Appendices

Introduction

The problem we are faced with in our design project is therapy bands, and, more specifically, the issue of their adjustability when they are tied in a knot. Sometimes the knot will come undone easily and will need to be tied again or sometimes the knot will refuse to be undone and may take a while to undo. This goal was introduced to us by our project partners, Dr. Bennett Goldberg, who is an avid user of therapy bands, and Dr. Melody Tran, who is a physical therapist. Both of our project partners had run into this issue quite often and thus asked for our help in solving this problem with therapy bands. Our goal, thus, is to create a device that can help ease the process of tying and untying a therapy band, all the while making it easily adjustable. We are writing this report here today to review what we have learned from our research about how we should design our device and inevitably create a prototype for it. Based on what we derived from our research, we will develop a prototype that is not only quick and easy to use, but also comfortable, compact, and cheap. Ideally, we would use a flexible plastic or rubber to minimize any potential hazards to the users (To be updated when the design is finalized). This report provides an overview of elastic and hard materials that can be used for our design. It will also provide an analysis on pre-existing ideas and solutions and what we can learn from them.

Design Criteria  

When it came to actually creating our design, we needed to be certain about what criteria our design would fulfill. In this case, the criteria refers to specific qualities our final design would have to have in order to effectively solve the problem proposed to our team. To determine these criteria, we used a combination of information from our project partners and additional sources to justify each of our solution goals. After conducting in-depth interviews and doing background research on common issues with therapy bands, we determined that our device needed to meet these three criteria: 1. quick and easily adjustable, 2. cheap and affordable, and 3. comfortable and compact. The rationale behind each of our criteria is described below.

Quickly and Easily Adjustable

The first, and most important criteria, of our design was to make a device that would make a therapy band quickly and easily adjustable. Our project partners had originally come to us hoping we could create a device that makes a therapy band easily adjustable. Their main problem with the current iteration of therapy bands was that when tied in a knot, it is very difficult for therapists to untie and retie the band [1].  Additionally, physical therapists have been desiring a device that could adjust the length of a therapy band easily, especially without the use of knots [2]. There was evidence that many others shared the complaints that our clients had. For example, there were multiple posts on a fitness forum specifically commented on how annoying it was to untie a therapy band after using it in exercises due to the knot tightening [3]. Therefore, a criteria that our solution had to meet would be to complete our main goal of making a therapy band quickly and easily adjustable, specifically quicker and easier to use compared to tying a knot in the band.

Cheap and Affordable

After determining the main goal for our device, we additionally had to determine some of the constraints on our design. One such constraint was determined to be the price of the adjusting device. During our interview with Melody Tran, she suggested that the medical community would be very reluctant to use the newly developed product unless it was extremely cheap and affordable [2].  Additionally, one of the main advantages to users of using therapy bands as opposed to other exercise equipment is that therapy bands are useful and durable at a very inexpensive price compared to many other apparati [4]. Within the medical community at large, the pricing of medtech devices on the market are constantly on the rise, causing price and affordability of a product to be even more relevant to its success [5-6]. In fact, according to an expert medical data analyst, innovators in the medical field “must find ways to understand exactly which product features their customers need and, critically, how much they are willing to pay for them” [7]. This concept is summarized by the theory of value-based pricing, which suggests the price of a device should be based on what it can do, how it was manufactured, and most importantly, how much a customer is willing to pay for these functions and materials [5-9]. During our interview with our client, they explicitly stated that they would not pay for our device if it was too expensive relative to what they pay for therapy bands (about $50 for 25 yards) [2]. With these plethora of sources suggesting the importance of affordability, keeping our solution at a cheap and affordable price became one of our design constraints. 

Comfortable and Compact

Another interesting criteria that was brought up during our initial project partner interview was the importance of comfort in our design.  During our interview with Dr. Bennett Goldberg, he emphasized that the design created must not be bulky as it cannot hurt a user if it is against their muscle during therapy [1]. Dr. Melody Tran echoed this point when she said that physical therapists care about the comfort of their patients over everything else [2]. Additionally, a patent for a therapy band device highlighted the essentiality of a non-bulky, compact design that wouldn’t infringe upon the user’s motion. This source discussed how different exercises with therapy bands will require different lengths, lengths that can only be adjusted by tying the band currently. They remarked that when the bands are tied, there may be long tail ends of the band hanging over which may impinge its user [10]. Therefore, another criteria for the design was to create a comfortable and compact solution that would not infringe upon the user more than the current therapy band.

