Search

Aims: We analysed the changes in force-velocity-power variables and jump performance in response to an individualized training program based on the force-velocity imbalance (FVimb). In particular, we investigated (i) the individual adaptation kinetics to reach the optimal profile and (ii) de-training kinetics over the three weeks following the end of the training program. Methods: Sixty subjects were assigned to four sub-groups according to their initial FVimb: high or low force-deficit (FD) and high or low velocity-deficit (VD). The duration of training intervention was set so that each individual reached their “Optimal force-velocity (F-v) profile”. Mechanical and performance variables were measured every 3 weeks during the program, and every week after the end of the individualized program. Results: All subjects in the FD sub-groups showed extremely large increases in maximal theoretical force output (+30±16.6% Mean±SD; ES = 2.23±0.28), FVimb reduction (-74.3±54.7%; ES = 2.17±0.27) and large increases in jump height (+12.4±7.6%; ES = 1.45±0.23). For the VD sub-groups, we observed moderate to extremely large increases in maximal theoretical velocity (+15.8±5.1%; ES = 2.72±0.29), FVimb reduction (-19.2±6.9%; ES = 2.36±0.35) and increases in jump height (+10.1±2.7%; ES = 0.93±0.09). The number of weeks needed to reach the optimal F-v profile (12.6 ± 4.6) was correlated to the magnitude of initial FVimb (r = 0.82, p<0.01) for all participants regardless of their initial subgroup. No significant change in mechanical variables or jump performance was observed over the 3-week de-training period. Conclusions: Collectively, these results provide useful insights into a more specific, individualized (i.e. based on the type and magnitude of FVimb) and accurate training prescription for jumping performance. Considering both training content and training duration together with FVimb may enable more individualized, specific and effective training monitoring and periodization. [ABSTRACT FROM AUTHOR]

Population reduction or eradication of domestic or non-domestic species may be required to address their impacts on the environment, other species, or human interests. Firearms are often used to accomplish these practical management objectives, and there is increased concern that the methods used may compromise animal welfare. We document the accuracy and humaneness of gunshot placement to the brain and cervical vertebrae of Philippine deer (Rusa marianna) on Guam during depopulation activities as a model for meeting AVMA standards of euthanasia under field conditions (e.g., animal is not in hand). Deer were shot with a .223 caliber rifle from 10–125 m and approached immediately (<20 s) for assessment. A subset of adult deer was further evaluated for physiological responses including cessation of heart rate, respiration, ocular reflexes, and post-mortem spasms. All deer shot in the brain (n = 132) and upper cervical spine (C1—C3; n = 18) died immediately due to the destruction of the brain or spinal tissue. Shot placements were all within 1.9 cm of the point of aim (i.e., the center of the target region). The accuracy and immediate insensibility resulting from targeting of C1—C3 demonstrates that this is an alternative target site when animal positioning is not optimal for targeting the brain, or there is a need to preserve brain tissue (e.g., Chronic Wasting Disease testing). While targeting of C4 –C7 vertebrae (n = 6) was accurate and resulted in immediate incapacitation, the failure to produce immediate insensibility does not support the use of this shot placement when upper cervical or brain shot placement is an option. It is reasonable to achieve sufficient accuracy to target the brain or upper cervical vertebrae of deer under field conditions and meet standards of euthanasia while accomplishing management objectives. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the learnability and feasibility of a new technique comprising a needle-guidance-system (NGS) for ultrasound-assisted lumbar puncture. Method: Using a randomized crossover study design, 24 medical students were asked to perform an ultrasound-assisted lumbar puncture on a gel phantom using two different techniques that each included a paramedian insertion site. Procedure 1 (P1) used a pre-procedural ultrasound scan to predetermine the ideal insertion point. Procedure 2 (P2) applied a new technique comprising an NGS for performing real-time ultrasound-guided lumbar puncture. Success rates and performance times for both procedures were compared. Participants were also asked to complete a post-study questionnaire, both to quantitatively assess the workload involved and state their personal preferences. Results: In comparison to the pre-procedural scan (P1), the NGS (P2) was associated with a significant increase in the number of successful punctures per participant (5 (P2) [interquartile range: 3.3–5.0] vs. 3 (P1) [interquartile range: 1.3–4.0], p = 0.005), and led to a significant reduction in performance time (118 seconds vs. 80.6 seconds, p < 0.001). In terms of workload perception, NGS use was associated with significantly better performances and lower frustration levels, as rated by students in the post-study questionnaire. Finally, 23/24 participants stated their preference for P2. Conclusion: Our newly-developed technique for real-time ultrasound-guided lumbar puncture proved to be learnable and feasible for novices, and only required a small amount of training. The use of an NGS therefore has the potential to serve as a key feature of the ultrasound-assisted lumbar puncture. [ABSTRACT FROM AUTHOR]

