Introduction as 13km have been reported (Shephard and

Introduction

Football is a sport characterised by intermittent activity that includes
high-intensity anaerobic efforts superimposed on a background of aerobic
activity. Football places a large demanded on the body through various tasks.
The sport requires a wide range of physical components and skills to support
play. 

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Match analysis shows that the total distances covered during a 90-minute
game can range from 9,845-11,527 metres (Andrzejewski et al., 2012) Although,
distances as large as 13km have been reported (Shephard and Astrand, 1994).
This distance is covered at various speeds; walking (25%), jogging (37%),
sub-maximal cruising (20%), sprinting (11%) and tracking backwards (7%)
(Shephard & Astrand, 1994). Studies have also shown that the average
intensity exceeds 70% VO2 Max (Bangsbo, et al., 2006).

 Due to vast position related differences and specific needs,
athletes can perform at various intensities during game-play.  This essay will analyse the full back
position in football in relation to the physical qualities needed to ensure
that appropriate training parameters are set. 
In addition, an analysis of injuries will be discussed in order that
training might be planned around their prevention.

Physiological needs

Athlete’s level of play can be assessed by their physical capabilities
(e.g., aerobic and anaerobic capacity, speed, strength, and power). Players
must adapt to requirements of the game to be successful as the level of
competition increases. Football players need to achieve a reasonable balance in
the improvement of physiological and physical capabilities which is relevant to
the level of competition and positional role (M. Svensson, B. Drust, 2005).

Strength and stability 

Full back defenders are arguably the most physical players on the pitch
due to their specific job role of having to protect their goal and preventing
opponents from getting into beneficial areas. Male professionally ranked
defenders tend to have a high level of upper extremity strength along with
lower extremity strength, both assist the ability to compete when jumping in
the air for a header or when placed in the wall defending a free kick. There
are clear advantages in having both strength and stability in various planes of
movement for athletes in this position.

Endurance 

The full back position partakes in multiple quick, explosive movements
that last a moderate duration, interspersed with periods of rest and
sub-maximal activity.  A desired
physiological trait needed to cope with football’s physical demand is
high-levels of physical fitness. This allows players to use their technical and
tactical attributes effectively, whilst resisting fatigue all-game long
(Krustrup, P. and Bangsbo, 2001) specifically, speed, muscular and
cardiovascular endurance support the main role the full back is tasked with.

Energy systems and capacity 

Defenders rely on their aerobic system for recovery in-between these
bouts of actions. In the modern game, top football players complete around
150-250 short duration, intense actions (sprints, shooting, tackling etc.)
throughout a game (Mohr et al., 2003). This could suggest that the rate of
anaerobic energy production will vary from low to high throughout a game. The
dominant energy will be sourced from the aerobic metabolism but in contrast the
most purposeful actions are likely to be performed in an anaerobic nature
(Wragg, Maxwell, & Doust 2000). Periods of intense exercise lead to a high
rate of phosphocreatine breakdown. In some respect PCr is resynthesized in
lower-intensity periods (Bangsbo, 1994), therefore the research suggests that a
good athlete will have a high aerobic capacity, as well as the ability to
recovery quickly from short anaerobic actions. Centre backs will benefit hugely
from understanding and training repeated sprint capacities.

Biomechanical analysis 

Football consists of multiple movements. The basic movements are; different
speeds and direction of locomotion and skill based tasked. These skills are:
passing, receiving, dribbling, shielding, shooting, heading, tackling and
intercepting. Kicking is the most prominent skill, it is the most analysed due
to the many different variations and ways to execute it, for example, the
speed, height, position of the foot during contact. While the instep on the
approach to the ball is said to provide the maximum force on the stationary
ball. 

There are 6 stages to a football kick which should be analysed, these
are:

The approach

Plant-foot forces

Swing-limb loading 

Hip flexion and knee extension

Foot contact

Follow-through

 

Table 1: Muscular action during kicking preparation 

 

Body Part

Action

Muscles

Trunk

Stabilisation of the right foot
rotation

Abdominals, psoas major,
erector spinae and spinal
postural muscles

Right hip

Extension 

Gluteus maximus and hamstring group

Left hip

External rotation and eccentric
extension

Gluteus med, gluteus minor,
hamstring group and adductor
magnus

Right knee

Flexion

Hamstring group and popliteus

Left knee

Eccentric extension

Quadricep

Right ankle

Plantarflexion

Plantarflexors

Left ankle

Eccentric plantarflexion

Plantarflexors

Left shoulder

Abduction

Middle and anterior deltoid and supraspinatus

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 2: Muscular action during approach and
kick

Body part

Action

Muscles

Trunk

Stabilisation

Abdominals, psoas major, erector spinae and spinal postural muscles

Right hip

Internal
rotation/Hip flexion

Tensor fascia lata,
rectus femoris, psoas, iliacus, sartorius and adductor group

Left hip

Extension

Gluteus maximus, hamstring group and adductor magnus

Right knee

Extension

Quadricep group

Left knee

Extension

Quadricep group

Right ankle

Plantarflexion

Plantarflexors

Left shoulder

Horizontal adduction

Anterior deltoid,
biceps brachii, pectorals major

 

Table 3: Muscles used in the swing limb
loading phase

Body Part

Action

Muscles

Right Hip

Extension and abduction. Also external rotation

Gluteus maximus, gluteus medius work
concentrically

Right knee

Flexion

Concentric contraction of the biceps femoris and concentric
contraction of the semitendinosus and semimembranosus