In conclusion, we can see that our criteria that we decided for our prototype can be clearly reiterated through the needs of many others. We know that the therapy bands themselves are both durable and affordable, so our device should be too since they go hand in hand. Additionally, our client stated that they would not pay any more than a few dollars for the device, seconding that the device must be cheap and affordable. Therapy bands are also compact, with a slight issue on the tail ends of the therapy band hanging over when tied, so the device should also be compact so that it is comfortable to use. Finally, our device needs to solve the main problem of this project–to create a device that adjusts a therapy band quicker and easier than tying and untying a knot. 

Materials research

For our design we decided to use TPU and PLA. These are both thermoplastics that have varying properties. We chose TPU for its “squishiness” and its higher coefficient of friction. We chose PLA for its stiffness and its lower coefficient of friction. We knew our device needed to be comfortable and needed to hold the therapy band. TPU and PLA allow us to achieve both of these requirements. 

TPU

TPU is a material that satisfies our requirements. It is flexible, strong, durable, and fairly cheap [12]. This material is perfect for our design as it is biologically safe, will increase the resistance of our device to external forces, and is cheap. The manufacturing process of TPU is also relatively easy. For example, one of the ways that TPU can be manufactured is 3D printing. 3D printing TPU into custom medical devices is currently an area of extensive research. Research showed that after going through the 3D printing, medical grade TPU was still biocompatible with tissue [13]. This suggests that TPU would not stand a risk of causing an allergic reaction as latex would, because it is biologically safe and unreactive with human tissue. Additionally, TPU has a coefficient of friction greater than 1.2, which is large relative to many other easily manufacturable materials [14]. This suggests that there would be a larger frictional force to resist the external force of the band stretching during exercises, which would help to prevent these forces from distorting or snapping our band. This research has led us to a decision that TPU is the material we want to use in our designs, or at least something to be highly considered. 

Another very important quality to consider is the sustainability, or in this case recyclability, of the materials used. TPU specifically is a thermoplastic, which means it can be mechanically recycled by melting. In order to do this, TPU first needs to be reduced down to a granular form. A lathe is then used to cut down the original piece to pieces that can be recycled. Cutting down flexible materials like TPU can be difficult, but a high cutting speed and a shallow cutting angle can solve this problem. Once the material is granulated, the TPU is heated and put under pressure. This creates a new sheet of TPU. However, this sheet does not have the same material properties [19]. When a plastic is recycled, it experiences some mechanical and chemical degradation. As the TPU is recycled more, it slowly changes properties. It becomes slightly less elastic, begins to degrade at lower temperatures and its tensile strength decreases [20]. However, the key takeaway is that TPU can be recycled. This fact further enhanced our confidence in using TPU as the main material for the project.  If our design goes into mass production, not only it will be recyclable; we can use recycled TPU for our design to make our product more environmentally friendly.

PLA

PLA is an additional material that we researched for production of our design due to its common use with 3D printers. In fact, PLA is one of the most popular materials used in 3D printers, due to its low melting point, ease of use, and affordability [15]. Additionally, PLA is quite hard, with a shore hardness value of 76.3 on average (with 0 being least hard and 100 being most hard) which would allow it to sturdily clamp the band in place during user motion [16].  However, PLA has a significantly lower coefficient of friction compared to TPU [17]. Therefore, PLA could be useful in our design due to its inexpensive price and its sturdiness; however, the lesser force of friction it would exert is important to keep in mind when designing our solution. The lower coefficient of friction could actually be useful as we do not want high friction against the users skin. 

Injection Molding

We wanted our plastics to be easily manufacturable so we also conducted research on a method called injection molding. We found that injection molding is a very common way to mass produce plastic objects and it works with TPU and PLA [18]. In a very basic overview, plastic is first melted and pushed into a mold at high pressure. Then it is left to cool. Once the plastic has solidified, the mold is removed and the object has been created. This can be done over and over, which means that injection molding is a method allowing for mass manufacturing. We have discovered some design considerations for injection molding as well. For example, sharp corners are undesirable for injection molding. The molten plastic does not flow well through sharp corners, so rounded corners are preferred [18]. Another design consideration is wall thickness; if wall thickness varies throughout the produced item, the thinner wall will cool faster than the thicker wall. It will cause warping, so walls should be a uniform thickness. Based on the discovered information, we will make the walls of our design prototype equally thick, and also we will make the edges more round so that it can be compatible with this manufacturing method, if we do choose to use injection molding.

