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Looking for a Highly Fatigue Resistance Spring Material

Looking for a Highly Fatigue Resistance Spring Material

axleshox

(Mechanical)

(OP)

28 May 05 08:12

We're currently using a stainless 17-7 Condition C material.
The material needs to go through a 4 slide die for cold forming and cutting.  Thus, we need it in a 2" width by 0.015" thick roll.  

It is subjected to a stainless of about 0.005, 1/2% strain and must be resistant to fatigue for at least a 1 million cycles.  

We've tried 304 and 316 alloys as well as nickel titanium alloys, i.e. Nitinol. The 304 and 316 were far less resistant to fatigue and came out slightly warped because of the heat treating proces.  The Nitinol proved to be too difficult to manufacture and thus too expensive.

I'd appreciate any suggestions or leads.

Elmer Lee

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RE: Looking for a Highly Fatigue Resistance Spring Material

israelkk

(Aerospace)

28 May 05 12:32

I am sorry but I could not understand your post. Are you designing a spring? If so, please explain the spring dimension, deflections, loads etc.

RE: Looking for a Highly Fatigue Resistance Spring Material

axleshox

(Mechanical)

(OP)

28 May 05 13:39

Yes, we are designing a leaf spring, not a coil spring.  There is no load requirement, only a deflection and fatigue requirement.  

The question was not meant to elicit assistance in designing the spring itself. I simply was trying to get suggestions for materials.

The spring's max strain is about 0.005, which for most metals is pretty close to is fatigue limit, I think.  I was hoping someone out there has work on applications requiring super elastic metals.

I hope that helps.

RE: Looking for a Highly Fatigue Resistance Spring Material

israelkk

(Aerospace)

28 May 05 14:47

First of all you can not differentiate deflection from force, a defection is usually a result of force, pressure etc.

However, at this strain the stress in the spring is approximately 103.7 kgf/mm2 or 147.5 ksi. According to AMS B 17-7PH strips at CH900 condition has a minimum tensile stress of 240ksi. Therefore, the stress on the your leaf spring is far beyond the 0.4 to 0.5 of tensile stress or yield stress. This leads to the conclusion that it is beyond the metal fatigue limit even before we take into account surface defects etc.

There are not many materials stronger than 17-7PH but you can try to find Marage 300 or 350, Custom 475 from Carpenter or Elgiloy. However these materials are difficult to attain and they are expensive.

There is other things that you may do with the current 17-7PH but they fall into the design area and manufacture process.But, as you mentioned you do not need assistance in designing the spring itself.

RE: Looking for a Highly Fatigue Resistance Spring Material

axleshox

(Mechanical)

(OP)

28 May 05 16:45

Thanks Israelkk,

   We're using 17-7 condition C that goes thorough a 900F age hardening process.  Would that be any better that 17-7PH.  Appreciate your help and input.

Elmer

RE: Looking for a Highly Fatigue Resistance Spring Material

israelkk

(Aerospace)

28 May 05 16:52

The material comes in the C condtion to allow forming of the spring. After the heat treatment in 900F it becomes condition CH900 and the stength is going up to the 240ksi and as I mentioned in my last post.

You didn't mention how is the spring deflects is it defelects the 0.005 strain only to one direction all the time or both directions?

RE: Looking for a Highly Fatigue Resistance Spring Material

axleshox

(Mechanical)

(OP)

28 May 05 17:05

It's a little envolved, but the gist of it is that the spring is essentially a cantilever beam.  It's formed in the straight position and then the tip is raised and held at an upper position.  During the lifespan, the tip is displaced downward upto 2x the amount it was originally displaced upwards.

The 0.005 strain number is the theoretical amount calculated using a FEM model and some fudging.  It is achieved with the half amplitude oscillation, in other words, just by lifting the tip up by x, the max strain should be 0.005.

So, I believe the answer to your question is that it is subjected to 0.005 strain in both directions.

RE: Looking for a Highly Fatigue Resistance Spring Material

israelkk

(Aerospace)

28 May 05 17:13

If so then according to my calculations (based on minimum tensile strength of 240ksi) your spring should not last more than cycles. You may encounter larger results if the actual strip of 17-7PH will have higher tensile strength. However, one should design for the minimum the spec says because future batches could be in the minimum allowed properties.

