Did you know Erin Cuskelly is a qualified Bike Fit Instructor? She can improve comfort and power wattage on and off the bike. Check out her you-tube video.
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Craig and Andrew have done a podcast interview for the British Journal of Sports Medicine regarding their research into swimmer’s shoulder. Click on the link below to have a listen;
Craig and Andrew at the National Swimming Titles which were held in early April at Brisbane. They were there to present their research on ‘Swimmer’s Shoulder’ to the team of Australian Physio’s.
NHRU: Newcastle rugby referees face concussion test
Newcastle referees will have the power to sideline concussed players for 12 days under an Australian Rugby Union trial this season.
The ARU, responding to growing concern about the long-term effects of head knocks in contact sports, announced on Thursday that it would trial a “blue card” system in Newcastle and Canberra rugby before rolling out the system nationwide next year.
The on-field referee will have the authority to issue a blue card to “any player presenting signs of concussion”. The player must then leave the field for the rest of the match and cannot play again for at least 12 days, even if they pass a doctor’s concussion test. Juniors cannot play or train for 19 days.
“As there is no gold-standard test that a doctor can do post-match to reliably diagnose or exclude concussion in their rooms, the ARU errs on the side of caution,” the governing body said.
“A person with concussion can appear normal at rest (in the doctor’s rooms) but become symptomatic with activity. Therefore, a doctor can only conclude a concussion over time.”
Referees can already stop a game and send off concussed players, but Newcastle and Hunter Rugby Union general manager Andy Fairfull expected it to be more common now that officials had the visual cue of the blue card and more concussion training.
“It gets reported into the Rugby Link playing system . . . it’s now far stricter to get you back on the field,” Fairfull said. “They’re a little worried about the over-precautionary side of it, but given where it’s heading with law suits, and also it’s still truly unknown medically.
“I reckon with a blue card more will go off the field than last year, because the referees have had the training about recognition and they’ve got another card. It’s brought it into focus.”
Head knocks have been in the news after former Knights NRL winger James McManus launched legal action against Newcastle over the ongoing effects of repeated concussions. The NRL fined three clubs, including Newcastle, a total of $450,000 over their handling of concussed players in matches last weekend.
Fairfull predicted the new mandated 12-day break for blue-carded players would be a point of contention for NHRU clubs.
“Wait til it happens. I guarantee there’ll be uproar for days if a superstar misses out on the finals series,” he said. “But the evidence is that concussion management is the right way to go. You wouldn’t have these law suits in league if it wasn’t the right way to go. Players themselves are recognising the safety.
“We’re delighted to have the trial. We think it’s the right way to go. At some point in time, legally, injuries are going to start to become civil cases, clubs will get included on suits, associations will get included on suits.”
New Zealand is introducing blue cards to all club rugby this year after a trial in 2014. Its stand-down periods are 21 days for seniors and 23 for juniors.
Fairfull said the growing athleticism of club rugby players inevitably led to harder collisions.
“Rugby isn’t quite as savage [as league], but the fact still remains players are training more, they’re faster, stronger, but the field is still the same size.”
He said the increased pressure on referees to assess concussion was more a factor in junior ranks, where some referees are as young as 15.
“In chatting with the referees about it, they’re probably more worried about that issue in juniors, because in seniors, if it’s a Dan Kevill, you’ve got the best referees in the zone, they’re used to being under pressure, they’re used to being criticised, getting howled at.
“If you take some of these younger referees who are doing juniors and a parent starts ripping in. Their attitude to that pressure will be interesting. If we don’t get that behaviour back to the referees right, you’re cutting off young guys wanting to be referees.
“The blue card at the wrong time in an under-15 fixture can count out a superstar for finals. But it’s one of the issues: how do our younger refs learn it properly and execute it widely.”
Fairfull said it was not practical to have independent assessors at every game and the ARU was attempting to find a workable solution.
ARU medical and development staff have held seminars in recent weeks to educate NHRU referees, coaches and club medical staff on the system.
