Utilizing Hip Abduction Strength to Body-Weight Ratios in Return to Sport Decision-Making After ACL Reconstruction

BackgroundDespite the association between hip abduction weakness and non-contact anterior cruciate ligament (ACL) injury, hip abduction strength is rarely considered in return to sport decision-making following ACL reconstruction (ACLR).Hypothesis/PurposeThe purpose of this study was to compare self-reported function, objective functional test performance, and re-injury rates in patients with high (≥33%) versus low (<33% ) isometric hip abduction strength to body weight (BW) ratios when returning to activity following ACLR.Study DesignCohort studyMethodsData were gathered from a single-surgeon database and included baseline demographics. Clinical outcomes were assessed at the time of release to activity and included self-reported outcomes and a functional testing battery. Isometric hip abduction strength was obtained using a handheld dynamometer. Groups were dichotomized into those with low vs high strength to BW ratios. Two-year follow-up was performed using the single assessment numeric evaluation (SANE). Data were analyzed using univariate general linear models with an alpha level of .05.ResultsOf the 528 enrolled patients, 364 (68.9%) demonstrated a low strength to BW ratio. Baseline comparisons revealed more females and higher BMI (P <.05) in the <33% group. At release to activity, the <33% BW group demonstrated lower International Knee Documentation Committee survey scores (88.2 ± 13.6 vs 93.5 ± 10.3, P<.01), ACL-Return to Sport After Injury (76.2 ± 15.4 vs 88.5 ± 16.9, P<.01) scores, and isokinetic hamstring peak torque (P=.04). At 2-years, the <33% group reported lower SANE scores (83.3 ± 21.1 vs 92.83 ± 11.4, P=.05) with no significant differences in re-injuries.ConclusionPatients with low hip abduction strength to BW ratios demonstrated lower subjective function, psychological readiness, and isokinetic hamstring peak torque when completing functional testing following ACLR. Subjective deficits remained at 2-years.Level of EvidenceLevel 3Key TermsACL injury, hip abduction strength, return to sport, strength ratioClinical RelevanceAssessing isometric hip abduction strength to body weight ratio may be beneficial in determining readiness to return to sport following ACL reconstruction.What is Known About the SubjectThree prospective studies have provided conflicting evidence regarding the relationship between hip abduction strength and ACL injury. A clinical cut-point of hip abduction strength:BW ratio <35.4% has been suggested to identify athletes at risk of sustaining a non-contact ACL injury. To our knowledge no studies have examined isometric hip abduction strength:BW ratios in athletes attempting to return to sport following ACLR.What This Study Adds to Existing KnowledgeThis study examines the potential for hip abduction strength:BW ratio to be included as an additional metric in return to sport testing batteries.     

ASSOCIATION OF ISOMETRIC STRENGTH OF HIP AND KNEE MUSCLES WITH INJURY RISK IN HIGH SCHOOL CROSS COUNTRY RUNNERS

Background

High school cross country runners have a high incidence of overuse injuries, particularly to the knee and shin. As lower extremity strength is modifiable, identification of strength attributes that contribute to anterior knee pain (AKP) and shin injuries may influence prevention and management of these injuries.

Purpose

To determine if a relationship existed between isometric hip abductor, knee extensor and flexor strength and the incidence of AKP and shin injury in high school cross country runners.

Materials/Methods

Sixty‐eight high school cross country runners (47 girls, 21 boys) participated in the study. Isometric strength tests of hip abductors, knee extensors and flexors were performed with a handheld dynamometer. Runners were prospectively followed during the 2014 interscholastic cross country season for occurrences of AKP and shin injury. Bivariate logistic regression was used to examine risk relationships between strength values and occurrence of AKP and shin injury.

Results

During the season, three (4.4%) runners experienced AKP and 13 (19.1%) runners incurred a shin injury. Runners in the tertiles indicating weakest hip abductor (chi‐square = 6.140; p=0.046), knee extensor (chi‐square = 6.562; p=0.038), and knee flexor (chi‐square = 6.140; p=0.046) muscle strength had a significantly higher incidence of AKP. Hip and knee muscle strength was not significantly associated with shin injury.

Conclusions

High school cross country runners with weaker hip abductor, knee extensor and flexor muscle strength had a higher incidence of AKP. Increasing hip and knee muscle strength may reduce the likelihood of AKP in high school cross country runners.

Level of Evidence

2b     

RELIABILITY,COMPARABILITY, AND VALIDITY OF FOOT INVERSION AND EVERSION STRENGTH MEASUREMENTS USING A HAND-HELD DYNAMOMETER

Background

There are conflicting results with respect to the validity and reliability of lower extremity strength measurements using a hand-held dynamometer (HHD) in the healthy population. Previous studies exploring foot inversion and eversion strength using a HHD were carried out with predominantly clinically affected participants in different positions. The question arises whether HHD measurements of isometric foot inversion and eversion strength performed with participants in different positions are valid, reliable and comparable and can be used alternatively.

