US20040254051A1

US20040254051A1 - Arm and leg erxercise machine

Info

Publication number: US20040254051A1
Application number: US10/867,552
Authority: US
Inventors: John Harrison
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-06-16
Filing date: 2004-06-11
Publication date: 2004-12-16
Also published as: GB0413271D0; GB2403431B; GB0313889D0; GB2403431A

Abstract

An exercise machine for exercising the arms and legs with a seat height adjustable to a lower and a upper position, in the lower position a preacher rest is also provided which places the elbow joint of the user when sitting on the seat in line with a pivot. Members are attached to the pivot which the user rotates to exercise his arms. The seat in the upper position places the knee joint of the user, when seated on the seat with the preacher rest removed, in line with the pivot members are then rotated about the pivot by the user bending his legs about the knee. Resistance to the exercise is provided rotation of the pivot.

Description

BACKGROUND OF THE INVENTION

Exercise machines for the legs and arms usually hold the upper part of the limb, that is, between the hip and the knee and the elbow and the shoulder, in a fixed position while the lower part of the limb, between the knee and the ankle and the elbow and the wrist are rotated about the knee joint or the elbow. Leg exercises are usually performed seated. A pivot is usually in line with the knee joint of the person exercising. An arm usually connects the ankle of the user to a pivot. For leg straightening exercises or leg extensions the upper leg is held in position by the seat, which prevents the upper leg from moving downwards and away from being in line with the pivot as the lower leg is raised against resistance. The resistance is usually provided through the pivot. This movement exercises the muscles on the front of the leg above the knee. Leg bending exercises or leg curls are often also performed seated with the leg starting straight and being bent against a resistance. A fixed support is usually placed across the legs just above the knee which prevents the upper leg of the user lifting when the ankle is lowered, and keeps the knee in line with the pivot. This movement exercise the muscles on the back of the legs above the knee.

Arm bending exercises are also often performed seated with the user leaning forwards and leaning his chest on a rest with the upper arms resting on a sloping rest in front of the user with the elbow joint in line with a pivot through which resistance to the exercise is provided. An arm also connects the hand or wrist of the user to a pivot. The sloping rest prevents the upper arm dropping as the wrist and forearm are raised against a resistance. This exercise is sometimes called a preacher curl. Arm straightening exercises can also be carried out with the upper arm resting to the same rest and using the same pivot and, starting with the arms bent, straightening them against a resistance. The same rest can be used for arm curls because the reaction to the arm being straightened is to push upwards through the upper arm to the shoulder of the user and the weight of the user leaning forwards holds the elbow in one position.

To provide resistance to the exercise a pivot is usually in line with the knee joint or elbow of the user with an arm extending from the pivot the the ankle or hand of the user for the user to rest his ankle or to hold on to. A further arm usually extends from the pivot with a weight placed on its end. The user then bends or straightens his leg or arm lifting the weight and exercising the muscles which straighten or bend the leg or arm.

Machines are in use which allow arm bending and leg straightening exercises to be performed on the same machine. This machine has two pivots, one below the other. The lower pivot is positioned to be in line with the knee joint of the user when in the seated position for the leg straightening exercise. The higher pivot is for the arm bending exercise performed with a preacher style rest. This machine requires two pivots, each with an arm attached to it for the user to move when exercising, and two means of providing resistance to the exercise attached to the pivot such as a weighted arm or pulling a cable which is passed around a number of pulleys to lift a weight. This machine has two pivots because if arm exercises were attempted on the same pivot as legs, then to keep the elbow in line with the pivot the user would have to lean too far forwards, making the exercise uncomfortable or even damaging.

Machines are in use which allow arm bending and arm straightening exercises to be performed on the same machine. Here the pivoted arm with the weight attached to it can be rotated independently to the arm which the user rotates and locked in a position so that resistance can be provided in either direction of rotation by lifting a weight against gravity. Similar machines are in use which allow both leg straightening and leg bending exercises to be performed on the same machine.