“The aim is to gather feedback from the upcoming trials and work towards rolling out the blue card system nationally across our grassroots competitions at both junior and senior level,” ARU chief medical officer Warren McDonald said.
Predisposing Risk Factors for Hamstring and Quadriceps Strain Injuries in Football (Soccer) and Rugby League Players
By: Phoebe Freeman
Background: This study was conducted to identify modifiable risk factors for hamstring and quadriceps muscle strain injuries in football and rugby league players.
Purpose: To identify possible associations between muscle strength, flexibility, body structure and static posture and hamstring or quadriceps muscle strain injury across a wide performance level.
Study Design: Prospective Cohort Study
Methods: A total of 294 football and 201 rugby league players ranging from amateur to professional performance levels were tested prior to the 2008 and 2009 playing seasons, through an Injury History Questionnaire and a battery of reliable physical assessments. Injury surveillance and exposure data were collected for the following playing season. Logistic regression analyses were conducted to identify independent predictors of hamstring or quadriceps strain injury in this study population.
Results: Nineteen and twenty-three players sustained a hamstring or quadriceps strain injury, respectively. Previous hamstring strain history or sitting height >141.4cm increased hamstring injury risk. Previous quadriceps strain history or slight knee flexion/hyperextension abnormality was independent predictors for quadriceps strain injury.
Conclusion: In a multivariate analysis, previous hamstring or quadriceps injuries were independent risk factors for sustaining hamstring or quadriceps strain injury, respectively. Further investigation, using multivariate models, is required to identify risk factors that are inter-related.
Clinical Relevance: Through the use of reliable pre-season measurement tests and standardized injury history and monitoring questionnaires, this study identified intrinsic risk factors for hamstring and quadriceps muscle strain injuries. This study may contribute to a greater understanding of the reasons for hamstring or quadriceps muscle strain and lead to future preventative or rehabilitative strategies.
Key Terms: hamstring injuries; quadriceps injuries; soccer; football; rugby league; prospective cohort study; risk factors
What is known about the subject: Both hamstring and quadriceps strain injuries have high incidence and recurrence rates in sports involving sprinting, kicking and changes of direction. Many injury risk factors have been proposed, however, few prospective cohort studies analyzing football or rugby league have been performed. Thus there is limited evidence implicating any particular risk factor for hamstring or quadriceps injury in these sports.
What this study adds to existing knowledge: This study investigated the predictive risk of strength, flexibility and static posture for hamstring and quadriceps muscle strain injury. The findings demonstrated an association between those players with a taller sitting height or previous hamstring injury history with an increased risk of sustaining hamstring injury. Players demonstrating slight knee hyperextension or with a previous history of quadriceps strain were at an elevated risk of quadriceps strain injury.
Non-contact hamstring and quadriceps muscle strain injuries are common in sports involving sprinting, jumping and changes of direction, such as football and rugby league [1, 5, 8, 19, 34, 43]. These strain injuries have a high prevalence in both sports [11, 23] with reports as high as 59% in professional football  and substantial adverse effects [27, 35]. For example, hamstring injuries lead to significant lost playing time in elite football players . They account for 12% of all football injuries, with a recurrence rate of 17%, and are the most common football injury to the lower extremity, resulting in an average of four games missed per injury . Similarly, hamstring muscle strains are the most prevalent lower extremity injury in rugby league, with 18 strains per 1000 playing hours. This impact is similar for quadriceps strains, with reports they comprise 25% of all lower limb injuries. Therefore identification of predisposing risk factors for these injuries is needed in order to develop injury prevention strategies [27, 35].
