Muscles work synergistically in agonist and antagonist pairs to produce forces that enable humans to carry out tasks ranging from pumping blood through the body to locomotion and exercise. However, as muscles fatigue, their ability to perform their prescribed functions declines over time. One way to characterize muscle fatigue is to measure the decrease in the maximum force a muscle can exert during a contraction, which is exhibited by a decrease in the frequency of nerve signals it receives. Understanding muscle fatigue has important applications in training program development and injury prevention. There are several factors that can influence the rate at which a muscle fatigues, including the type of muscle structure, blood flow, oxygen levels, metabolism, and available energy. Our research seeks to investigate the effect that hormone levels have on muscle’s performance as well as its susceptibility to fatigue.
Hormone synthesis is correlated with several other physiological pathways, such as cholesterol synthesis, energy production, and food metabolism. The connection between these pathways and muscle activation suggests a likely connection between hormone levels and muscle fatigue. This study is an investigation into how the cyclic rise and fall of hormones that drive the menstrual cycle may affect the rate at which a muscle fatigues. There are four main hormones that play a role in the menstrual cycle: estrogen, progesterone, follicle stimulating hormone (FSH), and luteinizing hormone (LH). Using at-home methods, a menstruating individual can determine the stage they are at in their menstrual cycle, which would indicate relative hormone levels for that individual. Combining this data with electromyography (EMG) analysis of muscle fatigue may demonstrate if there is a relationship between muscle fatigue and phases of the menstrual cycle. We will specifically focus on the Flexor Hallucis Longus (FHL), which produces the final push that lifts the foot from the ground during the toe-off phase of the walking and running gait cycle. This information can be used to enhance training programs for athletes by identifying when they should complete strength-based or endurance training, as well as help individuals avoid injury by knowing when to not overexert themselves