RE: Looking for a Highly Fatigue Resistance Spring Material

TVP

(Materials)

30 May 05 18:47

Type 301 stainless steel is often used for small spring applications that require exceptional fatigue resistance.  Type 301 develops its strength from strain hardening (cold working) instead of heat treatment, so warpage would not be a factor.  Somers Thin Strip, a division of Olin Brass, offers Type 301 stainless steel strip in several different tempers, with the highest strength being 280 ksi ultimate tensile strength.  I strongly recommend you contact them to discuss your application.  Use the following link for more information:


http://www.olinbrass.com/somindex.html

axleshox,Type 301 stainless steel is often used for small spring applications that require exceptional fatigue resistance. Type 301 develops its strength from strain hardening (cold working) instead of heat treatment, so warpage would not be a factor. Somers Thin Strip, a division of Olin Brass, offers Type 301 stainless steel strip in several different tempers, with the highest strength being 280 ksi ultimate tensile strength. I strongly recommend you contact them to discuss your application. Use the following link for more information:

RE: Looking for a Highly Fatigue Resistance Spring Material

NickE

(Materials)

31 May 05 12:09

Another stainless material with an endurance limit that is very high and also assured low inclusion and specifically designed for flat flexure is the Swedish Flapper valve Steels. One of these is Sandvik's proprietary grade of 420SS. It is called 7C27Mo2. There is a higher strength version called High-Flex.

Google: Sandvik Materials Technology.

(Also you will find that surface conditon has tons of effect on fatigue performance)

nick

RE: Looking for a Highly Fatigue Resistance Spring Material

mattis

(Automotive)

31 May 05 15:04

continuing on the paranthesis in the previous post. Surface condition is extremly important here do not forget to shot peen the spring to make sure you have negative compressive stresses in the surface.
good luck

RE: Looking for a Highly Fatigue Resistance Spring Material

NickE

(Materials)

31 May 05 15:42

Quote (axleshox):

"by 0.015" thick roll."

Another note from the first job I had in the steel industry.

Toilet Paper comes in rolls. Steel comes in coils.

Another note from the first job I had in the steel industry.Toilet Paper comes in rolls. Steel comes in coils.

RE: Looking for a Highly Fatigue Resistance Spring Material

axleshox

(Mechanical)

(OP)

31 May 05 17:35

I've tried shot peening.  The material is far too thin.  Rather than compressing the surface layer it deformes the actual spring shape.

My mistake NickE.  I'll know what to use when talking to a toilet paper manufacturer now.  You've saved me from the ultimate embarrassment.

RE: Looking for a Highly Fatigue Resistance Spring Material

mattis

(Automotive)

1 Jun 05 05:04

About shot peening, I know realize that you have quite thin material. In my line of work 0,4 mm would be considered as foil... got confused by the imperial measures. Maybe try glass bead blasting which will give you residual stresses but not deform the surface too much. Residual stresses will probably deform the spring anyhow especially if you don&#;t get an even distribution on your part.

//ma

RE: Looking for a Highly Fatigue Resistance Spring Material

israelkk

(Aerospace)

1 Jun 05 05:59

axleshox

It seems we all grinding water. The solution is probably not by changing the material. I think you need to consider design change. If you can give more info on the spring shape and what it is supposed to do it may help. As you mentioned in your posts the deflection is what you are looking for. If so, you may be able to recieve the same delection with less strain using the same strip thickness or even thicker strip but with a different shape of spring.

RE: Looking for a Highly Fatigue Resistance Spring Material

EdStainless

(Materials)

1 Jun 05 09:35
Have you looked at low modulus alloys?  BeCu, BeNi or alpha/beta Ti?  These would involve a lot less force for the same defection.

If you want to stay with the same stiffness tehn look at 21=6=9 (XM-11).  It is available as re-melted coil product from Allegheny-Ludlum.  It is used for aircraft hyrol lines for places where Ti isn't suitable due to temperature or damage tolerance requirements.
In tubing it is cold drawn to about 125ksi yield and 150ksi UTS, though it can be worked to higher values and still have good ductility.
I'll try to get an S-N curve for you.

No load requirement?Have you looked at low modulus alloys? BeCu, BeNi or alpha/beta Ti? These would involve a lot less force for the same defection.If you want to stay with the same stiffness tehn look at 21=6=9 (XM-11). It is available as re-melted coil product from Allegheny-Ludlum. It is used for aircraft hyrol lines for places where Ti isn't suitable due to temperature or damage tolerance requirements.In tubing it is cold drawn to about 125ksi yield and 150ksi UTS, though it can be worked to higher values and still have good ductility.I'll try to get an S-N curve for you.