Many injury risk factors for hamstring or quadriceps injury have been proposed, however, few prospective cohort studies analyzing football or rugby league have been performed and thus there is limited evidence implicating any particular risk factor for injury in these sports [10, 29]. Controversy exists over the role of reduced absolute strength and strength imbalance in hamstring and quadriceps muscle strain injury [8, 33]. However, evidence supporting associations between isokinetic H:Q ratio and hamstring/quadriceps muscle strain is inconclusive when considered in isolation, regardless of different speed and contraction type . Furthermore, although limited flexibility has been associated with muscle strain injuries [5, 43], much controversy exists regarding the validity of the association [14, 16]. There are no identifiable conclusions whether increased or decreased flexibility is associated with particular muscle strains [5, 43] and thus further investigation is required. Core stability and posture have been recognized as key components of hamstring rehabilitation , however limited evidence suggests these are associated with injury risk . Thus, further investigation into the effects and interactions of flexibility, strength and static posture as risk factors for hamstring and quadriceps muscle strain injury is warranted [4, 15, 31] as the complete roles and possible predictive value of these factors are not fully understood [2, 3, 9].
The aim of this study was to determine whether an association exists between a number of proposed modifiable risk factors and hamstring or quadriceps muscle strain injury . Risk factors of particular interest were hamstring and quadriceps muscle strength and flexibility and spinal and lower limb posture. This study may contribute to a greater understanding of the reasons for hamstring or quadriceps muscle strain and lead to future preventative or rehabilitative strategies.
A total of 495 players aged 15 years or older were recruited from the Hunter Region of NSW, Australia prior to the 2008 and 2009 playing seasons. Players were from a range of performance levels: amateur or semi-professional football and amateur, semi-professional or professional rugby league. Approval was obtained from the University of Newcastle Human Research Ethics Committee and all players (parents of those under 18 years) provided written informed consent prior to participation.
Study design In this prospective cohort study, players attended data collection sessions during the pre-season where they completed questionnaires followed by a series of reliable physical measurements to assess lower extremity strength, flexibility and static posture. Injuries and exposure were monitored in games and training throughout the following season.
Questionnaires Players completed a sports injury history questionnaire, which included questions on previous injuries and any reported movement restrictions. An injury was defined as any hamstring/quadriceps injury, in the previous year that caused the loss of a week or more of their sport related training or playing activity. This timeframe was chosen to reduce recall bias associated with self- reported injury history.
Physical assessments Details of the physical testing procedures and the order of testing are provided in Table 1. An investigator with specific anthropometry training and experience conducted anthropometric measurements. A steel anthropometric tape (KDS measure) was used for girth and leg length measurements. Kinematic data were obtained using two-dimensional video analysis (Dartfish Connect v4.9, Dartfish, Fribourg, Switzerland), using a single video camera (Panasonic NV-GS180) on a spirit level tripod (Slick, 88S). A ceiling held plumb line calibrated true vertical.
Vertical Jumps Vertical counter movement jumps were assessed with double (DCMJ) and single (SCMJ) legs, with three maximal efforts recorded for each. Each jump effort was followed by 20-30 seconds of rest. A practice jump was allowed for each leg prior to SCMJ test performance. Players were required to wear shoes and were instructed to keep their hands placed on hips and to keep the leg(s) straight underneath their body while in the air for all jump tests. For SCMJ, players were instructed to keep the thigh of the non-working leg parallel to the floor, with the knee at 900 throughout the jump to further isolate the working leg. All vertical jumps were performed on a 70 cm x 100 cm computer-interfaced contact mat (Kinematic Measurement System, Fitness Technologies, Adelaide, Australia). Maximum peak power relative to body weight (W.kg–1) was calculated for each jump as: Peak Power (W) = 60.7x (jump height [cm]) + 45.3 x (body mass [kg]) – 2055 .
Lower extremity strength and stability were assessed with 100 incline single-leg squats.
Players performed a single leg squat without shoes on a 10° incline wedge placed on a flat 30cm high box. Players were instructed to squat as low as possible, while keeping the foot of the working leg flat on the platform. Arms were held in front of the body at shoulder height, with the non-working leg held in front of the body for balance. A test was repeated if the player’s heel lifted off the platform at any stage, the non-working leg touched the floor or the edge of the box, the player failed to return to the standing position in full control or the player fell off the box. At each player’s lowest squat position, the sagittal ankle angle between the lower leg and the floor surface and knee angle were determined. A small ankle angle indicates greater ankle dorsiflexion, while a large ankle angle indicates less dorsiflexion range of motion (ROM).
