Strength Imbalance Research Articles

INFLUENCE OF ASYMMETRICAL LOADING ON SKELETAL AND SOFT TISSUE STRUCTURES

Asymmetrical loading produces a temporary functional scoliosis, but the long term effect of such weight bearing is unclear. It is also unknown whether chronic, static submaximal loading is sufficient to incite adaptive bone mineral density (BMD) or lean tissue responses. This is of concern due to the adaptive nature of bone, muscle, and connective tissue. Also of interest is the potential development of muscular strength imbalances due to external stress. PURPOSE To determine to what extent (if any), muscular and/or skeletal adaptations occur due to asymmetrical static loading. METHODS Eight healthy male commercial cameramen (44±7 yrs) underwent infrared thermographic imaging of the upper body, isometric scapular elevation strength testing, scapular and shoulder manual muscle testing, and dual energy X-ray absorptiometry (DEXA) bone mineral and lean tissue measurements. Researchers conducted two-way repeated measures ANOVA testing to determine within subject differences between loaded (right) and unloaded (left) sides of the body for upper body mean surface temperature, trunk/arm bone mineral and lean tissue content, scapular regional BMD, femoral neck BMD, and scapular elevation isometric force generation. RESULTS Participants' left sided trunk/arm lean tissue masses were significantly greater than right. (19,304±3245 vs. 18,519±3068 g, p < 0.05) No significant differences existed bilaterally for any other dependent variable. CONCLUSION Repetitive asymmetrical static loading with a hand held commercial camera was insufficient to induce adaptive bone or lean tissue changes within the loaded side of the body. However, participants did demonstrate increased lean tissue mass in the left trunk/arm region. Further research is recommended to determine whether repetitive, asymmetrical loading induces adaptive changes within the unloaded side of the body during camera carriage. Supported in part by Gatorade Sports Science Institute U.S. Student Grant Program.

Kinetics of the upper extremity in the open and square stance tennis forehand

Seven right-handed teaching professionals and eight intermediate tennis players were filmed using two high-speed cameras (100 Hz) as they performed open and square stance forehand drives. Three-dimensional coordinates (3D) were reconstructed using the DLT method. A three-segment rigid body model of the racket and upper extremity was used to calculate the kinetics of the wrist, elbow, and shoulder joints up to impact. The open stance created lower resultant velocities of the racket at impact (21.2 and 15.8 m/s) than the square stance (22.3 and 16.4 m/s) for professional and intermediate subjects, respectively. The largest components of the resultant joint torques were generated by the shoulder horizontal adductors, followed by elbow varus torques, and shoulder internal rotation torques. Torques were similar across stance and skill level except for significantly (p < 0.05) greater peak shoulder internal rotation torques in the square compared to the open stance, greater peak wrist flexion torques in the intermediate compared to the professionals, and greater peak wrist flexion torques in the square stance compared to the open stance. The data did not support the hypothesis that the open stance technique creates greater loading throughout the upper extremity than the square stance technique. Peak upper extremity torques were similar to peak torques reported for baseball pitching and represent loads that could contribute to strength imbalances and overuse injuries.

Isokinetic assessment of knee flexors and extensors in professional soccer players

