peterpen said:
Which tool is this? I typically only use SRMwin for downloading & marking intervals, but as one of the heretics who pays (limited) attention to HR, I'd be curious to check it out.
It's the one they simply call "SRM Analysis", which you can perform by clicking on the little icon on the toolbar that shows multi-colored diagonal lines. What is does is:
1) smooths the heart rate and power data using a rolling average the duration of which is specified via the "Analysis" tab of the "Options" pop-up;
2) performs a linear regression of smoothed heart rate vs. smoothed power, while time-shifting the data (to reflect the delay in the change in heart rate following a change in power output) to maximize the R^2 value. This generates a slope and intercept ("zero position") of the heart rate-power relationship, which is then used to predict the power that one could produce at a fixed heart rate of 150 beats/min (PWC150). The optimal "shifting" value is also given.
3) plots the smoothed heart rate vs. the smoothed power, using one of six different colors to represent the different sextiles of the ride (e.g., the 1st 10 min of a 1 h ride is plotted in yellow, the 2nd in red, etc...the ordering is shown by the little multi-colored bar found in the upper right hand corner of the screen).
Applied to the analysis of multiple rides, what you'd expect to find as your cardiovascular fitness improves would be a reduction in the slope and/or intercept of the regression line, resulting in an increase in the PWC150 value. In addition, the time-shift should decrease (although the magnitude of the expected improvement is quite small, and as such, easily overlooked when analyzing data collected in the field instead of a laboratory). Finally, you'd also expect to see less cardiovascular drift, such that the squiggly multi-colored line would remain closer to the regression line, versus the pink or blue parts being above and the yellow or red parts below.
Now for the ironic part: to refresh my memory re. all the details above, I called up one of my wife's recent workouts, which consisted of riding an ergometer at a fixed power of 200 W in our <65 deg F basement with a fan moving air over her at ~5 m/s. Regardless of whether I use the SRM Analysis tool or Friel's approach as implemented in the soon-to-be-released version 2.2 of WKO+, the amount of cardiovascular drift she experienced is minimal (e.g., <4% change in heart rate-power from 1st half to 2nd half of workout, which is how Friel suggests quantifying the amount of cardiovascular drift). Why is this ironic? Because she's been running, not riding, for the last ~2.5 mo, and as a result her cycling fitness has declined considerably...