WO2007141760A1

WO2007141760A1 - Isokinetic exercise device

Info

Publication number: WO2007141760A1
Application number: PCT/IB2007/052158
Authority: WO
Inventors: Thomas Philippus Liebenberg
Original assignee: Genesis Fitness (Pty) Ltd
Priority date: 2006-06-08
Filing date: 2007-06-07
Publication date: 2007-12-13

Abstract

The invention concerns an isokinetic exercise device. The device (10) includes a drive member (22) and an accommodating resistance means (38) providing accommodating resistance to movement of the drive member. A drive mechanism (12, 16) is operated by the effort of a user of the exercise device to drive the drive member with a constant leverage against the accommodating resistance provided by the accommodating resistance means. The accommodating resistance means is arranged to control the speed of movement of the drive member to a set velocity, thereby to bring about isokinetic resistance to operation of the drive mechanism.

Description

ISOKINETIC EXERCISE DEVICE

BACKGROUND TO THE INVENTION

THIS invention relates to an isokinetic exercise device.

The essence of isokinetic exercise is to allow for maximal muscle contraction throughout the complete range of motion of a particular joint. This is facilitated through an accommodating resistance and a set velocity of movement. It has been established that isokinetic exercise can lead to substantial increases in strength gain when compared to isometric and isotonic exercises where there is no control over the speed at which the exercise is performed and the relevant resistance remains constant throughout the duration of the exercise. It has for instance been shown that strength gain with isokinetic exercise is more rapid than with simple weight lifting, an example of isotonic exercise, where there is no control over the rate at which the weight is lifted.

A further advantage of isokinetic exercise is that it is a much safer exercise modality when compared isotonic exercise.

Existing isokinetic exercise devices tend to be bulky, complicated and expensive and hence not suitable for use in general exercise applications in public gymnasiums or sports training facilities. Typically the resistance in existing isokinetic exercises are generated with electromagnetic or hydraulic resistance devices.

In most known isokinetic exercise devices using hydraulically generated resistance, the exercise is performed with leverage against a resistance. In many cases, the user's effort is applied, with leverage, against a resistance device which is itself mounted pivotally. As the exercise movement takes place, the resistance device pivots and there is accordingly a variation of the leverage which is applied.

The user may for instance perform leg or arm presses against a lever at a point away from the pivot point of the lever. The lever acts through a pivotal connection against a resistance device which itself undergoes pivotal movement as the lever is pivoted by the force applied by the user. In such devices the various pivotal movements cause the effective lever arm through which the user is acting to vary, resulting in a variation of the speed at which the exercising movement is carried out if the exercising effort is continued.

SUMMARY OF THE INVENTION

An isokinetic exercise device according to the invention comprises a drive member, an accommodating resistance means providing accommodating resistance to movement of the drive member and a drive mechanism which is operable, by the effort of a user of the exercise device, to drive the drive member with constant leverage against the accommodating resistance provided by the accommodating resistance means, the accommodating resistance means being arranged to control the speed of movement of the drive member to a set velocity, thereby to bring about isokinetic resistance to operation of the drive mechanism.

In preferred embodiments, the drive mechanism comprises a rotatable member and an operating member arranged to be moved by the effort of the user to cause rotation of the rotatable member with a constant leverage. It is also preferred that the drive member is arranged to move linearly and the rotatable member is arranged to cause linear movement of the drive member.

In some embodiments, the rotatable member is a toothed pinion, the operating member is a force application arm fixed to and extending radially from the pinion and the drive member is a straight, elongate toothed rack with which the pinion meshes and which is guided for linear movement in its longitudinal direction.

In other embodiments, the rotatable member is a sprocket, the operating member is a force application arm fixed to and extending radially from the sprocket and the drive member is a chain with which the sprocket is engaged.

In yet other embodiments, the rotatable member is a toothed pinion, the operating member is a toothed rack with which the pinion meshes and the drive member is a further, straight, elongate, toothed rack arranged to be driven linearly by rotation of the pinion and guided for movement in its longitudinal direction. In this case, the drive mechanism may comprise a further pinion meshing with the first-mentioned pinion and with the further toothed rack.

