Table 1 lists the minimum root-mean-square (rms) error ||H_data-H_fit|| (where ? x ? = ? t = 1 N ( x t ) 2 / N for a time series xt of length N) for several static and dynamic fits of increasing complexity for the data in Fig. 1. Not surprisingly, Table 1 shows that the rms error becomes roughly smaller with increased fit complexity (in terms of the number of parameters). Rows 2 and 5 of Table 1 are single global linear fits for all of the data, whereas the remaining rows have different parameters for each cell and are thus piecewise linear when applied to all of the data.
We shall very first work at static linear matches (first four rows) of your own form h(W) = b·W + c, in which b and you will c is actually constants that overcome the latest rms error ||H_data-h(W)||, that’s available effortlessly because of the linear minimum squares. Static habits don’t have a lot of explanatory energy however they are easy carrying out points in which limitations and you can tradeoffs can be easily recognized and you can knew, therefore only use procedures that in person generalize so you’re able to active models (shown after) with more compact boost in complexity. Line step 1 of Table step 1 ‘s the superficial “zero” match b = c=0; row 2 is the best all over the world linear fit with (b,c) = (0.thirty five,53) that is used to help you linearly scale new tools of W (blue) to help you most readily useful match the latest Hour study (red) from inside the Fig. 1A; row 3 is a beneficial piecewise lingering match b = 0 and you can c being the mean of any data lay; line cuatro is the best piecewise linear fits (black colored dashed contours during the Fig. 1A) with slightly other thinking (b,c) regarding (0.forty-two,49), (0.14,82), and (0.04,137) at 0–50, 100–150, and you can 250–3 hundred W. The new piecewise linear design for the line 4 has actually quicker mistake than the global linear fit in row 2. At the large workload peak, Hr for the Fig. step 1 will not arrive at steady-state towards date measure away from the new experiments, the new linear static complement is absolutely nothing a lot better than lingering match, and thus these study are not noticed after that to own static matches and you will habits.
Each other Dining table step one and you will Fig. step one indicate that Hr reacts a little nonlinearly to different quantities of workload stresses. This new strong black colored contour inside the Fig. 3A reveals idealized (i.e., piecewise linear) and you will qualitative however, normal viewpoints to have h(W) worldwide that will be similar to the static piecewise linear matches at the the 2 straight down watts membership inside Fig. 1A. The change in the slope away from H = h(W) which have increasing workload is the best sign of modifying HRV and you may happens to be our initially interest. A great proximate lead to try autonomic neurological system equilibrium, however, we have been trying to find a further “why” when it comes to entire system limits and tradeoffs.
Static analysis of cardiovascular control of single e timidi aerobic metabolism as workload increases: Static data from Fig. 1A are summarized in A and the physiological model explaining the data is in B and C. The solid black curves in A and B are idealized (i.e., piecewise linear) and qualitatively typical values for H = h(W) that are globally consistent with static piecewise linear fits (black in Fig. 1A) at the two lower workload levels. The dashed line in A shows h(W) from the global static linear fit (blue in Fig. 1A) and in B shows a hypothetical but physiologically implausible linear continuation of increasing HR at the low workload level (solid line). The mesh plot in C depicts Pas–?O2 (mean arterial blood pressure–tissue oxygen difference) on the plane of the H–W mesh plot in B using the physiological model (Pas, ?O2) = f(H, W) for generic, plausible values of physiological constants. Thus, any function H = h(w) can be mapped from the H, W plane (B) using model f to the (P, ?O2) plane (C) to determine the consequences of Pas and ?O2. The reduction in slope of H = h(W) with increasing workload is the simplest manifestation of changing HRV addressed in this study.