Bigtallfatbloke said:
making my own look easier than the title Isontonic would seem to imply....I carry a packet of Vit C tabs which disolve to an orange drink in water....all i need do then is add a little salt, maybe some sugar and I'm isotonicd up right?
Sort of, but not really. Electrolytes are the 'salts' that are contained in both isotonic and hypotonic (no carbs/KCals but only 'salts') drinks. These do not usually contain any sodium chloride or 'table salt' as such. They instead contain different salts, including sodium, potasium, iodide, bicarbonate and others.
Refined sugar on it's own is not a great subsititute for drinks that contain longer chain and multiple types of sugars. It's best to read the labels carefully to see what is actually in them, as some are much better than others. You need a mixture of slow and quick release sugars to sustain a longer bike ride. Refined sugar in large doses is not that great in cycling terms, because it is absorbed all at once into the blood, raising your blood sugar level for a short time before a rapid decrease in that level which leaves you feeling, at best, tired and weak, and at worst, with a bad case of the 'bonk'. The way that you would usually drink on the bike though, does offset this unwanted effect to some extent, because you would not usually down a bottle of high sugar drink in one go, but would sip it gradually over a longer period of time, thus ensuring a steadier supply of sugar into the blood. This isn't that great for your teeth of course as they are continually exposed to the sugar over a much longer time period. Fructose in fruit juice is an alternatve to refined sugars, but again it isn't good for your teeth over long periods and is just as quickly released into the blood as refined sugars. You may still need to eat something as well as usuing these drinks if out for longer periods.
You may want to avoid sugary carbohydrate drinks altogether (either isotonic or hypertonic ones) and go for a hypotonic drink instead. This is one that contains no KCalories or carbohydrates, but only the electrolytes you lose in sweat and dilute if you only drink plain water. 'Nuun' is one brand and there are several others too. If you go for this option, this will mean that you will definitely need to eat something for energy whilst riding. If this is the case try to eat a mixture of steady release and fast release sugars - have a look at a Glycamic Indexed table of foods to get a good balance.