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There has been a significant change in the body mass of elite rugby players over the past 30 years, with the increase being greater than what would be expected for the normal upward trend in the population.
There are many studies which have examined the physical characteristics of elite, amateur, adolescent and pre-adolescent rugby players. Collectively these studies show that there is a clear distinction between forward and backline players with respect to stature and body mass, and furthermore that average body mass is higher among players of greater proficiency.
This pattern is also shown at the annual Craven Week schools tournament, where the average mass of the players has increased by almost 10 kg (6.6%) since 1968.
Table 5: Average mass (kg) of the players at Craven Week. Data are shown as 95% confidence intervals around the mean. Mean 95%- 95%+ number
This is in contrast to stature (Table 6), which has only increased by 1.7% during the same period.
Table 6: Average stature (cm) of the players at Craven Week. Data are shown as 95% confidence intervals around the mean. Mean 95%- 95%+ number
It is logical to assume that the accelerated increase in body mass over the past 30 years can be attributed to better knowledge and implementation of programmes involving nutrition, supplements and resistance training.
New laws and difference in sizes
One study also shows that forwards have become slightly shorter, whereas backline players have become taller. It may be speculated that the decrease in stature of the forwards coincides with the introduction of the law permitting lineout jumpers to be supported in the lineout.
This law allows good lifters to overcome slight disadvantages in the stature of the jumper. This law also introduced new requirements for successful lineout play, such as visual acuity, timing, and the ability to coordinate between the jumpers, lifters and hooker throwing in the ball.
The body mass of both forwards and backline players increased significantly (7.1% and 12.3%; forward and backline players) during this study.
Physical conditioning aspects for rugby
A well conditioned rugby player needs to have attributes such as endurance, speed, agility, power, flexibility and sport-specific skill.
Coupled with these characteristics, rugby players competing at a high level also have to have certain morphological attributes depending on their playing position. Within a team these characteristics may vary considerably, making the sport of rugby unusual compared to other team sports, in which the players within a team are generally more similar in their characteristics.
This variation also places unique challenges on the strength and conditioning trainer, particularly if the rules of the “specificity of training” are applied within each training session.
For example, the physical demands of a prop forward are quite different to the demands of a scrumhalf and it is understandable that their training programmes need to be specifically adapted.
The reason for training is to induce physiological and morphological adaptations, which either are associated with an increased performance (through either increased muscle power, increased ability to resist fatigue or increased motor co-ordination) or with a reduction in the risk of injury.
Although there is generally a positive relationship between training load and the physiological adaptations resulting in improvements in performance, the different aspects of fitness may adapt at different rates.
Fitness in rugby players
Peak fitness for rugby is attained when there is synchrony between the fitness characteristics identified as being important for the demands of rugby.
Whilst fitness will be compartmentalised in the following section for ease of discussion, it bears pointing out that all these aspects should be considered in context:
Strength
Muscle strength is defined as the ability to produce force. Whilst a minimal amount of strength is needed for normal daily activities, the demands of certain sports require well developed strength. In some sports, strength is needed just as a basic component of fitness, while in other sports (e.g. weightlifting) strength is the main outcome variable which determines success or failure in competition.
Strength can be increased by systematic resistance training using either specially designed machines or free weights. The manifestation of a player’s strength depends on muscle morphology and the motor system.
Strength can be increased without any change in muscle size, but in these cases it is dependent on adaptations in the neural system.
Increases in strength are transferred to sporting performances in varying amounts. For example, a weight-training programme increased squat one-repetition maximum by 21% and this increase in strength was accompanied by improvements in vertical jump performance (21%) and sprinting speed (2.3%).
Forwards, in particular, need strength and power for performance in the scrums, rucks and mauls. The forces produced during a vertical jump are related to forces produced during scrimmaging.
Power
Muscle power, which is a function of the interaction between force of contraction and the speed of contraction, is associated with the explosiveness of the muscle. The relationship between force and speed of contraction and the subsequent point at which peak power occurs, varies between athletes.
For example, peak power occurs between 50% and 70% of the maximum weight which can be lifted for one repetition (1RM) for the squat and between 40% and 60% of 1RM for the bench press.
A fundamental way of increasing muscle power is to increase maximal strength, particularly in untrained players.
