PTs have a wide array of techniques in their tool kits to restore athletes to fighting form. Lower-extremity resistance training is a crucial component of those tool kits. Increasingly, machines utilizing the power of this training in rehab are providing real benefit to PTs and their patients. And the biggest benefit may be mental.

"Patients trust their legs more with the tool I use," says Steve Tippett, PT, PhD, SCS, ATC, professor and associate chair of the Department of Physical Therapy and Health Science at Bradley University in Peoria, Ill. "Half the time, my patients are surprised they can do the things I'm asking them to do. They can see that they're getting stronger, and they do get stronger."

In this article, we examine powerful additions to the PT tool kit for lower-extremity resistance training, tools that enable PTs to improve results, enhance performance, and help patients regain their ability and confidence.

THE CRUX OF RESISTANCE TRAINING

As PTs know well, the mechanisms of resistance training apply to all body parts, whether upper body or lower extremities. Resistance training for rehab and performance improvement is particularly helpful for athletes and sports enthusiasts.

Generally, resistance training is valued for the significant customization ability PTs have for their patients. The same exercises can be customized for individual patients for their own tolerance of intensity, repetitions, and more. Programs also can be customized by patient goals, from regaining balance to reassuming world-caliber-level athletic performance. Finally, resistance is tailored to the patient. Each patient, and each muscle and bodily structure, has a certain tolerance toward stress, and the PT can use resistance training to find that sweet spot—the point at which the muscle is stressed correctly in order to get stronger and grow.

Of course, the PT's focus in resistance training becomes finding that sweet spot, the optimal level of appropriate resistance for patients. PTs must find the correct amount that doesn't push patients too hard and doesn't push them too little. The means of doing this is through progression, a methodical process of movement and preparing the patient for growth. The process moves from simple muscle-isolation exercises and contractions to more complicated load-bearing activities. Resistance usually is created with simple gravity, then other manual loads.

But PTs face significant challenges finding the best way to do this. Patients need to function quickly. They need strength without sacrificing other structures besides muscles. They need something that encourages them to continue and improve. For some PTs, the advanced machines and tools available on the market today are just the solution.

ELIMINATING GRAVITY'S PULL

Sometimes any resistance is too much. When a lower-extremity joint is unsteady, and when the simple tug of gravity is beyond a patient's tolerance level, PTs may believe that resistance training is out of the picture.

"You can get your patients on an elliptical or exercise for muscle endurance," Tippett says. "But for many of my patients, the status of the joint precludes the use of those tools. So then you've got to go to plan B. You can put them in a pool if they're comfortable in water and they have continual access to a pool. Or you can use the Shuttle."

The Shuttle System is a product offered by Contemporary Design Co, based in Glacier, Wash. The Shuttle System features a horizontal orientation for patients, negating the pull of gravity during exercise. It's opened up rehab possibilities for many patients with restricted ranges of motion through the lower extremities, and for whom confidence is a debilitating issue.

Tippett uses the two Shuttle models that are highly specific and useful to the athletic population: the 2000-1 and the MVP Pro. The 2000-1 features an elasticord resistance system, which offers a range of 12 to 258 pounds of resistance, promoting concentric and eccentric loading of the muscle through all phases of motion, and strengthening the neuromusculature to cope with acceleration forces. Extruded aluminum alloy rails, adjustable backrests, detachable headrests, and alternate carriage working positions contribute to a smooth and precise flow. The kickplate is adjustable back and forth and vertically to accommodate patients and activities. Additionally, expansion towers and a 25-inch horizontal stand expand the strengthening, stabilization, and flexibility exercises available.

The MVP Pro builds on the 2000-1 system of elasticord resistance, offering head-end elasticord loading, meaning a simpler process of adding or subtracting resistance. A 4° angle of tilt approximates the body lean that occurs during running and jumping movements, and a new feature allows for adjustment of bars to affect the range of motion and initial flexion angle.

"The Shuttle is the best way to transition to weight-bearing loading for lower-extremity strength," Tippett says. "That's one of the real advantages: you zero out the patient's weight on the Shuttle and progress them, working through the right range of motion. The shuttle is a boon to functional training. There are a lot of functional things patients can't do against gravity."

Tippett also values the Shuttle for its universality. Nearly all his patients can benefit, including younger athletes, high-performing athletes, nonathletes after trauma, and older patients with degenerative disease and total joint replacement. "I have a young high school student with recurrent instability and articular cartilage damage who doesn't tolerate open-chain exercises. If she does use those machines, she has restricted range of motion. On the Shuttle, with gradual loading she is able to tolerate exercises through a full range of motion without problems."

The Shuttle had a fascinating genesis. In 1965 the US Air Force considered a Manned Orbiting Lab, and enlisted bioscientists to determine the long exposure of zero gravity to an astronaut's cardiovascular system. The team, including Gary Graham, proposed a system of intermittent positive and negative acceleration forces parallel to the long axis of the body, and studies showed increased endurance, cardiovascular functioning, and tolerance. The project was scrapped, but 20 years later Graham revived the Cardiovascular Conditioner as an exercise device for PTs. Today, the company offers multiple tools geared toward all clinical populations, especially athletes.

"It's a good investment," Tippett says. "There are a lot of ways the clinician can build upon the basics of the Shuttle. You can make the weight-bearing surface unstable and challenge folks that way. You can use different positions of the patient on the device itself, or employ other tech while the patient is there to target diff muscles. It's not just a simple leg press machine. You can control so much more."

HARNESSING BODY WEIGHT FOR RESISTANCE

Above: The Shuttle 2000-1 model promotes concentric and eccentric loading of muscles through all phases of motion.

