EP2263759A1 - Muscle-building appliance offering a load differential between the concentric and eccentric exercise modes - Google Patents

Abstract

The apparatus has a frame (1), and an element that is intended to be mobilized with respect to the frame by a user of the apparatus along back and forth movement for exerting muscular or muscles groups in an eccentric mode and a concentric mode. Pneumatic jacks (5, 6) are provided for realizing difference in load between the concentric mode and eccentric mode, where the jacks are actuated using an actuator with hand or foot accessible to the user for repeating movement at each time.

Description

Bodybuilding apparatus providing a load differential between concentric and eccentric exercise modes Background of the invention

The present invention relates to the general field of bodybuilding, gymnastics or rehabilitation apparatus comprising a frame and at least one element intended to be mobilized with respect to this frame by a user of the apparatus in a back and forth motion allowing to exercise, successively, muscles or muscle groups, in eccentric mode and in concentric mode.

More particularly, the invention relates to weight machines for working with an eccentric mode load greater than the load in concentric mode.

The current training in bodybuilding is actually pushing and holding the same weight load. Thus, the resistance does not vary between the forward movement and the return movement. The variables of the training with the conventional machines concern the quantity of movements carried out, series and repetition, the speed of execution, the amplitude of the movement and the time of rest. The load is a possible variable between each set and can not usually be changed during the movement.

The advantage of changing the load during the movement is to be able to precisely obtain a higher load when the user works in eccentric mode.

Indeed, in the execution of a movement, the motor muscles contract in a phase corresponding to the forward movement and stretch in a phase corresponding to the return movement. When the muscles contract, we talk about concentric movement and when the muscles stretch, we talk about eccentric movement.

Physiologically, the muscles have a greater force in the eccentric phase than in the concentric phase. Thus, typically, one can retain a load greater than that which can be pushed.

There are already devices allowing work with a larger load in eccentric mode than in concentric mode.

Among these, there is known an apparatus in which the load is modified by a change of a pressure applied under the load displaced by the user thanks to a jack. This device is based on a principle of assistance to go and return, this assistance is differential and always offsetting part of the stack of weight.

In known embodiments, the compensation is also often automatic and changes when the user reaches the end of the race. This causes problems when, for example, the user slows down during his movement or even stops his movement in the middle of pushing. In this case, the automatic switchover may cause a change in the compensation. Such a sudden and unexpected change in the middle of the movement can be dangerous for the user who will be surprised.

Furthermore, this embodiment implies that the cylinder operates in a closed pneumatic circuit and that the volume containing the air under pressure varies with the stroke of the cylinder. The air circuit being a closed circuit, the volume of air varying with the movement, the pressure also varies with the movement. The pressure thus varies inversely with the volume. As the assisting force varies with movement, the residual charge also varies with it.

As it is a question of being able to compensate up to the totality of the stack of weight on the totality of the race, the variation of the volume of the pressure is then necessarily important.

This pressure variation is detrimental to the quality of the movement because it results in a variation of the compensation force. Also, a not inconsiderable variation of the residual charge between the low point and the high point of the weight stack is observed.

Solutions to solve this problem have been proposed. In particular, the use of a buffer reserve in communication with the cylinder chamber reduces the impact of the pressure variation during the movement. The volume of the reserve can be much larger than that of the cylinder chamber. Thus, the ratio between the volume of the cylinder chamber and the total volume is reduced and the impact of the change in volume also.

It was thus proposed a direct integration of a cylinder without a bottom in the heart of the buffer. As the cylinder then communicates directly with the reserve without passing through a pipe, no flow problem arises.

This made it possible to implement a jack to compensate for the load, and to adjust the load generated by commands, in particular manual controls, as a function of the desired load to the forward movement and to the return movement.

Nevertheless, the pressure change during the movement is limited to small variations of the order of 5 to 10 kg. Beyond and, given the volume of the reserve, the time to change the pressure is too long to allow proper use. The device is in particular not fast enough to ensure variations of the order of 30 to 40 kg.

