The Best Way to Monitor Your Run Training Daily


Training effectively in distance running is not a simple matter. It starts off simple enough. When you’re inexperienced and unfit, just about any training decision you make will yield dividends. But the fitter and more experienced you become, and the closer your performance level comes to your ultimate genetic limit, the more difficult it becomes to find ways to refine your training to squeeze out still better performance.

To continue improving as a runner, it is helpful to accurately and quantitatively connect cause and effect in your training—that is, to determine how various training stimuli really affect your running performance. To do this you need reliable ways to measure training stress and running performance, ideally on a daily basis. With such tools you can continuously evaluate the effectiveness of the training patterns you try and discard those that are least effective while retaining and increasing your use of those that are most effective.

The TrainingPeaks performance management variables of training stress score (TSS), acute training load (ATL), chronic training load (CTL) and Training Stress Balance (TSB) are the most practically useful metrics for daily monitoring of run training stress. But what about daily monitoring of performance?  The difficulty in monitoring running performance in training has been that the only really reliable way to measure performance is through a test of maximal performance, and obviously it’s not a good idea to produce a maximal effort every day in training.  What has been needed is a practical way to measure performance in all types of workout and compare performance across all workout types, so that runners can monitor their performance daily in the normal course of training.

Running Index is a feature exclusive to Polar speed and distance devices that does just that.  It is essentially an estimate of a runner’s current VO2max, which is determined largely by genetic inheritance but is also affected by training.  Therefore tracking Running Index is a useful way for Polar users to monitor the effects of their training on their fitness level.

Polar speed and distance devices calculate Running Index by comparing heart rate and speed.  The device notes your heart rate and speed when you reach the 12-minute mark of a run.  It converts your heart rate into a percentage of heart rate reserve.  Your heart rate reserve is the difference between your maximum and resting heart rates.  This requires that you enter your maximum heart rate into the device before using it.  The more accurate this number is, the more accurate your Running Index scores will be.  The following formula is used to calculate your current running heart rate as a percentage of reserve: (current HR – resting HR) ÷ heart rate reserve.  The device then divides your speed by your percentage of heart rate reserve to yield an estimate of the maximum running speed you could sustain for 12 minutes, which will be close to your VO2max running speed.  Finally, the device converts this value into an estimate of your current VO2max, with scores typically ranging from 40 to 80 (the higher, the better).  After 12 minutes, the device continuously recalculates your Running Index as a rolling average up to the present moment, so that your final Running Index score at the end of the run may be slightly different from your initial score at 12 minutes.

For example, suppose that, 12 minutes into a run, your heart rate is 130 and your speed is 7 mph.  The device knows that your maximum heart rate is 186 bpm and your resting heart rate is 55 bpm, hence it also knows your heart rate reserve (186 – 55 = 131 bpm).  At 120 bpm, your heart rate is at 48 percent of reserve ([130 – 57] ÷ 131 = 0.55).  Your estimated speed at VO2max is your running speed divided by your percentage of heart rate reserve at that speed (7 ÷ 0.55), or 12.72 mph in this case.

Heart rate normally drifts slowly upward as any given pace is sustained, and the faster you run, the faster the drift.  Polar speed and distance devices filter out this drift as best they can in calculating Running Index scores.  They also try to filter out the effects of hills on pace.  However, they are not able to filter out the effects of environment conditions such as heat and terrain on heart rate, and this limitation affects the comparability of Running Index scores from different runs.

Nevertheless, testing has shown that Running Index scores are reasonably accurate predictors of actual VO2max.  But they are even better predictors of maximum running speed at VO2max, which is an even more important variable because it factors together both aerobic capacity and running economy and is therefore a better predictor of actual running performance than VO2max.  High Running Index scores result from having a relatively low heart rate at relatively high running speeds, and running economy makes a significant contribution to this capacity.  Indeed, tests have shown that Running Index scores predict running economy separately almost as well as they predict VO2max.

If you don’t use a Polar speed and distance device, you cannot get Running Index scores but you can still calculate estimated VO2max speeds from training data in individual runs.  Just note your speed and heart rate at an appropriate point in a run and perform the calculations above exactly as illustrated in the example given.  For the best results, note your speed and HR on level, smooth terrain at a relatively early point during running at a given speed.  During sustained, moderate-intensity runs, the 12-minute point is ideal.  When doing short, high-speed intervals, it’s actually better to note your heart rate at the end of a given interval, as heart rate tends to lag behind speed in such circumstances.

With basic knowledge of a spreadsheet application such as Microsoft Excel you can make a graph that plots your daily or weekly average Running Index against your ATL, CTL and TSB. Before long you will be able to identify trends. Your Running Index will tend to increase as your CTL and TSB increase and decrease as these values decrease. But beyond such gross observations you will also be able to make subtler cause-effect connections that enable you to refine and customize your training further. The possibilities are endless.  You might, for example, notice that your Running Index for interval workouts is consistently higher when they are preceded by two easy days instead of one. Or you might find that your Running Index for all of your key workouts is consistently higher when you use three-week step cycles (hard week/harder week/easier week) instead of four-week step cycles (hard/harder/hardest/easier).

Using the TrainingPeaks performance management variables and Running Index to productively connect cause and effect in your training requires that you pay close attention to the data you collect, apply solid analytical skills, and act on educated hunches.  It is most certainly not a way to automate the process of improving your training.  But it’s a step closer than any alternative. Try it!

About the Author

Matt Fitzgerald

Matt Fitzgerald is a journalist, author, coach and runner specializing in the topics of health, fitness, nutrition, and endurance sports training (read more about Matt on his blog). Matt uses TrainingPeaks to train, coach and deliver pre-built training plans for runners including training plans built specifically to be used with a Garmin Forerunner. View Matt's plans here.

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