Exercise is good, however excessive weight in repetitive movement is not good. Lightness is the key to being able to continue in our profession for a prolonged period of time (15yrs+). Repetitive action with minimum strain to joints will actually help to maintain muscle tone as much as heavier exercise would. The key is not to develop our muscles, but to keep them well toned and working with our joints and ligaments as smoothly as possible. The heavier the weight we work with, the more sudden snatching movements will happen, leading to premature wear and possible injury.
I personally am striving to reduce weight whenever and wherever possible. I have just started trialling a new even lighter design brush. This could knock about 100g off of the weight of a Super-Lite brush. I could not believe the difference when I stuck it on the end of a 35ft carbon pole and went and worked with it for the day. It made the pole feel about half of its previous weight despite only shaving 100g off. To me this has got to be a good thing. I believe that lightness will continue to be of primary importance in our profession. I for one am working hard to keep reducing the weight of the average window cleaner's equipment.
A friend and client has just bought an SL-X as his shoulders and neck are suffering using heavier equipment. He is an absolute 'bull' of a man, incredibly strong and tough. He always thought that he could get away with any weight pole/brush, but his joints and ligaments are still made of the same stuff as the rest of us and he is now suffering because of the job.
riahehttrepuR, you are a strong fit bloke, but I notice that you are currently using the two lightest WFP ranges available on the market. I wonder how you'd be faring if you were still regularly using older, heavier equipment 
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although i am glad alex makes the lightweight equipment as it definately makes our work easier i have to disagree with some of what he says, the bloke he knows who is suffering is probably using an unatural angle when lifting and this is what is causing the damage not the weights, you state excessive weight with repetitive movement is not good but this just isnt true providing we build up strengh first i have posted on here before this web site www.fitness4x4.com look on the about us page and watch the video it will prove my point this bloke is now sixty years old and is still improving year on year if anyone wants to build ligament and muscle strength and avoid injury in the job we do i would recomend going to his online store and buying his hour of power dvd in my opinion it is perfect training for our job, like i said i am glad alex makes the lightweight equipment as it makes things very easy but i am also confident that i could use a 10kg pole allday and not get any neck or shoulder pain.
I had to give up work 7 years ago because of a serious illness. I had to be looked after 24/7. Couldn't move, dress, feed, wash or go toilet by myself, had to have everything done for me like a very young or old person. Life doesn't get any lower than losing your independence and dignity.
Through sheer stubborness and determination to regain some degree of my independance, I perservered constantly, in pain and agony, for a very long time, until I was able to take care of myself again, through sensible, appropiate, regular, exercise.
I only wish to be as fit as I need too for work, to allow me to earn a decent living and maintain a happy balanced social/work life. I'm not interested in short term benefits of using heavy, cumbersome wfpoles to build muscles to impress women. I want to look after my health long term and have suppleness and freedom in my joints and ligaments, hence why I choose lightweight poles anyday. "Why make life any harder than it already is".
People in the far East, on average live to a ripe old age because they do regular, gentle exercises everyday and take care of their bodies much better than us UK residents feeding ourselves on junk food which is full of toxins. Eating healthy foods and not smoking, taking drugs or drinking excessively is far better for our bodies than trying to go down the gym once a week to lift weights and undo all the good work afterwards.