+1 Endura due to the higher Magnesium content than other electrolyte powders (TorQ is comparable). For high exertion activity, replacing potassium, sodium and magnesium as well as ingesting additional calories and water _during_ that activity helps one avoid hyponatremia, muscle cramps and exhaustion (aka bonking or hitting the wall: where your body moves from burning glycogen stores to burning fat [which for those who know, it slow, lethargic and painful]).
Having said that, I'm an enduro, XC, and adventure mountain bike racer and generally only use electrolytes in longer events (2.5hrs+). For longer road or mtb rides (2hrs+), high calorie and easily digestible food is enough for me (bananas contain potassium and fast calories, muesli bars, peanut butter or jam sandwich, anzacs, choc chip biscuits, etc).
I used S! Caps in a 24 hour (team) enduro once and they seemed to stave off cramping (although, I was drinking gatorade powder mix and eating biscuits too so ymmv).
I've not used electrolytes or mineral replacements for bushwalking before but I can imagine high exertion or very hot temperature hiking would require something along these lines.
NOTE: Muscle cramping is a not well understood phenomenon and what works for one person doesn't necessarily work for another. I know more about the various hypotheses about what is needed and why for treating and preventing cramps having suffered for a long time. Magnesium seems to work for me.
Post activity nutrition is another subject I guess (hitting the glycogen window, etc.) but that's beyond the scope (or interest!) of this thread
