W': work capacity above critical power/speed.

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

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? If `TRUE`

computation is performed in parallel
using the backend provided to `foreach`

. Default is
`FALSE`

.

...

Currently not used.

An object of class `trackeRWprime`

.

#' 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 rationale can be applied by setting the argument
`meanRecoveryPower`

to `TRUE`

. Note that this uses
information from all observations with a power output below
critical power, not just those prior to the current time point.

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.

```
# NOT RUN {
data('runs', package = 'trackeR')
wexp <- Wprime(runs, session = c(11,13), cp = 4, version = '2012')
plot(wexp)
# }
```

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