Design, Analysis and Evaluation ofa Passive Augmentation Suit for Freestyle Swimming

Federico Parietti, Austin de Maille, Yi Tong and Borui Wang

Abstract— This paper presents a novel passive suit designedto augment swimming capabilities during the freestyle stroke.The suit consists of passive elements attached to the hip andthe elbows of the swimmers through a system of straps. Thepassive elements store elastic energy when the arms move inthe air (low load), and release it when the arms are in the water(high load). This allows the passive elements to shift some loadfrom the muscles that are mainly responsible for propulsion,to muscles that would not be normally fatigued during thefreestyle stroke. The underlying assumption is that efficientlyredistributing the load on a wider range of muscle groups willreduce fatigue, increase speed or reduce the metabolic cost offreestyle swimming. In this study we detail the choice of passiveelements and their effects on the swimming stroke. We thenquantify with experiments the effects of the suit on swimmers,identifying the advantages and the areas of improvement forthis augmentation strategy.

I. INTRODUCTION

Swimming has become a more and more popular recre-ational sports in the world. Although human beings havedeveloped several classic swimming styles over the yearswhich are highly optimized in terms of sports biomechanics,there is still a lot of room for potential improvement becausethe distribution of kinematic burden over different musclesare significantly uneven in these swimming styles. In orderto help swimmers more efficiently utilize biological energyduring swimming and to enhance their swimming experience,we decided to design a new type of passive exoskeletonswimsuit that could redistribute kinematic burden moreevenly across multiple critical muscles and thus raise theswimming efficiency of the wearer. In this project we willfocus on dealing with freestyle swimming.

Our basic strategy is to exploit the energy-loading oppor-tunity during the recovery phase of freestyle swimming. Thisstrategy has been first proposed in [1]. We place a passiveelastic element between upper arms and thighs, which shouldideally be within the appropriate range of elasticity whilehave a damping coefficient that is as small as possible. Sucha passive elastic element will store energy when the armsis moving in the air during the recovery phase and thenrelease a large portion of this stored energy to facilitate themovement of the arms underwater during the more difficultand energy-consuming pulling and pushing phase.

F. Parietti and A. de Maille are with the Department of MechanicalEngineering, Massachusetts Institute of Technology, Cambridge, MA, USAparietti at mit.edu, demaille@mit.edu

Yi Tong is with the Department of Computer Science, Wellesley College,Boston, MA, USA ytong@wellesley.edu

Borui Wang is with the Department of ComputerScience, Harvard University, Cambridge, MA, USAboruiwang@college.harvard.edu

Fig. 1. Material characterization experiment (left) and collected data (right).

Our goal is that by wearing our exoskeleton device, theswimmer would be able to: (1) reduce fatigue; (2) improvingswimming speed and endurance; and (3) reduce metaboliccost. We will conduct detailed experiments to test our hy-pothesis, which will be discussed in the second half of thepaper.

II. MATERIAL CHARACTERIZATION ANDANALYSIS

Our first task in the design and manufacturing stage is tofind the most appropriate type of material that we would useto build the elastic connector in our exoskeleton. In orderto determine the right material to use, we conducted springoscillator experiments on four distinct types of materials:latex tubing, silicone, bungee cord and steel spring, and forlatex tubing we also further tested four different subtypes.The data we collected from these experiments will allow usto numerically calculate the elastic and damping propertiesof these different materials.

We first use a heavy metal clamp to fix the upper end ofthe material, and then attach a 5 lb weight to the lower endof the material. We first measure the natural length of thematerial and then allow the system to stretch to its naturalposition against gravity. The elongation displacement of thematerial will allow us to calculate the elastic coefficient ofthe material using Hookes Law.

Next, we stretch the weight end of the material downto a certain height and then release the system as a springoscillator. The weight will oscillate up and down around thesystems equilibrium position until the kinematic energy ofthe system is completely dissipated through damping. Weplace a high-speed digital camera on the side to film thiswhole oscillation process.

