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Applied plyometrics for inline speedskating

Explosive strength gains for skaters

by Professor Rosario Bellia (Italy)

PART I
=====

Introduction
This text was born in order to provide some methodological indications about the plyometric system, considering the importance given to such method, which was shaped and developed in Italy. My work is based mainly in observations taken on skaters from Italy and other countries, aside from my personal experience of 15 years as an athlete coached by a great knowledgeable expert such as Prof. Bartolo Nizza, in a splendid city called Siracusa during the period in which professors Vittori and Bosco where carrying out their experiments. Finally, I made a bibliographical research resting on the recent applications being made in USA and Eastern Europe countries.
Regarding inline speedskating, this method is largely used in countries like USA, Korea, Colombia, France, Spain, etc. Talking to Italian coaches and athletes I was able to confirm that plyometrics are widely used in my country too, but only a handful of them do so for the entire season, programming a surge during the competitive phase.
So the aim of this study is to supply advice by means of considering plyometrics a safe and efficient method for the whole training year of this wonderful sport.

Elemental principles of neurophysiology, introduction to the method
In 1960, prof. Margaria said that “a concentric contraction preceded by an eccentric one can generate a greater strength that the concentric strength”. In 1982 prof. Carmelo Bosco, after many years of study and research, establishes that pre-stretching allows for an accumulation of elastic energy into the muscle, capable of improving performance in the positive muscular workload. This research, along with prof. Verkhoshansky studies in Russia, were cardinal in the development of the plyometric training method.
In short, Bosco demonstrated that pre-stretching forces a greater activation of the central nervous system, useful to optimize the training process. This was confirmed by Dr. Kuortane, from the Biomechanics Laboratory of Jyvaskyla University (Finland), and by prof. C. Pittera, internationally recognized expert in volleyball.
Weineck (1998) affirms that the plyometric method is the best one to work out instantaneous strength, that allows boosting in speed and general strength without mass increase. Bellotti and Matteucci demonstrated in 1999 that the best results are achieved if muscular elastic rebound (actomyosin bridge) can be effectively mixed with active muscular contraction, considering the infinite options of modulation (from maximum extension to zero elastic effect).

Regarding inline speedskating, a sprinter’s start or the sudden change of pace an endurance athlete does in a marathon can be arbitrarily defined by the same term: POWER, meaning the relation between strength and speed. In other words, power in this case is the maximum strength that can be generated in the shortest time lapse. So, if we consider power = strength x speed, we immediately see that we can’t work out one of the factors more than the other, as in doing that we are going to limit power increase.

Strength gains without improving speed will only give limited or partial results. Therefore, if lack of maximum strength spells for a limited expression of the motion skills chain, an excess of it might be useless if not even harmful. In fact, prof. Vittori maintains that an elite sprinter needs to push for a squat a total strength equal to twice their body weight. Analyzing specifically the motion of the leg in a sprint, it’s clear that this kinetic chain works adequately if all muscles involved in the extension phase are correctly fortified. As a matter of fact, having really strong hamstrings but weak foot extensor muscles (or the other way around) does guarantee non-optimal sprint ability (explosive-elastic reflective strength).
Plyometric training is not state-of the-art, actually it’s been used for many years by other sports’ athletes. After Bosco’s research, in which the elastic properties of muscles where revealed, many have tried to apply the concept to this training method. But quite a few incorrectly applied theories leaded to injuries and overtraining. So prevention is in order.
Plyometrics are a specific training method to improve explosive-elastic strength, which should be used along with other matching methods to increase the relationship between maximum strength and explosive-elastic strength. Especially in our sport, in which often a skater needs to express maximum strength in movements elapsed between 0.5 and 0.7 seconds.
During muscular extension the elastic energy accumulates and will subsequently be used in the contraction phase: the key to the efficient muscular cycle stays in a shorter inversion movement time between extension and contraction. That brings the fundamental principle of plyometric training: speed, instead of extension length, is what really determines the employ of the elastic energy.
To fully understand the advantages this technique offers it would be useful to firstly explain a few aspects of neuromuscular physiology. A single motion neuron connects only one type of muscular fibre (red, white, intermediate), and are activated based on the muscular recruitment percentage principle. Whenever strength is low (about 30% of maximum) the smaller motion units are recruited, namely red fibres, which have a lower activation margin. With increasing workloads from 30% to 70%, both small and intermediate fibres are activated. Over 80% of strength, the high-excitability white fibres will enter in action. However, during fast or very fast movements, it appears white fibres are recruited directly.

