Ergo-Rest

"Ergo-Rest," the ergonomic violin shoulder rest that reduces tension in the upper and middle trapezius muscles in the left shoulder while playing. I have used electromyography to determine the effectiveness of the ergonomic implementations and additions in my design."

"The goal for my extended essay was to design an ergonomic violin shoulder rest.  As a violin player myself, I found it difficult to practice for long periods of time due to pain in my left shoulder from the pressure the shoulder rest put on it. The Ergo-Rest reduces this pain and allows for violin players to practice for prolonged periods of time."

Introduction

Overview

The Extended Essay (EE) is a mandatory component of the IB program where students research and write a 4000 word essay in an area of their interest.  This was the perfect opportunity for me to combine my interests of music and design.

 

Research Question + Abstract

This essay will focus on the investigation and development of an ergonomic violin shoulder rest that makes playing more comfortable and reduce stress and tension in the left shoulder. My research question “Having considered the relevant factors required prior to designing, how does one design an ergonomic violin shoulder rest?,” combines my passions for both design and violin as I designed a new violin shoulder rest. The presentation and format of the essay will follow the Stanford Design Cycle, a five stage model and design thinking process.

 

The final milestone was to produce an ergonomic shoulder rest that reduces stress and tension inside

the left shoulder. To achieve this, I first researched the fundamental aspects of shoulder rests and gained a better understanding of the biomechanics involved in ergonomic design. I then selected a target audience, sketched 10 designs and created a final design, created a CAD model and physical prototype of the final design and, tested and made adjustments.

 

Named the Ergo-Rest, I evaluated my prototype’s function of lessening tension in the middle and upper trapezius muscles utilizing two methods: an Electromyograph machine (EMG) and an interview with the subject. While the Ergo-Rest was successful in lessening tension in the middle trapezius, it did not

achieve the same result when tested against the upper trapezius, where it put more stress on the muscle.

 

Overall, further development of the product and improvements to the design process (e.g. testing of multiple prototypes) will be needed to fulfill all six design specifications.

 

Introduction

Problem

Practicing is a fundamental when it comes to developing and learning new skills and depending on your skill level, the amount of time spent practicing will vary. For those, such as myself, who practice on average between 2 – 5 hours, individuals start to become sore in certain parts of the body, raising concern for potential consequences in the long-run. Violin shoulder rests are considered to be ab essential for experienced and new violin players alike. Over a 9 year period of playing the violin, I have alternated between 4 types of shoulder rests. Primary concerns such as comfort and the ability to freely adjust the rest’s position and other factors, have led myself and other violinists to change the rest they use.

 

Objective

My goal is to design an ergonomic shoulder rest that lessens tension in the base of the left neck/shoulder muscles and meet other specific design specifications. Throughout the design process, I will be aiming to gain an understanding of product development and creating a

minimum viable product (MVP)

 

​​

Stanford Design Cycle:

The Stanford Design Cycle is a design and critical thinking method that is used to guide designers through project processes. I am using this particular design cycle to organize and structure my essay, as it is accommodating of coordinating long-term projects involving various iterative processes. This approach is designed for problem-solving, which is a suitable approach to my project as it focuses on developing a creative solution to relieve tension in the left shoulder of violin players. The Stanford Design Cycle is broken down into 5 modes and the structure of my project can be seen below:

● Empathize = Research shoulder rests (current solutions to the problem),

biomechanics, evaluation methods to test my designs and observe/gather data

on potential clients/audiences (violinists of different levels and ages).

● Define = Reflect back on research to select a specific target audience

and simplify the problem to produce a specific research objective

 

● Ideate = Sketch 10 designs with 3 views (3D, top & side), narrow down

to 3 designs (further develop the ideas) and select final design(s) for prototype

● Prototype = Produce a computer-aid design model (CAD) and physical

prototype of the final design

 

● Test = Using previously researched evaluation methods, gather data

and make the necessary revisions/adjustments to the prototype.

Empathize

 

Prior to designing my own rest, further knowledge about the structure of the violin and other shoulder rests must be acquired.

Violin Anatomy

An understanding of the violin’s structure will give the designer ideas of the optimal areas where the shoulder rest can make contact with the violin without altering the sound produced by the instrument while playing, as well as specific dimensions. A majority of shoulder rests latch onto the lower bout of the violin and are typically 8” in length, which is the width of the lower bout of the violin

Different Types of Shoulder Rests + Primary Research

Understanding the different functions of the parts of traditional shoulder rests assists in determining which components will serve the ergonomic functions of my design and contribute to maintaining the accustomed image of a shoulder rest.

