One-minute exercise is best for evaluation of postexercise exhaustion in myasthenia gravis.

INTRODUCTION

To find the best exercise duration for postexercise exhaustion by decrement (PEE-D) in myasthenia gravis (MG).

METHODS

In 32 tests in 32 MG patients, repetitive nerve stimulation was performed in the abductor digiti quinti muscle. The 3 Hz responses for 2 s were obtained with supramaximal stimulation at rest, and immediately after (PE0), 30 s after (PE30s), and 1, 2, 3, and 4 min after 10-s, 30-s, and 1-min exercises.

RESULTS

Compared with the decrement at rest, a significantly greater decrement was found at PE2m and PE3m after 30-s exercise, and at PE2m, PE3m, and PE4m after 1-min exercise. In 11 patients who showed a decremental response only with exercise, PEE-D was observed in 5 after 30-s exercise and in 8 after 1-min exercise.

CONCLUSIONS

One-minute exercise is best for evaluation of PEE-D in MG.