Alan Glass, London, UK

Does the fact of thinking, of having an intense cerebral activity, lead to more burning of calories? When one has a prolonged mental activity, especially involving concentration, one usually becomes tired and/or hungry... Does this mean that thinking is good "sport"? Is it coherent to imagine a small, non-sporty but intensively reasoning person needing and consuming as much calories as a stronger sportperson?

is there a reason we have a separate bone to articulate the knee (patella), yet elbow articulation is achieved through an extension of an existing bone (olecranon process)? did we evolve them seperately to suit our activities, and do other primates share a similar skeletal anatomy, or have they different structures to suit their movement patterns? it seems to me that the structure of the 2 joints are similar enough ( 1 strong bone forming a hinge joint with 2 smaller bones which articulate about each other) yet the patella seems more susceptible to injury and dislocation. would we be better off with a solid extension of the tibia or would this have led to other problems? i am currently studying a sports injuries course, and the tutor (who obviously understands more on the subject than me by the way, yet doesn't satisfy my curiosity sufficiently) states that we need a patella because of the fine proprioceptive requirements of the leg, but if anything i would have placed (if i were creating humans from scratch) a strongly attatched bony process for the knee joint for weight bearing, and a finely controlled sesamoid bone joint in the elbow for finer hand dexterity. what am i missing?

When I play rugby, I sometimes have 'blackouts' where I regain conciousness at the end of an act such as scoring a try, and have memory of getting the ball, but have no memory of what happened in between and presumably no consciousness at the time. What is happening here; is it a common experience and is it advantageous (it usually occurs during my best play) or a sign of something wrong?

I have a friend who is so irritated by advertisements breaking into his TV sports viewing that he has vowed to boycott those advertisers' products. Has anyone studied negative responses to advertising like this, or the possible negative effect of sports-shirt sponsorship?

Certain soccer clubs - Real Madrid and Manchester United, for example - are intensely disliked by more people than actually support them. Has sponsoring such a team ever damaged sales or the popularity of the firm whose name appears on its shirts?

Alan King, Liverpool, UK

Surely for the level of accuracy it seems to offer, it would need far more cameras than appear to be present at major tennis tournaments. Yet everybody happily accepts its rulings. How does it work?

Franco Pallatini, New York, US