Vasanth Kumar (Sports Scientist)
It is debated since many years that every sports has its contribution from core musculature stability while only few researches have been published since then. Basketball one of the fastest game and being a group sport also played by the special population in competitive level like able-bodied athletes. The risk of injury especially to the back and in addition the performance enhancement considered as the key in this particular review. While there is very trivial evidence on this subject, some researches has been published since its
Core Stability in Wheelchair Basketball
Basketball is a group sport, played by two teams with five players in each team trying to achieve points by shooting a ball through the basketball ring with limited set of rules (IWBF 2010). Wheelchair sport originated by 1940s, wheelchair based events with the regular wheelchair were created to provide rehabilitation exercises. The modified version of the regular wheelchairs called the sports wheel chairs that have cambered posterior wheels for better stability, and are personalized towards self-momentum and eminent from that of regular wheel chairs (Michael, et al 2010).
The wheelchair Basketball, a modified sport played by disabled athletes. Around 1946 Injured World War II experts developed the sport that instantly swelled across Europe. Informal competitive events arose by 1973 and events that are more official emerged in the following years (Robbins, et al 2010). It is one of the world’s popular Paralympic sports (Shinji, 2005). In accordance with the NCCA regulations, the rules of the wheelchair basketball have only a few modifications compared to basketball (NWBA 2007). Each team aims to prevent the other team scoring and score in opponents’ basket (IWBF 2010). The officials, table officials and a commissioner, Controls the game. Wheelchair basketball is more of hand game. The rules allow throwing, dribbling, or throwing the ball in any direction while railing the wheels (NWBA 2007) which shows that there is more usage of upper extremities. According to Klenck, et al (2007) the lower limb amputees suffer lumbar spinal injuries as they have more of lateral spinal flexion and rotation movements involved in the game. They also emphasised that reduction of injuries is possible when concentrated on balance training, core strengthening, flexibility training, and proprioceptive training for the lower limb amputees. . Ferrara, et al (2000) in a research stated that upper extremities injuries are more common in wheelchair athletes. Stöhr, et al (1997) studied about the injury prevalence in wheelchair basketball athletes with 155 athletes by survey method revealed that the most predominant part of injury are the upper extremities. The survey study reported 60.6% of the athletes’ grieved 272 injuries and over load syndromes. Willardson (2004) in his research elucidated the relation between the mechanism of upper extremity injuries and the de-trained core musculature and the detailed explanation of the same concept given in the later part of this essay. Every sport needs strength, power flexibility, endurance and stability to have good performance on field. However, this essay aims at the core stability for the wheelchair basketball players.
According to NWBA (2010), there are three levels of classification based on the persons’ impairments or on the site of lesion. Those with spinal cord injuries at the level of T7 or above are nested under class I players. While complete motor loss originating at or below T8 and descending down till L2 including bilateral hip disarticulation amputees under Class II and all other lower limp paralysis and paresis arising at or below L2 and all types of lower limb amputees except Bilateral hip disarticulation under Class III. The NWBA (2007) also stated that the total value points on field should not exceed twelve and not more than three Class III players allowed to play together in a team. The actual capability of players in each class differs and according to IWBF (2010), there are five major classifications based on functional activities that an athlete can perform. They are 1-Point player little or no activity on the trunk, 2-point player partially controllable forward movement with absence of trunk lateral movements but with good upper trunk rotation and poor lower trunk rotation. 3-point player good flexion and extension without support and with good trunk rotations absence of controlled lateral movements. 4-point player has normal trunk movements due to unilateral lower limb disability difficulty in ipsilateral lateral movements. 4.5-point player has normal trunk movements with no limitations. There are instances where a player can exhibit characteristic features of one or more class. In such instances there are assignment of half points in between each such as 1.5, 2.5, 3.5 players. Hedges (Member of team Canada, 2009) in the wheelchair Basketball Canada website stated that Athletes sit lower in the wheelchair for two reasons. Firstly, because of the specificity of their disability and classification of the athlete like more limiting disabled players sit lower because of their lesser core muscle function. Secondly, for better ambulatory reasons as they might get good advantage in ability to move and control the wheelchair.
