Judo is a dynamic, high-intensity intermittent sport that requires complex skills and tactical excellence for success (15). During a single judo match, athletes may be required to perform a great number of highly technical and energy-demanding athletic movements, subjecting the body to high levels of stress over prolonged periods, resulting in physical and mental fatigue (51). A typical high-level judo match lasts between 3 and 4 minutes, with averages of 20- to 30-second periods of activity displaced by an average of 5–10 seconds of interruption (9). Judo medalists of major tournament competitions are typically involved in 5–7 matches in a single day (21). Given the physical and mental rigors associated with the sport of competitive judo, it would appear to be extremely beneficial for a judo athlete to possess optimal neuromuscular control and efficiency of function, as well as decreased injury potential.
Functional training is often defined as training that is aimed at bringing the situational needs and constraints of real-life activities into the training environment to enhance training effectiveness (28). Applying this concept to resistance training for judo requires understanding the physiological demands of the sport and selecting resistance exercises that improve the abilities of the athlete necessary to properly execute sport-specific techniques. Sport-specific exercises, however, do not lend themselves well to the weight room because they are exercises conducted in such a way that the amplitude and direction of a particular movement, as well as the dynamics of the strength release and the contraction of the muscles involved in that movement, correspond to the actual movement of a competitive situation (4). It is recommended that judo sport–specific exercises, such as throwing, pinning, and submission techniques, are restrained to technique drills or actual fighting scenarios on the mat where the desired competitive movement, both in relation to structure and time sequence, can be properly practiced.
The purpose of this article is to provide the reader with an introduction to key functional resistance training concepts and principles that when understood and applied appropriately can aid in developing an effective and well-balanced strength training program for judo athletes. The topics that follow have been specifically chosen for their relevance to the introduction of a functional approach to resistance training for judo.
CONCEPTS ASSOCIATED WITH PROPER PROGRAM PRESCRIPTION
ESSENTIALS OF A SOUND PROGRAM
An Australian strength coach, King, was the first person to make popular a series of elements necessary to increase athletic performance and maintain proper muscular balance. King stresses that any omission in “the essentials” will lead to imbalances contributing to an increased risk for injury. It is recommended that the essentials be covered at least once, if not twice a week in any strength program for optimal results. The essentials include: core strength, power training, knee dominant double- and single-leg exercises, hip dominant bent knee and straight leg exercises, horizontal presses, vertical presses, horizontal pulls, and vertical pulls. Also important to exercise selection is the ratio of exercises. To promote shoulder health, vertical pulls should be trained in similar proportion to horizontal presses. This will ensure balance in the shoulder girdle and reduce the risk of rotator cuff injury. Similarly, balancing hip dominant exercises with knee dominant exercises will promote proper hip balance and may reduce the risk of hamstring injury (14,17,55). Equally important is balancing bent knee hip dominant exercises with straight-leg hip-dominant exercises for proper gluteal and hamstring development. Exercise examples of the essentials are depicted in Table 1.
The execution of judo techniques requires the coordination of multiple joints, and experienced judo players develop specific biomechanical tendencies according to their individual body types. The judo player must adapt to a moving center of mass introduced by the addition of the opponent's resisting body mass and force. As such, specific attention on the mobility and stability of joints are an important component of strength training for judo (27).
The joint-by-joint approach is a concept discussed by Cook and Boyle attempting to explain the demands of different joints and how the functions of these joints relate to training. Although each joint is responsible for demonstrating various degrees of both mobility and stability, for the purpose of this discussion, joint complexes exhibiting greater relative mobility roles under normal function will be termed as mobility joints, and joint complexes exhibiting greater relative stability roles under the same set of conditions will be termed as stability joints. The body can be explained as a stack of joints where each joint complex has a specific function and is prone to predictable levels of dysfunction (6). Beginning with the foot and moving proximally, the joint-by-joint concept identifies joint complexes as alternating between stability and mobility roles.
Trauma and or prolonged inactivity are usually the main culprits for the breakdown of the functional interaction between joints, giving rise to dysfunctional moment patterns that can lead to injury (6,13). Because joints are linked together in a kinetic chain, if a single joint becomes impacted, joints above and below the original affected site must now compensate for either a lack of mobility or a lack of stability in the chain and will begin to experience dysfunction. In fact, it only takes 1 component of the kinetic chain not working properly to negatively impact all other components and ultimately affects movement (11).