 

I researched and tested the Everest, BonMusica, Kun (for full size violins) shoulder rests and a classic sponge. For current ergonomic-focused solutions, I researched the Phantom shoulder rest. Kun and Everest rests are known as “traditional rests” due to their structures, where the curved bodies position and similar components, such as having 2 layers - a 1/4” wood/plastic layer and underneath, a 1/4“ foam layer. Regarding dimensions, their lengths mimic the width of a full size violin, 8.” Aside from the sponge, all rests were composed of similar materials including wood, plastic, metal (nuts) and rubber, which are known to minimally absorb sound. These functions and dimensions will be taken into consideration while designing my rest.

 

Below are sample images of my research notes and a summary of my findings.

Player Interviews + Specific Target Audience

I asked five violin players of various skill levels (RCM grades 5, 7, 9 and 10) and found that the grade 5 players practiced on average for 1 – 1 . hours while the more advanced players practiced between 2 – 5 hours. An appropriate target market for a ‘customized’ shoulder rest is one that will use it and a practice for long periods of time. Typically, more advanced players are older and in addition, older players have most likely stopped growing, meaning they will no longer have to switch rests due to having to switch to a larger violin. I have chosen to primarily target teenagers and adults who play at a higher/more competitive level, where practice lengths range between 1.5-3 hours.

 

By implementing innovative ergonomic solutions into my designs, it will permit the player to play for a longer period of time comfortably and lessen the pressure applied to the trapezius muscles. While the primary target audiences are competitive violin players, less experienced players who would prefer to use a shoulder rest that will have less of a negative impact on the body, may use the solution as well.

 

Older and more advanced players generally use full-size violins, the largest size available, meaning that once players reach a certain height and wingspan, they will continue to use a full-size regardless if they grow any more and therefore will not have to purchase a differently sized shoulder rest. Hence, I have chosen to design a product for more advanced players, who utilize a full-size violin and practice for 2+ hours.

Biomechanics

Through observations while practicing, I found that the tension in certain parts of the shoulder becomes more apparent after 1.5 - 2 hours.

 

Stress vs. Strain → This project looks at how the application of applied loads affects the

muscles in the body. In biomechanic terms, applying an external force is referred to as loading the body, where the applied load creates internal forces on the material within the body called stress.

 

Deformation and changes in length in the materials in the body is a potential response to stress, known as strain. The amount of strain developed in the material determines whether the ligament will be sprained or in the case of muscles and their attached tendons if they will be categorized as a pull, strain or tear.

 

Symptoms of muscle strain include redness, swelling, pain at rest or pain when a specific

muscle or joint in relation is used (WebMD, 2005). To identify the possibility of strain being an

issue, myself and two friends looked for these symptoms after a 2 hour practice. We compared the researched symptoms to our observations where redness, pain when the muscles were used and stiffness at rest, were the three most common symptoms. While they did not remain for a long time, this is evidence of possible injuries or damage to the muscles in the long-run.

 

The ergonomic objective of my shoulder rest is to reduce this tension in the left shoulder, located in the upper and middle trapezius muscles (See Figure 5), as general shoulder rests put a great quantity pressure on these specific parts of the trapezius muscle.

Evaluation Methods + Professional Opinion (LIVELab at McMaster University)

I will use 2 evaluation methods for my prototype during the comparative user testing process:

● Interview & observations/Q&A (Tester)

● Electromyograph Machine (EMG)

 

Interview & Observations →

When evaluating ergonomics and comfort levels, a frequently used evaluation method is observing and asking the test subject(s) questions. I will ask the test subject questions during the test using an EMG machine and also ask the subject to answer

questions following a 2 hour violin practice, to evaluate the comfort levels over a longer period of time.

 

Electromyograph Machine (EMG) →

In the summer of 2017, I attended LEAP, a STEM summer camp at McMaster University where I met Dr. Ian C. Bruce, the associate director of the LIVELab, a unique performance hall designed research the experience of music, dance, multimedia presentations and human interaction. My camp group toured the facility and learned how the biomechanics of movements were tracked using motion capture cameras and other specialized equipment. I asked the professor about cost-efficient evaluation methods

regarding the ergonomics of the Ergo-Rest’s design and he recommended an Arduino EMG machine.

