Regardless of the joint/muscular system involved, there are some basic principles that form the basis of interpretation. These are discussed in many studies, but are best described in Sapega (1990).
In the case of testing only one side, the opposite side should be used as a reference (this is not the case for athletes who use one side preferentially over the other, for example, the javelin).
Strength imbalance of up to 10% can be considered normal.
Imbalance between 10 and 20% is possibly abnormal (with injuries, this is considered probably abnormal).
An imbalance of 20% or more is probably abnormal (in injuries, it is definitely abnormal).
As a baseline measure for return to activity after injury, the following is true.
A maximum deficit of 20% for any individual muscle
A maximum shortfall of 10% for any member involved (ie closed chain test).
There are no validated values for light activities, but a decrease of 30% for a muscle and 20% for a limb is considered acceptable. Sapega (1990)
For example, the imbalance of muscle proportions can be used. shoulder internal rotators versus external rotators. Try to use meaningful ratios, ie concentric agonist activity to eccentric antagonist activity.
In the presence of pathology, it is advisable to compare theMAP curveon the unaffected side. Care must be taken when using this practice, as the shape of the MAP curve is highly variable. Separate sections pertain specifically to various pathologies and are best described in Chan and Maffulli (1996).
If both limbs are affected or the subject just wants to know how strong they are, comparison to normal values is acceptable, see normal values section.
The maximum value of the moment angle position(MAP) curve(The maximum torque is the highest point of the curve). This is considered the gold standard measure in isokinetic/exercise testing (Kannus 1994
When using peak torque to test a subject, it is appropriate to compare the left side with the right side and look for discrepancies greater than 5% Sapega (1990).
When comparing concentric to eccentric figures (at average joint velocities) in the same muscle (eg, biceps concentric with biceps eccentric), the eccentric figures should be 30% larger than the concentric figures (Brown 2000), without However, this varies from joint to joint and can be as low as 20% or as high as 147% (Brown 2000), and is related to speed (explained below in the force-velocity relationship). Individual proportions can be seen in the normal values section. In general, low eccentric figures indicate pathology (Dvir 1995), while high eccentric figures may indicate connective tissue disorders (Dvir 1995).
Figures can also be analyzed across joints (for example, quadriceps concentric to eccentric hamstrings may be important in people with anterior cruciate ligament deficiency, as eccentric hamstrings could theoretically resist anterior tibial translation during quadriceps concentric pull) in this situation, the closer the eccentric figure is to the concentric figure, the better (since eccentric muscle action is necessary to stop a joint movement at the end of range), this comparison is very important in joints unstable such as shoulder (but note that the figures can sometimes be misleading as the angle of maximum torque will often be different, to accommodate this the same angles should be used, eg Torque@angle).
The force-velocity relationship: Peak concentric force will decrease with increasing speed (as long as you start slow and build speed), while peak eccentric force will initially increase with increasing speed, then level off, and finally decrease. With this knowledge, it is possible to determine the force of an object in relation to velocity and plot it on a graph (known as a force-velocity curve). Force-velocity curves are used primarily to determine if an athlete is able to maintain his or her force with increasing speed. With this information it is possible to determine if they need to develop their movement speed or their strength.
Used in older machines (Kin-Com), force is usually measured in imperial measurements like pounds (lbs) or metric like newton meters (NM).
- LBS: Originally from the UK now measured in the US as an avoirdupois pound. This equals 16 avoirdupois ounces (exactly 7000 grains, one (international) grain equals exactly 64.79891 milligrams).
- KG: Being the only metric measurement taken of a physical mass, the kilogram is defined as equal to the International Prototype Kilogram (IPK) mass, which is equal to the mass of one liter of water.
All modern dynamometers (Cybex/CSMI Norm, BiodexPro 4, Con-Trex, BTE)
Force is actually measured as torque, which is the twisting effect (moment) of a given force on an object. Torque = moment x distance from the center of rotation (in this case, the center of rotation of the lever arm).
- Ftlb: An imperial measurement (used in the US) is the energy transferred by applying a force of 1 pound-force (lbf) through a displacement of 1 foot.
- Nm: A measurement of torque often referred to as a moment. One newton meter is equal to the rotational force of one newton (1 kg) applied to a moment arm one meter long.
Sum of the maximum torque measured on IROM / number of measurements.
