Why are four-person bobsleighs faster than two-person bobsleighs? Is it because they have two extra people pushing at the start and therefore are faster throughout their run or is it to do with weight and momentum? Surely there comes a point when the extra weight slows the bob too much? A few friends and I spent an hour or so arguing over this the other week, divided into those who thought it was the extra weight and others who thought it was the extra runners.

Alan Kane, Glasgow, UK

One criticism often levelled at soccer is that the game can be unexciting as not many goals are scored in most matches. What would be the likelihood of goals if the rules were changed to allow two footballs to be in play at the same time?

Tony Holkham, Petersfield, Hampshire, UK

I have heard on numerous occaisions that it is dangerous to press a weight from behind the head, or pull a resisted bar (e.g. lat pulldown, pullups) behind the head. I have heard a few theories, based on either rotator cuff limitations or the risk of damage to the cervical spine. Anybody know of definite evidence/proof or even with solid reasoning and not just naming a few anatomical structures? Thanks

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?