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RE: Looking for a Highly Fatigue Resistance Spring Material

Compositepro

(Chemical)

2 Jun 05 19:48

Composites can have exceptional fatigue life. Fiberglass or carbon fiber can be combined with thermosets or thermoplastic resins for sping applications.

RE: Looking for a Highly Fatigue Resistance Spring Material

NickE

(Materials)

3 Jun 05 09:17

Also you may want to look around at this website:

http://www.destacomanufacturing.com/technologies.htm

Another thought is that you might be able to utilize two thinner spings in parallel. IE: For flat bending at the same beam geometry and same P-P deflection a strip half the thickness sees far lower stresses. In my work I see this type of application every day. What helps here is that you say you have no load requirement. You may be able to parallel two half thickness strips and get roughly the same stiffness but far lower stresses.Also you may want to look around at this website:

RE: Looking for a Highly Fatigue Resistance Spring Material

Maui

(Materials)

3 Jun 05 10:11 Elastic Design - Automobile Leaf Springs

How do you decide what material to use in designing a specific spring? Consider the leaf spring used for the suspension systems on older cars. These springs are essentially rectangular elastic beams loaded in bending. Suppose that such a beam of length L thickness t and width b can be modeled as simply supported at both ends, and loaded centrally with a force F. If the elastic modulus of the material is E, then the deflection D at the center of the beam is

        D = (FL^3)/(4Ebt^3)  

The maximum surface stress S is given by

        S = (3FL)/(2bt^2)

If the spring is plastically deformed while under load, then it won&#;t be able to &#;spring back&#;. So we set the condition that the maximum stress must always be less than the yield stress Sy.

        Sy > (3FL)/(2bt^2)

Substituting for F from the initial equation we find,

        (Sy/E) > (6Dt)/(L^2)

For a spring in service to undergo a deflection D, the ratio of Sy/E must be high enough to prevent plastic deformation. So the best leaf springs are made from materials that have high values of Sy/E. For this reason spring materials tend to be heavily strengthened by work hardening, precipitation hardening, or solid solution strengthening. Note that small values of thickness t permit larger deflections D for the same value of Sy/E. This is why leaf springs are usually constructed of several beams stacked on top of one another.

I am uncertain of the specific geometry and loading conditions that you are using, but a similar analysis for your specific case should provide you with the combination of physical properties that will allow us to determine the appropriate materials for use in your design. If you do this analysis, get back to us and we may be able to provide you with specific materials that can satisfy your criteria.

Maui

How do you decide what material to use in designing a specific spring? Consider the leaf spring used for the suspension systems on older cars. These springs are essentially rectangular elastic beams loaded in bending. Suppose that such a beam of length L thickness t and width b can be modeled as simply supported at both ends, and loaded centrally with a force F. If the elastic modulus of the material is E, then the deflection D at the center of the beam isD = (FL^3)/(4Ebt^3)The maximum surface stress S is given byS = (3FL)/(2bt^2)If the spring is plastically deformed while under load, then it won&#;t be able to &#;spring back&#;. So we set the condition that the maximum stress must always be less than the yield stress Sy.Sy > (3FL)/(2bt^2)Substituting for F from the initial equation we find,(Sy/E) > (6Dt)/(L^2)For a spring in service to undergo a deflection D, the ratio of Sy/E must be high enough to prevent plastic deformation. So the best leaf springs are made from materials that have high values of Sy/E. For this reason spring materials tend to be heavily strengthened by work hardening, precipitation hardening, or solid solution strengthening. Note that small values of thickness t permit larger deflections D for the same value of Sy/E. This is why leaf springs are usually constructed of several beams stacked on top of one another.I am uncertain of the specific geometry and loading conditions that you are using, but a similar analysis for your specific case should provide you with the combination of physical properties that will allow us to determine the appropriate materials for use in your design. If you do this analysis, get back to us and we may be able to provide you with specific materials that can satisfy your criteria.Maui

RE: Looking for a Highly Fatigue Resistance Spring Material

NickE

(Materials)

3 Jun 05 10:19

Dang Maui you always manage to put the right equations down. Thanks for clarifying what I tried to say (I did badly I should add)

RE: Looking for a Highly Fatigue Resistance Spring Material

axleshox

(Mechanical)

(OP)

3 Jun 05 11:00

   Since so many have ask for specifics of the design, I thought it would be best to spend some time explaining it.

