Semitendinosus and biceps femoris long head active stiffness response until failure in professional footballers with vs. without previous hamstring injury.

This study sought to examine the active stiffness of semitendinosus (ST) and biceps femoris long head (BFlh) during a knee flexor isometric contraction at 20% of maximal voluntary isometric contraction until failure in elite footballers (n = 50, age: 22.3 ± 5.3 years; height: 1.82 ± 0.08 m; body mass: 74.7 ± 9.0 kg). Active stiffness was assessed using ultrasound-based shear wave elastography by means of shear modulus quantification. Comparisons were performed between limbs with (n = 11) vs. without (n = 89) previous hamstring injury. A similar time until failure in the knee flexor fatigue task was observed between groups (p = .401). At the start of the task, lower limbs with previous hamstring injury showed a lower BFlh active stiffness (31.0.1 ± 10.4 kPa, p = .023) and BFlh/ST active stiffness ratio (0.50 ± 0.29), and no differences for ST (72.8 ± 26.8 kPa, p = .221) compared to lower limbs without previous hamstring injuries (BFlh: 38.0 ± 9.6 kPa; ST: 64.0 ± 18.4 kPa; BFlh/ST: 0.65 ± 0.27). During the task, the ST active stiffness in both groups decreased from 80% of task time (p = .032), in the absence of changes in BFlh active stiffness (p = .534), resulting in an increase in BFlh/ST active stiffness from 80% of task time (p = .029). No differences between limbs were observed during the fatigue task for all parameters (p > .099). Future research is warranted to verify if the differences found represent an increased risk of hamstring injury. HighlightsThe hamstring's active stiffness response to a fatigue protocol in soccer athletes with a history of injury is unknown.Athletes with previous injury showed less active stiffness in the biceps femoris long head.Similar response to fatigue was observed between athletes with and without hamstring injury history.

T2* mapping of subtalar cartilage: Precision and association between anatomical variants and cartilage composition.

Hindfoot arthritis is an important contributor to foot pain and physical disability. While the subtalar joint (STJ) is most frequently affected, anatomical variants such as facet configuration were suggested to further STJ cartilage deterioration. T2* mapping enables detection of ultra-structural cartilage change, particularly in thin cartilage layers, but its feasibility in the STJ has not yet been evaluated. The purpose of this study was to evaluate segmentation consistency and inter-scan short-term precision error of T2* mapping of talocalcaneal cartilage and to investigate the relationship between facet configuration and STJ T2* values. Using 3Tesla morphological magnetic resonance imaging, STJ configuration was categorized according to the degree of fusion between anterior, medial, or posterior facets. Subsequently, two repeats of multi-echo gradient recalled echo sequences were performed to obtain T2* maps with repositioning. Segmentation consistency of T2* values attained an ICC of 0.90 (95%CI 0.69-0.99). Precision errors comprised a coefficient of variation (CV) ranging 0.01-0.05, corresponding to a root mean square CV of 0.03-0.04. A 2-joint configuration type (i.e., fused anterior-medial facets) was significantly associated with a decrease in posterior facet T2* values (ß = -0.6, p = 0.046). STJ T2* mapping is a reliable method requiring at least a 4% difference within people to enable detection of significant change. Anatomical variants in STJ configuration were associated with T2* values with the more stable 3-joint types exhibiting more favorable cartilage outcomes. Longer-term larger-scaled studies focusing on arthritis pathology are needed to further support the use of T2* mapping in hindfoot disease monitoring. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1969-1976, 2016.

In vivo deformation of thin cartilage layers: Feasibility and applicability of T2* mapping.