Fig. 2. Identified parameters (stiffness constant k and damping coefficientb) for the considered materials.

We then used a tracking software to analyze the movementof the weight in the video. This will give us the oscillationplot of the system as shown in Figure 1.

We then isolate the peaks of each oscillation cycle, use anatural log transformation to linearly fit the curve, identifycoefficient of exponential decay, and then calculate thedamping coefficient.

The final results our of experiment and calculation arepresented in the Figure 2.

Since our criteria of choosing material for our passiveelastic connector is to have a comfortable elastic coefficientwhile minimizing the damping coefficient, we decided to usethe new small latex tubing as our material because its elasticcoefficient (97 N/m) is within human beings comfortablerange and its dambing coefficient is quite small (only 0.7N*s/m). Another advantage is that it is also very easy tomanufacture our exoskeleton device with latex tubing.

III. SWIMMING STROKE ANALYSIS

In this section, we will analyze the structure of a freestyleswimming stroke, and identify potential for augmentationby using a passive element. An experimentally recordedtrajectory of this stroke will then be quantitatively studied,considering in detail the energy contributions associated witha spring-damper with the properties of latex tubing.

A. Freestyle Swimming

Freestyle is a kind of swimming competition in whichswimmers are subject to limited restrictions on their swim-ming stroke [2]. The stroke used almost universally infreestyle races is the front crawl. As a consequence, theterms freestyle and front crawl are often used as synonymous,with the former being much more diffused among the generalpublic. For simplicity, in this paper we use the more commonterm freestyle to refer to the front crawl.

We chose to develop a suit that augments the freestylestroke for three reasons. First, this stroke is the most widelydiffused. It was possible to contact a large number of

undergraduate and graduate swimmers which had compet-itively raced in freestyle, or that were used to swim infreestyle every week. If we selected any other common stroke(breaststroke, backstroke or butterfly), the pool of expert testsubjects would have been greatly reduced. The second reasonis that freestyle is the fastest stroke, and also the strokemost commonly used in endurance competitions. This strokegave us the opportunity of testing the benefits of the useof passive elements both in terms of speed and in termsof endurance. The third reason is that freestyle swimmingpresented a significant opportunity for augmentation. As wewill point out in the following paragraphs, this stroke is basedon a cyclic motion of the arms with an unloaded movementforward, and a loaded movement backwards. It is thereforenatural to use a passive element to balance the load betweenthese two phases.

The freestyle stroke has three components: the startingposition, the arm movement and the leg movement. In thestarting position, the swimmer faces the bottom of the poolwhile both arms are stretched to the front and both legs areextended to the back. The movement of the arms (Figure 3)is divided into an underwater phase (pulling and pushing),and in a phase out of the water (recovery). When the armreaches the water, pulling starts. It consists of a semicircularmovement from the water level to the chest, in which thearm is kept straight. After the pull, the push starts. In thismovement, the arm of the swimmer is pulled back up to waterlevel, ending at the side of the body. At this point, recoverytakes place in order to bring the arm back to the startingposition. The elbow is moved in the air towards the front ofthe body, while the forearm and the hand are relaxed. Themovement of the legs consists of simple alternating kicks.One leg moves downward, while the other moves upward.The legs bend slightly at the knee before going downwards.

The freestyle stroke involves a large number of muscles(Figure 4). These muscles can be divided in two groups:primary muscles which bear the largest loads, and secondarymuscles which are only marginally involved in the swimming

Fig. 3. Arm movement in the freestyle stroke. Pull/push inside the water(top) and recovery outside of the water (bottom).

stroke. The primary muscles are mainly located in the upperarms, and include biceps, triceps and deltoids. The freestylestroke presents an evident opportunity for augmentation be-cause of the asymmetry of the arms movement. In the initialunderwater phase (pulling/pushing), the arms are heavilyloaded and fatigue rapidly. Conversely, in the recovery phasethe arms move outside of the water, and muscle forces arevery low. It should therefore be advantageous to shift partof the load from the muscles involved in pulling/pushing tothe muscles involved in recovery. This can be achieved bymeans of a passive element which is stretched when the armis moved forward (recovery) and then helps the swimmerwhen the arm is moved backwards (pull/push).

