Spin Solution (Duke University)

Ryan Denkewicz, Hersh Lakdawala, Boying Shui, Kavin Vasudevan

ABSTRACT

Prior to being diagnosed with a form of multiple sclerosis that severely restricted his mobility, the client was an avid cyclist who biked over ten thousand miles per year. The goal of this project is to assist him in riding a stationary bicycle with the long-term goal of building enough strength to cycle unassisted. The Spin Solution includes 1) a steel support frame, 2) a harness that provides variable core and lateral support, 3) a winch that provides a fail-safe, and 4) an ergonomic armrest to alleviate the load on the client’s left hand. The final product provides stability, graded support, and comfort, and has not only enabled the client to bike 1.2 miles but also encouraged him to set a goal of ten miles per day.

BACKGROUND

The client has multiple sclerosis, an autoimmune disease that attacks nerve cells and reduces the signals that nerve cells send to each other (1). As a result, the damaged nerves have induced paralysis on the left side of the client’s body. He lacks fine motor control in his left leg, which spasms periodically. In addition, his left hand is tightly clenched, making it painful for him to apply pressure on his hand. Finally, the client’s core has atrophied to the point that he requires assistance sitting upright. Given the client’s history as a cyclist, he would like to be able to ride a stationary bike. Commercial solutions are limited to recumbent bicycles, but the client prefers cycling in an upright position. The Spin Solution enables the client to ride upright by supporting him as he mounts, providing graded core and lateral support as he cycles, distributing the pressure from the client’s hand, and ensuring safety with a fail-safe winch.

PROBLEM STATEMENT

This project aims to provide the client with a safe and comfortable cycling experience by providing core and lateral support, alleviating the stress on his left hand, and ensuring that he will not fall off the bicycle.

DESIGN AND DEVELOPMENT

This image shows the completed system comprising a harness, a winch, resistance bands, and Aero handlebars.

Figure 1: Final Integrated System

The initial prototype addressed the lateral and core support via a counterweight system attached to an 80” x 60” x 72” wooden frame. The client wore a vest that was attached to the frame via carabineers and a strap that ran through a U-clamp on an elevated upper cross bar. The strap was connected to a variable rack with weights ranging up to 100 pounds. To ensure that the weight rack would not slip, its range of motion was restricted with an additional wooden crossbar. The setup successfully kept the client sitting upright, and prevented him from swaying too far to either side. To reduce the strain on the client’s left hand, handgrips were attached to padded PVC pipes that were then duct taped to the existing stationary bicycle handlebars. This allowed the client to rest his upper body weight along his entire arm rather than just his hand, and helped him to better support his own weight. To assist the client in mounting and dismounting, the frame featured two 36” high handrails and a detachable 8” wooden step that helped the client position himself more securely.Throughout the design process, the client’s safety was a top concern. After determining that the client wanted to cycle sitting upright, we identified key requirements for the Spin Solution to keep him safe and stable as he cycled. The system would need to provide lateral support to remain seated, core support to sit upright, and arm support to remove strain from his left arm. In addition, the system would need to support the client as he mounted and dismounted, so he could do so safely with only minor assistance from his wife.

Several design issues were discovered based on testing with the initial prototype. First, after assembling and disassembling the wooden frame several times, we noted that the joints degraded quickly. Second, tests suggested that separating the graded core support and failsafe mechanism rather than integrating them into the counterweight system would provide greater security. Third, the client indicated that the counterweight system did not offer enough freedom of movement, and that the harness was applying too much pressure to his chest. Fourth, the client’s wife noted that the boat strap system was difficult to adjust while helping the client to mount and dismount. Finally, the client’s physical therapist indicated that more ergonomic grips and additional adjustability in the armrests would offer better support.

With safety as the primary concern, the final frame is composed of 2 ½” welded steel for strength and longevity. The frame is 80” x 60” x 68”—slightly smaller than the wooden prototype to facilitate transportation—and is stabilized using 45-degree angled support beams. Two 36” handrails on either side of the support frame assist the client in mounting and dismounting. The steel frame separates into two halves for ease of transportation. An L-bracket extends from both the upper crossbar and lower crossbar of one half and extends into the other half. The two halves are fixed together with 3/8” steel bolts. To ensure that the frame stays level, it is mounted on four 5/8” hydraulic levelers with.

The steel frame comprises two symmetric side pieces featuring handrails, two horizontal beams (one in the back and one on top), and multiple 45-degree angled support beams.

Figure 2: Steel Frame

A winch system acts as a fail-safe, preventing falls and making mounting and dismounting safe and easy. The winch system consists of a Superwinch Series winch and an industrial grade block pulley. The winch is bolted to two blocks of HDPE, which are attached to the support frame (Figure 3a). The winch cable runs through the pulley, which is mounted to the middle of the upper crossbar (Figure 3b). The winch and pulley guarantee that the client cannot fall off the bicycle by restricting his range of forward motion to a pre-set distance, and help keep the client cycling at a set angle.

The winch is bolted to two HDPE 2"x2"x12" bars. These HDPE pieces are bolted to the horizontal crossbar in the back of the frame.

Figure 3a: Winch

The winch cable runs through the pulley, which is bolted to the horizontal crossbar at the top of the frame.

Figure 3b: Pulley

Resistance bands (Black Mountain) provide graded lateral and core support. The bands range between 2 and 30 pounds of resistance, offering variable freedom of movement so the client can increase or reduce support as necessary.  These bands attach to the angled beams using eye bolts (Figure 4). Bands can be added to either the left or the right side of the harness by clipping one end of the band to the harness and the other to an eye bolt, allowing the client to selectively increase support on one side of his body.

