Comparison of two measurement devices for obtaining horizontal force-velocity profile variables during sprint running

This study established the magnitude of systematic bias and random error of horizontal force-velocity (F-v) profile variables obtained from a 1080 Sprint compared to that obtained from a Stalker ATS II radar device. Twenty high-school athletes from an American football training group completed a 30 m sprint while the two devices simultaneously measured velocity-time data. The velocity-time data were modelled by an exponential equation fitting process and then used to calculate individual F-v profiles and related variables (theoretical maximum velocity, theoretical maximum horizontal force, slope of the linear F-v profile, peak power, time constant tau, and horizontal maximal velocity). The devices were compared by determining the systematic bias and the 95% limits of agreement (random error) for all variables, both of which were expressed as percentages of the mean radar value. All bias values were within 6.32%, with the 1080 Sprint reporting higher values for tau, horizontal maximal velocity, and theoretical maximum velocity. Random error was lowest for velocity-based variables but exceeded 7% for all others, with slope of the F-v profile being greatest at ±12.3%. These results provide practitioners with the information necessary to determine if the agreement between the devices and the magnitude of random error is acceptable within the context of their specific application.

The Effect of 16 Weeks of Lower-Limb Strength Training in Jumping Performance of Ballet Dancers

Jumping ability is considered a determinant of performance success. It is identified as one of the predictors and talent identification in many sports and dance. This study aimed to investigate the effect of 16 weeks of lower-limb strength training on the jumping performance of ballet dancers. A total of 24 participants from the same dance school were randomly selected in the control group [CG; n = 10; aged 13.00 (1.49) years; 43.09 (9.48) kg and 1.53 (0.11) m] and the intervention group [IG; n = 14; aged 12.43 (1.45) years; 38.21 (4.38) kg and 1.51 (0.07) m], evaluated before and after the applied strength training program mainly using the body weight of each participant. Jump performance was assessed using MyJump2, a scientifically validated mobile phone app. Intergroup and intragroup comparisons were assessed, and the magnitude of change was calculated using the effect size (ES). While CG significantly decreased the relative power over time (p < 0.001, ES = −0.29: small), results from the intragroup comparisons suggest that IG significantly increased the countermovement jump (CMJ) height (p < 0.001, ES = 1.21: large), the relative force (p < 0.001, ES = 0.86: moderate), maximal velocity (p < 0.001, ES = 1.15: moderate), and relative power (p < 0.001, ES = 1.37: large). We concluded that a 16-week strength training program of lower limbs is an effective way to improve CMJ height in young dancers. Supplementary strength training appears to be the determinant for the improvement of the jumping performance of ballet dancers.

The Effects of Vertical vs. Horizontal plyometric Training on Sprinting Kinetics in Post Peak Height Female Student Athletes

Plyometric training is a form of jump training that is a useful method to improve sprinting speed due to its propensity to improve neural efficiency, increase joint stiffness and contraction speed. While research has shown that plyometrics can improve jumping and sprinting performance, no studies have compared the effects of different types of plyometric training on sprinting speed in young females. Therefore, the aim of the study was to compare different forms of plyometric training (horizontal and vertical) on sprinting performance in young females. Thirty young females from a private girls college were randomly divided into two groups and trained for seven weeks, twice a week; vertical plyometric (n=11, age 13.50 ± 0.96, peak heigh velocity-PHV: 1.60 ± 1.14), horizontal plyometric training (n=10, 13.40 ± 0.92, PHV:1.60 ± 0.93), and a physical education class as a control (n=15, age, 15.60 ± 0.31, PHV: 2.90 ± 0.55). Participants were tested for sprinting kinetics i.e. force (Fo), maximum power (Pmax), theoretical velocity (Vo), maximal velocity (Vmax), 10, 20 and 30 m split times using a radar gun over 30 m, isometric strength, vertical jump height and horizontal jump distance before and after the intervention. Both the intervention groups significantly improved all performance variables (g= 0.32- 1.30; p<0.05). The vertical group improved all kinetic variables except Fo and Pmax whereas the horizontal group improved all kinetic variables with a greater effect size g= 0.40-1.30. In comparison to the control group, the vertical group significantly improved Vo, Vmax, vertical and broad jump scores whereas the horizontal group significantly improved broad jump and 20 m split time scores (p<0.05). The findings of this study suggest that horizontal plyometric training is more effective in improving sprinting kinetics.

