From antigravity treadmills to aerial yoga, fitness has left the ground in recent years in a departure from traditional activities that could damage joints and muscles. Although we love those aerial thrills, fitness experts are beginning to think on their feet as joint-friendly fitness evolves.

Fitness experts are continuing to develop equipment and activities to promote joint health and limit resistance to the user's own body weight in the interest of increasing range of motion to work hard-to-engage muscles.

SmartFlex is one such tool, a four-foot-long resistance bar with spring-loaded activation ends with the objective of restoring alignment, correcting imbalances and improving posture.

"It's a tool to help people dial into their physique, even if they aren't highly trained athletes, it can help them understand which muscles are overactive or underactive," SmartFlex Founder and CEO Philippe Til told Relaxnews. "It helps establish a baseline of what your body is capable of doing and improving on it by means of movement compensations."

SmartFlex lays claims to pain alleviation and injury prevention and both easy stretching and exercises that have more of a cardio effect are possible for the bar, which costs $158.

A client says in the SmartFlex promotional video that the product has improved his golf swing because he now has a greater range of motion in his shoulders.

It also provides strength training, and a wide variety of moves are possible as with cable resistance training.

Even slacklining is jumping on board, creating a balancing act between traditional exercises done on the rope and developing others that require one foot on the ground.

Slacklining involves a low-hanging tightrope that improves balance while minimizing joint damage, and an increasing number of moves are being discovered by fitness experts.

It started with the Gibbon Fitness Line, which comes with a poster featuring 18 exercise moves, many of which start from the ground up, giving fitness the edge over fun for the first time in slacklining. The kit is available for $79.99.

Gibbon has already come out with a book and corresponding DVD about how to get fit on a slackline.

While slacklining will always provide fun, its recent focus on fitness could thrust it into the ranks of cable resistance training methods, which have caught on due to their capacity to provide customized, efficient workouts to develop strength, balance and core stability.

Developed by Navy SEALs, cable suspension training has become popular and has become nearly synonymous with TRX. Suspension training draws interest from fitness enthusiasts because it leverages the user's own body weight and claims to provide customized, efficient workouts to develop strength, balance and core stability.

Home TRX kits can be purchased for $199.95.

TRX now has some playful competitionin the form of Monkii Bars.

While TRX involves an adjustable nylon cable that offers thousands of permutations in which to work just about every muscle in the body, Monkii Bars are wooden handles that are suspended by Spectra cords.

Spectra is also used in rock climbing, and although a video used in the Monkii Bars Kickstarter campaign shows an adrenaline junkie working his triceps suspended from a high-flying hot air balloon, more moves are possible with easy access to the ground.

Enthusiasm for the sleek design has been strong and the Monkii Bars Kickstarter campaign raised over $110,000 in 39 days on Kickstarter, swinging past its original 25,000 goal.

Monkii Bars' rotating dowels are likely to accommodate the hands better than the feet and therefore limitations to the variety of leg workouts relative to the offerings of TRX should be expected.

The two bars are each just over seven inches in length and together weigh one pound, making them highly portable. Because the bars are hollow, the Spectra cables can fit inside for neat storage and transport.

Monkii Bars are still available for pre-order for a reduced price of $98. Shipping is expected next month.