FR3064592A1 - PEDALIER OF AN EXERCISE BIKE INTENDED TO BE IMMERSIONED IN A LIQUID - Google Patents

Abstract

The invention relates to a pedal of an exercise bike intended to be immersed in a liquid, comprising two cranks, both movable in rotation about the same axis called "hub M", the pedal having two pedals, a pedal left movable in rotation about an axis connected to the left crank, said "left axis AG", and a right pedal movable in rotation about an axis connected to the right crank, said "right axis AD", the pedals comprising drag devices, the drag devices being configured to undergo a fluid friction force opposing the circular translation movement of the pedals, the drag devices having portions of cylinders of revolution located under the pedals in an operative position, axis of revolution of the left cylinder being coincident with the left axis AG, the axis of revolution of the right cylinder being coincident with the right axis AD.

Description

TECHNICAL FIELD OF THE INVENTION

The present invention is in the field of apparatus for sport and physical medicine and rehabilitation. More particularly, the invention relates to a crankset of a stationary exercise bike intended to be immersed in a liquid.

STATE OF THE ART

For people who have undergone surgery, following an injury or after an accident, or for people with disabilities, physical exercise in water is very beneficial. In particular, a person who exercises in a swimming pool is weightless. It is therefore possible for this person to work his lower limbs without them having to support the weight of his body. This can be useful in the case of people with weak limbs. In addition, exercise in water involves much less shock and trauma to the joints than exercise in air, which is very beneficial for people in rehabilitation. But the benefits of exercising in the water don't stop with physical medicine and rehabilitation, and many able-bodied athletes also train in this way.

For this purpose, there are several devices for sport and physical medicine and rehabilitation in water. In particular, the prior art proposes a sports or medical exercise device simulating pedaling on a bicycle, known as an exercise bike, which can be used in water. The crankset of this exercise bike includes a hub, two cranks and two pedals. The pedals are plastic plates on which the user places his foot.

This type of device has drawbacks. They are not adapted to the variety of morphologies and existing pathologies. Due to the shape of the pedals, the friction exerted by the water is more or less important depending on the position of the cranks around the hub. In particular, during the pedaling phases where the pedals mainly have a horizontal movement, the water exerts a much lower friction than during the pedaling phases where the pedals mainly have a vertical movement.

These large variations in the force exerted by water on the pedals involve risks of jolts and unexpected movements, which are very bad for a user in rehabilitation. The risks are particularly high for people who have had an Achilles tendon operation.

The present invention aims to overcome the drawbacks of the solutions proposed by the prior art for sport and physical medicine and rehabilitation, by providing a pedal board of an exercise bike intended to be immersed in a liquid, which is adaptable to all human pathologies and morphologies, and does not create jolts or harmful effort for people whose ligament, muscle or joint in particular are weakened.

OBJECT OF THE INVENTION

To this end, the invention relates firstly to a pedal board of an exercise bike intended to be immersed in a liquid. The crankset has two cranks, called "left crank" and "right crank", both of which are movable in rotation about the same axis called "hub M". The crankset has two pedals, a left pedal movable in rotation about an axis linked to the left crank, called "left axis AG", and a right pedal movable in rotation around an axis linked to the right crank, called " right axis AD >>. The pedals perform a circular translational movement around the hub M when pedaling. The pedals include drag devices, respectively called "left drag device >> and" right drag device >>. The drag devices are configured to undergo a fluid friction force opposing the circular translational movement of the pedals. The drag devices comprise portions of cylinders of revolution located under the pedals in the operating position, respectively called "left cylinder" and "right cylinder". The axis of revolution of the left cylinder coincides with the left axis AG. The axis of revolution of the right cylinder merges with the right axis AD.

In Mathematics, by cylinder of revolution is meant a surface generated by the revolution, around an axis called the axis of revolution, of a straight line parallel to this axis.

By portion of cylinder of revolution is meant a part having the shape of a cylinder of revolution truncated along at least two distinct planes.

By operating position is meant the normal pedaling position, a user having put one foot on each of the pedals, his muscular action causing the pedals in circular translation around the hub M. By the pedal, we denote the face of the opposite pedal to the face on which the user has placed his foot. The left cylinder is located under the left pedal and the right cylinder is located under the right pedal.