Lower limb ROM measurements assessed flexibility as follows: the Modified Thomas Test (MTT) for iliopsoas and quadriceps length , Active Knee Extension (AKE) for hamstring length and a combined MTT and AKE test to investigate the interaction between anterior and posterior hip musculature. Tests were performed in the same order, beginning with the right leg, followed by the left leg before moving on to the next test.
Figure 1 demonstrates the start and end positions of the MTT. The player maintained one leg in full flexion with their arms in the frontal plane while the contralateral limb was lowered slowly until hanging relaxed off the edge of the test bench. In this position, thigh-to-vertical was measured to represent the hip angle, with a smaller thigh-to-vertical angle indicating reduced iliopsoas flexibility. Knee-angle was the angle between a line intersecting the greater trochanter and knee joint axis at the head of the fibula and a line intersecting the lateral malleolus and knee joint axis (Figure 1b). A larger knee- angle represents reduced quadriceps flexibility. The assessor monitored frontal plane hip movement to ensure the lower extremity remained in the sagittal plane.
The AKE protocol of Gajdosik and Lusin  was modified for this study. A femur stabilizing apparatus (Figure 2) was used to ensure the hip remained at 90° throughout the test. Participants rested one knee on the apparatus with the hip at 90° and extended the knee with the ankle in neutral dorsiflexion, while the opposite leg rested on the bed (Figure 2). Knee angle was measured as per MTT and was obtained at a participant’s greatest extension without the contra-lateral leg lifting from the table. A smaller knee angle represented reduced hamstring flexibility.
Hamstring and contralateral iliopsoas interaction was investigated using a MTT from a standardised, braced position , immediately followed by an active knee extension  of the contra-lateral limb. Participants were positioned as previously described for the AKE test, however the player was placed closer to the edge of the test bench so the resting thigh was suspended rather than resting on the bed (Figure 3). Combined MTT/AKE was calculated for analysis by adding the AKE (knee angle) of the extended knee with the MTT (knee angle) of the hanging limb.
Four digital photographs (Pentax, Optio M30) assessed static posture: 1) anterior view, 2) lateral view, 3) lateral view (arms across chest) and 4) posterior view. A measurement scale by Watson and Mac Donncha  was used to assess possible postural deviations listed in Table 2. A single assessor scored all posture photographs for consistency.
Players were placed on a small box (5.5cm high), feet were to be touching (if possible) and centrally aligned for all photos. Players were asked to stand in their normal posture, looking straight ahead with arms relaxed by the side for all photos except the lateral view.
Injury and Exposure Monitoring
Conditioning staff (coach or manager) completed two questionnaires throughout the study period. One questionnaire was completed each month to obtain a player’s exposure to training, competition and minor injuries (no lost playing or training time). The second questionnaire recorded hamstring and quadriceps muscle strain injuries that caused a player to miss a subsequent game or training session. Specific information regarding the injury was recorded including location and mechanism of injury. An exposure diary was maintained for the duration of each competition season. For training exposure the date, length of session (minutes) and the number of players present was recorded. Total squad training exposure was extrapolated from the recorded figures. Game exposure was recorded as: total number of season games played x hours of play x players on field. Total exposure for the squad (training + game) was averaged across squad members for analysis.
Descriptive statistics were used to describe the characteristics of the study population. Continuous variables were ranked and categorized into tertiles for analysis to improve the clinical interpretation of the results. Tertiles separated test results into performance categories considered to be “poor”, “moderate” and “good.”
Bivariate and multivariate analyses assessed the relationship between pre-season measurements and the occurrence of hamstring and quadriceps muscle strain injury. Chi-squared analyses identified differences between pre-season variables between injured and uninjured players. Fisher’s exact tests were performed when Cochran’s criteria was not met (cells with less than five observations). For each chi-squared test, the odds ratio (OR and 95% CIs) for sustaining an injury was calculated relative to the chosen reference category.
