Rotator Muscle Strength Research Articles

Preseason Strength Assessment of the Rotator Muscles and Shoulder Injury in Handball Players.

Few researchers have identified intrinsic risk factors for shoulder injury in team handball players by analyzing measurements of maximal isokinetic rotator muscle strength. To identify possible intrinsic risk factors for shoulder injury by analyzing measurements of maximal isokinetic rotator muscle strength. Cross-sectional study. Male team handball senior divisions (the highest level) in France and Belgium. A total of 108 male high-level handball players (age = 24 ± 4 years, height = 189 ± 6 cm, mass = 87 ± 11 kg) were enrolled. All players completed a preseason questionnaire and performed a bilateral isokinetic assessment of the shoulder rotator muscles. On a monthly questionnaire, players reported any shoulder injury that they sustained during the season. On the preseason questionnaire, 51 of 108 (47%) participants reported a history of dominant-shoulder injury. A total of 106 participants completed the in-season questionnaire, with 22% (n = 23) reporting a shoulder injury on their dominant side during the subsequent season. Fourteen percent (n = 15) sustained microtraumatic injuries, and 8% (n = 8) described a traumatic injury. Backcourt players had a 3.5-times increased risk of injury during the new season compared with players in other positions. Among the isokinetic results, no risk factor for further injury was identified in handball players with microtraumatic injuries. For traumatic injuries, the concentric maximal strength developed by the internal rotators at high speed (240°/s) in the dominant shoulder was a protective factor against the risk of further injury. These results can potentially identify intrinsic risk factors for shoulder injury and may be used to determine potential interventions for reducing this risk in handball players.

Recovery of Shoulder Rotational Muscle Strength After Arthroscopic Bankart Repair.

Background:Shoulder rotational muscles act as dynamic stabilizers of the glenohumeral joint, and the recovery of muscle strength plays an important role in stabilizing the joint during postoperative rehabilitation. However, temporal changes in muscle strength after arthroscopic Bankart repair have not been clarified.Purpose:To better understand the temporal recovery of shoulder rotational muscle strength after arthroscopic Bankart repair.Study Design:Case series; Level of evidence, 4.Methods:Isokinetic concentric shoulder rotational muscle strength was evaluated in 50 patients who were diagnosed with recurrent dislocations of the glenohumeral joint and treated with arthroscopic Bankart repair.Results:The mean peak torque/weight and total work were reduced significantly at 1.5 months after surgery (P < .0001) and returned to preoperative levels by 6 months for external rotation and 4.5 months for internal rotation. The contralateral peak torque ratios reached preoperative levels by 6 months after surgery. The ipsilateral peak torque ratios were reduced between 1.5 and 3 months after surgery and returned to preoperative levels at 6 months for external rotation and 4.5 months for internal rotation.Conclusion:Isokinetic shoulder rotational muscle strength after arthroscopic Bankart repair recovered to preoperative levels by 6 months for external rotation and 4.5 months for internal rotation.

Wrist movements during isokinetic assessment of muscle rotators of the shoulder

The assessments of the internal (IR) and external (ER) rotator muscle strength of the shoulder are often studied from a hand held accessory gripped. In these conditions, even if the wrist is in alignment with the radius, it is not possible to eliminate any compensatory movements of the wrist during maximal contractions of the shoulder muscle rotators. The objective of this study was to investigate the movements of the wrist in flexion/extension during an isokinetic assessment of the strength of shoulder rotators. Twenty-two healthy participants were explored. Participant previously installed in a seated position, the shoulder test was performed for IR and ER in concentric (CON) and eccentric (ECC) modes on each shoulder (dominant: D; non-dominant: ND), at 60°/s and 180°/s using an isokinetic dynamometer and an electronic goniometer fixed on the wrist. Data acquisition was recorded continuously and calculated with an analysis software. No significant difference founded in wrist mobility depending on muscle groups (IR or ER) and laterality (D or ND) whereas dominant PT was higher at all velocity for ER (in CON and ECC modes) and for IR ECC. No significant correlation between the movements of the wrist and the strength parameters was shown. However, the wrist movements were greater in the concentric modality ( P < 0.05). In addition, we observed a significant difference ( P < 0.05) between angular velocities for the ND side, with greater movements at low speed (60°/s). These results highlight compensation strategies of the wrist during isokinetic assessment of the shoulder depending on modality of contraction with a locking strategy in ECC mode, and angular velocity selected. To conclude, isokinetic assessment is to evaluate the muscle potential of an isolated joint by limiting the compensation, but it is important to focus on the surrounding joints due to the fact that the human body is a set of interacting segments with interconnected influences.