Renshaw cells: optimal fibres synchronization is the purpose to attain maximum muscular efficiency. This is Renshaw cells function, to modulate the different fibres’ contractions in order to achieve best possible functional synchronization.

Muscular contractions are closely controlled by specific muscular sensors called receptors that oversee in every movement the stretch of fibres, avoiding structural damages. Let’s have an outlook:
Neuromuscular spindles: receptors placed along a parallel line with muscular fibres, which detect elongation variations. If the length variation at any point reaches a certain limit, the “stretching (myotatic) reflex” acts immediately. That is, the spindle reacts sending a signal to the central nervous system that in turn orders the agonist muscle to contract. This action is supported by the simultaneous inhibition of the antagonist muscle.

Golgi’s Organs: these are distributed in a series along the muscular fibres, following the junction between tendon and muscle. Their activation threshold is higher than neuromuscular spindles, keeping the central nervous system informed about the force variations developed at the tendon heads. If tension is too high chances for a fibre breakdown increase, so Golgi’s organs send a signal towards the central nervous system, which quickly induces a contraction inhibition.

Considering the physiological aspects then, plyometrics use is instinctively preferred by the central nervous system because:
● Allows for a deep and complete neuromuscular stimulation, as a result hastily increasing strength and speed in muscles.
● Decreases Golgi’s organs sensibility, which will not stop maximum (or sub-maximum) contraction (myotatic reflex inhibition)
● Brings greater elastic energy storage, faster contraction and improves neuromuscular spindles’ efficiency
● Reinforces tendons, aponeuroses (see here >>) and muscle’s internal connective.
● Improves instramuscular coordinations between fibres in a single muscle (higher quantity of motion units sincronized). As a result, there is better and faster strength gain.
● Elevates Renshaw cells’ inhibition threshold, so activation at higher frequency is possible. That allows a selective recruitment of white fibres, due to the massive intervention of sincronized motion units.

Now let’s analyze the details of plyometric drills characteristics. Plyometric work has three fundamental timings:
1) eccentric phase (stretching);
2) isometric phase (movement inversion);
3) concentric phase (shortening).
Two factors define the stretching-shortening cycle:
- elastic return action from the elastic component series (of which 72% comes from the tendon and 28% from the S2 myosinic head portion - Bisciotti, 2000);
- stretching reflex (Bosco,1985 -1997).

In order to get the best results, three compulsory conditions should be considered:
● The stretching that precedes concentric contraction should be active and directly proportional to the extension speed (Bosco 1997);
● Stretching should be sufficiently ample, to get the stretching reflex exactly at the right time: neither ahead of the eccentric phase, nor during the concentric phase.
● Coupling time should be shorter than that the half-life of an acto-myosinic bridge (about 120 – 150 milliseconds). Best effects are achieved if elastic return is blended with active muscular contraction.

WARNING - Plyometric methods should be avoided in the following cases:
1) Osgood-Schlatter disease, Larsen & Johansson disease, related pathologies;
2) Recent fractures in legs;
3) Severe spinal pathologies;
4) Perters’ disease after-effects;
5) Abnormal Q angles (remarkable knees’ valgism/varism);
6) Capsule-articular and tendineous apparatus pathologies;
7) Sever disease, or calcaneus apofisis and plantar fascitis;
8) Tendinopathies in calf/ Achilles tendon;
9) Any other pathology that could be harmful to the athlete while exercising plyometrics.

PART II

======
Plyometric training is largely based in the following principles:
Positive action: whenever muscle contracts to generate kinetic energy (body acceleration) is doing a positive action (concentric contraction)
Negative action: whenever a muscle in tension, instead of shortening is being extended by a moving mass, and the force being exerted is acting towards the opposing direction of said mass (i.e. for the skater’s basic position), a negative action is being done (eccentric contraction).