BRIEF SUMMARY OF THE INVENTION

A machine for exercising the legs and arms with resistance provided in at least one direction of rotation, with a pivot to stabilize the exercise, and with a seat adjustable to at least two heights, one height being such that the elbow joint of the user is approximately in line with the pivot, and another height being such that the knee joint of the user is approximately in line with the pivot.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective of an embodiment of the invention in the configuration for arm curls. [0007]
FIG. 2 shows an enlargement of a part of the machine shown in FIG. 1. [0008]
FIG. 3 shows a perspective of part of the machine with an attachment fitted for leg extensions. [0009]
FIG. 4 shows a side elevation of the machine in the configuration for arm curls. [0010]
FIG. 5 shows a perspective of the machine in the configuration for arm extensions. [0011]
FIG. 6 shows a side elevation of the machine in the configuration for arm extensions. [0012]
FIG. 7 shows a perspective of the machine in the configuration for leg extensions. [0013]
FIG. 8 shows a side elevation of the machine in the configuration for leg extensions. [0014]
FIG. 9 shows a perspective of part of the machine with an attachment for leg curls. [0015]
FIG. 10 shows a side elevation of the machine in the configuration for leg curls. [0016]
FIG. 11 shows a perspective of the machine in the configuration for leg curls. [0017]
FIG. 12 shows an alternative method of providing resistance to leg extensions and arm curls. [0018]
FIG. 13 shows an alternative method of providing resistance for leg curls and arm extensions. [0019]