Isokinetic assessment of knee flexors and extensors in professional soccer players J.L. Croisiera, V. Reveillona, J.M. Ferretb, T. Cotteb, M. Gentyc, N. Popovichd, Mohty Filhoe, J.E. Faryniuke, S. Ganteaumea and J.M. Crielaarda Department of Physical Medicine and Rehabilitation, CHU Sart Tilman, Liege, Belgium Center of Sports Medicine, Lyon-Gerland, France Center La Roseraie, St Adresse, France Standard de Liege football Club, Liege, Belgium Tuiuti of Parana University, Curitiba, Brazil Muscle injuries are among the most common insults in soccer players and result from multifactorial origins. In recent studies [1,2], we focused on hamstring muscle strains because of the high frequency of re-injury and persistent complaints after return to athletic activities. This study attempted to define the thigh muscle profile in professional soccers and to identify preseason isokinetic strength variables as predictors of hamstring muscle strain. Seventy-seven professional soccer players (age: 26 ± 4 years, weight: 76 ± 5 kg, height: 180 ± 5 cm) recruited from 4 elite teams (in Belgium, Brazil and France) were included in the study. All the participating Centers used a Cybex Norm dynamometer and a standardized preseason isokinetic protocol consisting in concentric exertions (angular speeds of 60 deg/sec and 240 deg/sec) of both knee flexor and quadriceps muscles; afterward, flexors were subjected to eccentric angular speeds of 30 deg/sec and 120 deg/sec. The nature of muscle abnormalities was determined using statistically selected cutoffs: bilateral differences of 15% or more, concentric ratio less than 0.47, and mixed ratio (eccentric flexors / concentric quadriceps) less than 0.80. Thereafter, players were observed for 9 months and we recorded the severity and frequency of new hamstring muscle injuries throughout the subsequent competitive season. Focusing on the quadriceps in the concentric mode at 60 deg/sec, the whole group of players averaged 3.03 (± 0.42) N.m/kg, with a 7% difference between extreme team values. Flexors in eccentric at 30 deg/sec reached on average 2.32 (± 0.64) N.m/kg, with a 34% difference between extreme team results. Referring to the selected limits, 55% of the whole group of players were isokinetically imbalanced and result analysis confirmed the discriminating character of the eccentric trial and the specificity of the original mixed ratio [2]. During the longitudinal follow-up, seven players sustained clinically diagnosed hamstring muscle injuries that caused them to miss playing time (more than 4 weeks). Among them, six presented isokinetic preseason abnormalities. These results allow us to fix the risk factor of hamstring injury at: – 15% in the presence of strength imbalance (6 injuries in 41 imbalanced players), – only 3% in the absence of strength abnormality (1 injury in 36 normal players). Soccer players were isokinetically characterized by a great interindividual variability of flexor and extensor muscle performances. Assuming the multifactorial origin of muscular injuries, we emphasize the importance of strength imbalances as a major risk factor. Soccers with imbalances appeared 5 times more likely to sustain a hamstring strain than those without the imbalance. Consequently, preseason isokinetic assessment may allow a preventive approach of that problem. ISSN 0959-3020/03/$8.00  2003 – IOS Press. All rights reserved 62 J.L. Croisier et al. / Abstract

Muscle Strength Imbalance in the Hip Joint Caused by Fast Movements

Eleven male sportsmen at the age of 24.3 ± 4.5 were examined. Their hip joint flexors and extensors were tested by an “REV-9000” Technogym dynamometer system during isokinetic movements at angular velocities of 100 (low) and 200 (high) °/s. The range of hip joint movements was from 30 (in flexion) to 130° (in extension). Torque values and their ratios for hip flexors and extensors at different angular positions were obtained and compared. It is shown that, at high speeds, the flexion movement significantly raises (p < 0.001) the torque ratios of flexors and extensors in flexion positions of the hip (50 and 60°). These ratios approximately twofold exceed their values at moderate velocities. The weakness of hip joint extensors in extreme flexion positions of the hip may cause injury of this group of muscles at fast movements.

Evidence for strength imbalances as a significant contributor to abnormal synergies in hemiparetic subjects.

Abnormal synergies in the paretic shoulder and elbow of hemiparetic subjects were quantified during maximal voluntary contractions (MVCs) in 27 subjects with a history of stroke and 8 age-matched control subjects. A six-axis load cell allowed simultaneous measurement of the primary torque the subject was attempting to maximize and the secondary torques at other joint actions. For example, during MVC of shoulder flexion, shoulder flexion is the primary torque and the secondary torques are internal/external rotation, abduction/adduction, and elbow flexion/extension. In general, the stroke subjects had increased secondary torques compared to controls, resulting in abnormal joint torque coupling within the set consisting of elbow flexion, internal rotation, adduction, shoulder flexion. Unlike previous studies, abnormal secondary torques in several cases were due to strength imbalances, which occur when the strength deficit for a particular joint action is greater than the strength deficit in the opposite joint action. This hypothesis was supported by electromyographic recordings and by the finding that subjects with larger strength imbalances tended to produce larger secondary torques. Possible mechanisms and consequences for rehabilitative treatments are discussed.

Management of hip dislocation with postural management.