While positive action is carried, the contraction’s resulting energy becomes mechanic work and heat. While negative action is being done, the resulting energy becomes heat and elastic energy, which could be swiftly used to accomplish a consequential positive action.
Just as in a bouncing ball, (which elevation/advancement motions are direct consequences of the elastic energy accumulated by its deformation the very moment it bounces from the floor), the energy collected into the elastic component in muscles and in the tendons’ elastic elements will be used during the posterior push forward or up.
During the phase in which muscle is doing a negative action, a certain amount of potential elastic energy is charged, which, after the tension/extension flow, can be transformed in kinetic energy. In physiological terms, the distinction between negative and positive action is extremely important, in view of the force that a muscle can apply is different if it is being shortened by contraction or stretched by a negative workload.
We can find the following aspects in negative muscular action:
If muscular distension speed is relatively low, thermal energy is produced
If muscular distension speed is relatively high, an elastic energy accumulation is obtained, that can be re-used whenever the muscle, after being stretched, is shortened by the following contraction.
Muscle’s tension grows in proportion to the speed in which is being stretched
Using again the ball’s analogy, if a ball is dropped to the floor, the altitude it will reach in its bounce will depend on its elasticity and on the speed in which hits the surface (its kinetic energy). It means that in order to achieve an optimal “bounce” we need a strong kinetic force plus an ideal elastic matter. Now, back to muscles, kinetic energy depends on the falling altitude (vertical/horizontal speed), elasticity depends on the muscle properties (actomyosinic bridges).
The problem is to find the correct relationship between the need of a greater strength and the improvement of elastic properties of the muscles, since it has been demonstrated that systematic repetitions of drills at maximum level (particularly isometric) reduces the elastic attributes of muscles. The answer lies in the specific function that is being trained: sprinters or endurance skaters. In particular, for sprinters mass augmentation in relation to the absolute strength is a crucial condition to achieve satisfactory performances; hence it is best to operate in sectors and separate timings: first absolute strength is to be increased, and then elasticity in muscular groups must be worked out, since that’s what is going to give the explosive quality to the technically refined movement. But in general, speedskaters should develop strength and muscular elasticity as a whole.
Moreover, it is better to choose specific drills: joints angles, quantity and timing of workload (negative action) plus elastic bouncing phase (positive action) should be as similar as possible to the motion that is being carried out during racing. Additionally, the typical plyometric drills should be done in concert with exercises that imitate the mechanical actions of racing.

Correct plyometric training
In order to get optimal and simultaneous enhancement in strength and elasticity, a skater needs to:
• perform specific drills that imitate the fundamental part of the action that is being trained
• immediately after the drills, relax the affected area & avoid for it to be subjected to gravity (laying on the floor or sitting with relaxed legs over a higher surface)
• execute 5-7 successive reps, with a 10-15 minutes recovery between series in which to eliminate any residual tension on muscles. The number of series will be determined by the athlete’s ability to sustain elevated reaction capacity (meaning positive action) during the elastic energy exertion (accumulated while on negative action).
• keep decontracted muscles before execution, taking care in doing a maximum contraction just before the rebound/jump, for an effective absorption of kinetic energy. In fact, the typical lower extremities drills are mainly jumps from an optimal height followed by a spring in vertical elevation.
Conditions for an elastic action in a drill are the following:
• fall, with relaxed muscles in the calf area
• blocking of calf/ankle, knee and hips joints during highest intensity of elastic bounce phase
• sudden bounce and attaining of maximum height after jump.

Optimal falling height is that in which the maximum height is reached after subsequent jumping. Such height must be determined by a hit&miss method, being augmented by 10 cm until the highest vertical jump can be measured. Obviously, the stronger the skater, the higher will be the optimum height, as elevated force indexes require more energy to extend the implicated muscular mass: trained high-jumpers fall from 80-100 cm with a successive bounce of equal entity.
There are 2 ways of executing the fall:
1) keeping extended legs (without muscular stiffening), with minimal angular variations (about 170° at knee while amortization/inversion phase) and short contact time. See video >>
2) starting and finishing positions to surface done with a knee angle of about 90º; reducing tension on knee/ankle joints there is anway a good neuromuscular stimulus of extensor leg muscles (C. Bosco & C.Pittera). See video >>

This training method should NOT be used by itself, but inserted in a specific program aimed to improve explosive elastic strength.