This is often used to describe strength and is considered a less significant variable (since fatigue plays a large role in determining this value).
Maximum torque/weight ratio:
To compare results between subjects, the maximum moment is calculated in comparison to body weight (kilograms or pounds). Lower extremity strength depends on body weight and can be expressed in this way. Upper body strength is less dependent on and not generally described in this way.
Time Peak Torque Maintained:
Usually used in isometric testing, the amount of time maximum torque is held best demonstrates true isometric strength.
Time to half maximum torque:
The isometric reports only represent the time from the start of torque development to the point where torque is half of maximum torque. It demonstrates isometric resistance in a more meaningful way.
Maximum torque slope:
Used in isometric tests, it is the maximum torque divided by the time to reach maximum torque. It demonstrates how isometrically the contraction is explosive.
Decay time of the force:
Generally used in isometric tests, this is the time from the end of peak torque production to the end of the movement. It demonstrates the decay of a tetanic contraction, as such, it shows the real resistance potential of the muscle fibers.
It is used in isometric tests and normally replaces work. It is the average torque during an isometric contraction.
Angle Specific Torque:
It is used to determine a specific angle twist ratio that may be of interest (for example, when looking at agonist/antagonist con/ecc ratios). It has been shown (Kannus and Kaplan 1991) to be most reliable in intermediate ranges of joints with decreasing reliability at the extremes of movement. This measure is mainly used when the agonist is interrupted by his antagonist, but each can have a different angle of maximum torque. This value can be found in each contraction, so the actual relationship can be analyzed. For example, the internal rotators of the shoulder are concentrically resisted by the eccentric external rotators. The peak torque angle of the internal rotators would be used to find the correct angle to observe the peak torque on the eccentric external rotators.
Max Torque Angle:
As the name suggests (but is often referred to as the angle of incidence), this is when the maximum torque reaches its maximum level. It can be useful as an indicator of maximum torque output if plotted against various speeds (Osternig 1986). Weaker muscles (probably due to neuromuscular facilitation) show maximum torque later in the range (for individual ranges see individual joints), as demonstrated by Kannus and Jarvien (1990). The reliability of this measure is often very low (Kannus 1994) and worsens with repeated testing (due to alignment problems, Chan and Maffulli 1996).
Time to maximum torque:
It tests the ability to produce force rapidly and can be used to determine explosive power. A prolonged time to maximum torque may indicate reduced recruitment of type II fibers (Kannus 1994). This has been replaced by peak torque acceleration power.
Peak Torque Acceleration Energy:
Amount of work done in the first 125 ms of a torque production cycle. This should reflect explosive power as it measures speed and the rate of torque production. As a precise measure, it is highly variable at low speeds (Kannus 1994) and can be greatly affected by exercise cycles, ie if there is no pause between the con/ecc cycle, the results are often useless. The Ecc/ecc and con/con exercises produce the best results, however even these have been questioned as they may not have (according to Perrin et al 1989) a basis in Newtonian physics.
All described in standard international units Joules (J), which is a measure of energy and work (rather than force). It is equal to the energy expended (or work done) in applying a force of one newton through a distance of one meter (1 newton meter or N m),
A measure of the energy expended by the muscles being tested and considered by some authorities to reflect endurance. However, difficulties in assessing the importance of strength (or lack thereof) and endurance during the interpretation of these results make its use questionable for research purposes but good for rehabilitation.
W(work) = torque x angular displacement
Total Work (TW) = Area under the torque curve x angular displacement (after Hislop and Perrine 1967)
Work per repetition = Work done in each repetition
Max Power (PP) = work done during best rep (often called best rep BWR work)
Total Rep Max Work = Total work done in the rep with the highest torque max.
First third of work = the total work in the first third of the test
Last third of work = the total work in the last third of the test
W(work done) / T(time spent) = P(power) So, power is energy divided by time. The unit of power is the watt (W), which is equal to one joule per second.
Power is related to the average rate of working time. Power does not decrease with increasing speed as peak torque is produced during concentric contractions, but rather increases (Osternig 1986). The use of these measurements is limited mainly because the results can be obtained from maximum torque values to time values. These measurements may highlight differences between elite athletes when peak torque values appear to be unsuccessful (Kannus 1994).
