Jessica Johnson, 25, of Charleston, South Carolina, claims her arm muscles ‘exploded’ due to rhabdomyolysis from doing 50 pull-ups in a day as part of the intense Murph Challenge. Jessica Johnson, 25, of Charleston, South Carolina, claims her arm muscles ‘exploded’ due to rhabdomyolysis from doing 50 pull-ups in a day as part of the intense Murph Challenge.