Surface coating

To preserve the durability and improve the comfort, we considered coating our design in a softer, rubber-like material. One of the existing solutions is silicone. Currently, siloxane hybrid with other organic resins is used [21]. For industrial maintenance applications, engineers employ three-coat system consisting of a zinc-rich primer, epoxy base coat, and a polyurethane topcoat [21]. For premium top-coat finishes, polysiloxanes are used in two-coat systems, that are less costly, quicker and more resistant to external factors. XTC-3D® – protective coating for finishing and smoothing 3D-printed surfaces, that was developed by Smooth-On in USA [22-23]. This coating contains two parts: resin and hardener. It dries in 4 hours and can be applied by hand very easily, without melting the plastic underneath. One 24 oz package of commercially produced XTC-3D® costs between $18-28. Provided 1 oz can cover more than 100 in^2, it is very inexpensive to use. As a result of using XTC-3D®, 3D-printed surfaces become smoother, more even and all the sharp edges are eliminated.  This solution can make our design more comfortable to the users’ skin and to cover the sharp edges left after 3D-printing. XTC-3D® was found to be the most appropriate because it is extremely easy to apply, the price is very low, and it provides the substrate surface with the properties we were looking for: smoothness and softness.

Latex

Latex was a material we decided against early on. We knew before doing any research that latex was a highly flexible material and may be suitable for our design. However, after conducting an interview with our client we learned that latex should not be used due to potential allergy problems. Therefore, we decided to do some research to see if latex allergies can be mitigated, and to find possible latex alternatives on the market. We found that many people have a latex sensitivity which causes allergic rhinitis and could lead to asthma [11]. According to the same resource, the only way to combat a latex allergy is to avoid contact with latex. Based on this, we have decided to avoid using latex in our designs. Using latex in a device for a therapy band, when it would often be in contact with the patient’s skin, could lead to several issues that would best be avoided. We do not want to create another health problem while the user is trying to solve one with their physical therapy. 

Preexisting Ideas

The remaining part of our background research was focused on preexisting ideas and solutions to the problems we face in our design. The purpose of this research was to learn from ideas that came before ours. By analyzing already existing solutions and inventions, we can learn what makes those things good and what makes them bad, what made them successful or what made them fail, and ultimately what can we use in our design from these ideas. Through this research, we were able to decide on ideal parameters for our design. 

Tension Measuring Devices

In our research, we looked at several preexisting ideas and methods that could measure tension as our client had hoped that we may be able to quantify tension in therapy bands. One such idea was a device called the WBR-SH2, a special resistance band with sensors that could measure and analyze the amount of strength and speed applied to the band and, thus its tension, utilizing a connection with a smartphone to do so [24]. Another device that was also created to measure the tension in a therapy band was a wireless wristband with a highly sensitive measurement that could measure the acceleration and thus force and tension [25]. While both these devices fulfill their purpose of measuring tension very well and were very comfortable to use, both of them also utilize fairly advanced technology. They are not as complex as compared to other devices, but they are likely fairly expensive and getting these devices in bulk would not be cheap, especially with the amount of therapy bands that physical therapists provide.

Another idea that was used to measure the tension in therapy bands was the use of a traction machine, a large separate device [26]. However, such an idea would only work for specially designated bands. This device measured the tension in a band, however the tension of a band relies on the total length of the band. Physical therapists when assigning therapy bands to patients cut arbitrary lengths that they deem fitting and would thus not actually have the same measure tension for another length. Not to mention, a large device like this would not only take up time to use if it were to be used with the random lengths of therapy bands, it would also get in the way and interfere with a patient if it were to be directly used as a patient did exercises. 

Based on our research about tension measuring devices, we unfortunately deem that measuring tension is far beyond the scope of our project. These devices are either expensive, complex, time consuming, or bulky, all of which go against the ideals of our project design since we aim to design an idea that is cheap, simple, quick, and most importantly, comfortable and we likely will not be able to create a modular device that can quantify tension that also fits these parameters.

