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Frequently Asked Questions

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System 4 Pro™

What are the advantages of Biodex Isokinetics?

Nothing can duplicate the performance of the Biodex Isokinetic System.

  • Efficiency: Biodex Isokinetics is the only safe way to load a dynamically contracting muscle to maximum capability throughout its entire range in a continuous motion using either functional positions or isolated in correct biomechanical positions. A Biodex isokinetic contraction recruits a larger number of muscle fibers than any other method of exercise.
  • Safety: Biodex Isokinetic resistance accommodates to: Pain, Fatigue and Musculoskeletal Leverage. The resistance a patient encounters is in direct proportion to the effort. Patients will never encounter more resistance than they are capable of applying.
  • Decreased Joint Compressive Forces: High speed isokinetics minimizes joint compression and translational forces while it strengthens musculature. Biodex isokinetics allows high speeds even in short arc patterns.
  • Decreased Tibial Translation Force:  Combining high speeds and proximal pad placement can decrease anterior tibial displacement. 
  • Functional Training and Evaluation: Biodex isokinetic performance has been consistently shown to demonstrate a positive correlation to function. Only Biodex isokinetics allows patients to test and train with the isolated joints and surrounding musculature in biomechanically correct positions and at speeds that replicate function. All the parameters (including acceleration and deceleration) that define muscle functional performance can be measured.
  • Reproducibility: With the highest level of accuracy, and reliability of any dynamic evaluation procedure, only Biodex isokinetics allows for the objective determination of:
      • Need (functional disability)
      • Progress (response to rehabilitation)
      • Outcome (return to function)
  • Efficacy: There have been more than 2,000 studies published utilizing isokinetics as an evaluation and rehabilitation method, an estimated 60 million patient treatments.
  • Versatile and Cost Effective: The versatility and adaptability of the Biodex Isokinetic System allows safe treatment of the widest variety of patients through every phase of rehabilitation. The Biodex Isokinetic System increases clinic efficiency... treat more patients more effectively. 

Can you tell me more about Biodex reliability, accuracy, repeatability and validity?

These publications say it all, the Biodex System exceeds the performance and measurement capabilities of any other system.

