duxx,
Here’s another little bit.
++++
Fitness Testing Assignment: Australian Rules Football - by Greg Wooton
Contents
Introduction
Physical Demands
Energy Systems
Twenty Metre Shuttle Run Test
VO2 max
Repeated Sprint Ability
References
Introduction
Australian Rules Football (ARF) is a game unique to the Australian population in regards to the skills and rules involved. It can be compared to many team sports with regard to the physical requirements and energy systems involved in competition. The development of all three energy systems- aerobic, anaerobic and the lactic, is regarded as desirable in physical preparation to compete in ARF (Telford et al 1989 and Minikin 1990). Typically players must repeat many short (5-10 seconds) bursts of intense (near maximal) effort repetitively through the course of a game, with periods of lighter intensity effort interspersed. Physiological testing of players can be beneficial to both the players and coach to indicate individual strengths and weaknesses, and also as an objective measure of training responses (Ellis et al 1998).
Over the course of a game of ARF the player typically performs 100 or more sprints (Douge 1982). Some variability in the amount of running efforts have been reported particularly for different playing positions on the field. Wadley et al (1988) reports these high intensity efforts account for around 20 per cent of the game time, with average sprint distances of approximately 20 metres. The work to rest ratio is variable depending on the state of play and positional requirements. This requirement of repeated effort is similar to sports such as rugby, soccer, netball, hockey, basketball, squash and tennis. Besides the ability to reproduce short bursts of intense effort the player must be able to sustain performance over the length of the game, 100 minutes (4 x 25 minute quarters).
Although training is often concentrated on short repeated efforts, a poor endurance base will only serve to limit playing performance, particularly later in the game (Jenkins 1993).
The ability to keep producing high intensity efforts is dependent on the replenishment of the working energy systems and the maintenance of nutrient and oxygen supply to the muscles. Throughout a game of ARF a player has large periods of moderate and low intensity activity between intense efforts where the aerobic energy system has an important role in the replenishment of energy stores and the removal of accumulated by products of activity. A range of fitness and physiological tests has been developed to test the efficiency of the various energy systems that are utilised in a game of ARF. Before outlining these tests it is important to develop an understanding of skills required through a game.
Physical Demands
Australian Rules Football becomes extremely complex when 36 players (18 on each team) compete for possession of the oval shaped ball. Today’s football is seen as very much a running sport (Parkin et al 1987), where players must be able to not only run fast, but maintain their speed of running in short bursts over the entire game. Thus, both the factors of speed and endurance are important aspects of a footballer’s fitness.
The players general endurance (or what has been called stamina, cardiovascular fitness, respiratory endurance and aerobic capacity) is the capacity of the players heart, lungs and blood vessels to supply oxygen and nutrients to those muscles that are working, at a submaximal level, over a prolonged period of time (Parkin et al 1987). In football this equates to the player being able to run and continue to perform the skills required at a steady, yet high level for the entire length of the game. This aerobic capacity forms the basis upon which more specific forms of “fitness” can be developed, and is typically the first or “pre-season” goal of training.
In ARF, generally the sprint or acceleration is only over a short distance (approximately 20 metres), but is repeated up 100 times through a match. The power that a player is able to generate is dependent on muscle strength and speed - so resistance training to increase muscle strength and specific motor skills to increase speed can be beneficial. Given the physical nature of ARF strength is also crucial for a player to be able to withstand the buffeting and bumping of a game. A player needs to be able to tackle their opponent and drag them to the ground, hold ground, bump and physically match or better their opponent in these areas.
The aerobic capacity is closely related to the player’s ability to repeatedly sustain speed over a short distance over a period of time.
As with all sports the football team is a combination of players with various specific abilities - particular to the position they play. The mobile “following division” for example (ruckman, rover, ruckrover) need to have greater levels of running endurance as they are required to cover more ground than the more stationary positional players, where a full back may need greater levels of muscle strength to be able to match a strong, bulky forward opponent. The specificity and emphasis of the training program must be geared to the individual and the requirements of ensuing competition.
Energy Systems
Adenosine Triphosphate (ATP) can be considered the bodies energy currency, although its quantity is limited. When the terminal phosphate bond of ATP is broken, the liberated free energy is harnessed to power all forms of biologic work (McArdle et al 1991).
ATP is synthesised from the food we eat, particularly fats and carbohydrates, through a series of chemical reactions that liberate the stored energy of the food nutrients. Various pathways are utilised to produce ATP - both aerobic and anaerobic.