Purpose

The aims of this study were to investigate: a) the intra- and inter-tester reliability of measurements of foot inversion and eversion strength in different participant positions using a belt-stabilized HHD; b) the comparability of results obtained in different positions; and c) the concurrent validity of the aforementioned measurements using an isokinetic dynamometer.

Methods

Thirty adults (12 females and 18 males; mean age 22.5 ± 3.9 years) volunteered to participate in this study. Maximal isometric foot inversion and eversion torques (Nm) were measured with participants lying supine, sitting with knees extended and lying on their side using a belt-stabilized HHD. Measurements were performed independently by two physiotherapists over two days and were repeated using an isokinetic dynamometer. Validity and intra- and inter-tester reliability were determined using the intra-class correlation coefficient (ICC). A two-way ANOVA (p < 0.05) and post-hoc tests with Bonferroni correction were used to compare data from different positions. Bland-Altman plots were used to demonstrate the range of error and difference between HHD and isokinetic measurements.

Results

Intra-tester reliability for inversion and eversion torques was fair to excellent in all positions (ICC = 0.598–0.828). Excellent inter-tester reliability was found for eversion torques in all positions (ICC = 0.773–0.860). For inversion torques, inter-tester reliability was fair to excellent (ICC = 0.519–0.879). ICC values of 0.205 to 0.562 indicated a low to fair concurrent validity. A significant difference was observed between the torques of the supine and side-lying positions as well as sitting and side-lying positions (p < 0.05). Bland-Altman plots showed that the mean of the differences for inversion and eversion torques deviates considerably from zero, indicating that measurements with the HHD in the three positions produce lower values compared to using the isokinetic dynamometer.

Conclusions

Inversion and eversion strength measurements with subjects in different positions using HHD seem to be reliable, but consistently underestimated torque output when compared with measurements using isokinetic dynamometry. While the HHD outcomes measured in supine and sitting positions seem to be comparable, those measured in supine/sitting and side-lying positions differed.

Level of Evidence

Diagnostic study, Level 3     

CHANGES IN HIP RANGE OF MOTION AND STRENGTH IN COLLEGIATE BASEBALL PITCHERS OVER THE COURSE OF A COMPETITIVE SEASON: A PILOT STUDY

Background

Adaptations in hip range of motion (ROM) and strength have been shown to influence performance and injury risk in overhead athletes. These adaptations in hip ROM and strength have not been examined longitudinally, and little is known regarding whether these changes are a result of pitching workload.

Hypothesis/Purpose

The authors hypothesized that hip rotation ROM and strength would change over the course of a season, and would be associated with pitching workload (number of pitches over the course of a season). The purpose of this exploratory, pilot study was twofold: 1) to examine changes in hip external rotation (ER) ROM, internal rotation (IR) ROM, isometric hip abduction and hip extension strength in pitchers occurring over the course of a competitive season, and 2) to determine the association between changes in hip ROM, strength, and pitching volume.

Study Design

Cohort (longitudinal) study

Methods

Bilateral hip rotation ROM and hip isometric strength was tested pre‐ and post‐season in fourteen collegiate baseball pitchers. Pearson correlations were calculated to determine the association between changes in hip ROM, strength, and pitching workload.

Results

Trail and lead hip ER, trail and lead hip total rotational ROM, and trail and lead hip abduction strength in all pitchers decreased from preseason to postseason (p < 0.01). However, these changes were not significantly associated with pitching workload (p > 0.05).

Conclusion

This study demonstrates that changes occur in hip ROM and strength in collegiate pitchers over the course of a season. These changes were not associated with pitching workload

Level of Evidence

3     

NORMATIVE VALUES OF ECCENTRIC HIP ABDUCTION STRENGTH IN NOVICE RUNNERS: AN EQUATION ADJUSTING FOR AGE AND GENDER

Purpose:

Low eccentric strength of the hip abductors, might increase the risk of patellofemoral pain syndrome and iliotibial band syndrome in runners. No normative values for maximal eccentric hip abduction strength have been established. Therefore the purpose of this study was to establish normative values of maximal eccentric hip abduction strength in novice runners.

Methods:

Novice healthy runners (n = 831) were recruited through advertisements at a hospital and a university. Maximal eccentric hip abduction strength was measured with a hand–held dynamometer. The demographic variables associated with maximal eccentric hip abduction strength from a univariate analysis were included in a multivariate linear regression model. Based on the results from the regression model, a regression equation for normative hip abduction strength is presented.