In order to augment freestyle swimming by shifting theload from pull/push to recovery, a promising passive elementlocation is the one going from the hip to the elbow of theswimmer. A passive element that connects these two pointswould be stretched when the arm is in the air (movingforward), and help the swimmer when the arm is in thewater (moving backwards). Attaching the passive elementto the wrist instead of the elbow would be disadvantageous,because the arm is never perfectly straight during the swim-ming stroke. This means that a passive element starting fromthe wrist would force the triceps to be constantly active (evenin the underwater phase), in order to prevent the arm fromfolding back on itself.

In the following section, we will quantitatively analyze thefreestyle swimming trajectory and the energy contributionsthat a passive elements would bring to it.

Fig. 4. Primary (red ellipses) and secondary (black ellipses) musclesinvolved in the freestyle stroke.

Fig. 5. Tracking experiment to measure the swimming trajectory (top) andidentified trajectory for the elbow and the hip (bottom).

B. Effects of the passive element on the freestyle stroke

In order to quantify the contributions of linear passiveelement attached to the hip and the elbow of freestyle swim-mers, we recorded the trajectory of these two anatomicalpoints during the swimming stroke. Figure 5 shows themeasured trajectories (over 5 complete periods) in a two-dimensional plot, where axis x is parallel to the body ofthe swimmer (with the positive direction pointing towardsthe feet) and axis y is perpendicular to it (with the positivedirection pointing outside of the water). These data wereextracted from a video using a tracking software, and aretherefore 2D data. This limitation simplification will notcompromise the results of our analysis, because most of thefreestyle stroke motion takes place in the sagittal plane (planexy in our reference system). The video was shot outside ofthe water to avoid distortion effects caused by diffractionwhen recording the motion of a swimmer in the pool. Thesubject of the video had been a trainer for the freestyle strokewhile in high school.

The two trajectories shown in Figure 5 are the motions ofthe hip and the elbow of the swimmer. We hypothesize thatthe passive element is linear and attached to these two points.Figure 6 shows the length of a passive element joining hipand elbow during the considered 5 periods of freestyle stroke.It can be noticed that the passive elements starts at a stretchedposition (the initial position of the stroke), and then quicklycontracts as the arm moves backwards underwater. Then, asthe arm is moved forward in the air, the passive elementis stretched back to the initial length and then stays there(with the arm fully extended forward) until the beginning

Fig. 6. Length and percent stretch of the passive element during freestyleswimming. Blue curves consider a theoretical passive element without slack,red curves consider the actual passive element with slack and limited stretch.

of the next period. This cyclic unloading (in water) andloading (in air) of the passive element is what we intend toexploit in order to redistribute muscular loads and augmentthe swimmer.

Figure 6 also shows the percent stretch of the passiveelement. The definition of percent stretch is:

%stretch =L− Lmin

Lmin· 100 (1)

The blue trajectory is calculated in the case of an elementwhich is at rest (0% stretch) when the elbow is closest to thehip. Such an element would need to stretch to almost 900%of its rest length in order to remain attached to the elbow ofthe swimmer throughout the whole trajectory. This value forthe maximum extension vastly exceeds the maximum safestretch for the latex tubing, which is 533% (measured inthe lab using the selected latex tubes). This problems canbe addressed by adding some slack in the passive elementtrajectory. In other words, the element is longer than theminimum distance between elbow and hip. This way, theelement will produce a zero force until its rest length isreached. At the same time, being a longer element it willhave a smaller percent stretch. The minimum length thatthe passive element must have in order to have a maximumpercent stretch of 533% on the measured trajectory is:

533 =Lmax − L0

L0· 100

⇒ L0 =Lmax

6.33(2)

Plugging in Lmax = 0.87m, the desired value for thelength of the passive element is L0 = 0.14m, whichcorresponds to a slack of 0.05m (the minimum distancebetween elbow and hip is 0.09m). This passive element withslack never exceeds its extension limit (see Figure 6, redtrajectories).