Hip dislocation in children with cerebral palsy has a well-documented history and morbidity. This paper presents a retrospective study of children with bilateral cerebral palsy who had various postural management and its effect on hip deformity. The most widely accepted theoretical model of hip subluxation/dislocation is that an imbalance in muscle length and strength around the hip leads to acetabular dysplasia and consequent hip subluxation. Maintenance of muscle length and strength and loadbearing is therefore a logical prevention. Research on normal infants' postures has provided biomechanical data to form the theoretical basis of 24 h postural management equipment. The notes and X-rays of 59 children with bilateral cerebral palsy from East and West Sussex and Oxfordshire were examined and measured to determine whether a relationship existed between postural management and the level of hip subluxation/dislocation. X-rays were measured using Reimers' hip migration percentage. Postural management support was divided into three groups for analysis. Category 1: use of a 24-h postural management approach using Chailey Adjustable Postural Support (CAPS) systems in lying, sitting and standing; category 2: two items of CAPS (either lying/sitting or sitting/standing supports); category 3: use of the CAPS seat only and/or any other postural supports. Hip status was recorded for analysis as both hips safe (under 33% migrated), or one/both hips subluxed. Children using 'All CAPS' before hip subluxation maintained significantly more hip integrity than other groups (chi2 P < 0.05). Postural management interventions have an important role in the prevention of hip dysplasia.

Relationship between hip muscle imbalance and occurrence of low back pain in collegiate athletes: a prospective study.

To assess whether athletes with strength imbalance of the hip musculature would be more likely to require treatment for low back pain (LBP) over the ensuing year. The study population included 163 National Collegiate Athletic Association Division I college athletes (100 males and 63 females) undergoing preparticipation sports physicals. Institutional review board approval was obtained to acquire and analyze hip muscle strength data. A commercially available dynamometer (Chatillon, Lexington, KY) incorporated into a specially designed anchoring station was used for testing the hip extensors and abductors. The maximum force generated for the hip abductors and extensors was used to calculate a percentage difference between the right and left hip extensors and abductors. Treatment of athletes by the athletic trainers for LBP unrelated to blunt trauma over the ensuing year was recorded. Of all athletes, 5 of 63 females and 8 of 100 males required treatment for LBP. Logistic regression analysis indicated that for female athletes, the percentage difference between the right and left hip extensors was predictive of whether treatment for LBP was required over the ensuing year (P = 0.05). There was no significant association noted for the percentage difference between the right and left hip abductors in females and for the percentage difference between both the right and left hip abductors and right and left hip extensors in males requiring treatment for LBP. These data support our results from our previous cohort study, adding validity to the concept of hip muscle imbalance being associated with LBP occurrence in female athletes. This research further supports the need for the assessment and treatment of hip muscle imbalance in individuals with LBP.

MUSCLE STRENGTH AND FLEXIBILITY IN YOUNG ELITE SWIMMERS

Research indicates that collegiate and Olympic swimmers display increased shoulder joint external rotation (ER) and decreased shoulder joint internal rotation (IR) ranges of motion (ROM). Swimmers show normal values for ER muscle strength but are proportionately overdeveloped regarding their IR muscle strength. These imbalances may predispose an athlete to shoulder injuries. Our goal was to determine if the physical characteristics of high school swimmers is consistent with the current body of knowledge regarding shoulder strength and ROM of elite level swimmers. Twenty-four subjects (age 14.5 ± 1.8) were recruited from a local swim club and reported to Blythedale Children's Hospital's Sports Medicine Center. Twenty-four subjects were evaluated for: body composition using bioelectrical impedance, shoulder IR and ER ROM using a hand-held goniometer, nd one-minute push-up repetition maximum (RM). Bilateral shoulder IR and ER torque (ft-lb) in the abducted position was assessed in eight subjects using an isokinetic dynamometer. Evaluations were made at speeds of 180 and 300 deg/sec. The results were as follows: percent body fat, 17.1 ± 5.6; push-up RM, 33.3 ± 12.1; IR ROM, 66.0 ± 13.3; ER ROM,89.6 ± 9.0; 180 deg/sec IR peak torque, 50.0 ± 19.2; 180 deg/sec ER peak torque, 21.2 ± 8.8; 300 deg/sec IR peak torque, 57.5 ± 27.2; 300 deg/sec ER peak torque, 31.9 ± 9.4; 180 deg/sec ER:IR peak torque ratio, 0.42:1; 300 deg/sec ER:IR peak torque ratio, 0.55:1. Normal ROM for IR is 70 and ER is 90. IR limitations may indicate a tight posterior capsule. A normal ER:IR torque ratio is 0.67. Abnormal ER:IR torque ratios indicate muscle strength imbalances. Our findings are consistent with the current literature and warrant investigation whether a strength and flexibility program can prevent these imbalances.