DETAILED DESCRIPTION

Referring to FIG. 1 the machine comprises a [0020] square tube 2 with adjustable square tube 4 slid inside it. The bottom end of square tube 2 has a hole in its side 6 and square tube 4 has at least two holes in its side 8 10. Hole 8 is above hole 10. A pin 12 is in both holes 6, in square tube 2, and hole 8 in adjustable square tube 4. Attached to the top of adjustable tube 4 is seat 14. Two members 16 connect square tube 2 to vertical member 18. Horizontal member 20 is connected to the bottom end of vertical member 18 and rests on the floor. Hollow shaft 22 pivots in vertical member 18. Fixed to one end of hollow shaft 22 is weight arm 24 with a weight 26 attached to its end. Weight arm 24 rests on one of stops 28, 30 which are the ends of stop member 32 which is fixed to vertical member 18. Stops 28, 30 stop the weight arm at approximately 60 degrees to the horizontal.
Referring to FIGS. 1 and 2. [0021] Circular plate 34 is fixed to the opposite end of hollow shaft 22 to weight arm 24 and has a hole 36 in its center in line with the hole in hollow shaft 22. Circular plate 34 has a number of holes 38 around and close to its outer edge, each hole the same distance from the center hole. Rectangular plate 40 has two holes. One hole, 42, lines up with the hole in center of circular plate 34 and the other hole 44 lines up with the holes around the edge of circular plate 34. A pin 46 in hole 42 in rectangular plate 40 is fixed to rectangular plate 40 and passed through center hole 36 in circular plate 34 and the center of hollow shaft 22. A small plate 48 is fixed to the end of pin 46. This keeps rectangular place 40 close to circular plate 34. A removable pin 50 can be placed in one of holes 38 and hole 44 to link circular plate 34 and rectangular plate 40 together. Fixed to rectangular plate 40 in line with hollow shaft 22 is member 52 fixed to the other end of member 52 is arm 54. Arm 54 has a number of holes 56 along its length.
Shown in FIGS. 1, 2 [0022] vertical member 18 is fixed to plate 58 to which is fixed square tube socket 60 with a hole 62 in its top. Plate 58 provides a space for circular plate 34 to pass and rotate freely between vertical member 18 and the end of square tube socket 60. Arm rest support member 70 has end 64 is slightly smaller than square tube socket 60 and slides into square square tube socket 60. The top of the end of arm rest support member 64 has a hole in it 66. When the end arm rest support member 64 is slid into square tube socket 60 holes 62, 66 line up and a pin 68 is placed in them to hold the arm rest support member in the square tube socket. Fixed to arm rest support member 70 is arm rest 72 which supports the upper arms and chest rest 74 which supports the chest. The arm rest 72 and chest rest 74 may be referred to as a preacher bench.
A [0023] leg support 76 shown in FIG. 3 comprises a member 78 which fits in square tube socket 60, vertical spacing member 80, leg rest support member 82 and leg rest 84. Vertical spacing member 80 is fixed to one side of member 78, a hole 86, similar to hole 62 in the end of arm rest support member 64, is in the same side of member 78 as the vertical spacing member, and a further hole 88 is in the opposite side of member 78 to the vertical spacing member.
Referring to FIG. 1 a [0024] collar 90 slides over arm 54 and has a handle 92 fixed to it. Arm 54 has a number of holes 56 along its length which line up with hole 94 in collar 90. By placing a pin 98 in holes 56, 94 collar 90 and handle 92 can be fixed in different positions along the length of arm 54.
The operation of the machine will now be described with reference to FIGS. 1, 4. Arm exercises are performed with the seat is in the lower position with pin [0025] 12 in hole 6 in square tube 2 and hole 8 in adjustable square tube 4. For arm bending exercises weight arm 24 is placed so as to rest against stop 28. Arm 54 is then rotated until handle 92 is in line with arm rest 72, position 96 FIG. 1. In this position the hole in rectangular plate 40 lines up with one of holes 38 close to the outer edge of circular plate 34. Pin 50 is then placed through both these holes. The user sits on seat 14 and leans forward until his chest rests on chest rest 74 and places his arms on arm rest 72. The user then tests if the distance between his elbow and handle 92 is the same as the distance between the handle and a line through hollow shaft 22. If the elbow is not in line with hollow shaft 22, the pivot, the exercise position will be eccentric and incorrect. To correct this the user removes pin 98 and slides collar 90 along arm 54 until the distance form handle 92 to the elbow of the user is the same as the distance from the handle to the center of hollow shaft 22. The collar is then held in place on arm 54 with pin 98 in the hole in collar 90 and one of the holes 56 in arm 54.
The machine is then ready for use and the user grasps handle [0026] 92 and bends his arms. This lifts arm 54 which rotates member 52 and rectangular plate 40. Pin 50 connects rectangular plate 40 and circular plate 34 by one of holes 38 and hole 44 so that they rotate together. Circular plate 34 is fixed to hollow shaft 22 and rotates with hollow shaft 22 and weight arm 24 lifting weight 26 and providing resistance to the exercise. It is preferable that hollow shaft 22 passes through vertical member 18 and is mounted on bearings for easy and free rotation. Horizontal member 18 provides stability to the machine. With the machine positioned as in FIG. 4 an arm bending exercise would be in a clockwise direction.
