image image image
Norm from CSMI   The HUMAC NORM is the number one solution for measuring and improving performance in the clinic, training room, and research laboratory.
     

 

Read the Full Story

Top Versatility with Con-Trex Multi Joint System.

With the dynamometer on a swivel arm the Con-Trex MJ System gives you the largest possible flexibility. Whether you like to evaluate or train in prone or supine position, this system makes it possible in the easiest way.

Read the Full Story

Biodex System 4

The most popular and advanced dynamometer in the world just got better and easier to use.

 

Read the Full Story
Main Menu Testing Knee Flexion / Extension

Flexion / Extension

Overview:

Until the late 1970s 75% of all isokinetic use and research was based on a single joint system - the knee. With more recent progress in rehabilitation and knee surgery this trend no longer exists. The basic design of isokinetic dynamometers (except for special purpose units) has not changed since the original instrumentation became available in the 1960s. The design is still better suited for knee testing and rehabilitation than any other joint (Dvir 1995). Although the knee has 2 major articulations the relevant one in this section is the tibio-femoral component.

Testing and exercise are generally performed in the sitting position although absolute hamstring testing is best performed in the prone lying position as this allows a greater range of motion and functional testing is best performed in the standing position. However, flexion and extension can be performed in either the Seated (most popular), Prone lying, Supine lying or standing positions.  

Seated position:

The most stabilised position for testing extension and flexion but it limits flexion unless the subject can get very close to the edge of the seat. Best overall position.

Seated testing assumes that minimal femoral motion will occur as the chair and body act as distal stabilisers of the thigh.

 kneeseatedminimalmotion

The subject usually sits with their back and thighs supported making approximately a right angle at the hip.

 kneeseatedoverall

The thigh support should extend to allow the appropriate amount of knee flexion. Try to leave two fingers gap between the chair and the back of the calf. In most tests this would be somewhere towards the distal third of the thigh which would allow 75-90 degrees of flexion (the maximum knee flexion available is approximately 110 degrees whilst retaining reproducibility).

kneeseated2fingerswidthclose 

 

This position then allows maximal extension (although debate rages over whether extension beyond -20 degrees should be permitted. Do not test beyond 0 degrees extension as an absolute maximum, subjects tend to find limitations beyond 5 degrees irritating and tend to do large isometric contractions to try to complete the range so try to stick to 0 degrees if possible. Although the angle of seat recline (from the semi-reclined to the upright position, i.e. 40-90 degrees), has little effect on quadriceps strength it has significant effects on hamstring strength. The optimal position is approximately 80 degrees (with a corresponding change in seat angle recline to give 90 degrees at the hips). This optimal position is suggested for both extensors and flexors as it allows the collection of good data over the least time.

To view a set up video see below

Standing position:

In the standing position stabilization is difficult if not impossible (and probably undesirable). Testing in this position is more functional than that in the seated position.

Prone lying position:

Prone allows for a much broader range of motion to be assessed. This position is generally used if the hamstring muscles are of particular interest (as stabilization of the knee flexion movement is easily achieved in this position). Stabilization is accomplished by allowing the subject to hold the seat edges and a femoral and waist strap should be applied. On the Cybex norm the seat does not lock into the down position this means that as the subject works the seat will raise up and crash back down. This can be prevented in the short term by wrapping the waist belt around both the patient and the chair. This appears to be an oversight on this machine. Best for hamstring tests.

The subject is prone and the thigh support extends to allow the knee to be off the edge of the seat. The seat can be seen as the red line whilst the blue stars represent the joint line.

kneeprone

To view a set up video press here 

Supine lying position:

Supine allows for the focus of the test to be on rectus-femoris. In essence it is the same as seated but with the chair made into a bed. This is the least used position. Supine testing assumes that minimal pelvic and femoral rotation will occur will occur as the chair and body act as distal stabilizers of the thigh, however, the subject will often shift the pelvis (hip hitching) to gain a better leaver advantage. 90 degrees  of knee flexion is needed in this position so you can obtain the peak torque measurement at the optimal angle of peak torque for the rectus femoris.

kneesupine

 

Stabilisation:

Seated: Stabilization is normally accomplished using femoral and pelvic strapping, however, the optimal set-up is a bit more involved. The number of research papers available on the subject is incredible. Magnusson et al (1992) showed that stabilization with a thoracic strap and the hands was associated with the highest quadriceps strength whilst no stabilization produced the lowest score. Hart et al (1984) also showed the use of a thoracic strap to improve quadriceps strength, whilst Hanton and Ramberg (1988) found exactly the opposite. Use of a thoracic, pelvic and femoral strap decreased quadriceps strength when compared to minimal stabilization i.e. only gripping the sides of the testing table.