ATP-CP Energy System
Activity of short duration and high intensity, such as the repeated sprint efforts of ARF, require an immediate supply of energy. The high energy phosphates of ATP-CP (Adenosine Triphosphate- Creatine Phosphate) sytem, which are stored locally in the specific muscles, provide this energy. These stores are depleted rapidly depending on the duration and intensity of the exercise, after about six seconds of sprinting (McArdle et al 1991), and may significantly affect one’s ability to generate immediate high intensity performance. To replenish these high energy phosphate stores following sustained or high intensity effort, energy must be generated for ATP resynthesis. Replenishment is a continual process involving the aerobic metabolism of carbohydrate, fat and protein stores and the anaerobic lactic acid system.
Lactic Acid System
The anaerobic process of glycolysis transfers energy from the metabolism of glucose and glycogen to allow resynthesis of high energy phosphates (ATP-CP) to meet energy demands. The lactic acid system provides rapid energy, above that stored in the high energy phosphate stores within the muscle, for intense efforts of longer duration. If exercise intensity and duration is miantained relative tissue hypoxia or local oxygen deficiency is thought to occur. The energy requirements are thus predominantly met by anaerobic glycolysis and the level of hydrogen ions, that would normally be removed through oxidation, increases and lactic acid accumulates. ATP is continually and rapidly formed anaerobically, resulting in the formation of lactic acid as a byproduct, as the demand for energy outstrips the capacity for aerobic resynthesis of ATP.
Aerobic System
The immediate energy for muscular work is provided by the non-oxygen consuming breakdown of ATP in the muscle. The aerobic (oxygen consuming) system becomes important and is the main contributor of energy for prolonged activity or exercise (duration greater than 2-3 minutes). Both carbohydrates and fat can be metabolized for energy production via the oxidative pathways. Although not directly involved in ATP synthesis, oxygen acts to accept hydrogen and electrons which if not utilised or removed then lactic acid accumulates. The maximal energy supply of the aerobic system is determined by the body’s ability to supply and utilise nutrient and oxygen to the exercising tissues’ locally as the presence of oxygen largely determines the capability for sustained aerobic energy release (McArdle et al 1991).
Three essential components must be met for the continual resynthesis of ATP - a donor of electrons, enzymes to facilitate the metabolic reactions and adequate oxygen. A steady state is achieved when the energy required by the working muscles matches the rate of ATP production via the aerobic metabolism (McArdle et al 1991). Increased energy demands or reduced aerobic metabolism may lead to oxygen deficit and the accumulation of lactic acid.
These energy systems are inter-related and there is considerable overlap of one system to the next to meet energy demands. At one extreme a short burst of high intensity effort such as the high mark or sprint, is supplied almost entirely by the ATP-CP system, while the light and moderate intensity periods place demands on the aerobic system, to provide energy, remove by-products, and to replenish the ATP-CP system stores through aerobic metabolism.
Twenty Metre Shuttle Run Test
This continuous multistage test was first introduced as a field test to predict VO2 max and cardio-respiratory fitness and has been modified and refined over the years. These tests are progressive in nature but still require the subject to be working maximally at the end of the test. Due to the complicated nature of direct VO2 max testing, the equipment required and the limitations of funding and time, alternative predictors of VO2 max are commonly used.
The 20 metre Shuttle Run Test (20mSRT) is user friendly in that the equipment required is minimal, multiple subjects can be tested simultaneously and the test has been shown to be reliable (St Clair Gibson et al 1998). Several slight variations in methodology conducting the test are described in the literature - these differences are negligible for intra-team testing as long as a standardised protocol is maintained. These differences may need to be considered when comparing data and results across testing procedures and locations.
A distance of 20 metres is marked on the ground, and to specify this test to ARF this is recommended to be on a grassed oval or surface to replicate playing conditions. An audio cassette or compact disc (available from the Australian Sports Commission) dictates the pace of the test by emitting tones at appropriate intervals. The subject is required to be at one of the other ends of the 20 metre course at the audio signal. A start speed of 8km/hour is described by Paliczka et al (1987), whereas a start speed of 8.5km/hour is described by St Clair Gibson et al (1998). The start speed is maintained for one minute before the speed is increased 0.5km/hour every minute thereafter. The test score achieved is the number of 20 metre laps completed before the subject either withdraws voluntarily from the test or fails to be within 3metres of the end line on 2 consecutive audio tones. VO2 max is derived by the formula: y= 6.0x - 24.4 Where y equals the predicted VO2 max and x equals the maximum speed achieved (St Clair Gibson 1998).
Comparisons of the 20mSRT predicted VO2 max to direct evaluation of VO2 max showed high correlation, indicating the 20SRT is a valid indicator of aerobic power in various populations, and that it mayb be used as an accurate alternative to predict VO2 max (Paliczka et al 1987 and Ramsbottom et al 1988). St Clair Gibson et al (1998) found the 20mSRT underpredicted VO2 max compared to direct gas analysis results. They concluded that in their homogenous population with a narrow range of values the prediction was less reliable than in a population with a diverse range of VO2 max values.
