Analyze work loop object to compute work and power outputSource:
Compute work and power output from a work loop experiment on a per-cycle basis.
workloopobject of class
muscle_stimthat has been passed through
select_cycles. See Details.
FALSE, the full analyzed workloop object is returned. If
TRUEa simpler table of net work and power (by cycle) is returned.
Gear ratio, set to 1 by default
Velocity multiplier, set adjust the sign of velocity. This parameter should generally be either -1 (the default) or 1.
Critical frequency (scalar) for low-pass filtering of velocity via
Additional arguments potentially passed down from
The function returns a
list of class
that provides instantaneous velocity, a smoothed velocity, and computes work, instantaneous power, and net power from a work loop experiment. All data are organized by the cycle number and important metadata are stored as Attributes.
list, each entry is labeled by cycle and includes:
Time, in sec
Length change of the muscle, corrected for gear ratio, in mm
Force, corrected for gear ratio, in mN
When stimulation occurs, on a binary scale
Cycle ID, as a letter
Instantaneous velocity, computed from
Positionchange, reported in meters/sec
Instantaneous velocity, after low-pass filtering, again in meter/sec
Instantaneous power, a product of
Filt_velocity, reported in J
The percent of that particular cycle which has elapsed
In addition, the following information is stored in the
analyzed_workloop object's attributes:
Frequency at which stimulus pulses occurred
Frequency of oscillations (assuming sine wave trajectory)
Total number of oscillatory cycles (assuming sine wave trajectory) that the muscle experienced.
Specifies what part of the cycle is understood as the beginning and end. There are currently three options: 'lo' for L0-to-L0; 'p2p' for peak-to-peak; and 't2t' for trough-to-trough
Amplitude of length change (assuming sine wave trajectory)
Phase of the oscillatory cycle (in percent) at which stimulation occurred. Somewhat experimental, please use with caution
Logical; whether position inversion has been applied)
The units of measurement for each column in the object after running this function. See Warning
Frequency at which samples were collected
Additional information from the header
Units from each Channel of the original ddf file
Protocol in tabular format; taken from the original ddf file
Specific info on stimulus protocol; taken from the original ddf file
Number of sequential pulses within a stimulation train
Timing offset at which stimulus began
Gear ratio applied by this function
Time at which file was last modified
Which cycles were retained, as numerics
Simple table showing work (in J) and net power (in W) for each cycle
Please note that
select_cycles() must be run on data prior to
using this function. This function relies on the input
object being organized by cycle number.
muscle_stim object (
x) must be a
preferably read in by one of our data import functions. Please see
as_muscle_stim() if you need to manually construct
muscle_stim object from a non .ddf source.
The gear ratio (GR) and velocity multiplier (M) parameters can help correct
for issues related to the magnitude and sign of data collection. By default,
they are set to apply no gear ratio adjustment and to positivize velocity.
Instantaneous velocity is often noisy and the
vel_bf parameter allows
for low-pass filtering of velocity data. See
signal::filtfilt() for details of how filtering is achieved.
Please also be careful with units! Se Warning section below.
Most systems we have encountered record Position data in millimeters
and Force in millinewtons, and therefore this function assumes data are
recorded in those units. Through a series of internal conversions, this
function computes velocity in meters/sec, work in Joules, and power in
Watts. If your raw data do not originate in millimeters and millinewtons,
please transform your data accordingly and ignore what you see in the
Josephson RK. 1985. Mechanical Power output from Striated Muscle during Cyclic Contraction. Journal of Experimental Biology 114: 493-512.
Other data analyses:
Other workloop functions:
library(workloopR) # import the workloop.ddf file included in workloopR wl_dat <-read_ddf(system.file("extdata", "workloop.ddf", package = 'workloopR'), phase_from_peak = TRUE) # select cycles 3 through 5 via the peak-to-peak definition wl_selected <- select_cycles(wl_dat, cycle_def = "p2p", keep_cycles = 3:5) # run the analysis function and get the full object wl_analyzed <- analyze_workloop(wl_selected, GR = 2) # print methods give a short summary print(wl_analyzed) #> File ID: workloop.ddf #> Cycles: 3 cycles kept out of 6 #> Mean Work: 0.00308 J #> Mean Power: 0.08474 W #> # summary provides a bit more detail summary(wl_analyzed) #> # Workloop Data: #> #> #> File ID: workloop.ddf #> Mod Time (mtime): 2023-03-06 07:19:19 #> Sample Frequency: 10000Hz #> #> data.frame Columns: #> Position (mm) #> Force (mN) #> Stim (TTL) #> Cycle (letters) #> Inst_Velocity (m/s) #> Filt_Velocity (m/s) #> Inst_Power (W) #> Percent_of_Cycle (NA) #> #> Stimulus Offset: 0.012s #> Stimulus Frequency: 300Hz #> Stimulus Width: 0.2ms #> Stimulus Pulses: 4 #> Gear Ratio: 2 #> #> Cycle Frequency: 28Hz #> Total Cycles (peak-to-peak): 6 #> Cycles Retained: 3 #> Amplitude: 1.575mm #> #> #> Cycle Work Net_Power #> a A 0.002785397 0.07639783 #> b B 0.003147250 0.08661014 #> c C 0.003305744 0.09122522 # run the analysis but get the simplified version wl_analyzed_simple <- analyze_workloop(wl_selected, simplify = TRUE, GR = 2)