The objectives of this study were as follows: (i) to assess segmentation consistency and scan precision of T2* mapping of human tibio-talar cartilage, and (ii) to monitor changes in T2* relaxation times of ankle cartilage immediately following a clinically relevant in vivo exercise and during recovery. Using multi-echo gradient recalled echo sequences, averaged T2* values were calculated for tibio-talar cartilage layers in 10 healthy volunteers. Segmentation consistency and scan precision were determined from two repeated segmentations and two repeated acquisitions with repositioning, respectively. Subsequently, acute in vivo cartilage loading responses were monitored by calculating averaged tibio-talar T2* values at rest, immediately after (i.e., deformation) and at 15 min (i.e., recovery) following a 30-repetition knee bending exercise. Precision errors attained 4-6% with excellent segmentation consistency point estimates (i.e., intra-rater ICC of 0.95) and acceptable limits of confidence. At deformation, T2* values were increased in both layers [+16.1 (10.7)%, p = 0.004 and +17.3 (15.3)%, p = 0.023, for the talus and tibia, respectively] whereas during recovery no significant changes could be established when comparing to baseline [talar cartilage: +5.2 (8.2)%, p = 0.26 and tibial cartilage: +6.6 (10.4)%, p = 0.23]. T2* mapping is a viable method to monitor deformational behavior in thin cartilage layers such as ankle cartilage. Longitudinal changes in T2* can be reliably appraised and require at least 4-6% differences to ascertain statistical significance. The ability to detect considerable change even after non-strenuous loading events, endorses T2* mapping as an innovative method to evaluate the effects of therapeutic exercise on thin cartilage layers. © 2015 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:771-778, 2016.

Are mechanics different between male and female runners with patellofemoral pain?

INTRODUCTION: Patellofemoral pain (PFP) has often been attributed to abnormal hip and knee mechanics in females. To date, there have been few investigations of the hip and knee mechanics of males with PFP. The purpose of this study was to compare the lower extremity mechanics and alignment of male runners with PFP with healthy male runners and female runners with PFP. We hypothesized that males with PFP would move with greater varus knee mechanics compared with male controls and compared with females with PFP. Furthermore, it was hypothesized that males with PFP would demonstrate greater varus alignment. METHODS: A gait and single-leg squat analysis was conducted on each group (18 runners per group). Measurement of each runner's tibial mechanical axis was also recorded. Motion data were processed using Visual 3D (C-Motion, Bethesda, MD). ANOVAs were used to analyze the data. RESULTS: Males with PFP ran and squatted in greater peak knee adduction and demonstrated greater peak knee external adduction moment compared with healthy male controls. In addition, males with PFP ran and squatted with less peak hip adduction and greater peak knee adduction compared with females with PFP. The static measure of mechanical axis of the tibial was not different between groups. However, a post hoc analysis revealed that males with PFP ran with greater peak tibial segmental adduction. CONCLUSION: Males with PFP demonstrated different mechanics during running and during a single-leg squat compared with females with PFP and with healthy males. Based upon the results of this study, therapies for PFP may need to be sex specific.

Descriptive profile of scapulothoracic position, strength and flexibility variables in adolescent elite tennis players.

STUDY DESIGN: Descriptive study, cross-sectional design. BACKGROUND: Tennis requires repetitive overhead movement patterns that can lead to upper extremity injury. The scapula plays a vital role in injury-free playing. Scapular dysfunction has been associated with shoulder injury in the overhead athlete. OBJECTIVES: The purpose of this study was to describe variables regarding scapular position, muscle strength and flexibility in young elite tennis players. METHODS: Thirty-five adolescent Swedish elite tennis players (19 boys, aged 13.6 (+/-1.4) years, 16 girls, aged 12.6 (+/-1.3) years), selected on the basis of their national ranking, underwent a clinical screening protocol consisting of: scapular upward rotation at several angles of arm elevation; isometric scapular muscle strength; and anthropometric measurement of pectoralis minor (PM) length. RESULTS: The players showed significantly more scapular upward rotation on their dominant side (p<0.001). For both genders, upper trapezius (p=0.003) and serratus anterior (p=0.01) strength was significantly greater on the dominant side, whereas middle and lower trapezius strength showed no side differences. PM was shorter on the dominant side (p<0.001), and in the female players (p=0.006) compared with the boys. CONCLUSION: These results indicate some sports-related adaptations of young tennis players on their dominant side at the scapulothoracic level to exposure to their sport. These data may assist the clinician in the prevention and rehabilitation of sport-specific injuries in adolescent tennis players.