To perform arm straightening exercises, the machine is altered to the configuration shown in FIG. 5, 6. First pin [0027] 50 holding the rectangular plate to the circular plate is removed. This allows rectangular plate 40 and circular plate 34 to rotate independently with pin 46 rotating inside hollow shaft 22. Rectangular plate 40 and arm 54 rotate with rectangular plate 40 and pin 46. Hollow shaft 22 and weight arm 24 rotate with circular plate 34. With pin 50 removed weight arm 24 is rotated so as to rest against stop 30. Arm 54 is rotated to position 100 FIGS. 5, 6 and pin 50 placed in the holes which now line up in the rectangular and circular plates. The user then sits in the same position as for arm curls and grasps handle 92. In this position the arms are fully bent and as they are straightened resistance is provided by the weight arm being lifted off stop 30 and rotated in the opposite direction to that for arm curls, which would be an anti clockwise direction with the machine positioned as shown in FIG. 6. The position of collar 90 on arm 54 should remain the same as for arm curls.
During arm exercises, the user sits on the seat and leans on [0028] chest rest 74 and, with his arms stabilized by arm rest 72, hollow shaft 22, which is the pivot of the machine, is just above arm rest 72 and in line with the elbow joint of the user. This provides a safe and comfortable exercise position, and is shown in FIGS. 4,6. Collar 90 which can be fixed at a number of positions along the length of arm 54 is to accommodate differing lengths of arm of different users, whilst keeping their elbow joint in line with the pivot of the machine. The square cross section of square tube socket 60 and the end of arm rest support member 64 keep the arm and chest rest fixed on one position and prevent it rotating which keeps the rests stable.
To perform leg exercises the seat is raised to position [0029] 102 shown in FIGS. 3, 7, 8, 9 10. This is achieved by removing pin 12 from hole 6 in square tube 2 and hole 8 in adjustable square tube 4. The seat, which is fixed to the top of adjustable square tube 4, is lifted. This slides adjustable tube 4 through square tube 2. Lifting of the seat is continued until hole 10 in adjustable square tube 4 is in line with hole 6 in square tube 4. Then pin 12 is placed in holes 6 and 10. This holds the seat in the raised position. The seat is lifted approximately 200 millimeters between its position for arm exercises and its position for leg exercises.
[0030] Arm rest 72 and chest rests 74 are removed from the machine by removing pin 68 from hole 62 in the square tube socket 60 and hole 66 in the end of arm rest support member 64. Arm rest support member 70 is then slid out of square tube socket 60.
Then to perform leg extensions or leg straightening exercises, shown in FIGS. 3, 7, [0031] 8 member 78 of the leg support 76 is placed in square tube socket 60. FIG. 3 has part of the machine removed to show the square tube socket and the leg support. Hole 88 is lined up with hole 62 in the square tube socket and pin 68 placed in the two holes. In this position leg rest 84 is facing upwards and level with seat 14 as in FIG. 8. The vertical spacing member 80 places the leg rest below the level of the square tube socket 60.
Then pin [0032] 98 holding collar 90 at a position along arm 54 is removed and collar 90 with handle 92, used for arm exercises, is slid off the end of arm 54 and removed. This makes way for ankle rest 104 to be fitted. The ankle rest comprises ankle rest collar 106, similar to collar 90, with hole 108, similar to hole 94. Ankle rest collar 106 has member 110 fixed to it. Fixed to one side of member 110 is ankle pad 112. Ankle rest collar 106 is slid onto arm 54 and in held in place with pin 98 placed in one of holes 56 in arm 54 and hole 108 in collar 106.
Pin [0033] 50 is removed from circular plate 34 and the weight arm is then positioned to rest against stop 28 with arm 54 approximately vertical. In this position hole 44 in rectangular plate 40 lines up with one of holes 38 near the outer edge of the circular plate and pin 46 is placed in these holes. The user then sits on the seat with the back of his legs, just above the knee, supported leg rest 84. The ankles are placed behind ankle pad 110 and the user then performs the leg extension exercise by lifting his ankles. This rotates arm 54, the rectangular and circular plates, the hollow shaft and the weight arm in a clockwise direction, with the machine as shown in FIG. 8, lifting the weight and providing resistance to the exercise. The leg support and leg rest prevent the upper leg of the user moving downwards in reaction to the lower leg being lifted against a resistance. This also causes the body of the user to want to lift which is prevented by the user holding onto the seat close to where it is fixed to adjustable square tube 4, handles may also be provided fixed to the seat for example for the user to hold onto.
Different users with different leg lengths can be accommodated by moving the ankle rest. This is achieved by removing [0034] pin 98 from collar 106 and sliding collar 106 along arm 54 and replacing the pin in the hole in collar 106 and another hole in arm 54. Shorter legged users use one of the holes in arm 54 nearer hollow shaft 22 and longer legged users use a hole further from the hollow shaft. This allows ankle pad to press on the most comfortable part of the lower leg which is just above the ankle, whilst maintaining the knee joint in line with the pivot of the machine.
The use of the machine to perform leg curl exercises will now be described with reference to FIGS. 9, 10 [0035] 11. FIG. 9 has part of the machine removed to show the position of the leg rest in the square tube socket. To perform leg curl exercises the seat is left in the raised position. The leg support is removed from square tube socket 60 by removing pin 68 and turned upside down. It is then slid back into the square tube socket with hole 86 lined up with hole 62 in the socket and pin 68 is placed in the holes to hold the leg support in place. When the leg support is turned upside down vertical spacing member 80 raises the leg rest support above the level of the seat and the square tube socket with the leg rest facing downwards, shown in FIG. 9.