 

EMG machines detect and record the electric potential generated by muscle cells when activated. By attaching electrodes where the upper and middle trapezius muscles are located in the left shoulder, I will be able to collect quantified muscle tension values by reading graphs produced by the EMG machine. The larger the readings, the more electric signals and hence the more stress on the muscle and vice-versa. Surface electrodes have the ability to gather speed and strength readings of the muscle, enough to evaluate my prototype’s ability to lessen tension.

Define

 

Design Specifications

Six design specifications will be the standards for the evaluation of the final product:

● Have a minimum of two ergonomic applications from researched shoulder rests

● Materials must not obstruct/muffle the sound

● Correct posture so that the scroll of the violin is as parallel as possible to the ground

● Have visual aspects of the traditional rest that will allow the rest to not look bulky or

stick out too much from under the violin

● From the EMG readings, the design should show that it causes less stress on the

shoulder than two of the rests I have researched

● For individuals who play more frequently and use a full size violin

Ideate

Design Process

I created 10 designs, then narrowed them down to five, then three and created a hybrid. Each design is shaped differently, and experiments with features such as the distance of the rest’s lower component from the back of the violin, which ultimately affects the rest’s height, locations of the fork members and the number of components it consists of.

Prototype

 

Final Design: Ergo-Rest

I sketched my final design and created two CAD models in Sketchup. This final design is a hybrid of various features from design 4, 8 and 9

The overall shape and bottom component consisting of a curve that rests directly on the shoulder was inspired by design 4. This ‘hook-shaped’ curve stems from the idea where the component is shaped a certain way, allowing the user to reposition or change the angle of the violin while playing, without applying additional pressure with the chin. The design primarily combines designs 8 and 9, where the shape of the sponge in the bottom component, is a hybrid of the sponges in both designs. This component covers a larger surface area than traditional rests, and distributes the downward, applied pressure from the chin to the entire shoulder.

 

The Ergo-Rest is primarily composed of inexpensive polypropylene plastic for the body, (similar to the material used in Everest rests), rubber for the fork members, and a durable, engineered-foam material that does not disintegrate, in place of the sponge in the lower component.

 

In terms of market potential, the Ergo-Rest comes in an assortment of colours, appealing to younger audiences and also grey and black for adults who prefer subtle looks. The individual parts can are replaceable by either screwing (e.g. fork members) or snapping them into place (lower component to the upper component of the rest).

 

The length and height of the Ergo-Rest, were based on the Everest shoulder rest and the dimensions of the bottom component were based on the measurements of my subject’s shoulder. The shoulder rest is also collapsible as the fork members can fold downwards, allowing for easier storage. Regarding aesthetics, the bottom component remains hidden, while playing. Since my first CAD model did not clearly portray certain features such as

the collapsibility of the fork members or the curved plank component, I created a second CAD model.

Prototype (MVP)

After seeing that 3D printing was time-consuming and expensive, I visited various stores such as Home Depot, Michaels and Dollarama to look for alternative materials. Due to limited resources and time, which resulted in a rapid prototyping process, I constructed a minimal viable product (MVP), of 3 headbands, 2 fork members of a FOM shoulder rest, an 8” x 3.5” x 0.75” piece of balsa wood, 2 sponges, nuts, duct tape and white glue. I spent a total of five days constructing the prototype.  Once the construction of my MVP was completed, I took it over to my friend who volunteered to test it, where we fitted it onto her violin and through observations, found what would need to be adjusted.

Test

Following the major adjustments, I tested the prototype through comparative user testing, which involves having the user(s) compare two different designs (Loop11, 2015). I recorded my friend playing an ascending G major scale on the violin, using both my prototype and an Everest shoulder rest. She had 2 electrodes attached above the middle (first test) and upper trapezius muscles (second test), and one on the elbow, to ground the charge.

Electromyography, Electromyograph Machine (EMG) readings + Analysis

By screen recording the Arduino Serial Plotter tool’s EMG readings, I performed a biomechanical comparison between my shoulder rest and the Everest rest. The areas highlighted in yellow in the screenshots of the readings below are the results at the first string crossing point (G to D string). String crossing applies additional weight to the shoulder due to the change in the bow’s angled direction of movement.