Core Stability Literature Review
Core stability is a term that describes the structures that includes the muscles, which connects the pelvis, spine, ribs and shoulders that provides stability to the trunk (McLean, 2006). Kibler, et al (2006, Page 190) defined core stability as ‘‘the ability to control the position and motion of the trunk over the pelvis to allow optimum production, transfer and control of force and motion to the terminal segment in integrated athletic activities.’’ According to Akuthota, et al (2004) to sustain the functional stability of the spine the muscles around the lumbar spine needs control which he termed as core stability. Lehman, (2006) defined core stability as a muscle or a muscle group that engenders maximum force at a definite velocity.
Critiques on Core stability and core strength started since from early 1980s by many authors. The researchers have concentrated their studies in improving the core stability and strength on the subjects with back pain (Panjabi, et al 1992; Behm, et al 2011; Hodges, 2003). However, there are fewer studies carried out in relation with performance and the core stability in elite sportspersons (Hrysomallis, 2011; Willardson, 2007). Stability needs a wide base of support, which is applicable not only for static actions but also for the dynamic action that has sudden change in vector momentum (Bartlett, 2007, Page 78). The stability is achieved while the maintenance of the centre of gravity over the base of support (Barnes 1980). These evidences when compared to the design of athletic wheelchairs prove positive. The athletic wheelchair has a very wide base of support in contrary from the regular wheelchairs. Another pilot study by Mason, et al (2010) dealt with nine wheelchair athletes from wheelchair basketball, wheelchair tennis, and wheelchair rugby about the wheelchair configuration revealed that the key component for a successful performance on the field is the stability by which the author concluded in the study stating that the modification of wheelchair affects the performance.
According to some authors’ study, good balance has good accuracy (Hartley, et al 1971). This study emphasised on the performance of the jump shot in able-bodied athletes. Consideration of this study because of same kind of sport aspect is possible however, the performance of jump shot not common in wheelchair basketball. With this study as base Hudson (1982) studied in detail about the biomechanical angles that the athletes uses to achieve during the free throw in basketball. The study included the biomechanical analysis of the free throws in able-bodied basketball players. Altogether twenty-five members selected for the study that included highly skilled nine members, seven non-scholarship players of intermediate skill level, and nine low skilled players. The advantage of this study is that the varying skilled players included in the study. Although, the constraint of the study included the exclusion of the disabled athletes and other biomechanical aspects of the core stability and the sports performance as the study compared only the angle of projection, projectile velocity, precision, trunk inclination, altitude of release ratio as the key variables and the centre of gravity given less importance in the study.
Panjabi, et al (1992) studied about the theoretical model of three subsystems that provided spinal stability namely passive, active and neural subsystems. This system of study incorporated all the three systems that are responsible for the core stability. This analysis helps to understand the major components that provide the stability during the static and dynamic postures. Consideration of this study possible since the wheelchair basketball needs more perturbed static and dynamic core stability while in seated position as well as during throwing activities. Although, this study created a base for the core musculature studies in the future the major limitations of this study considered includes the exclusion of the pelvic, shoulder girdle to the subsystems as the core stability also relates with the scapulo-thoracic and lumbo-pelvic stability. In addition, the three subsystems based on the theoretical model makes it less possible to compare to the live model. Various authors like Barnes (1980), Schaafsma (1971) discussed about maintaining the stability with the trunk inclination as a variable for accuracy of shooting the ball into the basket. The study described in detail about the significance of inclination angles of spine related to the core stability and the performance of free throw shooting of the basketball. Limitations in terms of angles and the point of release of the ball in air to reach the basket and no much further support for the core stability found in this study.
To relate core with the upper limb functions Ben Kibler, et al (2006, page 190) stated muscles considered as major stabilizers such as “upper and lower trapezius, hip rotators and glutei for the extremities gets attached to core; also stated that the core acts as the anatomical base for mobility of distal segments. That is ‘proximal stability for distal mobility’ for throwing, kicking, or running activities”. In wheelchair basketball players, the proximal stability of the trunk is more important for the mobility of the upper extremities in terms of throwing or shooting and additionally with ambulation using the upper limbs. Nevertheless, no added details about the biomechanical evidence required for core stability found. As a support to this a study by Cholewicki, et al (1997) hypothesized maintaining spinal stability achieved provided activated muscles found around the spine. The objective of this study corresponds with the muscular co activation of the trunk flexors and extensors that provided the required amount of stability to the spine. The study design incorporated ten individuals performing trunk flexion and extension in a slower pace and the muscles of the right side monitored by surface electromyography. The result concluded that there is co-activation of the trunk musculatures around the neutral spine that progressively increases when more loading delivered to the torso. This research when correlated with the wheelchair athletes reveals that the need for the trunk flexion and extension while ambulating using the wheelchair and during the field performance found necessary. However, this study is limited to the spinal flexor and extensor muscles and did not add details or emphasise on the girdles connected to the core. While Christopher McLean (2006) stated that, the assemblies that deliver stability to the trunk termed core stability. The study included the support of soft tissue structures that associates the shoulder girdle with the trunk and the pelvic girdle that has various accountability related with stability, movement and collective actions. To support his study he has provided a wide range of satisfactory evidence such as the works by Bogduk (1997); Panjabi, (1992a, 1992b); McGill et al., 2003. Bogduk (1997) stated that each segment of the spine possess twelve movements that includes distraction, translation (lateral, medial, postero-anterior and antero-posterior), compression, lateral flexion (left and right), axial rotation (left and right), flexion and extension.
