Flexion / Extension

Lying position:

The most stabilised position for testing flexion but it limits extension unless the subject can get very close to the edge of the bed. Best for flexion research poor for extension.

To view a set up video press here 

Standing position:

In the standing position (see below) stabilization is difficult if not impossible (and probably undesirable). Testing in this position is more functional than that in the seated position and allows the investigation of extension. It is claimed that this is more functional and involves the use of gravity. However, this position is difficult to stabilize. If the knee is allowed to flex the resulting gravitational moment of the leg is lower than if the knee was fully extended and rectus femoris contraction may result in variations of the strength curve. However, flexion of the knee is recommended, although only passively against gravity if for no other reason than to avoid sciatic nerve traction. Best for athletes.

To view a set up video press here 

Stabilisation:

Lying: In the lying position stabilisation normally only involves a pelvic strap to prevent the torso from influencing the results and a leg strap for the opposite (non tested) leg.

Standing: Stabilistion in the standing position is not normally required as this is the most functional position.

Attachments:

The thigh stabiliser pad is normally used and should be positioned just proximal to the knee joint (see below).

Axis of rotation:

The instantaneous axis of rotation is simply straight across from the greater trochanter to the axis of the dynamometer (as seen as the red line).

Anatomical zero:

With leg straight (as in standing).

Range of motion:

Unfortunately there is great discrepancy concerning the normal ROM of the hip in the saggital plane. A good example of this is Boone and Azen (1979) who found normal hip extension to be 10 degrees, whereas Dorinson and Wagner (1948) found it to be 50 degrees. The point of maximal isokinetic strength is another area of contentious debate. Callahan et al (1988), in a very comprehensive study, suggested that 45 degrees hip flexion is the point of maximum efficiency (for flexion and extension). Consequently, strength measurements should be made from 0 degrees flexion to 75 degrees flexion (and obviously back for extension). 

Gravity correction:

As the lever arm can be very long and heavy in these movements setting of gravity correction is essential.

Speeds:

Once again debate rages over the speeds of motion of the leg during normal activities, however, slower speeds are normally chosen in the hip.

Generally it is accepted that speeds of 30 degrees/second and multiples of this should be used.

Protocols:

Interpretation:

In the hip 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 same muscle.

Concentric/concentric ratio; flexion/extension 0.60% this means the flexors are only 60% of the extensors or the other way around is the extensors are 40% stronger than the flexors

Angle of peak torque for flexion and extension is 45 degrees flexion according to Callahan et al (1988),

Normative values:

 Hip flexor and extensor concentric strength (based on Cahalan et al 1989)