Football coaching: Ball kicking

Football coaching: Ball kicking

Football coaching: a new measure of kicking accuracy

Frustrated by the limitations of existing methods for assessing kicking accuracy – clearly a vital component of soccer performance – a research team from Minnesota in the US set out to develop and test a sensitive, reliable and valid means of measuring kicking accuracy that was relatively inexpensive, simple to make and easy to use.

The result of their endeavours was a plywood target 243.5cm wide and 122cm high, held in an upright position from behind by a wood plank frame. The surface of the plywood was covered with a textured white paint, while a black mark measuring 5cm squared (the bull’s-eye) was placed at the midpoint of the base of the board. A screw was placed in the middle of the bull’s-eye in such a way that a hook at the end of a tape measure could fit over the head of the screw with a view to precisely measuring the distance from the bull’s-eye to the centre of the mark left where the ball struck the target.

Sheets of white paper covered by carbon paper were placed over the board, such that when the soccer ball struck it left a mark on the underlying white paper. For each new kick a new sheet of paper-plus-carbon was used.

To test the accuracy of the system, 10 ball marks were created on the target by having a subject kick a football at it 10 times from a distance of 6.1m. Two ‘raters’ then independently measured the distance from the bull’s-eye to the centre of each ball mark, each taking the marks in a different random order. They then repeated their measurement on the same day, taking the marks in a different random order.

Analysis of the results showed a high degree of inter- and intra-rater reliability in measurement, with distances from the bull’s-eye to the ball mark (ranging from 25.7cm to 150.75cm) accurate to within 0.15cm.

‘These results suggest that our method for assessing kicking accuracy is a useful, valid and reliable tool for analysing performance in soccer players,’ state the researchers. ‘To our knowledge, no other tool has demonstrated reliability…Measurements were made to within 0.15cm, suggesting that the target is sensitive to change in kicking accuracy. Such targets may also be useful in sports other than soccer, such as lacrosse, ice hockey, field hockey and …handball.’

This particular device was tested indoors in a gym. But the researchers point out that game situations could be simulated more accurately by using defenders or a goalie against the player kicking at the target, placing it on a playing field – although not in rain or extreme wind – and/or making it larger to replicate the size of an actual goal (244x732.5cm).

Training and research are the two main applications of the target, they conclude. The bull’s-eye could be moved to different places on the target, allowing players to practise kicking to specific spots. Each player’s accuracy could be determined for each spot, and regions to which the player does not kick accurately could become a primary focus of training. The target could then be used to measure improvements in accuracy over time.

Journal of Science and Medicine in Sport 5(4):348-353

Isabel Walker

Genetics

Metabolic rate: sports training has a significant effect on weight gain and weight loss

The effects sports and fitness training has on our metabolic rate and calorific needs

Metabolic rate basically refers to the energy that is released by the body.

Sports training can have a significant effect on metabolic rate – this can determine weight gain and weight loss. This is because it boosts calorie burning. This is a result of 1) doing the activity itself 2) the effects of a process known as ‘excess post oxygen consumption’ (EPOC) – of which more later – and 3) by creating a body whose constituent parts (specifically muscle) create an all day and every day increased calorie requirement (again of which more later).

Metabolic rate is comprised of:

Total Daily Energy Expenditure (TDEE)
This refers to all the energy we expend over a day

Resting Metabolic Rate (RMR)

Thermic Effect of Feeding (TEF)

Activity
This may be a surprise but only 10-15% of our total daily energy expenditure comes from physical activity of any sort. However, this relatively small amount can have a huge effect on our body composition, i.e. how much fat we have and how many calories we need to optimally sustain ourselves and our sports/fitness training

How do you know how many calories you are burning during exercise?

When we exercise we increase our metabolic rate as our body boosts its energy output to meet demand. Calories measure the energy release from food (see box).

Research has provided the calorific requirements of numerous sports activities. It should be noted that although these figures are relatively accurate, they vary in regard to:

Your weight. A heavier person will burn more calories, everything else being equal compared to a lighter one, simply because more energy is required to overcome the greater resistance.

Your level of fitness. Someone who is fitter, for example, at rowing will be more ‘energy (and therefore calorie) efficient’ than someone who is less fit. This is why exercise intensity needs to be continually increased (progressively) if increased calorie burning is your objective, for example, in order to achieve a weight loss goal (or negative energy balance – of which more later).

Atmospheric conditions. The body will burn more calories in hotter, humid conditions than in temperate ones. This is due to the energy required to maintain its cooling processes and reduce core temperature

Body types. Certain people – particularly those with lean wiry frames (‘ectomorphs’) – tend to have faster metabolic rates, which can enhance calorie burning.

Metabolic rate generally slows with age, sports and fitness training can do much to challenge this.

Table 1 displays the calories burned during various sport and fitness activities. It will be of use to athlete and coach in terms of calculating calorific expenditure

How to calculate metabolic rateFollowing the steps below will enable you to gain an indication of the calorific value of your metabolic rate

Step 1 Calculate your RMR

Age:	18-30 Multiply your weight in Kg x 14.7 and add 496	31-60 Multiply your weight in Kg x 8.7 and add 829
Example:	65Kg Individual 65 x 14.7 + 496 = 1451.5 RMR	65 Kg Individual 65 x 8.7 + 829 = 1394.5 RMR

Step 2 Estimate your daily activity requirements in calories

Multiply your RMR by your daily activity level as indicated by one of the figures in the table below