A backward stepwise binary logistic regression, based on a likelihood ratio method, was used to identify the factors that were independent predictors of hamstring injury. A separate regression was performed for quadriceps injury. Variables with a p< 0.20 from the Chi-square were included in the regression models at the first step and the models were adjusted for exposure (hours of match play and training for the season). For each model, odds ratios and 95% CI were calculated. Where the confidence interval did not contain the null value (OR= 1.0), the OR was taken as being significant (p < 0.05). The goodness of fit of the prediction model was assessed using the Hosmer-Lemeshow statistic.
T-tests were used to investigate this association. Single leg squat joint ROM angles (mean of both limbs) were compared to examine between group difference in functional strength among athletes displaying slight postural deviations (hyperextension/flexion) compared to those with lower limb posture considered to be “ideal”.
All analyses were performed using SPSS for Microsoft Excel (Version 19) (SPSS Inc, Chicago, Illinois, USA).
The median (range) age of players was 17.7 (15.0- 34.0) years with no significant difference between sports. The median weight of players was 76.2 (32.5- 121.5) kg, with a statistically significant difference (p< 0.00) between soccer and rugby league players (71.0 and 89.6kg, respectively) hence the multivariate model was adjusted for sport. A total of 19 hamstring strain injuries (football= 9 (0.24/1000 exposure hours); rugby league= 10 (0.24/1000 exposure hours) and 23 quadriceps strain injuries (football= 8 (0.21/1000 exposure hours); rugby league= 15 (0.36/1000 exposure hours)) were reported within the study period. Injury incidence was influenced by performance level for quadriceps (high= 19; low= 4; p= 0.074) but not for hamstring strain injuries (high= 13; low= 6; p= 0.632).
Hamstring Strain Injury
Results of the bivariate analyses, which identified associations between proposed risk factors and sustaining a hamstring strain, are detailed in Table 3.
Leg length, sitting height, dorsiflexion (DF) lunge, AKE, squat ankle angle, posture score and previous injury met the criteria for inclusion into the multivariate analysis. Squat ankle angle was not included in the model due to a strong inverse correlation with DF lunge (R = -0.600; p= 0.001). The DF lunge test was entered into the multivariate model, as this was considered a more clinically relevant test.
Table 4 summarises the results of the multivariate logistic regression analysis. The Hosmer-Lemeshow statistic for goodness of fit was 3.799 (p= 0.875).
Quadriceps Strain Injury
Results of the bivariate analyses for quadriceps strain injury are detailed in Table 5. Sport, performance level, DF lunge, full range, knee hyperextension, kyphosis and previous injury met the criteria for inclusion into the multivariate analysis. Table 6 summarises the results of the multivariate logistic regression analysis. The Hosmer-Lemeshow statistic for goodness of fit was 6.670 (p=0.464). Players at the professional level were at slightly increased risk of quadriceps strain injury (OR= 1.729; p= 0.529) but this was not statistically significant.
Despite the extent of research into hamstring and quadriceps injuries in both football and rugby league, few studies have used multivariate prospective analysis to investigate potential risk factors . Through the use of reliable pre-season measurement tests and standardized injury history and monitoring questionnaires, this study was able to identify a number of intrinsic risk factors for hamstring and quadriceps strain injuries. Unlike previous studies, these findings did not find that age was associated with increased hamstring [1, 9, 14, 15, 19, 31, 39, 40] or quadriceps [1, 19, 31, 40] injury risk.
Previous injury history (sustained within the previous 12 months) was shown to be an independent risk factor for subsequent hamstring and quadriceps strain injury. These findings are in agreement with a number of prospective [1, 9, 14, 15, 19, 31, 39, 40] and retrospective [1, 31, 39, 40]cohort studies. Previous injury may alter the mechanics of the lower extremity for long periods of time after the disappearance of injury symptoms, resulting in ongoing injury risk . As a player’s injury history cannot be modified and the factor causing the initial injury may still be present, further investigation is required to identify modifiable risk factors associated specifically with these players. These risk factors may be a result of deficits sustained through injury, the healing process, premature return to sport or insufficient rehabilitation. One previous prospective study  found that previously injured muscles were at a greater susceptibility for further damage, due to a shorter optimum length for active tension, compared to uninjured muscles . Clinically, it is important to determine why athletes with history of strain injury have smaller optimum angles and how these can be increased to reduce the risk of re-injury [27, 35].