However, such rapid and significant changes are necessary for the use of a load differential in concentric and eccentric mode.

Other systems have been developed. It is in particular known to exert an additional force to the weight stack by means of an electric motor connected to this stack by a strap. The traction force of the motor is then added to the load of the weight stack. Such a solution has the disadvantage of being very expensive and to propose an eccentric load formed of the combination of traction and the force of gravity. This can annoy users because they seek sensations related to the only force of gravity. In addition, the use of the electric motor generates jolts in the operation of the apparatus during the addition of the tensile load.

There is also a system based on the use of an inclination of the concentric phase weight stack, which is then repositioned vertically into eccentric phase. Thus, in the concentric phase, the force of gravity is reduced thanks to the inclination. Such a solution is expensive and complex to implement technically. It also poses problems of safety and reliability.

Object and summary of the invention

The main purpose of the present invention is therefore to overcome the drawbacks of the known apparatuses to allow differential work in eccentric mode and concentric mode by proposing a bodybuilding, gymnastics or rehabilitation apparatus comprising a frame and at least one element intended to be mobilized relative to the frame by a user of the apparatus in a back and forth movement for successively exercising muscles or muscle groups in eccentric mode and concentric mode, the apparatus being such that it allows to work with a load in eccentric mode greater than the load in concentric mode, characterized in that the load in one of the two modes being provided by weights selected by the user in a stack of weights and carried by a support integral with the element mobilized by the user to be mobilized vertically, at least one jack On-off pneumatic system achieves the difference in load between the concentric and eccentric modes, the load in the other of the two modes being that of the weights selected in the weight stack decreased or enhanced by the action of the fully functioning cylinder. nothing, the cylinder being intended to be actuated by a hand or foot actuator accessible to the user each time it repeats the movement.

The invention therefore proposes to work by lifting the entire load of the weight stack while having the possibility to relieve all or part of this load by actuating the jacks when the user lifts the load or while having the possibility of increase this charge when the user holds it.

The invention therefore uses for this purpose one or more pneumatic cylinders for compensating or reinforcing the counterweight constituted by the weight stack. The invention implements, in parallel with the apparatus, an ancillary pneumatic system, comprising at least one compressor, valves and control buttons.

Thus, the invention consists in the implementation of one or more pneumatic cylinders placed (s) so as to be able to either assist the movement of the moving weight stack vertically in concentric mode, or to accentuate the load in eccentric mode. Such use of a pneumatic cylinder is new compared to the use generally observed in weight machines. In general, in machines using a jack, the user performs an exercise by fighting the thrust of the cylinder or against its traction. Such devices are precisely devoid of weight piles since the load is achieved using the cylinder.

In addition, even if there are double effect cylinders that can operate in both directions by inversion of the air supply to and from the return, the known devices operating with a cylinder do not generally allow an effort in a movement back and forth and the cylinder then allows resistance only in one direction of movement.

The invention preserves the feeling of working with a weight stack while optimizing work in eccentric mode and concentric mode. Indeed, in one of the modes, the user suffers only the weight of the selected weights in the weight stack while, in the other mode, the force exerted on him is either relieved by the jack, or increased by the jack. Optimal physiological effects are thus obtained.

Thus, the invention proposes to use a pneumatic cylinder in all or nothing mode in combination with a load selected in a weight stack, this load can be modified, conventionally, using a mechanical key.

According to the invention, the modification of the overall load between the concentric and eccentric modes being carried out by simple actuation of one or more cylinders, this makes it possible to use simple control buttons of the jack or cylinders accessible to the user for to modify, himself and at the moment he wishes, the charge which he raises and which he retains in concentric and eccentric mode.

Note that, according to the invention, in assistance, it is not necessary to compensate for the entire weight stack but only a part. Cylinders of smaller diameter than in the case of the apparatus of the prior art can therefore be used. The advantage is similar when it comes to boosting the load in eccentric mode.

This reduces the volume of air used and improves the reaction speed of the cylinders which do not need to present buffer air reserves.

Thus, compact cylinders can be mounted without significant modification on conventional mass-produced machines.