Effects of Hinged versus Floor-Reaction Ankle-Foot Orthoses on Standing Stability and Sit-to-Stand Performance in Children with Spastic Diplegic Cerebral Palsy

Hinged ankle-foot orthoses (HAFOs) and floor reaction ankle-foot orthoses (FRAFOs) are frequently prescribed to improve gait performance in children with spastic diplegic cerebral palsy (CP). No study has investigated the effects of FRAFO on sit-to-stand (STS) performance nor scrutinized differences between the application of HAFOs and FRAFOs on postural control. This study compared the effects of HAFOs and FRAFOs on standing stability and STS performance in children with spastic diplegic CP. Nine children with spastic diplegic CP participated in this crossover repeated-measures design research. Kinematic and kinetic data were collected during static standing and STS performance using 3-D motion analysis and force plates. Wilcoxon signed ranks test was used to compare the differences in standing stability and STS performance between wearing HAFOs and FRAFOs. The results showed that during static standing, all center of pressure (COP) parameters (maximal anteroposterior/mediolateral displacement, maximal velocity, and sway area) were not significantly different between FRAFOs and HAFOs. During STS, the floor reaction force in the vertical direction was significantly higher with FRAFOs than with HAFOs (p = 0.018). There were no significant differences in the range of motion in the trunk, knee, and ankle, the maximal velocity of COP forward displacement, completion time, and the force of hip, knee, and ankle joints between the two orthoses. The results suggest both FRAFOs and HAFOs have a similar effect on standing stability, while FRAFOs may benefit STS performance more compared to HAFOs.

Convective and turbulent motions in non-precipitating Cu. Part II: LES simulated cloud represented by a starting plume

The dynamic structure of a small trade-wind Cu is analyzed using a novel approach. Cu developing in a shear-free environment was simulated by 10 m-resolution LES model with spectral bin microphysics. The aim is to clarify the dynamical nature of cloud updraft zone (CUZ) including entrainment and mixing in growing Cu. The validity of concept stating that a cloud at developing state can be represented by a parcel or a jet is tested. To investigate dynamical entrainment in CUZ performed by motions with scales larger than the turbulence scales, the modeled fields of air velocity were filtered by wavelet filter which separated convective motions from turbulent ones. Two types of objects in developing cloud were investigated: small volume ascending at maximal velocity (point parcel) and CUZ. It was found that the point parcel representing the upper part of cloud core is adiabatic. The motion of the air in this parcel ascending from cloud base determines cloud top height. The top hat (i.e., averaged) values of updraft velocity and adiabatic fraction in CUZ are substantially lower than those in the point parcel. Evaluation of the terms in the dynamical equation typically used in 1D cloud parcel models show that this equation can be applied for calculation of vertical velocities at the developing stage of small Cu, at least up to the heights of the inversion layer. Dynamically, the CUZ of developing cloud resembles the starting plume with the tail of non-stationary jet. Both the top hat vertical velocity and buoyancy acceleration linearly increase with the height, at least up to the inversion layer. An important finding is that lateral entrainment of convective (non-turbulent) nature has a little effect on the top hat CUZ velocity and cannot explain the vertical changes of conservative variables qt and θl. In contrast, entrained air lifting inside CUZ substantially decreases top hat liquid water content and its adiabatic fraction. Possible reasons of these effects are discussed.

Effectiveness and relationship between biased and unbiased measures of dopamine release and clearance

