What is injury prevention and how?

Points to remember in injury prevention : 

An injury occurs when the stress applied to a tissue is greater than its capacity to absorb these different forces. This fundamental balance to prevent injury is based on complex interactions between internal and external risk factors (1)(2). All injury prevention programmes and principles must be based on optimising the balance between applied and absorbed stress, a balance which is sometimes fragile but which can be strengthened by rigorous and specific training. Different essential notions will be discussed here in order to try to give you some keys to apply during your sessions. The aim here is to provide some food for thought, based on scientific literature, about how to improve training. However, injury reduction rates are only significant when multi-component programmes are used, so it is essential to incorporate as much as possible of these concepts into your sessions if you want the work done by the athlete to be effective (3). These guidelines will be further developed and expanded upon in order to make you aware of the need to adopt them and to reduce the incidence of injury in each season.

Proprioception : 

What is proprioception ? 

Proprioception is a neural process by which the body receives information from the external environment and integrates it to produce an adapted motor response (4). In short, it is our conscious or unconscious ability to perceive the position of our body in order to regulate our movements and posture. The sense of position and joint movement are expressions of the conscious component, whereas postural control is mainly based on the unconscious component (5). It is responsible for the balancing abilities of each of us. This notion of proprioception plays a central role in joint stability and injury prevention since proprioceptive control can also be defined as the expression of the effectiveness of stabilisation reflexes in controlling vertical stability (6).

It is difficult to classify an exercise solely as proprioceptive strengthening as it often has other features in parallel. However, to be considered proprioceptive, it must involve instability that causes the individual to adapt their balance. Proprioceptive training programmes based on high frequency instability exercises have been shown to improve proprioceptive and postural control and have been effective in reducing the incidence of ankle sprains, knee sprains and low back pain. These results indicate that improved proprioceptive control may be a key factor in the effective reduction of lower limb injuries and low back pain (7). There are two main mechanisms that would explain the reduction in the rate of ankle and knee sprains.

The first principle is based on the improvement of proprioceptive control allowing better control of movements, adequate management of jumping and landing trajectories, thus minimising mechanical stress on the lower limbs. The repetitive reflex contraction of the stabilising muscles, the extrinsic and intrinsic muscles of the foot, during high frequency exercise increases their strength and endurance, shortening their mechanical latency. These effects make these reflexes more effective in countering various situations that can lead to ankle and knee sprains(7). The increased strength of the fibular muscles allows a less supine attitude of the feet during flight, improving their potential to protect against inversion (the most common injury mechanism). The importance of this aspect is underlined by the results of a recent review confirming that an anterior ankle sprain causes moderate to strong temporal deficits in the peroneal reflex (8). Thus, specific training can make proprioceptive reflexes more effective, and the body will react faster and better to imbalances.

On the other hand, proprioceptive training promotes resistance to stress and the resilience of joint soft tissues (the ability of tissues to remain in good trophic condition despite difficult stresses) such as ligaments, capsules and especially fascias. The latter seem to be better able to protect the joints in varying degrees of amplitude. This point is based on one of the most important capacities characterising our human body: adaptation. 

Proprioceptive training can raise the threshold of protection, allowing better absorption of potentially injurious forces. However, when this threshold is exceeded, the injury is the same in an untrained person, and recovery time is not reduced either (7). The adaptation of tissues for preventive purposes will thus be responsible for an improvement in stabilising capacities, but it does not play a role when the tissue is injured. Specifically, Hübsher et al (9) reported in their review that balance training was effective in reducing the risk of ankle sprain injuries by 36%. Other reviews have supported this figure by indicating that proprioceptive training was also effective in reducing ankle sprain recurrences (30-50%) (1). Beyond the effects on injury reduction, athletes also reported a perceived improvement in stability, technical skills and movement control during their sport (7).

How to work on proprioception effectively ?

