EMG Antagonist Coactivation

Measure antagonist EMG amplitude relative to agonist and onset lag.

Description

Antagonist coactivation here uses antagonist RMS relative to agonist RMS.

Antagonist coactivation here uses antagonist RMS relative to agonist RMS. Onset lag separately reports antagonist timing relative to agonist.^[1]

Measure antagonist EMG amplitude relative to agonist and onset lag.

When to use EMG Antagonist Coactivation

Use this tool to measure antagonist EMG amplitude relative to agonist and onset lag.

Prepare the measured movement, timing, load or preassigned score requested. Keep protocols, units, paired measurements and caller-selected thresholds consistent.

How to use EMG Antagonist Coactivation and understand its results

Prepare the measured movement, timing, load or preassigned score requested. Keep protocols, units, paired measurements and caller-selected thresholds consistent.
Enter agonistRms, antagonistRms, agonistOnsetMs, antagonistOnsetMs using the field table and calculation rules, then run the tool.
Read coactivationPercent, onsetLagMs. The explanation below defines the units, signs, ordering and any flags or placeholder values.
If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.

Input field	Meaning	Value type; see rules below	Requirement
agonistRms	Agonist rms	number	Required
antagonistRms	Antagonist rms	number	Required
agonistOnsetMs	Agonist onset ms	number	Required
antagonistOnsetMs	Antagonist onset ms	number	Required

Enter positive agonist RMS, nonnegative antagonist RMS and finite signed onset ms. Return percentage and lag.

coactivation%=100antagonist/agonist; lag=antagonistOnset−agonistOnset

Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.

Output field	Meaning	Value type
coactivationPercent	Coactivation percent	number
onsetLagMs	Onset lag ms	number

json

{
  "input": {
    "agonistRms": 1,
    "antagonistRms": 0.3,
    "agonistOnsetMs": 100,
    "antagonistOnsetMs": 120
  },
  "output": {
    "coactivationPercent": 30,
    "onsetLagMs": 20
  }
}

Limitations and assumptions

No RMS/onset detection or muscle-normalization protocol is provided; percentages can exceed 100.

Numeric inputs must be finite. Follow the calculation-specific rules for overflow, underflow and exceptional cases. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors.

Alternative or Complementary methods

Use EMG Median Frequency Shift: Flag an EMG median-frequency decline against a caller-selected fatigue threshold. For a complementary task, use Hamstring Quadriceps Ratio: Calculate isokinetic hamstring/quadriceps torque ratio against caller limits.

References

EMG Antagonist Coactivation — tool.io

Similar or alternative tools

EMG Median Frequency Shift
Flag an EMG median-frequency decline against a caller-selected fatigue threshold.
Hamstring Quadriceps Ratio
Calculate isokinetic hamstring/quadriceps torque ratio against caller limits.