Posture and isokinetic shoulder strength in female water polo players

Background: Being overhead athletes, water polo players can present with muscular imbalances of the shoulder, between the internal rotators (IR) and external rotators (ER), leading to changes in posture and an increased risk of injury.Objectives: To assess posture and isokinetic shoulder strength of female club-level water polo players.Methods: A descriptive study assessing posture and isokinetic strength of the IR and ER shoulder muscles in 15 female club-level South African water polo players (age: 21.3 ± 1.5 years) was conducted. Posture was assessed using a posture grid. Isokinetic shoulder rotator muscle strength was tested over five repetitions concentrically and eccentrically at 60°/sec using a Biodex system 3 isokinetic dynamometer. The bilateral, reciprocal and functional dynamic control ratios (DCR) were calculated.Results: Typical postures noted were a forward head, rounded shoulders, increased thoracic spine kyphosis, elevated non-dominant shoulder and mild scapula winging. The mean concentric reciprocal ratios for the dominant (52.2 ± 7%) and non-dominant (51.9 ± 6.4%) sides indicated ER muscle weakness. DCR values were within normal limits for the group. (D: 0.75 ± 0.2 and ND: 0.75 ± 0.1).Conclusion: There is a trend for these female water polo players to have rounded shoulders and forward head postures, as well as ER muscle strength weakness, the combination of which could predispose the athletes to shoulder injury.

CSM 2017 Orthopaedic Section Platform Presentations (Abstracts OPL1–OPL64)

CSM 2017 Orthopaedic Section Platform Presentations (Abstracts OPL1–OPL64)

Sling-based Exercise for External Rotator Muscles: Effects on Shoulder Profile in Young Recreational Tennis Players

Context: Tennis playing generates specific adaptations, particularly at the dominant shoulder. It remains to be established whether shoulder strength balance can be restored by sling-based training for adolescent recreational tennis players. Objective: We added a sling-based exercise for shoulder external rotators to investigate its effects on external rotator muscle strength, on internal rotator muscle strength, on glenohumeral range of motion and on tennis serve performance. Design: Test-retest design. Setting: Tennis training sports facilities. Participants: Twelve adolescent male players volunteered to participate in this study (age: 13.3 ± 0.5 years; height: 1.64 ± 0.07 cm, mass: 51.7 ± 5.8 kg, International Tennis Number: 8). Intervention: The procedure spanned 10 weeks. For the first five weeks, players performed their regular training (RT) twice a week. For the last five weeks, a sling-based exercise (SE) for strengthening the shoulder external rotator muscles was added to their regular training. Main Outcome Measures: Maximal isometric strength of shoulder external and internal rotator muscles and glenohumeral range of motion in external and internal rotation were assessed in both shoulders. Serve performance was also evaluated by accuracy and post-impact ball velocity, using a radar gun. Results: No change was found in any measurement after the RT period. Significant increases in external (~+5%; p<0.001) and internal (~+2%; p<0.05) rotator muscle strength and in external/internal strength ratio (~+4%; p<0.001) were observed after the SE period. Serve velocity and accuracy were significantly improved after SE (~+2% and ~+24%, respectively; p<0.05 for both), while no clinically meaningful alterations in ranges of motion were observed. Conclusions: Prophylactic intervention through sling-based exercise for strengthening shoulder external rotator muscles appears effective in restoring strength balance at the dominant shoulder, and may prevent adolescent tennis players from sustaining degenerative shoulder problems which could later impair their performance of daily and work-related tasks.

