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Contraction-induced upper extremity H reflexes: normative values
1Department of Physical Medicine and Rehabilitation, Cooper Hospital/University Medical Center, and the University of Medicine and Dentistry of New Jersey, Robert Wood Johnson Medical School at Camden, 08103, USA.
Objectives:
To determine the reliability of contraction-induced upper extremity H reflexes; to calculate normal values for latency, amplitude, and side-to-side variation; and to correlate latency to arm length.
Design:
Case series.
Setting:
Electrophysiology laboratory of a tertiary care center.
Participants:
Twenty-three healthy volunteers (4 men, 19 women), aged 19 to 42.
Intervention:
Volunteers were tested bilaterally for H reflexes in four to six upper extremity muscles during an isometric contraction.
Main Outcome Measures:
H reflex onset latency, onset to negative peak amplitude, side-to-side variation, normal ranges, and latency versus arm-length correlation.
Results:
H reflexes were found at all 264 sites tested. Mean latencies varied from 9.5 to 27 msec. Maximum normal side-to-side variation was 1.5 to 2.7 msec. Maximum normal amplitude ratios (larger to smaller) ranged from 2.06 to 4.80. Abductor pollicis brevis (APB) and abductor digiti minimi (ADM) H reflex latencies were strongly correlated to arm length. Correlation for APB = .64 (p<.0001) and for ADM = .70 (p<.0001).
Conclusions:
Contraction-induced upper extremity H reflexes occur consistently in healthy adults, with latencies, amplitudes, and side-to-side variation occurring in predictable ranges.