Exercise and Your Muscles

Your muscular system basically consists of three types of muscles. They are skeletal, smooth, and cardiac muscles. These muscles contract and produce force according to the signals from your nervous system. Therefore, they create movements of your body.

Skeletal muscles, which are attached to the bones, contract with the help of the nervous system and create specific movements of the body. They are under your control and are ready to move as you wish. Skeletal muscular activity generates energy as well as heat. Therefore, it helps keep up your body temperature within the normal range. This process is known as the thermogenesis.

However, cardiac (heart) and smooth muscles are controlled by a part of your nervous system called autonomic nervous system. Therefore, their activities are beyond your control. Smooth muscles are seen in the walls of the tubes and hollow organs in your body, such as the blood vessels, respiratory tract, digestive tract, urinary tract, and various types of glands. They move to create many functions in the body. Cardiac muscles are found in the walls of your heart. They generate rhythmical movements to pump blood to the organ systems of your body.

Basically, the contraction process of all types of muscles is similar. However, the force and contraction of the cardiac and smooth muscles can be affected by a number of hormones secreted from your endocrine system, although skeletal muscles cannot.

Every muscle consists of individual muscle fibres (muscle cells), which can contract and produce force. Therefore, these contractions and force help different kinds of muscles to carry out specific movements in very distinctive ways.

Skeletal muscle fibres can be divided into three groups according to the metabolic or specific contractile features. They are:

• Type i (slow oxidative fibres)
• Type iiA (fast oxidative fibres)
• Type iiB (fast glycolytic fibres)

	Type i	Type iiA	Type iiB
Speed of contraction	Slow	Fast	Fast
Resistance to fatigue	High	Intermediate	Low
Activity used for	Aerobic	Long-term anaerobic	Short-term anaerobic
Maximum duration of use	Several hours	Less than 30 minutes	Less than one minute
Power generated	Low	Medium	High
Oxidative capacity (ability to use oxygen for cellular respiration)	High	High	Low
Glycolytic capacity (ability to do cellular respiration without oxygen)	Low	Intermediate	High
Colour of fibres	Red	Red	White

Every skeletal muscle consists of a mixture of three kinds of muscle fibres. However, their proportions differ according to the action of the particular muscle.

When a sedentary person starts a workout program, he or she may get delayed onset muscle soreness (DOMS) in active muscle groups. DOMS usually appears one to two days following vigorous exercise and may remain for up to three to four days. It is considered to originate from tissue damage due to excessive force applied on the muscle fibres and connective tissues. DOMS usually arises following exercise, which is of high-intensity and is not familiar. It is believed that DOMS occurs because of cellular injury, which breaks down cellular proteins within the muscle. This leads to an inflammation and mild swelling of the particular muscle, causing pain. Usually, eccentric muscle activities cause more damage to the muscle and significant pain.

How do you prevent delayed onset muscle soreness (DOMS)? There are few options to avoid or reduce the level of DOMS.

• Begin your exercise plan with mild to moderate intensity physical activities and increase the intensity gradually.

• Do your workout for a short period initially, and then increase the duration gradually.

• Avoid vigorous eccentric muscle activities as much as possible.

• Treatment with nonsteroidal anti-inflammatory drugs (NSAIDs).

• Using hyperbaric oxygen therapy.

High-intensity resistance training increases the size and strength of the muscles. Therefore, it improves athletic and sport performance significantly. This rise in muscle size may occur due to either increased size of the individual muscle cells or fibres (muscle fibre hypertrophy) or increased number of muscle cells or fibres (muscle fibre hyperplasia). However, there is no clear evidence that resistance training causes muscle fibre hyperplasia, although muscle fibre hypertrophy takes place due to resistance training. Resistance training triggers your endocrine system to secrete growth-promoting substances, which help promote muscle hypertrophy. People, who participate in high volume and high-intensity resistance training for a long period, have more muscle cells (fibres) per motor unit compared to a normal person. Furthermore, anabolic steroids and other growth promoting substances (human and synthetic) may lead to muscle fibre hyperplasia. However, the process of muscle fibre hyperplasia increases the number of muscle fibres in a small amount. It depends on genetic factors, nutrition, training history, and growth promoting substances.

What happens when you exercise?

When you exercise, your cardiac (heart) muscle increases its rate and force of contraction gradually to pump more blood through the circulatory system. The required signal comes from your autonomic nervous system without your knowledge. Then, your heart pumps more blood to the lungs and helps take oxygen into the blood efficiently. It also propels more blood to the working tissues throughout your body to supply oxygen and nutrients. Blood circulation also helps remove waste products from your tissues.

Your skeletal muscles contract and relax as required in a coordinated manner to generate specific movements. This raises the heat production (thermogenesis) and the energy expenditure. The process of thermogenesis also helps increase the metabolism of your body and improve blood circulation.

Smooth muscles contract and dilate to regulate the diameter of the blood vessels and airways. They increase the blood flow to your working tissues and air flow to the lungs for an optimal gas exchange. This process is regulated by the autonomic nervous system and other chemical substances in your body without your knowledge.



Related Links:

Exercise and Your Skeletal System
Exercise and Your Cardiovascular System
Exercise and Your Respiratory System
Exercise and Your Urinary System
Exercise and Your Digestive System
Exercise and Your Nervous System