Preexisting Patents for Therapy Band-like Devices

Alongside our research on existing tension devices, we also researched about preexisting ideas for adjustable therapy devices. One of the things we found was a patent for a device that was described as a “portable elastic type device” that was notable for being highly adjustable [27]. This device used a sort of looping mechanism that could be extended or shortened to adjust the length of the rest of the device. However, based on the sketch in the patent, the looping mechanism took up a large amount of space, around 25% of the entire device’s length and was 3 times the width of the device itself. Another patent we found was an exercise device that was comprised of several buckles and that could be adjusted using said buckles. When we look at both of these devices, we can see that there are three main problems that arise. The first device is slightly complicated and fairly bulky and will very likely interfere with the user. The second device on the other hand, is slightly time consuming due to the numerous buckles, although it is simpler in mechanism. These problems coincide with the problems that came up in the tension measuring devices. It can then be seen that ideally, our own device would not have these problems. The last idea we found was a simple clip on an online exercise and therapy device catalogue. This device was not only simple and, in theory, quick to use, but it was also small and cheap. At only $1.70 per clip, it is very affordable. That isn’t to say that this device isn’t without its own problems, such as the material its made out of potentially being uncomfortable to use as well as being quite bulky, but we can learn from that and take that into further consideration when we make our own prototype.

Conclusion

Our background research covered many topics related to the development of our design. After researching the materials, we discovered that thermoplastic polyurethane (TPU) is preferable in our design due to its flexibility, durability, low cost of manufacturing and recyclability. It is also compatible with 3D printing. On the other hand, we learned that latex is not a suitable material for us as it sometimes causes allergic reactions. Also, we found a way of manufacturing plastic objects called injection molding that we can possibly use for the production of our design. And with those materials in mind, we will need to create a prototype that does not fall into the issues that we discovered in already existing ideas and solutions in tension measuring devices and therapy band like devices. 

Based on the rationale for our design criteria, we can conclude that our device should be simple, quick to use, cheap, and above all, comfortable for the user. So as we stated in the thesis earlier, we will develop a plastic-based design that will be simple, quick, comfortable, and affordable to produce. Based on the conducted research, we would like to use materials such as TPU for our design, possibly involving manufacturing methods such as injection molding and 3D printing. We would prefer to avoid materials like latex to decrease health risks, and add a surface finish that will make the device more comfortable to use. Our design will also take into consideration the ideas of successful previous devices, most prominently the clip device, to build upon and improve previously successful ideas. Therefore, our design will be a shortened, doubled chip clip device which will provide more comfort to the user than previous designs. This design will be made out of a combination of PLA and TPU in order to maximize the friction of the material without compromising the stiffness necessary to properly hold the clip in place.

Bibliography

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[2] M. Tran, “Interview with Physical Therapist About Therapy Band Issues,” 10-Oct-2019.

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[4] S. Ashe-Edmunds, “Advantages and Disadvantages of Resistance Bands,” SportsRec, 23-Aug-2011.

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Project Name: Adjustable Therapy Bands

Client: Dr. Bennett Goldberg, Melody Tran, Athletico

Team members: Johanna Kann, Garrett Short, John Wu, Nastya Lantsova

Date:         10/3/19

Version:       Updated 11/19/2019

Mission Statement

We will design a modular attachment to a therapy band that will not only be user friendly and simple, but also comfortable to use and will not interfere with its user.

Project Deliverables

• Final report (printed and bound)
• Presentation and poster during the Design Expo
• Physical prototype of our design

Constraints

• All deliverables are due on December 7, 2019
• The project budget is $100
• Design must not be bulky
• Design should not be too expensive
• Design cannot injure or interfere with its user
• Design should be simple
• Design needs to be user friendly

Users and Stakeholders

• People who attend physical therapy and utilize therapy bands

• Dr. Bennett Goldberg, who attends physical therapy and uses therapy bands

•  
• Physical trainers and therapists
  • Melody Tran, a physical therapist at Athletico who also uses and assigns the use of therapy bands
• Companies that produce therapy bands such as Theraband

User(s) Profile

• Dr. Bennett Goldberg is a man in his 60s and is an Assistant Provost for Learning and Teaching at Northwestern University. He attends physical therapy and thus utilizes the therapy bands for exercises. He finds the constant need of tying and untying the therapy bands inconvenient, as the knots can come undone easily or may be extremely difficult to undo.

