TENNIS.com gear editor Justin diFeliciantonio and his technical advisers answer your equipment questions each day. Click here to send in a question of your own.
You’ve talked at length about how natural gut is the healthiest string to use for your arm. What about the worst string for your arm?—John T.
Natural gut is indeed the best string for injury prevention. As I’ve written numerous times in the past, its elasticity and low stiffness are unmatched by man-made synthetics. For this reason, gut should always be the string of choice for folks prone to arm injury.
As for the other end of spectrum: The worst possible string in terms of arm safety is undoubtedly Kevlar. Kevlar’s high tensile strength makes it ideal for manufacturing things like automobile tires and SWAT vests. It also makes for an incredibly durable string, even more so than the toughest polyesters. For years, string makers have touted Kevlar as the last resort for chronic string breakers.
But Kevlar’s durability comes at a cost: Its intense stiffness makes it unbelievably harsh on the arm. How harsh? According to the United States Racquet Stringers Association’s 2012 String Selector, the most pliant Kevlar far more rigid than even the stiffest polyester…and as those of us who’ve played ball with poly know, it’s no joke.
In particular, the most shock-inducing string, per the USRSA’s data, is sold as one half of Prince’s Problend with Duraflex 16, a hybrid offering. Breathe deeply: Problend’s Kevlar measures a whopping 981 lbs./in. To put that into perspective: Consider that the stiffest gut, nylon, and polyester in the String Selector measures 124, 231, 304 lbs./in., respectively.
Very rarely, if at all, should players string with Kevlar. I wouldn’t recommend it; it’s just not worth the risk to the tendons in your elbow and shoulder. If you do break strings quickly, try working with a qualified racquet technician. They should be able to help you find a suitable monofilament to plug the holes in your game.