Rehabilitation of scapular muscle balance: which exercises to prescribe?

BACKGROUND: Strengthening exercises for the scapular muscles are used in the treatment of scapulothoracic dysfunction related to shoulder injury. In view of the intermuscular and intramuscular imbalances often established in these patients, exercises promoting lower trapezius (LT), middle trapezius (MT), and serratus anterior (SA) activation with minimal activity in the upper trapezius (UT) are recommended. HYPOTHESIS: Of 12 commonly used trapezius strengthening exercises, a selection can be performed for muscle balance rehabilitation, based on a low UT/LT, UT/MT, or UT/SA muscle ratio. STUDY DESIGN: Controlled laboratory study. METHODS: Electromyographic activity of the 3 trapezius parts and the SA was measured in 45 healthy subjects performing 12 commonly described scapular exercises, using surface electromyography. RESULTS: For each intramuscular trapezius ratio (UT/LT, UT/MT), 3 exercises were selected for restoration of muscle balance. The exercises side-lying external rotation, side-lying forward flexion, prone horizontal abduction with external rotation, and prone extension were found to be the most appropriate for intramuscular trapezius muscle balance rehabilitation. For the UT/SA ratio, none of the exercises met the criteria for optimal intermuscular balance restoration. CONCLUSION: In cases of trapezius muscle imbalance, some exercises are preferable over others because of their low UT/LT and UT/MT ratios. CLINICAL RELEVANCE: In the selection of rehabilitation exercises, the clinician should have a preference for exercises with high activation of the LT and MT and low activity of the UT.

Isokinetic scapular muscle performance in young elite gymnasts.

CONTEXT: During gymnastic exercises, considerable force output is required in the shoulder girdle muscles. Isokinetic performance of the scapular muscles in young, elite gymnasts has not been examined. OBJECTIVE: To compare the isokinetic muscle performance of the scapular muscles between elite adolescent gymnasts and nonathletic adolescents to identify differences in strength, endurance, and muscle balance based on high-level sport participation. DESIGN: Single-session, repeated-measures design. SETTING: University human research laboratory. PATIENTS OR OTHER PARTICIPANTS: Sixteen young, elite gymnasts and 26 age-matched nonathletic subjects participated in the study. INTERVENTION(S): Linear protraction-retraction movement in the scapular plane at 2 velocities (12.2 cm/s and 36.6 cm/s). MAIN OUTCOME MEASURE(S): Isokinetic strength and endurance values, peak force/body mass, work/body mass, fatigue index (difference between the work performed in the first third and the last third of the test), and protraction to retraction strength ratios. RESULTS: Elite gymnasts demonstrated higher values for the protraction peak force/body mass than the control group demonstrated (P < .05), and they demonstrated higher protraction to retraction ratios on the nondominant side than on the dominant side (P < .05 at low velocity, P < .001 at high velocity). Work/body mass and fatigue index values were not statistically different between the groups. Side differences (P = .003) for retraction strength with lower protraction to retraction ratios (P < .001) were apparent in the gymnast group on the dominant side. CONCLUSIONS: Scapular muscle performance in elite, young gymnasts is characterized by increased protraction strength and altered muscular balance around the scapula compared with nonathletic adolescents.

Isokinetic Scapular Muscle Performance in Overhead Athletes With and Without Impingement Symptoms.