• Dr. Melody Tran works as both a physical therapist and facility manager for Athletico. Because of her job, she is required to constantly assign therapy bands to her patients and she finds that tying them is the most inconvenient part of the therapy bands for the same reasons that Dr. Bennett Goldberg have: the knots can come undone easily or may be extremely difficult to undo.

User Scenario

Dr. P.T. is a physical therapist who works at a physical therapy facility daily with patients, providing care to them and helping them improve their movement and heal by providing them with tasks and exercises to do.

Dr. P.T. wakes up early to go to work. She gets to her facility and prepares to get to work with patients. Patient 1, who has had a stroke and lost partial control over their left arm, comes in for physical therapy with Dr. P.T. to help regain control in their left arm. Dr. P.T. reviews their condition and notes that they are improving and assigns them a therapy band exercise called “wall-walking” in which the user must hold down one end of a looped band and stretch the other hand in the band in three directions on a wall. Dr. P.T. quickly ties a therapy band into a loop and leaves Patient 1 to do their exercise. 

Patient 2, who has recently had surgery on their leg, also comes in to receive physical therapy. Now Patient 1 is on sick leave due to their stroke, but Patient 2 is coming in early right before they go to work so they don’t have as much time as Patient 1. Dr. P.T. does a quick check on Patient 2’s condition and assigns them proper exercises to do. Patient 2 is to do clamshells with a therapy band, in which the user must lie on their side and bring one leg apart with a looped therapy band, like a clam opening its shell. Patient 1 just finishes with their exercise and Dr. P.T. wants to assign them an exercise using an unlooped band. Dr. P.T. takes the band Patient 1 was using and tries to untie it but it becomes stuck. Dr. P.T. spends around a minute trying to untie the band before it finally comes loose. Meanwhile, Patient 2 comes up to Dr. P.T. saying that the band has come untied and several more patients are also coming in. Dr. P.T. here would easily have become overwhelmed with patients and waste a lot of time, but luckily for Dr. P.T., there is another physical therapist on location who knows Patient 1 and Patient 2’s medical history so she refers them to that physical therapist and goes to check in the incoming patients.

Needs Identification, Metrics, and Specifications

CLIENT INTERVIEW SUMMARY

We had our initial interview with our client, Dr. Bennett Goldberg, the assistant provost for learning and teaching, and a therapy band user, on Tuesday, October 1st, 2019 at 5:30 p.m., in the Ford Building. Johanna Kann, Garrett Short and John Wu were present. The purpose of the meeting was to learn more about the problems that therapy band users experience while using the band, and to learn about the reasons behind these problems.This appendix summarizes what we learned about the main design problem, constraints, users, and current alternatives.

Problems

Our client has highlighted several problems that users experience while using therapy bands:

1. It is easy to make a knot on a therapy band, but it is difficult and time consuming to untie and re-tie it. It is especially problematic for the therapists;
2. There is no way to measure the differences in resistance and the strain caused by making a knot – the resistance can be too strong or too weak;
3. It is complicated to find the right size and resistance for a particular person when making a loop.

Requirements

Our client emphasized the following requirements for the resign:

1. Time/Ease of use
   • The main requirement is the ease of use – if it is too difficult and too time consuming, the therapists will go back to knotting the band;
2. Cost
   • Must not cost more than $100;
3. Size and material
   • The size should be compact enough to not interfere with the patients’ motion – not bigger than a fist;
   • Must not be bulky so that it does not hurt when against muscle or leg during therapy;
   • Must have enough strength to hold the two ends together;
   • Material should be soft and easily pliable;
4. Safety
   • Should be strong enough to prevent unclasping (which can hurt or pinch the user);
5. Other recommendations
   • Should be able to adjust clasp from one band to another – sometimes therapists send bands home with the patient;
   • Should be reusable;
   • Semi-rigid modeled plastic as a clasp material suggestion;
   • Should have a way to measure the resistance and the strain of the band loop.

Users

The user group is very diverse and it includes both patients and practitioners. Some users have major physical disabilities which limits their use of therapy band. Most users utilize therapy band for pressing, walking exercises and upper body motion. Many users prefer to have therapy bands at home.

