Consider what a typical metabolic analysis software package offers regarding the determination of the gas exchange threshold. Almost invariably, you get only one method, typically the VCO₂ by VO₂ plot. You push a button and the program "magically" decides where the supposed breakpoint in the data is, shows you an estimate of the time and percentage of VO₂max at which this supposed breakpoint occured and, if you are lucky, plots regression lines through the before-the-breakpoint and after-the-breakpoint data. Then, you are allowed to manually shift the supposed breakpoint higher or lower to fit what "looks better" to you.

Those who have worked extensively with expired gases, particularly when these gases are collected on a breath-by-breath basis, know very well that this manual adjustment of the "automatically" determined breakpoint is very often necessary, as the erratic nature of ventilatory data make it very easy for statistical methods to lead to physiologically irrelevant and erroneous solutions. Perhaps most importantly, the typical metabolic analysis software packages do not reveal precisely what algorithm they use in making the "automatic" determination of the gas exchange threshold and do not disclose the full computational details of the iterative process that leads to this determination. An examination of the research literature that pertains to gas exchange analyses shows that there is a distinct lack of specificity in describing the methodology used to determine the gas exchange threshold. It seems that, at best, authors resort to using general and imprecise terms, such as "the V-Slope method", which have nearly no substantive meaning unless exact procedural details are described, and at worst, they admit that they relied exclusively on subjective and, thus, essentially impossible to precisely document and replicate criteria. Naturally, this situation can only lead to tremendous potential for inconsistency and confusion in the literature, as well as to justified scepticism toward the reliability and validity of any findings based on such poorly documented methodology.

Against this bleak backdrop, the features of WinBreak and the progress that they represent are astounding. Some of the features of WinBreak 3.7 include:

1. First, WinBreak is the only software program that is specifically designed to assist in the determination of the gas exchange threshold. The alternatives are (a) the continued reliance upon the very limited (due to the reasons explained above) methods for the determination of the gas exchange threshold incorporated into most of the commercial metabolic analysis software packages, (b) trying to obtain copies of computer code from researchers who, according to their publications, have developed computerized methods for determining the gas exchange threshold (unfortunately, for various reasons, most researchers are not willing to share their code), and (c) writing one's own computer program from scratch, an extremely time-consuming and, therefore, inefficient solution.

2. Second, WinBreak offers an automated and integrated analysis and data-presentation solution. All the analytical and graphical methods are incorporated into the program, so there is no need to have access to auxiliary mathematical software packages. All the common data-processing and graphing options related to the determination of the gas exchange threshold are available, usually with one click of the computer mouse.

3. Third, with WinBreak, there are no secret, arbitrary, or untested methods. All the methods and algorithms used in the program have been validated and published in the exercise physiology literature. This not only allows researchers and practitioners to have confidence in the methods on which they are basing their decisions, but also allows authors of scientific papers to document their methodologies in a simple, precise, and defensible fashion.

4. Fourth, WinBreak does not rely on a single method of determination. Idiosyncracies in data sets or excessive noise in the data can derail any statistical method of determination, leading to an erroneous solution. For this reason, WinBreak combines multiple methods of determination, thus giving users more options for viewing and analyzing their data. Specifically, WinBreak incorporates the 3 most popular and powerful graphical methods (the V-slope method, the method of ventilatory equivalents, and the Excess CO₂ method) and can place markers on each graph, indicating the location of the gas exchange threshold determined via the remaining two methods. Furthermore, in the V-slope module, in particular, users can select among five published algorithms (Jones & Molitoris, 1984; Orr et al., 1982; Beaver et al., 1986; Cheng et al., 1992; Sue et al., 1988). Of course, WinBreak also allows users to manually override the results of the "automatic" methods of determination if these results are deemed unsatisfactory. As the breakpoint is shifted higher or lower, the graphs are re-plotted and the regression slopes are re-calculated to enable users to observe the impact of their changes.

5. Fifth, to eliminate the uncertainty about the decision-making process that the program follows (i.e., how it arrives at a certain solution and why it considers this solution preferrable over all others), WinBreak provides the complete computational details for each method requested by the user. This output can be voluminous, particularly for breath-by-breath data, but it is important that users have access to it and be able to choose whether they wish to save it, print it, or delete it.

6. Sixth, to help users obtain a clear representation of their data and facilitate the process of determining the gas exchange threshold by minimizing some of the noise and clutter of metabolic data, WinBreak offers an extensive array of data manipulation options, including averaging, interpolation, outlier removal, and five smoothing options (running-window average, low-pass FFT filter, Savitzky-Golay least squares filter, cubic spline filter, polynomial from second to tenth order). With one click of the mouse, the data can revert to the original set.

7. Seventh, all graphs produced by WinBreak are presentation-quality and fully customizable (labels, fonts, axis scaling, symbol styles, line styles, sizes, and colors). Users can also turn some elements on or off (e.g., data series, grid, legend, etc.). Furthermore, WinBreak "memorizes" all the stylistic choices you make (separately for each graph, amounting to dozens of graph elements), so that you will not have to spend time re-customizing each graph.

8. Eighth, WinBreak can save all graphs in Windows^® Metafile (WMF) format. This format entails no loss of quality (as with bitmap formats, for example) and is compatible with all major word processors and presentation packages. In conjunction with WinBreak's graph customization options, this means that authors can prepare and incorporate graphs in their manuscripts in one easy step.

9. Ninth, WinBreak can produce not only printouts of its results in text format, but also graphical printouts accompanied by a summary of computational results. This type of printout is very convenient for hard-copy record-keeping, as it can provide an one-page overview of an analysis for future reference.

10. Tenth, WinBreak offers a flexible interface to import data from any metabolic analysis software package that can generate ASCII files and, given the fact that WinBreak can perform several data analysis and manipulation tasks that are difficult to replicate with common spreadsheet software packages, it is also important that WinBreak can save its data sheet in a variety of ASCII formats (e.g., comma-delimited, tab-delimited) and in the popular Microsoft^® Excel^® file format.

Finally, WinBreak, despite its technical sophistication and rich feature set, is very intuitive and easy to use, having a very short learning curve, is great as an educational tool for exercise physiology classes and laboratories, and its low price is a very welcome surprise!

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