Individual goals must be set for each athlete dependent upon his or her current functional level, the level of competition to which they are to return, and the specific sport of the athlete. In general, the goals of the training program are to restore and/or improve flexibility, endurance, strength, balance, and agility. Once the athlete has completed his or her acute phase rehabilitation, the concept of a needs analysis may assist in establishing more sports-specific goals. The needs analysis takes into account the fitness needs of both the activity/sport and the individual athlete, thus designing a more customized versus a “cook book” program. To develop a needs analysis, both a physiologic and biomechanical analysis must be completed. When considering a specific event, one must look at the muscles involved, the energy system needs, speed/strength/power/endurance requirements, and any other specific needs of the event itself.6 Next, the current status and prior history of the athlete is determined and a program is then designed to progress him or her toward those specific goals. Sport-specific training is fundamental in returning the athlete back to his or her respective sport. The rehabilitation program should incorporate a whole body approach including core strengthening and exercises for the noninjured extremity.

Controversy exists in the literature regarding static stretching.7 Several studies have shown that there is little evidence to support its role in injury prevention and determined that preexercise static stretching may actually negatively affect performance.⁸ Some researchers found decreases in muscle strength⁹ and decreases in jumping ability¹⁰ after passive stretching. The concept of using a dynamic warm-up instead of static stretching has gained popularity in both the literature and on the field. Some of the proposed benefits of a dynamic warm-up versus static stretching are that the muscles are in more continuous movement, thus increasing the overall temperature and achieving a more “true warm-up.” Dynamic stretching can also use more sports-specific movements to incorporate balance and motor control and mental preparation for the athlete, which may help to prime the neuromuscular system for the upcoming event.¹¹ A few examples of dynamic warm-up exercises are heel/toe walking, marching, skipping, long leg kicks, gluteal kicks, lunge walking, carioca, and lateral slides. This does not mean that static stretching should be abandoned, however. Shrier⁸ contends that regular stretching as part of a comprehensive program and not before exercise can increase force, jump height, and speed.⁸ Athletes who need greater range of motion or need to increase overall flexibility may still benefit from static stretching (Box 33-1). Stretching after activity may also tend to relax the tissues and prevent general postactivity stiffness.

Special considerations must be given to injured athletes with regard to strengthening. Rehabilitation of knee injuries in particular has presented the clinician with a challenge. For example, the main goal of rehabilitation following ACL reconstruction is to restore lower extremity strength while protecting the reconstructed graft and the patellofemoral joint from excessive stresses. Selective quadriceps muscle atrophy occurs following injury and/or immobilization. Strength deficits in the quadriceps of up to 10% have been reported by Shelbourne and associates12 at an average follow-up of 4 years following ACL surgery. Debate exists between the uses of open kinetic chain (OKC) versus closed kinetic chain (CKC) exercises to build quadriceps strength (Fig. 33-1). Several authors have advocated the use of both after ACL reconstruction.^13,14 A literature review by Ross and associates¹⁵ on OKC versus CKC exercises following ACL reconstruction indicates that the greatest amount of ACL strain and patellofemoral joint stress occurs at approximately 40° of knee flexion to full extension.^16,17 It was therefore recommended that OKC exercises for quadriceps strengthening be performed with knee angles greater that 40° to avoid excessive stress on these structures. Closed chain activities beyond 60° were to be avoided since maximum stress on the patellofemoral joint occurs between 60° and 90° of flexion.¹⁷

Because of the predominant atrophy of type I (slow twitch) muscle fibers following injury or immobilization, high repetitions (6 to 10 sets, 12 to 15 repetitions) with low resistance is recommended early in the rehabilitation program.¹⁵ Establishing normal muscle balance for both involved and uninvolved limbs is one of the primary goals. A comprehensive strength training program should address core, hip, calf, and ankle musculature, as well as establish appropriate quadriceps/hamstring ratios. Strengthening of the hamstrings using both closed and open chain methods is important because of their role in assisting in the control of anterior tibial translation. Traditional and functional techniques can be incorporated for both variety and effectiveness (Box 33-2).

There has been an increasing amount of literature in recent years regarding the relationship of hip and core strength as factors in lower extremity injuries. Unfortunately, this relationship is not quite clear. For example, weakness of the hip abductors and external rotators has been shown to contribute to increased hip adduction and internal rotation motion observed in female runners with patellofemoral pain or iliotibial band syndrome. However, it has also been shown that these motion abnormalities can exist even though no strength deficits are present. This indicates an apparent disconnect between muscle strength and observed abnormal kinematics in some cases. Therefore, it has been suggested that additional factors such as altered proprioception and neuromuscular control of the lumbo-pelvic and hip regions should also be considered in the clinical assessment and treatment plan of individuals with lower extremity injuries.¹⁸

Agility is the ability to rapidly change body direction, accelerate, or decelerate. It is influenced by balance, strength, coordination, and skill level. Agility can be improved by first developing an adequate base of strength and conditioning that is appropriate for the difficulty level of the athlete. After this is achieved, drills designed to enhance reactive and explosive motor skills can be progressively incorporated (Fig. 33-4).

