Using a general purpose spreadsheet software package to estimate exponential plus constant model fits for blood lactate concentration versus work rate data

The objective of this analysis was to evaluate the accuracy of a standard spreadsheet software package to estimate best-fit parameters for an exponential plus constant model (y=a+b.e cx) applied to blood lactate concentration versus work rate data. During an incremental cycle test, blood lactate concentrations were measured in six endurance-trained athletes. A spreadsheet (Microsoft® Excel) and a dedicated curvefitting software programme (GraphPad Prism®) were used to obtain model coefficients, model fit parameters, interpolated work rate at a fixed blood lactate concentration (WR 4mmol/l) and work rate at a curve gradient of 1 mmol/l per watt (WRdy/dx=1). Model coefficients and model fit parameters were identical to the sixth decimal place for four subjects and differed by ≤0.000006 in two subjects. WR4mmol/l differed b