Fast-scan cyclic voltammetry (FSCV) is an effective tool for measuring dopamine (DA) release and clearance throughout the brain, including the ventral and dorsal striatum. Striatal DA terminals are abundant with signals heavily regulated by release machinery and the dopamine transporter (DAT). Peak height is a common method for measuring release but can be affected by changes in clearance. The Michaelis-Menten model has been a standard in measuring DA clearance, but requires experimenter fitted modeling subject to experimenter bias. The current study presents the use of the first derivative (velocity) of evoked DA signals as an alternative approach for measuring dopamine release and clearance and can be used to distinguish the two measures. Maximal upwards velocity predicts reductions in DA peak height due to D2 and GABAB receptor stimulation and by alterations in calcium concentrations. The Michaelis-Menten maximal velocity (Vmax) measure, an approximation for DAT numbers, predicted maximal downward velocity in slices and in vivo. Dopamine peak height and upward velocity were similar between wildtype C57 (WT) and DAT knock out (DATKO) mice. In contrast, downward velocity was considerably reduced and exponential decay (tau) was increased in DATKO mice, supporting use of both measures for changes in DAT activity. In slices, the competitive DAT inhibitors cocaine, PTT and WF23 increased peak height and upward velocity differentially across increasing concentrations, with PTT and cocaine reducing these measures at high concentrations. Downward velocity and tau values decreased and increased respectively across concentrations, with greater potency and efficacy observed with WF23 and PTT. In vivo recordings demonstrated similar effects of WF23 and PTT on measures of release and clearance. Tau was a more sensitive measure at low concentrations, supporting its use as a surrogate for the Michaelis-Menten measure of apparent affinity (Km). Together, these results inform on the use of these measures for DA release and clearance.

Purification and characterization of actinidin from Actinidia deliciosa and its utilization in inactivation of α-amylase

Background Actinidin is an anionic thiol-proteinase predominant and unique to Chinese gooseberry or kiwifruit, whose strong digestibility enables proteins or enzymes vulnerable to digestion. The arrangement of active cysteine–thiol residues (Cys22-Cys65, Cys56-Cys98, and Cys156-Cys206) stabilizes the catalytic unit, thus allowing an effective Inhibition of α-amylase protein on exposure to the highest concentrations of actinidin under optimum conditions. When starch-rich foods are consumed with kiwifruit, starch digestion may be slowed by the inactivation of α-amylase (digestive enzyme), specifically reducing the blood sugar levels by hindering starch digestion that is helpful in diabetes mellitus. Thus, the study aimed at actinidin purification, optimization for maximal activity, and its demonstration as a potential to degrade α-amylase. Results Protease showed a molecular mass of 27 kDa on SDS-PAGE analysis. One factor at a time method was applied for process optimization, increasing the actinidin yield up to 176.03 U/mg. The enzyme was stable at a wide pH range; however, it was most active and stable at pH 7.5. The enzyme possessed half‐life at 35 °C of 5.5 h, at 40 °C of 4.5 h, at 45 °C of 2.5 h, and at 50 °C of 1 h. Lineweaver–Burk plot showed Michaelis–Menten constant (Km: 3.14 mg/ml) and maximal velocity (Vmax: 1.428 mmol/ml/min) using casein. The actinidin activity was enhanced with Ca2+ while it was inhibited by Cd2+ and Hg2+ ions. The α-amylase protein was successfully inactivated upon incubation with actinidin for 30 min; around ~ 85% of the α-amylase activity diminished. IC50 for inhibition of α-amylase was 2.54 mg/ml for crude actinidin and 1.86 mg/ml for purified actinidin. Conclusions Purified Actinidin showed a 1.28-fold increase in proteolytic activity. The proteinase showed an active pH range of 3.5–8.5 under varied buffer conditions and thermostability up to 50 °C. The results revealed a significant potential utility of actinidin to retard amylase as it effectively degraded the amylolytic enzyme under in vitro conditions and could be beneficial for lowering glycemic response to ingested starch. However, further in vitro as well as in vivo studies need to be conducted under gastrointestinal conditions to establish the hypothesis.

Development and Validation of Prediction Formula of Wingate Test Peak Power From Force–Velocity Test in Male Soccer Players

