DynEx™ Electronic Hand Dynamometer
and Isometric Exerciser
 The DynEx™ dynamometer offers therapists advantages not previously available in other technologies, and in a format which allows these advantages to be easily realized.
DynEx electronic hand dynamometers offer therapists and their patients a precise, versatile, reliable and user friendly professional instrument to perform Grip Test, or to perform isometric Grip Therapy using its scientific approach to strengthens the handgrip muscle group.
Two models, DynEx1 and DynEx2, are offered. Each is equipped with Grip Test mode, DynEx2 also provides Grip Therapy mode offering two methods for strengthening the handgrip muscles.
The microprocessor power of DynEx technology enables collection of all data and review of that data following a series of measurements, including an automatic calculation of statistical data. Microprocessor control also enables management of the isometric therapy in a manner previously not feasible, making this type of therapy viable.
DynEx handle widths are the same as those commonly used in the hydraulic JAMAR Hand Dynamometer, making it possible to transition from JAMAR without loss of consistency. Results of Norms tests conducted by the University of Florida Dept. of Occupational Therapy report excellent concordance between JAMAR and DynEx measurements. DynEx reliability exceeds 0.97 for test-retest exceeding those of hydraulic technology. Validity between JAMAR and DynEx achieved 0.95.
The DynEx instrument is designed for observation by either the patient or therapist, allowing for blind measurements, and configuration settings may be easily switched between English and Metric.
A data communications port located on the back of each DynEx provides a means of downloading archived data to a PC and for remote monitoring.
- Liquid Crystal Display: An easy to read Reflective Liquid Crystal display guides users through the exercise instructions, combined with audio cues. Operational temperature is -20°C to +50°C.
- Battery Cover: For easy access to the 9VDC Alkaline high capacity battery offering a battery life of over 6 months when the device is used by one person.
- Menu Button: Allows the user to access a list of functions provided in each DynEx model.
- On and Select Button: Activates the various modes of operation and can be used to turn the device OFF in advance of its automatic turn-off sequence when it is not used for 5 minutes.
- Front Handle: Designed to comfortably fit the palm or fingers of the hand and covers the electronic load cells that measure the force being applied (0.1 pounds or 1.0% force accuracy). Attaching a Grip Extender expands the grip width by 1/2 inch.
- COM Port: Provided to interface DynEx to computers and similar compatible devices for data access and remote monitoring.
- Durable Plastic Shell: Provides high-impact protection for long life. durability and ease of maintaining instrument cleanliness. The device weights 0.7 pounds or 0.3 kilograms.
- Rear Handle: Designed round and smooth to maximize the user's comfort and capability to expand the grip width by attaching a Grip Extender.
- Grip Extender: May be attached to either or both handles to provide adjustable grip widths from 1-7/8 inches to 2-1/8 inches, which are the commonly used widths (positions 2,3, & 4) on JAMAR-type hydraulic hand dynamometers.
DynEx1 and DynEx2 provide three dynamometer modes:
Max Grip Strength Test mode provides up to ten consecutive measurements of maximum grip strength in a series, each of which may be stored into a non-volatile memory as an accepted measurement or over-written with a next measurement. Following each accepted measurement, a set of statistics related to the series of measurements is automatically computed and displayed, including Average Strength, Standard Deviation, and Coefficient of Variation.
Endurance Grip-Strength Test enables measuring maximum grip strength (MVC, Maximum Voluntary Contraction), then selecting a % MVC (Max) as a target force to be held by a patient to evaluate the time this load can be maintained. The Endurance Test also measures the maximum force that can be maintained by a patient after it is impossible for them to maintain the target force as time progresses. The DynEx stores time markers in seconds as the applied force drops each 10% increment below the target force. Force data is archived by time markers for review after the test.
Rapid Exchange Strength Test provides a means of comparing a Right/Left Hand exchange spaced by 0.8 seconds or 1.5 seconds to measure instantaneous handgrip strengths in both hands, sequentially over a series of 10 or 20 exchanges. Following conclusion of this test, each of the strength measurements may be individually reviewed along with the statistics related to the series of measurements. Statistics provided include Average Strength, Standard Deviation, and Coefficient of Variation of the measurement series.
Archived Test Data is stored for ease of review during each DynEx session. All grip strength measurements are automatically stored into a non-volatile memory to provide therapists and users the opportunity to conduct a series of tests, and then later review each of the test results. These data are stored until the DynEx is intentionally turned off or a 5-minute period has elapsed without use, at which time the device is automatically turned off to save battery life.
