I have had normal emg on left arm: also normal clinical exam by neuro with full power. now twitching appears from time to time in both calves. very healthy otherwise and athletic . 40 y/o fm. what are my % chances this could still be als ?

If a neurological investigation ruled out ALS, your symptoms may be due to minor electrolyte imbalance. Try increasing your intake of fruit juices to add potassium. Unless you have high blood pressure, it may help to add table salt to the juice. Regular aerobic exercise should improve your muscle health. Wish you good health!

You do not describe any symptoms which would be consistent or concerning regarding a motor neuron disorder. At this point if all is as you mention, your chance of ALS is about zero.