Quantitation of tendon reflexes in normal volunteers.

Ankle (ATR), patellar (PTR) and triceps (TTR) T-reflex responses were recorded in 48 limbs of 24 normal volunteers by delivering tendon taps with a hand operated electronic hammer. Latency to the onset of the triggered response, peak to peak amplitude and duration of the wave were measured after several repetitions. In all individuals, ATR and PTR were observed, while in 27% of limbs, TTR was absent. Shortest latency and duration of the elicited response were chosen to calculate normal means. Side differences were also evaluated. As amplitude showed a marked interindividual and side to side variation, lowest recorded value was selected to represent the lower limit of normal. Age, height, and leg length showed a good correlation with minimum ATR latency (p < 0.001). PTR latency correlated significantly with age, height, (p < 0.001) and thigh length (p < 0.001). No significant correlation existed between age, height, arm length and TTR latency (p > 0.01). In conclusion, ATR and PTR are acceptable tests in clinical practice, whereas TTR is not reliable, as it is technically difficult to elicit in some normal individuals.