When the kinetic chain becomes broken, mobility joints have a tendency to behave like stability joints and experience reduced capacities for motion. Stability joints are just the opposite, in the same set of circumstances; they begin to act more like mobility joints and become hypermobile with decreased neuromuscular control. When this happens, it is essential to treat the injured site and assess each joint in the chain to begin clearing dysfunction (13). Hypermobile stability joints with decreased neuromuscular control should be made to demonstrate greater stability and control, whereas mobility joints that have undergone reduced capacities for motion should be made to move more efficiently and exhibit improved ranges of motion (13). It is important to note that if a training program works to increase mobility somewhere, it must also work to increase stability somewhere else, otherwise the body may theoretically return to a dysfunctional state and all efforts to increase functionality will have been in vain. A list of the joint-by-joint kinetic chain beginning with the foot, including their specific functions and predictable levels of dysfunction, are summarized in Table 2.
ADDRESSING THE JOINT-BY-JOINT APPROACH USING A MOVEMENT PREPARATION
A proper movement preparation or “warm-up” is an essential component in any strength training program, and if designed correctly, may even be the most important aspect of the workout. Before an athlete undergoes performance training, attempts should be made to clear the body of dysfunction, activate stabilizers of the hip and core, and stimulate the central nervous system. This will help ensure that the athlete receives the best training effect from their workout, and if predisposed, may decrease their potential for future injury. There are 4 parts to the movement preparation: foam rolling, static stretching, mobility drills, and a plyometric circuit (Table 3).
Foam rolling is concentrated mostly on the large muscle groups of the hips and legs and is used to decrease muscle density and break up adhesions in the muscle belly (11). This process will help restore the body back to its optimal level of function by resetting the proprioceptive mechanisms of the soft tissue (1). An added bonus to foam rolling is that stabilizers of the hip and core become activated as the athlete attempts to maintain proper body position on the foam roll. Theoretically, static stretching becomes more effective now that muscles are less dense and there are fewer adhesions present. Only when muscle tissue is cold, can muscle fibers undergo some plastic deformation and realize an increase in length (6). When muscle tissue is warm, it is more elastic, and when stretched, although fibers become elongated, they inevitably recoil and return back to their original length (6). Research findings have indicated static stretching to be correlated to injury prevention by helping to increase range of motion and correcting postural distortions (23). Although static stretching has traditionally been a component of exercise preparation protocol, many strength coaches have begun to shy away from static stretching because of the publication of recent studies showing static stretching before exercise can decrease power outputs (43,44,47,54). This hypothesis has generally been accepted as true by the majority of the strength training community. However, new findings suggest that some, if not all, of the decrease in muscular power output potential caused by static stretching may be removed if the duration of static stretching is less than 30 seconds, the muscles are stretched below the point of discomfort, and a dynamic warm-up is conducted immediately afterward before physical activity (10,18).
A series of mobility drills adapted from a mobility routine originally developed by Boyle directly follows static stretching targeting the increased range of motion in joints prone to reduced capacities for motion. The mobility drill series also acts as a dynamic warm-up that may return any muscular force potential lost from static stretching as previously mentioned. The warm-up concludes with a dynamic total body activation circuit that involves a series of plyometric exercises targeting the activation of the central nervous system and training the stretch-shortening cycle of muscle tissue responsible for elastic energy potential. Equally important to including all of the essential components in a movement preparation is not to over burden it with too many exercises. It must be condensed to only what is absolutely necessary to properly prepare the athlete for physical activity. If the warm-up becomes too involved, not only will it take a long time to complete essentially cutting into workout time, but the athlete will begin to lose focus, become sloppy in technique, and not receive the intended training effect. A well-designed warm-up should take no more than 12–15 minutes to complete. See Table 3 for an example of a movement preparation.
Laterality, or the dominance of one side of the body over the other, has been identified as playing a major role in the technical and tactical approach of judo players, including the development of gripping patterns and angles of attack. Upper- and lower-body symmetry, as well as integrated trunk strength as an intermediary between these muscle groups, can be impacted by the design and implementation of a well-designed strength program (48).