Hip muscle strength and static balance in patients with snapping hip syndrome – a pilot study

Abstract Introduction: Snapping hip syndrome (SHS) occurs in 5-10% of the global population. A back and forth skip of the tendon of the dysfunctional muscle across the osseous prominence is the most common symptom of this condition. Mainly young generation suffers from SHS. Depending on the structures that cause an audible snap, snapping hip syndrome may be classified into intra-articular and extra-articular types. The main aim of the research was to assess the strength of the major hip muscles and static balance in patients with snapping hip syndrome. Material and methods: The research was carried out on 10 untrained females and 10 untrained males with extra-articular snapping hip syndrome. An average age was approximately 25 years. The research was conducted with the use of interview questionnaire, clinical examination, balance assessment on the JBA Staniak 4P dynamometric platform and measurements of the hip muscle strength on the JBA Staniak SPB2 set. Results: Patients with SHS manifested an increased tension in iliotibial band, while significant weakening of internal and external rotator muscle strength was noted in women and significant weakening of external rotator muscle strength was observed in men. No correlations between hip muscles strength and stabilographic test results in patients with snapping hip syndrome were found. Conclusions: Individuals with SHS and healthy persons demonstrate similar balance levels. The treatment of snapping hip syndrome should include: 1) restoring internal rotator muscle strength in women, 2) restoring external rotator muscle strength both in women and in men, as well as 3) restoring iliotibial band flexibility.

Effect of exercise-based management on multidirectional instability of the glenohumeral joint: a pilot randomised controlled trial protocol.

IntroductionThe most commonly recommended treatment for multidirectional instability (MDI) of the shoulder is exercise. Despite this recommendation, there is limited evidence to support the effectiveness of exercise. The aim of this paper is to describe a pilot randomised controlled trial comparing the effectiveness of 2 exercise programmes on outcomes of participants with MDI.Methods and analysisConsenting participants between 12 and 35 years, with non-traumatic MDI will be randomly allocated to participate in either the Rockwood Instability programme or the Watson MDI programme. Both programmes involve 1 consultation per week for 12 weeks with a physiotherapist to prescribe and progress a home exercise programme. Outcomes will be assessed at baseline, 6, 12, 24 and 52 weeks. Primary outcome measures include the Melbourne Instability Shoulder Score and Western Ontario Shoulder Index. Secondary outcomes include scapular coordinates, scapular upward rotation angles, muscle strength, symptomatic onset, limiting factor and angle of limiting factor in abduction range, incidence of complete glenohumeral joint dislocation, global rating of change, satisfaction scores, the Orebro Musculoskeletal Pain Questionnaire, adverse events and compliance with the home exercise programme. Data will be analysed on intention-to-treat principles and a per protocol basis.DiscussionThis trial will evaluate whether there are differences in outcomes between the Rockwood and the Watson MDI programmes for participants with MDI.Ethics and disseminationParticipant confidentiality will be maintained with publication of results. Ethics approval: Faculty of Health Sciences (FHEC12/201).Trial registration numberACTRN12613001240730; Pre-results.

Does grafting of the tuberosities improve the functional outcomes of proximal humeral fractures treated with reverse shoulder arthroplasty?

