Thom Osborne, Granada, Spain

(Image: The North American Indian by Edward S Curtis / Wikimedia Commons)

Twice at the weekend I went out running. I ran at the same time on both days and for the same distance. I slept well the night before both runs, ate similar meals, drank the same amount of liquid and felt generally fine on both days.

On the first day I bounced along, running as well as I would expect. On the second day it felt like I was running through treacle; I was lethargic and it was dreadfully hard work.

I haven't subsequently gone down with any illness, so why did this happen?

Patrick Parratt, London, UK

(Image: sh0dan, stock.xchng)

I wanted to chill a mug of water so placed it in the freezer, but then forgot about it and it froze solid.

When I removed the block of ice from the mug it contained the most amazing thistle-like pattern of what seemed like canals of air (pictured). None of these canals extended to any outside surfaces. What happened?

Brian Barnes, Somerset West, South Africa

I have just read the label on my shampoo bottle. The list of ingredients is mind-boggling. How on earth did anyone come up with such a complex concoction and what exactly are chemicals such as sodium diethylene-triamine pentamethylene phosphonate and hydroxyisohexyl 3-cyclohexene carboxaldehyde doing to my hair?

Haydn Ford, Hexham, Northumberland, UK

(Image: LotusHead, stock.xchng)

The Last Word has told us why garlic makes your breath and body smell, but I want to know why the spice methi, or fresh fenugreek, has a similar, possibly stronger, effect.

Nikki Bedi, BBC Radio Asian Network, UK

(Image: Wikimedia Commons)

A number of athletics and cycling world records have been set at high-altitude venues, for example during the 1968 Olympic Games in Mexico City.

Presumably the air is thinner so there is less resistance, enabling them to run or cycle faster. But surely oxygen uptake at altitude is more difficult, so there must be a point at which altitude no longer favours athletes.

What is this point and why? And which tracks or velodromes come nearest to it?

Carlos Loeb, Madrid, Spain

(Image: Wikimedia Commons)

When closely matched athletes are competing in events that involve running, swimming, throwing or lifting, why does one of them win one day and another the next? Surely whoever is the fastest or strongest will remain so, for a while at least. Often the original winner will return a few days later and win again, so why did he or she lose the race between the two victories?

Magda Loncic, Kiev, Ukraine

(Image: mordoc, stock.xchng)

What is the purpose of the small hole halfway down the outside shell of a Bic ballpoint pen?

Frank Horseman, Derby, UK

Walking along the breakwater at Berwick-upon-Tweed in north-east England recently, my granddaughter and her mother noticed their hair was standing on end (see photo, above left). It started to rain soon afterwards, but there was no thunder or lightning that day. What was happening?Richard Turner, Harrogate, North Yorkshire, UK

A sprint athlete is deemed to have false-started if they react within 0.1 seconds of the starting gun. This seems like a rather arbitrary round figure. What studies have been done to test human reaction times, and is the fastest a person can react to the sound of a gun really exactly 0.1 seconds?

Cathy Jameson, Barrow, Cumbria, UK

(Image: Rudolphous, Wikimedia Commons)