We can now compute the forces exerted by the passiveelement on the swimmer. The passive element is modeledas a parallel spring damper, where spring force and damper

Fig. 7. Elastic force and damping force exerted by the passive elementduring freestyle swimming.

force are linearly related respectively to the stretch and to thestretching velocity of the passive element. The expressionsof these two forces are as follows:{

Felastic = k ·∆L

Fdamper = −b · L̇ (3)

Figure 7 shows the plots of the spring and damper forcesduring the swimming trajectory. Notice that the passiveelement with slack, though limited to lower forces, is stillable to reach 94% of the maximum force provided by atheoretical passive element without slack. It is also importantto observe that the damping forces are much lower thanthe elastic forces. This means that the selected materialis suitable for this application (the damping coefficient islow enough to generate scarce damping forces, even in thepresence of fast arm motions such as the recorded ones).

When evaluating the effects of the passive element on thefreestyle stroke, we are particularly interested in the elasticand dissipative (damping) energies that come into play. Theseenergies are defined by the following expressions:{

Eelastic = 12k ·∆L2

Edamping =∫ t

0

∣∣∣Fdamper · L̇∣∣∣ dt (4)

Figure 8 shows the plots of elastic and dissipated energyduring the considered swimming trajectory. In every period,the elastic energy which is stored and then released amountsto 24J . Notice that the passive element with slack is able tostore 88% of the elastic energy which would be stored by apassive element without slack. The energy dissipated in everyperiod is about 1.5J. This means that the dissipated energy isonly 6% of the energy which is stored and released in everyperiod. This limited energy dissipation is very promising,

Fig. 8. Elastic energy and damping energy exchanged by the passiveelement during freestyle swimming.

because it means that the passive element is very efficient intransferring load from the muscles used in recovery to themuscles used to pull/push the water.

Since this theoretical analysis gave interesting results, weproceeded with the realization of a swimming augmentationsuit based on linear passive elements (the selected latextubes) attached at the elbows and hip of freestyle swimmers.

IV. METHODS

A. Exoskeleton Swimsuit Fabrication and Design

1) Key Requirements and Storage Element MaterialChoice: When building the exoskeleton swimsuit, therewere several key design requirements to consider. First, aspreviously mentioned, the suit needs to allow for energystorage on the arms recovery phase when it is out of thewater. This would allow less human energy needed to pushthe arm through the water. The material used as the energystorage element will therefore also need limited energy loss(minimum damping). In addition, the constant repetitiveforces put on device requires the design and choice ofpassive element to be very durable. Considering all theserequirements, the latex tubing with stiffness of 97 N/m anddamping coefficient of 0.9 N*s/m was chosen as the passivestorage element. Of all the materials analyzed, it has the bestbalance between resistance, limited damping, and durability.

Finally, the overall design of the exoskeleton suit must beboth customizable and comfortable. It must be customizableso that people of all body types can wear it. The exoskeletonsuit must be comfortable simply because if it gives discom-fort, it will never be worn.

2) Overall Design: A picture of the overall design of theexoskeleton suit can be found in Figure 9. As an overview,the design consists of nylon straps around the upper thigh and

upper elbow. The latex energy storage elements connect thesenylon straps via hooks and a 3D printed part. A bodysuit isworn underneath the nylon straps.

3) Nylon Straps: Adjustable nylon straps are worn aroundthe arms and legs. Straps worn around the upper thigh are 1.5inches thick. Straps worn around the arm above the elbowand below the bicep are 1 inch thick. Strap length around thelimbs is adjusted using a ladderlock buckle. Sleeves aroundthe straps allow the extra length of the nylon strap to betucked away. Without the sleeve, the straps would dangleand lead to additional unnecessary water resistance.