Understanding body structure and how muscles normally interact during functional movement is imperative to creating effective strength training programs. One particular point of interest is how the body is linked anteriorly and posteriorly in a diagonal pattern. It is now understood that anatomic structures normally described as hip, pelvis, and leg muscles are contralaterally linked with so-called arm and spinal muscles via the thoracolumbar fascia, allowing for an effective load transfer among spine, pelvis, legs, and arms (25,52). The lumbar-pelvic-hip complex has been called the “hub” for both weight-bearing and functional kinetic chain movement. The role of the myofascial and skeletal tissues in this region is to absorb forces, to initiate and control movement, and to transfer forces to the surrounding tissues from either ground reaction forces transmitted superiorly at heel strike or upper-extremity trunk forces transmitted inferiorly. Muscles, such as the middle trapezius and latissimus dorsi, act over the shoulder girdle to influence lumbopelvic hip mechanics (25). The same can also be said of leg and hip muscles, such as the biceps femoris and gluteus maximus because they influence shoulder girdle mechanics (25). The value to understanding this system of cross-linkage is to use this knowledge to prescribe exercises that train hip stabilization and engage back and hip muscles in their proper motor patterns. For this reason, all standing upper-body pulls and posterior chain exercises should be conducted on one leg with the load in the opposite hand (Figure 6). This will train proper load transfer between the lower and upper extremities through a stable hip and back.
To properly train the core, it is important to understand its composition and its primary function. Core musculature predominantly includes muscles of the lumbar spine, abdominal wall, back extensors, and quadratus lumborum (37). However, as was discussed earlier about the upper body being contralaterally linked to the lower body through the lumbo-pelvic-hip complex, it is now known that the core extends well beyond the lower back and abdomen to include muscles of the pelvis, legs, and arms, such as biceps femoris, gluteus maximus, middle trapezius, and latissimus dorsi. Core musculature is very different than muscles of the periphery or limbs in the sense that its primary function is to prevent motion rather than initiating it (37).
When the body is involved in athletic movements, such as running, throwing, or changing direction, the entire musculature of the core undergoes various degrees of isometric contraction, creating a stiffening effect that restricts superfluous movements of the trunk (36). Power generated from the hips can now be absorbed and transmitted to the upper body through a stiffened core (52). Muscles of the core act more like springs that function as elastic storage and recovery devices rather than independent muscles that flex the spine, and they should be trained this way. Exercises that stress stabilization and load transfer, such as planks and rotational lifts, should be the focus of a core training program rather than exercises that require repeated spine flexion, such as sit-ups and crunches.
Studies have shown that exercises targeting core muscles as flexors rather than stabilizers not only decrease core stability, but the repeated flexion and extension of the spine can also cause the degeneration of intervertebral discs (8,29,50). In addition, a common misconception is that closed kinetic chain exercises involving large muscle groups of the lower body, such as the squat and deadlift, encompass all necessary stimulus required for adequate core training. Although performing these exercises does require the activation of core muscles, EMG studies have shown that they do not significantly activate the quadratus lumborum or abdominal obliques (38). An effective core program is at the heart of a good strength program. Prescribing exercises that require the core to function properly is the key to core training and will increase effectiveness as a strength coach or trainer.
LOWER EXTREMITY TRAINING
SINGLE-LEG EXERCISES VERSUS DOUBLE-LEG EXERCISES
A recent change in the competition rules of the International Judo Federation has lead to resurgence in the use and effectiveness of leg-dominant throws as opposed to hand-dominant throws. Some of the most common techniques at the 2010 World Championships were those throws that require execution with balance and explosion off of a single leg that is planted on the mat surface, including uchimata and osotogari (34). This observation suggests the importance of lower-body training, with particular focus on single-leg exercise when training judo athletes.