Several factors that may effect the validity of the 20mSRT include differences in running economy, rate of onset of blood lactate accumulation and the training status of the individual (Ramsbottom et al 1988). In relation to testing ARF players these factors may all be anticipated and considered by the coaching staff. The advantages of this test to this population are numerous: specificity of task to actual sport (running, change of direction), the constant environmental conditions, absence of need for pacing or pace judgement, the graded physiological response, high reliability and validity and large numbers can be tested simultaneously.
VO2 max
Maximal oxygen uptake reflects the ability of the cardiovascular system to deliver oxygen to the working muscles. A variety of work tasks that activate the large musckle groups, sustained for sufficient duration at sufficient intensity, may engage maximal oxygen transfer - VO2 max (McArdle et al 1991). For the ease of application of apparatus treadmill running and walking, cycling and bench stepping procedures are commonly used. The VO2 max test may be performed via a continuous supra-maximal effort or exercise consisting of progressively graded increments to the point where the athlete will no longer continue to exercise.
Prior to testing the subject is familiarised with treadmill running. The subject is fitted with a gas analysis device that monitors all inspired and expired gases and, given a known gas concentration temperature and humidity, calculates the oxygen and gaseous exchange throughout the test procedure.
There is some variation in the exact methods of VO2 max testing described in the literature. The exact speed of the treamill (both initial and progressive) and the gradient of the treadmill (initial and progressive) are somewhat variable. An initial treadmill inclination of 3.5 with progressive 2.5 degree inclination every three minutes is described by Ramsbottom et al (1988). An initial flat treadmill with progressive 2.5 per cent inclination every minute (Paliczka et al 1987) and 2.5 degrees every two minutes until 20 degrees has also been described. The essential component of the VO2 max test is not the gradient or speed but that the subject “peaks over”.
To be confident that a subject has attained their maximum capacity for aerobic metabolism (VO2 max) a leveling off or peaking over in oxygen uptake should occur (McArdle et al 1991). The attainment of this peaking over substantiates VO2 max has been achieved. Other similar criteria based on oxygen consumption that are indicative of VO2 max have been suggested. Blood lactate levels in the vicinity of 80mg per 100ml of blood have been reported to indicate maximal aerobic capacity but there are obvious difficulties in blood sampling. A respiratory exchange rate (ratio of carbon dioxide produced to oxygen consumed) in excess of 1.0, the attainment of age predicted heart rate maximum and a plateau of oxygen consumption despite an increase in work rate are also said to indicate achievement of VO2 max (McArdle et al 1991).
Many factors may influence an individual’s performance of a maximal aerobic capacity test. The specificity of the test procedure to the athletes training or competition mode may affect the results indicating that it is preferable to align the test procedure to the athlete’s requirements. Running for example, rather than cycling, is the more appropriate test in ARF population. Similarly body composition, lean body mass, body fat and overall size, affect the results attained from VO2 max testing. A 2.00 metre ruckman is expected to produce a higher VO2 max result than a 1.50 metre rover with out necessarily indicating a greater aerobic fitness level. It is generally more meaningful to assess the data in relation to body mass, hence results are generally reported as volume of oxygen consumed per kilogram mass per minute.
Repeated Sprint Ability
As previously discussed, ARF involves sustained light and moderate intensity activity over a period of 100 minutes, with a series of contests involving high intensity efforts. These efforts deplete the high energy phosphate stores and may lead to the accumulation of lactic acid in the muscles and blood. The ability of the player to keep producing near maximal high intensity efforts is dependent on the replenishment of the CP system and the removal of the metabolic byproducts such as inorganic phosphates and hydrogen ions (Wadley et al 1998). The repeated sprint ability test (RSA) is specifically designed to test the athlete’s ability to perform in short bursts of high intensity exercise over a series of multiple efforts.
A single high intensity effort of 5-10 seconds duration is reported to put demands on the phosphagen energy system and its importance appears to increase over a series of repeated efforts (Wadley et al 1998). Early RSA tests involved repetitions in the order of twenty sprints but it became apparent that the high number of repetitions necessitated the subjects to pace themselves to some degree in order to complete the test. Initially Dawson et al (1991) recommended eight to ten repetitions of five second sprints every 30 seconds, high enough to be challenging but enabling a maximal performance to be maintained. Dawson et al (1993) has also described a repeated sprint test involving six 40 metre maximal sprints starting every 30 seconds geared towards testing ARF players. Wadley et al (1998) investigated an RSA involving twelve 20 metre sprints, starting every 20 seconds. The reduced recovery time was designed in attempt to specifically replicate the energy demands of ARF. The average work to rest ratio (including the time of deceleration as work) ranged from 1:2.3 to 1:2.7.