Results:

A significant difference in maximal eccentric hip abduction strength was found between males and females: 1.62 ± 0.38 Nm/kg (SD) for males versus 1.41 ± 0.33 Nm/kg (SD) for females (p < 0.001). Age was associated with maximal eccentric hip abduction strength: per one year increase in age a ‐0.0045 ± 0.0013 Nm/kg (SD) decrease in strength was found, p < 0.001. Normative values were identified using a regression equation adjusting for age and gender. Based on this, the equation to calculate normative values for relative eccentric hip abduction strength became: (1.600 + (age * ‐0.005) + (gender (1 = male / 0 = female) * 0.215) ± 1 or 2 * 0.354) Nm/kg.

Conclusion:

Normative values for maximal eccentric hip abduction strength in novice runners can be calculated by taking into account the differences in strength across genders and the decline in strength that occurs with increasing age. Age and gender were associated with maximal eccentric hip abduction strength in novice runners, and these variables should be taken into account when evaluating eccentric hip abduction strength in this group of athletes.

Level of Evidence:

2A     

EFFECT OF RESTRICTED HIP FLEXOR MUSCLE LENGTH ON HIP EXTENSOR MUSCLE ACTIVITY AND LOWER EXTREMITY BIOMECHANICS IN COLLEGE‐AGED FEMALE SOCCER PLAYERS

Background

Hip flexor tightness is theorized to alter antagonist muscle function through reciprocal inhibition and synergistic dominance mechanisms. Synergistic dominance may result in altered movement patterns and increased risk of lower extremity injury.

Hypothesis/Purpose

To compare hip extensor muscle activation, internal hip and knee extension moments during double‐leg squatting, and gluteus maximus strength in those with and without clinically restricted hip flexor muscle length.

Design

Causal‐comparative cross‐sectional laboratory study.

Method

Using a modified Thomas Test, female soccer athletes were assigned to a restricted (>0 ° of sagittal plane hip motion above the horizontal; n=20, age=19.9 ± 1 years, ht=167.1 ± 6.4 cm, mass=64.7 ± 8.2kg) or normal (>15 ° of sagittal plane hip motion below horizontal; n=20, age=19.4 ± 1 years, ht=167.2 ± 5.5 cm, mass=61.2 ± 8.6 kg) hip flexor muscle length group. Surface electromyographic (sEMG) activity of the gluteus maximus and biceps femoris, and net internal hip and knee extension moments were measured between groups during a double‐leg squat. Isometric gluteus maximus strength was assessed using handheld dynamometry.

Results

Individuals with restricted hip flexor muscle length demonstrated less gluteus maximus activation (p=0.008) and a lower gluteus maximus : biceps femoris co‐activation ratio (p=0.004). There were no significant differences (p>0.05) in hip or knee extension moments, isometric gluteus maximus strength, or biceps femoris activation between groups.

Conclusions

Female soccer athletes with hip flexor muscle tightness exhibit less gluteus maximus activation and lower gluteus maximus : biceps femoris co‐activation while producing similar net hip and knee extension moments. Thus, individuals with hip flexor muscle tightness appear to utilize different neuromuscular strategies to control lower extremity motion.

Level of Evidence

3     

TEST-RETEST RELIABILITY OF TWO CLINICAL TESTS FOR THE ASSESSMENT OF HIP ABDUCTOR ENDURANCE IN HEALTHY FEMALES

Background

Substantial deficits in performance of hip abductor in patients with common lower extremity injuries are reported in literature. Therefore, assessing hip abductor endurance might be of major importance for clinicians and researchers.

Purposes

The purpose of this study was to examine the test-retest reliability of two hip abductor endurance tests in healthy females. Learning effect, systematic difference in the rate of perceived exertion and relationship between endurance performance and some clinical characteristics of participants were also investigated.

Design

Observational study, with a test-retest design.

Methods

Thirty-six healthy females, aged 18-30 years, were recruited. In two identical assessment sessions, the participants performed an isometric hip abductor strength test and two different hip abductor endurance tests

Results

Isometric and dynamic endurance tests demonstrated good test-retest reliability (intraclass correlation coefficients (ICC) = 0.73 and 0.78, respectively). The standard errors of measurement (SEM) and the minimal detectable changes (MDC) were, respectively, 19.8 and 54.9 seconds for isometric endurance test and 21.2 and 58.7 repetitions for dynamic endurance test. Moderate correlation between both endurance tests (r = 0.60, p = 0.0001) and weak correlation between dynamic endurance test and strength (r = 0.44, p = 0.008) were found.

Conclusions

The results of the present study demonstrate good test-retest reliability of two non-instrumented clinical tests of hip abductor endurance in healthy females.