Bilateral Strength Comparisons among Injured and Noninjured Competitive Flatwater Kayakers

Context:Anecdotal evidence suggests a relationship between strength imbalances and injury incidence.Objective:To examine the relationship between bilateral strength imbalance and incidence of injury.Participants and Design:Thirty national- or international-standard flatwater kayakers were classified as noninjured, trunk injured, or upper-limb injured based on the number of days lost from training over the last 6 months. Bilateral strength imbalance was measured using a kayak ergometer, producing data for peak force and force impulse for each side of each stroke. Bilateral strength imbalance was then compared between the noninjured, trunk-injured, and upper-limb-injured groups by means of 2 one-way ANOVAs. No participants reported training days lost through lower-limb injury.Results:A significantly elevated bilateral peak-force strength imbalance was observed between the upper-limb-injured and the noninjured groups.Conclusion:These data support the existence of a relationship between strength imbalance and incidence of injury.

Comparison of upper limb musculoskeletal function and throwing performance in adolescent baseball players and matched controls

Objectives: To compare upper limb musculoskeletal profile and throwing speed in adolescent baseball players and matched controls. Participants: Fourteen elite early adolescent (13–16 years) baseball players and 14 age, height and weight matched control subjects. Main outcome measures: Joint range of motion, isometric muscle strength and overhead throwing speed. Results: No significant differences in shoulder or elbow joint range of motion were found, though there was a significant increase in pronation (P=0·03) in the baseball group compared to the control group. No significant differences in shoulder and elbow isometric muscle strength were found between the groups. However, the baseball players threw the ball approximately 50% faster than control subjects. Conclusions: Fast throwing speeds may be achieved in well-trained early adolescent baseball players without changes in isometric muscle strength and with changes in only some ranges of motion. Greater emphasis on the achievement of fast throwing speed by the use of sound overhead throwing technique, particularly in the early stages of a baseball career, may minimize the development of upper limb joint range and muscle strength imbalances which possibly predispose baseball players to injury.

Factors associated with thoracic spinal cord injury, lesion level and rotator cuff disorders.

The study was concerned with the secondary functional compromise persons with long-term paraplegia contend with, that has been shown to be associated with wheelchair use. Of particular interest was the relationship between the level of thoracic spinal cord injury (SCI) and factors predisposing to rotator cuff disorders (RCD), one of the most common upper extremity musculoskeletal complications linked with long-term SCI. Disorders of these peri-articular structures have previously been associated with impaired trunk postural control and abnormal muscle strength ratios in both able-bodied groups and in paraplegic athletes. Despite their neurologically intact shoulder joint musculature, high-level and low-level paraplegics have different degrees of trunk and pelvic stability available to them during activities of daily living (ADL). This fundamental functional anatomical difference between high-level and low-level paraplegics had not previously been related to the diagnosis of RCD in a non-athletic long-term paraplegic population. A descriptive cross sectional study was undertaken to demonstrate the differences in the prevalence of clinically diagnosed RCD in a high-level (n=22) and a low-level (n=20) group of persons with long-term paraplegia. Any perceived differences were then related to the functional anatomical variations between the two groups. Inferences were made based on factors predisposing to RCD known to exist among both able-bodied and paraplegic athletes. The 42 subjects completed the Wheelchair User's Shoulder Pain Index (WUSPI) to establish the presence or absence of shoulder pain and the Musculoskeletal Function Assessment (MFA) instrument to determine differences in functional ability and perceived degree of difficulty within five categories of ADL. Each participant underwent a clinical examination using validated provocative clinical tests and isometric muscle strength ratio testing. There was a higher prevalence of RCD in the high-level group (P=0.009) which correlated with decreased trunk control (P=0.009). Differences in ability to perform functional tasks were not shown to be greater in the high-level group, although there was a higher degree of perceived difficulty in ADL. Muscle strength imbalances between the shoulder adductors and abductors were shown to be greater in the high-level group. The results of this study suggest that the functional anatomical differences that exist within paraplegia contribute to the propensity of high-level paraplegic persons to suffer from RCD. These findings send a clear message to service-providers that greater acknowledgement of the differences in trunk postural control specific to the level of thoracic SCI is required. This may have implications for the prescription of wheelchairs, assistive devices and instruction for alternative ADL techniques to this specific population.