Peak power of the Wingate anaerobic test (WAnT), either in W (Ppeak) or in W.kg–1 (rPpeak), has been widely used to evaluate the performance of soccer players; however, its relationship with force–velocity (F-v) test (e.g., whether these tests can be used interchangeably) has received little scientific attention so far. The aim of this work was to develop and validate a prediction equation of Ppeak and rPpeak from F-v characteristics in male soccer players. Participants were 158 adult male soccer players (sport experience 11.4 ± 4.5 years, mean ± standard deviation, approximately five weekly training units, age 22.6 ± 3.9 years, body mass 74.8 ± 7.8 kg, and height 178.3 ± 7.8 cm) who performed both WAnT and F-v test. An experimental (EXP, n = 79) and a control group (CON, n = 79) were used for development and validation, respectively, of the prediction equation of Ppeak and rPpeak from F-v test. In EXP, Ppeak correlated very largely with body mass (r = 0.787), fat-free mass (r = 0.765), largely with maximal power of F-v test (Pmax; r = 0.639), body mass index (r = 0.603), height (r = 0.558), moderately with theoretical maximal force (F0; r = 0.481), percentage of body fat (r = 0.471), fat mass (r = 0.443, p &lt; 0.001); rPpeak correlated with rPmax (largely; r = 0.596, p &lt; 0.001), theoretical maximal velocity (v0; moderately; r = 0.341, p = 0.002), F0 (small magnitude; r = 0.280, p = 0.012), BF (r = −0.230, p = 0.042), and fat mass (r = −0.242, p = 0.032). Ppeak in EXP could be predicted using the formula “44.251 + 7.431 × body mass (kg) + 0.576 × Pmax (W) – 19.512 × F0” (R = 0.912, R2 = 0.833, standard error of estimate (SEE) = 42.616), and rPpeak from “3.148 + 0.218 × rPmax (W.kg–1) + v0 (rpm)” (R = 0.765, R2 = 0.585, SEE = 0.514). Applying these formulas in CON, no bias was observed between the actual and the predicted Ppeak (mean difference 2.5 ± 49.8 W; 95% CI, −8.7, 13.6; p = 0.661) and rPpeak (mean difference 0.05 ± 0.71 W.kg–1; 95% CI, −0.11, 0.21, p = 0.525). These findings provided indirect estimates of Ppeak of the WAnT, especially useful in periods when this test should not be applied considering the fatigue it causes; in this context, the F-v test can be considered as an alternative of exercise testing for estimating the average Ppeak of a group of soccer players rather than for predicting individual scores when the interindividual variation of performance is small.

Bounds for rotating Rayleigh–Bénard convection at large Prandtl number

Bounds are derived for rotating Rayleigh–Bénard convection with free slip boundaries as a function of the Rayleigh, Taylor and Prandtl numbers ${\textit {Ra}}$ , ${\textit {Ta}}$ and ${\textit {Pr}}$ . At infinite ${\textit {Pr}}$ and ${\textit {Ta}} > 130$ , the Nusselt number ${\textit {Nu}}$ obeys ${\textit {Nu}} \leqslant \frac {7}{36} \left ({4}/{{\rm \pi} ^2} \right )^{1/3} {\textit {Ra}} {\textit {Ta}}^{-1/3}$ , whereas the kinetic energy density $E_{kin}$ obeys $E_{kin} \leqslant ({7}/{72 {\rm \pi}}) \left ({4}/{{\rm \pi} } \right )^{1/3} {\textit {Ra}}^2 {\textit {Ta}}^{-2/3}$ in the frame of reference in which the total momentum is zero, and $E_{kin} \leqslant ({1}/{2{\rm \pi} ^2})({{\textit {Ra}}^2}/{{\textit {Ta}}})({\textit {Nu}}-1)$ . These three bounds are derived from the momentum equation and the maximum principle for temperature and are extended to general ${\textit {Pr}}$ . The extension to finite ${\textit {Pr}}$ is based on the fact that the maximal velocity in rotating convection at infinite ${\textit {Pr}}$ is bound by $1.23 {\textit {Ra}} {\textit {Ta}}^{-1/3}$ .

Kinetics and kinematics of sprinting in mid and post peak height velocity female athletes

Sprinting speed is a crucial physical capacity and can change throughout an athlete’s growth. Previous research has shown that both kinetic and kinematic variables change across maturation in young males. However, due to the changes in growth and hormonal levels, the kinetic and kinematic factors associated with sprinting may vary in young females compared to their male counterparts. Therefore, determining kinetics (force, maximal power) and kinematics (step length, step frequency, contact time and flight time) associated with sprinting in young females can provide valuable insights into training for this cohort. Thirty-two young female athletes, 11 mid-peak height velocity (PHV) age (12.8±0.6) and 21 post PHV (13.5±0.93) performed two 15 and 30 m sprints each. Theoretical velocity, maximal velocity, step length, force and power max were significantly higher in post PHV girls (p<0.05). Univariate regression analysis reported that the best predictors of velocity (15 and 30 m) were contact time, power max, stride frequency, step length and leg length with contact time being the strongest predictor. The findings of this research provide insight into the natural development of sprinting in young females and will help practitioners specifically develop training programs that can effectively improve sprinting kinetics and kinematics in this cohort.