Speed
Speed consists of a number of components, all of which are independent qualities; namely acceleration speed, maximum speed and speed-endurance. Performance in the 10 m sprint is influenced by acceleration speed, while performance in the 40 m sprint is dependent on both acceleration speed and maximum speed.
Speed can be improved by increasing a player’s power to weight ratio.
Plyometric training (i.e. countermovement jumps or loaded squat jumps) is effective for improving speed, but the effectiveness of this depends on the state of training of the players. Many of the short sprints in a rugby match do not produce the player’s maximum speed, as it takes about 30 m to reach the maximum speed.
Sprinting activities in rugby have to be considered bearing in mind changing of direction, methods of carrying the ball, and strategies to avoid contact with the opposition players.
Attacking players often have to sprint while carrying a ball. This has the potential to reduce their arm drive, an important characteristic of sprinting.
A study has shown that players can sprint fastest without the ball, while running with the ball under one arm is slower and running with the ball in both hands is the slowest.
The negative effect of slowing down while holding the ball in both hands, has to be weighed up against the advantages of being able to distribute the ball more efficiently when the need arises. All these aspects need to be considered during training and it is not only the player who can run fastest in a straight line who will have fully developed their sprinting advantage.
On average, forwards perform 13 ± 6 sprints per game, compared to be backline players.
The mean duration of sprints during a match for forwards was 2.5 ± 1.6 seconds compared to the 3.1 ± 1.6 seconds of the backline players.
Up to 78% of all the sprints during a match involved a change of direction. It has been recommended that during training and conditioning, players should accelerate from both standing and moving starts, reaching speeds in excess of 90% of the peak running speed.
Lastly, track sprinting technique training is not ideal for rugby as this neglects the need of the players to change direction, carry a ball and prepare for contact.
Acceleration
As many of the sprints in a rugby match are shorter than the distance required to reach maximum speed, the ability to accelerate and cover short distances then becomes an important characteristic which distinguishes the proficiency levels of players.
Acceleration into the contact zone, and running off a straight line have been identified as important characteristics of an effective ball-carrying performance.
Both these factors increase the unpredictability of the contact situation, putting more emphasis on the decision-making ability of the defender, and increasing the chance of an incorrect decision by the defender.
Muscle endurance
Muscle endurance is dependent on the muscle being able to contract repetitively without developing fatigue.
A combination of muscle strength, metabolic characteristics and local circulation in the muscle influence the endurance characteristics. Several tests have been developed to measure muscle endurance.
A feature of these tests is that they all monitor the ability of a specific muscle, or group of muscles, to contract repetitively. Examples of these tests are the number of push-ups and abdominal curls in a minute.
These tests lack specificity and do not differentiate the proficiency level of rugby players.
Repeat sprints
The ability to resist fatigue after repeated short-duration, high-intensity sprints is a fitness characteristic which is important for team sports such as soccer, rugby, football, basketball and netball, to name a few.
Repeat sprint performance, and by implication fatigue resistance during intermittent, short-duration, high-intensity activities, can be improved by decreasing body mass, specifically body fat, and by increasing strength and muscular endurance, providing this does not result in an increase in body mass.
Training which results in improvements in agility and/or aerobic power may also improve the ability to resist fatigue during repeat sprint activities.
Motor co-ordination (skill)
Apart from the physical characteristics associated with success in rugby, performance also depends on skill, which is the combined interaction of agility, balance, co-ordination, power, speed and reaction time.
Another aspect of skill which is difficult to define or measure is the ability of a player to make a strategic decision very quickly and with accuracy. The accuracy of this decision-making contributes to the success of the team.
There are examples of players who seem gifted and on most occasions make the correct decision during matches, compared to their less “talented” team mates. Whilst motor coordination can be trained, the superior decision-making ability that some players have, and which make them appear more skilled, is probably an intrinsic characteristic rather than being a characteristic acquired by training.
Flexibility
Flexibility represents the range of motion specific to a joint. Flexibility can be dynamic or static.
Dynamic flexibility involves the range of motion during movement of muscles around a joint whereas static flexibility defines the degree to which a joint can be passively moved through its full range of motion.