The drag devices according to the invention have the advantage of smoothing the effort to be provided by the user during the pedaling cycle, that is to say of limiting sudden jolts and movements. Indeed, by their shape, the drag devices undergo a fluid friction force which varies relatively little throughout the pedaling cycle. The forces exerted by the liquid on the pedals are smoothed, they vary little whatever the angular position of the pedals around the hub M. In fact, the cylindrical shape of the drag devices guarantees that their transverse surface (or master torque) will vary little regardless of the angle of attack of the liquid on these drag devices. As the friction force exerted by a liquid on a solid is proportional to this transverse surface, then the force exerted by the liquid on the drag devices varies little throughout the circular translation of the pedals around the hub M of the crankset.

In particular, the pedals on which the foot rests tend to remain horizontal throughout the pedaling cycle, not creating any particular effort on the user's Achilles tendons, unlike the pedals offered by art prior. The efforts on the Achilles tendons are very bad for people who have had an operation on this area of the foot.

According to particular embodiments, the invention also meets the following characteristics, implemented separately or in each of their technically operating combinations.

In a particular advantageous embodiment, the cranks are of adjustable lengths.

The length of a crank means the distance between the hub M and the axis of the pedal linked to this crank (the left axis AG or the right axis AD).

The adjustable length of the cranks makes it possible to adapt the crankset to all morphologies and pathologies, which has an obvious advantage for the exercise of people in physical medicine and rehabilitation. In addition, the lengths of the left and right cranks can be adjusted independently of each other, which has an advantage for the rehabilitation of people whose one limb is weaker than the other, or one of whose limbs is shorter than the other.

In one embodiment, the left and right cylinders are both pierced with at least one through hole, respectively called left light and right light.

The through hole (s) drilled in the cylinders allow the liquid to flow through the cylinders on the surface of these openings, thereby reducing the friction force exerted by the liquid on the cylinders. Indeed, the force exerted by a liquid on a solid is proportional to the transverse surface (or master-couple) of this solid.

In one embodiment, the surface of the lights is adjustable.

By left light area, respectively right light, is meant the sum of the areas of all through holes made in the left cylinder, respectively in the right cylinder.

By varying the surface of the lights, you can vary the force that the liquid will exert on the drag devices when using the pedal board. This adjusts the resistance of the pedal to the pedaling effort of the user. In other words, we thus adjust the difficulty of pedaling. This has the great advantage of making it possible to adapt the crankset to all users. A sports user can reduce the surface of the lights or even close them, to obtain more difficult pedaling. On the contrary, a weak user will open the surface of the lights, making pedaling easier.

In addition, this advantageously makes it possible to support the progression of a patient throughout his rehabilitation. Indeed, at the start of the treatment, while the patient has still weak limbs, it is possible to adjust the drag devices to imply a minimum pedaling effort. The difficulty may be increased as the patient recovers muscle strength in his limbs.

In one embodiment, the surface of the left light is adjustable independently of the surface of the right light.

This advantageously makes it possible to adjust the difficulty of pedaling independently on the left foot and on the right foot. This can be very useful for patients who have experienced asymmetric trauma. For example, a person operated on one leg but whose other leg is in good health will benefit from this embodiment of the invention.

In addition, the combination of the adjustment of the cranks and the adjustment of the light surfaces advantageously makes it possible to adapt the crankset according to the invention to all the varieties of existing morphologies and pathologies.

In one embodiment, each of the left and right cylinders has two superimposed shells that can slide one on the other, thereby varying the surface of the lights.

The surfaces of the left and right lights can therefore be very easily adjusted. This system has the advantage of being easy to use, robust and inexpensive.

According to another aspect, the invention relates to an exercise bike intended to be immersed in a liquid, comprising a crankset according to one of the embodiments mentioned here.

An exercise bike intended to be immersed in a liquid comprising a crankset according to an embodiment of the invention has many advantages for physical medicine and rehabilitation, in particular its adaptability to all morphologies and pathologies, and regularity of its smooth pedaling cycle.

In one embodiment, the invention relates to an exercise bike intended to be immersed in a liquid, comprising a crankset according to one of the embodiments mentioned here, the use of which is not linked to its movement.

In this embodiment, the exercise bike is configured to be stationary when in use.

