Reactive Strength Index

Compute reactive strength index from inferred jump height and ground contact time.

Description

Reactive strength index divides ballistic jump height by contact time.

Reactive strength index divides ballistic jump height by contact time. Flight/contact ratio is reported separately and has a different unit basis.^[1]

Compute reactive strength index from inferred jump height and ground contact time.

When to use Reactive Strength Index

Use this tool to compute reactive strength index from inferred jump height and ground contact time.

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

How to use Reactive Strength 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 flightSeconds, contactSeconds, gravityMps2 using the field table and calculation rules, then run the tool.
Read jumpHeightM, reactiveStrengthIndexMps, flightContactRatio. 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
flightSeconds	Flight seconds	number	Required
contactSeconds	Contact seconds	number	Required
gravityMps2	Gravity mps 2	number	Required

Enter positive flight/contact seconds and gravity. Return meters, RSI m/s and dimensionless time ratio.

height=g flight²/8; RSI=height/contact; ratio=flight/contact

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

Output field	Meaning	Value type
jumpHeightM	Jump height m	number
reactiveStrengthIndexMps	Reactive strength index mps	number
flightContactRatio	Flight contact ratio	number

json

{
  "input": {
    "flightSeconds": 0.4,
    "contactSeconds": 0.2,
    "gravityMps2": 10
  },
  "output": {
    "jumpHeightM": 0.20000000000000004,
    "reactiveStrengthIndexMps": 1.0000000000000002,
    "flightContactRatio": 2
  }
}

Limitations and assumptions

Assumes equal takeoff/landing height and ballistic flight. No landing technique or performance threshold is supplied.

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 Flight Time Jump Height: Infer ballistic jump height from flight time and supplied gravitational acceleration. For a complementary task, use Takeoff Impulse Velocity: Convert net takeoff impulse to velocity and ideal ballistic jump height.

References

Reactive Strength Index — tool.io

Similar or alternative tools

Flight Time Jump Height
Infer ballistic jump height from flight time and supplied gravitational acceleration.
Takeoff Impulse Velocity
Convert net takeoff impulse to velocity and ideal ballistic jump height.