The effect of the lever arm (measure of trunk length) on hamstring strain in footballers has not been previously investigated. The current study found that a greater sitting height was associated with an increased injury risk. The majority of hamstring strain injuries occur during terminal swing and ground contact during sprinting [32, 34], actions requiring the hamstrings to actively lengthen and functionally change from eccentrically decelerating knee extension to concentrically extending the hip [4, 7, 34]. Thus, running places the hamstrings in an anatomically vulnerable position . Athletes with a longer trunk height may be more susceptible to hamstring strains in situations requiring them to forward flex from the hip while running, as this requires greater anterior pelvic tilt . This potentially places greater strain on the hamstrings, increasing the risk of injury as demonstrated in the current study.
This is the first study to identify associations between knee flexion/hyperextension posture and quadriceps strain injury. Players with this slight abnormality have a 3.9 times greater risk of sustaining a quadriceps strain compared to those with normal knee extension. Subsequent deficits of genu recurvatum have been previously investigated [26, 37]. Players presenting with knee hyperextension abnormalities may have functional strength deficits and will be unable to control terminal knee extension in the weight-bearing position . An investigation of functional strength, using the 100 incline squat, demonstrated players with knee flexion/hyperextension abnormalities had a larger mean knee angle (1150 ± 16.20), compared to players with normal knee extension (107.60 ± 15.90) (p= 0.034). A larger knee angle demonstrates a player’s inability to descend to a lower level, suggesting reduced functional strength. This finding concurs with previous studies [26, 37] and therefore, further prospective studies are required to determine causality of knee hyperextension and quadriceps strain injury.
There are a number of strengths to this prospective study including the identification of potential causal relationships. The study design enabled analysis of a large study population (n= 495) over a wide performance level and different codes of football, using reliable measurement tests. However, a number of study limitations must be acknowledged. The incidence of injury in this study was lower than that previously described in the literature. This could be attributable to the large sample size and inclusion of amateur athletes. The lower incidence rate is comparable to that of previous studies . Injury rates for amateur athletes may be significantly lower compared to elite, however further investigation is required to confirm this hypothesis.
Club personnel were responsible for injury diagnosis and thus injury monitoring was limited to the experience of these personnel. Due to analysis of a broad sample of athletes, it is possible that the injury diagnosis differed between personnel, creating potential bias.
While exposure hours were collected for teams, these could not be recorded for individual players due to the large population size and inclusion of community-level football.
Despite a relatively large sample cohort, the small percentage of injuries recorded during the study period reduces the power to detect small-to-moderate associations between the potential risk factors studied and hamstring or quadriceps injury [2, 15]. While these results may not be directly transferable to other sporting populations, sprinting and kicking, where the majority of hamstring injuries occur, are fundamental actions for a number of sports and thus consideration should be given to the findings of this study.
Findings from this prospective cohort study demonstrated an association between those players with a taller sitting height or previous hamstring injury history as well as slight knee hyperextension or previous history of quadriceps strain with an increased risk of sustaining a new hamstring or quadriceps injury, respectively. Further investigation, using multivariate models, is required to identify risk factors that are inter-related. This information would potentially allow researchers and practitioners to implement evidence-based strategies to prevent injuries from occurring, thus reducing the impact of these injuries on both the player and their teams.
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Having been a competitive swimmer in the 1980’s who suffered unresolving shoulder pain I understand the frustration experienced by swimmers who are plagued by this common injury. I am happy to say our ability to prevent and treat shoulder pain in swimmers has progressed markedly from all those years ago. We now have a much better understanding of the many factors that can contribute to this condition including training volume, loss of specific shoulder range, glenohumeral laxity, scapula dyskinesis and incorrect stroke mechanics. When these factors are thoroughly addressed in swimmers with shoulder pain many experience resolution of their symptoms.
