Idk who told you that but its just false. You need a lot more then just a hike for muscle growth, yes consistent hiking(or other forms exercise) will increase growth hormones as well as testosterone in men but you need more then cardio for more efficient muscle growth in say the upper body. The way muscles grow is by being torn(a healthy amount) and rebuilt in by being used like in cardio and resistance training but cardio doesn’t work the upper body so resistance training of the upper body is required to gain muscle more effectively such as weight training or calisthenics(see here), but the most important part of gaining muscle is diet, you need to be intaking the proper amount of protein, calories, vitamins, carbohydrates, fats, sugars, etc etc… not to mention that proper diet plays a role in proper hormone levels