Interestingly, Currier (1977) whilst testing isometric strength found that gripping of the table increased strength whilst gripping of handles did not show such significant improvements. These results were elaborated upon by Bohannon (1986) when he tested various gripping devices compared to only gripping the table and found massive differences. Hence, most isokinetic dynamometers do not offer hand grips as an option.

Prone Lying: Stabilization is normally accomplished using femoral and pelvic strapping and the subject is allowed to hold the chair or the handles provided.

Standing: Stabilization is almost impossible and  would be undesirable as this position is the most functional.

Supine: Is normally accomplished using femoral and pelvic strapping and the subject is allowed to hold the chair or the handles provided.

Attachments:

Whilst testing normal subjects the resistance pad is placed on a level with the inferior part of the pad immediately superior to the medial malleolus shown here (in other words the bottom of the pad touches the top of the medial malleolus). This is because 70% of all subjects tested by Kramer et al (1989) found this the most comfortable with the other 30% preferring a position at two-thirds of the usable leg length (after you have spent an hour determining the usable leg length and then calculating a position two-thirds down this, your subject will be so fed up the results will be negated by poor subject motivation).

kneeseated2

When using any selected location the subject should be free to maximally dorsiflex the foot (as seen below). 

kneepadonfoot

Close attention should be paid to not over tightening the strap around the shank as the resistance pad will, in all subjects, slide up and down the leg to some degree (this is because of the change in joint axis through range).

Siewert et al (1975) showed that the strength of both the extensors and flexors become successively smaller as the resistance pad is placed near the knee. This trend was established at all test velocities. Taylor and Casey (1986) have suggested that the reason for this phenomenon was increased intra muscular pressure which causes further divergence of the knee axis away from the actuators axis (or in other words the axis of knee rotation becomes greater which means that the axis of rotation you set at the machine must be further away from it). For every 1cm change an alteration of up to 5% in the values recorded can be expected.

These findings were supported by Kramer et al (1989) however, it is probably not that simple. Moving the resistance cell nearer the knee also shortens the dynamometer application arm and increases the angle between the arm and shank which when coupled with changes in neurophysiological inhibitory mechanisms, discomfort and pain all contribute to a general reduction in muscular strength. 

Consistency in the position of the resistance pads is, therefore, crucial.

Axis of rotation:

Setting up the machine to get the subject in roughly the right position is only the first part of the task. Do not be afraid to move the seat or dynamometer to allow for better alignment of the biological axis of rotation. At the knee this changes throughout range (so we use a compromise position). Dvir (1995) tells us this extends through the lateral femoral epicondyle (although alignment with the lateral joint line slightly anteriorly to the centre point generally offers better alignment throughout range see below). To check the alignment simply straighten and bend the knee and make sure that the attachment on the calf does not move up and down the shin (this can cause friction burns and does not allow the knee to rotate correctly).

kneeseatedaxis

If you find it hard to set the alignment correctly with the knee bent try doing it with it straight this often helps.

Subjects with limited extension will often lift their thigh from the seat as they reach terminal extension setting the axis of rotation slightly too far forwards (towards the patella) can help overcome this.

Small errors in alignment can be compensated for by the subject i.e. if you test the alignment and find the subject moves their body in the chair slightly continue to bend and straighten the knee until they stop adjusting and the alignment will be correct.

Anatomical zero:

With knee straight.

 

kneeseatedanatomicalzero

 

Range of motion:

For flexion try to be between 75-90 degrees of flexion. Then set the range of motion for extension  (do not test beyond 0 degrees extension as an absolute maximum, whilst subjects tend to find limitations beyond 5 degrees of flexion irritating and they will tend to do large isometric contractions to try to complete the range).

Gravity correction:

As the lever arm can be very long and heavy in these movements setting of gravity correction is essential. The effects of gravity help the hamstrings but hinder the quadriceps, however, if you always test the same person without gravity correction your results will be generally consistent (as long as the subject does not gain or loose allot of weight! Watch out for heavy and light footwear).