Level of evidence

2b     

THE IMPACT OF SAGITTAL PLANE HIP POSITION ON ISOMETRIC FORCE OF HIP EXTERNAL ROTATOR AND INTERNAL ROTATOR MUSCLES IN HEALTHY YOUNG ADULTS

Purpose/Background:

Hip external rotator (ER) and internal rotator (IR) muscle weakness is theorized to be associated with lower extremity injury in athletes including knee ligament tears and patellofemoral pain. Previous studies investigating hip musculature strength have utilized various sagittal plane hip positions for testing. The relationship between results at these different positions is unknown.

Methods:

Eighty healthy, pain‐free young adults participated in the study: 40 female, mean age 22.90 (± 2.32) years, and 40 male, mean age 23.50 (± 2.15) years. Peak isometric torque of bilateral hip ER and IR were tested at 90° and 0° of hip flexion with an instrumented dynamometer. Peak muscle forces were calculated. Peak forces were normalized by body mass. Mean normalized force was calculated for dominant and non‐dominant limbs for ER and IR in both positions. Male and female data were analyzed separately with paired t‐tests (2‐tailed). Reference values for average muscle force and torque were calculated for dominant and non‐dominant limbs for both hip positions.

Results:

Hip IR normalized peak force was greater at 90° compared to 0° flexion position bilaterally in both genders (p < .01). Hip ER normalized peak force was greater at 90° compared to 0° flexion in dominant limbs of both genders and in non‐dominant limbs of males (p < .01). Non‐dominant hip ER normalized force in females was greater at 90° versus 0° flexion; however, it was not significant (p = .092). Post hoc analysis of normalized average force (average over 5‐second contraction) yielded similar results.

Conclusion:

Clinicians and researchers should use consistent positioning for testing of hip ER and IR strength. This will improve certainty of determining if a patient’s strength has changed or if differences between groups are present. Reference values reported will be useful in order to determine if weakness is present and to set goals, particularly in cases of bilateral involvement.

Level of Evidence:

2b     

THE RELATIONSHIP BETWEEN PASSIVE GLENOHUMERAL TOTAL ROTATION AND THE STRENGTH OF THE INTERNAL AND EXTERNAL ROTATOR MUSCLES,A PRELIMINARY STUDY

Background

There is little research on how the amount of shoulder joint range of motion, specifically glenohumeral rotation, may be related to the muscle strength of the rotator cuff muscles. A long held belief is that a joint with excessive range of motion needs sufficient muscular strength for stability. However, no studies have examined this concept.

Purpose

The purpose of this study was to see if total arc of glenohumeral joint rotation (External rotation [ER]+Internal rotation [IR]) could predict peak isometric muscle strength of the IR or ER muscles of the shoulder.

Study Design

Cross‐sectional study design

Methods

Fifty‐three participants (41 females, 12 males) participated in the study. Passive glenohumeral joint internal rotation and external rotation motion was measured for each participant with a standard goniometer. Isometric muscle force of the ER and IR muscles were tested using a handheld dynamometer in three positions: end range ER, neutral 0°, and end range IR. Data were analyzed using a non‐parametric tree based regression method (CART) and then cross‐validated.

Results

The results showed that those with an increased total arc of motion of glenohumeral rotation (greater than 165.0°) had less muscle isometric muscle strength in all tests positions than those with less glenohumeral rotation.

Conclusion

Decreased force of the ER and IR muscles of the shoulder was noted in those with increased total arc glenohumeral rotation ( > 165.0°), specifically those with increased glenohumeral internal rotation ( > 80.0°) when compared to those with glenohumeral rotation ( < 165.0°) and glenohumeral internal rotation ( < 80.0°). Future studies should include more males and attempt to develop strategies to assist those with larger excursions of shoulder rotation who may be at risk of developing shoulder problems.

Level of Evidence

Level 2     

RELATIONSHIP BETWEEN HIP STRENGTH AND TRUNK,HIP, AND KNEE KINEMATICS DURING A JUMP‐LANDING TASK IN INDIVIDUALS WITH PATELLOFEMORAL PAIN

Background/Purpose:

Decreased strength of the hip musculature and altered mechanics of the lower extremity have been identified in individuals with patellofemoral pain (PFP). The aim of this study was to determine if a relationship exists between hip muscle strength and transverse and frontal plane motion at the hip and knee, and ipsilateral trunk flexion during a jump‐landing task in individuals with PFP.

Methods:

Fifteen individuals (10 females, 5 males) with PFP participated in this investigation. A three‐dimensional motion analysis system was utilized to assess trunk, hip, and knee kinematics during a jump‐landing task. An isokinetic dynamometer was utilized to assess concentric and eccentric strength of the hip musculature. Simple correlation analyses were performed to determine the relationships between hip muscle strength and peak frontal and transverse plane hip and knee kinematics and ipsilateral trunk flexion.

Results:

Decreased eccentric strength of the hip external rotators and abductors was significantly correlated to increased frontal plane motion at the hip and trunk, respectively (P<0.05).