Existing Alternatives

Dr. Goldberg specified that so far the following equipment has been used:

1. Theraband;
2. Pre-made bands in loops of various sizes. This alternative did not satisfy the users as it was hard to find the correct resistance and size of the loop.

The interview provided crucial information for understanding the problem, users, and client requirements. When we do our user observation, we will learn more about the therapy band applications for various health conditions and the constraints of using a therapy band.

The purpose of the user observation session was to understand how physical therapists and patients use the therapy bands, what difficulties they have using it, and what they think about the therapy bands. The observation session lasted about one hour. This appendix explains the methodology of the observation, describes the use of the therapy bands, and summarizes the results of the observation.

Methodology:

The observation took place in an Athletico physical therapy facility. There we interviewed Dr. Melody Tran, one of the head physical therapists there and our client. She was interviewed on her opinions on therapy bands as well as how the therapists and the patients use the bands. Afterwards, a few patients were observed using the bands in exercises. Throughout the entire session, we continued asking Dr. Melody Tran and two other physical therapists what they wanted in a solution and what their priorities are in the design, which, above all, was comfort and user ease.

Use of therapy bands

The athletic bands allow for a plethora of different exercises due to their flexible nature. There are exercises called clamshells in which the user opens their legs like a clam (See Figure 1) and exercises where the users have a band around their legs and walk sideways with the tension (See Figure 2). There are also exercises where the user may simply stretch their arm while the band is anchored to something (See Figure 3).

There are a few different ways the bands are used in these exercises. They are either held just as the band, tied in a loop, or anchored to something. When they are tied in a loop they are often tied again to adjust the size. It should be noted that the physical therapists do most, if not all, of the knot tying during physical therapy at a facility, not the patients. If a knot comes undone, usually one of the physical therapists will fix that. Anchored bands are also generally tied in a knot and hooked onto a wall.

The issues arise when the knots the bands are tied into don’t stick together and fall apart or don’t come apart and are extremely difficult to undo. The tying and untying the physical trainers have to do while working with their clients is difficult and time consuming and every second matters for them. Furthermore, the bands that are anchored are often tied to the anchor for weeks and, after repeated use, the knot can become near irreversible (Figure 4). Dr. Melody Tran mentioned using scissors to remove these if it came to it. There are also tube therapy bands that face similar problems, although these aren’t used as much as the flat therapy bands are generally more versatile. There are also bands that come with loops already built in segments. However, these bands similarly lack the versatility of simple flat bands as these bands come premade and cannot be cut to a desired length.

User’s interaction and difficulty with therapy bands

• Process of tying the band and untying the band
  • Band is tied into a knot; Client used a slipknot for easy tying and untying
  • Band is then used for exercises
  • Band sometimes came untied when not wanted
  • Band is untied as needed by undoing the slip knot
    • Band didn’t come undone as easily as expected; took one of the observers over a minute to untie the band

Qualities about Therapy Bands to see in our solution

• Therapy bands have some beneficial qualities about them now that we must try to retain in our solution.
  • Durability of current bands is very good
    • Client mentioned that they last a long time (several years if taken care of)
  • User friendly and versatile
    • Client explicitly stated that they would not use it if it was not user friendly
  • Average price for bands is currently ~$100 for 50 yards
    • Client mentioned that she would not be willing to spend much more money, if any, on a solution, along with the fact that the medical community does not appreciate change
• Priorities of user for a solution
  • Comfort
    • Client stated that they prioritize the patient’s comfort above all else
  • Time-saving
    • Client stated that time is extremely valuable, especially when they’re working with several patients at once and they’re, as our client put it, “tracking minutes”
  • Custom length
    • Needs to be able to adjust the length of the band with ease, preferably without the use of knots

User Observation Table

Purpose
The purpose of our user testing was to get user feedback on our mockups. Specifically we wanted to know if the size of our mockups was appropriate and if they would be comfortable. We also wanted to learn how quickly and how easily each mock up could be used to create a loop with the athletic band.

