What is the difference between JAS SPS & JAS Dynamic?

This is a question we often get from our patients when they’re deciding which device might be right for them. Our resident Orthotist & Prosthetist at JAS, Bryan King, answers it here.

Static Progressive Stretch (SPS) is a well established treatment technique used to permanently stretch shortened soft tissues of the body to restore range of motion in a particular joint.  SPS uses the biomechanical principle of Stress Relaxation (SR) loading.  Stress relaxation involves applying a stretch force to soft tissue and holding that force for a limited time until the resistance of the soft tissue drops and the soft tissue relaxes.  Once the soft tissue becomes relaxed at a certain length, the stretch force is increased to again reach a desired resistance of the soft tissue.  JAS SPS devices use this periodic, incremental application of SR loading over time achieve permanent restoration of joint range of motion.  Physical and occupational therapists routinely use SPS by manually stretching a joint to end range and holding that position.  Once the soft tissues relax, therapists apply a new stretch and hold, repeating this process throughout a 20 to 30 minute treatment session.  JAS SPS devices provide SPS for home use as an adjunct to clinical therapy.

Treatment protocol for JAS SPS devices is applying the device in the home up to (3) 30 minute sessions daily.  This protocol makes the SPS devices best suited for patients with orthopedic or acute soft tissue conditions who maintain an active daily lifestyle.

By contrast, JAS Dynamic devices use creep-based loading rather than SR loading.  In creep-based loading, tissues are continually elongated over time with the application of constant or continuous force.   While JAS Dynamic devices look and function similarly to the SPS devices, a key difference is the addition of a spring mechanism in the Dynamic device.  This spring mechanism will maintain active resistance to the soft tissue at its end range for the duration of the treatment time.  

Because JAS Dynamic devices use the creep-based loading concept, the treatment protocol is the use of the device for a continual time period up to 6-8 hours per day.  Consequently, these devices are best suited for patients who can wear the device at night and/or patients with medical conditions that keep them recumbent for extended time periods, particularly patients with neurological conditions.  The JAS Dynamic devices feature materials and cuff designs that better accommodate these longer wear times.