Anatomy of core
According to Bergmark (1989) the muscles design around the spine is the key elements that adds stability to it. He discussed about the local and the global systems of the spine, they are the muscles that originates or inserts or the muscles that has both its origin and insertions at the lumbar vertebrae and the muscles that origins from the pelvis and inserts at the thorax respectively. With his study as base another author Sheri (2005, page 466) stated that “synergist muscle ratios represented by activation of segmental relative to multi-segmental muscles when acting synergistically (i.e., internal oblique/rectus abdominus) would be higher in Chronic low back pain Population group as an attempted to increase stability”.
Bergmark (1989) determined the best way of explanation of the global and local muscle system of the core stability. According to him, the muscles of global system are the global muscles of Erector Spinae, the external obliques, the internal obliques, the Rectus Abdominus muscles and the Quadratus Lumborum (lateral parts) muscles. He also included the muscles of Psoas and Latissimus Dorsi to the global system in his study however, he excluded them because these muscles did not have much influence on the stability. His research also revealed that the local system of the spine also called the lateral stabilisers included muscles of the intertransverse, the Quadratus Lumborum (medial parts), the Transverse Abdominus muscle and the muscle fibers of the local Erector Spinae.
Impact of core stability on performance
For the past decades, the athletic training incorporated the core-training programme as a part of their training programme. Athletes believe that improved core stability will enhance their athletic performance on field (Sharrock, et al 2011). Nevertheless, the researchers (Hibbs, et al, 2008) remain unclear about the relationship between the core stability and the athletic performance. Most of the studies available relate core stability and core conditioning with the low back pain in the non-sporting populations (Behm, et al 2011; Hodges, 2003). However, there are very trivial number of studies that relate core stability with the athletic performance and their enhancements found (Hrysomallis, 2011; Willardson, 2007). Some recent studies piloted relating the relationship among the core stability and athletic performance provided as evidence to support the topic that includes a pilot study by Sharrock, et al (2011) there is a link between the core stability and athletic performance. The study is a correlation between the core stability test and the four performance tests by the thirty-five collegiate athletes as the study models. The core stability and the four-performance test included double leg lowering, T-Test, Forty-yard dash, medicine ball throw and vertical jump tests correspondingly. The results determined using a linear model that revealed there is relationship between both the components especially with the medicine ball throw test that had a stronger negative correlation with the athletes who performed better on core stability test by which the author concluded stating the relation between core stability and the performance. As the pilot study revealed a significant relation between the core stability and the athletic performance, this evidence supports the topic of study by means of comparing the medicine ball throw with the passes in the wheelchair basketball game that needs better core stability for enhanced performance skill.
According to Lee (1999, Page 103), the stability is about the mechanism that supports the transfer of loads and the smooth, natural movements, but not the amount of mobility and the end feel fineness. This is applicable for the sporting populations because of their requirement to improve in the ability of performance while executing a shooting or a free throw movement that requires a good stability and the transfer of load from the core to the upper extremity. To support this Willardson (2004) in a research paper stated that a joint movement that does throwing type of actions owns kinetic energy of the ball that progressively increases and during the point of release gains maximal velocity. He also stated that the transfer of kinetic energy might not be effective in de-trained core muscles, which places a very greater compensatory stress over the muscles, joints and other connective tissues of the arm that performs the action to gain and maintain high velocity while throwing. Under such circumstances, there are more likely chances to acquire an injury. Relating this with the wheelchair basketball athletes where throwing plays a very vital role in the gameplay the need of efficiency in their core musculature can be determined. Another author Hodges, et al (1997) Suggested that while applying core stability on sports performance the acceleration or the deceleration of the body segments may depend upon the extremities’ contraction with core as the basis. Comparing this with the mobility of the wheelchair basketball players, the relation between the core stability and performance is eminent as their primary ambulation is by means of wheelchair propulsion for which they use their upper extremities.