This normally decreases the manufacturing cost of the apparatuses according to the invention and thus makes it possible to equip existing apparatuses with the option of differential load in eccentric mode and in concentric mode.

Note also that, insofar as the cylinder operates in all or nothing mode, reaction times, filling and exhaust air, are very short and therefore allow use in an apparatus for working differentially in mode eccentric and concentric with load modifications quite consistent and effective.

Advantageously, the jack makes it possible to compensate up to 40% of the total load of the weight stack in concentric mode or to add up to 40% of the total load of the weight stack in eccentric mode. Indeed, there is no problem of inertia or reaction time even for large loads of the order of 40 kg. Thus, the invention makes it possible to make load variations between the forward movement and the return movement of up to 40-50 kg and, in particular, it is possible to pass, for example, from 40 to 80 kg very fast and without annoying sensations for the user.

Indeed, the load in one of the two modes depending on the load selected by the user in a stack of weights with a selection system by means of a key, the assistance device using the pneumatic cylinder serves only to realize the difference in load between the concentric and eccentric phases. Thus, it is only a matter of canceling the operation of the device for assisting or reinforcing the load by evacuation of the air, there is no significant reaction time when switching from the "all" mode to the "nothing" mode and vice versa.

According to a very advantageous feature of the invention, the jack is fixed on the frame on one side and resting on a tab integral with the weight stack of the other.

The positioning of the jack bearing on the lug secured to the weight stack allows the rod, in single support, enters alone in the body either by gravity or with the aid of a biasing element, typically a spring integrated in the jack when the cylinder is deactivated. Thus, when the invention is implemented in assistance in concentric mode, when switching to eccentric mode, the user who deactivated the actuator cylinder through the actuator undergoes the load of the weight stack without any restraint due to the presence of the cylinder.

Indeed, the rod returns by gravity into the body when the cylinder is disabled and the weight stack is the only one charge to be applied to the lever manipulated by the user. This is a major advantage of the invention since many users of this kind of devices wish to have the only feeling of gravity return to eccentric mode.

Indeed, as the feeling of a job associated with the output of a rod of a cylinder is perfectly tolerated as the feeling of a job associated with a return of the rod in the cylinder is unpleasant for the user. As, according to the invention, the cylinder operates in open circuit, it is not observed problems of pressure variation requiring buffer reserve, contrary to what was necessary in the devices of the prior art.

Also, if the cylinder is not supplied with compressed air, for example because of a compressor failure for consumer use, the machine remains operational because it operates in this case as a conventional machine with a load selected in a stack of weight. In this case, the rod of the jack in single support remains in the body when the system is such that the jack operates in thrust or on the contrary remains out of the body when the system is such that the jack operates in tension and does not participate in any movement of the weight stack. This is not possible in the apparatus of the prior art which are specifically differential between concentric mode and mode eccentric. In a first embodiment, the jack provides concentric motion assistance, the selected load in the weight stack then defining the load in eccentric mode.

This embodiment makes it possible to artificially mount the load of the counterweight by means of one or more jacks. In this embodiment, the relief of all or part of the mobile counterweight can be eliminated by purging the cylinders during the return of the load to its initial position.

In a first implementation of this embodiment, the cylinder or cylinders, comprising a rod and a body, operate in thrust and are positioned vertically on one side of the stack or on both sides of the stack of weights. and at the level of the support of the weight stack, the rod of the jack or cylinders being positioned upwardly against a tab integral with the support of the weight stack and the body of the jack or cylinders being, on the bottom, fixed on the chassis of the device.

Advantageously, two cylinders are here positioned vertically on either side of the guided mobile counterweight. The implementation of the pneumatic jack makes it possible to relieve the guided load. This positioning of the jacks under the legs of the support of the weight stack makes it possible to use conventional jacks since the size of the support of the weight stack authorizes the use of a jack rod of reasonable size. In addition, the simple support of the stem on the leg allows the stem to descend naturally into the body by simple gravity.