Functional outcomes of reverse total shoulder arthroplasty (rTSA) can be improved by fixation of the tuberosities. This study compares clinical and radiologic results of patients with comminuted proximal humeral fractures treated with rTSA, with and without autologous grafting. Thirty-three patients with proximal humeral fractures were treated with rTSA and tuberosity fixation. In 18 patients (group I; mean age, 75 years), tuberosity fixation was augmented with autografting; in 15 patients (group II; mean age, 71 years), graft augmentation was not used. The mean follow-up was 16.7 (range, 12-24) months in group I and 16.8 (range, 12-25) months in group II. Radiologic tuberosity union was achieved in 14 of 18 (77.8%) patients who underwent autograft augmentation and in 6 of 15 (40.0%) patients treated without autografting. The mean American Shoulder and Elbow Surgeons (ASES) score was 69.6 ± 13.0 in group I and 51.0 ± 20.0 in group II. The mean Disabilities of the Arm, Shoulder, and Hand (DASH) score was 31.9 ± 24.0 in group I and 58.2 ± 24.6 in group II. A significant difference was detected between groups for ASES and DASH scores. Among shoulder range of motion measures, only forward flexion differed significantly between groups I and II (124° ± 23° vs. 98° ± 30°, respectively). External rotation muscle strength was significantly higher in group I (3.36 ± 1.46 kg) than in group II (2.39 ± 2.00 kg). In the treatment of complex proximal humeral fractures in elderly patients by rTSA, cancellous block autograft augmentation can increase the rate of tuberosity union and improve functional outcomes.

Effect of fatigue caused by a simulated handball game on ball throwing velocity, shoulder muscle strength and balance ratio: a prospective study.

BackgroundArm throwing represents a deciding element in handball. Ball velocity, aim accuracy, and dynamic stability of the shoulder are factors that influence throwing effectiveness. The purpose of this study was to examine the influence of muscle fatigue caused by simulated game activities (SGA) on shoulder rotational isokinetic muscle strength, muscle balance and throwing performance, and to examine the relationship between muscle strength and throwing performance.MethodsTen national elite adult handball athletes were evaluated. Isokinetic internal (IR), external (ER) rotators peak torque, and balance ratio were measured before and after SGA. Ball throwing velocity was assessed by radar gun.ResultsBoth internal (IR) and external (ER) rotators peak torque were significantly lower after SGA (p = 0.0003 and p = 0.02, respectively). However, the deleterious effect was more evident for IR than ER muscles (effect size r = 0.39 and r = 0.18, respectively). Balance ratio before and after SGA did not differ (p = 0.06). Ball throwing velocity was not impaired by SGA. Moreover, isokinetic variables correlated positively with ball velocity (r ≥ 0.67).ConclusionsSGA affected the muscle strength of IR more than ER, predisposing the shoulder joint to muscular imbalance. The muscular impairment after SGA was insufficient to impair ball throwing velocity.Electronic supplementary materialThe online version of this article (doi:10.1186/s13102-016-0038-9) contains supplementary material, which is available to authorized users.

Do changes in hand grip strength correlate with shoulder rotator cuff function?

Shoulder pain as a result of rotator cuff pathology is one of the most common musculoskeletal complaints presenting within primary care. Assessment of hand grip strength has been proposed as an indicator of rotator cuff function. This experimental study assessed the relationship between grip strength and shoulder lateral rotator muscle strength in a number of different shoulder positions, aiming to investigate whether such a relationship existed and whether grip strength could be used as a functional assessment tool for the posterior cuff. Twenty-seven healthy, physically active, volunteers (19 males, eight females) with no history of shoulder, upper limb or neck injury comprised the study group. The mean (SD) age was 19.8 (5.7) years (range 18 years to 23 years). Grip strength (measured with hand grip dynamometer) and lateral rotator strength (measured with a hand held dynamometer) was measured at neutral, 90° abduction, and 90° abduction with 90° external rotation. The correlation between grip strength and shoulder lateral rotation strength ranged between r = 0.91 (r (2 )= 0.84) and r = 0.72 (r (2 )= 0.52) across all positions. A strong correlation between grip strength and lateral rotator strength was shown at all positions for both left and right hands, suggesting that assessment of grip strength could be used as a rotator cuff monitor of recruitment function.

Reliability and Validity of EN-TreeM Dynamometer for Measurement of Shoulder Rotator Strength in Volleyball Players.