Common mistakes in plyometric training
If during execution the height (or length) reached is not maximal, or increased in any case, the reasons most probably are:
• scarce executive coordination;
• insufficient charge of elastic potential, due to an inadequate falling height;
• excessive stretching due to a too elevated falling height (therefore over the subject’s real strength capacity). In this case, tension diminishes probably for the partial inhibition influence of Golgi’s corpuscles that protects the muscles from excessive stretch load.

During plyometrics, Central Nervous System is hugely triggered
CNS progressively operates to inhibit the elastic reaction capacity of muscles, whereas the work out involves an effort not proportional to the effective reaction potential.
In an annual training cycle, plyometrics should be employed from the second half of the preparatory period. During racing phase, plyometrics are useful to maintain special training conditioning: as a thumb of rule, a session should be completed every 10-15 days taking the following precautionary measures:
• optimal falling height should be found gradually, starting from a minimal height
• initially, jumps should be made in forward-up direction, after proper training jumps can be fully vertical
• plyometrics should always be performed after appropriate warming-up, to avoid damages to muscles, tendons and joints
• not recommended for athletes in evolutive/growth phase, and in general to anybody who hasn’t yet reached a satisfactory maximum level strength.
• to neophytes unable to master the exact technical characteristics of the correct movement inherent to our sport, specific plyometrics are counter-productive and even dangerous.

Any exertion of explosive force depends exclusively on our capacity to maintain elevated reaction rates after the elastic bounce (negative action) and to optimal CNS triggering, so any evident tiredness should be avoided, otherwise the execution will inevitably be slowed up thus the drill will be invalidated.
It’s a good idea to find an exercise that can be used as an assessment method to check the training progress, periodically performed to measure the athletes’ form and the program effectiveness.

Other means to improve speed strength

Dynamic loads method
To increase explosive strength, the moving phase requires a static starting position with a chosen joints’ angle. See video >>
To increase explosive elastic strength, the moving phase employs the elastic reaction of muscles in a plyometric action. See video >>

Shock method
Created by Y. Verchosanskij, it differs to the plyometric method by some variations in the workload parameters and for the dissimilar ways of jumps from below, in which the lower joints flexion occurs only after touching the floor with heels. Falling height varies depending on which kind of strength we want to develop
1) quick strength : 75 cm
2) reaction capability: 55 cm.
3) maximum strength: 110 cm.
The author maintains that a notably and sudden muscle stretch is the result of an “emergency recruitment” of motion resources hidden in the neuromuscular system. This method is extremely useful in developing explosive strength, but only for elite athletes; it should be entirely avoided with young athletes as the muscle-tendon structures are heavily stimulated. In addition, arms elevation should be applied to equalize the spinal cord engagement. See video >>

Stimulation method
Another one fashioned by Y. Verchosanskij, that aims to develop quick strength and muscular reaction potential. See below Verchosanskij’s table:

The key principle in this method is that every stimulus that boosts muscular activity’s intensity leaves a “trace” within the nervous system that can encompass a notable influence in the effectiveness of muscular effort. As per Verchosanskij’s table, there are two related sequences of drills. The first one employs heavy weight and a limited number of reps over a flowing rhythm. The second one focuses on an explosive engagement with a low resistance, for a higher number of reps. This method is effectual only if subject is not exhausted. During recovery between series, is advisable to perform joint mobility drills together with relaxing/stretching exercises.

PART III

======

Some exercises to improve explosive & explosive/elastic strength
Practically speaking, a few authors did indicate certain directives to be followed in order to get the best possible results from plyometric work. Regarding the reps in each series, authors mostly agree that for beginners the minimal quantity is 5-8 and for advanced athletes a maximum of 10-12 reps (Verchoshansky, 1997 - Cometti-Weineck, 1998-2001). Those authors also concur about series output, which should be 2-3 for beginners to 6-8 for advanced athletes.
As for the recovery times, while all authors agree on total recovery between series (since these drills cannot be done in a fatigue condition), they provide different figures:
- 1,5-2 minutes Verchoshansky, Weineck;
- 2-5 minutes Bellotti & Matteucci;
- 7 minutes Cometti;
- 10 minutes Wisloff, Salveson & Sigmundstain
Finally, most experts believe it is better to allow for a 10 to 21 days recovery period between the last plyometrics session and the race event. As opposed, Bosco (1997) argues that the last plyometric session could be even 4 days before race, but in this case he mentions high-level athletes, that are used to this kind of work out and their bodies absorb at a better rate such stimulus.

