Re: OT : Petrol Pumps
If you have trouble gripping, I recommend using a gyroscope 'Power Ball' to strengthen the appropriate muscles.
Not so good if the muscle attachments are affected by psoriatic arthritis. The body actively works to stop you applying force to muscles attached to the joints affected.
 Imagine psoriasis. Now imagine it affecting the synovial membranes round the joint capsules and causing inflammation to said membranes and the tendons nearby. It's quite painful. And, if left untreated, caused acute joint deformation. In my case, it affects the hands, feet, lower spine, knees and hips. Which is why I had to give up riding motorbikes.
 Which involves quite a number of toxic compounds and/or biologicals. Which is why blood tests once/month get done.