Asymmetrical strength changes and injuries in athletes training on a small radius curve indoor track.

1) To evaluate strength changes in the hindfoot invertor and evertor muscle groups of athletes training and competing primarily in the counterclockwise direction on an indoor, unbanked track, and 2) to observe injuries occurring in these same runners over the course of an indoor season. Prospective observational study. Fowler-Kennedy Sport Medicine Clinic, The University of Western Ontario, London, Ontario. A convenience sample of 25 intercollegiate, long sprinters (200-600 m) and middle distance runners (800-3,000 m) competing and training with the 1995-1996 University of Western Ontario Track and Field team. A standardized protocol using the Cybex 6000 isokinetic dynamometer was used to measure peak torques of the hindfoot invertor and evertor muscle groups of both limbs using concentric and eccentric contractions performed at angular velocities of 60, 120, and 300 degrees/sec. Changes in peak torques between the preseason and postseason values were calculated and compared using a repeated measures analysis of variance test. Injury reports were collected by student athletic trainers and in the Sport Medicine and Physiotherapy clinic. Primary analysis indicated that the left (inside limb) invertors increased in strength significantly more than the right (outside limb) invertors (p = 0.01), while the right evertors increased in strength significantly more than the left evertors (p = 0.04). A high incidence of lower extremity injury (68%) occurred in this sample of runners, corresponding to an injury rate of 0.75 injuries per 100 person-hours of sport exposure. Although sample size was limited, secondary analysis indicated that strength changes were not significantly different for injured (n = 17) and uninjured (n = 8) runners (p > 0.05). The observed small, but statistically significant, asymmetrical changes in strength of the hindfoot invertor and evertor muscle groups can best be described as a training effect. Altered biomechanics proposed to occur in the stance foot while running on the curve of the track are discussed in relation to the observed strength imbalance. A causal link between strength changes and lower extremity injuries cannot be inferred from this study, but suggestions for further research are made.

Trunk muscle activation in open stance and square stance tennis forehands.

Electromyography of the trunk muscles were compared between the open and square stance forehand drives of 14 collegiate tennis players. Surface EMG were bilaterally collected from the rectus abdominis (RA), external oblique (EO), and erector spinae (ES) in open and square stance forehand drives. EMG data were transferred by telemetry, 12 bit A/D converted at 1000 Hz, and stored for analysis. Rectified and smoothed EMG data were normalized (NEMG) to maximal isometric voluntary contractions and mean NEMG were calculated during the forward swing and follow through phases of the stroke. A 2 x 2 x 2 x 6 factorial ANOVA (Gender, Stance, Phase, Muscle) with repeated measures on Subject showed significant (p < 0.05) effects of Gender, Muscle, Phase, and several interactions. The nonsignificant differences in muscle activation between stances did not support the belief of tennis experts that open stance forehands require greater trunk activation than square stance forehands. Mean NEMG of the ES were significantly (p < 0.05) larger than EO or RA, which was consistent with observations of tennis-specific strength imbalances and increasing incidence of low back injuries in tennis.