General strength drills
1) Calf extension from standing position on either both legs or one at a time – Video >>
2) One legged flexion - Video >>
3) Getting up the bench - Video >>
4) Sagital plane abs: Video >>
a - flexing legs and hips
b - flexing upper body
b - simultaneous flexing (Gilles Cometti) - Video >>
5) Transversal plane abs: pelvic torsion - Video >>
6) Frontal plane abs: pelvis flexion - Video >>
7) One legged stand up - Video >>

Explosive & explosive/elastic strength drills
In these exercises, maximum vertical propulsion must be attained - Quantitative parameters are to be adapted to the skater’s weekly training and general fitness level.
1) Calf extension from standing position, one leg at a time, with elastic bounce - Video >>
2) Slalom run
3) All kind of jumps: both feet toghether, one foot, lateral w/leg crossing, with obstacles, etc) - Video >>
4) Frontal and/or lateral flexion, quickly returning to standing position - Video >>
5) Jump followed by bounce - Video >>
6) Sprints 30 – 50 – 70 m, 3 – 4 series with a 8 to 10 minutes recovery. Ballast can be applied (10-15% body weight)
7) Bench jumps, various types, with feet together or one at a time.
8) Obstacle leaps, touching the ground for the shortest possible time. Distance/height of obstacles, according to the skater’s abilities.
9) Half Dynamic Squat: knees down to 90º, keep position 2 seconds, 60-70% max.weight, 6 reps x 3 series - Video 1 >>, Video 2 >>
10) Jump Squat: from half squat (slowly reaching 90º angle at knee), ballast 20-30% of body weight. Do a jump at max. speed and full extension, 3 series of 8 reps.
11) Up the bench: one leg at a time, bench at about 50-60 cm, alternate starting leg. - Video >>
12) High knee jumps - Video >>
13) Bench sides - Video >>
14) Open and close with light ballast - Video >>
15) Step bench, with ballast and hyper-extension of supporting leg - Video >>
16) “Varju” Bench - Video >>
17) Sitting Bench - Video >>
18) Rope jumps (any kind)
19) Lateral jumps skating imitation – Variations: arm swing, arms on back, static or forward movement - Video >>
20) Double bench (keep flexing for 5 seconds) - Video >>
21) Lateral step-jump, with or without ballast - Video >>
22) Alternate lateral jumps
23) Cone/obstacles Skipping
24) Stairs: every possible variation- Video >> , Video >> ,Video >> ,Video >> ,
25) High Jump, then short bounce, followed by 15 mts sprint
26) Bench high jump - Video >>
27) Head jump tester (Gilles Cometti) - Video >>
28) Sprints starting from seated position

In general, all these drills can be done with ballast in order to get a better effect. Ballast is related to the skater’s own weight, but authors do not agree on its entity. For instance, Kusnetzov’s research demonstrated that in order to maintain a correct execution technique, overload should not be more than 7% of athlete’s body weight.
As of means of increasing ballast during drills, athletes can use heavy bodysuits (similar to those wear by motorcyclists), weight jackets and belts, etc. Bear in mind that calf/ankle ballast can produce injuries!

It is worth to note on a separated paragraph prof. Carmelo Bosco’s works related to sprints. There are several types, for instance: 10 to 30 mts, with sudden deceleration while at maximum speed, uphills, dragging ballast. Another interesting drill is 50 mts sprints with quick deceleration followed by a trajectory inversion (3-4 reps by 2-3 series at 90-95%, 8 min. recovery).

Another use of plyometrics can be related to pre-post skating workout
Specific Post- fatigue principle: Immediately after skating a distance that doesn’t pose a problem, the skater does a series of plyometrics. Thins kind of workout improves strength resistance.
Specific Pre- fatigue principle: First a plyometric series is done (for about ¾ of the skated distance duration), then the specific distance is skated.

