Arthritis: it’s a disease that sneaks up on you. Fingers and toes slowly but surely become stiff and painful. A nice morning stretch is no longer all it takes to get your body moving. Arthritis is a chronic illness that sinks its claws into your body, and causes inflammation in your joints. It can destroy your joints, which causes weakness and loss of movement. New research suggests that high intensity training can help with the pain that the illness provides.