Major ion toxicity in effluents: A review with permitting recommendations

AbstractEffluent toxicity testing methods have been well defined, but for the most part, these methods do not attempt to segregate the effects of active ionic concentrations and ion imbalances upon test and species performances. The role of various total dissolved solids in effluents on regulatory compliance has emerged during the last few years and has caused confusion in technical assessment and in permitting and compliance issues. This paper assesses the issue of ionic strength and ion imbalance, provides a brief summary of applicable data, presents several case studies demonstrating successful tools to address toxicity resulting from salinity and ion imbalance, and provides recommendations for regulatory and compliance options to manage discharges with salinity/ion imbalance issues. Effluent toxicity resulting from inorganic ion imbalance and the ion concentration of the effluent is pervasive in permitted discharge from many industrial process and municipal discharges where process streams are concentrated, adjusted, or modified. This paper discusses procedures that use weight‐of‐evidence approaches to identify ion imbalance toxicity, including direct measurement, predictive toxicity models for freshwater, exchange resins, mock effluents, and ion imbalance toxicity with tolerant/susceptible text species. Cost‐effective waste treatment control options for a facility whose effluent is toxic because of total dissolved solids (TDS) or because of specific ion(s) are scarce at best. Depending on the discharge situation, TDS toxicity may not be viewed with the same level of concern as other, more traditional, toxicants. These discharge situations often do not require the conservative safety factors required by other toxicants. Selection of the alternative regulatory solutions discussed in this paper may be beneficial, especially because they do not require potentially expensive or high‐energy–using treatment options that may be ineffective control options. The information presented is intended to provide a better understanding of the role of ion imbalance in aquatic toxicity testing and to provide various recommendations that should be considered in addressing these issues.

Kinanthropometric and physiological characteristics of outrigger canoe paddlers

We describe the physiological characteristics of amateur outrigger canoe paddlers. Twenty-one paddlers (13 males, 8 females) were evaluated for body stature, aerobic power, muscular strength and endurance, peak paddle force, flexibility and 250 m sprint paddle performance at the end of the outrigging season. The mean variables ( - s) for the males were: age 27 - 9 years, height 175 - 5 cm, body mass 80 - 5 kg, arm span 178 - 7 cm, sitting height 100 - 2 cm, aerobic power 3.0 - 0.4 l·min-1, maximum bench press strength 85 - 19 kg, right peak paddle force 382 - 66 N and left peak paddle force 369 - 69 N. For the females, these were: age 26 - 6 years, height 168 - 5 cm, body mass 70 - 8 kg, arm span 170 - 5 cm, sitting height 97 - 3 cm, aerobic power 2.3 - 0.5 l· min-1, maximum bench press strength 47 - 10 kg, right peak paddle force 252 - 63 N and left peak paddle force 257 - 60 N. Analysis of variance revealed diff erences (P ≪ 0.05) between the dominant and non-dominant sides of the body for peak paddle force, isokinetic internal and external rotation, and flexion and extension torque of the shoulder joint. The outrigger canoe paddlers were generally within the range of scores found to describe participants of other water craft sports. Outrigger canoeists should be concerned with the muscular strength imbalances associated with paddling technique.

A COMPREHENSIVE ANALYSIS OF THE SWIMMER'S SHOULDER

595 Shoulder impingement syndrome is the most common injury suffered by the competitive swimmer. The aetiology of this condition was studied in 95 age group and 12 masters swimmers. Based on shoulder injury status, the age group swimmers were divided into 20 acutely injured (mean = 16.5 years), 35 with a history of injury (mean = 16.7 years) and 40 non-injured (mean = 16.0 years). The masters swimmers (mean = 44.1 years) were all chronically injured. Assessments were made for differences in training volume and duration, swimming technique, rotator cuff flexibility, posterior joint capsule inflexibility, glenohumeral joint laxity, and concentric rotator cuff strength and endurance. The injured athletes demonstrated a trend towards reduction in active internal rotation (left p = .124, right p = .019). The injured swimmers had significantly reduced flexibility in the posterior joint capsule (left p < .001, right p = .042). An assessment of the glenohumeral ligaments detected that injured athletes had significantly more laxity on the anterior drawer (left p = .003, right p = .012) and inferior sulcus (left p = .007, right p < .001). There were no differences in posterior drawer of generalized joint laxity. Concentric strength testing found no significant difference between the subject groups on internal or external rotation strength. All studied groups had strength imbalances between the internal and external rotators. Endurance testing found a trend towards reduced external rotation (left p = .193, right p = .003). It is hypothesized that the combination of glenohumeral joint laxity combined with rotator cuff imbalance and low endurance plays a major role in the aetiology of shoulder impingement. Inflexibility of the posterior capsule also contributes to the development of rotator cuff injury.