Considerations & Safety

Considerations
● Workload : Adequate workload must be the first consideration. There are tables and indicators that help monitor plyometric stress in relation to muscular requests, but common sense and experience are the best instruments to decide quantity and quality of training stimulus.
● Athlete’s weight: the heavier the skater, the higher is their training request. In fact, static jumping for a 50kg athlete is a low request, but for a 85 kg athlete the same drill means a rather elevated request.
● Limbs: jumps on one leg are obviously much more stressing that jumps on both legs.
Ballast: the use of ballast increases intensity and slows down execution, even converts to concentric certain movements that are eccentric without extra weight.
● Density: a parameter that refers to the number of plyometric trainings in a certain period. As a rule of thumb, no more than 3 weekly sessions are ideal.
● Age and fitness: the younger the athlete, the less intensity. Also beginners should start with uncomplicated and low-requesting drills
● Strength base: before starting a demanding plyometric training program, it’s better to have a good strength base. As a guideline, some drills can indicate strength level, like squats (twice the body weight) or press (two and a half times body weight). Young athletes don’t need high strength levels just because their body weight is definitely lower.
Before starting, improve stabilization muscles (their strength can be evaluated through simple tests). Also eccentric strength might be a limiting factor in complex and intense plyometric trainings. The lack of adequate eccentric strength, spells for an impossible quick reversion from eccentric to concentric movement. This type of strength can be tested with certain methods, for instance the Stabilization jump test table (Klatt, 1988), that among others has the following tests:
1) Frontal lengthiest possible jump, maintain landing position for 10 seconds – check jumped distance, both legs – check if athlete’s using all 3 joints (calf/knee/hip) while landing
2) Repeatedly jumping the longer/faster possible during 30 seconds, checking if athlete inverts quickly from eccentric to concentric movement – count number of jumps
● Ability: proper execution contributes to avoid joint stress. For beginners it is necessary to establish a basic technique to prevent traumas. Falling shock is not only absorbed by foot, but by the whole skeletal system, that helps muscles absorb stress. Landing has to be on the entire foot, not on heels or toes, so the impact is transmitted through the calf and knees. Noisy landings are a sign of incorrect falling technique. What’s more, to avoid injuries in lower back, a reinforcement of dorsal & abdominal musculature is needed.

Advised progression
A gradual progression is suggested, following logical steps:
- For beginners rope jumping and small bounces should reinforce basic movement patterns.
- Take off on both legs is to be preferred to one leg variations.
- Movements’ amplitude should increase as long as experience and ability grows.
Correct progression is based on the following components:
1. Landing: proper landing on foot is cardinal, using calf/knee/hip to absorb impact with a correct posture.
2. Stabilizing jumps: to refine a good landing and increase eccentric strength levels in stabilizing muscles. I.e., athlete should be able to maintain for 5 seconds the landing position after 3 jumps per leg.
3. Jumps over bench: to learn a good take-off and the right arm swing, a bench can be used. Its height should reach halfway the athlete’s hamstring, at the most.
4. Reactive jumps on site: to improve reaction and to thrust vertically the body’s centre of gravity, little hops over the same sport using calves can greatly help. Athletes must focus on reacting quickly against the ground, and keeping the torso lifted.
5. Short leaps: to learn horizontal centre of mass translation, repeat at least 5 consecutive leaps (on stairs, if subject can do it), then jump on one leg, focusing on extension (at least 10 jumps per leg)
6. Long leaps: to increase horizontal speed, alternate jumps on one leg with combinations of short jumps or skipping (10 to 20 contacts to the ground maximum)
7. Plyometric falls: very demanding drills for the nervous system. This is an advanced training method that needs an adequate base, and implies falling from elevated surfaces or jumps between tall obstacles.

Safety observations
● Warm-up: complete and appropriate warm-up must precede any drill that involves strength, power, speed, endurance and dexterity. Warming up should be followed by general and specific stretching (for the muscular groups that are going to be worked out by plyometrics).
● Training sequence: Top neuromuscular activity is reached whenever the athlete is rested. Plyometrics should precede any other activity in order to get the best possible effects.
● Progression: athletes must start with easy drills, increasing difficulty little by little
● Medical problems: After injury or rehabilitation, plyometrics should be avoided.

Equipment safety
● Surface: all drills involving leg movement should be completed on not too hard terrain. Working area must be dry, flat and obstacle-free.
● Obstacles: Caution must be taken with obstacles. They should be not fixed (to move away if hit by athlete) and possibly light, in order to evade injuries and damages.
● High-planes: their elevation can vary depending on the drill’s intensity and athlete’s ability, but too high could spell for injury.
● Shoes: very important matter. They should offer a high degree of lateral stability, anti-slipping soles, and good cushioning on landing.

