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The Nordic hamstring curl appears effective in reducing the incidence of injury in physically active young adults, likely through its capacity as an eccentric exercise to increase muscle stiffness. Although eccentric exercises have been shown to increase muscle stiffness, medium- and long-term Nordic hamstring curl training programs have not demonstrated an effect on muscle stiffness. This study examined the acute effects of a single session of Nordic hamstring curls on the stiffness of the biceps femoris, semitendinosus, and semimembranosus muscles using ultrasound shear wave elastography, an accepted method for measuring passive muscle stiffness.

The KinaTrax markerless motion capture system, used extensively in the analysis of baseball pitching and hitting, is currently being adapted for use in clinical biomechanics. In clinical and laboratory environments, repeatability is inherent to the quality of any diagnostic tool. The KinaTrax system was assessed on within- and between-session reliability for gait kinematic and spatiotemporal parameters in healthy adults. Nine subjects contributed five trials per session over three sessions to yield 135 unique trials. Each trial was comprised of a single bilateral gait cycle. Ten spatiotemporal parameters for each session were calculated and compared using the intraclass correlation coefficient (ICC), Standard Error of the Measurement (SEM), and minimal detectable change (MDC). In addition, seven kinematic waveforms were assessed from each session and compared using the coefficient of multiple determination (CMD). ICCs for between-session spatiotemporal parameters were lowest for left step time (0.896) and left cadence (0.894). SEMs were 0.018 (s) and 3.593 (steps/min) while MDCs were 0.050 (s) and 9.958 (steps/min). Between-session average CMDs for joint angles were large (0.969) in the sagittal plane, medium (0.554) in the frontal plane, and medium (0.327) in the transverse plane while average CMDs for segment angles were large (0.860), large (0.651), and medium (0.561), respectively. KinaTrax markerless motion capture system provides reliable spatiotemporal measures within and between sessions accompanied by reliable kinematic measures in the sagittal and frontal plane. Considerable strides are necessary to improve methodological comparisons, however, markerless motion capture poses a reliable application for gait analysis within healthy individuals. [ABSTRACT FROM AUTHOR]

Velocity-based training (VBT) positively impacts muscle morphology and performance in persons with Parkinson's disease (PD); however, optimal training frequencies for VBT in patients with PD remain undetermined. Changes in ultrasound-determined muscle thickness (MT) and echo intensity (EI)-derived muscle quality of the rectus femoris (RF) and vastus lateralis (VL), neuromuscular performance, and functional capacity were examined following 2 VBT frequencies (2-3 d·wk-1) using 30% velocity loss thresholds for 12 weeks. Neuromuscular performance was assessed using computerized pneumatic resistance machines. For each variable, 2 (time) 3 2 (group) repeated-measures analyses of variance (ANOVA) were used to determine significant main effects and interactions. Significant time effects were seen for MT and EI of all muscles (p, 0.05). Muscle thickness improvements included right VL (RVL) (0.171 6 0.065 cm; p 5 0.019), left VL (LVL) (0.214 6 0.101 cm; p 5 0.049), right RF (RRF) (0.194 6 0.077 cm; p 5 0.023), and left RF (LRF) (0.318 6 0.109 cm; p 5 0.010). For EI, improvements occurred in RVL (218.688 6 3.600; p5,0.001), LVL (210.959 6 4.894; p 5 0.040), RRF (29.516 6 3.537; p 5 0.016), and LRF (29.018 6 3.444; p 5 0.019). Time effects were seen for leg-press 1-repetition maximum and peak power (p, 0.01) and habitual walking speed (p 5 0.022), with a group by time interaction for maximal gait speed favoring the 3 d·wk-1 condition (δ0.15 m·s21, p 5 0.002). The results indicate that VBT at 2 or 3 d·wk-1 can significantly improve muscle morphology, neuromuscular performance, and functional capability in patients with PD; however, improvements in maximal gait speed require 3 d·wk21. These findings provide flexibility when developing exercise prescriptions for patients with PD. [ABSTRACT FROM AUTHOR]