KNEE FLEXOR IMBALANCES IN ELITE SNOWBOARD RACERS

341 Snowboard racing requires that the snowboard rider position themselves with either their right or left leg forward on the snowboard. We hypothesized that this asymmetric position on the snowboard may place differing demands on the skeletal musculature during snowboarding resulting in muscle strength imbalances. Three women and six men from the U.S. Snowboard National Team, all racers, were tested for knee extension and knee flexion torque strength. All althletes were tested in concentric extension and concentric flexion at 60 degrees per second on a Cybex (6000) isokinetic dynamometer. Knee extension musculature was equally balanced between legs with an average torque of 212.42 ± 30.96 Newton*meters for the front leg knee extensors and 213.35 ± 32.62 Newton*meters for the rear leg knee extensors (p=0.44). Torque of the front leg knee flexors averaged 118.94 ± 20.78 Newton*meters, while torque of the rear leg knee flexors averaged 131.43 ± 35.39 Newton*meters (p=0.03). It is concluded that snowboard racing due to its asymmetric stance facilitates skeletal movements which lead to stronger rear leg knee flexors when compared to the front leg knee flexors, while front and back knee extensors are equal in strength. The rear leg knee flexors may be exercised to a greater degree due to the muscular actions involved in snowboarding, specifically steering, tip pressure, and/or ambulating on flat terrain. These muscular imbalances between front leg and rear leg knee flexors, if uncorrected, may lead to orthopaedic problems in the athlete's future.

LOWER LIMB FLEXIBILITY AND MUSCLE STRENGTH IN OSGOOD SCHLATTER DISEASE.

1819 BACKGROUND: Osgood-Schlatter Disease (OSD) is a result of microavulsions caused by traction of the patellar tendon on the tibial apophysis. We hypothesized that adolescent patients with OSD lack knee flexibility and may have an imbalance of muscle strength in the lower limbs. METHODS: 9 adolescents (mean age=11.8 yrs.) with OSD were matched for age, sex, height and weight with 9 adolescents with no known knee disease. Participants completed a questionnaire about type and frequency of sports participation. Quantitative static flexibility of the hamstring and quadriceps muscles was measured. Isokinetic knee extensor and flexor muscle strength was measured at speeds of 90,180,&360 degrees/second using a Biodex III system dynanometer. Peak torque and total work during isokinetic movement was calculated. RESULTS: A comparison of quadriceps and hamstring flexibility by goniometer between the OSD and control groups showed similar flexibility (mean 127.4 degrees and 129.6 degrees, respectively for quadriceps and 39.8 degrees and 41.2 degrees for hamstrings, p=ns). Subjects in the OSD group who engaged in sports more than three times a week (n=7) were significantly less flexible than the remainder (n=11) of the participants (mean quadriceps flexibility 141.1 degrees vs. 128 degrees, p<0.05). Isokinetic strength testing of bilateral knee extensor and flexor muscle groups was not significantly different between the OSD and control groups. However, the ratio of knee extensor strength to knee flexor strength was greater in affected knees of OSD subjects than in knees of controls. (Mean knee extension/flexion ratio in OSD subjects 73/30 ft.lbs=2.4, in controls 78/42 ft.lbs.=1.85, p<0.05). CONCLUSION: Lack of flexibility and strength imbalance of the leg muscles is associated with OSD. While this cross-sectional study cannot determine cause and effect, training aimed at improving the flexibility and balancing the strength of the leg muscle groups in adolescents may help prevent Osgood-Schlatter disease.

Sport-Specific Muscle Strength Imbalances in Tennis

Sport-Specific Muscle Strength Imbalances in Tennis

Maritime peace support operations in the Mediterranean

In spite of the significance of internationally‐legitimized peace support operations in the Mediterranean area since the second world war, the historical record testifies to the absence of intra‐Mediterranean security co‐operation. The functional attributes of maritime forces in facilitating co‐operative behaviour would appear to offer a means to overcome this. Currently, however, the prospects for co‐operation at sea continue to be limited by divergent political interests and structural factors such as the extra‐regional linkages of the largest naval powers, imbalances in naval strength and capability and the fragility of intra‐Mediterranean security frameworks. Steps to improve trans‐ and intra‐Mediterranean relations through participation in peace support operations are perhaps more likely to be achieved with regard to land‐based activities than at sea, given the growing involvement of Jordan and some of the Maghreb states in UN land operations. On the other hand, the potential for joint ocean management and constabulary co‐operation in non‐military security spheres could be exploited, leading in the longer term to confidence building and increased military transparency.