  • BEMBEN, M.G., et al.
    "Reliability of the Biodex B-2000 Isokinetic Dynamometer and the Evaluation of a Sport-Specific Determination for the Angle
    of Peak Torque During Knee Extension" Isokinetics and Exercise Science / Vol 3, #3, 1993
  • BROWN, L.E., et al.
    "Reliability of the Biodex System 2 Isokinetic Dynamometer Concentric Mode" Isokinetics and Exercise Science / Vol 3, #3, 1993
  • FEIRING, D., et al.
    "Test-Re-Test Reliability of the Biodex Isokinetic Dynamometer" JOSPT, 11:7, 298-300, January 1990
  • FRISIELLO, S., el al. "Test-Retest Reliability of Eccentric Peak Torque Values for Shoulder Medial and Lateral Rotation Using the Biodex Isokinetic Dynamometer" JOSPT, Vol 19:6, June 1994
    "Trunk Extension and Flexion" Clinical Advantage Program, 1989 Biodex Corporation "Isokinetic Measurements of Trunk Extension and Flexion Performance Collected with the Biodex Clinical Data Station"
    JOSPT 11:590-598, 1990
  • GROSS, M., et al.
    "Intra-Machine and Inter-Machine Reliability of the Biodex and Cybex II for Knee Flexion and Extension Peak Torque and
    Angular Work" Abstract to be presented at the 1990 APTA Annual Conference in Anaheim, CA, June 24-28,
    JOSPT 13:6, 329-330, June 1991
  • HALL, P.
    "Comparison of Two Test Protocols for Isokinetic Determination of Quadriceps and Hamstring Peak Torque in Injured Individuals:
    Simultaneous Versus Individual Testing" Walt Disney World PT, 7508 Summer Laker Court, Orlando, FL 32811,
    JOSPT 13:5, May 1991
  • KEVELIN, A., et al.
    "Reliability of Biodex Isokinetic Measurement Using a Fixed Versus Anticompression Knee Attachment" (Abstract)
    Phys Ther 71:6, 1991
  • MONTGOMERY, L., et al.
    "Reliability of an Isokinetic Test of Muscle Strength and Endurance" JOSPT, 315-322, February 1989
  • SCHOONMAKER, W., et al.
    "Test-Retest Reliability of Isokinetic Concentric Mode Peak Torque Measurements on Healthy Children and Children with Spina
    Bifida" Phys Ther / Vol 72:6 (Supp) June 1992
  • TAYLOR, N., et al. (VALIDITY)
    "Static and Dynamic Assessment of the Biodex Dynamometer" European Journal of Applied Physiology (1991) 62:180-188
  • THOMPSON, M., et al.
    "Comparison of Value Generated during Testing of the Knee using the Cybex II Plus and Biodex Model B-2000 Isokinetic
    Dynamometer" JOSPT, 11:3, 108-115, September 1989
  • TIMM, K., et al.
    "The Mechanical and Physiological Reliability of the Isokinetic Mode of the Biodex Dynamometer"
    "The Mechanical and Physiological Reliability of the Eccentric Mode of the Biodex Dynamometer"
    "Concentric Isokinetic Test-Retest Reliability and Testing Interval"
  • VOIGHT, M., et al.
    "Reliability of Biodex Isokinetic Dynamometer for Measurement of Hamstring Reaction Time" Small, C.L. and Waters, J.T.,
    Univ. of Miami, Div. of P.T. Coral Gables, FL.
  • WILK, K., et al.
    "Reliability of the Biodex B-2000 Isokinetic Dynamometer" Physical Therapy, 68:6, 792, May 1988\
    "Intermachine Reliability of Three Biodex Isokinetic Dynamometers" Healthsouth Sports Med Rehab Ctr., Birmingham, AL 35205

Reliability, accuracy, repeatability and validity are important to Biodex because we require
precise measurement of muscle performance to objectively measure need, progress and outcome.
Only Biodex compares bilateral performance with built-in normative data.

The emphasis today in rehabilitation seems to be on Function. What place does an isolated joint testing system have in this environment?

The real issue in rehabilitation is restoration of the patient's full function, in the safest, most efficient and effective manner possible. It has never been documented that this process is enhanced by exclusively performing functional activities in rehabilitation.

Isolated joint testing and rehabilitation must be performed to develop the muscle performance necessary to safely progress the joint to weight-bearing activities then on to functional activities.

"It is important to develop isolated muscle function before progression to more complex multi-planer functional exercise. This gives the patient a firm base to build on."
Jay Irrgang, MS, PT, ATC

"If the muscle cannot function in an isolated pattern, then it cannot function in a functional pattern."
 — Jules Rothstein, PT, PhD 

What about correlation to function?

Every study ever performed to compare Biodex performance to functional performance has found a positive correlation. Consider:"Statistically significant trends were found between the hop tests and isokinetic testing."
Noyes FR, Barber SD, Mangine RE. Abnormal lower limb symmetry determined by function hop tests after anterior cruciate ligament rupture. Am J Sports Med 19(5), 1991.

"A positive correlation was noted between isokinetic knee extension peak torque (180°/sec, 300°/sec) and subjective knee scores and the three hop tests."

"A statistical trend was also noted for knee acceleration range at 180°/sec and the cross-over hop test and at 300°/sec and the timed hop and the cross-over hop test."

Wilk KE, Romaniello WT, Soscia SM, Arrigo CA, Andrews JR. The Relationship Between Subjective Knee Scores, Isokinetic Testing, and Functional Testing in the ACL-Reconstructed Knee. JOSPT 20(2), 1994. 

We hear so much today about Closed Chain exercise. How does Biodex address this?

