Explain why some people’s leg muscles tired quickly and developed cramp when they were running

Muscle cramps are often the result of dehydration.

Explanation:

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The 'Dehydration/Electrolyte Theory'

It speculates that a significant disturbance in fluid or electrolyte balance, usually due to a reduction in total body exchangeable sodium stores, causes a contraction of the interstitial fluid compartment around muscles and a misfiring of nerve impulses, leading to cramps. And

The burning sensation we sometimes feel during exercise is caused by a build-up of lactic acid. The burning sensation we sometimes feel during exercise is caused by a build-up of lactic acid.

answer: that would be cheating

explanation:

sheep is a herbivore animal whereas grasshopper belongs to the class chordates but both of them feed on greens.  

if grasshopper and sheep feeding on a pasture land, i do not think both of them will have any impact on each other. however, the number of the species can make difference. since sheep feed on greens, there is a possibility there left no pasture land for the grasshoppers or they may get extinct.