trackeR (version 0.0.3)

Wprime: W': work capacity above critical power.

Description

Based on the critical power model for cycling (Monod and Scherrer, 1965), W' (read W prime) describes the finite work capacity above critical power (Skiba et al., 2012). While W' is depleted during exercise above critical power, it is replenished during exercise below critical power. Thus, it is of interest how much of this work capacity has been depleted and not yet been replinished again, named W' expended, or how much of this work capacity is still available, named W' balance. This principal is applied to runners by subsituting power and critical power with speed and critical speed, respectively (Skiba et al., 2012).

Usage

Wprime(object, session = NULL, quantity = c("expended", "balance"), w0, cp, version = c("2015", "2012"), meanRecoveryPower = FALSE, parallel = FALSE, cores = NULL, ...)

Arguments

object

A trackeRdata object.

session

A numeric vector of the sessions to be used, defaults to all sessions.

quantity

Should W' "expended" or W' "balance" be returned?

w0

Inital capacity of W', as calculated based on the critical power model by Monod and Scherrer (1965).

cp

Critical power/speed, i.e., the power/speed which can be maintained for longer period of time.

version

How should W' be replenished? Options include "2015" and "2012" for the versions presented in Skiba et al. (2015) and Skiba et al. (2012), respectively. See Details.

meanRecoveryPower

Should the mean of all power outputs below critical power be used as recovery power? See Details.

parallel

Logical. Should computation be carried out in parallel?

cores

Number of cores for parallel computing. If NULL, the number of cores is set to the value of options("corese") (on Windows) or options("mc.cores") (elsewhere), or, if the relevant option is unspecified, to half the number of cores detected.

...

Currently not used.

Value

An object of class trackeRWprime.

Details

Skiba et al. (2015) and Skiba et al. (2012) both describe an exponential decay of W' expended over an interval [t_i-1, t_i) if the power output during this interval is below critical power: W_exp (t_i) = W_exp(t_i-1) * exp(nu * (t_i - t_i-1)). However, the factor nu differs: Skiba et al. (2012) describe it as 1/tau with tau estimated as tau = 546 * exp( -0.01 * (CP - P_i) + 316. Skiba et al. (2015) use (P_i - CP) / W'_0. Skiba et al. (2012) and Skiba et al. (2015) employ a constant recovery power (calculated as the mean over all power outputs below critical power). This rational can be applied by setting the argument meanRecoveryPower to TRUE. Note that this employes information from the all observations with a power output below critical power, not just those prior to the current time point.

References

Monod H, Scherrer J (1965). "The Work Capacity of a Synergic Muscular Group." Ergonomics, 8(3), 329--338. Skiba PF, Chidnok W, Vanhatalo A, Jones AM (2012). "Modeling the Expenditure and Reconstitution of Work Capacity above Critical Power." Medicine & Science in Sports & Exercise, 44(8), 1526--1532. Skiba PF, Fulford J, Clarke DC, Vanhatalo A, Jones AM (2015). "Intramuscular Determinants of the Abilility to Recover Work Capacity above Critical Power." European Journal of Applied Physiology, 115(4), 703--713.

Examples

data("runs", package = "trackeR")
wexp <- Wprime(runs, session = c(11,13), cp = 4, version = "2012")
plot(wexp)