Volleyball involves repeated forceful arm actions that produce a high incidence of shoulder injury. Shoulder rotator strength ratio is an important predictor of the likelihood of shoulder injury, especially, secondary shoulder impingement and instability. Therefore, assessment of muscle strength of external and internal rotators of shoulder is imperative to establish the profiles of shoulder rotator performance, strength ratios, and shoulder mobility of volleyball players. To establish reliability and validity of EN-TreeM dynamometer for the measurement of shoulder rotators strength in volleyball players. Thirty male volleyball players aged 18-24 years, mean height 1.7m, weight 69.8 Kg and BMI 23.1 participated in the study. They performed 1RM (one repetition maximum) estimation protocols using EN-TreeM dynamometer and free weights for shoulder rotators, to investigate its concurrent validity. A retest using the same protocol was performed 48 hours later to assess test-retest reliability of the EN-TreeM dynamometer. The results yielded excellent test-retest reliability (ICC0.96) and internal consistency (Cronbach's alpha0.98) for both internal and external rotators. The concurrent validity was established using Pearson correlation coefficient (internal rotator r=0.45, p=0.01;External rotator r=0.38, p=0.03). The findings establish the reliability and concurrent validity of EN-TreeM dynamometer for the quantification of shoulder rotators strength. Based on these findings in volleyball players, EN-TreeM dynamometer can be used with confidence as an instrument for assessing muscle performance (strength). Additionally, it may also be used for monitoring changes due to rehabilitation interventions in shoulder injuries.

Posture and isokinetic shoulder strength in female water polo players

Background: Being overhead athletes, water polo players can present with muscular imbalances of the shoulder, between the internal rotators (IR) and external rotators (ER), leading to changes in posture and an increased risk of injury. Objectives: To assess posture and isokinetic shoulder strength of female club-level water polo players. Methods: A descriptive study assessing posture and isokinetic strength of the IR and ER shoulder muscles in 15 female club-level South African water polo players (age: 21.3 ± 1.5 years) was conducted. Posture was assessed using a posture grid. Isokinetic shoulder rotator muscle strength was tested over five repetitions concentrically and eccentrically at 60°/sec using a Biodex system 3 isokinetic dynamometer. The bilateral, reciprocal and functional dynamic control ratios (DCR) were calculated. Results: Typical postures noted were a forward head, rounded shoulders, increased thoracic spine kyphosis, elevated non-dominant shoulder and mild scapula winging. The mean concentric reciprocal ratios for the dominant (52.2 ± 7%) and non-dominant (51.9 ± 6.4%) sides indicated ER muscle weakness. DCR values were within normal limits for the group. (D: 0.75 ± 0.2 and ND: 0.75 ± 0.1). Conclusion: There is a trend for these female water polo players to have rounded shoulders and forward head postures, as well as ER muscle strength weakness, the combination of which could predispose the athletes to shoulder injury.

Evaluation of shoulder function after secondary surgery in children with Neonatal Brachial Plexus Palsy.

Shoulder function in children with Neonatal Brachial Plexus Palsy (NBPP) can be impaired. Functional gain is possible by an internal contracture release and muscle tendon transfer (ICL+MTT) for external rotation. This study evaluates the functional results of this intervention. Assessments were done pre-operatively and 3, 6 and 12 months thereafter and included joint-mobility (ROM), muscle strength, arm function (Assisting Hand Assessment (AHA) and Mallet-score), Quality of Life (QoL) (Pediatric Outcome Data Collecting Instrument (PODCI)) and parental satisfaction. Changes were examined using Wilcoxon's Signed-Rank test and Cohen's effect size. Ten children (5 boys) aged 3-10 years who underwent a combined ICL+MTT (mm. Latissimus Dorsi/Teres Major) were included.Active and passive external rotation ROM and muscle strength improved (p < 0.05). Arm function improved according to the Mallet-score (Hand-to-Head, Hand-to-Mouth, External-Rotation) (p < 0.05) and the arm use and pace scales of the AHA (p < 0.05). The PODCI Upper Extremity/Physical Functioning and Global Functioning subscales also showed improvements (p < 0.05). Parents were highly satisfied concerning daily life activities and sports. ICL+MTT leads to improvement of ROM, strength, arm function, QoL and high parental satisfaction in this studies' patients and is therefore a good intervention to consider in children with NBPP with limited shoulder function.