Enhancements in any of the following characteristics such as muscular endurance, muscular strength or muscular power attained if core stability is improved and precisely incorporated into practice of the necessary sports abilities Willardson (2007). His study mainly dealt with the pre-season and in-season core stability exercises and post-season and off-season exercises for core stability and found that there is improvement in the performance level of the athlete. The author is clear in the concept that the core stability has effect on athletic performance and suggests core stability training is important in sports performance. In contrary, a research by Nesser, et al (2009) provided an evidence-based study performed on division I female soccer players to relate the core stability and the performance, which gained no correlation between them. Hence, suggested that there is no relation between the core strength and the performance. However, consideration of this research not possible as the study dealt with able-bodied soccer players and nowhere related with the wheelchair athletes.
Considering these studies as supportive evidence for the topic, the throwing actions is correlated the with the core stability required for the sport, as the wheelchair basketballs’ key scoring is by throwing and shooting the ball.
According to Cael (2010, Page 281) the muscles such as external and internal obliques depend on the deep transversospinalis muscles to achieve the trunk rotation and flexion to sustain the vertebral alignment. He described the transverse abdominus muscle to an “anatomical weight belt” as one of its primary functions is to support and stabilise the lumbar spine. In his text, he also stated that the muscle Quadratus lumborum maintains the alignment of spine in relation to the pelvis while the lower body is fixed. In co-ordination with the Erector Spinae muscle, the spine sustains an upright posture and thereby providing adequate lateral movements and satisfactory spinal extension. While the intertransverse muscles major, purpose is to maintain side-to-side posture against gravity that contracts isometrically and maintains an upright spine in frontal plane. Relating this with the wheelchair basketball where the players’ need more of these types of movements and the athletes can achieve an upright spinal alignment and control over their lateral movements and extension of spine with which can perform better on the field of play.
Core Stability (Training principles and considerations)
The most influential part of any training program is goal setting without which an athlete will lose focus and is ever more challenging to motivate and subject themselves to lowest withholding levels. The goal setting must be dynamic where both the athlete and the coach need to be involved with same aspect of programme. The program should have certain principles and considerations to train the disabled athletes. The training principles remain the same for both the able-bodied and disables athletes. According to DePauw, et al (1995, page 143) there are three main principles followed while training an athlete. The foremost principle for training is frequency, which refers to the regularity or how often an athlete trains. Secondly, the intensity in which they train consecutively applies the duration of the training programme. Sometimes mode of training needs consideration.
According to ACSMs’ guidelines for exercise testing and prescription (Edition 8, Page 242) exercise prescription guidelines for general population is applicable for the special populations. Considerations like pressure sores, cardiovascular status, autonomic dysreflexia, and muscular activity limitations. Acsm also suggests exercise sessions in non-wheelchair seated positions to encompass the muscles that stabilises the trunk.
Core stability training
According to Cook (2003) in his book (Page 29) stated that precursor of strength is stability. Willardson (2007) suggested improved core stability gives very less risk of injury. There are several ways to train the core musculature in order to gain stability. ACSM (ACSM’s certification review, edition 3, Page 165) suggests equipment such as rubber tubing, medicine balls, and bosu balls for core training. Marshall, et al (2005) studied about the exercises on and off the stability ball to find the lumbo pelvic activity during the exercise. His study included eight subjects to perform four exercises on and off the stability ball, which revealed a considerable upsurge in the activity of the rectus abdominus muscle, that lead to the changes to the triggering of the lumbo pelvis musculatures. Cardinale, et al (2011, page 158) enumerated about using various difficulty levels of unstable surfaces with an approach of progressive overload to improve the balance ability of the disabled athlete (amputees) continuingly he also suggested to assess the balance of the athlete on a regular basis. He also stated that the achievement of the motor control by strengthening the trunk musculatures in different positions and techniques in combination with the flexion and extension of the trunk to gain static strength and postural control (2011, page 162). He conjectured that five sets of ten to twelve repetitions each sets show improvement in strength that in turn improves the performance.