BRIEF DESCRIPTION OF THE FIGURES

Other advantages, aims and characteristics of the present invention will emerge from the description which follows, given for explanatory purposes and in no way limiting with regard to the appended drawings, in which:

FIG. 1 illustrates a particular embodiment of a drag device according to the invention, seen in profile,

FIG. 2 illustrates the embodiment of the drag device of FIG. 1, seen from below, the lights being open,

FIG. 3 illustrates the embodiment of the drag device of FIG. 1, seen from below, the lights being closed,

FIG. 4 illustrates another particular embodiment of a drag device according to the invention, seen in profile,

FIG. 5 illustrates the embodiment of the drag device of FIG. 4, seen from below, the lights being open,

FIG. 6 illustrates the embodiment of the drag device of FIG. 4, seen from below, the lights being closed,

FIG. 7 illustrates the embodiment of the drag device of FIG. 4, seen from three-quarters,

FIG. 8 illustrates an embodiment of an exercise bike intended to be immersed in a liquid comprising a crankset according to the invention,

- Figure 9 illustrates a particular embodiment of a crankset according to the invention.

DETAILED DESCRIPTION OF EXAMPLES OF EMBODIMENT OF THE INVENTION

We note, as of now, that the figures are not to scale.

The invention finds its place in the context of devices for sport and physical medicine and rehabilitation.

A pedal board 1 of an exercise bike 2 intended to be immersed in a liquid according to a particular embodiment of the invention is shown diagrammatically in FIG. 9. The pedal board 1 comprises two cranks 3, called "left crank" 31 and “right crank” 32 both movable in rotation about the same axis called “hub M”, the crankset 1 comprising two pedals 4, a left pedal 41 movable in rotation around an axis linked to the left crank 31, said "left axis AG", and a right pedal 42 movable in rotation about an axis linked to the right crank 32, said "right axis AD", the pedals 4 performing a circular translational movement around the hub M during pedaling , the pedals 4 comprising drag devices, respectively called "left drag device" and "right drag device", the drag devices being configured to undergo a fluid frictional force s opposing the circular translation movement of the pedals 4, the drag devices comprising portions of cylinders 5 of revolution located under the pedals 4 in the operating position, respectively called “left cylinder” 51 and “right cylinder” 52, the axis of revolution of the left cylinder 51 being coincident with the left axis AG, the axis of revolution of the right cylinder 52 being coincident with the right axis AD.

In one embodiment, each pedal 4 has a surface on which the user places his foot in the operating position, which can be substantially flat. This surface on which the user comes to put his foot is here assimilated to a plane, and called pedal plane 4.

By operating position is meant the normal pedaling position, a user having put one foot on each of the pedals 4, his muscular action causing the pedals 4 in circular translation around the hub M.

A longitudinal axis X is defined as being contained in the pedal plane 4 and being perpendicular to the axis of rotation of the pedal 4 (left axis AG or right axis AD). The longitudinal axis X is parallel to the axis of the foot, i.e. from the front to the rear of the foot (from the toes to the heel).

By length of pedal 4 is meant its average dimension along the axis X. By width of pedal 4 is meant its average dimension along its axis of rotation AD or AG.

In one embodiment, the drag device is located under the pedal 4 in the operating position. By under the pedal 4 is meant that the drag device is located in half of the space delimited by the pedal plane 4 which does not contain the user's foot in the operating position.

In a separate embodiment, the drag device is located above the pedal 4 in the operating position. By above the pedal 4, it is meant that the drag device is located in half of the space delimited by the pedal plane 4 which contains the user's foot in the operating position. In this case, a recess or opening is made in the drag device so as to allow the user to put his foot on the pedal 4.

In one embodiment, each drag device comprises an object having the shape of a portion of cylinder 5 of revolution.

In Mathematics, cylinder 5 of revolution means a surface generated by the revolution, around an axis called the axis of revolution, of a straight line parallel to this axis.

By portion of cylinder 5 of revolution is meant a part having the shape of a cylinder 5 of revolution truncated along at least two distinct planes.

In one embodiment, the cylinder portion 5 of revolution is a cylinder 5 of axis of revolution coincident with the axis of rotation AG or AD of the pedal 4, which is truncated by:

- a first plane perpendicular to the axis of rotation AG or AD of the pedal 4,

- a second plane perpendicular to the axis of rotation AG or AD of the pedal 4 and not being confused with the first plane,

- a third plane merged with the pedal plane 4.

In this embodiment, the distance between the first plane and the second plane corresponds to the width of the cylinder 5.

In another embodiment, the cylinder portion 5 of revolution is a cylinder of axis of revolution merged with the axis of rotation AG or AD of the pedal 4, which is truncated by:

- a first plane perpendicular to the axis of rotation AG or AD of the pedal 4,

- a second plane perpendicular to the axis of rotation AG or AD of the pedal 4 and not being confused with the first plane,

- a third plane comprising the axis of rotation AG or AD of the pedal 4,

- a fourth plane comprising the axis of rotation AG or AD of the pedal 4 and not being confused with the third plane.