Speeds:

A medium joint speed for testing strength which is 1 degree per second for every 1 degree range of motion (think of it like this if we have already set a range of motion from 0 degrees extension to say 90 degrees flexion then a medium speed would be 90 degrees per second!). However, in the knee some speeds have been used allot in the research these are 60, 90 and 120 degrees per second for strength and 240, 300 and upwards for endurance. So simply choose one of these speeds to suit your requirements.

 

The range of angular velocities used to test the hamstrings and the quadriceps is extensive. Borges (1989) chose an extremely low value of 12 degrees/second for one of the criterion velocities, whilst at the other end of the spectrum Ghena et al (1991) and Hall and Roofner (1991) tested subjects at velocities as high as 500 degrees/second. It is debatable whether the use of high velocities in knee testing gives significant data for interpretation. A high velocity at the knee is considered to be above 180 degrees/second. Some studies (Ghena et al (1991) being the most significant) have demonstrated only very small strength differences above 300 degrees/second at the knee. The greatest change in muscular strength tends to occur between 30 degrees/second and 120 degrees/second.

The findings of Hall and Roofner (1991) have revealed a moment angular velocity curve which may be easily extrapolated to give predictions of strength values at high values for most normal subjects. It would seem then that testing at very high velocities would provide no useful information to the clinician. However, there may be good reason to test and train at high speed for muscle performance for professional athletes. In fact muscle conditioning at velocities around 450 degrees/second may still constitute a genuine stimulus to the muscle, as has been recommended by Mangine and Noyes (1992).

 

Any speed between 60 degrees/second and 180 degrees/second would generally meet most requirements for validity and the need for information about muscle performance. Between these ranges the subject tends to be comfortable and finds the movement reasonably easy to cope with. An added benefit is the very wide usage of these speeds in hundreds of studies. Very low and very high velocities are often contraindicated in most patients unless the purpose of the test is to provoke a specific reaction (testing at speeds outside the range of 60-180 degrees/second should be reserved only for professional athletes or very experienced clinicians).

Generally it is accepted that speeds of 60 degrees/second and multiples of this should be used.

Protocols:

TEST Protocol General Patients Athletes Research
Contraction Cycle  con/con con/con 

con/con

con/ecc 

 con/con

ecc/ecc

Speed/s  60 or 120  60 or 120  60-300  60-500
Trial Repetitions  0  0  3
Repetitions  10 10   10  5
Sets  3  4  up to 9
Rest  20-30 20-30   20-30  20
Feedback  nil nil  nil  nil 

 

Exercise Protocol General Patients Athletes
Contraction Cycle con/con con/con con/ecc
Speed/s 60 up to 180 60 up to 180 60-300
Trial Repetitions 0 0 0
Repetitions 10 10 14
Sets 6 6 up to 12
Rest 30-60 30-60 30
Feedback bar bar bar

Interpretation:

In the knee it is normal to look at the ratio between the right and left sides there should be a 0-10% difference between the sides. Anything beyond this would indicate a muscle imbalance which would be best corrected.

Eccentric results are generally 30% higher than concentric within the quads but are often equal to concentric results in the hamstrings of men and often below concentric in the hamstrings in women.

Generally the quadriceps will be twice the strength of the hamstrings I.e. hamstrings are 50% of quads ham/quad ratio is 50%. In athletes this can change to as high as 80% in long distance type events to 30% in sprinting type events.

Angle of peak torque for flexion is 30 degrees flexion.

Angle of peak torque for extension 70 degrees of flexion.

Normative values:

Figures for male athletes.

Muscle Group

Mode

Angular Velocity

Mean Peak Moments Nm (SD)

Extensors

Concentric

60

260 (59)

 

Concentric

120

219 (40)

 

Concentric

300

146 (27)

 

Concentric

450

113 (20)

 

Eccentric

60

257 (36)

 

Eccentric

120

260 (38)

Flexors

Concentric

60

142 (28)

 

Concentric

120

126 (24)

 

Concentric

300

88 (20)

 

Concentric

450

92 (27)

 

Eccentric

60

166 (40)

 

Eccentric

120

168 (39)

Based on Ghena et al (1991).

