The newest version of PC Coach offers improved options for graphing downloaded heart monitor data. As monitors (such as the S625X) record more types of data (speed, distance, altitude) in addition to heart rate, these graphing options become important in making the data more usable.

In this article, we'll show a few of the new graphing features of PC Coach, and how they can be used to make your workout data more meaningful. We will also show situations when certain options should NOT be used.

Look at the two graphs below. These graphs show the same workout as downloaded from two different monitors - the Polar S520 ( top graph ) and the new Polar S625X ( bottom graph ).

Editor's note: although this article is discussing graphs resulting from workouts performed with the Polar S520 and S625X, similar data would be downloaded from other S-series monitors (The S410 data downloaded would be similar to the S520 data, the data from the S720i or S725X would be similar to S625X data).

The S520X (top graph) captured a heart rate sample every 30 seconds (this sample rate was because the workout lasted between 30 minutes and 1 hour -the sampling rate is not an option on the S520). The S625X has captured samples for heart rate (red with fill), altitude (purple near the top) and pace (blue line lower middle area) every 5 seconds. With the S625X, you can choose to sample every 5, 15 or 60 seconds, depending on the granularity of data you want to see. Luckily, the S625X has enough memory that even while recording your data every 5 seconds, it has enough memory to store a dozen or so workouts.

The S625X speed values (for running workouts) are obtained from a new technology that uses accelerometers in a footpod mounted on your shoe. The S625X is the first Polar monitor to include this footpod. For more information on the S625X and Polar S1 footpod, click here.

The workout as downloaded from the S625X has three data elements: heart rate, altitude, and pace. Here, the new graphing options in PC Coach 4.3, described below as FILL, SMOOTHING and Y-AXIS CONTROL are useful to make the graph more understandable.

With the altitude values present (the blue line at the top of graph) it is clear that lap 5 was a hill sprint, and lap 6 was recovering coming back down the hill. Looking at the S520 download without altitude, it would perhaps be difficult to remember what was special about the workout, when looking at it weeks later.

Using Fill to differentiate the graph
With three data elements on the graph, it becomes useful to use one as a background. But the heart rate zones (color bands) are already a useful background. Fill refers to coloring the area under the data line. You can select fill values of 25, 50, 75 or 100%, which describe how 'transparent' it is. We used a 25% fill on the heart rate values, so the heart rate zones can still be seen 'behind' it.

Y axis control:
Note that the altitude graph hugs the top, out of the way of the other data. By comparison, the heart rate values are more centered in the graph ( top to bottom ). Forcing the altitude near the top was done by specifying manually entered max and min Y axis values for altitude, ( in this case 5000 to 5550, which covers the range of the local area) rather than choosing the automatic setting, which centers the data ( automatic setting was used for heart rate). You can elect to enter manual values, but still allow the Y axis to grow if needed to show the data. This is a useful option when you take a visit to the coast, and your altitude values for those workouts are suddenly outside the normal range for workouts done at home.

Y axis control could be used for the pace information as well, to use the space at the bottom of the graph more effectively. This is always the case when you know the boundaries of the data. That is, you won't be running a 3:00 mile pace today, so you could set that as the fixed Y-axis lower value.

Smoothing
Smoothing is an option that relates to how jagged the graph looks. It is difficult to look at a graph with a lot of jittery lines - you can miss the point of the story. In the above S625X graph heart rate and altitude were set to 'slight' smoothing. Sampling at 5 seconds, this almost never hides any important information. However, in the S520 graph, sampling at 30 seconds, smoothing was set to 'off'. Here is the same S520 graph with smoothing set to 'slight'.

Look at the hill sprint, which only lasted 3 minutes, and has only 6 data points during that time. In particular, look at the max heart rate at the end of the hill sprint, and compare it to the original graph above. The smoothing algorithm has covered up the maximum heart rate achieved. Rather than the accurate 173, it shows closer to 155. In general, the slower the sample rate, the less likely you can use smoothing.

For comparison, look at the effect of the pace information from the S625X. The original S625X graph above had smoothing set to 'off' for pace. Here is the same graph with pace smoothing set to 'slight'.

It is clear that the graph is much easier to look at. Smoothing actually does the work that your mind would otherwise have to do, to find an average among all those dots. And in general, with a 5 second sample rate, there is not much loss of information. But if you look closely, you can see that the pace drops more abruptly at the start of the hill sprint with smoothing off, and the fastest pace reported during that 3:00 is faster as well. These are things to keep in mind when using smoothing. It all depends on the type of workout, the sample rate, and what is important to learn from the graph.