Limb Symmetry Index

Calculate limb symmetry index from the supplied measurements.

Description

Limb symmetry index expresses an involved-limb result relative to an uninvolved reference.

Limb symmetry index expresses an involved-limb result relative to an uninvolved reference. Measurement direction matters when lower scores represent better performance.^[1]

Calculate limb symmetry index from the supplied measurements.

When to use Limb Symmetry Index

Use this tool to calculate limb symmetry index from the supplied measurements.

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

How to use Limb Symmetry Index 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 involvedLimbResult, uninvolvedLimbResult using the field table and calculation rules, then run the tool.
Read limbSymmetryPercent. 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
involvedLimbResult	Involved-limb result	number	Required
uninvolvedLimbResult	Uninvolved-limb result	number	Required

Enter finite results with nonzero reference. Signed values and percentages above 100 are accepted; return percent.

symmetry%=100involved/uninvolved

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

Output field	Meaning	Value type
limbSymmetryPercent	Limb symmetry (%)	number

json

{
  "input": {
    "involvedLimbResult": 90,
    "uninvolvedLimbResult": 100
  },
  "output": {
    "limbSymmetryPercent": 90
  }
}

Limitations and assumptions

The tool does not select the better side, invert timed measures or establish return-to-sport readiness.

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 Jump Phase Asymmetry: Calculate bilateral force asymmetry separately for propulsion and landing. For a complementary task, use Minimal Detectable Change: Compare observed change with z×√2×SEM minimal detectable change.

References

Limb Symmetry Index — tool.io

Similar or alternative tools

Jump Phase Asymmetry
Calculate bilateral force asymmetry separately for propulsion and landing.
Minimal Detectable Change
Compare observed change with z×√2×SEM minimal detectable change.