Context: Overhead activities such as throwing, tennis, or volleyball place athletes at considerable risk for overuse injuries. A relationship between scapulothoracic muscle imbalance and shoulder pain has been suggested.Objective: To compare the isokinetic muscle performance of the scapular muscles between overhead athletes with impingement symptoms and uninjured overhead athletes and to identify strength deficits in the patient population.Design: A repeated-measures analysis of variance with 1 within-subjects factor (side) and 1 between-subjects factor (group) was used to compare strength values and agonist:antagonist ratios across sides and across groups.Setting: University laboratory.Patients or Other Participants: Thirty overhead athletes with chronic shoulder impingement symptoms and 30 overhead athletes without a history of shoulder pain.Intervention(s): A linear protraction-retraction movement in the scapular plane at 2 velocities (12.2 cm/s and 36.6 cm/s).Main Outcome Measure(s): Isokinetic strength values and protraction:retraction ratios for both velocities.Results: Overhead athletes with impingement symptoms showed decreased force output:body weight at both velocities in the protractor muscles on the injured side compared with the uninjured side (-13.7% at slow velocity, -15.5% at high velocity) and compared with the control group at high velocity (-20.7%). On both sides, the patient group had significantly lower protraction:retraction ratios than the control group, measured at slow velocity (nondominant = -11%, dominant = -13.7%).Conclusions: Overhead athletes with impingement symptoms demonstrated strength deficits and muscular imbalance in the scapular muscles compared with uninjured athletes.

Scapular muscle recruitment patterns: trapezius muscle latency with and without impingement symptoms.

BACKGROUND: Altered muscle activity in the scapular muscles is commonly believed to be a factor contributing to shoulder impingement syndrome. However, one important measure of the muscular coordination in the scapular muscles, the timing of the temporal recruitment pattern, is undetermined. PURPOSE: To evaluate the timing of trapezius muscle activity in response to an unexpected arm movement in athletes with impingement and in normal control subjects. STUDY DESIGN: Prospective cohort study. METHODS: Muscle latency times were measured in all three parts of the trapezius muscle and in the middle deltoid muscle of 39 "overhand athletes" with shoulder impingement and compared with that of 30 overhand athletes with no impingement during a sudden downward falling movement of the arm. RESULTS: There were significant differences in the relative muscle latency times between the impingement and the control group subjects. Those with impingement showed a delay in muscle activation of the middle and lower trapezius muscle. CONCLUSION: The results of this study indicate that overhand athletes with impingement symptoms show abnormal muscle recruitment timing in the trapezius muscle. The findings support the theory that impingement of the shoulder may be related to delayed onset of contraction in the middle and lower parts of the trapezius muscle.

Scapular muscle recruitment pattern: electromyographic response of the trapezius muscle to sudden shoulder movement before and after a fatiguing exercise.

STUDY DESIGN: Test-retest reliability study and single-group repeated measures design. OBJECTIVES: To evaluate the muscle latency times of the 3 portions of the trapezius muscle to a sudden arm movement in normal shoulders and to determine if this recruitment pattern is altered as a result of fatigue. BACKGROUND: It has been suggested that shoulder impingement may be related to altered muscle activity and muscle fatigue in the scapular stabilizers. Fatigue-induced changes in latency times of the trapezius might influence scapular stability. METHODS AND MEASURES: Muscle latency times were investigated in 30 healthy shoulders with surface electromyography. Muscle activity was measured in all 3 sections of the trapezius and the middle deltoid muscle during a sudden downward falling movement of the arm. Subsequently the shoulder was fatigued on an isokinetic dynamometer, after which muscle latency time measurement was repeated. RESULTS: ANOVA for repeated measures revealed significant differences in latency times (P < 0.05) among the 4 muscles of interest. Although there were no significant differences among the 3 sections of the trapezius muscle, they all were recruited after the initialization of the deltoid muscle. The recruitment order of the shoulder muscles did not change with muscle fatigue. However, after fatigue, muscle responses were significantly slower in all muscles except for the lower trapezius (P < 0.05). CONCLUSIONS: There is a specific recruitment sequence in the shoulder muscles in response to a sudden arm movement characterized by initial activation of the middle deltoid muscle and followed by simultaneous contraction of all 3 sections of the trapezius. This muscle activation pattern is delayed but not altered with fatigue.