The EMG Machine has a 9600 baud rate, the rate at which information is transferred in a communication channel. In this case, a maximum of 9600 bits per second can be transferred. From the EMG readings, the levels of activity in the muscle can be identified by analyzing the amplitude differences and frequencies of the waves. The amplitude differences between each period of a single muscle represent the varying levels of its activity. The more strength required of it, more additional motor units will be added and hence, the EMG signals visually have larger amplitudes and become denser/tightly packed together .

Everest

Ergo-Rest

Middle Trapezius

Upper

Trapezius

After analyzing the collected data, the Ergo-Rest was successful in lessening tension in the middle trapezius. However, it did not successfully fulfill its goals in lessening tension in the upper trapezius as well. One noticeable feature of the EMG readings for the middle trapezius is that the Ergo-Rest seems to lessen the tension significantly during string-crossing in comparison to the Everest, where the tension remained higher for a long period of time (extending past the duration of the string crossing). In terms of the upper trapezius evaluation, the readings were larger for the Ergo-Rest in comparison to the Everest. However, when Natalie crossed from the G string to the D string, there was less of a response and the muscle’s activity did not spike, as it did use the Everest Rest. Overall, the Ergo-Rest provided results that exceeded expectations as an MVP and if a higher quality prototype was constructed, feedback would be more fitting.

Interviews With Test Subject

Interviews were conducted on two occasions: Directly after the EMG test and after the subject practiced for 2 hours. Following the EMG test, I proceeded to ask her questions about my prototype. While it is clear that she preferred the Everest to the Ergo-Rest, she stated that her opinion is biased as she is used to the Everest and it would take more time to adjust to the Ergo-Rest as the feeling is different in terms of

support, the violin’s position and the surface area it covers on the shoulder.

 

For the second test, which happened a week later, she practiced for 2 hours with the Ergo-Rest and answered questions I previously prepared, where she stated that visually, there were fewer marks left on the skin by the Ergo-Rest in comparison to the Everest. She also said that using

the Ergo-Rest made the shoulder feel less sore, but stiffer in the neck

Areas for Improvement for Final Prototype

One major area for improvement is to change the materials I used. While the materials I used were cheaper and easily attainable, some choices limited the types of modifications I wanted to make (e.g. Being unable to bend a plank of wood). These materials were suitable for the iterative approach my project followed, but to produce the best final product, I needed to use higher quality materials. I was unable to freely adjust the height of the Ergo-Rest and if I had been able to substitute the wood plank with a 3D printed component instead, the results of the

data collection for the upper trapezius may have been more accurate.

 

In terms of the design thinking and planning process, I wish I checked in more frequently with my subject during milestones and iterations, as I did spend longer than expected making the necessary adjustments to my MVP/prototype. In relation to the Empathize step, building it alongside her would have resulted in less adjustments that would take less time. Overall, research and development project should be conducted over a longer period of time with multiple subjects and prototypes. Testing multiple designs against one another would have allowed me to gather more obective data.

Evaluation Against Design Specifications

The first specification has been met as I have implemented ergonomic applications into the shape of the bottom component and the fork members, where the fork members can be slightly adjusted and move side to side, allowing for the user to comfortably position the shoulder rest at their preferred angle, ultimately correcting posture. Second, the fork members allow for some distance between the rest and the back of the violin, which does not obstruct or muffle the sound in any way. Third, the main materials used are plastic and rubber, which keep sound absorption to the minimum. Fourth, the shape of the upper component of the Ergo-Rest was inspired by the traditional rest, as its thin shape allows it to be easily concealed underneath the violin. Fifth, the rest is appropriate to be used by various audiences, as shown by my test subject, who is an advanced violinist. Sixth, the Ergo-Rest has been able to reduce the stress in the middle trapezius, but increased the stress in the upper trapezius. Hence, five of six specifications have been met.

Conclusion

In conclusion, the shoulder rest was successful in lessening tension in the middle trapezius, but it was as if some of the stress had transferred into the upper trapezius. From the EMG readings, the overall stress induced by the Ergo-Rest is less than the Everest rest as there was a larger decrease in stress in the middle trapezius than the amount the stress increased by in the upper trapezius. The Ergo-Rest has met four out of the five criteria/design specifications and if the project is continued, a better prototype will be made (e.g. 3D printed), to help produce

better and accurate readings.​

In society, new innovations may solve problems, but create new ones as well and individuals may not be accepting of change. In the case of the Ergo-Rest, the upper trapezius problem remains unsolved and the shape of the rest itself deviates from the traditional image, but

further development of ergonomics will spark a new age of violin shoulder rest designs.

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