Conclusions:

Based on these findings, eccentric strengthening exercises for the hip musculature may be an important component for clinicians to include when rehabilitating individuals with PFP who display increased frontal plane motion at the hip and trunk.

Level of Evidence:

2b     

Reliability of a new instrument for measuring plantarflexor muscle strength

Örtqvist M, Gutierrez-Farewik EM, Farewik M, Jansson A, Bartonek Å, Broström E. Reliability of a new instrument for measuring plantarflexor muscle strength.

Objectives

To test the reliability of a new muscle strength testing instrument (the Strength Measuring Chair [SMC]) designed to quantify isometric strength in the lower extremities, and to determine the agreement between the SMC and an isokinetic dynamometer (Biodex).

Design

Isometric strength tests were performed in plantarflexors with 2 different knee positions (60°, 30°). Measurements were taken at 3 different sessions.

Setting

Strength testing laboratory.

Participants

Twenty-three able-bodied adults and 15 able-bodied children.

Interventions

Not applicable.

Main Outcome Measure

Isometric plantarflexor strength.

Results

The reliability of isometric strength measurements of plantarflexors taken in the SMC was excellent for both the adult and children groups (intraclass correlation coefficient range, .84−.87). A Bland-Altman 95% limit of agreement test showed no systematic variation in 3 of the 4 SMC test observations; systematic variation was only observed in the adult group at a knee position of 30°. There was no systematic difference in the adult group between the SMC and the isokinetic dynamometer, but there was a systematic variation in the children’s group.

Conclusions

The SMC reliably measured isometric plantarflexor strength in the tested populations.     

Single Leg Bridge Test is Not a Valid Clinical Tool to Assess Maximum Hamstring Strength

BackgroundThe single leg bridge test (SLBT) has been introduced in the sports context as a way of estimating hamstring muscle capacity for prevention and rehabilitation of hamstring strain injuries.PurposeThe primary aim was to examine the association between SLBT scores with concentric and eccentric knee flexor peak torques. Secondarily, this study aimed examine the association of between-limb asymmetries provided by SLBT and isokinetic tests.Study designCross-sectional study.MethodsOne hundred male soccer players (20±3 years) performed the SLBT and the knee flexion-extension isokinetic dynamometry evaluation (60°/s) billaterally during a single visit. SLBT score (i.e., number of repetitions until failure) and concentric and eccentric knee flexor peak torques (normalized per body mass) were considered for analysis. For both SLBT and isokinetic dynamometry, between-limb asymmetry was calculated as the percentage difference between the left limb and the right limb. Associations were assessed through Pearson’s correlation coefficient.ResultsThe mean SLBT score was 33.6±9.6 repetitions, concentric peak torque was 2.00±0.22 Nm/kg, and eccentric peak torque was 2.79±0.44 Nm/kg. Between-limb asymmetry was 0.4±9.6%, 1.08±8.5%, and 1.64±14.61% in SLBT, concentric, and eccentric tests, respectively. There was a poor association of SLBT score with concentric (p<0.001, r=0.275) and eccentric (p=0.002, r=0.215) peak torques. The SLBT between-limb asymmetry was poorly associated with asymmetry found in concentric peak torque asymmetry (p=0.033, r=0.213) and was not associated with eccentric peak torque asymmetry (p=0.539, r=0.062).ConclusionThe SLBT should not be used as a clinical tool to assess the maximum strength of hamstring muscles.Level of EvidenceLevel 3     

STRENGTH & FUNCTIONAL ASSESSMENT OF HEALTHY HIGH SCHOOL FOOTBALL PLAYERS: ANALYSIS OF SKILLED AND NON‐SKILLED POSITIONS

Background/Purpose

Identifying an athlete''s functional capacity is an important consideration in determining when to allow an athlete to return to competition following injury. Establishing normative data for lower extremity functional assessment is valuable for comparison when making decisions regarding the high school athlete returning to play after injury. Therefore, the purpose of this study was to compare functional performance and strength between American high school football players of both skilled and non‐skilled positions.

Methods

Forty‐nine high school football players (30 skilled; 19 non‐skilled) completed a single‐session of testing consisting of a Figure of 8 test (F‐8), single‐leg vertical jump (SLVJ), single‐leg broad jump (SLBJ), and isokinetic knee strength assessment. Pearson correlation coefficients were used to determine the relationships between the results of functional testing and isokinetic strength measures. Paired t‐tests were used to determine the differences in functional performance and isokinetic muscle strength between skilled and non‐skilled athletes.