The Biodex System and clinical protocols are designed around the concept of Integrated Physical Rehabilitation. That means doing the right thing at the right time for the right reason.With a Biodex System you can quickly progress a patient along a safe, efficient critical path to recovery. Use open kinetic chain within a protected ROM and at speeds that inhibit joint compressive forces. Use closed kinetic chain exercise in the way it was meant to be: controlling range and rotation to optimize the stimulation of neuromuscular mechanisms. 

How useful is the Biodex System in the early stages of rehabilitation?

During the early stages of rehab, acute/post-surgical, the Biodex System allows the clinician hands-on control to achieve the results the patient needs most:Decrease joint effusion.Increase range of motion.Improve healing of the articular cartilage and soft tissues.

The Passive Mode and its manual control ensure the most efficient patient/therapist/machine interface available, allowing the technology to be applied to even the most acute patients.

Noyes FR, Mangine RE, Barber S. Early Knee Motion after Open and Arthroscopic ACL Reconstruction. Am J Sports Med 15: 149-160, 1981.
Coutts R, Rothe C, Kaita J. The Role of Continuous Passive Motion in the Rehabilitation of the Total Knee Patient. Clin Orthop 159: 126-132, 1981. 

What does the Biodex System offer for patients in the intermediate stages of rehabilitation, when the development of strength is so essential?

The Biodex Isokinetic Mode allows smooth, impact-free acceleration and deceleration, with bi-directional velocities so that one side of a joint motion can be emphasized more than the other. In addition to maximal isokinetics, the Biodex offers submaximal isokinetics and isotonics with preset resistance limits for safety. Contractions can be performed in an Active Assistive (Concentric) or Resistive (Eccentric) manner and in any combination for agonist and antagonist muscle groups all in the Passive Mode. Eccentric resistance limits are always preset for greater safety and physical biofeedback.

Davies GJ. A Compendium of Isokinetics in Clinical Usage and Rehabilitation Techniques. S&S Publishers, Onalaska, Wisconsin: 4th Edition, 1990.
Davies GJ. Isokinetic Approach to the Knee, p221. In: Mangine RE (ed): Physical Therapy of the Knee. Churchill-Livingstone, New York, 1988.
Hislop HJ, Perrine JJ. The Isokinetic Concept of Exercise. Phys Ther 47(2): 114-117, 1967.
Moffroid M, et al. A Study of Isokinetic Exercise. Phys Ther 49(7): 735-746.
Giove TP, Miller SJ, Kent BE, et al. Non-operative Treatment of the Torn Anterior Cruciate Ligament Surgery. JBJS 65A: 184-192, 1983. 

Restoration of function is always the goal. How can the Biodex System assist in this most challenging stage of rehabilitation?

The reciprocal movements allowed by the Biodex Isokinetic Mode combined with the ability to measure acceleration to and deceleration from the Isokinetic speed consistently demonstrate a positive correlation to tests of the patients' ability to function. *The Biodex allows patients to exercise in functional patterns including standing shoulder diagonals, shoulder rotation in the 90°/90° throwing position, and closed kinetic chain movements for both upper and lower extremities. All patterns can be performed at speeds approximating function and in modes which allow simulation of functional contraction types.

The Biodex Isotonic Mode allows exercise with a fixed resistance at variable speeds controlled by the patient, allowing the clinician to evaluate the patient's ability to accelerate and decelerate their limbs or a fixed load. This functional form of muscle loading is often referred to as power training. Velocity spectrum training and functional power training are essential to ensure that a patient is ready to return to the field of play or the job site. 