Almost every athletic movement in judo requires acceleration, deceleration, or balance and stabilization of a single leg. Even if both feet are on the ground, the load and demand experienced by each leg differs and the feet are rarely parallel to one another. Extreme right or left stances (wide foot placement in the sagittal plane with either the right foot or left foot forward) are commonplace in judo, and one leg is often being used to attack or defend, whereas the other is tasked with maintaining balance. Emphasis on training the lower body in a stable environment, such as with the traditional double leg squat, will target prime movers of the hip and knee (gluteus maximus, hamstrings, and quadriceps) without adequately training muscles responsible for stabilizing the hip and knee that can lead to muscular imbalances, increasing the potential for injury (35). Single-leg exercises are 3 dimensional, whereas double-leg exercises tend to be only 2 dimensional. The lateral subsystem (gluteus medius, adductors, and quadratus lumborum) becomes engaged and trained during the single-leg squat (Figure 4) acting in their normal roles as stabilizers. These muscles become relatively less active when conducting lower-body stable bilateral exercises, such as a traditional double-leg squat (6). Another advantage of incorporating single-leg exercises into program prescription is that relative to double-leg exercises, greater demands are placed on muscles of the lower extremity without placing heavy loads on the spine, so that the athlete's legs experience greater training effects at a reduced potential for back injury (6).
Although a sound program will emphasize single-leg exercises over double-leg exercises, it is still important to periodically train under conditions stable enough, allowing for maximum activation of prime movers. With highly unstable exercises, the ability to maintain proper technique with added resistance reduces the ability of the primary muscle groups to produce tension during the exercise, thus limiting the potential for conditioning the lower body for high-intensity activities that occur in sport and daily living. A recent study (3) comparing muscle force and activation of the quadriceps muscles in stable and unstable environments found that the ability to exert force under stable conditions significantly exceeded force output under unstable conditions and that a very unstable environment would not provide sufficient overload resistance to promote quadriceps strength adaptations. It is accepted that overload tension on the muscle is essential for fostering strength training adaptations (2).
A possible solution to being able to train safely at high intensities and still receive some of the benefits of single-leg training is to take a double-leg squat and modify it, so that a greater demand is placed upon a single leg with a reduced base of support, increasing the activity of the lateral subsystem as in the rear foot–elevated split squat (RFESS) (Figure 3). A recent study (35) recorded the EMG activity of selected hip and knee muscle groups when conducting a RFESS and that of a traditional double leg squat. It was found that the RFESS produced greater activity in hamstring and gluteus medius muscles relative to the double-leg squat because of a reduced mediolateral base of support that may have demanded higher neuromuscular activity to support the body in the frontal plane. Although quadriceps activity was greater in the double-leg squat relative to the RFESS, quadriceps activity during the RFESS remained relatively high, demonstrating a sustained ability to generate force in the quadriceps. Although it may seem that the reduction of quadriceps activity during a RFESS relative to a double-leg squat is a negative aspect, a more even quadriceps to hamstring activation ratio reduces shear forces at the knee, suggesting it to be a safer exercise (35,46).
Squats should go to parallel to maximize training effect, unless a partial range of motion squat is part of the program prescription as with a body weight single leg ½ squat used when the athlete's stabilizers and neutralizers of the hip, knee, and torso are not yet strong enough for the femur to go parallel under sufficient control. Research conducted on squat depth through a full range of motion comparing knee joint angle and quadriceps activity has shown that peak activity levels occur between 80° and 102° of knee flexion (20,53). Partial squats were found to elicit only 59% maximum volitional contraction (MVC) of the quadriceps and 63% MVC of the hamstrings in another electromyogram study (33). There have been numerous studies (16,19,32) cautioning against the regular practice of loaded deep squats (also known as full squats) where the femur goes below parallel. Patellofemoral compressive forces, tibiofemoral compressive forces, and tibiofemoral shear forces all progressively increase as the knees flex and reach peak values near maximum knee flexion (16,26,40,49). Performing the parallel squat is recommended over the deep squat for athletes with healthy knees because injury potential to the menisci and cruciate and collateral ligaments may increase with the deep squat (16,45).
FRONT SQUATS VERSUS BACK SQUATS
A functionally based strength training program will typically emphasize the use of front squats over back squats. Although an athlete may be able to lift more weight when conducting a back squat (22), a front squat is better for building functional strength because the load is more naturally distributed throughout the body (12) and exerts less compressive forces on the knees and spine, making it a better exercise choice. A recent study (22) comparing back and front squat biomechanics found that front squats produce significantly lower maximal joint compressive forces at the knee and reduced lumbar stress without compromising muscle activity in the quadriceps and hamstrings relative to back squats. Front squats require the lifter to maintain a rigid upright body position emphasizing leg drive rather than back extension in the concentric phase of the lift. Becoming strong in the front squat position translates well into developing important skills related to aspects of weightlifting, such as in the catch phase of the clean and the racked position of the push press and jerk. The front squat also helps develop shoulder flexibility, which is an important carryover to pressing exercises. If the athlete does not currently possess the required range of motion of the wrist to properly rack the bar when performing the front squat, wrist straps can be used to reduce tension and alleviate any wrist discomfort.