Results

Knee extension peak torque/body weight (BW) was moderately correlated (p < .01) with SLBJ (r = .54‐.61), SLVJ (r = .39‐.48), and F‐8 run times (r = ‐.50) for all athletes. Similar relationships were observed between knee flexion peak torque/BW and SLBJ (r = .48‐.49), SLVJ (r = .28‐.46), and the F‐8 run times (r = .41‐.52) for all subjects. No differences were observed between groups when examining raw peak torque values for knee flexion and extension (p > .05), however, skilled players did demonstrate greater peak torque/BW ratios (p < .05) for both knee extension and knee flexion at 60 and 240 degrees/sec. Skilled players also displayed faster F‐8 times (9.4 sec ± .3; p < .01) and greater SLBJ (p < .05) on both the dominant (81.0 in ± 9.3) and non‐dominant (83.0 in ± 7.6) limbs (p < .01) when compared to non‐skilled players.

Conclusions

Overall, skilled football players displayed greater peak torque/BW ratios and functional performance when compared to non‐skilled players. Furthermore, isokinetic peak torque/BW appears to be related to functional performance. This relationship is affected by position, with skilled players showing a stronger association. Limb dominance did not influence these functional and strength metrics. It is recommended that clinicians and coaches consider the positional differences in strength and functional performance when managing patients and athletes.

Level of Evidence

4 – Cross‐sectional Case Series     

PERCEIVED LOADING AND MUSCLE ACTIVITY DURING HIP STRENGTHENING EXERCISES: COMPARISON OF ELASTIC RESISTANCE AND MACHINE EXERCISES

Objective:

Decreased hip muscle strength is frequently reported in patients with hip injury or pathology. Furthermore, soccer players suffering from groin injury show decreased strength of hip muscles. Estimating 10‐repetition maximum can be time‐consuming and difficult, thus, using the Borg category rating 10 scale (Borg CR10 scale) can be a useful tool for estimating the intensity of exercise. The aims of this study were 1) to investigate the feasibility of the use of the Borg CR10 scale for rating strength training intensity of the hip abductor and hip adductor muscles, and 2) to compare hip muscle activity during hip abduction and hip adduction exercises using elastic resistance and isotonic machines, using electromyography (EMG).

Methods:

EMG activity was recorded from 11 muscles at the hip, thigh and trunk during hip adduction and hip abduction exercises in 16 untrained women, using elastic resistance and isotonic exercise machines. These recordings were normalized to maximal voluntary contraction (MVC) EMG (nEMG). The exercises were performed at four levels of perceived loading reported using the Borg CR10: light (Borg ≤2), moderate (Borg >2–<5), heavy (Borg ≥5–<7) and near maximum (Borg ≥7).

Results:

Moderate to strong associations were observed between perceived loading and nEMG obtained during the adduction exercise with elastic resistance (r=0.8±0.3) as well as in machine (r=0.69±0.55) and the abduction exercise with elastic resistance (r=0.66±0.29) as well as in machine (r =0.62±0.54). The abduction exercise performed with elastic resistance displayed significantly higher gluteus medius nEMG recruitment than the in machine exercise.

Conclusions:

The results of this study show that the Borg CR10 scale can be a useful tool for estimating intensity levels during resistance training of the hip adductor and hip abductor muscles. Although elastic resistance and exercise machine seem equally effective for recruiting muscle activity of the hip adductors, the elastic resistance condition was able to demonstrate greater muscle recruitment than the exercise machine during hip abduction.     

Associations between functional capacity,isokinetic leg strength,sleep quality and cognitive function in multiple sclerosis patients: a cross-sectional study

ABSTRACT

Objectives: Recent evidence suggests an association between functional capacity and cognitive function, at least in older adults. The aim of this cross-sectional study was to examine the association between cognitive function, functional capacity, isokinetic leg strength, health-related quality of life (HRQOL), sleep quality, body fat, handgrip strength, and fatigue among a sample of MS patients.

Methods: Fifty-one relapsing-remitting MS patients (age: 38.4 ± 7.1 yrs; 30 females) were recruited and agreed to participate in this study. Cognitive function was assessed by the Paced Auditory Serial Addition Test (PASAT). Functional capacity was examined using various functional tests commonly used in MS patients. Maximal voluntary unilateral leg strength was assessed using isokinetic dynamometer. Isometric handgrip strength was assessed by a dynamometer. Total body and visceral fat levels were assessed via bioelectrical impedance analyzers. Finally, the patients’ HRQOL, sleep quality, and fatigue levels were evaluated using specific questionnaires.

Results: A significant association was found between the PASAT score and the performance score in various functional capacity tests (p < 0.050). On the other hand, a weak but statistically significant association was found between the PASAT score and isokinetic strength of knee extensors (r = 0.319, p = 0.022) and knee flexors (r = 0.354 p = 0.011). Poor sleep quality was associated with lower performance in all the functional capacity tests examined (p < 0.05) whilst was negatively associated with the PASAT score (r = ?0.334, p = 0.017). The multivariate regression analysis revealed that the performance on the TUG test was a significant predictor of cognitive function.