    The sping is a leaf spring that can be modeled as a cantilever beam rigidly supported on both ends.  The beam however is not straight, but instead made up of 3 curves of different radiis.  One end of the beam is held stationary and the other is displaced about 0.75" in total, i.e. .375" upward, and the same amount downward.  As the spring is deformed, the 3 curves essentially change radiis.  There is a formula:

       strain=thick/(1/R1-1/R2)

where R1 is the orginal curvature of the beam and R2 is the resulting curvature after deformation.

   I've written a computer algorithm that uses the above equation, and knowing some geometric constraints, i.e. total spring length, max and min radius, and determines all of the spring geometries that when deflected the desired amount will not give a strain of more than 0.005 which I thought was the upper bound of any metal's fatigue strain. So the resulting spring would only have a max strain of 0. because it would be deflected 1/2 the desired amount upwards and the equal amount downards.

   If anyone wants to know more about this code, my MSN messenging name is

   In the end, the algorithm spit out about 30 different sets of spring shapes.  They were all quite similar and I pick the one that seemed easiest to manufacture, i.e. did not bend over on itself too much.

    What I am finding is that the spring seems to be holding up to simple upward and downward deflection.  However, we realized later that the spring was also being subjected to a torsional load.  As a result, the torsional plus the vertical deflection is starting to produce fatigue failure in the springs.   

    Nicke, the suggestion about parallel spring is an excellent one.  We tried that once and found that if we were to lay up say 3 springs on top of each other, the bottom one would deflect as desired but the top two would start to bend in un-predictable ways.  I attribute the problem to not having the springs tied to one another.  I think essentially the top two springs are buckling.
  
   We're probably going to redesign a few tools that will allow us to bond the springs together with low durometer rubber or urethane.  That way, the different layers can still move in shear with respect to one another, but no buckling can result.

    I started this thread in hopes to find a stronger, more flexible material. That would have been the easiest fix.  

   Redesigning the shape of the spring seems like it would be unfruitful.  The algorith was fairly complete.  The only way to further reduce stress and strain whle still maintaining the same deflection is to use a longer spring.  Unfortunately, the spring is enclosed in a housing and we've already used up every piece of space we could find.

Sorry for such a long post.  I hope someone is willing to read it all.  Appreciate all the comments thus far.  It's geat to know there is a community out there willing to lend a hand.  Thanks all.

Elmer

Hello All,Since so many have ask for specifics of the design, I thought it would be best to spend some time explaining it.The sping is a leaf spring that can be modeled as a cantilever beam rigidly supported on both ends. The beam however is not straight, but instead made up of 3 curves of different radiis. One end of the beam is held stationary and the other is displaced about 0.75" in total, i.e. .375" upward, and the same amount downward. As the spring is deformed, the 3 curves essentially change radiis. There is a formula:strain=thick/(1/R1-1/R2)where R1 is the orginal curvature of the beam and R2 is the resulting curvature after deformation.I've written a computer algorithm that uses the above equation, and knowing some geometric constraints, i.e. total spring length, max and min radius, and determines all of the spring geometries that when deflected the desired amount will not give a strain of more than 0.005 which I thought was the upper bound of any metal's fatigue strain. So the resulting spring would only have a max strain of 0. because it would be deflected 1/2 the desired amount upwards and the equal amount downards.If anyone wants to know more about this code, my MSN messenging name is . I'm almost always online. I'd be happy to discuss this further.In the end, the algorithm spit out about 30 different sets of spring shapes. They were all quite similar and I pick the one that seemed easiest to manufacture, i.e. did not bend over on itself too much.What I am finding is that the spring seems to be holding up to simple upward and downward deflection. However, we realized later that the spring was also being subjected to a torsional load. As a result, the torsional plus the vertical deflection is starting to produce fatigue failure in the springs.Nicke, the suggestion about parallel spring is an excellent one. We tried that once and found that if we were to lay up say 3 springs on top of each other, the bottom one would deflect as desired but the top two would start to bend in un-predictable ways. I attribute the problem to not having the springs tied to one another. I think essentially the top two springs are buckling.We're probably going to redesign a few tools that will allow us to bond the springs together with low durometer rubber or urethane. That way, the different layers can still move in shear with respect to one another, but no buckling can result.I started this thread in hopes to find a stronger, more flexible material. That would have been the easiest fix.Redesigning the shape of the spring seems like it would be unfruitful. The algorith was fairly complete. The only way to further reduce stress and strain whle still maintaining the same deflection is to use a longer spring. Unfortunately, the spring is enclosed in a housing and we've already used up every piece of space we could find.Sorry for such a long post. I hope someone is willing to read it all. Appreciate all the comments thus far. It's geat to know there is a community out there willing to lend a hand. Thanks all.Elmer

