Setting accurate high-speed GPS thresholds to avoid sub-optimal performance and increased injury risk

What consitutes a sprint? What is classified as “high speed running”? These are questions that are asked by sports scientists across the world when setting up speed thresholds but until recently, there isn’t much in the way of solid guidance based on peer-reviewed research. We spoke to Brock Freeman for this week’s Sportsmith Six and asked him six questions about how sports scientists can optimise their high-speed GPS threshold.

When an organisation purchases a GPS system, one of the first jobs is to set speed thresholds so they can categorise walking, high speed running, sprinting, etc. What are these thresholds, and where have people traditionally obtained this information? Are practitioners still using old Prozone thresholds?

Some practitioners are still using the predetermined thresholds that come with the GPS software. Individualisation is the fundamental principle of training that practitioners should adhere to in this instance.

Recently, information has become more readily accessible to allow for individualisation of speed zones. Most, if not all, sport science staff at the elite level are setting their own thresholds to determine the movement requirements of their sport. At the semi-professional level and lower this is likely a lot different. When I was working with an Under-18 state league Australian Football team in 2020, we were locked to the manufacturer recommendations of 4 m/s for high speed running and 6 m/s for sprinting by the regulating body.

It’s no secret that these thresholds are very loosely defined. Alice Sweeting and colleagues wrote a really good review of this topic in 2017 entitled “ When is a sprint a sprint? A review of the analysis of Team-Sport Athlete Activity profile” that outlines how ambiguous these thresholds are.

From an absolute perspective, high speed running can start as low as 3.5 m/s or as high as 5.5 m/s, which is quite a big range. We can see the same range of thresholds for sprinting, where it can start at 5 m/s, or it can start at 7 m/s.

It’s generally accepted that relative thresholds are a better method to categorise intensity, but this is still highly variable. Across field sports, you will typically see anything at or above 50% of maximum velocity (V_max) being defined as high speed running, and 70% V_max or greater to define sprinting. In a practical setting, there are certainly professional teams using a threshold of 90% V_max to trigger a sprint. However, personal experience would suggest this isn’t well reflected in academia (we know that practice often leads publishing, though), or in semi-pro / amateur settings.

What potential problems can arise if practitioners use inaccurate thresholds?

This comes down to two key factors: sub-optimal performance and increased injury risk.

A lot of the team sport athletes I have worked with have V_max­ of 8.5 – 9.5 m/s. If the athlete can run 9 m/s and we set 7 m/s as our sprint threshold, we’re not accurately capturing their “sprint.” Objectively, it’s only 78% V_max. And from a subjective visual interpretation, it looks very different from an all-out sprint effort. Therefore, if we use that value to monitor training and inform session design, we can’t say that we are providing an adequate stimulus to promote speed development.

Following on from this, the work demands and forces that lower body muscles and tendons are required to withstand and produce substantially increase above 80% V_max. ­If we’re coming in beneath that, we are probably not providing an adequate stimulus to condition and protect those muscles to the demands of sprinting. Many coaches and academics argue that maximum speed isn’t as important as acceleration, and that the risk outweighs the reward. If I use Australian Football as an example, acceleration frequently creates space for players to attack and to defend, but the rare instances where players need to express maximum speed occurs at pivotal moments of a competition, such as a line breaking running goal or a dramatic chase down tackle. If athletes never prepare to run their fastest, they won’t have the ability to do it, and the risk of injury will go up if they try.

Based on your research, how should practitioners use thresholds more accurately?

We should be clear on what a fair interpretation of a sprint is. In a perfect setting, we would assess our athlete’s maximal speed regularly using radar or other timing systems across several different days to establish what their maximum running speed is. Obviously, that’s not feasible for everyone.

What we can do, though, is use GPS to get a value that’s going to be close to the individual’s maximum running speed. This might happen at the end of a warm up, and we can do this every couple of weeks to keep track of how the value is changing. There is an error associated with using GPS, but this information is readily available, and we can account for that when we set our thresholds.

The next thing we need to do is determine what we want from our thresholds. If we look at sprinting, I’d suggest that 90% V_max is a good starting point. It’s fast enough that we are capturing activity where the demands on the lower body are increasing rapidly, and it’s a better (but not perfect) indication of whether athletes might be improving their speed qualities. We might also consider using a secondary threshold at 95% V_max if the session goal is biased towards achieving maximum speed.

The rest of the thresholds should be dictated by the goal of the session. If the training goal is to develop aerobic qualities, and you know what the athlete’s Maximal Aerobic Speed / Critical Speed / vVO_2max is, then you can adjust your thresholds to quantify this.

If the software that accompanies the units doesn’t allow for individualisation, a set of different thresholds might work in this instance. For example, you could have 4 m/s, 4.5 m/s and 5 m/s thresholds for a group of 15, but the 4 m/s might only really apply to five of them, 4.5 m/s for the next five, and 5 m/s for the final five athletes.

Based on the thresholds you recommend, how much variation is there between individuals? Should that be taken into account or are we able to generalise to an extent to get what we need?

We are actually putting together a study in this area at the moment, where we seek to establish how much V_max varies between sessions and compare this with the variation in lower body strength and lower body power.

Additionally, we should be aware of the typical error associated with assessment of maximum speed. The more you can account for that, the better off you will be.

If you are regularly tracking the maximum speed of your athletes over a season, this will also help to provide some context to the thresholds and the numbers that the athletes are producing. For a while now we have been generalising to get what we need, and it has worked to some extent, but we can always improve upon this. It’s also important to consider that we should look at other factors that might explain some of the metrics that athletes might produce, such as soreness, fatigue, motivation to train, etc. Perhaps if it’s GD+2, the interest in the 95% V_max threshold isn’t as important as it might be on GD-2.

Although maybe outside of your current research, are there any other thresholds commonly used within GPS systems that practitioners should approach with caution, pending more scientific rigor behind them?

One area that could improve is the distinction between high speed running and high intensity running.

Often these two terms are used interchangeably, but I’m not convinced that they are the same thing. To me, high speed indicates that the athlete is moving fast and producing a lot of force, whereas I associate high intensity with the metabolic cost of running. The example I would use is that 4 m/s for a team sport athlete could be considered high intensity running, but it’s definitely not high speed running as it’s likely well under 50% V_max. A lot of this probably stems from the descriptors used in time-motion studies before GPS was more common.

It all goes back to what we want to measure. If we need to know if the athlete needs to improve from a metabolic perspective, the terminology of high intensity running could be more appropriate and reflected by a threshold relevant to field or lab based measures. If we need to know if the athlete has been sufficiently exposed to a speed stimulus, then high speed running is more appropriate, and the threshold should be fast.

As I suggested above, using different thresholds for different adaptations is one way we could improve upon this.

What are the biggest mistakes you see young practitioners/sports scientists make and what advice would you give them to help?

For those working in the field, it’s easy to get caught up in making things new and flashy, but this rarely works in the perfect setting, let alone in the very tight constraints of team sports. If you design your practice with the principles of training in mind, you can’t go too far astray.

Similarly, when choosing whether to implement new technology or not, consider how easily it can align with your program design. No one wants to spend multiple hours combing through hundreds of metrics, especially when you when can get that information from one or two simple measures. The best practitioners I’ve seen do this really well and combine it with an athlete centred approach.

For academics seeking to answer questions that are important to the industry, I would suggest we follow the advice of one of my Ph.D. supervisors, Warren Young. Good research starts with a good question and good questions come from coaches.

Listen to what coaches are saying and the problems they are facing, and then formulate your research questions off of that.