Guidelines for speed and agility training are as follows:

Box 33-6 lists various speed and agility drills. This list provides examples only; the reader may wish to refer to specific resources on speed, agility, and plyometric training for a more comprehensive list and description of drills.^20,22,25,26

Neuromuscular control is the ability to produce controlled movement through coordinated muscle activity.27 It is the efferent motor response to sensory input from the somatosensory (proprioceptive and kinesthetic) system, the visual system, and the vestibular system. Stability is achieved by continuous feedback to the central nervous system from the integration of input from these three systems. The somatosensory system uses several different types of sensory input from proprioceptors and the sensory nerve terminals found in muscles, tendons, and joint capsules. Proprioceptors relay information relating to movement and position sense.

Visual input received in the cortex and vestibular nuclei provides information for the vestibular and somatosensory systems to make adjustments to maintain stability and balance. Dynamic joint stability is the ability of the joint to remain stable under the rapidly changing loads during activity.²⁷

Following an injury, deafferentation to ligament and capsular mechanoreceptors may occur. The presence of tissue swelling and pain can also compound sensory damage by disrupting sensory feedback that can alter reflexive joint stabilization and neuromuscular coordination.

Neuromuscular training programs aimed at enhancing or restoring neuromuscular control following injury have been developed and have been shown to reduce the incidence of injury.^28–32 A comprehensive neuromuscular program would integrate exercises that challenge all three regulatory systems: the somatosensory, visual, and vestibular systems. The neuromuscular program should incorporate a multilevel approach, which includes combinations of strength training, flexibility, balance, agility, and plyometric exercises. Activities that induce adaptations to the system may include open and/or closed chain exercise, eccentric training, balance activities, reflex facilitation, stretch-shortening, biofeedback training, and controlled position training. Balance training might include stationary and dynamic surfaces, such as wobble boards, balance beams, and foam pads, to enhance both static and dynamic balance. Functional training, such as jumping and landing, agility, and perturbation training, should also be included depending on sport demands. Fig. 33-5 illustrates several examples of neuromuscular training exercises.

As mentioned previously, the clinician must continually monitor the athlete for tissue tolerance and to determine readiness to proceed to the next phase in the rehabilitation process. Myer and associates have proposed a progressive end-stage return to sport protocol following ACL reconstruction that is based on the athlete meeting specific criteria before being able to progress to the next phase.³³ The protocol consists of four stages: dynamic stabilization, functional strengthening, power development, and sports performance symmetry. One significant limitation of this protocol is that some of the criteria were based on the use of specialized testing equipment such as a stabilometer and isokinetic equipment, which most clinicians would not have available.

Single-leg hop tests are commonly used to determine an athlete’s progress in his/her rehabilitation program and to determine the readiness to return to sport. Various single-leg hop tests either used alone or in combination have been described in the literature.34–38 These tests include single-leg hop and stop tests,³⁶ single-leg hop for distance and time, triple hop, and the triple crossover hop.^34–39 Several studies have shown these tests to be reliable with intraclass coefficients between 0.66 to 0.97.^40–42 Barber and associates recommended using at least two hop tests and achieving a limb symmetry score of 85%.³⁴

Other test measures have been used to determine return to sport as well. Vertical jump height (Fig. 33-6) and isokinetic testing have been used to assess function and strength.^43,44 A 1 repetition maximum (RM) leg press test or squat can also be used to assess strength. The shuttle run and figure eight run have been used to test the ability to run, cut, and pivot.^34,45,46 The T-test (Fig. 33-7) and the Edgren side step test are two tests that can be used to assess agility and body control.⁴⁷ These tests can also be used in the rehabilitation program as functional drills.

Speed tests measure the body’s displacement per unit of time. Testing speed for clinical purposes is usually limited because of lack of appropriate space. The majority of the research on these tests has been with ACL deficient or ACL reconstruction individuals; however, the tests may be used in other lower extremity patient populations as well. Standard health and fitness tests for flexibility, local endurance, aerobic power, and agility/speed such as those described in The Essentials of Strength and Conditioning⁴⁷ may also be incorporated into the testing protocol and compared with available normative data.

Davies⁴⁸ has developed a functional testing algorithm that uses a systematic functional progression of testing and exercise. It is designed to progressively increase stresses on the athlete while gradually lessening clinical control. The algorithm includes the following: subjective information, basic measurements, KT 1000 test, balance testing, closed and open chain strength testing, two-leg jump test, unilateral hop test, lower extremity functional test, and sports-specific testing.⁴⁸ Very specific criterion must be met before the athlete is allowed to progress to the next level. Frequent testing and monitoring of the patient allows the clinician to always know the status of that patient. A specific rehabilitation program can then be designed to address individual deficits instead of following a preset clinical protocol.

Recent research by Hewett and associates⁴⁹ has focused on biomechanical loading measurements in female athletes in an attempt to predict those who are at risk for ACL injury. They concluded that increased valgus motion and valgus moments at the knee were key predictors for potential ACL injury (Fig. 33-8). If predictive factors associated with lower extremity injuries can be identified, specific screening programs and training programs could potentially be designed to reduce the risk for injury.

In general, there is currently no standard accepted series of tests to determine when an athlete is ready to return safely to sport. The decision should be based on ROM, strength, symptomatology, and functional testing. Box 33-7 provides a list of tests that the clinician may select to assist in the decision. It is recommended that a minimum of two hop tests,³⁴ a strength assessment, and an agility/body control test be used. The athlete must demonstrate proper form and technique throughout the test procedures. A deficit of 10% or less with good control is currently used in many facilities to allow return to sport. There are obvious limitations to the tests; however, they appear to be the most commonly used in various combinations. Further research is needed not only to determine risk factors, but also to determine what testing procedures would be best to predict safe return to sport.