I've made some more progress this month. Tricep extension strength is about equal and chest press is about 18% difference. That's a major improvement from January when both triceps & chest were around 50% difference. I still don't know what caused this? The Wikipedia reference-linkrotator cuff pinched nerve is another possibility. I'm still waiting to see a neurologist , now mid May. I'm hoping to be almost recovered by then. My bench is up to 120Kg, big improvement on 60Kg back in December. I'm hoping this will be almost repaired and muscle mass recovered in say 3 months. Keep you posted.