Methodology
Our team has run one round of testing with Dr. Goldberg. We presented him 3 of our mockups, one constructed of foamcore and the other two being 3d printed. These three mockups were our buckle design, as seen in Figure 1, our chip clip design, Figure 2, and a design we call interlocking, Figure 3. We presented each mockup to Dr. Goldberg and had him use it and give us feedback. The tests happened in our DTC room and lasted about 20 mins. One member of our team talked with Dr. Goldberg while the others took notes.

Figure 1: Buckle Mockup

Figure 2: Chip Clip Mockup

Figure 3: Interlocking

Results/Feedback

Buckle: We found that the buckle is very good at holding the band but it takes a long time to create a loop. It also takes a long time to adjust the size of the loop. The buckle in its current form is almost a more permanent fixture of the band.

Chip Clip: We found the chip clip was very simple and easy to use. It was also very quick. It slipped a bit more than the buckle design. The chip clip was a little large for Dr. Goldbergs liking. It kept the band “stretched out” while he was using it. The balance between flexibility and functionality will be an interesting thing to figure out.

Interlocking: We found that the intersecting design was very quick to create a band. It did have a problem that when tension is released, like it is in some exercises, the loop becomes undone. The mockup used in testing was also very bulky, and Dr. Goldberg wanted something smaller.

Conclusion
We found that in general our designs need to be smaller and more comfortable. This was especially true with the chip clip and interlocking design. They were simple too big. For the next iteration we need to make these smaller and attempt to make them out of more comfortable materials. We found that the chip clip and interlocking were both fairly quick and easy to use. The buckle design took way too long to weave the band through it. We are looking towards integrating this design more with the interlocking design.

Limitations
We were a bit limited on time when we did our testing. We had to make sure everyone else had time with Dr. Goldberg as well. We also could only have two of our members at the user testing for the whole time.

Purpose

Several design options that we created had unique advantages and disadvantages: the “grate” design held the therapy band most securely together, the “interlock” was extremely simple in use and the “chip clip” was fast. It was difficult to make a decision on which one should we proceed further with. We decided to focus more on the client’s mail expectations: comfort, quickness and easiness of the clasp usage. The objective of this performance testing was to determine to what extent does each design correspond to these factors to take the final decision.

Methodology

The quickness of use of each clasp was determined through measuring the time taken to connect, adjust length and disconnect the clasp from the therapy band. The data was collected from 3 persons, each performing the action 5 times, using the phone timer.

To determine the ease of use of each clasp, the “blindfold” test was used. During this test, each of the 3 persons attempted to connect the ends of the therapy band via each design. If the action was successful, then a design would pass the “blindfold” test.

To determine the comfort of each clasp, spring balance was used. Therapy band connected by each clasp and wrapped around a leg was pulled by the spring balance up to 20 N (Newtons) for 5 seconds. Then, each of the 3 participants rated the comfort they experienced on a scale from 1 (most comfortable) to 7 (least comfortable).

Measuring all the above factors for a knot on was included in the data collection for the sake of comparison because the aim of the project is to create a design that exceeds the knot in these parameters.

Results

Table 1 shows the calculated average time taken for each action for each design.

Table 1. Average time taken for connecting, adjusting and disconnecting the therapy band using knot and each clasp.

Table 2 represents the results of the “blindfold” testing for each of the participants.

Table 2. Results of the “blindfold” test.

Table 3 shows the average of the results of the comfort test.

Table 3. Results of the comfort test.

Conclusions and Limitations

From the data collected during the performance testing, following can be concluded:

1. Chip Clip is the fastest clasp, according to the time averages for its connecting, disconnecting and adjusting the therapy band length.
2. Chip Clip passed the “blindfold” test.
3. Grate did not pass the “blindfold” test because 2 participants failed to perform any action with it while being blindfolded.
4. Grate shown to be the slowest in use taking up to 60 seconds on average to connect the ends of the therapy band.
5. Comfort test did not show significant difference in results. It was decided to omit the results of this test as they were not helpful.

The last conclusion requires further research on how the comfort of each clasp can be measured in a more precise way. Based on other conclusions, it was determined that the “Chip Clip” design has the most advantage over simply tying a knot and over the “Grate” design. Hence, we decided to proceed with the “Chip Clip” design and make it our main project.

Bill of Materials

We also used Solidworks to model our design. Onshape.com and Fusion 360 are good free alternatives.

Please feel free to view the design concepts and technical drawings of our mockups at the following link: Team mockups