Much of lower-extremity resistance training is functional, re-creating and strengthening the way the body executes daily physical activities. The progression of resistance training recruits multiple muscle groups at once to rebuild the simplest to the most complex, sports-performance-oriented movements. For athletes in particular, functional exercises in lower-extremity resistance training lays the foundation for sport-specific training, improved performance, agility, and proprioception.

The Total Gym PowerTower, offered by EFI Sports Medicine, San Diego, focuses on function in lower-extremity resistance training through its incline plane design. Not quite horizontal, and not quite vertical, the patient's body rests at an angle. Resistance harnesses gravity and body weight to challenge patients.

Exercises start at the user's ability level, and body weight resistance on the free-rolling glideboard challenges the proprioceptors, stabilizes muscle, and adds multiplane movement and unrestricted range of motion. The advantage of the PowerTower and other Total Gym machines for lower-extremity resistance training is in the ability for PTs to incorporate weight-bearing exercises early in rehab.

EFI contends that the constant load and dynamic pulley system make a difference over spring or tension-type equipment, allowing full muscle strength throughout the exercise and forcing muscles to adapt to the functionality needed in their athletic (or daily) activity. The dynamic pulley system offers unilateral, bilateral, and cyclocentric movement patterns in the lower extremities. And since the patient's body is the load, the body moves within the frontal, sagittal, and transverse planes of motion. So the PT can use the pulley system to create a constant, customized load that accommodates the full range of motion and enhances proprioception.

Another bonus for PTs is easy calibration. The Power Tower is calibrated by the machine, incorporating user body weight, glideboard weight, and any added plate weight, factored with the angle of incline. This offers athletes precise, repeatable levels of resistance and PTs ease in reporting outcomes.

REDUCING LOAD DAMAGE

For athletes and for all patients, building the strength of the larger lower muscles improves the ability to function on a normal basis and on a high-performance basis. But even if patients can tolerate the resistance of gravity or even their own body weight, typical machines can put too much load on the spinal column and other structures around the muscle. Improving this state of affairs is a focus of the Nautilus strength and resistance training system.

Nautilus is offered by Med-Fit Systems, Fallbrook, Calif. The Nautilus leg press comes to PTs as a separate machine or as part of a greater multiuse system, with models including the Studio series, the Nitro series, and the 2ST series. The recumbent orientation on the Nautilus machines work to improve on sled-style and seated lower-extremity resistance training. Older machines limited quad and glut work to the poundage tolerated by the spine. New machines and the Nautilus line fully support the torso and prevent resistance loading on the spine, which can exacerbate shoulder, cervical, thoracic, or lumbar problems and create entirely new problems.

Recumbent machines allow clinicians to fine-tune the angle for the major joints of the knees and hips, and to easily adjust the resistance for a customized session. In addition, the four-bar linkage system with the Nautilus recumbent machines mimics the natural process of supporting extra weight.

"Patients are weakest in the highest degree of knee flexion and strongest in full extension," says Dean Sbragia, president and CEO of Med-Fit. "I like to illustrate by asking a client to achieve and maintain a 90-degree knee angle squatted position. It is very difficult. Yet, when you stand, even though you are using the same musculature, the mechanical advantage requires much less muscle strength or tension to maintain. Same is true with a leg press. The Nautilus leg press' four-bar-linkage system captures the remarkable change in force output though this flexion-to-extension phase. An elliptical cam, used by most competitors' leg presses, cannot achieve this demonstrable force output variation. So you either overload the start point (causing pelvic tilt) or underload 80% of the exercise motion."

ADDITIONAL THERAPIST RESOURCES

Lower-extremity resistance training is designed to get the muscles working and stronger in order to improve daily living and sports performance. It's good to remember that many injuries among athletes occur in the first place because of an imbalance among muscle groups.

SciFit machines are built on the notion of bidirectional resistance. This kind of lower-extremity resistance training exercises reciprocal muscle groups, increasing performance and reducing the risk of additional injury. Bidirectional resistance particularly helps when patients fatigue easily or face rehab walls. This type of movement allows patients to change directions of muscular output, resting one muscle group and working another, without interrupting the session.

The PRO2 model by SciFit, based in Tulsa, Okla, was developed by rehab professionals and promises effectiveness that translates into more patients treated in less time. In addition to bidirectional resistance, the machine comes with seating offering lumbar support and proper alignment, electromagnetic brakes for quiet operation, and step-through seat positioning. Other options for the PT from SciFit include the RST7000 Total Body Recumbent Stepper and the REX Total Body Recumbent Elliptical.

From LifeFitness, based in Schiller Park, Ill, comes products for PTs focused on the benefits of independent loading in lower-extremity resistance training. Users unable to lift the same amount of weight with both limbs, due to injury or trauma, can be at more risk for injury with dependently loaded machines that don't identify muscle imbalances. Independent loading allows this imbalance to be immediately identified and corrected through training.LifeFitness offers a wide array of multiuse machines and systems for rehab and sports training. For lower-extremity resistance training, products include the PRO2 leg press and Iso-Lateral lower-body machines.

NuStep®, based in Ann Arbor, Mich, offers the TRS 4000, which provides both upper and lower body motion, enabling users to work all the major muscle groups when building strength and improving overall cardiovascular fitness. According to NuStep, the TRS 4000 simulates a natural walking motion while eliminating undesirable joint stress and promoting functional fitness.

The power of lower-extremity resistance training may be enhanced with sophisticated machines that guide patients into their rehabilitation. With plenty of bells and whistles combined with a firm foundation of science and function, these newest machines can be used by PTs to help patients regain not only their physical form but their confidence as well.

Amy Lillard is a contributing writer for Physical Therapy Products. For more information, contact .