Background: Maintenance of the medial longitudinal arch (MLA) of the foot is fundamental during functional tasks and disorders can lead to clinical alterations. Studies have demonstrated that deficits in ankle isokinetic performance can predispose an individual to lower limb injuries.Objectives: To evaluate the muscular performance of cavus, planus, and normal feet by means of torque/body mass and the isokinetic phases, to generate 3D surface map analysis, and to verify whether there is a relationship between MLA height and arch height flexibility with isokinetic performance.Methods: The sample consisted of 105 healthy adult women, divided into three groups: normal, cavus, and planus. Assessment in concentric mode at 30, 60, and 90 °/s in the dorsiflexion and plantarflexion of the ankle joint were analyzed during the three isokinetic phases (acceleration, sustained velocity, and deceleration). The variables total range of motion, peak of torque (PT), and angle of PT were extracted within the sustained velocity.Results: In dorsiflexion at 60 °/s, the phase where the velocicty is sustained (load range phase) was higher in the planus group (M_eanD_ifference=10.9 %; ω²_p = 0.06) when compared with the cavus group. Deficits in the peak torque/body mass in dorsiflexion at 60 °/s (cavus feet: MD=‐3 N.m/kg; ω²_p = 0.06; and planus feet: MD=‐1.1 N.m/kg; ω²_p = 0.06) were also observed as well as in the 3D surface maps, when compared with the normal group. The flexibility of MLA had a negative correlation of PT at 30 °/s in cavus group. The heigth of MLA had a postive correlation with the PT for the cavus and planus group ate 60 °/s. All other results did not show differences between the groups.Conclusions: The planus groups showed a better capacity of attain and sustained the velocity in dorsiflexion in relation the cavus group. The cavus and planus group had deficts in torque in relation the normal. The correlations were weak between the measures of MLA and PT. Thereby, in general the differences between foot types showed small effect in isokinetic muscle performance measures of the plantar and dorsi flexores.Trial registration: Study design was approved by the IRB (#90238618.8.0000.5231).

The choice of musculoskeletal (MSK) model is crucial for performing MSK estimations to evaluate muscle demands and joint forces. This study compared two previously published generic MSK models and a modified model to estimate tibiofemoral reaction forces (TFRF) during gait, sit-to-stand, and stand-to-sit. The estimated tibiofemoral reaction forces were compared with an in vivo dataset from six patients using an instrumented knee prosthesis. A correlation and root mean square error (RMSE) in the time-series analysis and relative peak error (RPE) were evaluated. The results showed that the three MSK models were similar in estimating the vertical forces, with a large correlation, and RPE was found around 20 % during gait. The RMSE and the RPE indicated that the modified model had lower total and lateral compartment forces errors for sit-to-stand and stand-to-sit, showing the best performance. The shear forces for all tasks and models showed significant errors. Future MSK studies should consider these findings when researching functional tasks. The modified model was found to be more effective in estimating the vertical tibiofemoral joint reaction forces in tasks that impose greater demands on muscle forces and require high knee and hip flexion.

Background: Many studies have investigated isokinetic performance in volleyball players but not through surface maps. Objectives: The goals of this study were to assess velocity-specific isokinetic knee extensor-flexor muscle strength and to compare the isokinetic knee extensor-flexor muscles between professional (PRO) and under-17 (U17) female volleyball players. Method: This cross-sectional laboratory study was developed with two groups: PRO (n = 12), median(age) = 21.3 years, and U17 (n = 9), median(age) = 15 years. Peak torque, total work, mean power, angle of peak torque, hamstring-quadriceps torque ratio (H-Q ratio) and torque-angle-velocity surface maps were analysed from knee extension-flexion at 60, 120 and 300 degrees per second (degrees/s). Results: Significant differences were identified for extensor peak torque between PRO (x) over bar= 202.3 Newton metre (N.m) (standard deviation [SD] = 24.4) and U17 (x) over bar = 141.6 N.m (30.1) at 60 degrees/s (p < 0.001; <(d)over bar> = 2.21) as well as flexor peak torque (PRO (x) over bar = 75.7 N.m [10.3] and U17 (x) over bar = 57.7 N.m [11.4]) at 120 degrees/s (p < 0.001; <(d)over bar> = 1.65) for the dominant limb. There were also significant group differences for total work and mean power at all velocities for extension and flexion. Surface maps demonstrated higher torque at lower speeds for both groups with smaller torque changes across velocities for flexion. Conclusion: Different groups of female volleyball players showed contrasting concentric knee muscle strength across isokinetic velocities. Clinical implications: These results demonstrate the importance of specific strength training for different age groups, even within the same sport, and provide insight into muscle strength.

The Low Back Activity Confidence Scale (LoBACS) assesses the self-efficacy to perform activities in individuals with chronic low back pain (CLBP). As self-efficacy appears to directly influence the patient’s functional capacity and prognosis, it is important to develop a scale that evaluates this attribute to guide treatment strategy and monitor the clinical course of patients. This study aimed to evaluate the reliability, construct validity, and responsiveness of the Brazilian version of the LoBACS. The scale was applied to 112 male and female patients (age, 18–65 years) with specific and nonspecific CLBP. For evaluating the interobserver reliability, the scale was applied twice on the first evaluation day by two trained evaluators (A and B). Within 48–72 h of the first evaluation, assessor A reapplied the scale to evaluate intraobserver reliability (test–retest), which was analyzed by intraclass correlation coefficient (ICC). The first LoBACS applied in the baseline evaluation was also used to assess the construct validity of the scale by factor analysis. For responsiveness, the scale was applied 5 times at 2-week intervals and the change in scores was analyzed by the repeated measures ANOVA. Although factor analysis indicated three subscales, they did not present acceptable values of convergent and divergent validity. Reliability ranged from good to excellent, with ICC values of .90 (95% CI, .84; .93) and .85 (95% CI, .77; .91) for inter- and intraobserver variability for total score. Moreover, the total score was responsive in all comparisons, with no floor or ceiling effects. Thus, only the total score of the Brazilian version of LoBACS proved to be reliable, valid, and responsive.

Many patients report more difficulty when descending stairs compared to level walking after total knee arthroplasty (TKA). Different implant designs can affect knee biomechanics and muscle activity during gait, but their effect during stair descent is unclear. The purpose of this study was to evaluate knee biomechanics and muscle activations of quadriceps, hamstrings, and gastrocnemius muscles during a stair descent task in patients who underwent TKA with either a posterior stabilized (PS) or medial ball-and-socket (MBS) implant and to compare them to a group of healthy controls. There were 28 TKA patients who were randomized to either an MBS (n = 14) or PS (n = 14) implant and were compared with 14 controls. Patients visited the biomechanics lab approximately 12 months after TKA, where knee biomechanics and muscle activity were measured as they descended a three-step staircase. Compared to the MBS and control groups, the PS group descended the stairs with a reduced knee flexion angle and greater hamstring muscle activation throughout single limb support. Knee joint moments and power were similar between the MBS and PS groups, but neither reached the level of the control group. Lower knee flexion angles and increased hamstring muscle activity indicated that the PS group descended the stairs with a stiffer knee gait pattern than the MBS group. The MBS implant design may provide additional stability as patients require less muscle activity than the PS group.