Determining Resistance: Dynamic Footrests

Michelle L. Lange, OTR/L, ABDA, ATP/SMS

Our last blog discussed how to determine the correct resistance for a Dynamic Rocker Back interface (DRBi). When a client moves within their seating system, the elastomers in the DRBi compress and the stored energy helps to return the client to upright. Various elastomers are available to provide the most appropriate level of resistance for an individual.

Seating Dynamics Dynamic Footrests can move in up to three directions. First, the footrests can telescope, allowing movement downward. Second, the footrests can elevate, allowing the knee to extend and the foot to move forward. Third, the footplate can move into plantar and dorsi flexion, allowing ankle movement.

How is Resistance changed on the Dynamic Footrests?

The telescoping feature provides up to 1.5” of movement and is adjusted by changing a spring. The installed default spring is Blue, which responds to 40 lbs of force. Yellow (20 lb) and Green (60 lb) are also available.

A cutaway of Seating Dynamics Footrest for wheelchairs

Resistance of the knee extension feature cannot be changed at this time, though Seating Dynamics is exploring the need for a firmer elastomer. Three clear, dog bone shaped elastomers are installed and can be changed out if worn (see photo right).

The plantar and dorsi flexion resistance is adjusted by changing 3 elastomers – Yellow (Soft), Blue (Medium), and Green (Firm) – to provide up to 10 degrees of movement in either direction. The installed default elastomer is Blue.

Determining Resistance and Replacement

So how do I determine if the resistance needs to be changed to best meet an individual’s needs?

To determine the optimal spring for the telescoping movement, watch the client as extension occurs. If no telescoping movement occurs, a softer spring may be indicated. If the client extends, leading to the dynamic footrest telescoping, but does not readily return to a starting position, a firmer spring may be required. If the client moves with different force on either side of their body, different springs can be used in each dynamic footrest, as well. These springs are quite durable and generally do not require replacement for wear and tear.

The resistance of the knee extension feature cannot be changed, however these elastomers can wear out. The resistance should be checked at least once a year. If the client is moving into knee extension too readily, the elastomers most likely need to be replaced. The care giver can lift a new dynamic footrest into knee extension, without the weight of a foot on it, to get a feel for the resistance and smoothness of operation. This check can be performed routinely, as often as monthly, to assess condition – if the footrest is not moving smoothly and demonstrating consistent resistance, service and elastomer replacement is likely required.

If there is no movement into plantar flexion during lower extremity extension, a softer elastomer is indicated. If the client is not returning to a starting position, a firmer elastomer may be required. As with other dynamic components, check for wear annually. If the client is no longer readily returning to a starting position, the elastomers may be worn and need replacing.

Please see the following document for the Dynamic Footrest assembly and adjustment:

Please contact us if you need to replace elastomers, and we can help you get what you need and walk you through the process.

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