Interactive Physiotherapy ToolsInteractive Tool

EMG / NCV — Interactive Electrodiagnostic Laboratory

Electrodiagnostic Neurophysiology • Nerve Conduction Studies • Needle EMG • Clinical Localization

Sixteen modules covering membrane biophysics, motor and sensory conduction, F-waves and the H-reflex, needle electromyography, repetitive nerve stimulation, normative data and technical artifacts, followed by a localization and clinical-reasoning phase. Includes a waveform laboratory that teaches every trace as what you see, what it means, what it does not prove and the technical pitfalls; an interactive electrode and needle-muscle atlas; a technical-validity engine; a localization comparator; a case laboratory with progressive disclosure; and self-assessment built on clinical reasoning rather than recall.

Theory & referenceFoundations, motor and sensory conduction, late responses, needle EMG, RNS and the neuromuscular junction, normative data, technical artifacts, the disease modules and the localization phase — with the electrode and needle-muscle atlases, the technical-validity engine, the case laboratory and self-assessment.Interactive simulations — 13 laboratoriesMotor and sensory NCS, F-wave, H-reflex, RNS/NMJ, needle EMG, spontaneous activity, MUAP morphology, recruitment, temperature, technical factors, electrode geometry and the normative data explorer. Every trace is generated, and every measurement is read back off the waveform.

Interactive simulations

13 laboratories

Thirteen working laboratories. Every trace below is generated by the same eight-stage causal pipeline — parameter, physiology, signal, recording electrode, filter, stochastic variability, waveform, measurement — so a latency or an amplitude is measured from the waveform you are looking at rather than read from a table. Each laboratory states what it does not model.

Motor Nerve Conduction Study (MNCV) Laboratory

Laboratory 1 of 13

Stimulate at two sites, read the CMAP, and watch distal latency, amplitude and conduction velocity follow from the waveform rather than from a lookup.

Motor Nerve Conduction Study

UNCALIBRATEDMedian (motor)

Recording from abductor pollicis brevis (APB). Selecting a nerve changes the montage, the starting geometry and which reference cohorts are shown — never a conduction property.

Distal stimulation60 mm to recording electrode

Proximal stimulation260 mm to recording electrode

Dashed grey shows the previous sweep, so a change reads as a difference rather than a replacement. Move any control below and watch both traces without scrolling.

Shape of the simulated distal response

Phases: 2
Leading phase: negative (upward)
Dominant phase: negative (upward)
Negative : positive: 2.20
Signal to noise: 9407 : 1

Descriptive only — read off the simulated trace above, and not compared with any normal range, threshold or diagnostic criterion. Polarity follows this library's display convention: negative displays upward.

Stimulus intensity30 mARecruits more axons, so the response grows — then plateaus once stimulation is supramaximal.Distal stimulus to recording distance60 mmA measured surface distance. Further to travel means a later onset and more dispersion.Inter-stimulus distance200 mmproximal trace onlyMoves the proximal stimulator only. The distal RESPONSE is unchanged — same onset, peak and amplitude — which is exactly why two sites are needed to cancel the distal delay. Both traces do share one sweep window, as a dual-trace recording does, so the distal time base rescales.Fastest axon conduction velocity120 m/sSets when the earliest axons arrive, and therefore the onset latency.Slowest axon conduction velocity70 m/sWiden the gap to the fastest value and the response disperses: broader, lower, later tail.G1 offset from the motor point0 mmMoves the active electrode across the muscle, changing which sources dominate the recording.G2 (reference) offset30 mmDifferential recording subtracts G2 from G1. Near the muscle it removes real signal; far over tendon it contributes almost nothing — so the effect is large close in and small further out.Stimulus pulse duration0.1 msdoes not change the traceRecorded as acquisition context (P4-C1 states 0.1 ms, extended for deep nerves).

why the trace does not change

The trace will NOT change. Pulse duration acts through the strength-duration relationship of the axon membrane, and the approved package supplies no chronaxie or rheobase value for it. Rather than invent one, the parameter is carried as protocol context only. This is a declared gap, not a broken control.

Both invert or shift the recording — watch the traces above as you toggle them.

Distal measurements

Onset latency: 0.68 ms
Peak latency: 2.24 ms
Amplitude (peak to peak): 27.37 uV
Amplitude (baseline to peak): -18.81 uV
Duration: 3.20 ms
Area (total): 0.20 uV.ms
Area (negative phase): -11.06 uV.ms

Proximal measurements

Onset latency: 2.48 ms
Peak latency: 4.40 ms
Amplitude (peak to peak): 21.45 uV
Amplitude (baseline to peak): -14.07 uV
Duration: 3.72 ms
Area (total): 0.20 uV.ms
Area (negative phase): -10.05 uV.ms

Segmental measurements — computed from the two traces above

Segmental motor conduction velocityuncalibrated: 111.11 m/s; 200 mm / (2.48 - 0.68) ms
Residual latencyuncalibrated: 0.14 ms; 0.68 ms - (60 mm / 111.11 m/s). Residual latency measures exactly the terminal branch, junctional and sarcolemmal delay that this engine does not model, so it computes toward zero. That is the missing model showing through, not a physiological result.
Proximal / distal amplitude ratio (observed)uncalibrated: 0.78 ratio; proximal peak-to-peak / distal peak-to-peak — an observation, not a criterion
Proximal / distal negative-area ratio (observed)uncalibrated: 0.91 ratio; proximal negative area / distal negative area — an observation, not a criterion

Calibration, provenance and interpretation

Calibration notice. EVERY quantity in this laboratory is UNCALIBRATED and none is clinical output. Layer-1 conduction runs on a BIOPHYSICAL axonal fibre-class band, which is not a nerve-specific clinical conduction velocity and is not used as one: the simulated segmental velocity is an engine result, is never compared against the clinical cohorts, and must not be read as a normal or abnormal MNCV. Latencies, duration, morphology and amplitudes demonstrate the measurement METHOD and the causal chain only. What IS meaningful is relative behaviour — how the response changes when a parameter changes. The simulated fibre population spans the printed conduction-velocity band of its fibre class: the fastest element takes the band maximum, the slowest takes the band minimum. Nothing between or beyond the printed endpoints is invented. The learner may narrow the band to study temporal dispersion; widening beyond the printed band is not offered.