It is well documented that the body adapts quickly to stresses placed upon it (5), and for this reason, training stimuli or stress should be periodically changed to avoid stagnation. It is this phenomenon that has given rise to periodization in strength training programs. Periodization is a term used to describe variation in training specificity, intensity, and volume organized in planned periods or cycles within an overall program, usually over the course of a year. One study determined that periodized strength training will lead to adequate increases in muscular strength of first-class judo athletes, allowing the ability to perform movements and techniques faster and more efficiently during a match (7).
Two periodization models commonly discussed in today's strength training programs are stepwise (or linear) periodization and undulating (or nonlinear) periodization. In a stepwise periodization model, volume, measured in total repetitions, incrementally decreases as training intensity, measured in total weight lifted, reciprocally increases for the major lifts over the course of a training cycle. Each training phase is generally 4 weeks long, consisting of 3 heavy weeks followed by a light or “unloaded” week, to allow for recovery and decrease the potential of overtraining. In an undulating periodization model, volume and intensity for the major lifts demonstrate greater variation over the course of a training cycle. Phases alternate between accumulation phases stressing volume and intensification phases that stress load intensity.
Studies comparing performance variables from athletes who have undergone both periodization models tend to favor undulating periodization as the superior method (39,42). Periodically alternating volume and intensity may supply the neuromuscular system with the stimulus needed for adaptation to occur and, at the same time, allows for the body to recover and regenerate (41). With stepwise periodization, the continuous increases in intensity over the course of a training cycle subjects the body to ever-increasing levels of stress, requiring a light or unloading week for regeneration (41).
The amount of time spent in each training phase to maximize training effect without leading to stagnation seems to vary considerably throughout the strength and conditioning community. One study indicated that strength training programs tend to lose their efficiency after only 2 weeks (31). Another study indicated strength gains can continue up to 6 weeks within a single phase (30). Regularly training elite judo athletes using the undulating periodization method has afforded the author with the observation that 3-week training phases allow for optimum adaptations to occur without the onset of stagnation or the risk of overtraining. An example of a 4-phase, 12-week, nonlinear periodization model for judo before a major competition is shown in Table 4.
As was stated earlier when discussing periodization, the body adapts quickly to stresses placed upon it and therefore must be constantly challenged to avoid stagnation. When developing a strength training program, there are typically 2 ways to achieve this goal. One is to increase the amount of weight being lifted for a particular exercise, whereas the other is to modify an exercise so that it becomes less stable (balance training). Usually, the later tends to work best in exercise prescriptions contained within accumulation phases because higher degrees of instability are associated with lower degrees of force production. Although strength gains are usually associated with exercises that cause significant muscle overload tension as previously mentioned, improvements in strength have also been documented in judo athletes participating in balance training attributed to enhanced intramuscular and intermuscular coordination (24). In any case, it is important that any progression in exercise prescription, whether it is an increase in weight or a decrease in stability, challenges the athlete but does not significantly exceed their abilities. Progressions should be logical and be in accordance with training objectives specific to each phase as defined by the periodization model. An example of each progression method is depicted in Table 5.
Possessing tactical excellence and having the ability to execute an array of complex skills necessary for success in judo competition requires the ability to move well and efficiently; this means that the athlete must excel in basic movement patterns and be absent of postural distortions, faulty movement patterns, and muscular imbalances. Although the sport of judo has its own special considerations, it is important that a program not become so overly sport specific in exercise prescription that it becomes deficient of the fundamental resistance training concepts and principles discussed in this article. Incorporating a functional approach in a judo strength and conditioning program, one that incorporates resistance training techniques that properly train the athlete's specific situational needs and body function, will further enhance sporting performance capabilities and reduce their potential for noncontact and repetitive overuse injuries.
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