4) 3D parts: 3D parts are used to connect the hooks ofthe latex tubing passive element to the nylon straps. The 3Dparts are placed over the strap and are fixed in place with aset screw. There is a hole where the passive storage elementhook can attach. When wearing the suit, the 3D parts onthe arm straps are placed on the triceps with the hole facingtowards the upper arm/shoulder. The 3D parts on the thighstraps are placed on the back of the hip with the hole facingtowards the torso. Refer to Figure 9.B to view the 3D partorientation on the human body. In addition, a close-up viewof the 3D part can be found in Figure 10.A.

5) Passive Elements: The passive elements connect thethigh and arm straps. They are manufactured by inserting ametal bungee cord hook around the tubing. The hooks are setin place by folding the latex tubing over. The tubing is thenclamped down via self-made compression sleeves which arecomposed of steel sheet metal and duct tape. This designensures that the hooks will not fall off. A close-up picture ofthe hook and compression sleeve configuration is displayedin Figure 10.C.

The length of the passive elements vary in size based onthe height of the swimmer. During testing, subjects under 56used latex tubing that was 15cm long. Subjects from 56 to510 used tubing that was 17.5 cm long and subjects above510 wore tubing that was 20cm long. A picture of the varyinglengths of tubing can be found in Figure 10.B.

Fig. 9. Left: front view of the exoskeleton swimsuit. Right: Side view ofthe exoskeleton swimsuit. Take notice of the 3D part positioning.

6) Bodysuit: A standard swimming body suit is wornunderneath the nylon straps and latex tubing. This is used togive padding between the human body and the straps. Thesuit helps limit discomfort, specifically the redness causedby the friction between the straps and the skin.

B. Experimental Methods

In overview, 5 subjects performed three different exper-iments that tested freestyle swimming speed, swimmingendurance, and post-workout fatigue. Subjects swam in a 25yard length pool with lifeguards always present. As a control,all subjects swam without the passive element exoskeleton.They then swam with the exoskeleton. During swimmingtests, swimming speed and heart rate were measured. Inthe fatigue test, the time to hold a weight until failure wasmeasured.

1) Subjects: Five subjects were contacted for this study.All five subjects are students at the Massachusetts Instituteof Technology. They ranged from the ages of 19-28 andboth sexes (2 female, 3 male) were represented. Subjectswere recruited based on their previous swimming experienceand were asked a series of pre-test evaluation questions thatdetermined whether or not they were experienced enough toparticipate in the experiment.

All subjects swim on a regular basis, swimming at leastonce a week. Four of the five subjects swam competitively,three of those four swimming competitively up through highschool. With this level of swimming experience, these subjectwould be able to give consistent results that would moreaccurately determine if our exoskeleton device had beneficial

Fig. 10. A: close-up view of the 3D part that allows the hook of the energystorage element to attach to the nylon strap. B: the varying length of latextubing storing elements. 15cm on top, 17.5cm in middle, 20cm on bottom.C: A close-up view of the assembly of the hook and compression sleeve onthe latex tubing.

Fig. 11. A: Test subject holds a five pound weight over the head while lyingon the back to measure fatigue in the muscles used in propelling the bodythrough the water. B: Subject holds a ten pound weight over the shoulderto measure fatigue in muscles used during the recovery phase of freestyleswimming.

effects on freestyle swimming speed, swimming endurance,and post-workout fatigue. In addition, these five subjectswould be people that could wear this exoskeleton deviceregularly for swimming activities if it deems beneficial.

2) Testing Layout: Testing consisted of two days ofexperimentation. On the first day, subjects swam while onlywearing the black bodysuit. This was done to acquire acontrolled baseline. Subjects initially participated in the highperformance swimming test. Subjects were given a breakuntil they felt fully recovered. Subjects then participated inthe endurance swimming test. Once complete, subjects tookoff the bodysuit and immediately performed the fatigue test.No break was provided because measurement of exhaustionimmediately following swimming was ideally desired. Sub-jects were given four days rest from swimming to ensure thatfatigue from the first day would not affect the second day oftesting. During the second round of testing, the exoskeletonswimsuit suit was worn. Tests were performed with the exactsame procedure protocol as the first day.