Typically, the resistance means comprises a piston to which the drive member is connected, an hydraulic cylinder in which the piston is moved by movement of the drive means such that hydraulic fluid is expelled from one side of the cylinder, and flow control means for controlling the rate at which the hydraulic fluid can be expelled from that one side of the cylinder in order to control the velocity of the piston and drive member and hence the velocity at which the drive mechanism can be operated by the user. The flow control means may comprise a flow control valve including a flow restricting orifice, which may be adjustable.

The device may include sensors for monitoring the speed of operation of the drive mechanism and/or the effort applied to the drive mechanism by the user and a computer, responsive to the sensor(s), for controlling the operation of the flow control valve.

Preferably the hydraulic cylinder is arranged to operate in a closed circuit, the device including an hydraulic line extending from the cylinder on one -A-

side of the piston to the cylinder on the other side of the piston to convey hydraulic fluid from one side of the piston to the other, the flow control means being arranged in the hydraulic line.

There may be two hydraulic lines extending from the cylinder on one side of the piston to the cylinder on the other side of the piston to convey hydraulic fluid from one side of the piston to the other and flow control means in both lines to control the flow in opposite directions.

BRIEF DESRIPTION OF THE DRAWINGS

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings.

In the drawings, Figures 1 to 4 diagrammatically illustrate isokinetic exercise devices according to different embodiments of the invention.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The isokinetic exercise device 10 illustrated in Figure 1 includes a rotatable member in the form of a toothed pinion 12 which is arranged to rotate about a fixed axis 14. An operating member in the form of a radially oriented force application arm 16 is connected to the pinion 12 at the axis 14 so that, as the arm is swung back and forth as indicated by the arrows 18, 20, the pinion is caused to rotate.

The pinion 12 meshes with a drive member in the form of an elongate, toothed rack 22 which is guided for linear, longitudinal movement as indicated by the arrows 24, 26. The rack is connected by connectors 28, 30 to piston rods 32, 34 carrying a central piston 36 in an hydraulic cylinder 38. The piston 36 is shown in Figure 1 in a central position, midway between the ends of the cylinder. An hydraulic line 40 extends through a flow control valve 42 from the cylinder space 44 on one side of the piston to the cylinder space 46 on the opposite side of the piston. Both piston spaces are filled with hydraulic fluid. It is pointed out that with the piston 36 located in its central position inside the hydraulic cylinder 38, the volume of the cylinder space 44 will equal that of the cylinder space 46.

In use, a person wishing to perform isokinetic exercise applies effort to the drive mechanism, in this case consisting of the force application arm 16 and pinion 12, in order to swing the arm 16 in the direction of the arrow 18. The exercise may, for instance, be a bicep curl exercise in which the user grips a handle at the end of the arm 16 with his forearm outstretched and then contracts his bicep muscle in order to flex the elbow joint, thereby swinging the arm 16 in the direction 18.

The effort applied to the drive mechanism results in rotation of the pinion 12 about the axis 14. This in turn causes the rack 22 to move linearly and in the direction of the arrow 24. Through the connectors 28, 30 and the piston rods 32, 34, the piston 36 is driven to the right in Figure 1. Hydraulic fluid is driven from the piston space 44 through the line 40 and valve 42 into the space 46.

The valve 42 includes a flow restricting orifice through which the fluid passes and which accordingly provides accommodating resistance to the movement of the piston and hence to the rotation of the pinion 12. Thus the piston and cylinder seen in Figure 1 constitute an accommodating resistance means to resist the movement of the rack 22 and hence to resist the rotation of the pinion 12 and pivotal movement of the force application arm 16.

The valve may be of a type which is mechanically adjustable in order to vary the size of the orifice. Such adjustment allows the valve orifice to be set such that the maximum flow rate of hydraulic fluid through the orifice corresponds to a predetermined, maximum linear piston speed, corresponding in turn to a maximum rotational velocity of the pinion, i.e. a set maximum speed at which the user can raise his forearm in the example of a bicep curl exercise. In other words, the speed at which the user can flex his elbow is limited to the predetermined, maximum value resulting from having the accommodating resistance, even if he attempts to increase the speed of movement by increasing the applied effort. The device. seen in Figure 1 accordingly brings about isokinetic resistance to the effort applied by the user.

An important feature of the device seen in Figure 1 is the fact that the mechanical advantage with which the user applies effort to swing the force application arm 16 remains constant throughout the movement. This is attributable to the fact that the lever arm on which the user acts, i.e. the . distance from his hand on the force application arm 16 to the axis 14, remains constant, so the leverage available to the user is constant, and to the fact that the drive member i.e. the rack 22 in this embodiment, moves linearly in a constant, longitudinal direction.