According to another embodiment of the first embodiment, the cylinder or cylinders comprising a rod and a body, operate in traction and are positioned vertically, above the support of the weight stack, the rod of the cylinder or cylinders being positioned towards the bottom resting on a tab of the support of the weight stack and the body being, on the top, fixed on the frame of the apparatus.

With this implementation, the pneumatic cylinder is positioned vertically with its rod directed downwards to relieve the load during the concentric movement by lifting it. For this the rod passes through the leg through an orifice whose leg is provided. The rod comprises a washer or other stop device located at the end of the rod and abutting the contour of the orifice of the tab. The washer is then resting on the tab during operation of the cylinder, this support being on the underside of the tab. This stop allows the rod to relieve, by traction, the load during the concentric movement. When the cylinder is not activated, the rod falls downwards by sliding in the orifice by gravity and thus does not cause any discomfort when the return movement in which the leg slides along the stem down.

In a second embodiment, the jack produces an additional force to be retained during the eccentric movement, the weight stack then defining the load in concentric mode.

Here, the jack adds load when moving in eccentric mode. It is not a question of an "assistance" to the effort of the user strictly speaking but of an assistance with the efficiency of the exercise which consists precisely to add the load in eccentric mode.

In a first implementation of this embodiment, the cylinder or cylinders, comprising a rod and a body, operate in tension and are positioned vertically on one side of the stack or on both sides of the stack of weights. and at the level of the support of the weight stack, the rod of the jack or cylinders being positioned upwardly against a tab integral with the support of the weight stack and the body of the jack or cylinders being, on the bottom, fixed on the chassis of the device.

In this embodiment, again, the tab comprises an orifice through which the rod has a washer or other abutment device at its highest end to come to rest on the tab and pull it down when the cylinder is activated in traction. The washer then bears on the leg on the upper face of the leg.

Advantageously, the jack comprises an expansion element, typically a spring integrated in the cylinder body, to push the rod out of the body when the cylinder is switched to nothing mode.

The presence of the rod thus causes no discomfort during the concentric movement in which the leg slides along the rod which is raised upwards.

In a second implementation, the jack or cylinders, comprising a rod and a body, operate in thrust and are positioned vertically, above the support of the weight stack, the rod of the jack or cylinders being positioned downwards in support on one leg of the support of the weight stack and the body being, on the top, fixed on the frame of the apparatus.

Advantageously, the jack comprises a rod return member to bring it up in the body when the cylinder is switched to nothing mode.

We note here that it would be equivalent, although less easily achievable, in one or other of the embodiments, to reverse the positions relative to the body and the rod of the jack and / or their types of links with the frame or the tab integral with the weight stack. The essential is, according to the invention, that the body or the rod of the jack is fixed to the leg or the frame while the other part of the jack is in simple support on, conversely, the frame or the leg, left to provide the cylinder with a return or detent element of the rod when the latter is oriented downwards respectively upwards.

Thus, depending on the embodiment, the cylinders can be used to relieve the moving load go or serve to accentuate the load on return.

It will be noted here that the use of two jacks under load and at least one thrust cylinder above the latter can, by implementing the invention twice, to obtain an apparatus in which the charge is raised on the go of the movement and the mass of the pile of weight is accentuated in the return movement. Such an embodiment allows the user to choose which concentric or eccentric mode he prefers to assist, either by a discharge made by the jack placed under the lug secured to the weight stack, or by an overload carried by the jack placed at above the paw secured to the weight stack.

Finally, according to a particular characteristic of the invention, the apparatus further comprises end of movement detection means for automatically controlling the change in operation of the jack.

This feature carries some risk for the user who may be surprised by the automatic load modification. Nevertheless such automatic operation in addition to the normal operation according to the invention where an actuator is used may be useful especially for people who have become used to working on this type of machine.

According to another particular feature of the invention, the apparatus comprises an additional control to remove at will the air supply cylinders allowing the use of the machine as a traditional machine.