Health safety: Orthopaedic equipment to prevent traumas
● Weightlifters belt: it helps to bring forward a correct spinal posture in the lumbar/lumbosacral area. This belt does not solve all postural problems, but improves lumbar zone perception, so favours a good posture before and during movement inversion. During squats and jumps, intervertebral disks are subjected to elevated pressure; which is compensated by an increased intra-abdominal pressure (reducing about 40% vertebrae pressure: Cometti-Gilles, 2002).
● Heels wedge: balance is essential during weight lifting, in particular during squats heel elevations are instinctively acted (so the chances to loose equilibrium are high).
● Kneecap devices: very efficient to reduce vibrations that propagate to the tendon during jumps, especially for athletes that are sensible and suffer inflammations in the kneecap.
● Push kneepads: useful for their good mechanic support on an unstable knee or patella injuries.
● Heel support: polymeric holder with stabilizing wall and soft silicon insert. Used by athletes recovering from certain foot pathologies, which require vibration absorption and reduction of heel transmission to the spine during plyometric training.

Technique safety
In avoidance of injury, before starting a planned plyometric training, an adequate general strengthening period must be put forward, aiming to obtain the needed biological adaptation and reinforcement of the concerned structures (tendons, ligaments, capsules, internal joints, etc).
Chances of injury increase notably if there is a poor balance between the body segments’ muscular strength, which in turn signifies a less efficient improvement of speed strength. Accordingly, a preliminary muscular reinforcement period is definitely essential.
Also, before starting plyometric training is imperative to develop strength in stabilizing muscles. Once again, we’ll stress out that landing has to occur with the whole foot instead of heels/toes, so the impact forces are correctly transmitted to the calves and knees, saving metatarsal heads in the process.
To avoid functional overcharge to the spine, it is necessary to reinforce the dorsal/erector muscles, the rotators and abdominals.
Also, skaters afflicted with paramorfisms (foot, knees and hips) should pay attention to carefully execute plyometric drills.

Conclusions

Prof. Bosco has annotated dissimilar response from several subjects:
- male athletes are able to sustain higher stretching workloads than females;
- female athletes are able to store up higher quantities of elastic energy than males;
- aged athletes have lower response to muscular stretching
- muscles with short fibres and long tendons (i.e. sural triceps) can amass more elastic energy than muscles with long fibres and short tendons.

In my opinion, this explosive strength gaining method is very effective for inline skating, but safety regulations must be thoroughly followed to avoid functional overload. The coaches’ experience and sensibility should be sufficient to come across the best possible drills for each athlete (depending on their age and fitness level), and the required training intensity.
I’m available to any discussion or exchange of ideas about such a fascinating topic, on our quest to further develop this wonderful sport our athletes are so passionately practising with so much sacrifice.
Have a nice skate!

Rosario Bellia
Originally published in italian on www.simonebellia.com >> - Translation: M. Bresin

Bibliography

1. C. Bosco, Elasticità muscolare e forza esplosiva nelle attività fisico-sportive - Soc.Stampa Sportiva, Roma,1985.
2. C. Bosco, La forza muscolare / Aspetti fisiologici ed applicazioni pratiche –
Soc. Stampa Sportiva, Roma, 1997.
3. P. Bellotti , Matteucci E., Allenamento sportivo – UTET, Torino, 1999.
4. G. Cometti, Metodi di potenziamento muscolare – Calzetti-Mariucci, Perugia, 1997.
5. G. Cometti, Manuale di potenziamento muscolare per gli sport di squadra – Calzetti-Mariucci, Perugina, 2002.
6. B.Baldoni & A. Dispensa, Manuale di educazione fisica – ed. Capitello ,Torino,2006.
7. R.G.Danowski & J. Chanussot, Traumatologia dello sport – ed. Masson,Milano, 2000.
8. Fiorini, Corelli, Bocchi, Corpo libero due movimento e salute – Marietti- Novara 2006.
9. Rossi, Borgogni, Piccioni, I mondi dello sport – ed. Bruno Mondadori – Milano – 2006.
10. De Nista, June Paker, Tasselli, Praticamente sport – ed. D’Anna – Firenze – 2005.


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