 

To focus the work of a session on the development and reinforcement of proprioception, it is necessary to vary the situations of instability and imbalance as much as possible. Inducing different components of jumps, landings, stabilisations with external imbalances allows to work efficiently on these capacities. It is also possible to disturb the trunk and its balance capacities because abnormal patterns of the latter diminish the neuromuscular control and the optimal biomechanics of movements (10). In order to achieve a high level of protection and work intensity, it is possible to alter or suppress the visual signal during these exercises. This alteration of vision, and the cues that go with it, will allow better recruitment of information. 

All this neuromuscular and proprioceptive work should be carried out from the pre-season onwards but it is important to continue it regularly in order to maintain the benefits obtained. This regularity and early management have made it possible to better prevent knee injuries, particularly those involving cruciate ligament damage (11). It is also possible to reduce the risk of injury during matches by adding more consistent proprioceptive components during the warm-up (12). This addition seems simple but it is really important in order to better prepare neuromuscular control and balance capacities afterwards, increasing the speed of responses to imbalances. 

To summarise, it is extremely interesting for injury prevention to work on imbalance situations by closing the eyes or by disturbing the visual inputs in various ways. Disturbing and imposing constraints on the trunk or upper limbs during balance situations is also a factor that can easily be played on. In addition, starting proprioceptive work in the pre-season and continuing it throughout the entire season gives better results. Inducing some proprioceptive exercises before the match is also easy to do and equally effective. 

Tailoring muscle strengthening and the importance of eccentrics :

Another big part of injury prevention is the individualised and precise adaptation of muscle strengthening to the needs of each athlete. This strengthening aims to improve cushioning strength, maximal strength and reactive explosive strength. It is also important to adapt the physical training programmes to the velocity and profile of the players according to their position (explosiveness/endurance…), the physical preparation must be well individualised. It has been shown that there are direct relationships between the athlete’s basic physical condition and his or her risk of injury depending on the training loads provided. However, it has also been shown that appropriate training offers a protective effect against possible injuries (13)(14). In fact, if the body is properly prepared, intense chronic training loads effectively reduce this risk of injury (15)(16). Beware, however, of excessive and rapid increases in training loads which are responsible for a large proportion of non-contact soft tissue injuries. It is also necessary to keep an eye on possible overtraining, which can be devastating for an athlete during the season, a concept developed in the recovery section of this site. (overtraining) 

What factors should be considered during the session to effectively reduce the risk of injury ? 

In addition to the personalised adaptation of the load, it is essential to carry out regular quality eccentric strengthening. This work must be carried out in particular on the hamstrings, the preferential sites of muscular damage in footballers. To briefly explain the notion of eccentricity, it is a contraction where the muscle fibres lengthen, despite the resistance to this movement and this contraction comes into play mainly during receptions or braking. To illustrate, if a movement is produced by the agonists with a large force, then it stands to reason that the force exerted by the antagonists should be strong enough to control the variations in muscle elongation. It is this good control which also makes it possible to prevent and reduce the risk of muscular injuries during violent efforts. In fact, eccentric strengthening makes it possible to work on the alignment of the muscle fibres. This optimal alignment makes it possible to have a healthy muscle, ready to face different constraints without additional risk of injury. 

During the sessions, it is also essential to take into consideration the age of the players in the group, as this data directly influences the adaptations linked to the training. Indeed, Gabett et al. found that when they applied the same 14-week conditioning programme to junior players (about 17 years old) and senior players (about 25 years old), the effects and improvements differed between the two groups. Thus, while the training improved muscle strength and maximal aerobic power in the junior and senior players, the improvements were greater in the junior players. In contrast, injury rates were higher in the senior players. Thus, junior and senior players may adapt differently to the same training load, suggesting that training programmes should be adapted to account for age differences if the risk of injury is to be reduced (17)(18).

