Does age also affect kicking strength?

As you get older, your muscle mass tends to decline, you start to have gait (walking) problems, stiffening and reducing your mobility. It is possible for your muscle mass to decrease by up to 50% between 30 years of age and "old age" (around 65). It is, therefore, generally true that the loss of muscle mass as you age causes your strength to lessen.

It is, however, possible to keep your strength even at an old age. By regularly exercising yourself, your muscles will become more stimulated and will tend to grow (certainly more useful than being inactive).

How can a person's height affect their kick?

How does the length of the leg affect the strenght of the kick? Who kicks harder – shorter or taller people?

If we ask a tall football player of 90 kg (with a leg of 9 kg) to kick a ball, and then a short one of 60 kg (with a 6 kg leg) at the same leg velocity. Who would send the ball at a higher velocity?

After a few complex equations, its is possible to determine that the tall player will have made the ball move at 21.05 m/s, while the shorter one will have made it move at 18.46 m/s

So if both players kick the ball with the same leg velocity, the taller player will have sent the ball at a higher speed then the shorter player would.

In real life, taller players have longer legs than shorter ones, which means that their legs are heavier. When a person with a heavier leg kicks a ball, even if he spends the same energy as a shorter player, his leg velocity will be smaller than that of a lighter player. Knowing that, which player will have the strongest kick?

In this case, the velocity of the ball kicked by the shorter player will be higher than the velocity of the ball kicked by the taller one. So, generally, shorter people are able to deliver a greater force to the ball than taller ones (assuming the same energy is used for each kick).

More muscle = more strength?

One thing that affects a kick are the muscles behind it. But it doesn’t help to only have strong muscles if these muscles are not even used in the kick itself. The most significant muscles which determine the type of athlete a person is are the Slow and Fast twitch muscle fibers.

Slow and fast twitch fibers have different characteristics when it comes to exercise. In a kick, as you need a rapid contraction of the muscles in order to strongly hit the football, the musclefibers which are used are the fast twitch ones. This is due to the fact that the fast twitch fibers use anaerobic metabolism to create energy, which enables them to have powerful, short bursts of speed. Although these fibers are more easily ‘fired up’ they build up fatigue at a faster rate than the slow twitch fibers.

Human muscles contain a genetically determined mixture of both slow and fast fiber types. On average, we have about 50 percent slow twitch and 50 percent fast twitch fibers in most of the muscles used for movement. But this can vary from person to person, depending on their genetic makeup. Elite athletes, for instance a sprinter, tend to have more or less 80% of the fast twitch fiber which is the muscle they use on their particular sport and just 20% of the slow twitch fiber.

Firstly, some words on steroids...

Most Anabolic steroids (which are basically artificial versions of the natural hormone testosterone, with a structure very similar to the hormone itself [pictured below]) help in building up fast twitch muscle fibres. These fast twitch fibres, which mostly release energy via anaerobic respiration, are capable of short bursts of energy, ideal for something simple like kicking a football.

Though it is true that these anabolic steroids help increase the build-up of muscles (especially when combined with regular exercises), they have a number of problems associated to them, including:

• Stunted growth in teens
• Liver tumors
• Enlargement of heart muscles (this can make it difficult for the heart to pumb blood)
• Violent behaviour and mood swings
• Acne
• Impotence
• Muscle aches

One good example of the dangers which steroids pose is that of the famous Brazilian soccer player Ronaldo, who has constantly been suffering knee injuries. One doctor has suggested that the fact that he took anabolic steroids at an early age (17) could mean that his bone structure was completely unable to cope with his muscle structure, leading to a number of injuries.

What are we doing here?

The purpose of this investigation is to determine what factors, such as age, length of leg and even external factors (like steroids), are capable of affecting the strength of a person’s kick. In order to do this, we will be measuring the lengths of peoples’ legs and asking them to kick a football at a force meter as hard as they possibly can, in an attempt to test what could affect their kicking strength.

This will be done by us, group #7, composed of:

Bernardo Esteves

Julia Graça Aranha

Maria Costa

Gabriel Ayres

Pedro Leite

Carlos Tadeu Ribeiro

all on the 9th of November during the presentation of Class 10's Group 4 projects.