The Effect of Game Participation by a Professional Pitcher on Isokinetic and Isometric Muscle

This study was conducted to identify the isokinetic muscular strength during the season in professional baseball pitchers. By medical and clinical tests of medical specialist (doctor), 21 players were selected for this study. Total results of 21 players were used as data. All variables were measured in pre-season, in-season, and post-season. Isokinetic and isometric muscle strength was measured by CSMi (Humac Co., U.S.A). Repeated measure MANOVA was used to verify differences between the groups. LSD (Least Significant Difference) was carried out when significant difference is appeared among times and independent T-test was used to analyze significant differences between groups. Significant level was p<.05. The results of this study were as follows: In isokinetic muscle strength test, ER/IR ratio of dominant shoulder was significantly lower than in non-dominant. Peak muscle strength (180°/sec) in dominant was significantly lower. In isometric muscle strength test, isometric-25° ER muscle strength in dominant was significantly lower than in non-dominant. In conclusion, Isometric muscle strength of external rotators in dominant was lower and also decreased during the season. Therefore, further researches will be necessary for identifying effects of pitching on muscle strength in baseball players.

Effects of humeral head compression taping on the isokinetic strength of the shoulder external rotator muscle in patients with rotator cuff tendinitis.

[Purpose] The purpose of this study was to examine the effects of humeral head compression taping (HHCT) on the strength of the shoulder external rotator muscle in patients with rotator cuff tendinitis. [Subjects and Methods] Twenty patients with rotator cuff tendinitis were recruited. The shoulder external rotator strength was measured using a Biodex isokinetic dynamometer system. A paired t-test was performed to evaluate within-group differences in the strength of the shoulder external rotator muscle. [Results] Significantly higher shoulder external rotator peak torque and peak torque per body weight were found in the HHCT condition than in the no-taping condition. [Conclusion] HHCT may effectively increase the shoulder external rotator muscle strength in patients with rotator cuff tendinitis.

Lumbopelvic Kinematic Characteristics of Golfers With Limited Hip Rotation

Background: While the biomechanical characteristics of the golf swing are well established, the lumbopelvic kinematic characteristics of professional golfers with limited hip internal rotation warrant further investigation. Purpose: The specific aim was to ascertain mechanical differences in lumbopelvic-hip movement of asymptomatic professional golfers with and without limited hip internal rotation during the golf swing. Study Design: Controlled laboratory study. Methods: Thirty professional male golfers (aged 25-35 years and 0 handicap matched) were classified into either the limited hip internal motion (LHIM) group (range of motion <20°) or the normal hip internal motion (NHIM) group (range of motion ≥30°). All participants underwent clinical tests (muscle strength, muscle length, and range of motion) and a biomechanical assessment using 8 infrared optic cameras in a motion analysis system. Independent t tests were performed to determine potential mean differences in muscle strength, length, and range of motion and lumbopelvic kinematics at P < .05. Results: Kinematic analysis revealed that the LHIM group showed significantly greater lumbar flexion (P < .001), right and left axial rotation (P < .025), and right-side lateral bending (P = .003) than the NHIM group. A greater pelvic posterior tilt was observed in the LHIM group when compared with the NHIM group (P = .021). Clinical tests showed reduced internal rotator muscle strength and shorter muscle length in the iliopsoas (P = .017) and hamstring (P < .001) among those in the LHIM group when compared with the NHIM group. Clinical Relevance: The study data suggest that constraints to hip joint internal rotation, along with muscle strength imbalances between the agonist and antagonist muscles and muscle tightness, are associated with substantially greater lumbopelvic movement during the golf swing.

Factors associated with visually assessed quality of movement during a lateral step-down test among individuals with patellofemoral pain.