Despite this progress shoulder pain is an ongoing issue for our elite level swimmers. In a survey of over 100 of Australia’s best swimmers this year 70% reported having experienced shoulder pain with swimming at some stage, with 28% indicating that their shoulder pain was an ongoing issue, and 21% experiencing some degree of discomfort at the time of questioning. Athletes reported their symptoms significant enough to cause them to modify or stop training for a period of time and in some cases to require surgical intervention. So while we have progressed in our knowledge over the years we continue to have elite level swimmers plagued by ill-defined recalcitrant shoulder pain and there is still work to be done. Recent attention to shoulder strength balance using hand held dynamometry (HHD) is yielding interesting results and is proving to be a valuable tool for assessment and insight into varied sub-groups within the population of swimmers suffering shoulder pain, and in their ongoing monitoring and management.
Previous researchers have determined that swimmer’s internal rotation (IR) strength may become excessively greater than external rotation (ER) due to the predominantly IR loading created during swimming [1, 2-5], thus resulting in a loss of humeral head control with potential superior migration, impingement and resulting shoulder pain. To investigate this further, physiotherapists working with Australia’s elite swimmers, including the 2012 Olympic team, have been performing regular HHD to examine shoulder rotation force generation with the aim of documenting strength ratios and address any imbalances if identified.
HHD measurements have been made with subjects standing, the elbow by the side but not touching the body and flexed to 90°. The dynamometer was placed aligned with the ulnar styloid process on the dorsal side of the forearm for ER and the palmar side for IR measurements. Subjects were asked to brace themselves by separating their feet and bending their knees in order to avoid losing balance during testing. The force was applied gradually and increased to ‘breaking’ the isometric resistance given by the subject, and the maximum measure of three measures for each direction was used in analysis.
In previous research on swimmers performed isokinetically on Cybex or Kin-com dynamometers, the IR:ER reported have varied from 1.25 to 1.62 [3, 5, 6] and as high as 1.9 , with differing results being due to variations in subject positioning and speed of rotation during testing. Using the HHD technique described we found our asymptomatic subjects on average recorded an IR:ER ratio of 1.41(+/- 0.14SD). With ongoing data collection it appears that a ratio between 1.2 and 1.6 is optimal for normal shoulder function in swimmers and if outside this range they are likely to experience shoulder symptoms. The data collected provides further evidence for the importance of addressing the causes of imbalances in shoulder rotation strength in managing swimmers’ shoulder pain.
Our data indicate that as well as monitoring a swimmer’s shoulder IR:ER ratios, normalised rotation strength levels should also be calculated as they too may be predictive of injury. When expressed as a percentage of bodyweight male swimmers with no history of shoulder pain averaged approximately 30% for IR (31.4% +/- 4.3 SD and 31.0% +/- 3.8 SD for right and left shoulders respectively) and approximately 20% for ER (21.4% +/- 2.3SD and 21.3% +/- 3.3 SD for right and left shoulders respectively). In females this was slightly lower at approximately 26% for IR (26.9% +/- 3.3 SD and 25.9% +/- 3.9 SD for right and left shoulders respectively) and approximately 18% for ER (18.2% +/- 2.7 SD and 18.3% +/- 2.8SD for right and left shoulders respectively). Therefore, while a swimmer may have an acceptable IR:ER ratio their normalised strength levels may be low. Ongoing data collection and injury history suggests that normalised strength levels may be an important factor to consider in swimmers becoming susceptible to shoulder symptoms, with several of the symptomatic swimmers falling well short of these figures. Further evidence of the importance of achieving and maintaining adequate gross shoulder rotation strength has been the finding that swimmers with unilateral shoulder pain show low force production with testing on their contralateral non-symptomatic shoulder, suggestive that a loss of force on the symptomatic side was present prior to the onset of symptoms.