Changes in flexibility occur after stretching exercises. Flexibility training is used in the warm-up before training or competition and also with the goal of preventing injuries.
Although there is theoretical evidence to support the positive link between stretching and lowered risk of musculoskeletal injuries during exercise, the clinical evidence is not so strong.
A sit-and-reach field test has also been developed to measure the range of motion of the lower back and hamstring muscles.
Cardiovascular fitness
Cardiovascular fitness, also referred to as cardiovascular endurance or aerobic fitness, refers to the collective ability of the cardiovascular system to adjust to the physiological stress of exercise.
Cardiovascular fitness is usually measured in the laboratory during a high-intensity exercise test to exhaustion with a mode of exercise which recruits a large muscle mass and with rhythmic muscle contractions (e.g. cycling, running, rowing).
A feature of the test it that it should have a progressively increasing intensity, which continues until the player is exhausted.
Oxygen consumption and carbon dioxide produced are measured continuously during the test. The oxygen consumption coinciding with exhaustion is called the maximum oxygen consumption (VO2max).
An athlete who excels in an endurance sport generally has a high VO2max. Although endurance training increases the VO2max, and by implication the cardiovascular fitness, the increases are generally moderate (about 15%) and are dependent on the level of fitness of the person at the start of the training programme.
A 20 m shuttle test has also been developed to predict cardiovascular fitness in a field setting.
In this field test, athletes run backwards and forwards between two beacons 20m apart, maintaining a prescribed pace that gets faster and faster until the athlete is unable to maintain the pace.
Body composition
Body composition is defined by the proportions of fat, muscle and bone. Fat occurs beneath the skin and around the internal organs and is also found within tissue such as bone and muscle.
Fat can be divided into non-essential and essential compartments. Fat tissue insulates and protects organs and is a storage form of energy and substrates for metabolism. Fat mass may vary from about 6 to 40% of body mass.
Endurance athletes who perform at a high level have low levels of fat. Sumo wrestlers are examples of elite athletes who have a high fat content. Many sports have weight categories (e.g. boxing, judo, wrestling), and therefore the manipulation of body mass, in particular fat mass, becomes an important part of these athletes’ preparation for competition.
The body fat of elite rugby players ranges from about 8 to 17%.
Forwards generally have a greater percentage of body fat than backline players, and it might also be said that as the proficiency level increases, the average percentage of body fat decreases.
Body fat does not contribute to the generation of muscle power, and therefore excessive amounts of body fat will detract from sprinting ability.
Muscle mass can vary from about 40% (anorexic person) to 65% of body mass (e.g. a bodybuilder with hypertrophied muscle).
The main function of muscle, from a sport and exercise perspective, is to contract and generate force.
Depending on the sport and the type of training, some muscle is adapted to contract several thousand times per training session without developing fatigue (e.g. endurance activity), whereas other muscle is adapted to generate high levels of power with only a few contractions (e.g. powerlifting, shot-put, weightlifting).
This type of muscle fatigues rapidly.
Bone is a specialised type of connective tissue which is also dynamic and responds to stimuli by changing its shape and density, albeit at a much slower rate than fat and muscle tissue. Bone mass varies from 10 – 20% of total body mass.
Summary
An important aspect of physical conditioning for rugby is the characteristic of “match fitness”. This is the specific fitness acquired from playing matches on a regular basis and becoming adapted to contact.
Whilst the physiological demands of matches can be simulated during practise, there are subtle aspects of playing a match that cannot be simulated in practise. These difficult-to-measure characteristics can only be developed from playing.
There are no data, other than the experience of coaches and players, which defines how much contact a player needs to have before he is “match fit”.
This is an important question, as it has important spin-offs on performance and also for the risk of injury.
There is a fine line between getting sufficient “game time” to develop “match fitness”, and playing too much with insufficient time for recovery and regeneration. Another consideration for developing “match fitness” is that the risk of injury is always high during a match compared to a practice.
This is an extract of Aspects of Physical Conditioning for Rugby as published on SA Rugby. For the full article click here.
Source Aspects of Physical Conditioning for Rugby by Mike I. Lambert; 1MRC/UCT Research Unit for Exercise Science and Sports Medicine, Department of Human Biology, Faculty of Health Sciences, University of Cape Town.
(Health24, August 2011)