Cross-sectional. To determine what physical measures are associated with visually assessed quality of movement among patients with patellofemoral pain (PFP). An altered movement pattern has been implicated as a risk factor for PFP. An understanding of physical measures associated with an altered movement pattern could potentially help guide prevention and management efforts in patients with PFP. Seventy-nine (40 women) Israel Defense Forces soldiers referred to physical therapy with a diagnosis of PFP were included. Movement pattern was assessed visually during a lateral step-down test and rated as "good" or "moderate," based on previously established criteria. Weight-bearing and non-weight-bearing ankle dorsiflexion (DF) range of motion (ROM); hip internal and external rotation ROM; and hip abduction, hip external rotation, and knee extension strength were also assessed. Differences in physical measures between those with good versus moderate quality of movement were assessed. Weight-bearing DF ROM was more limited among participants with a moderate quality of movement compared to those with a good quality of movement (P<.01). Among men, non-weight-bearing DF ROM was more limited in those with a moderate quality of movement as well (P<.01). In addition, quality of movement was associated with weight-bearing DF ROM for both women (r = -0.39, P = .01) and men (r = -0.46, P<.01), and with non-weight-bearing DF ROM for men (r = -0.66, P<.01). When the subgroup of participants who exhibited more than 25° of non-weight-bearing DF ROM was assessed, those with a good quality of movement displayed greater hip external rotator and knee extensor muscle strength compared with those with a moderate quality of movement (P<.01). Ankle DF ROM should be assessed when patients with PFP demonstrate a lower quality of movement during a lateral step-down test. Lower hip muscle strength may be associated with lower quality of movement among patients with relatively greater ankle DF ROM.

The effect of ankle muscle strength and flexibility on dolphin kick performance in competitive swimmers

The velocity of a swimmer is determined by biomechanical and bioenergetics factors. However, little is known about the effect of ankle flexibility on dolphin kick performance. Next to this, scientific evidence is lacking concerning the influence of ankle muscle strength. Therefore, the aim of this study was to investigate the effect of ankle flexibility and muscle strength on dolphin kick performance in competitive swimmers.Ankle range of motion (ROM) and ankle muscle strength were measured in 26 healthy competitive swimmers. The effect of both was assessed on the swimmer’s velocity and lower extremity joint angles during three maximal dolphin kick trials. Additionally, the effect of a flexibility restriction by a tape on the dolphin kick performance was assessed.Correlations were calculated between the flexibility, muscle strength and dolphin kick performance and differences were investigated between the unrestricted and restricted condition. Muscle strength of dorsal flexors and internal rotators were positively significantly correlated with the velocity. Active and passive plantar flexion ROM and internal rotation ROM were not significantly correlated. A plantar flexion–internal rotation restriction during the dolphin kick showed a significant decrease in velocity. This restriction was associated with a changed movement pattern in the knee towards more flexion.The results suggest that dolphin kick velocity might be enhanced by ankle muscle strength exercises and that subjects with a restricted ankle flexibility might profit from a flexibility program.

Hip Rotator Strength in Healthy Young Adults Measured in Hip Flexion and Extension by Using a Hand-held Dynamometer

To investigate the effect of hip joint position on hip rotator muscle strength of healthy young adults by using a hand-held dynamometer. A cross-sectional cohort study. A university medical center. Thirty-four healthy (19 women, 15 men; mean [standard deviation] age, 25± 2.3 years) participated in this study. A hand-held dynamometer was used to measure the strength of hip internal rotators and external rotators in 2 positions: hip flexion in sitting and hip extension in supine. The hip was tested in a neutral position with respect to rotation, abduction, and adduction. Isometric force in pounds was measured as the subject pushed against the device. For each subject, hip rotator muscle strength measurements were taken during a single session. Hypotheses were developed before data collection. Hip internal rotators were significantly stronger in hip flexion compared with hip extension (P< .01). There was no significant difference found in the hip external rotators between the 2 positions. Hip internal rotators and external rotators behave differently when comparing strength measurements between the positions of hip flexion and hip extension. A hand-held dynamometer provided an objective measurement of strength that was clinically feasible to use. Both muscle length and moment arms influence forceproduction of the hip rotators as the hip position changes. Understanding these relationships may help clinicians interpret strength findings and direct intervention toward strengthening the appropriate muscles by using the most advantageous position.