This feature can be very beneficial in the centers of bodybuilding or fitness to make the machine versatile according to the public attending the establishment. Either the machine has a classic operation, reassuring for the regular customer, or the machine has a differential operation, more specifically dedicated to a particular clientele. The invention thus avoids having to equip the establishment with two machines, the same equipment to satisfy both types of customers.

Brief description of the drawings

• les figures 1A et 1B représentent une tour d'un appareil de musculation selon l'invention, respectivement en vue de face et en perspective ;
• la figure 2 montre un exemple d'appareil de musculation utilisant une tour telle que représentée sur la figure 1 ;
• les figures 3A, 3B et 3C montrent trois étapes du fonctionnement d'une mise en oeuvre particulière de l'invention ;
• la figure 4 montre un mode de réalisation particulier de l'invention ;
• la figure 5 montre un autre mode de réalisation particulier de l'invention ;
• la figure 6 montre encore un autre mode de réalisation particulier de l'invention.

Other features and advantages of the present invention will emerge from the description given below, with reference to the accompanying drawings which illustrate an embodiment having no limiting character. In the figures:

• the Figures 1A and 1B represent a tower of a weight training device according to the invention, respectively in front view and in perspective;
• the figure 2 shows an example of a weight training device using a tower as shown on the figure 1 ;
• the Figures 3A , 3B and 3C show three stages of operation of a particular embodiment of the invention;
• the figure 4 shows a particular embodiment of the invention;
• the figure 5 shows another particular embodiment of the invention;
• the figure 6 shows yet another particular embodiment of the invention.

Detailed description of an embodiment

The figure 1 shows a tower in which the invention is implemented. The tower comprises a frame 1 supporting at least two slides, here four sliders referenced 10, 11, 12 and 13 on which slide weights selected from a stack of weight 2, typically consisting of several steel plates, here 12 plates, associated a selector 3 having a mechanical key 4 for selecting weights.

With this key 4, it is possible to select all or part of the plates at the start of the exercise. On the Figure 1A only four plates were selected. The sliders 10, 11, 12 and 13 guide the weights directly in the tower of the weight machine.

In accordance with what is generally practiced, the user pulls on the selected weights in the weight stack 2 by means of a strap or cable attached to the guided load 2 at a point 33 connected to the selector 3. The element of mobilization, classic and well known in the field of sports machines is generally in the form of a wide handlebar that hangs from above the user's head and that the user catches before pulling it down. This element not shown in the figures presented is very conventional.

On either side of the weight stack 2 are placed cylinders 5 and 6 embodying the invention. According to the invention, the bodies 51 and 61 of the cylinders are fixed vertically on the frame of the tower of the weight training apparatus. The rods 52 and 62 of the two cylinders are themselves supported on lugs 31 and 32 themselves fixed, for example by welding, on the selector 3.

Thus, when the cylinders which operate here in thrust are actuated, the rods 52 and 62 push the selector 3 and therefore the load 2 upwards.

The thrust of the cylinders is a function of the pressure sent into the cylinders. It can be selected more or less strong, which allows to adjust the help to lift the load. Nevertheless, according to the invention, once a given differential load has been set, actuation and operation of the jack is in all-or-nothing mode, ie air is sent into the jack and the jack is active, or it is deactivated and the cylinder then no longer exerts any force.

Since the jacks push the load upward depending on the pressure of the jacks, the traction produced by the user needed to lift the load will be reduced. Thus, the work in concentric mode will be performed on a smaller load than that in eccentric mode, in which the cylinder is inactive.

The cylinder, once deactivated, sees its rod, until then resting on the leg, fall back into his body by gravity. This return in the cylinder body is ensured by the all-or-nothing operation of the cylinder combined with gravity. Thus the user then supports the entire weight stack and only this one in eccentric mode. The cylinder therefore introduces no friction or assistance when it is switched to nothing mode.

Actuation and stopping of the operation of the cylinder at the beginning and at the end of the movement or during the movement in concentric mode or in eccentric mode is provided according to the invention with the aid of a control which can be hand or foot. The positioning of the order will advantageously be provided at the level of the members not concerned by the exercise. For example, if the exercise is for the arms, the control will be located at the level of the feet and vice versa. This allows a comfortable use of the device. Thus, with this control means, the user can choose to lift a certain load and then remove the pressure in the cylinders to retain the selected load in the weight stack without assistance when returning to the initial position.