DynEx training consists of a series of timed isometric Efforts performed by the hand grip muscle groups, at levels proportionate to Maximum Strength measured for the muscles to be trained. These Efforts are interrupted with timed Rest Periods between each of a series of efforts. The sustained isometric efforts of the DynEx programs require only muscle tension. They are purely isometric regimens which have been proved safe and effective[5,1] Since there is no movement, tendons are only stressed and do not move in their sheath. No outward work is being done as a result of the lack of motion.
DynEx training requires much less energy than rhythmic training, does not generate large amounts of heat in the working muscles, and does not yield sweating[6]. Compliance Scores are calculated during the therapy and are totaled during Rest Periods. Scores indicate the percent compliance with the prescribed Therapy thereby providing feedback to both the patient and the therapist on the quality of exercise accomplished. The DynEx provides two training regimens, called Fixed Therapy and Stepped Therapy.
Fixed Therapy
Exercise training provided under Fixed Therapy provides a fixed level of Effort, during a fixed time period, repeated a set number of times in an exercise Session, each Effort spaced by a Rest Period of fixed duration. Effort levels are established as a percent of the Maximum Strength measured in the handgrip muscle group to be strengthened. Therapists may adjust the Effort level from 10% of Maximum Strength, to 100% of Maximum Strength in 10% increments. Repetitions of the selected Effort level may be adjusted from 1 to 10. Duration of each Effort may be selected from 5 seconds to 120 seconds in 5 second increments. Rest Period between Efforts may be selected from 10 seconds to 120 seconds in 10 second increments. Nominated values for each of the parameters are provided in the DynEx protocol as a default setting following Maximum Strength measurements. Also, following therapist election of a % Max Effort, the DynEx program nominates the remaining parameters for Repetitions, Effort duration, and Rest Period times. Any or all of these nominated parameters may be adjusted to preferred settings by the therapist prior to initiating training.
Results
Dramatic results of using DynEx therapy show [7] that over a 6-week training period Strength increased by 20% in the trained arm and that a cross-training effect occurred in the untrained arm where strength increased by 15%. Endurance increased by 112% in the trained arm over the 6-week training period and the cross-training effect in the untrained arm caused a 43% increase in Endurance.
 Stepped Therapy
Exercise training provided under Stepped Therapy provides a stepped level of Effort, during a stepped time period appropriate to each of the Efforts, repeated a set number of times in an exercise Session, and spaced by a Rest Period between Efforts. Therapists establish the number of Steps (1-5) to be accomplished and the number of Repetitions (1-10) to be completed during an exercise Session. Effort levels are established as a percent of the Maximum Strength (MVC) measured in the handgrip muscle group to be strengthened. Therapists may adjust the Effort level in Steps from 20% of Maximum Strength (1-Step), to 100% (5-Step) of Maximum Strength in 20% MVC increments. Repetitions of the selected Effort level may be adjusted from 1 to 10. Duration of each hold Effort and the Rest Periods between Efforts are established by the DynEx automatically.
- Weight: 0.7 pounds, 0.3 kg
- Size (l x w x h): 2.5 x 1.86 x 7.75 inches, 6.35 x 4.72 x 19.68 cm.
- Display Type: Liquid Crystal dot matrix, reflective
- Power: 9volt, DC Alkaline Cell
- Accuracy: 0.1 pounds, 0.05 kg (or 1.0% Force)
- Maximum Capacity: 200 pounds, 90 kilograms
- Operational Temperature: -20 degrees to +50 degrees Celsius
- Materials: ABS Plastic shell, electronic load cells, surface mounted electronic components
- Patents: 5,398,696 5,904,639, Des.407,385 and new applications apply
- FCC Compliance: Part 15FCC Rules subject to conditions:
(1) Device may not cause harmful interference
(2) Device must except interference received
Each DynEx shipped in plastic carrying case with User Guide, 9V Battery and Grip Extenders
[1] Howden, R et al., The effects of isometric exercise training on resting blood pressure and orthostatic tolerance in humans, Exp Physiol 2002 Jul;87(4):507-515.
[2] Mathiowetz, V et al., Grip and pinch strength: normative data for adults, Arch Phys Med Rehabilitation 66:69-72, 1985.
[3] Mathiowetz V et al., Reliability and validity of grip and pinch strength evaluations, The Journal of Hand Surgery 9A:22-6, 1984
[4] Mathiowetz V et al., Grip and pinch strength: Norms for 6- 19 year olds, Am Journ Occu Ther 40:705-11, 1986
[5] Wiley RL et al., Isometric exercise training lowers resting blood pressure, Med Sci Sports Exerc 1992;24(7):749-754.
[6] Asmussen E, Similarities and dissimilarities between static and dynamic exercise, Circ Res 1981;48(6):I3-I10.
[7] Wiley, et al Manufacturing, 2002 controlled study, unpublished |
