No matter the exercise or the person doing it, no one is immune from the almost immobilizing affects of what some have termed “The Wall”. Anyone that is active has hit a level of exercise fatigue that can be caused by a number of factors. Let’s learn a little about them and how to reduce the effects.
You can experience two types of exercise fatigue: peripheral or central. The human body runs on energy derived from foods that we consume. The food is converted to glucose, which is further broken down into a useable energy source for muscle cells. Strenuous physical activity or exercise increases the demand for energy and affects the biochemical balance within the muscle cells. Hard working muscles produce a greater amount of byproducts from the breakdown of the energy and the muscles themselves.
Byproducts, such as lactic acid, can accumulate in muscles and directly affect the mechanical functioning of cells. Working muscles also produce heat as a result of the constant contractions. If you have ever broken a sweat during a workout then you have experienced the heat being released as a byproduct of your workout. The increased demand for energy to power muscles for your workouts, the byproducts produced from the breakdown of energy and the heat produced by hard working muscles all lead up to the first type of fatigue — peripheral.
The second type of fatigue is central fatigue or fatigue that occurs due to factors affecting the central nervous system (CNS). Your CNS is made up of the brain, spinal cord and nerves that exit the cord. Nerves exit the spinal cord and innervate muscles around the body. The combination of nerve and the muscle it innervates is called a motor unit (MU). When you need the extra “oomph” to lift 225lbs or squat 400lbs, the brain sends a signal to the motor unit to contract at a great rate than if you were to lift, say a cup of coffee. The more weight being lifted, the greater the signal the brain sends to the MU. Central fatigue occurs due to poor MU firing. During a prolonged or intense workout session the rapid drop in energy stores, production of byproducts and increase in temperature due to heat production, all decrease the neural drive leaving you feeling almost absolute weakness.