GPS and Heart Rate Technology: The Endurance Training Revolution

Technology has become mainstream in all aspects of our daily lives and has slowly infiltrated the sport scene with decades of improvements. Considering all the tools available to chalk up our athletic lives to a bunch of quantitative data, I’d like to think I’ve kept it pretty simple. I operate with a GPS watch and a heart rate monitor. The heart rate monitor is a relatively new addition to my arsenal.

I log everything, religiously, so when I’m running 70, 80, and 90 miles a week, I can see how I’m trending, for worse or for better. I have two sensors on my bike, but unlike most of my high-tech competitors, I don’t own a cycling computer and often just strap my watch around my handlebars in a true, jimmy-rigged fashion. Nevertheless, I value the numbers as much as the next person. Here is how I have found this technology to be useful.

GPS and Pacing Feedback: Distance Running

One of the greatest factors separating experienced runners from the novice is the ability to pace accurately and consistently for an entire interval or workout. For well-trained runners, this becomes an almost innate, subconscious ability and often can be executed precisely by “feel.”

The sustained pace in long distance races is closely associated with a runner’s lactate threshold. At just a few seconds per mile above the lactate threshold, lactate and hydrogen ions begin to accumulate in the muscles, and without enough oxygen to support their clearance, a buildup ensues and fatigue is inevitable.

Race pace is often just below the lactate threshold for distances at or above a 5K, and training to improve this threshold becomes an integral part of program design. Training at lactate paces, just below the threshold zone, is the best way to improve the body’s ability to clear lactate from the muscles. This is a trainable aspect of an athlete’s physiology which is directly related to performance.

In other words, improved lactate clearance at a given running speed enables the runner to withstand a faster pace for the entire race. The threshold can be pushed higher and higher with progressive training, unlike VO2 max which has a harder ceiling based on predefined genetic factors.

So how does GPS come into play? Using a GPS watch as an inanimate pacer can truly be a game-changer in a runner’s ability to acquire an intuitive pacing ability. While this skill comes only from experience, the tool can greatly speed up the process of mastering internal pacing. GPS watches gives real-time pace, average run pace, and interval/lap pace options, so the data gives live feedback on how consistent a runner performs over the miles.

As a pacer, a GPS watch can be a game-changer in a runner’s ability to acquire intuitive pacing. Share on X

A study by Smith, Moran, and Foley (2013)² tested the benefit of GPS feedback on lactate threshold pacing in first-year collegiate distance runners. Researchers split the participants into an intervention group (using GPS devices) and a control group (no GPS devices) for a three-week lactate training experiment. Before the study started, researchers determined the threshold pace for each athlete with a fixed time-trial. None of the participants had previous experience with a GPS watch.

In the GPS group, the device significantly improved pacing in just three sessions. The study suggested that less experienced runners may benefit even more than more advanced runners due to an inverse relationship between improvements in pacing and the athlete’s experience level.

GPS as a Gauge for Overtraining

Overuse injuries from running are often caused by excessive progression in weekly volume or an overload of intensity. A study by Nielsen et al. (2013)¹ examined the use of GPS technology to determine whether training volume led to harmful effects on recovery and adaptation. In the study’s follow-up, thirteen of sixty runners who sustained injuries had performed a significantly higher training volume (31.6%) the week before their injury occurred, compared to a 22.1% increase in healthy participants. Researchers concluded that increasing weekly training above 30% significantly increased the risk of developing running related injuries.

GPS technology serves as a quantitative monitor to detect indications of overtraining. Share on X

The gold standard 10% rule is the currently accepted guideline for increasing training volume in a progressive yet safe manner. Although experienced athletes may tolerate a more aggressive increase if they’ve established a solid fitness base, GPS technology still serves as a quantitative monitor to detect indications of overtraining. I will elaborate more on heart rate technology later in the article.

GPS and Biomechanics: Swimming

Several GPS watches now have a multisport function which can track sport-specific parameters across multiple disciplines. I use a Garmin Forerunner 920XT in my training. The swim, bike, and run analytics have helped me fine tune my triathlon training to target specific biomechanical and economic issues that would be otherwise difficult to note as a self-coached athlete.

The swim metrics include distance, pace, stroke type identification, average and max stroke count per minute, average strokes per length, drill logging, and rest timers. When I’m specifically working on stroke cadence in the pool, I can use the stroke count features to monitor my efficiency. Triathletes often have a shorter, choppier swim stroke to account for the variability and unpredictability of the open water swim. Increasing stroke count per length in the pool, while maintaining speed, is important to monitor for improvements in stroke efficiency. The watch’s accelerometer tracks swim metrics when indoors, and the GPS capability is activated when swimming in open water.

GPS and Biomechanics: Cycling

On the bike, the 920XT measures average speed, maximum speed, distance, and elevation change. I can add compatible sensors to the bike for speed, cadence, and heart rate to provide advanced training data for cycling workouts.

Cadence has been especially important for me on the bike since I learn to develop leg power while still pushing high revolutions per minute. This also makes it easier when it’s time to train for intervals involving high-gear/low-cadence bouts alternated with low-gear/high-cadence bouts. The speed sensor is a bit redundant outdoors with the watch’s built-in GPS. But when winter calls to break out the indoor trainer, the speed sensor lets you know how you match up to your outdoor pacing while staying warm inside.