The [0036] ankle rest 104 is then removed from arm 54. This is carried out by removing pin 98 from collar 106 and sliding ankle rest 104 off arm 54. The ankle rest is then turned over and slid back on arm 54 and held in place with pin 98 through one of holes 56 in arm 54 and collar 106. Ankle pad 112 now faces forwards.
Pin [0037] 50 is them removed which holds the rectangular plate 40 to the circular plate 34 and the weight arm is rotated to rest against stop 30. Arm 54 is then rotated to approximately 20 degrees to the horizontal as shown in FIG. 10 11, in this position the hole in the rectangular plate lines up with a hole towards the outer edge of the circular plate and pin 50 is placed in them to link them together. The machine is now in the position shown in FIG. 10, 11.
The user then sits on seat and raises his legs, and with the front of his legs just above the knee under the leg rest, slides his legs across until the back of his ankles are resting on the ankle pad. The user is now in a position with his legs slightly bent and the backs of his ankles on the ankle pad and the front of his legs, just above the knee, below the upper leg rest. The exercise is now performed with the user pressing his ankles on the lower leg rest and bending his legs. This rotates [0038] arm 54 and the hollow shaft and lifts the weight off stop 30 in an ant clockwise direction with the machine positioned as shown in FIG. 10. This lifts weight 26 and provides resistance to the legs being bent. In reaction to the ankles being pressed down against a resistance the knees want to lift. This is prevented by the leg rest holding the upper leg and knee down. Users with different lengths of leg between the knee and the ankle can remove pin 98 and slide the ankle rest along arm 54, so that the ankle pad is in a comfortable position on the back of the ankle. Pin 98 is then replaced in a hole in arm 54 and the hole in collar 106.
For the leg exercises, leg extensions and leg curls, the seat is in the raised position, this places the knee joint of the user in line with [0039] hollow shaft 22, which is the pivot of the machine. This allows the leg exercises to be comfortable and safe. Movements of the upper leg, above the knee, in reaction to the exercise movements of the lower leg, are prevented by the leg support.
Thus as can be seen from the above description The machine has a seat which can be fixed at two different heights. The lower height used for arms and allows the user to place his elbow joint in line with the pivot of the machine in a comfortable position for exercising the arms. The higher seat position is used for legs with the knee joint of the user in line with the pivot of the machine, allowing a comfortable and safe position for exercising the legs. Thus it is easier and simpler to manufacture the machine described above with two seat heights and only one pivot, and consequently one means of providing resistance to the exercises rather than a machine with two pivots and means of providing resistance to the exercises, one for each pivot. The machine described above is therefore simpler to manufacture and fewer components, reducing the overall cost of the machine. [0040]
The machine described above with one pivot and two seat heights allows one machine to be used where previously two were required, which reduces the space required to exercise the legs and arms and means only one machine need be purchased. [0041]
The removable leg support saves having two leg supports one for leg extensions and one for leg curls which may restrict the movement of the user. The vertical spacing member which may be 80 millimeters long, changes the height of the leg rest when it is turned over by approximately 100 millimeters and places the leg rest in a lower position for leg extensions and a high position for leg curls allowing one socket to be used rather then two. [0042]
It is also possible to fix the leg rest to the seat, supported by a member which allows it to be lifted, in a similar way to [0043] arm 54 and collar 90 for example. If the leg rest is lifted the member supporting it for leg curls when it is above the leg may pass between the knees or to one side of the legs. With this design it may be necessary to have a leg rest on both sides of the member supporting it, one side, or the top against the legs for leg extensions, and the other side or the bottom against the legs for leg curls. Member 110 may also have an ankle pad fixed to either side, one side used for leg extensions and one for leg curls.
It is possible to have a machine which is only used for one exercise of the legs and arms, for example only arm curls and leg extensions, in this case resistance to the exercise is provided in only one direction of rotation. It is not necessary for the direction of rotation of the resistance to be the same for the arm exercise as for the leg exercise, for example only arm curls and leg curls could be performed on the same machine. A machine could also be made which allows leg curls and leg extensions and only one arm exercise, for example arm curls, or both arm exercises and only one leg exercise to be performed. [0044]
The resistance to the exercise may not be provided through the pivot, for example weights can be placed on [0045] arm 54 near to the ankle or wrist of the user to provide resistance to arm curls and leg extensions, with the pivot stabilizing the exercise movement. The pivot should still remain in line with the knee or elbow of the user.
