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Detect the spastic catch on a single passive stretch

Source: R/spasticity-tardieu.R
tardieuStretch.Rd

Locates the Tardieu "catch" on one passive-stretch joint-angle trace and returns the catch angle (R1). The catch is detected from a reflex EMG burst (envelope crossing a baseline mean + threshold_sd * SD threshold), from a velocity arrest (angular velocity dropping below catch_fraction of its peak after the fastest stretch), or from both.

Usage

tardieuStretch(
  angle,
  emg = NULL,
  sampling_rate,
  emg_sampling_rate = sampling_rate,
  onset = c("emg", "velocity", "both"),
  baseline_sec = 0.5,
  threshold_sd = 3,
  catch_fraction = 0.5,
  envelope_ms = 50
)

Arguments

angle

Numeric joint-angle trace over the stretch (degrees; increasing as the joint is stretched).

emg

Optional EMG of the stretched muscle (numeric); enables the EMG reflex-onset trigger.

sampling_rate

Angle sampling rate (Hz).

emg_sampling_rate

EMG sampling rate (Hz); the EMG is resampled onto the angle time base with alignEMGtoMoCap(). Default = sampling_rate.

onset

Catch trigger: "emg", "velocity" or "both" (EMG-preferred, velocity fallback).

baseline_sec

Baseline window (s) for the EMG threshold (default 0.5).

threshold_sd

EMG onset threshold in baseline SDs (default 3).

catch_fraction

Velocity-arrest fraction of peak velocity (default 0.5).

envelope_ms

EMG RMS-envelope window in ms (default 50).

Value

An S3 tardieu_stretch list: catch_angle (R1), catch_index, catch_velocity, peak_velocity, rom_max/rom_min, reflex_latency_ms (EMG onset relative to stretch onset), onset_method.

See also

tardieuScore(), reflexThreshold()

Examples

fs <- 200; t <- seq(0, 0.6, by = 1 / fs)
angle <- ifelse(t <= 0.25, 25 * t / 0.25, 25 + 5 * (t - 0.25) / 0.35)
tardieuStretch(angle, sampling_rate = fs, onset = "velocity")$catch_angle
#> [1] 25.07143