In other separate embodiments, the cylinder portion 5 is a cylinder truncated by planes other than those mentioned here.

In one embodiment, the drag device is a solid object having substantially the shape of a portion of cylinder 5 of revolution. The drag device may nevertheless have a shape which varies slightly from that of a portion of cylinder 5 of revolution. The drag device may in particular include hooks, openings, roughness, rail, handle, allowance, chamfer, groove, tongue 73, stud, groove, collar, base, flat, or any other element which slightly differentiates its shape from that of a perfect portion of cylinder 5 of revolution.

Depending on the embodiment, the drag device may be hollow or be full. The drag device can be a simple hull. Depending on the embodiment, the drag device may or may not include material on its lateral surfaces.

By lateral surfaces of the drag device is meant the surfaces of the cylinder portion 5 combined with the first plane and with the second plane (planes perpendicular to the axis of rotation AG or AD of the pedal 4).

Figure 4, Figure 5, Figure 6 and Figure 7 illustrate an embodiment of a pedal 4 in which is installed a drag device comprising a portion of cylinder 5 of revolution. In one embodiment, the diameter of the cylinder 5 is substantially equal to the length of the pedal 4. In other embodiments, the diameter of the cylinder 5 may be less than or greater than the length of the pedal 4.

By width of the cylinder 5 is meant the maximum dimension of the cylinder 5 along the axis of rotation AD or AG of the pedal 4. In one embodiment, the width of the cylinder 5 is substantially equal to the width of the pedal 4. In other embodiments, the width of the cylinder 5 can be greater, or be less, than the width of the pedal 4.

In one embodiment, the left pedal 41 and the right pedal 42 are identical. In one embodiment, the left pedal 41 and the right pedal 42 are chiral (images of one another in a mirror). In one embodiment, the pedals 4 are symmetrical to each other.

In other separate embodiments, the drag devices have a different shape. They can have the shape of portions of cylinders 5 whose directing curve is not a circle. In this case, these are not 5-revolution cylinders. In a particular embodiment, the drag devices have the shape of cylinder portions 5 whose directing curve is an ellipse. In one embodiment, the drag devices have the shape of portions of cylinders 5 whose directing curve is a polygon. In one embodiment, the drag devices have the shape of rectangular parallelepipeds. In one embodiment, the drag devices have the shape of an ellipsoid portion.

According to the embodiment, the crankset 1 or a part of the crankset 1 can be manufactured with one or more of the following materials: stainless steel, carbon, polyethylene, or other materials.

We consider the interaction between the cylinder 5 and the liquid from the point of view of a reference linked to the cylinder 5. The pedals 4 linked to their drag device have a circular translational movement around the hub M of the crankset 1. Consequently , during a pedaling cycle, the liquid strikes cylinder 5 at all times with a non-zero speed, the speed vector of the liquid being contained in the plane perpendicular to the hub M. The direction of the speed vector of the liquid rotates around of cylinder 5. The liquid strikes cylinder 5 successively with all possible angles during a pedaling cycle.

The particular shape of the cylinder 5 has the advantage of offering a surface orthogonal to the velocity vector of the liquid which varies little whatever the angle at which the liquid strikes the cylinder 5. Like the drag force of a solid in movement in a liquid is proportional to the surface of this solid orthogonal to the speed vector of the liquid, then the drag device according to the invention makes it possible to limit the variations in the force exerted by the liquid on the pedal 4 during the cycle of pedaling. This advantageously avoids unexpected jolts and movements for the user during pedaling, which is particularly beneficial for the functional rehabilitation of the weakened, injured or operated limbs of a user.

In an embodiment illustrated in FIG. 9, the left pedal 41 and the right pedal 42 each have a strap 43 configured to hold the user's foot in place on the pedal 4.

In one embodiment, the surface of the lights 6 is adjustable.

In one embodiment, each of the left cylinder 51 and right cylinder 52 comprises two superimposed shells 7 which can slide one on the other, a shell called the inner shell 71 and a shell called the outer shell 72. The interior of the cylinders 5 is hollow, and the lateral surfaces of the cylinders 5 do not contain any material. When the bottom bracket 1 is submerged, the liquid freely penetrates inside the cylinders 5.

According to the embodiment, the inner shell 71 and the outer shell 72 can overlap completely or only partially.

In an embodiment illustrated by FIG. 4, FIG. 5 and FIG. 6, the outer shell 72 slides relative to the inner shell 71 according to a speed vector always contained in a plane defined as: perpendicular to the axis of rotation AD or AG of the pedal 4.