Sports and fitness training can increase metabolic rate by as much as 20%. This is due to EPOC. Unlike a car when the ignition is turned off, our body’s engine does not stop immediately after we have taken it for a run, row or performed a weights workout. The processes involved in producing the energy required for these and all other sports, fitness and general activity, take a while to slow down and return to base line levels. These processes include, the restocking of muscle fuel (notably a specific type of carbohydrate, known as glycogen) and the normalisation of lactate levels in our body. Lactate is used in energy creation at all times. Its levels increase with exercise. When we stop exercising it is still buzzing around inside us at a great rate. It needs time to slow down and in some circumstances be re-converted back to its original chemical format – and this all requires energy. Additionally, when we workout, particularly using weights, microscopic tears occur in our muscles and it is during the recovery period when these are repaired and our muscles grow stronger – again this requires energy. The more the intense the exercise the greater the EPOC.Sports scientists have discovered two distinct EPOC phases:EPOC phase 1The most significant – in terms of calorie burning – occurs in the two to three hours after training. The less significant given the same criteria lasts up to 48 hours after training.If you do not factor EPOC in to your calorie requirements you could experience muscle loss, lack of energy and a failure to obtain sufficient amounts of vitamins and minerals needed to optimally maintain bodily processes. Basically your body would be running ‘energy light’ – not getting enough fuel to optimally power it.Table 1 Energy expenditure and exerciseEnergy expenditure in calories per minute for selected activities against selected body weight (Kg)

Note: women may not benefit to the same extent as men from increased lean muscle mass calorie burning. This may reflect their naturally higher levels of body fat – with the latter cancelling out the gains made by the former

A Kilocalorie (Kcal) represents the amount of energy needed to increase the temperature of 1Kg of water by 1 degree centigrade and is the unit commonly used to measure the energy released from food or burned in sports activities. As in this article, Kilocalories are often referred to simply as ‘calories’. Food packaging also gives energy release in kilojoules (kJ), the international standard for energy. To convert Kcal to kJ, multiply by 4.2 and to convert kJ to Kcal divide by 4.2.

Article at a glance:

The classification of body types is made;

The relationship between body types, sports suitability and sports performance is identified;

Other factors influencing sports performance from a physiological perspective are presented.

The human body comes in a huge array of different shapes and sizes, but should your natural body type dictate the sport you choose or the way you train? John Shepherd looks at the evidence and in particular whether it’s nature or nurture that really countsIn a particular sport or event within a sport, the participants will often share a similar body shape. For example, male sprinters tend to be relatively tall and be proportionately muscled, whilst female gymnasts tend to be relatively slight with very low body fat and shot-putters relatively round with more body fat and large muscles. These sports’ body shapes quite closely reflect the three derivative ‘somatotypes’ (body type classifications). The sprinter fits the typical mesomorph body type, the gymnast the ectomorph, and the shot-putter the endomorph. In this article, we’ll consider the relationship between body types, sports performance and training response.

Although his work is perhaps overstated it provides a useful starting point for the analysis of male and female body types. This is because it’s possible to identify the ways that these types will typically respond physiologically to training and the way they are represented across various sports.Most athletes (and non-athletes) are actually an amalgamation of the three main body types and there is a further level of somatotype classification that describes a body type in terms of ‘parts’ of the three. This is known as ‘dominant somatotype’. Sheldon identified ‘seven parts’, 1-7 for each somatotype, with 1 being the minimum and 7 the maximum number of parts attributable to that somatotype. For example, 2-6-3 indicates low endomorphy, high mesomorphy and low ectomorphy (note variations to this system exist which use decimal points). The panels on this page describe the three main body types more fully.

Athletes often seem to fit a blueprint for their sport and numerous research findings appear to confirm what common sense suggests. Greek researchers looked at the somatotypes (as well as body composition and anthropometric measurements) of 518 elite Greek basketball, volleyball and handball players(1). The team discovered that the volleyball players were the tallest and had the lowest levels of body fat. Their somatotype was characterised as ‘balanced endomorph’ (3.4-2.7-2.9). Basketball players were taller and leaner than handball players. The former were profiled as mesomorph-endomorph (3.7-2.7-2.9). The latter were profiled as mesomorph-endomorph also but their ratio was identified as 4.2-4.7-1.8.

Body composition

The ratio of lean (muscle) mass to fat (non lean weight)

Anthropometric measurements

Specific measurements of limbs and body parts

Overtraining syndrome

Identified state of health when the athlete will negatively adapt to training, become injured or ill

Delving deeper, the researchers also considered level of performance, as the athletes represented both the first and second divisions of their sports. Interestingly it was discovered that the first division players were taller, heavier, but leaner than the second division players. Even more interesting was the fact that players from all the three sports displayed a greater similarity between somatotype characteristics. It is possible that this similarity could be attributed to that particular somatotype balance making for ‘better’ players.

American researchers went a little further than their Greek counterparts by looking at somatotype differences within a sport(2). Specifically, they considered 168 elite basketball players. The team discovered that there were considerable differences between playing positions; guards had greater mesomorphy than centres, and less ectomorphy than forwards and centres.

Serbian researchers took up the theme of this research and basketball was again the sport of choice(3). Interestingly the conclusions on somatotypes by the Greek researchers were somewhat different than those reached by their Serbian counterparts (of which more later). The particularly interesting aspect of this research was the inclusion of the relationship between physiological capability and body type across a number of measures.

The 60 players surveyed came from five clubs in the Serbian first division. Physiological testing of the players was carried out during the final week of their pre-season training. Players were categorised according to court position. Here’s what the researchers found:

Centres were taller and heavier than guards and forwards;

Forwards were taller and heavier than guards;

Centres carried more body fat than guards and forwards;

Centres had lower estimated VO2max values compared to forwards and guards;

Guards’ heart rates did not reach the same levels of centres and forwards during the last minute of a bleep test;

Centres had better vertical jump power than guards.

These findings led the researchers to conclude that ‘The results of the present study demonstrate that a strong relationship exists between body composition, aerobic fitness, anaerobic power and positional roles in elite basketball.’