Exposing players to too low a training load can also increase the risk of re-injury. Therefore, it is important to find the right balance between too much and too little, as it is between these limits that the best benefits of physiological adaptations to muscle strengthening will be achieved. In this need, the role of the physical trainers takes all its sense because a precise knowledge of each physical training modality will allow a better adaptation to the player and his profile. Unfortunately, after an injury and once players enter the rehabilitation or reathletisation phase, it is difficult for practitioners to expose them to appropriate loads representing their basic level. These loads would allow them to improve their physical qualities, having the protective effect against injury, but it is difficult to regain continuity and regularity of performance after a period of varying degrees of unavailability. This regular physical work during the season would avoid the « peak » of loads when players return to full training. However, if the player comes out of a period of immobility or a phase with much less intensive training than he is used to, it may become difficult to recover this physical level without injury. It is not uncommon in teams for a player to be constantly injured and to break down repeatedly with different injuries. All of these injuries are due to the fact that his training load is not high enough each time to cope with the demands of high level matches or training, even though the processes and timeframes for management have been followed (13). This type of player exposes physiotherapists, physical trainers and doctors to considerable difficulties in managing them and it is therefore always necessary to take the time and, if necessary, slightly increase the time taken to return to the field, despite the sporting and economic importance of the player. Surrounding oneself with a competent medical and sports staff is thus one of the most important criteria for getting the maximum benefit from one’s potential during one’s career. 

Working in a fatigue situation :

Fatigue is defined as the transient inability to maintain power or force during a repeated muscle contraction (19). Fatigue work is a less popular but not less effective concept. Studies show that most joint or muscle injuries occur in the vast majority of cases at the end of the second half or in the last 15 minutes of a player’s game. These data show that fatigue is a considerable risk factor in sports, as it can contribute to the alteration of neuromuscular control of the lower limb and the subsequent alteration of an individual’s ability to dynamically stabilise their joints (20). Indeed, exercise and fatigue have been shown to increase knee ligament laxity, thereby decreasing joint control (21)(22). Other studies have also shown a delay in voluntary muscle reaction time, a decrease in quadriceps and hamstring excitation rates, and a delay in spinal reflexes during fatigue (23).

Physiologically, how does fatigue play a role in this ?

It is important to know that the central nervous system receives and integrates information from various types of stimuli in order to achieve movement or correct joint position. All visual, auditory, vestibular, skin, joint and muscle information influences 3 distinct structures responsible for motor control: the spine, the brain stem and the higher centres (cerebellum, basal gland and motor cortex) (24)(25)(26)(27). Fatigue, through the organic disturbances it induces, modifies the afferent input of muscle receptors. Indeed, Lagier-Tessonier et al confirmed this by demonstrating that the responses of the muscle spindle and Golgi tendon organs were reduced under conditions of muscle acidosis, ischaemia and hypoxia in the tibialis anterior muscle (28). This depletion alters active stability as it has direct effects on the muscles but it is also interesting to note that it decreases the accuracy of messages sent to the cerebral cortex.

How and why do we work when we are tired ?

As explained above, fatigue reduces muscle activation but also the activation of their sensory receptors. It is therefore advisable to work on the resistance of these receptors in order to prepare them, always progressively, to react even in the event of exhaustion. To do this, training sessions with a heavy physical load could be finished with a quick proprioceptive part, well supervised. The aim is to get as close as possible to the conditions found in matches by running, jumping and contact with the ball. Working on proprioception after an eccentric strengthening session, where the contracting muscle is forcibly lengthened, could also be beneficial. This type of exercise causes muscle damage that can spread to the muscle’s proprioceptors, the neuromuscular spindles, and lead to a disturbance in the perception of limb position (29). Working under these conditions would increase our body’s capacity to adapt in a situation of exhaustion.

Mobility and joint maintenance :

It is known and recognised that good flexibility, less stiffness and better ranges of motion are beneficial factors in injury prevention. In conjunction with the ability of muscles to stretch in the face of violent contractions, these concepts also play a role in the prevention of overuse injuries (30). This mobility is closely linked to stretching and the relaxation of structures (joint capsules, tendons, ligaments, fascias, etc.). Good mobility, especially in the hips, would allow a more optimal recruitment of muscle fibres and improve the quality of movement of each player. This quality of movement is essential if the athlete wants to keep a healthy body, ready to face a more varied number of physical constraints. 

