Exertional rhabdomyolysis , AKA “march rhabdo” occurs in athletic “adventures” or in recruits ( hence the reference to marching”.

Eccentric muscle contraction , which you do on long downhills, overexertion, inadequate conditioning, heat, dehydration and more are factors. In most mild or moderate cases like on Whitney, Bob’s suggestions and time work well. I had it there on one occasion but not the others. But if severe, there are very serious medical complications . For more info, see Rhabdo