Five color-coded variable resistance bands attach to eye bolts on the metal frame on one end and a carabineer on the harness on the other end for graded lateral support.

Figure 4: Resistance Bands

Both the winch system and the resistance bands attach to a modified Ameristep climbing vest through a carabineer that runs through a nylon strap on the upper back of the harness (Figure 5). The harness distributes the load across the client’s chest and abdomen through five straps: three Velcro straps across the chest, a belt across the upper abdomen, and a buckle across the lower abdomen. The upper abdomen strap was included with the harness, while the additional straps were added to evenly distribute the load across the client’s body and to securely connect him to the support system.

The harness is a climbing vest adapted with five straps for weight distribution. The back of the harness features carabineers that facilitate connection to the metal frame.

Figure 5: Harness

The switches in the junction box at the front of the steel frame (Figure 2) allow the client’s wife to easily adjust the support system while helping the client mount and dismount by driving the motorized winch. The 12V winch is powered by a Peak PKC0AZ Jump Starter power supply, which is charged with a standard wall outlet. Both the winch and the battery connect to the female terminal of a 7-blade RV connector, which is housed in a metal junction box (Figure 6a). The male terminal of the 7-blade is connected to a four-wire 10 AWG power cord that extends to the junction box. The junction box contains two switches (Figure 6b): a 30 Amp DPDT Rocker Switch for ON/OFF control, and an Amico Self-locking Emergency Stop Button. The toggle switch controls the extension and retraction of the winch by reversing the polarity on the winch motor. Pushing up on the switch makes the winch recede, and pushing down on the switch makes it extend. The emergency stop button disconnects power from the winch when it is depressed and resets when the knob is turned clockwise. While turning off the power supply is the normal way to stop the winch, the emergency stop button provides an emergency cutoff option for the winch operator.

The 7-blade terminal safely connects the battery and winch to the switches, and prevents accidental contact with exposed electrical leads.

Figure 6a: 7-Blade Terminal

The Aero Evo Extensions (“Aero handlebars”, Figure 7) attach to a section of the stationary bicycle’s handlebar with the rubber coating removed. Zip ties secure the Aero handlebars to the spin bike. Adjustable armrests allow the client to distribute his upper body weight along his forearm. The armrests are set to accommodate the limited range of motion of the client’s left arm. The Aero handlebars were fixed to the stationary bike using zip ties to ensure that they would not shift from repeated use. Custom ergonomic handgrips at the end of the Aero handlebars provide continued comfort during long cycling sessions.

The Aero Handlebar features adjustable elbow pads to accommodate limited range of motion. Custom handgrips provide additional comfort.

Figure 7: Aero Handlebars

EVALUATION

This image shows the client using the Spin Solution in conjunction with his personal stationary bicycle.

Figure 8: Client Using Spin Solution

The goal of the Spin Solution is to provide a safe and comfortable cycling experience for the client. The Spin Solution’s functionality can be divided into four main categories: support frame stability, quality of graded core and lateral support, support and comfort of the harness, and quality of arm support. The final product keeps the client seated on the bicycle seat, provides him with a natural cycling experience while offering substantial lateral and core support, and allows him to distribute his upper body weight along his arms. The addition of several straps to the harness effectively distributed the load across the client’s body.

The continual adaptation of the system’s components in response to the client’s feedback yielded significant results: in his first trial with the finalized system, the client biked 1.2 miles—a marked improvement from initially being unable to stay seated for more than several minutes at a time. The client is very enthusiastic, and is confident that the Spin Solution “will let [him] ride 10 miles a day by the end of winter.” The Spin Solution offers the necessary support, giving the client a sense of security that encourages him to set ambitious goals for his rehabilitation.

After four months of use, the client reported biking roughly 35 miles every week using the Spin Solution. The client’s neurologist has shown significant interest in the benefits of his cycling therapy, and shared the above video with the rehabilitation department at the Mayo Clinic.

DISCUSSION AND CONCLUSIONS

The Spin Solution provides an effective and non-restrictive method of supporting an individual riding a stationary bike. While riding, the user is able to rely on graded resistance as well as a fail-safe support system. Ergonomic handlebars distribute pressure from the hand throughout the forearm, creating a comfortable riding experience.

At a price point of $1,364 per unit, the Spin Solution offers the client a comfortable and safe upright cycling experience. The Spin Solution was specifically designed to support the client’s weight, and the quality of the materials chosen reflects that decision-making process. The most expensive part of the system was the steel frame at $680. With mass production and more appropriate material selection—the frame can support far greater forces than necessary for the application—the production cost can be significantly reduced.

Future work for the device could consist of making it more universa. The device is adjusted and designed for a specific client, but by adding telescoping beams, the support mechanism could easily be adjusted for any user. This device could also be adapted for use with multiple exercise machines.

ACKNOWLEDGEMENTS

We thank Dr. Laurence Bohs and Josh Doherty for advising us through the project, Steve Earp for giving advice in designing components, and Jerry Spathis for building the support frame at Custom Steel. This work was supported by the National Science Foundation under Grant No. CBET-09672221.

REFERENCES

  1. “Multiple Sclerosis.” Multiple Sclerosis. Ed. David Zieve and Luc Jasmin. U.S. National Library of Medicine, 26 Sept. 2011. Web. 02 Dec. 2012. <http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0001747/>. 

Primary Authors:  

Shui, Boying; 8114 Bulrush Canyon Trail, Katy, TX, 77494

Vasudevan, Kavin; 15590 SW Tanager Dr, Lake Oswego, OR, 97035

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