In order to work on this mobility, it is advisable to set up regular routines since improvements in joint amplitude do not appear overnight. It is a long term work, that some tend to neglect saying that they do not see any direct consequences but it is essential to keep these good amplitudes if the sportsman wants to resist on the duration to the requirements of high level. Numerous ideas for video exercises will flourish on the site and on the pages of the social networks, so don’t hesitate to try them out or insert them into your mobility routines. 

Fascias: directly linked to mobility !

These tissues are to be linked to the mobility part, indeed they play a particular role in the good flexibility and health of our body. They are characterised as a multidimensional network allowing the integrity and the good functioning of all the structures of the human body between them. Indeed, forces are not only transmitted through muscles and tendons, but numerous experiments have shown that intermuscular and extramuscular fascial tissues also constitute a pathway for transmitting the force necessary for movement (31). If the fascial system is injured or stiff, significant loss of performance may occur directly, but it may also have a potential role in the development and perpetuation of musculoskeletal disorders (32). These lesions can also lead to fascia-induced neuronal disruptions that can propagate to the muscles. The latter could be led to modify their physiology and transmit completely dysregulated painful messages. 

How to improve the health of your fascial tissue ? 

To try to briefly summarise its physiological functioning, it is necessary to know that the good cellular balance of the fascias is influenced by the quantity of water present around its fibres. This quantity of water that this tissue can absorb is directly influenced by the physical constraints it is confronted with. Other factors come into play, such as hydration, of course, but also age, history of injury, and gender, thanks to the presence of oestrogen in women. This hormone has a stimulating effect on the synthesis of collagen, which is the main component of fascial fibres (33). It is also important to know that in this type of tissue, acute and chronic loading stimulates collagen remodelling (34), whereas simple excessive loading or direct trauma initiates micro and macro changes necessary for the repair of this tissue. These changes can, however, lead to pathological changes in the function and mechanics of healthy tissues if they are not controlled or supervised (32). The best way to prevent these changes is to impose progressive stresses so that physiological adaptations have time to take place. This is the reason why this notion of progressiveness comes up very regularly on this site, since the fascias will be concerned in any type of injury or physical activity. A training of these tissues makes it possible to have a strong body at all levels and even in depth, allowing thereafter to better resist the loads of the trainings or the matches. 

Stretching : 

Stretching is one of the biggest debates in the world of sport and has been for years. There is currently no real consensus on their optimal use, but there have been many studies on the subject. Perhaps the most pervasive notion is that tense muscles are more likely to be strained (35)(36).

Overall, it is possible to characterise 2 types of stretching, static and dynamic.

• For the dynamic part, they are to be recommended during the warm-up. Indeed, there can be a great similarity between the patterns of dynamic stretching movements and exercise (37). Secondly, dynamics can raise core temperature (38), which can increase nerve conduction velocity, muscle compliance and the enzyme cycle, thereby accelerating energy production (39). There was some evidence of a specific effect of these stretches on movement pattern, as jumping performance improved slightly (about 2.1%) (40). Overall, the current research indicates that pre-activity stretching may be beneficial for injury prevention in sports with a sprinting or repetitive motion component. Taken together, these studies indicate a reduction of up to 54% in the risk of acute muscle injury associated with stretching (40). It is therefore advisable to carry out activo-dynamic stretching during the warm-up, i.e. stretching the muscle (maximum 10 seconds) and then activating it via a dynamic movement generating specific contractions. To qualify this, it has been shown that a longer stretching time ( ≥60 s) before a match was likely to cause performance alterations such as reduced muscle activation or decreased performance (41). 

• Static stretching consists of extending the muscle until it feels stretched and then holding it for a given time. A growing number of studies have reported negative effects of static stretching on maximal muscle performance and therefore it seems more interesting to perform it outside of physical activity during mobility and stretching sessions (40). Many athletes believe that it is important to stretch for a long time directly after physical activity in order to recover, but beware of this misconception. Stretching directly after a match or training session does not bring any benefit because the warmed up muscle is initially more supple, the effects of stretching will be only less or even negative. It is therefore recommended to stretch at least 3 hours after a physical activity in order to obtain benefits on flexibility and injury prevention since there is always a presumed relationship between muscle tension and the risk of a muscle strain injury. The clinical hypothesis is that a more flexible muscle can be stretched further and is therefore less likely to suffer a muscle strain injury as its fibres are less affected by stress by absorbing energy better (42). This reduction in tendon stiffness may reduce the load placed on the muscle-tendon unit during movement and this is why less flexibility in the quadriceps and hamstring muscles may contribute to the development of patellar tendinopathy in some athletes.