The apparatus further advantageously comprises means for adjusting the pressure in the jacks during exercise, which can vary all the effort of the user increasing or decreasing during the mode concerned by the operation. the cylinder but always in a principle of all or nothing of the cylinders associated one concentric mode and the other eccentric mode.

The figure 2 represents a weight machine with a tower as shown on the figure 1 .

On the frame 1 of this tower, are mounted a bracket 14 and a user support 15 allowing the user, installed on the support 15, to raise and lower the load 2 by means of a strap or a cable attached to the load at point 33. This strap or cable then passes through a number of pulleys, here 15 and 16, supported in particular by the bracket 14.

It should be noted here that the planned exercise concerns the arms and the upper body. Advantageously, the command to put in operation and to stop the jacks will be a foot control positioned at the level of the bearing 17 or close thereto.

Note finally that various implementations can be made according to the principles of the invention as defined in the following claims. Note that the tab can be an integral part of the selector 3. This is shown on the figure 3 where a spar 310 uniting in one piece the functions of the two lateral lugs 31 and 32 of the embodiment described above. The spar 310 is here secured to the selector 3 by fastening elements 311. The rods 52 and 62 are provided with bearing pads 520 and 620 resting on the spar. On the figure 3A , the device is at rest. On the figure 3B , the device is in concentric phase. In this phase, the rods of the cylinders, activated by the user, are supported on the spar and push the beam upwards. On the figure 3C at the beginning of the eccentric phase, the rods 52 and 62 have fallen back into the bodies of the cylinders 5 and 6 while the spar, the selector and the weight stack are still in the up position and weighing on the user who will retain them during the whole descent.

In addition, the support of the cylinder or cylinders may be of various kinds and the cylinder can operate either in traction or thrust. The Figures 4 to 6 describe three other embodiments according to the invention. On the figure 4 , jacks 5 and 6 are mounted between, on the bottom, a beam 310 and, at the top, the frame 1 of the device. The rods 52 and 62 are here oriented downwards and the cylinders operate in traction mode concentric to help lift the selected weights in the weight stack. For this, the rods 52 and 62 pass through the spar 310 in two lateral orifices and buffers 520 and 620 are then placed at the ends of the rods 52 and 62. These buffers 520 and 620 abut under the spar 310 when they are in tension and allow the rods 52 and 62 to pull it upwards. When the traction work is interrupted by action of the user, the rods of the cylinders 5 and 6 fall down by gravity out of the body of the cylinders.

The figure 5 shows for its part an embodiment where a reinforcement of the load is achieved by jacks 5 and 6 in the eccentric mode. In this embodiment, the cylinders 5 and 6 are placed under a spar 310. The rods 52 and 62 here pass through the spar 310 at two lateral orifices. The rods 52 and 62 are provided at their ends with buffers 520 and 620 abutting on the top of the spar 310 when the rods 52 and 62 are actuated in tension. This traction which corresponds to penetration of the rods 52 and 62 in the cylinder body has the effect of pulling the beam 310 down which adds a force against which the user of the device will resist in eccentric mode. Once the traction deactivated by the user, the rods are advantageously expelled from the cylinder bodies by an expansion element, typically an internal spring, which brings out the rods 52 and 62 of the cylinder body.

The figure 6 shows again an embodiment where the load in eccentric mode is reinforced. For this, cylinders 5 and 6 are placed on the top of a spar 310 and their rods 52 and 62 operate in thrust downwards. Tampons 520 and 620 at the ends of the rods 52 and 62 press on the spar 310 and reinforce the load retained by the user. Advantageously, the cylinders 5 and 6 are provided with biasing elements to recall the rods 52 and 62 inside the cylinder body when their action is disabled by the user.

