Velocity-Specific Relationships Among Eccentric and Concentric Force Velocity Profiles and Jumping Performance

The purpose of this study is to determine the relationships among force velocity profiles during eccentric only movements (eFVP), concentric only movements (cFVP), and dynamic performance during a countermovement jump (CMJ), squat jump (SJ), and drop jump (DJ). Nineteen collegiate baseball players (1.85 ± 0.04 m, 86.4 ± 8.2 kg, 21.1 ± 1.8 years) from a single NCAA Division I team performed CMJ, SJ, and DJ, drop landings from varying heights, and hex bar jumps with varying weights. FVPs were created with a linear regression using the drop landings for eFVP and hex bar jumps for cFVP, which were used to calculate slopes and area under the entire FVP and velocity-specific regions. Correlations analyzed the results with bootstrapping for 95% confidence intervals. Area under eFVP correlated with cFVP at r=0.51 (p<0.05), cFVP slope presented strong correlations with CMJ height and DJ height while eFVP slopes did not relate to jumping performance or metrics. Area under the faster regions of cFVP and eFVP produced moderate and strong relationships to jumping performance. The area under the FVP, especially when separated into velocity-specific bands, may be a key metric which can audit or provide insight into velocity-based training program effectiveness and athlete comparisons

Quadriceps Strength Influences Patient Function More Than Single Leg Forward Hop During Late-Stage ACL Rehabilitation

# Background A comprehensive battery of tests are used to inform return to play decisions following anterior cruciate ligament (ACL) reconstruction. Performance measures contribute to patient function, but it is not clear if achieving symmetrical performance on strength and hop tests is sufficient or if a patient also needs to meet minimum unilateral thresholds. # Hypothesis/Purpose To determine the association of quadriceps strength and single-leg forward hop performance with patient-reported function, as measured by the IKDC Subjective Knee Form (IKDC), during late-stage ACL rehabilitation. A secondary purpose was to determine which clinical tests were the most difficult for participants to pass. # Study Design Descriptive Laboratory Study # Methods Forty-eight individuals with a history of ACL-R (32 female, 16 male; mean±SD age=18.0±2.7 y; height=172.4±7.6 cm; mass=69.6±11.4 kg; time since surgery=7.7±1.8 months; IKDC=86.8±10.6) completed the IKDC survey, quadriceps isometric strength, and single-leg forward hop performance. The relationship between IKDC scores and performance measures (LSI and involved limb) was determined using stepwise linear regression. Frequency counts were used to determine whether participants met clinical thresholds (IKDC $\geq$ 90%, quadriceps and single-leg forward hop LSI $\geq$ 90%, quadriceps peak torque $\geq$ 3.0 Nm/kg, and single-leg forward hop $\geq$ 80% height for females and $\geq$ 90% height for males). # Results Quadriceps LSI and involved limb peak torque explained 39% of the variance in IKDC scores while measures of single-leg forward hop performance did not add to the predictive model. Nearly 90% of participants could not meet established clinical thresholds on all five tests and quadriceps strength (LSI and peak torque) was the most common unmet criteria (71% of participants). # Conclusions During late-stage ACL rehabilitation deficits in quadriceps strength contribute more to patient function and are greater in magnitude compared to hop test performance. # Level of evidence Cross-Sectional Study, Level

Manual therapy directed at the knee or lumbopelvic region does not influence quadriceps spinal reflex excitability

Manual therapies, directed to the knee and lumbopelvic region, have demonstrated the ability to improve neuromuscular quadriceps function in individuals with knee pathology. It remains unknown if manual therapies may alter impaired spinal reflex excitability, thus identifying a potential mechanism in which manual therapy may improve neuromuscular function following knee injury

Exo70-Mediated Recruitment of Nucleoporin Nup62 at the Leading Edge of Migrating Cells is Required for Cell Migration

Nucleoporin Nup62 localizes at the central channel of the nuclear pore complex and is essential for nucleocytoplasmic transport. Through its FG-repeat domain, Nup62 regulates nuclear pore permeability and binds nuclear transport receptors. Here, we report that Nup62 interacts directly with Exo70 and colocalizes with Exo70 at the leading edge of migrating cells. Nup62 binds the N-terminal domain of Exo70 through its coiled-coil domain but not through its FG-repeat domain. Selective inhibition of leading edge Nup62 using RNA interference significantly reduces cell migration. Furthermore, Exo70 recruits Nup62 at the plasma membrane and at filopodia. Removal of the Exo70-binding domain of Nup62 prevents leading edge localization of Nup62. Analogous to Exo70, Nup62 cycles between the plasma membrane and the perinuclear recycling compartment. Altogether, we propose that Nup62 not solely regulates access to the cell nucleus, but additionally functions in conjunction with Exo70, a key regulator of exocytosis and actin dynamics, at the leading edge of migrating cells

Increased active hamstring stiffness after exercise in women with a history of low back pain

Objective: To compare active hamstring stiffness in female subjects with and without a history of low back pain (LBP) after a standardized 20-min aerobic-exercise session. Design: Case control. Setting: Laboratory. Participants: 12 women with a history of recurrent episodes of LBP (age = 22.4 ± 2.1 y, mass = 67.1 ± 11.8 kg, height = 167.9 ± 8 cm) and 12 matched healthy women (age = 21.7 ± 1.7 y, mass = 61.4 ± 8.8 kg, height = 165.6 ± 7.3 cm). LBP subjects reported an average 6.5 ± 4.7 on the Oswestry Disability Index. Interventions: Participants walked at a self-selected speed (minimum 3.0 miles/h) for 20 min. The treadmill incline was raised 1% grade per minute for the first 15 min. During the last 5 min, participants adjusted the incline of the treadmill so they would maintain a moderate level of perceived exertion through the end of the exercise protocol. Main Outcome Measures: During session 1, active hamstring stiffness, hamstring and quadriceps isometric strength, and concurrently collected electromyographic activity were recorded before and immediately after the exercise protocol. For session 2, subjects returned 48-72 h after exercise for repeat measure of active hamstring stiffness. Results: Hamstring active stiffness (Nm/rad) taken immediately postexercise was not significantly different between groups. However, individuals with a history of recurrent LBP episodes presented significantly increased hamstring stiffness 48-72 h postexercise compared with controls. For other outcomes, there was no group difference. Conclusions: Women with a history of recurrent LBP episodes presented greater active hamstring stiffness 48-72 h after aerobic exercise. © 2013 Human Kinetics, Inc