Locomotion of machines and robots operating in rough terrain is strongly influenced by the mechanics of the ground-machine interactions. A rolling wheel in terrain with obstacles is subject to collisional energy losses, which is governed by mechanics comparable to hopping or walking locomotion. Here we investigate the energetic cost associated with overcoming an obstacle for rolling and hopping locomotion, using a simple mechanics model. The model considers collision-based interactions with the ground and the obstacle, without frictional losses, and we quantify, analyse, and compare the sources of energetic costs for three locomotion strategies. Our results show that the energetic advantages of the locomotion strategies are uniquely defined given the moment of inertia and the Froude number associated with the system. We find that hopping outperforms rolling at larger Froude numbers and vice versa. The analysis is further extended for a comparative study with animals. By applying size and inertial properties through an allometric scaling law of hopping and trotting animals to our models, we found that the conditions at which hopping becomes energetically advantageous to rolling roughly corresponds to animals’ preferred gait transition speeds. The energetic collision losses as predicted by the model are largely verified experimentally. [ABSTRACT FROM AUTHOR]

There is preliminary evidence that there are several types of submovements in movement aiming that reflect different processes of control and can result from particular task constraints. The purpose of the study was to investigate the effect of movement space and time task criteria on the prevalence of different submovement control characteristics in discrete aiming. Twelve participants completed 3 distance x 5 time conditions each with 100 trials in a target-aiming movement task. The kinematic structure of the trajectory determined the prevalence of 5 submovement types (none; pre-peak, post-peak movement velocity; undershoot, overshoot). The findings showed that the overall number of submovements increased in the slower space-time conditions and was predominantly characterized by post-peak trajectory submovements rather than discrete overshoot submovements. Overshoot submovements were more frequent in the high average movement velocity and short time duration conditions. We concluded that there are qualitatively different distributional patterns of submovement types in discrete aiming tasks that are organized by the quantitative scaling of the average movement velocity arising from multiple control processes to meet the specific space-time task constraints. [ABSTRACT FROM AUTHOR]

Purpose: Aging is associated with slow reactive movement generation and poor termination. Objective: We examined the hypothesis that the build-up of excitability in the primary motor cortex in the agonist muscle to generate ballistic wrist flexion and extension and in the antagonist to stop the movement, is lower and slower in old compared with young adults. Methods: We measured the size of the motor potentials evoked (MEP) produced by transcranial magnetic stimulation (TMS), background integrated EMG (iEMG), and the MEP:iEMG ratio in healthy young (23 y, n = 14) and old adults' (73 y, n = 14) wrist flexors and extensors as they rapidly flexed or extended the wrist in response to an auditory cue. TMS was delivered at 80% of resting motor threshold randomly in 20 ms increments between 130 and 430 ms after the tone. Results: Even though old compared to young adults executed the two wrist movements with ~23% longer movement duration and ~15% longer reaction time (both p < 0.05), the rise in MEP:iEMG ratio before the main similar in the two age groups. Conclusion: These data suggest that an adjustment of current models might be needed to better understand how and if age affects the build-up excitability accompanying movement generation and termination. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the relation between the maximum mean propulsive power (MPP) obtained in the loaded jump squat (JS) and half squat (HS) exercises and functional performances in vertical jumps, 40 m linear speed (VEL) and change-of-direction (COD) tests, using the median split technique. Twenty-two male rugby sevens players from the Brazilian National Olympic Team (Rio-2016) performed vertical jumping tests (squat and countermovement jumps [SJ and CMJ]), JS and HS exercises, COD speed test and sprinting velocity in 40 m, in this order. Based on the results of the MPP in the JS and HS exercises the participants were divided, using the median split, into four groups as follows: higher JS, lower JS, higher HS, and lower HS. Between-group differences in the functional tasks were detected via magnitude-based inferences. The athletes with higher MPP in the JS were capable of jumping higher and sprinting faster (including the COD speed test) than their weaker counterparts. This pattern was not observed in the HS exercise. To conclude, JS was shown to be more connected to sprinting, COD speed and jumping abilities than HS in elite rugby sevens players and should be preferred for assessing and possibly training elite athletes needing to improve speed-power related abilities. [ABSTRACT FROM AUTHOR]

Purpose: To compare the effect of 4-week unknown vs known loads strength training intervention on power output performance and throwing velocity in junior team handball players. Methods: Twenty-eight junior team-handball players (17.2 ± 0.6 years, 1.79 ± 0.07 m, 75.6 ± 9.4 kg)were divided into two groups (unknown loads: UL; known loads: KL). Both groups performed two sessions weekly consisting of four sets of six repetitions of the bench press throw exercise, using the 30%, 50% and 70% of subjects’ individual 1 repetition maximum (1RM). In each set, two repetitions with each load were performed, but the order of the loads was randomised. In the KL group, researchers told the subjects the load to mobilise prior each repetition, while in the UL group, researchers did not provide any information. Maximal dynamic strength (1RM bench press), power output (with 30, 50 and 70% of 1RM) and throwing velocity (7 m standing throw and 9 m jumping throw) were assessed pre- and post-training intervention. Results: Both UL and KL group improved similarly their 1RM bench press as well as mean and peak power with all loads. There were significant improvements in power developed in all the early time intervals measured (150 ms) with the three loads (30, 50, 70% 1RM) in the UL group, while KL only improved with 30% 1RM (all the time intervals) and with 70% 1RM (at certain time intervals). Only the UL group improved throwing velocity in both standing (4.7%) and jumping (5.3%) throw (p > 0.05). Conclusions: The use of unknown loads has led to greater gains in power output in the early time intervals as well as to increases in throwing velocity compared with known loads. Therefore unknown loads are of significant practical use to increase both strength and in-field performance in a short period of training. [ABSTRACT FROM AUTHOR]