The term pivot refers to the axis of rotation, and may not be a pivot, but may be a circular or semicircular track with its axis of rotation in the same position as the pivot. A point along [0046] arm 24 for example may slide along the track. Circular plate 34 may not form a complete cirde, and may be a semi circle as long as it covers all the positions which rectangular plate 40 rotates to when altering the machine to perform different exercises.
The handle which the user holds for arm exercises can be of different shapes. The exercise can be performed with the palms of the hands facing up or down or anywhere between and with the hands different distances apart, or even one handed. [0047]
Pins [0048] 12, 50, 68 98 can be spring loaded, being pulled out by the user and released when the required hole is in position. The raising of the seat may also be assisted by springs or gas struts. It is preferable that hollow shaft 22 is mounted on bearings to reduce resistance to the exercise.
There are many methods of providing resistance to the exercise, such as lifting weights on arms as described above, or electromagnetic resistance. Another method is shown in FIG. 12. Here [0049] hollow shaft 22 is connected to arm 114 instead of weight arm 24. A short member 116 is fixed to vertical member 18 and has a pulley 118 fixed to its end. Pulley member 120 is also fixed to short member 116 and has top pulley 122 and bottom pulley 124 fixed to it. Pulleys 118 122 124 are all in the same plane and each other and arm 114. Hook 126 is on the end of arm 114 and has a cable 128 attached to it by loop 129 on the end of cable 128. Hook 126 lies in a horizontal plane so appears as a line when shown on side elevation in FIGS. 12 13. Fixed to the other end of cable 128 is weight 130. The machine as shown in FIG. 12 is set up to provide resistance to arm straightening exercises and leg curls, with cable 128 passed over top pulley 122 and pulley 118 and down to weight 130. When either of these exercises are carried out arm 114 rotates in an anti clockwise direction pulling cable 128 over top pulley 122 and pulley 118 and lifting weight 130 to provide resistance to the exercise.
To perform arm curls or leg extensions pin [0050] 50 is removed from circular plate 34 and rectangular plate 40 as before and loop 129 on cable 128 is removed form hook 126. Arm 114 is then rotated by hand until it is just below bottom pulley 124. Cable 128 is then passed around and underneath bottom pulley 124 and loop 129 connected to hook 126. This is shown in FIG. 12. Pin 50 is placed in the appropriate hole for the exercise to be performed as before and the exercise is carried out. This rotates arm 114 clockwise, pulling cable 128 around bottom pulley 124 over pulley 118 and lifting weight 130. This method of providing resistance to the exercise easily and quickly allows a change in direction the rotation of the resistance to the exercise with the weight connected to the end of a cable. Weights on the end of cables are usually made up of a weight stack with different weights selected by removing and placing a pin into a central rod connected to the cable. This is easier than manually placing weights on rod and is preferred on many machines.
It may be desirable to have a number of different seat levels available all close together, maybe 20 millimeters apart for example, at the lower overall seat level used for arm exercises and a number of different levels at the higher overall seat level for exercising legs. This provides fine tuning of the adjustment to keep the joint exercised in line with the pivot and find the most comfortable exercise position for different sizes and shapes of user. A small amount of horizontal seat adjustment may also be desirable. A small amount of horizontal movement of the arm rest or leg rest may also be desirable to accommodate different sizes and shapes of user. For example a user may have long arms between the elbow and the shoulder joint, and when he leans his chest against [0051] chest rest 74 his elbow joint may fall below and in front of the pivot. This could be corrected by moving the arm rest up and backwards slightly. This can be achieved by making square tube socket movable up and down or forwards and backwards and able to be fixed in a new position. A forwards or backwards direction would be in a direction which would be represented by moving left or right respectively in FIG. 4. This would also allow the leg rest be moved to accommodate users with different sizes or thicknesses of legs and keep the knee in line with the pivot of the machine. The seat could also be made longer to replace leg rest 84 for leg extensions, the leg rest need only be fitted for leg curls. If the pivot of the machine is not in line with the joint of the user which is exercised, leg rest 104 would slide up or down the leg and handle 92 would want to move up or down the arm, causing the wrists to bend to accommodate the movement, as the exercise is performed. This is uncomfortable at best and may even cause injury.
It may be desirable to place [0052] square tube 4 at an angle which is not quite vertical. For example, if the square tube is on an angle which moves the seat forwards as it is lifted to place the knee joint in line with the pivot for leg exercises, the seat is further back when it is lowered for arm exercises. This provides more room for the body of the user between the back of the seat and the chest rest. The seat could also be made adjustable in a forwards or backwards direction.

Claims

1. A machine for exercising the legs and arms with resistance provided in at least one direction of rotation, with a pivot to stabilize the exercise, and with a seat adjustable to at least two heights, one height being such that the elbow joint of the user is approximately in line with the pivot, and another height being such that the knee joint of the user is approximately in line with the pivot.