3) High Performance Swimming Test: In the high perfor-mance swimming test, subjects were tested on their abilityto swim at high speeds. The five subjects swam 100 yards(4 laps) as fast as possible. The time it took to swim thisrelatively short distance will help gauge the subjects abilityto swim at peak performance. The hypothesis is that peakswimming speed will increase while wearing the exoskeletonsuit.

4) Endurance Swimming Test: In the endurance swim-ming test, subjects were tested on their swimming stamina.The five subjects swam 300 yards (12 laps) with the goal ofmaintaining a constant speed. The time it took to swim eachlap as well as the entire 300 yards will help determine thesubjects swimming stamina. The hypothesis is that swim-ming endurance will increase while wearing the exoskeletonswimsuit.

5) Fatigue Test: In the fatigue test, the amount of fatiguewas measured in the arm muscles used in swimming. Twotests on each arm were performed. The first test measured thefatigue of muscles used to push oneself through the water.As shown in figure 11.A, subjects held a five or ten poundweight straight out above their head until failure. The secondtest measured the fatigue of muscles used during the recoveryphase of freestyle swimming when the arm was out of the

water. As shown in figure 11.B, subjects held a five or tenpound weight over their shoulder until failure. The weight aspecific subject used during the fatigue test was held constantthroughout the two days of testing.

Ideally, we expect that by using the exoskeleton swimsuit,time until failure will increase when holding the weight whilelaying down (aka the muscles that push through the water areless tired) and time until failure will decrease when holdingthe weight behind the shoulder (aka the muscles involved inthe recovery phase are more tired). This would indicate thattransfer of muscle energy use was achieved.

6) Measurements: As previously mentioned, swimmingspeed was measured in both swimming tests by recordingthe time it took to swim every lap of the pool (25 yards).The average and maximum heart rate were also measured ineach of the swimming experiments. It should be noted thatwe originally planned to use a heart rate sensor that activelylogged the subjects heart rates throughout the experiment.The manufacturers said this device would work in water, butthe device proved to not hold up this claim. Thus we hadto use a heart rate sensor that would only log average andmaximum heart rates for any given single trial.

In the fatigue test, the time to hold a weight until failurein the two different arm positions was measured. Controland experimental tests would be compared and analyzed todetermine if wearing the suit helped decrease post-workoutfatigue.

V. RESULTS

The results of the experiments are analyzed in detail inAppendix A. Here follows a summary of the most importantresults:

1) The use of the passive suit made the swimmers slowerby an average of 2.27 seconds per lap (around 10% slowerthan swimmers without the passive suit).

2) The effect of the suit seems to be similar on all laps(both the first and the last ones).

3) Fatigue levels with the suit are not statistically differentfrom the levels without the suit. We observed a qualitativedecrease of fatigue in the pull/push muscles (the muscleshelped by the passive element) and an increase of fatiguein the recovery muscles (the muscles used to stretch thepassive element). However, these trends were not statisticallysignificant. This was probably due to the limited amount ofexperimental data.

4) Heart rate levels with the suit are not statisticallydifferent from the levels without the suit. As before, itseemed that the suit led to a decrease in average heartrate. However, this was not statistically significant and moretesting is required in order to achieve a definitive result.

VI. CHALLENGES AND FUTUREIMPROVEMENTS

A. Material

In future development, more research and testing willfocus on the various materials for the spring system, thecinching strap, and the 3D printed part, because they could

largely affect the performance and endurance of users. Withmore suitable material, the suit could be more comfortable,more endurable and cause less side effects.