In a separate embodiment illustrated by FIG. 1, FIG. 2 and FIG. 3, the outer shell 72 slides relative to the inner shell 71 according to a speed vector parallel to the axis of rotation AD or AG of the pedal 4.

In one embodiment, for each of the cylinders 5, the outer shell 72 and the inner shell 71 are both pierced with at least one through hole.

In one embodiment, for each of the cylinders 5, the through holes drilled in the outer shell 72 and the through holes drilled in the inner shell 71 are arranged so that they may or may not be opposite one another, depending on the position relative sliding of the outer shell 72 and the inner shell 71.

In other words, in this embodiment, for each of the cylinders 5, the sliding of the outer shell 72 relative to the inner shell 71 causes the cylinder 5 to pass from one of the following states to the other:

the holes in the outer shell 72 are opposite the holes in the inner shell 71,

the holes in the outer shell 72 are partially opposite the holes in the inner shell 71,

the holes in the outer shell 72 are not opposite the holes in the inner shell 71.

When the holes in the outer shell 72 and the holes in the inner shell 71 are at least partially opposite one another, the liquid can pass through the cylinder 5. This is then called light 6, respectively called light 6 left for the cylinder left 51, and light 6 right for right cylinder 52.

The fact that the liquid can pass through the openings 6 of the cylinder 5 reduces the friction surface of the cylinder 5 during the circular translational movement. So the force opposed by the liquid to the pedaling movement is a function of the opening state of the lights 6 of the cylinder 5.

By sliding one on the other the inner shell 71 and the outer shell 72 of the cylinder 5, the surface of the lights 6 is varied, thereby varying the friction force opposed by the liquid to the pedaling movement. In other words, sliding the two shells 7 one on the other allows you to adjust the pedaling difficulty. This possibility of adjustment is an important advantage of the crankset 1 according to the invention. For a sportsman in good shape we can slide the shells 7 so as to close the lights 6, and the effort required to pedal will be maximum. For a weaker user, the shells 7 can be slid to partially or completely open the lights 6, and the effort required to pedal will be lower, adapted to the physical condition of the user.

In one embodiment, the cylinders 5 are both pierced with at least one through hole, respectively called "light 6 left" and "light 6 right".

Depending on the embodiment, the left lumen 6 may include one or more through holes of any possible shape.

Depending on the embodiment, the right lumen 6 may include one or more through holes, of any possible shape.

In the embodiment illustrated in FIG. 1, FIG. 2 and FIG. 3, the openings 6 of a cylinder 5 consist of two rows of through holes, all the through holes of a row being aligned with the surface of the cylinder 5 along a plane perpendicular to the axis of rotation AD or AG of the pedal 4. The through holes have an oblong shape, their greatest length being aligned on this same plane perpendicular to the axis of rotation AD or AG of the pedal 4.

In the embodiment illustrated by FIG. 4, FIG. 5 and FIG. 6, the openings 6 of a cylinder 5 consist of several rows of through holes, all the through holes of a row being aligned with the surface of the cylinder 5 along lines parallel to the axis of rotation AD or AG of the pedal 4. The through holes have an oblong shape, their greatest length being aligned on these same lines parallel to the axis of rotation AD or AG of the pedal 4.

In other embodiments, the openings 6 of a cylinder 5 may include one or more through holes having all the possible shapes and surfaces.

In one embodiment, for each of the cylinders 5, one of the shells 7 has a solid and projecting tongue 73. This tongue 73 is configured to be easily grasped by a user or a trainer, in order to manually slide one over the other the inner shell 71 and the outer shell 72. In one embodiment, the tongue 73 is located on the outer shell 72.

In one embodiment, the surface of the left light 6 is adjustable independently of the surface of the right light 6. For this, the user just has to slide the outer shell 72 and the inner shell 71 of the left cylinder 51 one on the other independently of the outer shell 72 and the inner shell 71 of the right cylinder 52.

This has the important advantage of allowing adaptation of the pedal unit 1 according to the invention to asymmetrical human morphologies. For example, a person who has been operated on with only one leg, therefore having a very weak limb and a healthy second limb can independently adjust the surface of the lumen 6 of the left cylinder 51 and the lumen surface 6 of the right cylinder 52. Consequently, the friction force exerted by the liquid, and therefore the difficulty of pedaling will not be identical for the two members during pedaling.

In one embodiment, the cranks 3 are of adjustable lengths.

The length of a crank 3 means the distance between the hub M and the axis of the pedal 4 linked to this crank 3 (the left axis AG or the right axis AD).

