Will be deeply ! a gymnast currently stretches her hamstrings by bending forward at the waist and touching her fingers to the ground for 15 seconds, five days per week. to improve flexibility, she begins to hold the stretch for five seconds longer on each stretch. this type of change is - intensity - frequency - time - type

frequency is the answer

the right answer is: time

since you have not provided the options here i   am going to give you general overview about hormone.hormone are actually the part of endocrine system in our body and produced by the endocrine glands. the hormones act like a chemical messenger   within human body. once produce by the glands they   travel through the blood stream and reach at specific or target tissue and organs   which result in control of our body function. the hormones are specific in their work and work on only the targeted tissue or organ   . with the of hormone endocrine system regulate the heart rate , metabolism, our mood and   growth as well as the development and even the sleeping cycle etc. they actually are the messenger for body cell and organs .