Accurate determinations of individuals' one-repetition maximum (1RM) are critical when evaluating the effectiveness of an exercise intervention involving progressive resistance training (RT). Traditional ("bottom-up"; BT) testing methods involve progressions from low to maximal loads and are commonly used in clinical and laboratory environments. Concerns about the reliability of BT testing in certain populations suggest a different technique may be more effective. Purpose: To compare the reliability and effectiveness of traditional 1RM testing to a novel technique (TDT) involving progressive load reductions and a starting intensity equal to 130% of exercisers' estimated 1RM. Method: 70 healthy adults (age = 45.03 ± 25.64 y) with diverse RT experience were randomized into a reliability testing trial (RTT; n = 33) or an optimal method trial (OMT; n = 37). Subjects in the RTT performed either TDT or BT on 3 occasions separated by = 72 hours, while subjects in the OMT performed each method once in random order on separate days. Results: No significant differences in percent coefficient of variation were observed between BT and TDT for either exercise used in the study (pneumatic seated chest press: Hedge's g = 0.25, p = 0.49; pneumatic recumbent leg press: Hedge's g = 0.12, p = 0.74). TDT was not found to produce significantly higher 1RM values than BT in any group. Conclusion: TDT does not appear to facilitate more reliable 1RM estimates than BT. Further research is needed to determine the stability of these findings across levels of exercisers' age, sex, and previous RT experience.

The purpose of this work was to provide a simple method to determine reactive strength during the 6-meter timed hop test (6mTH) and evaluate its association with isokinetic peak torque in patients following anterior cruciate ligament reconstruction (ACLR). Twenty-nine ACLR patients who were at least four months from surgery were included in this analysis. Participants were brought into the laboratory on one occasion to complete functional testing. Quadriceps and hamstring isokinetic testing was completed bilaterally at 60, 180, and 300 deg∙s-1, using extension peak torque from each speed as the outcome measure. The 6mTH was completed bilaterally using a marker-based motion capture system, and reactive strength ratio (RSR) was calculated from the vertical velocity of the pelvis during the test. An adjustment in RSR was made using the velocity of the 6mTH test to account for different strategies employed across participants. Repeated measures correlations were used to determine associations among isokinetic and hop testing variables. A two-way mixed analysis of variance was used to determine differences in isokinetic and hop testing variables between operated and non-operated legs and across male and female participants. Moderate positive associations were found between RSR (and adjusted RSR) and isokinetic peak torque at all speeds (r =.527 to.577). Mean comparisons showed significant main effects for leg and sex. Patients showed significant deficits in their operated versus non-operated legs in all isokinetic and hop testing variables, yet only isokinetic peak torque and timed hop time showed significant differences across male and female groups. Preliminary results are promising but further development is needed to validate other accessible technologies available to calculate reactive strength during functional testing after ACLR. Pending these developments, the effects of movement strategies, demographics, and levels of participation on RSR can then be explored to translate this simple method to clinical environments. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this study was to examine the impact of an 8-week high-speed circuit resistance training program (HSCT) on choriocapillaris density (CCD) in healthy older adults. Methods: Eighteen cognitively normal older adults were enrolled and randomly assigned to either the HSCT or the control group (CON). The HSCT group was comprised of 11 participants who trained three times a week for eight weeks, while the CON group consisted of 7 participants who did not engage in formal training. Optical coherence tomography angiography (OCTA) was employed to image both eyes of each subject at baseline and at the 8-week follow-up. The choriocapillaris density (CCD) of 2.5 mm in diameter centered on the fovea was measured. Results: The average age of the HSCT group was 70.3 ± 5.7 years, which was not different from the CON group (average age: 71.6 ± 5.2 years, p = 0.62). There were no significant changes in CCD between baseline and the 8-week follow-up in either the HSCT or the CON group—specifically, the baseline CCD in the HSCT group was 63.3% ± 5% (Mean ± SD), which did not differ significantly from the 8-week follow-up after HSCT training (64.7% ± 4%, p = 0.19). Likewise, there was no significant difference in CCD between baseline and the 8-week follow-up in the CON group (63.3% ± 3% and 62.7% ± 5%, respectively, p = 0.66). Conclusion: CCD appeared to remain stable after 8 weeks of HSCT in healthy older individuals, possibly due to autoregulation. Further research with extended training may be necessary to verify these findings. [ABSTRACT FROM AUTHOR]