McGorry R. Active Dynamometry in Quantitative Evaluation and Rehabilitation of Musculoskeletal Dysfunction.
Assist Tech 1(4): 91-99, 1989.
Rothstein JM, Lamb RL, Mayhew TP. Clinical Uses of Isokinetic Measurements. Phys Ther 67(12): 1840-1844, 1987.
Sapega AA. Muscle Performance Evaluation in Orthopedic Practice. JBJS 72-A(10): 1562-1574, 1990.
Wilk KE. Dynamic Muscle Strength Testing. In: Amundsen LR. Muscle Strength Testing, Instrumented and Non-instrumented Systems.
New York: Churchill-Livingstone, 1990.
Wilk KE, Andrews JR. Current Concepts in the Treatment of Anterior Cruciate Ligament Disruption. JOSPT 15(6): 279-293, 1992.
Wilk KE, Romaniello WT, Soscia SM, Arrigo CA, Andrews JR. The Relationship Between Subjective Knee Scores, Isokinetic Testing, and Functional Testing in the ACL-Reconstructed Knee.
JOSPT 20(2), 1994.
Noyes FR, Barber SD, Mangine RE. Abnormal lower limb symmetry determined by function hop tests after anterior cruciate ligament rupture.
Am J Sports Med 19(5), 1991. 

What about industrial medicine?

Treat industrial injuries with a proven sports medicine model. The kinesiology and physiology for human activity is independent of the environment in which such activity occurs. So, why treat your workplace rehabilitation patients different from athletic or general population patients?

The point is to restore functional capability as soon as possible. Precisely what Biodex equipment is designed to do. 

Referring Physicians, employers, insurance companies and HMO’s are now demanding more documentation than ever before. Can Biodex help?

Documentation is your management tool. Without it you cannot access or communicate Need (Functional Disability), Progress (patient's response to rehab) or Outcome (return to Function). The Biodex System has reports available with the information vital to the different participants in the patients rehabilitation program. The Biodex Narrative Reports are printed ready to be mailed. An enormous time saver.

The BIODEX Clinical Protocols enhance communication between the patient, clinician, physician and payors, and ensure successful outcomes. 

Can I get clinical help?

Yes! Biodex clinical assistance is always available, reliable and versatile.

Start off with a one-day in-service designed to acquaint clinicians with their new Biodex System. Review the basics of the Biodex Dynamometer, patient positioning and software use.

Continue with clinical training for a wide variety of pathologies.

Follow-up at any time with questions on application, patient setups, data analysis or testing procedures. Simply call our toll free hotline and get an immediate response over the phone from our experienced staff.

Use Biodex evaluation-based Clinical Protocols to help take the guesswork out of rehabilitation.

Stay abreast of the latest medical research and its implications for Biodex customers, by attending one of our many Clinical Workshop Programs.

Need backup data or research information? Our extensive library collection is filled with the latest medical and professional journals, abstracts, research articles, text and normative data, all available for your review. Biodex University 

What about durability, structural integrity and quality?

Biodex Multi-Joint Systems are relied on by more professionals than any other system... and for good reason. Biodex Multi-Joint Systems are designed to meet the clinician's every need and built strong enough to take whatever punishment a patient can dish out... while performing accurately and efficiently.

Here are a few of the professional and college teams currently using the Biodex System: Giants, Jets, Cowboys, 49ers, Dolphins, Broncos, Colts, Falcons, Marlins, Saints, Blue Jays, Capitals, Phillies, White Sox, Bears, Expos, Indians, Royals, Chiefs, Tigers, Mets, Angels, Dodgers, Lakers, Cardinals, Magic, Bullets, Supersonics, Eagles, Steelers, Arizona State University, University of Georgia, University of Iowa, University of Kentucky, University of North Carolina, Penn State University, University of Texas, and University of Michigan.

In the clinically competitive and financially challenging world of physical testing and rehabilitation... 

Why should a clinician buy a multi-mode, multi-joint isokinetic system?

The success of your practice depends on it! The clinical and financial sides of any practice are directly related. You need the ability to fulfill certain clinical needs in order to meet your financial expectations and obligations. Without a system that provides isokinetics, you simply can't rehabilitate or strengthen joints and their surrounding musculature in the fastest, safest and most efficient manner possible.