The total sprinting time was calculated by the summation of the twelve sprint times. A repeated effort performance decrement was calculated by dividing the total time for the twelve sprints by the best possible total score (the best 20 metre time multiplied by twelve) and multiply by 100. The performance decrement is suggested to represent the degree of fatigue and the individual’s ability to recover quickly (Dawson et al 1993 and Fitzsimmons et al 1993). Similar performance decrements have been reported after investigations by Dawson et al (1993), Fitzsimmons et al (1993) and Wadley et al (1998), with a range from 5.3 to 5.6 over the three studies. This range of results can be considered as normative for a trained but not elite population.
It has previously been discussed that short high intensity efforts place demands on the ATP-CP energy system. It is agreed that the strong relationship between the single best 20 metre sprint time and total sprint time suggests that the ATP-CP system is the major contributor to the energy demands of the RSA test. Although both the single best sprint and the total sprint time may be an indicator of aerobic power the RSA also provides beneficial information in regard to the amount of fatigue experienced with repeated efforts (Dawson et al 1993 and Wadley et al 1998).
A strong correlation between the single best sprint and the performance decrement has also been reported (Wadley et al 1998). It is proposed that subjects who can produce higher peak power outputs and subsequently better “best” sprint times are able to do so due to an increased ability to utilise the available ATP-CP stores. With the increased utilisation and lack of recovery to allow replenishment of stores, fatigue becomes a more significant factor with repeated efforts.
A strong correlation of VO2 max and performance decrement was observed in Dawson et al (1993) study of RSA tests, demonstrating the importance of the aerobic system in the level of fatigue experienced. With a more efficient aerobic system, that produces a greater degree of ATP-CP replenishment between efforts, less demands are placed on the lactic acid energy system in subsequent efforts. It is conceivable that improvement in aerobic power may augment performance of the RSA by increasing the rate of ATP-CP replenishment and lactate removal.
References
Dawson B, Ackland T, Roberts C and Lawrence S (1991)
Repeated effort testing: The phosphate recovery test revisited. Sports Coach 14:12-17.
Dawson B, Fitzsimons M, and Ward D (1993)
The relationship of repeated sprint ability to aerobic power and performance measures of anaerobic work capacity and power. Australian Journal of Science and Medicine in Sport 25:88-93.
Ellis L, Gastin P, Lawrence S, Savage B, Sheales A, Stapff A, Tumilty D, Quinn A, Woolford S and Young W (1998)
Testing protocols for the physiological assessment of team sport players. In Australian Institute of Sport Test Methods Manual. Belconnen National Sports Research Centre Chapter 9.
Fitzsimons M, Dawson B, Ward D and Wilkinson A (1993)
Cycling and running tests of repeated sprint ability. Australian Journal of Science and Medicine in Sport 25:82-87.
Douge B (1982)
Testing in Australian rules football. Sports Coach 6:29-34.
Jenkins D (1993)
The importance of aerobic fitness for field games players. Sports Coach 2:22-23.
Leger LA and Lambert J (1982)
A maximal multistage 20-m shuttle run test to predict VO2max. European Journal of Applied Physiology 49: 1-12.
McArdle WD, Katch FI and Katch VL (1991)
Exercise Physiology: Energy, Nutrition and Human Performance (3rd ed.). Philadelphia:Lea and Febiger.
Minikin B (1990)
Hints for coaches on interpreting the trilevel profile of general fitness. Sports Coach 3:19-23.
Paliczka VJ, Nichols AK and Boreham CAG (1987)
A multi-stage shuttle run as a predictor of running performance and maximal oxygen uptake in adults. British Journal of Sports Medicine 21:163-165.
Parkin D, Smith R, and Schokman P (1987)
Premiership Football: how to play, train, and coach Australian football (2nd ed.). Melbourne:Hargreen.
Ramsbottom R, Nevill M, Nevill A and Hazeldine R (1997)
Accumulated oxygen deficit and shuttle run performance in physically active men and women. Journal of Sport Sciences 15:207-214.
St Clair Gibson A, Broomhead S, Lambert MI and Hawley JA (1998)
Prediction of maximal oxygen uptake from a 20 m shuttle run as measured directly in runners and squash players. Journal of Sports Sciences 16:331-335.
Telford R, Minikin B, and Hahn A (1989)
A simple method for the assessment of general fitness: the tri-level profile. Australian Journal of Science and Medicine in Sport 21(3):6-9.
Wadley G and Le Rossignol P (1998)
The relationship between repeated sprint ability and the aerobic and anaerobic energy systems. Journal of Science and Medicine in Sport 1:100-110.
Woodman L and Pyke F (1991)
Periodisation of Australian football training. Sports Coach 2:32-43.
This article and some other interesting titles can be found here: http://physiotherapy.curtin.edu/resources/educational-resources/exphys/99/
… I wrote this in about 15min so there may be some serious errors but it will be good as a starting point for discussion!
so this is not the problem at all!