Thus in all these embodiments, the action of the cylinder is felt by the user only when it is active. This avoids the bad sensations due to the return of the stem in the initial position after it has been active. In known devices, the presence of the cylinder, generally used to relieve the load, is constantly undergone even when it is not active.

Claims (12)

Bodybuilding, gymnastics or rehabilitation apparatus comprising a frame (1) and at least one element intended to be mobilized with respect to the frame (1) by a user of the apparatus in a back and forth movement for exercising successively muscles or muscle groups in eccentric mode and in concentric mode, the apparatus being such that it makes it possible to work with a load in eccentric mode greater than the load in concentric mode, characterized in that , the load in one of the two modes being ensured by weights selected by the user in a weight stack (2) and carried by a support (3) integral with the element mobilized by the user to be mobilized vertically, at least one pneumatic cylinder ( 5,6) performs the load difference between the concentric and eccentric modes, the load in the other of the two modes being that of the selected weights in the weight stack. s (2) decreased or enhanced by the action of the cylinder (5,6) to all-or-nothing operation, the cylinder (5,6) being intended to be actuated by a hand or foot actuator accessible to the user whenever it repeats the movement. Apparatus according to claim 1, characterized in that the jack is fixed on one side to the frame and, on the other side, resting on a tab integral with the selected weights in the weight stack. Apparatus according to one of claims 1 and 2, characterized in that the jack (5, 6) is adapted to assist the movement in concentric mode, the weights selected in the weight stack (2) then defining the load in eccentric mode. . Apparatus according to claim 3, characterized in that the jack or cylinders (5, 6), comprising a rod (52, 62) and a body (51, 61), operate in thrust and are positioned vertically on one side of the weight stack (2) or on both sides of the weight stack (2) and substantially at the support (3) of the weight stack (2), the rod (52,62) of the cylinder (s) (5,6) being positioned upwardly resting on a tab (31,32) integral with the support (3) of the weight stack (2) and the body (51,61) of the cylinder (s) (5,6). ) being, on the bottom, fixed on the frame (1) of the apparatus. Apparatus according to claim 3, characterized in that the cylinder or jacks (5, 6) comprising a rod and a body operate in tension and are positioned vertically above the support (3) of the weight stack (2), the rod of the cylinder (s) (5,6) being positioned downwardly on a lug (31,32) of the support (3) of the weight stack (2) and the body being, on the top, fixed on the chassis (1) of the device. Apparatus according to one of claims 1 and 2, characterized in that the cylinder (5, 6) is adapted to apply additional force to be retained by the user during the eccentric movement, the weights selected in the weight stack. (2) then defining the charge in concentric mode. Apparatus according to claim 6, characterized in that the one or more cylinders (5, 6), comprising a rod and a body, operate in traction and are positioned vertically on one side of the weight stack (2) or on the one hand and other of the weight stack (2) and substantially at the support (3) of the weight stack (2), the rod of the cylinder (s) being positioned upwardly on a leg (31,32) secured to the support (3) of the weight stack (2) and the body of the cylinder (s) (5,6) being, on the bottom, fixed to the frame (1) of the apparatus. Apparatus according to claim 7, characterized in that the jack comprises an expansion element, typically a spring integrated in the cylinder body, to push the rod out of the body when the cylinder is switched to nothing mode. Apparatus according to claim 6, characterized in that the cylinder or cylinders (5, 6), comprising a rod and a body, operate in thrust and are positioned vertically, above the support (3) of the weight stack (2). , the rod of the cylinder (s) (5,6) being positioned downwardly on a lug (31,32) of the support of the weight stack (2) and the body being, on the top, fixed on the frame (1) of the device. Apparatus according to claim 9, characterized in that the cylinder comprises a rod return member to make it up in the body when the cylinder is switched to nothing mode. Apparatus according to one of the preceding claims, characterized in that it further comprises end of movement detection means for automatically controlling the change in operation of the jack. Apparatus according to one of the preceding claims, characterized in that it comprises an additional control to remove at will the air supply cylinders allowing the use of the machine as a traditional machine weight stack.

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