A force application arm of fixed length may be too short or too long to suit the exercise being performed or the physical size of the user. For this reason the invention envisages embodiments in which the length of the arm 16 may be varied to suit different persons or to suit different exercises. It will however be recognised that a variation in the length of the arm will require an adjustment to the setting of the valve 42 in order to achieve the desired isokinetic resistance.

In more sophisticated versions of the device of Figure 1 , the valve 42 may be a solenoid or other type of valve which can be controlled electronically. Such versions may include a rotational speed sensor which monitors the angular speed of the pinion 12 and/or a force sensor which monitors the effort applied to the arm 16, and a computer which receives the output of the sensor(s) in order to control the setting of the valve 42 in accordance with software with which it is programmed. In the device of Figure 1 , the valve orifice restricts fluid flow equally in both directions, so the user must apply a similar effort in the opposite direction in order to return the piston to the initial, central position. In the above example of a bicep curl exercise where the user initially contracts his bicep muscle in order to flex his elbow, he must then apply a pushing force in order to extend his elbow and swing the arm 16 in the opposite direction, thereby to rotate the pinion 12 in a sense to move the rack 22 in the direction of the arrow 26.

In other versions, the valve may be designed to restrict flow in one direction but not in the other. In such versions only a small amount of effort is required to return the piston to the central position, and the device may include a counterweight or spring arrangement to achieve this, so that the force application arm 16 is returned to the start position in readiness for a repetition of the exercise.

Instead of a single line 40 between the spaces 44 and 46, there may be two lines, each controlled by an adjustable, unidirectional flow control orifice for controlling fluid flow in one direction only. The valves may be set differently from one another, thereby varying the isokinetic resistance to exercise in opposite directions.

The gear ratio between the pinion 12 and rack 22 is constant. Thus the rack 22 moves a set distance for a given angle of rotation of the pinion, i.e. a given rotation of the arm 16. By varying the number of pinion teeth it is possible to vary the longitudinal movement undergone by the rack for a given angular rotation. The parameters may for instance be set such that a relatively large angular movement of the arm 16 generates only a relatively small longitudinal movement of the piston, making it possible to limit the length of the cylinder. In this way, the device and hence the exercising apparatus in which the device is used may be kept to a compact size. Figure 2 illustrates another embodiment in which the rack 22 is aligned longitudinally with the piston rods 32, 34. Although more compact in a transverse sense, this embodiment occupies a greater length.

It is recognised that in certain exercises, the user must extend or contract a limb linearly and that such extension or contraction may take place over a fairly substantial distance. An example might be a leg press exercise where the leg may be extended linearly for a metre or more.

Figure 3 illustrates an embodiment suitable for extended linear movement. This embodiment includes a first rack 50 which is pushed (or pulled linearly) as indicated by the arrows 53, 54. The rack meshes with a first pinion 56 which has a fixed rotational axis and which meshes with a second pinion 60, also with a fixed rotational axis. The second pinion corresponds in function to the pinion 12 of the first embodiment. It meshes with a rack 62, corresponding to the rack 22, that drives a piston 64 through an arrangement of connectors and piston rods similar to those seen in Figure 1. In this case, it is possible to vary the rack/pinion ratios in order to convert a relatively large linear movement of the first rack to a relatively small linear movement of the second rack, which in turn makes it possible to limit the length of at least the second rack and the cylinder.

It would also be possible to interpose further gears or sprockets between the pinions 56 and 60 in order to allow for further variation in the ratio of the extent of the linear motion undergone by the user and that undergone by the piston.

Figure 4 illustrates an embodiment in which a chain 61 passes around sprockets 63, 64 with its ends connected to piston rods 66, 68 carrying a piston 70 in a cylinder 72. The sprocket 63 corresponds in function to the pinion 12 and has a force application arm 74, corresponding to the arm 16, connected to it. It will be understood that in this type of device, the sprocket and chain take the place of the pinion and rack of the earlier embodiments. This can be advantageous from the point of view of cost, weight and space saving.

