Basic Course in Exercise Physiology - Part 1

Basic Course in Exercise Physiology - Part 1

At Umara, we manufacture nutritional products. But that's just one aspect of what we do. Our primary goal is performance – specifically, your performance. We assist you in running faster, cycling further, and enhancing the pleasure of your athletic endeavors. The concept of performance involves not just nutrition, but also physiology and sports science. Below is part 1, focused on sports science.

Through this 4-part article series, you'll gain a basic understanding of how the body functions during physical activity and how to improve this capability.

Firstly, the human body is incredibly complex, made up of nerves, tissues, muscles, bones, and organs. Several intricate physiological systems are interwoven and influence each other. From a training standpoint, it's easier to categorize these into four groups - Energy Systems, Muscle Physiology, Cardiovascular System, and Nervous System.

The 3 Energy Systems
When physically active, we need energy. The body must convert chemical energy into mechanical energy. In a previous article titled "Carbohydrates, Proteins, and Fats for Athletes - A Basic Course," you can delve deeper into how the body utilizes different energy sources. In simple terms, it mainly uses carbohydrates and fats for energy production. This energy conversion happens in muscle cells, producing Adenosine Triphosphate (ATP), the fuel for muscles and other tissues.

This energy conversion can occur with or without oxygen, i.e., aerobically or anaerobically. Fat is only converted aerobically, while carbohydrates can convert in both manners. We have three distinct energy systems:

Anaerobic Alactic Combustion or ATP-PCr System:
This system lasts for about 10 seconds of work, used when we start, sprint, or make rapid explosive movements. It operates without oxygen but doesn't produce the detrimental (performance-wise) substances that the anaerobic lactic system does, which is the next system.

Anaerobic lactic system:
This second system dominates activities ranging from 10 seconds to 3 minutes when the oxygen supply is insufficient, leading to lactic acid (lactate) formation through anaerobic glycolysis. As mentioned, the body can only maintain this intensity for a few minutes before needing to reduce or stop, allowing the third energy system that operates with oxygen to catch up and offset the oxygen debt and "lactic acid" buildup.

Aerobic energy system:
This third system is the aerobic energy system, which works with both carbohydrates and fats. Carbohydrates are more efficient but are limited in storage in the liver and muscles, while fat is abundant.
All three systems work simultaneously, with the intensity of the activity determining which system is most taxed.

Of all the energy we generate through these processes, 70-85% becomes heat rather than muscle movement. This is known as work efficiency or efficiency ratio, and even a few percentage points difference between athletes can significantly impact performance. Simply put, more experienced athletes usually have better work efficiency.

Muscle Physiology
The above-mentioned energy systems produce ATP, the fuel for our muscles. ATP is necessary for muscle contractions. Our muscles can function in three ways: concentric (contracting), eccentric (resisting and slowly releasing), and isometric (activated without movement).

Muscles in our body are also of different types. There's smooth muscle (found around lungs, internal tissues, and blood vessels), which is controlled by the autonomic nervous system (you don't consciously control your breathing or digestion). Then, there's cardiac muscle, comprised of striped muscle fibers that make up the heart, partially controlled by our actions. Lastly, skeletal muscles, which we consciously control and can be influenced by training and nutrition, comprise about 640 muscles in our body.

Skeletal muscles consist of muscle fibers that form entire muscles. There are two primary types:

Type 1: Slow-twitch fibers, smaller than type 2 fibers. They have more capillaries (tiny blood vessels delivering oxygen-rich blood to muscles) and more mitochondria, cellular components that convert fats and carbs into ATP. They contain more enzymes for aerobic combustion, while type 2 has more for anaerobic combustion.

Type 2: Fast-twitch fibers, larger than type 1. They store more creatine phosphate for quick, explosive movements and more carbohydrates since they operate both aerobically and anaerobically. There are two subtypes: 2a and 2x, with 2x being the fastest.

Type 1 seems less adaptable, while type 2 can change more easily with training, becoming better at either anaerobic or aerobic tasks. Your genetic makeup primarily determines the proportion of these fiber types, affecting your aptitude for various activities and sports. Still, of course, consistent training can refine muscle fibers for endurance or explosiveness.

The fibers activated first depend mainly on intensity. At a calm intensity, type 1 fibers engage first, with type 2 joining as intensity rises. The exercise's duration also plays a role. In endurance tasks, type 1 fibers engage first, with type 2 gradually taking over as the former tires. Similarly, in sprints, type 1 increasingly takes over as type 2 exhausts, which is why sprinters can keep running, but not as quickly.

This article provided a basic overview of energy systems and muscle physiology. In part 2, you can learn about the cardiovascular system – heart, lungs, blood – and the nervous system and their roles in physical performance.