Power measurements are becoming increasingly popular in the research community to look at performance in activities/sports that are not fundamentally limited by strength.
Momentum (average) x T(time) = I(impulse)
It is used in the literature to describe the difference in performance where the maximum torque reveals no difference.
The time required to reverse the direction of the member. Another measure of explosive actions that focuses on the ability to change direction quickly.
The time from the beginning of the movement to the beginning of the development of the pair. It was used to see if participants had extra rest with a set between repetitions.
The time required to accelerate to isokinetic speed.
This will increase with smoother stops and higher speeds. If you have done the test at high speed, the acceleration time needed to execute the movement may cause the maximum torque angle to not be included (as the values obtained during the acceleration time are not included, since this part of the movement is considered isotonic and is usually cushioned), so it's important to make sure the range of motion is great enough to accommodate this. If testing at many different speeds, the maximum torque angle should stay in the same place if the range of motion is sufficient; otherwise the maximum torque values may be useless.
The time required to decelerate from isokinetic speed to 0. It is only used in concentric contractions since eccentric contractions are controlled by the machine.
Coefficient of variation:
The amount of difference between repetitions in an individual set. This variable is used to check the consistency of a set, the closer the result is to 0, the more consistent the set will be. In stress tests, it must be less than 0.20 (Dvir 1995) for the test to be valid. A high number is expected in stress tests. In isometric and isokinetic tests, deflection is calculated from torque, while in isotonic tests, deflection is calculated from position.
Agonist antagonist relationship:
The peak torque of the weakest muscle group divided by the peak torque of the strongest muscle group and then multiplied by 100 to give a percentage. The weakest group is shown as a proportion of the strongest.
Fatigue and resistance tests:
Peak starting torque:
The average of the first three repetitions of an endurance test.
Final torque peak:
The average of the last three repetitions of an endurance test.
Combining the two measurements above, this is the percentage by which peak torque dropped during the endurance test. It uses a simple chi-square test, subtracting the initial maximum torque from the final maximum torque and dividing again by the initial maximum torque. This is then multiplied by 100 to give a percentage of 100.
Any value below 100 means that the subject is fatigued (the lower the value, the greater the fatigue, for example, a fatigue rate of 65% means that the subject was 35% tired during the test).
Note that a negative number means that the subject got stronger during the test, not weaker.
Resistance or fatigue rate:
The ratio of the total work of the first half of the set divided by the work of the last half of the set multiplied by 100. This is a more reliable measure of fatigue.
The most widely used measure of resistance. The amount of work done in a given number of repetitions is recorded. These tests are considered measures of absolute resistance that should be used in research settings (Kannus 1994). The problem begins when the subjects fail to reach the set number of repetitions required.
Time at 50% of maximum torque.
The amount of time it took to reach 50% of the initial maximum timbre values. The actual percentage can often be changed (Cybex Norm) and 40% becomes a popular number used. This measurement shows the point at which the type II muscle fibers (a and b) stop working and all the effort comes from the type I fibers.
Work up to 50% of the maximum torque:
The amount of work produced up to the point where torque levels dropped below 50%
Power at 50% Max Touch:
Power produced before peak torque dropped below 50% of peak
Biodex 3 and 4 systems use Isomap as the report type. In essence, an isomap looks at torque and position like a regular MAP curve, but adds speed (3 speeds are tested and shown) to the equation which produces a colored 'map' showing deficits in force or speed output, which are related angle. . In deficit, the mapped areas show problems, while the blue areas are fine.
Isomap is a mathematical model using low-dimensional embedding methods, where geodetic distances on a weighted graph are embedded with a multidimensional metric scale. The algorithm provides a simple method to estimate the intrinsic geometry of the torsion and position data based on a rough estimate of the neighbors of each data point with respect to velocity.
Controlled Comparison Speed:
The Con-Trex uses a 3D model of a standard MAP curve with position on the X axis and torque on the Y axis. Velocity is then added on the Z axis with up to 6 different velocities available to plot. Color is then added to distinguish deficits through range and speeds.
Mapeo muscular 3D:
Originally developed by NASA, 3D muscle mapping takes the standard MAP curve (force at Y axis position on the X axis) and simply adds velocity to the Y axis. This allows the performance of any given muscle to be viewed as a terrain map showing peaks and troughs. It is elegant simplicity.