RE: Looking for a Highly Fatigue Resistance Spring Material

CoryPad

(Materials)

3 Jun 05 13:34

If the easiest change is to use a stronger material, then re-read TVP's post above about 301 stainless from Somer.

Regards,

Cory

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News

Reformer Spring Resistance: The Basics

Have you ever had a client ask you &#;How much weight is this?&#; Have you ever wondered what springs to use for different exercises on the reformer? Many programs offer a vague recommendation of how many springs to use for each exercise depending on your students, but sometimes they do not provide the underlying reason for the recommendation or the deeper understanding of what the specific resistance provides to a specific exercise.

In traditional strength training, the addition of more resistance (or weight) means a greater challenge for the exerciser. In Pilates, the challenge of resistance is much different; sometimes more resistance doesn&#;t equal more challenge. One of the things that sets the Pilates method of exercise apart from &#;regular&#; or &#;traditional&#; fitness is that Pilates equipment depends on springs to provide resistance, rather than standard weight plates and/or barbells. Another is the way that Pilates employs, or uses, the resistance itself.

The Challenge of Resistance

In order to fully understand how, why and when to use springs in Pilates exercise, we must first gain a rudimentary understanding of the difference in the physics of springs versus weight plates. The nature, or physics, of standard strength training equipment is that the weight, or resistance remains constant throughout the exercise. Any exerciser, no matter their size or body mass, using a leg press machine loaded with 100 lb, will be moving the same amount of weight throughout the motion of the exercise. There will be an initial full effort in order to start the movement (remember that an object in motion already is easier to keep in motion), there will be the force needed to move the foot plate away from the body, and there will be the effort needed to return the foot plate to the starting position without the weight crashing in towards the body. The resistance of 100 lb and the force of gravity remain the constant.

The physics of springs is much different. The type of spring that is used on Pilates equipment is called a &#;tension/extension spring&#;. When this type of spring is stretched from its resting position, it exerts an opposing force proportional to its change in length. In other words, the more you stretch a spring, the more opposing force it provides. This means more force is required to overcome that opposition. In Pilates Reformer Footwork, there is an initial force needed to start the motion; a force needed to stretch the springs, and a force to return the carriage back to the home position. All of these same motions are required for the Leg Press. However, unlike the 100 lb move in the Leg Press, the force that has to be overcome in Footwork increases the farther away from the footbar the carriage is pulled, and decreases as the carriage returns home.

Peak Pilates recommends 3-4 springs be employed for Reformer Footwork. Using the chart below of the varied resistance the Peak Pilates springs provide, we can see that taller people will have greater resistance applied against them at the end range of the exercise (while the carriage is out), and will have to resist against more force initially as they bring the carriage back in. Conversely, shorter people will not extend the springs as far, so they will have less load to apply force to. Let&#;s say one red, two yellow, and one blue spring is used. A person with a 36&#; inseam will have approximately 173 lb of load on them with the carriage all the way out, and a person with a 21&#; inseam will have approximately 118 lb of load.

The length/opposition variable of the springs enables us to teach to every BODY on the same equipment with the same springs, as long as that spring load is applicable to that BODY. Of course, a deconditioned or injured body is going to be treated differently than a healthy body conditioned for Pilates work. An injured or deconditioned exerciser may not be able to safely apply the higher end pounds of force on their joints, so adjustments to the springs will be needed to accommodate those issues. The variability of working with the springs makes working with all abilities possible.

Resistance as Assistance

In Pilates exercise, the way we use resistance is just as important as the amount of resistance we use. Generally speaking, the more resistance there is, the more challenging it would be for the extremities; the less resistance there is, the more challenging for the powerhouse. Sometimes, the less resistance there is in the springs against the carriage, the more difficult the exercise is to perform. This is especially true in an exercise like Long Stretch.

