Smoking avoid you to sleep and laziness so if you do more work obviously your work capacity will improve. But,it does not means that you should start smoking to improve work capacity. You should not try this.
Nicotine does help in raising level of blood pressure and one might get a passing feeling of being energetic but it disappears quickly to create the next desire to smoke!!!
Smoking doesn't improve capacity to do work. But the smokers says reason that it improves their capacity to do work.it is not true. They smoke in that name of capacity.
smoking just increase the body capability for the small after its effect over it lay the body down and body's capacity of doing work lowers down than normal level.