Hi there, Thanks for your query. When carrying heavy loads, the arms nerves get stretched apart from compression over them by the shoulder joint. This leads to transient numbing -and consequently, deranged function- of these nerves, which, in turn, cause muscle cramps, numbness and tingling sensation in the concerned arm. Everything is restored to normal once the nerves recover. Consult your doctor and apprise him of my opinion. I am certain that he will agree with me, order required tests, and- based on the reports- will prescribe suitable/modified treatment as advised. If you find my response helpful and informative, do not forget an “excellent” (5-star rating) to my answer, to ENCOURAGE ALL doctors- engaged in social service- to render sound advice to the FREE queries. Take care Dr. Rakesh Karanwal