At Peak Pilates, we suggest two springs be used to perform Long Stretch. If a 6&#;1&#; exerciser uses two yellow springs, there will be approximately 88 lb of resistance against the movement of the carriage. That is 88 lb pulling the carriage in, or in this case, slowing down or stabilizing the movement of the carriage away from the footbar. This will help the exerciser to stabilize their own body mass against the movement and will assist them with the return of the carriage from the stretched position. Using two blue springs, this same exerciser would only have approximately 60 lb of assistance with their stabilization. The Long Stretch would be more difficult to stabilize in the extended position and would become even less stable as the resistance decreases with the return of the carriage.

Assistance with greater spring resistance also occurs in the Short Spine Massage. The higher the spring tension, the more assistance is provided with getting the legs and pelvis up and over and allows for a deeper stretch for tighter backs as the hips roll back down to the mat. To challenge the powerhouse in this exercise, two blue springs would supply less assistance to the up and over, making the exerciser provide the effort needed to lift the legs and pelvis. Teaching a student to do the Short Spine Massage for the first time would probably require more spring resistance, while challenging an intermediate student in Short Spine Massage with less resistance would be appropriate. Like the Long Stretch, more resistance equals greater assistance equals less challenging than less resistance with less assistance.

Intention is Everything

Another variable to consider when choosing what springs to use is the intention of the specific exercise being performed. Intention could mean two things: the goal of that particular exercise, or the goal for that particular exerciser. While the goal for every Pilates exercise is to strengthen the connection with the powerhouse, there are secondary goals that need to be taken into account. Having a deep personal connection and knowledge of each exercise is essential to being able to set specific goals for each student.

In the Classical reformer workout, everyone starts with Footwork. The intention for beginners is to build strength and flexibility, so higher spring resistance would facilitate this goal. Intermediate and Advanced students need to build a greater connection with the work, so a variable spring tension for Footwork could help achieve this goal. On the other hand, teaching greater hamstring activation requires a different way of looking at Footwork&#;s intention for a specific client, like a cyclist who wants to attach the legs to the powerhouse for stronger pedaling. Using two blue springs in the Footwork would make the exerciser need to control the outward motion with a strong powerhouse and deeper connection to the pelvis. This would make the exerciser have to actively pull the carriage in with little assistance from the springs. As we can see, one exercise can have three different intentions with different spring requirements.

Another example of how intention can result in different the spring usage is with the simple beginner arm work. If the intention behind doing the exercise is to build arm strength, then one blue spring and one yellow spring would be a good starting point. If the intention is to teach scapular stabilization, two blue springs would challenge that skill with less assistance and therefore greater stabilization required. In the Elephant, the more spring resistance there is, the more hamstring/glute activation is required to pull the carriage away from the footbar; the less spring resistance used, the more the Powerhouse has to Scoop deep to pull the carriage back in. Same exercise, many different intentions.

Not All Springs Are Created Equal

Like the bodies of our clients, every spring is unique. Even springs of the same color may not be identical, and reformers have their own &#;personality&#; with particular springs. For instance, springs inside the Peak Pilates Classical line may behave differently than the metal line&#;s springs. A blue spring on a Classical reformer does not equal a blue spring on the MVe® reformer. The Classical nature of the Resistance Ride spring set offers a different feel from any other springs on the market today. Each reformer in a studio may have the same springs, but have completely different feels because of age of the springs, how the springs were used, and where the springs are placed within the gear itself (which makes a difference in the balance of the carriage). There are reformers with five springs, and there are reformers with four springs. The Classical four-spring set up order on the reformer is &#;Red-Yellow-Blue-Yellow&#;, and the traditional set up for reformers with four springs is &#;Yellow-Blue-Red-Blue-Yellow.&#; However, studios may have a different ratio and order of springs according to the needs of their clients. The total number of springs and their placement within the gear make a difference in the &#;feel&#; as well as the performance of the reformer. The only way to really know the resistance and personality of the springs on a specific reformer is to get on the equipment yourself and test it out.

Finally, you must think about your own connection to the work when considering the use of springs. This connection includes your knowledge of the precision points of each exercise, the skill in applying that knowledge to individual clients, and continuing your own exploration of Pilates exercise within your practice.

 

 

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