Right ankle

Plantarflexion

Concentric contraction of gastrocnemius

 

Table 4: Muscles used to produce the actions
around the downward swing

Body part

Action

Muscles

Right Hip

Flexion 

Concentric contraction of the iliacus, psoas major and psoas minor and
the rectus remorus (Putnam, 1983)

Right Knee

Extension

Knee extensors
(vastus lateralis) powerfully contracting

Right Ankle

Plantarflexed

Gastrocnemius contracts concentrically

Left Arm

Adducts and
horizontally flexes

Deltoid and
latissimus dorsi

 

 

Table 5: Muscular action of the kicking leg during
the follow through

Body Part

Action

Muscles

Right Hip

Eccentric external rotation, eccentric extension
and eccentric abduction

Hamstring group, posterior fibres of gluteus
medius, quadrates femoris, piriformis and gluteus maximus

Right Knee

Eccentric flexion

Hamstring group

 

 

The kick beings with the approach up to the ball. Isokawa and Lees (1998)
have shown a 45-degree approach angle produces the greatest peak ball velocity
because of the greater pelvic rotation enabling a larger range of motion, as
opposed to a 15/30-degree angled run up. The position of the foot plant
determines the balls path (Hay, 1996). The trajectory is determined by the
anterior-posterior position of the foot plant. The ideal foot position is
perpendicular to the centre of the ball and 5-10cm to the side of the ball, allowing
for a straight ball path (Abo-Abdo, 1981). The athlete must insure they create
a steady base of support during the foot plant. This can be achieved by
ensuring their centre of mass is over their base of support to maintain balance
(Blazevich, 2012). The swing limb loading phase is the preparing of the leg for
the downward motion towards the ball. The motion is a proximal to distal
sequence involving segmental motion of the lower limb (Levanon and Dapena,
1998). The downwards motion is where all the energy stored through the
backswing is used in contact with the ball. During the foot contact 15% of the
kinetic energy gets transferred to the ball from the swinging limb. The
remaining energy dissipates by the eccentric activity of the hamstring to slow
the leg down (Gainor, B, Pitrowski, G, and Puhl, J 1978). This phase is the
deceleration of the kicking leg. Two purposes come from this phase, firstly to
increase the time the foot is in contact with the ball, and secondly to protect
the leg from injury. As for all ballistic movements, the longer contact time
will give the maximum amount of momentum to the ball and therefore increase its
speed (Barfield, B 1998). The body reduces the risk of injury by dissipating
the kinetic and elastic forces generated by the swinging leg after contact.
However, sudden attempts to slow the limb would increase the risk of injury.

Injury epidemiology

There are two major dangers in regard to the kicking movement. These are
hamstring strains and impingements of the posterior ankle, with Osteitis pubis
being an additional danger, which is the inflammation of the pubic symphysis
and surrounding muscle insertions (Brukner, P, and Khan, K 1993). Hamstring
injuries can occur for three reasons. Firstly, when a muscle contracts hard
against resistance. The second involves pulling a muscle excessively at a
specific angle and direction. The last involves the contraction of a muscle
excessively when it is not prepared to contract. For a defender this might be
when an attacker quickly changes a direction and the defender tries to shadow
the player’s movements at a fast pace causing hard contractions and movement at
specific risky angles. 

Sprains are also common for defenders, usually in the knee, lower leg or
ankle. The anterior cruciate ligament is the most common ligament injured in
the knee. Pivoting and lateral movements cause these injuries. Closed head
injuries are often caused by a collision between players, these are common for full
backs due to their job of heading the ball and protecting the box from crosses
and free kicks, also injuries to the head could be due to improper technique
when it comes to heading the ball. The proper technique for heading consists of
the use of the forehead to contact the ball, and the correct use of the neck
muscles to reduce flexion and extension of the neck to minimise head motion,
using the leg muscles instead to advance in the air.  

It seems that the most frequent injuries in football are muscular. Jan Ekstrand, carried out a study to
‘investigate the incidence and nature of muscle injuries in male professional
footballers’. The study consisted of fifty-one football teams with a total of
2299 players. They were followed during the years 2001 to 2009. Each team’s
medical staff recorded individual player exposure and time-loss injuries.
Muscle injuries were defined as “a traumatic distraction or overuse injury to
the muscle leading to a player being unable to fully participate in training or
match play.” 2908 muscle injuries were measured per season. Thus a squad of 25
can expect around 15 muscle injuries per season. These injuries constituted 31%
of all injuries and caused 27% of the total injury absence.

Ninety-two percent of all muscle injuries affected the 4 major muscle
groups of the lower limbs: hamstrings (37%), adductors (23%), quadriceps (19%),
and calf muscles (13%). Interestingly 16% of these were re-injuries. These
caused longer absences that the index injuries. Results showed that the
incidence of muscle injury increased with age, but only for calf injures and
not for hamstring, quadriceps, or hip/groin strains. 

Conclusion

A review of the literature around the full back has
shown that the physical qualities needed to succeed in this position are
multi-faceted.  The full back must have a
high tolerance to aerobic activity as well as being able to recover quickly
from short anaerobic actions. Strength and agility are major players in a
defender’s arsenal because of the amount of physical contact they have with
opposition players both on and off the ball. 
The threat of injury is high and therefore careful consideration should
be given to pivotal and lateral movement training to reduce risk of ACL
damage.  In addition, training should
revolve around the development of muscles that are conditioned to respond to
forceful, sudden changes of length and angle of force. Finally, level of competence
and age should also be taken into consideration when planning a training
programme for a full back.

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