Hi,
From the explanation that you have given, I suppose you had an
injury 2 years ago which is healed but some residual symptoms are left like weakness of muscles. If you had a
bruise then a scar tissue is not allowing you to perform your activities.
So what I suppose is a de-conditioning has taken place on your left side which includes your breathing muscles, your shoulder and arm muscles and your upper back muscles. You need to recondition them using exercises which would target each and every specific weight lifting muscle like trapezius,
biceps, triceps, pectoralis, rectus, abdominis, latissimus dorsi and erector spinae group.
This could be achieved with the proper
Physiotherapy treatment especially the sports physiotherapy speciality which will help you in regaining your muscle strength and assist you in going ahead with your weight lifting activities.
Hope you found the solution to your problem. Let me know if I can assist you further.
Get well soon.
Regards,
Dr. Jenis Bhalavat