One compatible feature that I have not tapped into yet, for financial reasons, is the power meter. This is gradually becoming the gold standard for measuring cycling adaptation and leg power development. The higher power wattage you can push and pull at the same cadence/speed, the stronger you are as a cyclist.

The 920XT can display power metrics when paired with ANT+® power meters, including the Vector™ line of single- and dual-sensing pedal options. If you train with heart rate and a power meter, the 920XT can determine your estimatedVO2 max to help monitor changes in your fitness. The color gauge on the watch even shows how you rank against other athletes in your age group.

GPS and Biomechanics: Running

Aside from the basics of pace, time, and distance, the running dynamics include cadence, vertical oscillation, stride length, ground contact time, and more. A cadence of at least 180 steps per minute combined with optimal stride length correlates to faster race performances.
When I become fatigued late in a training run or race, I often shorten my stride and increase my cadence to overcome the over-striding and form breakdown which often accompany fatigue. The watch also features a built-in metronome (vibration or auditory) if cadence is something you or your athletes struggle with intuitively.

Vertical oscillation is the measure of the amount of “bounce” in each step. Too much bounce is wasteful of energy. Too little bounce often means the full backward extension of the hips is shortchanged, making the stride choppier and less cyclical. The amount of ground contact time can be a major differentiating factor between elite and sub-elite runners. When a runner spends less time on the ground with each foot contact, more energy returns to the legs for turnover rather than dissipating with a slow inefficiency.

The ground contact time feature (in conjunction with cadence) has been a game-changer for me. I have noticeably slower contact times when my body has not fully recovered from a previous workout, and cadence often lags behind the 180-steps per minute mark. My best race performances always follow optimal ground contact times when my legs are rested and primed for responsiveness.

Garmin has released a new feature that shows the ground contact time balance between the left and right legs. As a coach, I’ve found that most beginner and some advanced but less economical runners slightly favor one leg over the other. This may be due to a muscular (hip/glute) imbalance, leg length discrepancy, or compensation from an injury.

This feature helped me tremendously when coming off an acute ankle sprain after trail running. I had a significant imbalance between my healthy left foot and injured right foot contact times (54%/46%, respectively). As I healed, I saw that I favored my right foot less and less every day, and my numbers slowly regained equal balance at 50%/50%.

This is an invaluable tool for coaches and athletes to monitor changes in compensatory mechanisms which reveal inefficiencies otherwise unrecognizable without video analysis. These advanced run metrics are only measured when wearing the compatible HRM-Run™ chest strap. In my case, I use the HRM-Tri™ monitor and wear it in all three sport disciplines.

Heart Rate Training

I’ve grown to appreciate training with a heart rate monitor over the last year. While I do not design my training programs based on specific heart rate zones/intensities, I do check my heart rate during and after every workout to monitor my recovery status. Within the first few minutes of the run, my watch indicates my recovery status, either “Good” or “Fair.”

If my heart rate is higher than 145bpm on an easy run, I know my body has not recovered from my previous workout. Between intervals on the track, I can watch my heart rate fall back to a recovery zone and know I’m clearing lactate well and ready to go for the next bout.
Earlier in a training cycle, I often see my recovery time is not as efficient, especially with a short rest, but I can monitor my progress as the season goes on. If I see my heart rate climb and my breathing labor even at a slow pace on a trail run, I often check the altitude reading on the watch. “Oh, you just climbed 1,000-feet over the last mile and a half?” Well, that explains it.

After a workout, the watch recommends a recovery time before I should attempt my next hard day. As an aspiring elite athlete, I take this particular piece of information lightly, since we often need to take advantage of overloading the system to gain the benefits of super compensation on true recovery days. Often I accumulate my stress on two or three back-to-back hard days and take several recovery days before repeating the process.

Technology and Intuition

This article isn’t meant to be a plug for Garmin or this particular watch. There are many models available which have similar features and are just as beneficial. As an athlete, I’m grateful for the advances in technology which have helped me take my running and triathlon game to the next level. I’m excited to see where the wearable tech takes us in the next decade, and how it can further revolutionize the science of training.

With that said, I can’t stress enough the importance of not relying on external technology to become innately in-tune with your sport. There is something to be said for disconnecting from all forms of external feedback and data to simply feel the body working in its most natural way. I encourage my athletes (and myself) to perform most initial base conditioning runs, and often recovery runs, without the watch to become more aware of how their body feels and responds to the miles. This will make you a better, more intuitive athlete as much as, if not more than, the number-crunching game.

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References

1. Nielsen, R. O., P. Cederholm, I. Buist, H. Sørensen, M. Lind, and S. Rasmussen (2013). “Can GPS be Used to Detect Deleterious Progression in Training Volume Among Runners?” Journal of Strength & Conditioning Research, 27(6), 1471-1478.
2. Smith, J. W., M.F. Moran, and J.T. Foley (2013). “Effect of GPS Feedback on Lactate Threshold Pacing in Intercollegiate Distance Runners.” International Journal of Exercise Science, 6(1), 74-80.