As has been reported in past research, our testing has been able to identify individuals who produce increased IR relative to ER force during testing, indicated by a high IR:ER ratio. This relative change was seen to occur as a result of increased IR force in some swimmers, but also from a reduction in ER force production most likely as a result of posterior cuff pathology. Given the high incidence of supraspinatus pathology identified in swimmers  this has not been surprising. What has been of greater interest, however, has been the number of symptomatic swimmers recording reduced IR force measures. (See Figure 1 for example). This indicates a distinct clinical sub-group in swimmers suffering shoulder pain, and by its nature would require a management program different from that for other sources of swimmer’s shoulder pain. The reason for a reduction in generated IR force is not clear, however, it is hypothesized that it may arise as a result of training overload and fatigue, with pathology developing in the shoulder internal rotating musculotendinous structures. Recent electromyography research has shown that subscapularis can act as a major torque producer during shoulder IR  and a glenohumeral joint stabilizer during shoulder extension , the predominant movements performed during the pull phase of most swimming strokes. Subscapularis overload leading to the development of pathology would explain a reduction in IR force in an elite swimming population. Anecdotal evidence of swimmers who have ultimately undergone shoulder surgery for ongoing symptoms with identified subscapularis pathology may be further evidence for this proposed mechanism.
If the loss of IR force is due to fatigue it may be possible that this phenomenon only occurs in swimmers performing large volumes of training. The current data have been collected from a group of elite level swimmers with many regularly training 50 kilometres or more per week. Therefore the likelihood of some of these subjects being susceptible to fatigue would be higher than for a recreational swimmer. Whether reduced IR force generation occurs, or is as common in less elite swimmers will only be answered with future studies examining swimmers of various levels.
Several recommendations can be made from the findings of this study. First, swimmers should be routinely examined with HDD to ensure that their shoulders are maintaining an appropriate IR:ER ratio and normalised force production in their internal and external rotators. Identifying loss of force generated in either IR or ER may assist in diagnosing the source of symptoms and, therefore, implementing the most appropriate management plan. Changes in shoulder rotation ratios may be used to give direction to coaches on the appropriate swimming volume and intensity for their swimmers, particularly those swimmers with reduced IR force given that this loss may be directly workload related. Ongoing research is currently being undertaken with the AIS swim program to determine the relationship between workload and rotation force measures, which will provide further detail on the potential for us to provide coaches with this information based on our HHD measures. Furthermore, it is generally more common for clinicians and coaches to suggest to swimmers to work on ER strengthening to assist with maintaining shoulder strength balance. These preliminary results would suggest that maintaining adequate shoulder IR strength can be equally important, so dry land training should also focus on gaining strength and potentially greater ‘resilience’ within the internal rotating musculotendinous structures. How best to retrain strengths deficits of the shoulder once identified is an area beyond the scope of this article, but it is a protracted process with gains being made slowly. Again, HHD is of value by providing an objective and accurate measure with which to monitor progress.
By the nature of swimming, there will always be the potential for shoulder injury. The hope is that with further examination of the value of tools such as HHD and the results of other investigations currently being undertaken with our elite swimmers, we will be better able to give direction in preventative measures to avoid shoulder injury, better predict its potential onset and provide improved injury specific rehabilitation should it occur. At this stage there appear to be encouraging signs that we are heading in the right direction.
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Figure 1. Graph of external rotation and internal rotation force production for the right shoulder of female members of the 2012 Australian Olympic swim team. Units are in kilograms. Swimmers’ shoulders were classified as symptomatic if, in the 12 months prior to testing, symptoms were significant enough to cause cessation of training for any period of time. Note the symptomatic shoulders show a greater tendency toward reduced internal rotation force production in comparison with asymptomatic shoulders.
Stress fractures are a relatively common issue in athletes of all levels, particularly in those sports that require repetitive loading such as running. It is suggested that 95% of stress fractures occur in the lower limbs; in runners they account for 15-20% of injuries (Wright et al 2015)