Why do some polys play differently from each other as they lose playability?


Hello all!

Why do some polys seem to gain power as they lose playability as time go by, while other polys go "dead" and lose power? Yet both lose control and spin.

And sometimes I've noticed that the same string has lost playability in both ways? Is it the way a person strings it each time?


I attribute change in poly playing characteristics to three things : 1) Tension loss ; 2) Loss of shape/texture/coatings ; 3) Notching, or "locking in" of the stringbed, reducing string movement.

For polys that gain power as they lose playability, it's likely that #1 is the dominant culprit, while #3 is unlikely. For polys that go "dead", #2 and/or #3 are the likely reasons why. Tension loss is still there, but it's not as big of a factor.


Yea, this is a interesting topic. 3-4 hours of good performance from a poly
Was/is catching up with me, means going thru 2-3 rackets a week.

But back to the topic, i use STB and used to string at 50lbs, after about
2 hrs, the strings would get a bit soft/more power..
So basically they would lose tension, and enough to start adding some power to the stringbed...which i didnt like. So change racket, or use for training in which case after about 4-5 hrs, they would just go dead.

Eventually i upped the tension to 52lbs...this really helped in that the strings would
Soften up, lose tension over 3-4 hours..but then the tension loss was tolerable...
So then , 4hrs of decent performance, and then would just die...


Hall of Fame
yes...also many other factor, heat, cold....because they are copolys ...just like us they are all somewhat different....oh I remember babolat did a study a while back and found that most copolys and lose up to 50% tension in less that 20 hours!


Older, 'traditional' single-filament strings are effectively a plastic, like the string in a weed whacker. Plastics have poor yield strength. Read about that here -


If you do read that, your question should be 'why would they use something with that characteristic for tennis strings?'. The answer is that the yield curve is effectively the COR, or rebound curve as well, which is what allows you to take big swings without hitting the ball into the fence constantly.

The down sides to this type of material are that their initial stiffness can lead to repetitive use injury, and when the material is stressed beyond the yield point, it does indeed loose power, control, and "bags out".

To combat this, manufacturers have begun to add significant amounts of material that effects the string's elasticity and yield strength. These strings, such as HyperG and Head Lynx, behave physically more like rubber than plastic. They do stretch and fatigue as well, but their increases yield limit means that unless they actually break, they will tend to increase in perceived power as they age.