Category: Muscle physiology

Approximately 40 different myosin genes exist in humans, coding for a superfamily of motor proteins essential for muscle contraction and cellular transport. The regulation of these proteins is complex, determining precisely what triggers myosin and its action.

Creatine phosphate, also known as phosphocreatine, is a high-energy molecule found predominantly in muscle cells that acts as a rapidly accessible energy reserve. This crucial compound serves to supply energy for the synthesis of adenosine triphosphate (ATP), the body's primary energy currency, particularly during the initial seconds of intense physical exertion.

The human body is constantly creating and consuming energy, with muscle cells being particularly demanding. In fact, each muscle cell can cycle through a billion molecules of adenosine triphosphate (ATP) every two minutes during intense activity. So, what do muscles use as an energy source to power everything from a simple blink to a full-out sprint?

Skeletal muscle is widely recognized for its ability to store carbohydrates, but surprisingly, muscle cells also store fat. These tiny fat droplets, known as intramyocellular lipids (IMCLs), serve as an essential and readily available energy source for working muscles, particularly during prolonged exercise. However, the role of IMCLs is complex, and their accumulation is associated with both enhanced metabolic health in athletes and insulin resistance in sedentary individuals.

Approximately 75% of the body's total carbohydrate stores are found in skeletal muscle, where they exist in the form of glycogen. This highly branched polysaccharide is the primary energy reserve, dictating performance and function for muscles and fueling moderate to high-intensity exercise.

Over 75% of the body's total glycogen is stored in the muscles, but what effect does glucagon have on glycogen in muscle? The answer is none directly, as this hormone primarily targets the liver for systemic glucose release.

The body's fat reserves hold over 60 times the energy of carbohydrate stores, a crucial fact for energy production. Yes, muscles can use fatty acids for fuel, a process vital for sustained activity, especially during prolonged exercise. This energy system provides a high-efficiency fuel source for many bodily functions.

An average person stores about 400 grams of glycogen in their skeletal muscles, but this amount can vary significantly based on body composition and training level. This fact underpins a common question among athletes and fitness enthusiasts: do bigger muscles have more glycogen?