Muscle Contraction During Exercise of Differing Intensities and Recovery

Muscle Contraction

Muscle contraction occurs through a process called the Sliding Filament Theory. This involves the filaments of actin and myosin within the muscle fibres sliding past each other to create a contraction.
The process of muscle contraction requires energy in the form of ATP (adenosine triphosphate).
The intensity of the exercise dictates the rate and source of ATP used in muscle contraction.
At rest and during low-intensity exercise, muscles contract aerobically, using oxygen as the main catalyst for ATP production.
During high-intensity exercise, the aerobic system cannot produce ATP quickly enough to meet the demands, causing the body to switch to anaerobic ATP production known as Anaerobic Glycolysis.

The intensity of exercise determines the ratio of aerobic to anaerobic metabolism.
During low intensity exercise, the Aerobic System supplies most of the muscles’ energy. The body uses oxygen to convert carbohydrates and fats into ATP.
At medium intensity, the body begins to use a higher percentage of carbohydrates.
At high intensity, exercise cannot be sustained for long, and is fuelled primarily by the rapid breakdown of carbohydrates.
The Lactic Acid System takes over, which uses glucose or glycogen in absence of oxygen to produce ATP, forming lactic acid as a byproduct.
Lactic acid then accumulates in the muscles, contributing to fatigue.

After exercise, it is crucial for muscle recovery to take place. This is when the body repairs damage and restores muscle glycogen stores.
One important aspect of recovery is the process of lactate removal. Lactate can be converted back to glucose in the liver through the Cori Cycle, used as an energy source by heart and type I muscle fibres, or expelled from the body via sweat and urine.
Adequate recovery allows for Continuous Training, involving low to moderate intensity exercise for an extended period of time to improve aerobic fitness.
Interval Training, involving periods of high-intensity work followed by periods of lower intensity work or rest to recover, can improve anaerobic fitness.
Consuming a balanced meal containing proteins, carbohydrates, and fats within a two-hour window post-exercise can aid in muscle recovery. The proteins help repair and build muscle, while carbohydrates replenish the muscles’ energy stores. Fats are necessary for hormone production and nutrient absorption.