1.Sunlight
the body’s energy source
2.Aerobic
versus anaerobic
3.Effects
of a stamina- building programme
4.
Carbohydrates and fats
5.Fibre
types and colours
6.Stamina
training programme
1.Sunlight
the body’s energy source
When we bend an elbow, take a step or blink an eye, we use muscle power. But what exactly is muscle power and how does the muscle get its power?
It seems remarkable- but muscle power comes from sunlight. It is the same kind of power that charges the batteries of a space probe, or starts a fire when the sun’s rays are focused through a magnifying glass. Solar energy is the radiant energy from the sun (which in turn is produced by the conversion of hydrogen atoms into helium atoms). This solar energy gets into the body through the foods we eat. A process known as ‘photosynthesis’ locks the energy from sunlight into the starches and sugars of plants. The sunlight is trapped by the green chlorophyll and used in the manufacture of carbohydrates from carbon dioxide and water.
The carbohydrates can be stored in muscles and the liver (in the form of a substance called ‘glycogen’) to provide fuel for muscle power. As muscles use this locked energy, the carbohydrate molecule breaks down into its original components (carbon dioxide and water), which are then removed from the body as waste products. The body can also get energy from its fat stores and, to a lesser extent, from protein.
The fact that energy released during physical activity is apparent as we feel our bodies heating up, causing us to sweat. In fact, around 75% of all the energy released is in the form of heat, whilst approximately 25% is harnessed for muscle power.
Food provides energy for action, just as fuel provides energy for a car engine. But the engine has only one way of converting fuel, whilst the body can shift from one energy system to other.
Anaerobic metabolism- instant energy
Muscles can work for limited periods of time without oxygen. This is termed ‘anaerobic’ work. During the first few minutes of intense effort of the lifting and carrying of heavy objects, the body uses an energy store located within the muscle fibres.
Firstly muscles tap a substance called ATP (adenosine trisophate). This is the only fuel that can power the muscles. However, the store of ATP is tiny and it burns out in about one second. So, the body then uses another substance, CP (creatine phosphate), which is also stored in muscles, to rebuild a fresh supply of ATP. This system supplies about enough energy for around ten seconds of intensive exertion. After that, muscles can use a third energy supply, glycogen (a form of carbohydrate stored in your muscles- with extra supplies stored in the liver), to rebuild the ATP. Unfortunately, this energy system also generates a substance called ‘lactic acid’, which builds up in muscles causing pain and fatigue. When exercise ceases, this lactic acid is flushed out of muscles into the blood stream, enabling muscles to recover. Lactic acid, therefore, is the substance that causes legs to ache.
Anaerobic energy is vital to us and it provides us with the instant energy required for the first few seconds of intensive physical activity and for the first few minutes of muscle endurance work.
Aerobic metabolism- the key to stamina and endurance performance
For activity to last more than a few minutes, energy has to come from a much longer- lasting source. This is termed ‘aerobic energy’ and relies on oxygen being supplied to muscles by the lungs, heart and blood circulation. This is why aerobic fitness (‘aero’ means ‘with oxygen’) is often called cardiorespiratory (heart- lung) fitness.
The oxygen breathed in is transported to the working muscles, where it combines with molecules of fat or carbohydrate, to provide the energy for the aerobic exercise- such a walking, cycling and swimming.
Aerobic metabolism is around 16 times more efficient at generating energy than anaerobic metabolism. That is why, after a few minutes of exercise, we often settle into a ‘second wind’. The body has gradually changed from supplying energy predominantly from the anaerobic system during the first few minutes to the more efficient aerobic energy system as exercise is continued.
3.Effects
of a stamina- building programme
There are some remarkable adaptations by the heart and lungs that result from an effective stamina- building programme:
This is why endurance or aerobic fitness is often termed ‘heart- lung’ or cardiorespiratory fitness.
4.
Carbohydrates and fats
At rest the body uses a mixture of carbohydrates (glycogen) and fats to fuel its energy needs. During anaerobic exercise, such as strength and power work or sprinting, the body uses its glycogen stores to generate the bulk of its energy needs. Also, when exercising aerobically, at a fairly vigorous intensity of around 75-85% of maximum heart rate (e.g. running or swimming), carbohydrate (glycogen) is the preferred fuel.
However, exercising aerobically at a moderate pace- such as a brisk walk- uses fat as the fuel. This is why L-S-D (‘long-slow-distance’) activities, such as walking and cycling are excellent ‘fat burning activities’. However, it takes about 15 minutes for the fat metabolism to swing into action, so a half-hour brisk walk is ideal to get the fat burning system (lipolysis) moving.
5.Fibre
types and colours
Fast- twitch or slow- twitch?
All muscle fibres are connected by nerves to the brain and they respond to nerve impulses. A nerve impulse is rather like a tiny electrical current travelling at speeds of up to 100 metres a second.
Some muscles appear quite white in colour and are connected to the central nervous system by high- speed nerves. They are called ‘fast- twitch fibres’ and provide speed and high- power movements. A top class sprinter would have a very high proportion of fast- twitch fibres.
Other fibres appear quite red and are connected by less- fast nerves to the brain. These fibres are termed ‘slow- twitch fibres’ and are better suited to more prolonged, endurance work. A top- level marathon runner may have muscles containing 80-90% of these red, fatigue- resistant, slow- twitch fibres.
Most of us have a good mix of red and white- and various shades of ‘pink’ in between. Some of us have a higher proportion of white fibres and are better at strength and power activities, whilst others are ‘red fibre’ people and are better suited to stamina- type endurance work. Different types of fitness programmes will train these different fibre types. We can train for strength and power or for endurance. Each aspect of fitness will be improved best by training that is specific to it. So, strength training is quite different from stamina training.
6.Stamina
training programme
Training programme should have.
1.Pre- test to determine existing stamina levels.
Stamina- building activities include:
The following circuit is designed to strengthen the muscles of the legs, stomach, arms and back, and to produce a good level of aerobic fitness.
Step ups x 20
Abdominal curls x10
Press- ups x 10
Dorsal curls x 10
Squat thrusts x 20
Bicep curls x 10
Shuttle runs x 10
Presses x 10
Squat jumps x 15
Deltoid raises x 10
Safety principles