The adjustable length of the cranks 3 makes it possible to adapt the crankset 1 to all morphologies and pathologies, which has an obvious advantage for the exercise of people in physical medicine and rehabilitation. In addition, the lengths of the left crank 31 and right crank 32 can be adjusted independently of each other, which has an advantage for the rehabilitation of people whose one limb is weaker than the other, or whose one member is shorter than the other.

In an embodiment illustrated in FIG. 9, each of the cranks 3 is pierced with several through holes at different distances from the hub M. The axis of rotation AD or AG of the pedal 4 is fixed to the crank 3 by a removable mechanism . This removable mechanism can slide along the crank 3, or be fixed on one of the holes made in the crank 3. Depending on the distance to the hub M from the hole to which said removable mechanism is fixed, the distance between the hub M and the axis rotation AG or AD of pedal 4 can be adjusted. Thus, the length of the hub M is adjustable.

According to another aspect, the invention relates to an exercise bike 2 intended to be immersed in a liquid, comprising a crankset 1 according to one of the embodiments mentioned here.

In one embodiment, the exercise bike 2 has a saddle 81. In one embodiment, the exercise bike 2 does not have a saddle 81. In one embodiment, the exercise bike 2 has a or more handles 82 which the user can hold. In one embodiment, the exercise bike 2 is a recumbent bike. A recumbent bike 2 is configured to allow a user to pedal while having the trunk or part of the trunk of his body which rests on a suitable support. This type of recumbent exercise bike 2 is particularly suitable for the rehabilitation of people who have had hip surgery. In one embodiment, the exercise bike 2 is configured so that the user pedals with his lower limbs (legs, feet). In another embodiment, the exercise bike 2 is configured so that the user pedals with his upper limbs (arms, hands). In this case, the crankset 1 may include, at the level of the pedals 4, organs which can be grasped by the hands.

In one embodiment, the invention relates to an exercise bike 2 intended to be immersed in a liquid comprising a pedal board 1 according to one of the embodiments mentioned here, characterized in that its use is not linked to its displacement.

In one embodiment, the exercise bike 2 is configured to be used stationary. In one embodiment, the exercise bike 2 has a structure 83 which keeps the user and the crankset 1 in a position suitable for pedaling.

According to the embodiment, one or more parts of the exercise bike 2 can be manufactured with one or more of the following materials: stainless steel, carbon, polyethylene.

Claims (8)

1 - Crankset (1) of an exercise bike (2) intended to be immersed in a liquid, comprising two cranks (3), called "left crank" (31) and "right crank" (32) both movable in rotation about the same axis called "hub M", the crankset (1) comprising two pedals (4), a left pedal (41) movable in rotation around an axis linked to the left crank (31), said "Left axis AG", and a right pedal (42) movable in rotation about an axis linked to the right crank (32), called "right axis AD", the pedals (4) performing a circular translation movement around the hub M when pedaling, characterized in that the pedals (4) comprise drag devices, respectively called "left drag device" and "right drag device", the drag devices being configured to undergo a fluid friction force opposing the circular translational movement of the pedals (4), the drag devices comprising cylinders portions (5) of revolution located under the pedals (4) in the operating position, respectively called "left cylinder" (51) and "right cylinder" (52), the axis of revolution of the left cylinder (51) being coincident with the left axis AG, the axis of revolution of the right cylinder (52) being coincident with the right axis AD. 2 - Crankset (1) according to claim 1, characterized in that the cranks (3) are of adjustable lengths. 3 - Crankset (1) according to one of claims 1 to 2, characterized in that the left cylinders (51) and right cylinder (52) are both pierced with at least one through hole, respectively called "light ( 6) left ”and“ light (6) right ”. 4 - Crankset (1) according to claim 3, characterized in that the surface of the lights (6) is adjustable. 5 - Crankset (1) according to claim 4, characterized in that the surface of the light ( 6) left is adjustable independently of the surface of the light (6) right. 5 6 - Crankset (1) according to one of claims 3 to 5, characterized in that each of the left cylinder (51) and right cylinder (52) has two shells ( 7) superimposed which can slide one on the other, thus varying the surface of the lights (6). 10 7 - Exercise bike (2) intended to be immersed in a liquid, comprising a pedal board (1) according to one of claims 1 to 6. 8 - Exercise bike (2) intended to be immersed in a liquid according to claim (7), characterized in that its use is not linked to its 15 displacement. 1/4 FiflJÎ 2/4 4/4