Last week, we did an overview of Health in general- we discussed that Health should be perceived in a holistic manner; a healthy body is likely going to  give rise to a healthy mind and vice –versa. There is an adage that says “Prevention is better than cure”; an also “An Apple a day keeps the Doctor away”.  

This week, we are going to discuss an aspect of Preventive Medicine called AEROBIC EXERCISES.                                                                                                       

Exercise has been widely used as preventative medicine to reduce the risk and incidence of cardiovascular and metabolic diseases related to sedentary and unhealthy living. Regular exercise has been shown to improve health and reduce the severity of diseases accompanying an unhealthy lifestyle.

Aerobic Exercise- also known as Endurance activities, Cardio or Cardio-respiratory exercise, is   a Physical exercise of low to high intensity that depends primarily on the Aerobic  energy- generating process. “Aerobic “ is defined as “relating to , involving , or requiring  free oxygen and refers to the use of oxygen to adequately meet energy demands during exercise via aerobic metabolism. That means Aerobic exercises require pumping of oxygenated blood by the heart to deliver oxygen to working muscles. Aerobic exercise stimulates the heart rate and breathing rate to increase in a way that  can be sustained by the exercise session. In contrast, “Anaerobic”-(without oxygen) exercise, causes you to be quickly out of breath like sprinting, or lifting a heavy weight. The bottom line is that the intensity with which you perform an activity determines whether it is Aerobic or Anaerobic.

HISTORICAL BACKGROUND                                   

Archibald Hill, a British Physiologist in 1922, introduced the concept of maximal oxygen intake and oxygen debt and himself and a German Physician, Otto Meyerhof, shared the 1922 Nobel prize in Physiology/Medicine for their independent work related to muscle energy metabolism. This work served as a foundation for Scientists to begin measuring oxygen consumption during exercise. After World War 2, health-oriented recreational activities such as jogging became popular. Physical Therapists, Col. Pauline Potts and Dr. Kenneth Cooper first advocated the concept of Aerobic exercise.

Cooper, now known as the father of Aerobics and who encouraged millions of people to become physically active, first published his ideas in a book called “Aerobics” in 1968 and published another  in 1979 titled “The new Aerobics”. Jacki  Sorensen, inspired by Cooper’s book, created Aerobic Dancing routines which grew in popularity in the 1970’s.

Aerobics at home became popular worldwide after the release of Jane Fonda’s Workout  exercise. Step Aerobics became popular in the 1990’s.

 NATURE OF AEROBIC EXERCISE              

Aerobic exercise start with breathing—in other words,  inhaling and exhaling; The average healthy adult  inhales and exhales about 7-8 litres of air per minute. Once you fill your lungs, the oxygen in the air (air contains approximately 20% oxygen); filters through the small branches of tubes (called bronchioles) until it reaches the Alveoli, which are microscopic sacs from where oxygen diffuses or enters into the blood. From the blood, the oxygen goes directly to the heart.

The heart has two chambers that fill with blood and pump blood( two atria and 2 ventricles) and some very active coronary arteries. Because of all this action, the heart always  needs a fresh supply of oxygen, which the lungs provide. Once the heart uses what it needs, it pumps the blood carrying the oxygen and other nutrients out through the left ventricle, and through the circulatory system(cardiovascular system) to all the organs, muscles and tissues that need it.

The heart beats approximately 60-80 times per minute at rest.  Every beat of the heart sends a volume of blood along with the oxygen and many other life-sustaining nutrients, circulating through the body. The average adult healthy heart pumps about 5 litres of blood per minute.

Oxygen Consumption  is the amount of oxygen the muscles extract or consume from the blood. It is expressed as  ml/kg/minute-(milliliters per kilogram of body weight per minute), Muscles are like engines that run on fuel –just like an automobile that runs on fuel; difference is that the muscles use fats and carbohydrates instead of fuel used by the automobile.   Oxygen is a key player; once inside the muscle, it is used to burn fats and carbohydrates for fuel or energy  to keep our engines running. The more efficient our muscles are at consuming oxygen, the more fuel we can burn , the more fit we are and the longer we can exercise.

WHY DO WE NEED AEROBIC EXERCISES?

The average sedentary adult will reach a level of oxygen consumption level of about 35ml/kg/minute during a maximal treadmill test(where you are asked to walk as hard as you can). Translated, that means the person is consuming 35 millilitres of oxygen for every kilogram of body weight per minute.  Some athletes can reach values as high as 90ml/kg/minute! What happens is that in the latter case, the bodies adapt through training; this good news- that for the rest of us, our bodies can adapt through training too!

EXAMPLES OF AEROBIC  EXERCISES.                                     

Moderate Activities.

• Dancing
• Hiking on flat ground
• Bicycling at less than 10mph
• Moderate walking(about 3.5 mph)
• Golf(not using a cart)
• Downhill skiing
• Tennis(doubles)
• Softball
• Swimming
• Gardening
• Light Yard work
• Jogging

Vigorous Activities

• Brisk walking(about 4.5mph)
• Bicycling at more than 10mph
• Hiking uphill
•  Cross country skiing
• Stairs climbing
• Soccer
• Jumping rope(Skipping rope)
• Tennis (singles)
• Basketball
• Heavy Yard work.

BENEFITS OF AEROBIC EXERCISES AND BODY ADAPTATION THROUGH TRAINING

1. When Aerobic  exercises are done regularly, the heart gets stronger and pumps more with each beat(larger stroke volume); hearts subjected to training have a greater diameter and mass since the heart is a muscle too and get bigger when you train it. Consequently, the heart pumps more efficiently,  allows for greater filling time , more blood fills the chambers and more blood gets pumped with each heart beat.
2. Greater stroke volume means that the heart means that the heart doesn’t have to pump as fast to meet the demands of exercise. Fewer beats  and more stroke volume  means greater efficiency. Normally, a pump emptying water out of a flooded basement works better and lasts longer if it can pump larger volumes of water with each cycle than if it had to pump faster with smaller volumes of water. High stroke volume is why athletes’ hearts  don’t  pump fast during exercise and why they have such low resting heart  rates—sometimes as low as 40 beats per minute, whereas the average is 60-80 beats per minute.
3. Greater stroke volume with regular aerobic exercises means that the muscles become more efficient at consuming oxygen; more oxygen will be transported from the blood to the muscle and will result in better fitness  and  endurance as the muscle will not quickly run out of oxygen when compared to a situation of lower stroke volume.
4. Mitochondria in the muscle increase in number and activity in response to regular aerobic exercises in adults of all ages in just a matter of days to weeks. Mitochondria are the “powerhouses” of the cells, using the oxygen to burn the fat and carbohydrate that gives you the energy  to keep going.
5. Opportunities to burn fats are prevalent; Fats contain 9calories per gram whereas carbohydrates contain 4 calories per gram. More oxygen is needed to burn fats because it is denser than carbohydrates. The good news is that when regular aerobic exercises are done, the heart pumps more blood , the muscles consume more oxygen and the mitochondria increase in number and activity to burn the fat.

Caroline Ademiluyi is a Lagos based pharmacist