higher your power is when you run into the wind. If you typically run in sheltered areas, or you just don’t want the app to account for wind, simply disable this feature within the app settings in the Garmin Connect™ Mobile app. Many runners ask how running power correlates with heart rate. The 2 factors are certainly related as your muscles require more oxygen when they are generating more power. When viewing your charts post-run, you will see that when power goes up, heart rate follows a little while after. Avoiding this delay in response to changes (such as pace, hills or wind) is one of the advantages of using power rather than heart rate to gauge your effort when you’re running. Also, running power doesn’t depend on physiological factors — such as hydration level or how well-rested you are — the way heart rate does. Many runners are also surprised that their running power is so much higher than their bike power. In fact, running power is expected to be higher than bike power because metabolic efficiency is much higher for running (around 40-45%) than for cycling (around 20-25%). This means that athletes can convert the same amount of oxygen into more power when running than we can do when cycling. Or, thinking in terms of heart rate, we can produce more power for the same heart rate. This is primarily because when we run, we benefit from passive recoil of elastics elements such as tendons. Simply put, energy is stored when we land and returned as we push off. The same is not true for cycling. For more information on this, refer to our FAQs. To help you train with running power, you can choose to download apps to show Current Running Power, Lap Running Power, Last Lap Running Power, Average Power or all 4 of those at once. Some runners also use zones or alerts to monitor their running power. The app settings enable you to set up 5 custom running power zones and/or high and low running power alerts to help you keep your running power within a target range. If you already own the right Garmin devices, adding power to your run is free. All you need is a compatible Garmin watch and 1 of these 3 accessories: HRM-Run, HRM-Tri or the Running Dynamics Pod. Download the Running Power app now to get access to real-time power data.