In each of the embodiments of Figures 2 to 4, as in the embodiment of Figure 1 , the mechanical advantage afforded to the user remains constant, allowing the desired isokinetic exercise to take place. This feature is considered advantageous compared to prior devices in which the mechanical advantage varies as the effective lever arm varies, thereby and accordingly leads to an exercise which is not truly isokinetic in nature.

An added advantage of the illustrated devices is that the fact that the hydraulic cylinder operates in a closed circuit, with a constant volume of hydraulic fluid. The fluid present in the cylinder is merely driven from one side of the cylinder to the other as the piston is reciprocated. Because the system operates in a closed circuit, it is possible to orientate the hydraulic components at any suitable angle to suit the nature of the particular exercising apparatus of which the device forms part. It is however within the scope of the invention for the opposite sides of the cylinder to operate in open circuit with appropriate, external reservoirs to receive fluid expelled from the cylinder as the piston moves.

Although specific reference has been made in the description above to the use of the isokinetic exercise device as a fitness training device, it will be readily appreciated that it could also be used for diagnostic or rehabilitation purposes. A person may, for example, operate the isokinetic exercise device while certain diagnostic observations are made by a physician.

Claims

1.

An isokinetic exercise device comprising a drive member, an accommodating resistance means providing accommodating resistance to movement of the drive member and a drive mechanism which is operable, by the effort of a user of the exercise device, to drive the drive member with constant leverage against the accommodating resistance provided by the accommodating resistance means, the accommodating resistance means being arranged to control the speed of movement of the drive member to a set velocity, thereby to bring about isokinetic resistance to operation of the drive mechanism.

2.

An isokinetic exercise device according to claim 1 wherein the drive mechanism comprises a rotatable member and an operating member arranged to be moved by the effort of the user to cause rotation of the rotatable member with a constant leverage.

3.

An isokinetic exercise device according to claim 2 wherein the drive member is arranged to move linearly and the rotatable member is arranged to cause linear movement of the drive member.

4.

An isokinetic exercise device according to claim 3 wherein the rotatable member is a toothed pinion, the operating member is a force application arm fixed to and extending radially from the pinion and the drive member is a straight, elongate toothed rack with which the pinion meshes and which is guided for linear movement in its longitudinal direction.

5.

An isokinetic exercise device according to claim 3 wherein the rotatable member is a sprocket, the operating member is a force application arm fixed to and extending radially from the sprocket and the drive member is a chain with which the sprocket is engaged.

6.

An isokinetic exercise device according to claim 3 wherein the rotatable member is a toothed pinion, the operating member is a toothed rack with which the pinion meshes and the drive member is a further, straight, elongate, toothed rack arranged to be driven linearly by rotation of the pinion and guided for movement in its longitudinal direction.

7.

An isokinetic exercise device according to claim 6 wherein the drive mechanism comprises a further pinion meshing with the first-mentioned pinion and with the further toothed rack.

8.

An isokinetic exercise device according to any one of the preceding claims wherein the accommodating resistance means comprises a piston to which the drive member is connected, an hydraulic cylinder in which the piston is moved by movement of the drive means such that hydraulic fluid is expelled from one side of the cylinder, and flow control means for controlling the rate at which the hydraulic fluid can be expelled from that one side of the cylinder in order to control the velocity of the piston and drive member and hence the velocity at which the drive mechanism can be operated by the user.

9.

An isokinetic exercise device according to claim 8 wherein the flow control means comprises a flow control valve including a flow restricting orifice.

10.

An isokinetic exercise device according to claim 9 wherein the flow restricting orifice is adjustable.

11.

An isokinetic exercise device according to claim 9 wherein the device comprises sensor means for monitoring the speed of operation of the drive mechanism and/or the effort applied to the drive mechanism by the user and a computer, responsive to the sensor(s), for controlling the operation of the flow control valve.

12.

An isokinetic exercise device according to any one of claims 8 to 11 wherein the hydraulic cylinder is arranged to operate in a closed circuit, the device including an hydraulic line extending from the cylinder on one side of the piston to the cylinder on the other side of the piston to convey hydraulic fluid from one side of the piston to the other, the flow control means being arranged in the hydraulic line.

13.

An isokinetic exercise device according to claim 12 comprising two hydraulic lines extending from the cylinder on one side of the piston to the cylinder on the other side of the piston to convey hydraulic fluid from one side of the piston to the other and flow control means in both lines to control the flow in opposite directions.