The spring system could use materials with less dampingand stiffness . The current prototype uses a latex tubing witha stiffness of 97N/m and damping of 0.9 N/(m/s). Whilethe percentage of dissipated energy per period is as low as6%, users reported increased difficulty while extending theirarm. Unlike silicon, latex tubing or metal spring, combinedmaterials like metal spring coated with silicon or rubbercould be used to lower the damping and stiffness while stillbeing resistant to water. Besides damping and stiffness, theendurance of the material is also important. The latex tubinggot small cracks on the surface after a single testing(as figurex shown). Since the spring system is designed to be stretchedrepeatedly in the water, we will need a more durable material.Further study of the materials used in swim trainer machinescould also be beneficial.

The cinching straps on the arms and legs work quitewell. However, even with the swimming suit between theaugmented parts and skin, users still reported skin irritationcaused by the polypropylene straps rubbing against the armduring strokes . The straps could be sewed onto the swimsuit so that it will move around. It could also be replacedwith a more flexible material so that it sticks to the suit withfriction while still being soft enough to not irritate the skin.The 3D printed part could be downsized and wrapped in asoft material like silicon so that it does not cause pain intriceps. A piece of soft fabric can also be placed betweenthe attachment and the suit to reduce the discomfort.

B. Attachment

Besides the choice of the material and design of theattachment, the installment of the suit also largely affectthe behaviors of users. The suit currently has one end ofthe spring attached to arm (above elbow), and the otherend attached to the upper thigh. Users experienced difficultywhen touching the wall to turn and when turning their torsobetween strokes. The installment position can be changed toachieve better performance and allow users to fully extendtheir bodies as usual.

C. Biometric data collection

Heart rate is used to estimate the metabolic cost duringtesting. However the heart rate monitor we used only showedthe peak and average heart rate. The type of monitor thatcontinuously records heart rate over a period of time didnot work under the water as expected. Therefore, a betterwaterproof monitor could provide a better prediction aboutthe metabolic cost. If triaxial accelerometry counts could bemonitored, it could be combined with heart rate to predictoxygen consumption and carbon dioxide production. In thelong term, a system that could directly measure the oxygenconsumption and carbon dioxide production would be moreideal. However, since the user is moving under the water, thesystem will need to be portable , lightweight and waterproof.

D. Other potential applications

Given what we have for now, another direction of theproject is to explore more applications of the augmentedswimming suit. One potential application is to use theaugmented suit for training purposes instead of improvingthe performance and endurance of users. Unlike traditionalswim trainers which the users need to train on land toimprove stroke efficiency and build swim-specific strength,the augmented suit enables users to achieve the same goals inthe water. In this way, the training process will happen real-time while they are swimming. With the same environment,the trainee could feel how the suit makes a difference ontheir turn and strokes. Not only can the trainees increasetheir strength, they can also practice maintaining their strokesand turns while changing how much strength they use.Furthermore, appropriate biometric analysis system could beintegrated onto the suit so that the improvement by usingthe suit could be quantified. This augmented swimmingsuit could revolutionize swim trainings and help swimmersimprove more efficiently.

VII. CONCLUSIONS

In this study, we analyzed the design and performance of asuit that augments freestyle swimmers by re-distributing theload on a wider range of muscle groups. In particular, oursuit uses the recovery (out of the water) phase of arm motionto load a passive element, which is then released during thepull/push (in the water) phase of arm motion.

The material and design of the suit have been optimizedbased on a quantitative analysis of the energies involved infreestyle swimming. The performance of the suit has beencharacterized based on a series of experiments. Our resultsindicate that, while the suit makes the swimmer slower, itdoes reduce fatigue for the arm muscles responsible forpropulsion in water (pull/push phase). This is achieved byshifting some of the load on the muscles used during recov-ery, which as expected are more fatigues as a consequenceof suit use.

In conclusion, this suit has a good potential as a traininginstrument for professional swimmers. Moreover, this studyidentified several areas of improvement which, if addressed,could extend these benefits to recreational swimmers.

REFERENCES

[1] Herr, H., and N. Langman. “Optimization of human-powered elasticmechanisms for endurance amplification.“, Structural optimization, 13.1(1997): 65-67.

[2] R. Mark, “Freestyle Foundations“, USA Swimming,http://www.usaswimming.org/ .