 

 

Concentric

Eccentric

Peak Moment

Extensors

Flexors

Extensors

Flexors

Women

       

15-24 years

2.19

0.87

2.37

1.06

25-34 years

1.98

0.85

2.36

1.11

Pooled

2.12

0.85

2.36

1.06

Men

       

15-24 years

2.98

1.21

3.09

1.44

25-34 years

2.49

1.08

2.67

1.37

Pooled

2.76

1.16

2.88

1.4

Average moment

       

Women

       

15-24 years

1.26

0.59

1.31

0.7

25-34 years

1.22

0.58

1.38

0.7

Pooled

1.25

0.58

1.34

0.7

Men

       

15-24 years

1.78

0.85

1.87

1.01

25-34 years

1.48

0.73

1.71

0.95

Pooled

1.66

0.8

1.81

1

Based on Highgenboten et al (1988)

Normative peak values expressed in Nm

 

120/second

900/second

1500/second

 

Right

Left

Right

Left

Right

Left

 

Age

Extension

Flexion

Extension

Flexion

Extension

Flexion

Extension

Flexion

Extension

Flexion

Extension

Flexion

Women

20

183 (34)

100 (20)

172 (31)

95 (20)

143 (25)

68 (21)

137 (24)

66 (17

110 (18)

49 (19)

106 (19)

46 (16)

 

30

169 (34)

90 (18)

163 (30)

88 (18)

138 (22)

61 (15)

134 (20)

58 (13

108 (19)

46 (14)

107 (15)

42 (12)

 

40

172 (28)

93 (20)

161 (26)

91 (18)

134 (20)

62 (14)

131 (20)

61 (13

105 (15)

46 (14)

102 (14)

46 (13)

 

50

153 (30)

76 (24)

143 (26)

75 (20)

122 (18)

52 (13)

114 (17)

51 (13

94 (16)

36 (13)

92 (14)

38 (11)

 

60

145 (20)

77 (14)

125 (24)

74 (17)

113 (13)

53 (12)

99 (15)

47 (13

84 (10)

38 (11)

79 (12)

35 (12)

 

 

70

128 (28)

65 (12)

120 (25)

59 (13)

98 (17)

39 (13)

93 (15)

38 (13

74 (12)

28 (8)

70 (11)

25 (9)

Men

20

289 (44)

155 (28)

269 (47)

144 (27)

231 (32)

122 (21)

217 (27)

113 (21

180 (24)

96 (19)

179 (22)

91 (19)

 

30

258 (45)

150 (28)

243 (47)

143 (35)

207 (38)

113 (23)

196 (35)

108 (29

158 (34)

91 (26)

160 (28)

87 (25)

 

40

248 (29)

149 (22)

238 (42)

144 (24)

203 (27)

112 (18)

197 (31)

106 (21

158 (24)

87 (16)

155 (26)

83 (15)

 

50

226 (51)

142 (32)

220 (45)

129 (30)

186 (26)

98 (24)

177 (32)

91 (25

145 (27)

82 (23)

143 (30)

76 (25)

 

60

223 (48)

130 (38)

212 (40)

133 (34)

179 (34)

95 (29)

169 (32)

86 (30

142 (28)

78 (24)

136 (22)

75 (25)

 

70

188 (36)

109 (30)

183 (37)

109 (32)

143 (24)

78 (26)

145 (30)

77 (23)

113 (22)

61 (23)

113 (21)

60 (26)

 

From Borges (1989)

Single repetition peak torque to body weight (foot pounds to weight in pounds) ratios for elite junior tennis players.

 

Left

Right

 

Male

Female

Male

Female

Knee extension

       

Torque/BW 180

60.2

 

60.5

 

Torque/BW 300

53.8

44.4

54

47.4

Work/BW 180

61.4

 

62.1

 

Work/BW 300

54.1

43.3

52.8

42.6

Knee flexion

       

Torque/BW 180

36.6

 

36

 

Torque/BW 300

33.7

30.7

32.6

31.3

Work/BW 180

35.2

 

35.2

26.5

Work/BW 300

29.5

27.2

29.5

 

Adapted from Chan an Maffulli (1996). All speeds 0/second.

Hamstring / quadriceps ratios for male and female junior tennis players.

 

Left

Right

Male

   

H/Q 180

61%

59%

H/Q 300

63%

62%

Female

   

H/Q 300

69%

66%

Adapted from Chan and Muffulli (1996) All speeds 0/second.

Hamstring / quadriceps peak torque ratio (dominant side)

 

600/second

1800/second

Control

58%

45%

Badminton

48%

52%

Cycling

45%

38%

Soccer

63%

52%

Adapted from Chan and Maffulli (1996)

Normalised strength at 500/second expressed as peak torque to body weight

Statistics

Members : 8335
Content : 114
Web Links : 6
Content View Hits : 3042504

Who's Online

We have 52 guests online
Open