After purchasing this deal, you will need to visit the website listed on your Groupon voucher to complete redemption.

The Deal

• $29 for Entry into an Eight-Week Flex Tennis League in the Chicago Suburbs ($40 value)

After enrolling, players are matched with competitors of similar skill levels at courts nearby where they work or live. Members will accumulate points based on performance and will be eligible for a playoff tournament with prizes. Click here for more information on the match-making process.

Tennis Strings: Choosing the Right Tension

Finding the right tennis racket is critical, but stringing it at a suitable tension can be equally important. Figure out your sweet spot with Groupon’s study of racket strings.

When it comes to their rackets, professional tennis players seem to be downright neurotic. Some may stash as many as 10 versions of the same racket in their bag to use over the course of just one match. But whereas hockey players are simply being superstitious when they burn their sticks between each period, tennis players have a reason to be profligate: as the match progresses, a racket’s strings lose their tension, so players must switch in order to keep the tension with which they’re comfortable. Indeed, string tension is as important as any other element on the court, a direct reflection of a player’s style—a tightly strung racket provides more control and more spin, for instance, while looser strings produce extra power.

The physics behind string tension is a matter of basic kinetics. When a ball collides with the bed of strings, both surfaces compress to absorb the impact. The tennis ball flattens, and the strings depress like a trampoline. As both sides bounce back to normal, the ball launches in the opposite direction of the impact. By design, the strings handle most of the force of this rebound, returning around 90 percent of the energy they take in. Since looser strings depress more, they take in (and thus release) more energy, resulting in a more powerful ricochet. With tighter strings, however, the ball flattens more during impact, which allows the strings to get a better grip on the sphere—a boon to players who prefer to add spin to their shots.

Along with the benefits of each style, there are drawbacks. Higher tension also means a tougher impact, which can send nasty vibrations up a player’s arm in a distracting C-sharp tone. Likewise, though the prolonged contact between the ball and looser strings can mean more power, it can also compromise control, as the racket head may twist unintentionally upon impact, changing the flight of the ball. For the pros, it’s all a matter of personal preference and comfort, but choosing the right string tension can help amateur players improve their game, too. Those with already fast strokes might benefit from the added control of taut strings, whereas those who need a little help to generate power might want a bit of extra slack.