Conclusion: Based on the results of this study, functional capacity was found to be associated with both impaired cognitive performance and low HRQOL in MS patients. In addition, an association between sleep quality and cognitive performance was revealed, confirming existing literature. Functional capacity as assessed by the TUG test emerged as the best predictor of cognitive function.     

EFFECTS OF BLOOD FLOW RESTRICTION TRAINING ON HANDGRIP STRENGTH AND MUSCULAR VOLUME OF YOUNG WOMEN

Background:High-intensity training methods are generally recommended to increase muscle mass and strength, with training loads of 60-70% 1RM for novice and 80-100% 1RM for advanced individuals. Blood flow restriction training, despite using lower intensities (30-50% 1RM), can provide similar improvements in muscle mass and strength. However, studies commonly investigate the effects of blood flow restriction training in large muscular groups, whereas there are few studies that investigated those effects in smaller muscle groups, such as the muscles involved in grasping (e.g, wrist flexors; finger flexors). Clinically, smaller muscular groups should also be considered in intervention programs, given that repetitive stress, such as repeated strain injuries, affects upper limbs and may lead to chronic pain and incapacity for work. The purpose of the present study was to examine the effects of blood flow restriction training in strength and anthropometric indicators of muscular volume in young women.Hypothesis:The effect of blood flow restriction training in handgrip strength (HGS) and muscular volume of young women can be similar to traditional training, even with lower loads.Methods:Twenty-eight university students, 18 to 25 years of age, were randomly assigned into two groups, blood flow restriction training (BFR, n = 14) and traditional training (TRAD, n = 14). The anthropometric measures and maximum handgrip strength (MHGS) test were performed before and after the intervention. The participants did three weekly sessions of dynamic concentric contraction exercises on a dynamometer for four weeks (12 sessions). Each session had a time length of five minutes and the intensity was established from a percentage of MHGS at 30-35% in the first week, 40-45% in the second and 50-55% in third/fourth weeks. Three sets of 15-25 handgrip repetitions were performed until a failure with a 30 seconds rest for BFR training and three sets of 8-12 repetitions with one-minute rest for TRAD training.Results:A significant increase was found in the arm muscle circumference (20.6 ± 2.2 vs 21.6 ± 1.7cm) and right MHGS (32.7 ± 4.5 vs 34.3 ± 4.1 kgf) and left MHGS (28.0 ± 5.5 vs 30.9 ± 4.1 kgf) for the BFR training, and the left MHGS (27.6 ± 5.0 vs 31.0 ± 6.1 kgf) for the TRAD training.ConclusionDynamometer training with blood flow restriction, performed with low to moderate loads, was more effective than the traditional training in increasing HGS and muscle volume in young women.Level of evidence:2b     

EFFECTS OF KINESIO TAPING ON HIP ABDUCTOR MUSCLE STRENGTH AND ELECTROMYOGRAPHY ACTIVITY IN ATHLETES WITH CHRONIC ANKLE INSTABILITY: A RANDOMIZED CONTROLLED TRIAL

ObjectiveAthletes with chronic ankle instability tend to develop hip abductor muscle weakness. Kinesio taping may help this muscle perform its functions, thus preventing injury. The aim of this study was to assess the effects of Kinesio taping on hip abductor muscle strength and electromyography (EMG) activity.SubjectsA total of 34 athletes, mean age 22.08 years (standard deviation 2.71 years) participated in the study.MethodsA pre-test–post-test experimental design was used. For the experimental group, Kinesio tape, and for the control group, Micropore tape, was applied over the gluteus medius muscle. Gluteus medius muscle strength and EMG activity were noted in supine and during the single-leg squat test (SLST), respectively, before and after the intervention. Strength was measured through maximum voluntary isometric contraction (MVIC) force with a handheld dynamometer, and muscle activation measured through EMG.ResultsIn the experimental group, there was a significant increase in gluteus medius strength, by 10.27% (p = 0.00), and a significant decrease in EMG activity (p = 0.00), by 8.38%. In the control group, there was a significant increase in gluteus medius strength, by 2.89% (p = 0.01) and a not statistically significant decrease in EMG activity, by 0.80% (p = 0.15).ConclusionKinesio taping is effective in increasing hip abductor muscle strength in athletes with chronic ankle instability.LAY ABSTRACTAthletes with chronic ankle instability tend to develop hip abductor weakness, which further predisposes them to injuries in the lower limb and hinders their athletic performance. Kinesio taping may help this muscle perform its functions. The aim of this study was to determine the effects of Kinesio taping, applied over the hip abductors, on muscle strength and activation. A total of 34 athletes with chronic ankle instability were recruited to the study. Kinesio taping was found to be effective in increasing the strength of the hip abductor muscle and reducing its activation. Kinesio taping can be used by athletes with chronic ankle instability to prevent injury to the lower limb, for rehabilitation, and to enhance their athletic performance.Key words: ankle injury, hip abductors, Kinesio taping, muscle strength, electromyography