You need the ability to test, exercise, document, report and rehabilitate. Your system must be able to challenge and motivate anyone from a geriatric patient to a 300-pound defensive lineman. If your system doesn't have the ability to treat orthopedic, neuromuscular, workman's compensation, pediatric and geriatric patients, then you won't see these patients — someone else will.

Think about it. Come up short on the clinical end and you may come up short on the financial end as well.

Your success is dependent on doing the right thing. Now is the time to invest in yourself and the services you provide. 

How does the system know the lever length of the adapter shaft for calculation of torque?

It doesn't and is not required as torque is a rotational force measured at the axis of rotation. 

Does it use the time to complete ROM at set rotational speed of movement to calculate this?

No – torque is measured directly via a strain gage on the input shaft. 

Why are the metal stoppers attached to certain adapter connectors when you can self-select ROM?

Any attachment in which a limb is strapped in has a fixed ROM stop. This is a safety thing. For attachments in which a patient can let go, i.e., shoulder or wrist – there is no stop. 

Are there any guidelines for selecting max torque load limits during eccentric testing for various limbs and movements, and for various population groups and strengths?

Not really. It is totally dependent upon what it is you are trying to do. Whenever testing torque limits are generally set beyond what the patient will conceivably do. Note - the initiation force is 10% of the set eccentric torque limit. You don't want to set the limit too high so the patient cannot initiate the movement. Also - range of motion limits may have to be reduced when doing eccentrics. 

For the hip supine flexion/extension and abduction/adduction tests the adapter shaft seems to be very short.

Please be sure you are using the specified hip attachment. It is plenty long enough for pad placement on either the anterior or lateral side of the thigh. Check page 3-16 of the System 4 Pro set-up and positioning manual. This manual is available from our web site. 

For people with longer limbs, is there no alternative for testing, i.e. using the knee attachment? Otherwise at maximum position for these individuals, the torque generated and measured would neither be functional enough nor accurate.

Again – should not be an issue when using the hip attachment. 

For different limb tests and movements, there are no guidelines provided for gravity corrections in terms of positional setups?

Position the limb in the position of greatest gravity effect (close to horizontal, but not too close) and ask the patient to relax. You do not want flexion contractures or ligament tightness to confound the measure. 

Protocols on computer and in the Biodex booklet only show lying down hip abduction/adduction and not standing hip abduction/adduction protocol.

Hip testing is one of those patterns where some people prefer side lying or supine (better stabilization, especially for testing) and some prefer standing (quicker set-up, especially for healthy people). We went with the side lying/supine as the "standardized" position. The main reason is better stabilization. Also – patients don't necessarily want to stand on involved limb. 

Does one have to weigh the limb when testing hip abduction/adduction in standing or lying down? If yes, at what degrees does this have to be tested at?

Gravity correction is a personal preference. The most important thing is to be consistent as well as to be sure when comparing data that it is understood whether or not the data is gravity corrected.

The position to make the "weigh limb" measure will be close to horizontal. Again, make sure the patient is relaxed and no contactures. 

When testing hip abduction/adduction standing up one needs to use the right upper half of the knee attachment when testing the left leg & the left upper half of the knee attachment when testing the right leg. Why is this?

Position the limb in the position of greatest gravity effect (close to horizontal, but not too close) and ask the patient to relax. You do not want flexion contractures or ligament tightness to confound the measure. 

Is the manufacturer ISO certified?

Biodex Medical Systems, Inc. has been providing innovative products and service for more than 60 years. We manufacture our products in our state-of-the-art, 120,000 sq ft facility following strict quality control guidelines. Biodex is certified for ISO 9001:2008, ISO 13485:2003.

Is the manufacturer ISO certified?

Biodex Medical Systems, Inc. has been providing innovative products and service for more than 60 years. We manufacture our products in our state-of-the-art, 120,000 sq ft facility following strict quality control guidelines. Biodex is certified for ISO 9001:2008, ISO 13485:2003.


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