According to Allford, A., et al (2010, page 69) a warm-up period with three components need to improve the performance and to avoid injuries. Firstly, an exercise to escalate the respiratory rate and heart rate and the core temperature by almost by 1 degree Celsius, secondly passive or dynamic stretches for the limbs and trunk muscles, and finally the sports-precise skill try-outs. He also stressed in cool down periods following any exercise sessions. Cool down mainly concentrates on reducing the work of the muscle groups and reduces the heart demand. He also emphasised on stretching out the limb and trunk musculatures as a part of cool down sessions. He also suggested massaging for the athletes who suffer early fatigues while exercise sessions. This can assist recovery and eliminate post-exercise metabolic by-products. Geithner (2011, ACSM’s) stated that once mastered a technique or found improvement in stability, balance and strength then application of progressive over load would be beneficial. The preliminary feature of core stability training starts with the activation of the transverse abdominus muscle. This feature achieved by drawing the navel inwards, towards the spine along with the pelvic floor muscle contractions maintaining regular breathing pattern and neutral spine. (Lawrence, 2007, page 23). There are number of exercises that targets core stabilisation given in his book of which only certain exercises considered for the disabled athletes mentioned here. Starting with basic stabilisation exercises that are static in nature like plank (Prone bridging), side plank (lateral bridging) once mastered can progress on to the dynamic exercise programs (Lawrence, 2007, Page 56, 57). Dynamic exercises such as abdominal curls, oblique reach, hip lifts performed in sequential manner. The progressive technique is the slow eccentric curl in which the foot is in the air with the knees flexed, the arms extended spine flexed in supine position followed by slow steady eccentric contraction of the rectus abdominus until the shoulders contacts the floor maintaining the transverse abdominus activation and normal regular breathing throughout the exercise. Repeating this for about five to ten repetitions can increase the strength of the rectus abdominus musculature eccentrically (Lawrence, 2007, page 64).
The introduction of the unstable bases follows mastering the basic dynamic workouts. Firstly, stability ball exercises such as seated pelvic tilting on stability ball followed by stability curls, oblique curls, back extension, lying torso rotation performed on stability ball (Lawrence, 2007, pages 68-74). Performance of exercises using core board and bosu ball serves as an alternative unstable base to achieve core stability. Exercise such as press-ups, press-ups with rotation on core board found to be effective exercise for core stability functions (Lawrence, 2007, page 87, 88). Free weight exercises on the stability ball also involve core stability training. Exercises such as dumbbell chess press, dumbbell flye, press-ups pull-over, seated lateral raise, seated shoulder press, prone frontal extension, prone bent-over laterals, lying triceps extension, cable oblique curl and cable abdominal crunches on stability ball are found effective (Lawrence, 2007, Pages 101-120). According to him, some of the water based exercise such as trunk rotations, twists, alternate bear hugs and pull-throughs using water as resistance concentrates on core musculature (Lawrence, 2007, Pages 185-192). According to Allford, et al (2010, Page 74) advanced athletes can perform exercises using medicine balls. Exercise such as medicine ball abdominal throws and medicine ball rotations three sets of each with eight repetitions with two minutes rest period found effective. He also advised that if the athlete has good trunk control, then the athlete could perform these exercises.
To encapsulate the basketball is a group sport played by five in each team and the modification of this sport is the wheelchair basketball. Both the sports have the similar set of rules followed. This work concentrated on the core stability required for the athlete playing wheelchair basketball revealed that there are limited resources and evidences to support the core stability and the performance of the wheelchair athlete. Few controversy studies found in literature stating there are no relation between the core stability and the athletic performance. However, some studies revealed the effective relation of core stability with the athletic performance. Core stability training involves many different methods such as usage of unstable bases, usage of medicine balls to achieve the results. These techniques when prescribed to the disabled athletes need certain considerations. There are number of study and literature support found concentrated on the relation between core stability and back pain. Researches need to concentrate on the core stability and the performance of the athlete especially the wheelchair athlete or the Paralympic athletes. There are number of study and evidences to support the able-bodied sports. However, very few evidence-based studies carried out based on the disabled athletes. Few evidence based studies obtained from the wheelchair rugby and wheelchair basketball studied. Considerations of further researches in disabled sport in the future to support and improve the quality of rehabilitation and performance of disabled sport are beneficial.
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