One of the most common injuries, occurring not only in sports, but also in everyday activities, is ankle sprain (1, 2). Incomplete recovery of ankle sprain is very common, and the majority of individuals after initial ankle sprains experience residual symptoms, such as repeated sprains, pain, and a sensation of “giving way” (3). This condition is called chronic ankle instability (CAI) (4). CAI is highly prevalent in high-school/ collegiate athletes, and occurs in up to 70% of athletes with initial ankle sprains (5–8). CAI is associated with reduced health-related quality of life, reduced physical activity levels, and suboptimal functional levels (9). In individuals with chronic ankle sprains the ipsilateral hip abductor muscles are weak in comparison with the uninjured side (10, 11). Beckman & Buchanan observed a significant delay in muscle activation of the gluteus medius (GM) in individuals with CAI (12).Weak hip musculature and comparatively stronger hip adductors further predispose the ankle joint to sprains, because hip joint stability and hip musculature strength are crucial for foot positioning during the heel strike phase of the gait cycle and overall proper gait mechanics (11, 13). This becomes a vicious cycle, in which CAI causes hip abductor muscle weakness and weak hip abductor muscles cause ankle injuries. Therefore, to prevent future problems in the foot and ankle complex in such individuals, this vicious cycle should be broken, either through strengthening the weak hip abductors or by reinforcing the actions of these muscles. Application of Kinesio tape (KT) (3B Scientific®tape, Burnham-on-Sea, UK) is also a method for improving muscle functions, and thus can be used to reinforce the actions of hip abductors. KT is a thin elastic tape that has stretchability up to 120–140% of its original length, and hence provides less mechanical constraint during movement. KT is considered to prevent injuries during sports and to reduce muscle spasms, swelling, and pain (14).A recent study has examined the effects of KT on hip abductor muscle strength in athletes with and without functional ankle instability (FAI) and reported an increase in muscle strength after application of KT (15). However, in that study, KT was applied over both the peroneus longus and the GM, not over the GM only. To the best of our knowledge, no study has examined the effects of KT on muscle strength and electromyography (EMG) activity of GM when KT is applied over the GM only.The aim of this study was to examine the effects of KT on muscle strength and EMG activity of GM in athletes with CAI. If KT is found to have significant effects on muscle strength and EMG activity then it can be used to improve lower limb kinematics, improve athletic performance, prevent and treat lower limb injuries. It has been hypothesized that muscle strength would increase and EMG activity of GM decrease after the application of KT over GM in athletes with CAI.     

INFLUENCE OF LIMB DOMINANCE AND SHOULDER INJURY ON STRENGTH AND EXPLOSIVE FORCE IN US MARINES

Background:The specialized roles of many military personnel require specific skills and high physical demands, placing unique stresses on the shoulders and increasing risk of injury. As normal dominant/nondominant shoulder asymmetries have been established in military personnel, bilateral strength comparisons must be understood in context of daily physical demands to monitor patients’ progress or readiness to return to duty.Purpose:This study aims to assess bilateral differences in strength and explosive force in United States Marines with a history of dominant or nondominant shoulder pathology.Study Design:Cross-Sectional.Methods:A total of 52 full-duty, male US Marines with a shoulder injury within the prior year participated. Bilateral isokinetic shoulder internal (IR) and external (ER) rotation strength, and peak force (Peak Force) and average rate of force production (Avg Rate) during an explosive push-up were collected. Dominant versus nondominant side data were independently examined within each group (DOM: dominant injury, NOND: nondominant injury). Comparison between DOM and NOND, as well as previously published CON (no history of shoulder injury) was also completed.Results:NOND (n = 26) demonstrated significantly less IR (p < 0.001) and ER (p = 0.003) strength and Peak Force (p = 0.001) and Avg Rate (p = 0.047) on the injured side, while DOM (n = 26) demonstrated no bilateral differences in strength or push-up performance. Comparison between the three groups showed that NOND demonstrated significantly less ER strength than CON (p = 0.022).Conclusions:Military personnel demonstrate asymmetric strength patterns likely due to increased demand of the dominant shoulder. US Marines with a history of injury to the nondominant shoulder performed differently than those with a dominant side injury, presenting with both strength and push-up asymmetries. They also demonstrated significant ER strength deficits compared to CON. Common clinical practice and previous literature often compare injured and uninjured limbs or injured individuals to healthy controls, but further distinction of dominant or nondominant side may provide more accurate information needed to develop targeted treatment strategies.Clinical Relevance:Recognizing unique occupational demands and how patients may present differently with dominant versus nondominant side shoulder injuries are important considerations for ensuring accurate assessment and effective individualized rehabilitation.Level of Evidence:3.