Sports involving explosive skills, with many maximal changes of direction, require a muscle-tendon unit that is flexible enough to store and release the large amount of elastic energy. Recently, it has been shown that stretching is able to increase the flexibility of human tendons and, consequently, increase the tendon’s ability to absorb energy. Therefore, in these sports, we suggest that stretching is important as a prophylactic measure for injury prevention. The authors concluded that a rigid muscle-tendon unit was a risk factor for the development of certain tendinopathies (43).

However, there are other arguments that counteract these views by explaining that some athletes may have tendons that are less suited to their physical activity if they are too flexible, and therefore less efficient during movement. In some sporting activities, having rigid tendons would be advantageous for the execution of brisk and rapid movements, allowing for rapid changes in tension and therefore quicker responses to joint movements, perhaps providing more sensitive feedback to the central nervous system regarding muscle length and tension (44)(45)(46). 

Thus, it seems important to remember that dynamic stretching must be incorporated into a warm-up protocol while respecting its application modalities. Static stretching, on the other hand, should be used at a distance from physical activity (at least three hours afterwards) if the athlete intends to benefit from it. There are conflicting opinions about the benefits of stretching and improving flexibility, but it is necessary to avoid maintaining muscle or tendon stiffness. There is also evidence that a more flexible person will tend to recover better after significant effort (see section on recovery). 

The warm-up : 

The very purpose of the warm-up is to prepare the body for the stresses encountered in a match in order to limit the risk of injury during the activity. Indeed, it has been shown that warming up has a positive effect on reducing muscle injuries and that warm muscle (40°C) absorbs less energy than cold muscle (25°C) before rupture (30)(47). A warm and more flexible muscle will thus be less likely to suffer injuries related to violent stresses of activity. Warming up also provides a protective mechanism for the muscle by giving it a greater length of stretch and greater resistance to stresses that may induce tears (48). In addition, it has been shown that warming up increases the speed and strength of muscle contractions while accelerating the speed of nerve transmission, providing better reactivity and adaptations to falls or injurious movements (30). All these characteristics illustrate the role that warming up has in the practice of a sporting activity but even more so in the prevention of injury. 

In order to optimise warm-up programmes it is important to take into account all the principles of injury prevention outlined in this article. It is therefore recommended to adapt the stress progressively by starting, for example, with a little mobility work, followed by activo-dynamic stretching. Subsequently, proprioceptive work can be incorporated into the preparation of the body for the match by including jumping exercises and landing exercises with and without imbalances. In parallel with the cardiovascular warm-up, some eccentric contractions can be incorporated such as a few repetitions of the famous Nordic Hamstring. Then, at the end of the warm-up, it is recommended to perform rapid accelerations or changes of direction. Reflex work can also be included at the end of the warm-up in order to prepare the brain for the efforts it will encounter during the match. 

Otherwise, several standardised programmes are available, such as FIFA 11+, which is divided into three parts and consists of 15 exercises. These should be performed at the beginning of each training session in the given order. It is essential that the exercises are performed with perfect technique. Particular attention must be paid to the correct execution of these exercises to increase their effectiveness (mastery of movements, good alignment of the lower limb, jumping repetitions, etc.).

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• 1st part (8 minutes): 6 slow running exercises combined with stretching and controlled contact with a partner.
• Part 2 (10 minutes): 6 exercises focusing on upper body and leg strength, balance, plyometrics and agility, each with 3 levels of difficulty
• Part 3 (2 minutes): 3 more rhythmic running exercises, combined with starting and restarting.

References :