PROXIMAL AND DISTAL CONSTRAINTS REDUCE DIMENSIONALITY OF VERTICAL JUMPING TASKS

The purpose of this study was to examine motor control strategies employed to control the degrees of freedom when performing a lower limb task with constraints applied at the hip, knee and ankle. Thirty-five individuals performed vertical jumping tasks: hip flexed, no knee bend and plantar flexed. Joint moment data from hip, knee and ankle was analysed using principal component analysis (PCA). In all, PCA performed, a minimum of two and maximum of six principal components (PCs) were required to describe the movement. A proximal to distal reduction in variability was only observed for the hip flexed and no knee bend conditions. Collectively, the results suggest a reduction in the dimensionality of the movement occurs, despite the constraints imposed within each condition and would suggest dimensionality reduction and motor control strategies are a function of the task demands

INVESTIGATION OF ATM PROPULSION FORCE-TIME PROFILES USING FUNCTIONAL DATA ANALYSIS ON FRONT CRAWL SPRINT SWIMMERS

The purpose of this investigation was to assess whether characteristics of the Assisted Towing Method (ATM) propulsive force-time profiles can discriminate between elite and sub-elite male sprint swimmers. Eleven elite and seven sub-elite sprint front crawl swimmers completed the ATM protocol to capture propulsion force-time profiles. The second full stroke cycle taken from the median propulsion trial on both the right and left arms were selected and functional data analysis was used to process the trials. Functional principal components analysis (fPCA) results revealed a statistical difference between the elite and sub-elite groups (p > 0.000). Further, within the elite group profiles, a distinctive double peak was found. The double peak profile could suggest a more efficient and effective stroking ratio of active drag and propulsion within the elite group

A force profile analysis comparison between functional data analysis, statistical parametric mapping and statistical non-parametric mapping in on-water single sculling

Objectives: To examine whether the Functional Data Analysis (FDA), Statistical Parametric Mapping (SPM) and Statistical non-Parametric Mapping (SnPM) hypothesis testing techniques differ in their ability to draw inferences in the context of a single, simple experimental design. Design: The sample data used is cross-sectional (two-sample gender comparison) and evaluation of differences between statistical techniques used a combination of descriptive and qualitative assessments. Methods: FDA, SPM and SnPM t-tests were applied to sample data of twenty highly skilled male and female rowers, rowing at 32 strokes per minute in a single scull boat. Statistical differences for gender were assessed by applying two t-tests (one for each side of the boat). Results: The t-statistic values were identical for all three methods (with the FDA t-statistic presented as an absolute measure). The critical t-statistics (tcrit) were very similar between the techniques, with SPM tcrit providing a marginally higher tcrit than the FDA and SnPM tcrit values (which were identical). All techniques were successful in identifying consistent sections of the force waveform, where male and female rowers were shown to differ significantly (p < 0.05). Conclusions: This is the first study to show that FDA, SPM and SnPM t-tests provide consistent results when applied to sports biomechanics data. Though the results were similar, selection of one technique over another by applied researchers and practitioners should be based on the underlying parametric assumption of SPM, as well as contextual factors related to the type of waveform data to be analysed and the experimental research question of interest

Principal Component Analysis Reveals the Proximal to Distal Pattern in Vertical Jumping Is Governed by Two Functional Degrees of Freedom

The successful completion of motor tasks requires effective control of multiple degrees of freedom (DOF), with adaptations occurring as a function of varying performance constraints. In this study we sought to compare the emergent coordination strategies employed in vertical jumping under different task constraints [countermovement jump (CMJ) with arm swing-CMJas and no arm swing-CMJnas]. In order to achieve this, principal component analysis (PCA) was conducted on joint moment waveform data from the hip, knee and ankle. This statistical approach has the advantage of analyzing the whole movement within a time series and reduces multidimensional datasets to lower dimensions for analysis. Both individual and group analyses were conducted. For individual analysis, PCA was conducted on combined hip, knee, and ankle joint moment data for each individual across both CMJnas (thirty-eight participants), and CMJas (twenty-two participants) conditions. PCA was also performed comparing all data from each individual across CMJnas and CMJas conditions. The results revealed a maximum of three principal components (PC) explained over 90% of the variance in the data sets for both conditions and within individual and group analyses. For individual analysis, no more than 2PCs were required for both conditions. For group analysis, CMJas required 3PCs to explain over 90% of the variance within the dataset and CMJnas only required 2PCs. Reconstruction of the original NJM waveforms from the PCA output demonstrates a greater loading of hip and knee joint moments to PC1, with PC2 showing a greater loading to ankle joint moment. The reduction in dimensions of the original data shows the proximal to distal extension pattern in the sagittal plane, typical of vertical jumping tasks, is governed by only 2 functional DOF, at both a group, and individual level, rather than the typically reported 3 mechanical DOF in some forms of jumping

Task Demand Changes Motor Control Strategies in Vertical Jumping.

The purpose of this study was to examine the motor control strategies employed to control the degrees of freedom when performing a lower limb task with constraints applied at the hip, knee, and ankle. Thirty-five individuals performed vertical jumping tasks: hip flexed, no knee bend, and plantar flexed. Joint moment data from the hip, knee, and ankle were analyzed using principal component analysis (PCA). In all PCA performed, a minimum of two and maximum of six principal components (PC) were required to describe the movements. Similar reductions in dimensionality were observed in the hip flexed and no knee bend conditions (3PCs), compared to the plantar flexed condition (5PCs). A proximal to distal reduction in variability was observed for the hip flexed and no knee bend conditions but not for the plantar flexed condition. Collectively, the results suggest a reduction in the dimensionality of the movement occurs despite the constraints imposed within each condition and would suggest that dimensionality reduction and motor control strategies are a function of the task demands

"Het Nieuwe Telen" Paprika

In het Nieuwe Telen Paprika met drie schermen en gecontroleerde ventilatie is geteeld met een energie inzet voor warmte van 22.2 m3/m2 en is 30.6 kg/m2 gele paprika’s geoogst. Netto verkocht is er 30 kg/m2 waarvan 26.5 kg/m2 klasse I. De energiebesparing ten opzichte van twee excursie groepen was over het hele jaar steeds ca 0.3 m3/(m2.week). Vooral in de zomer is dit opmerkelij

PCA of waveforms and functional PCA: A primer for biomechanics.

Principal components analysis (PCA) of waveforms and functional PCA (fPCA) are statistical approaches used to explore patterns of variability in biomechanical curve data, with fPCA being an accepted statistical method grounded within the functional data analysis (FDA) statistical framework. This technical note demonstrates that PCA of waveforms is the most rudimentary form of FDA, and consequently can be rationalised within the FDA framework of statistical processes. Mathematical proofing applied demonstrations of both techniques, and an example of when fPCA may be of greater benefit to control over smoothing of functional principal components is provided using an open access motion sickness dataset. Finally, open access software is provided with this paper as means of priming the biomechanics community for using these methods as a part of future functional data explorations

Gelimiteerd CO2 en het nieuwe telen Tomaat

Verwacht wordt dat de hoeveelheid te doseren CO2 in de toekomst zal afnemen vanwege afnemende beschikbaarheid uit aardgas en vanwege maatschappelijk belang om de CO2 emissie te verlagen. Daarom is onderzocht wat de gevolgen zijn van een verlaging van de doseercapaciteit op de ontwikkeling en productie van tomaat. Met een beperkte dosering van CO2 blijkt de teelt heel goed mogelijk. Een verschil van 50% in dosering (46.2 om 23.2 kg/(m2.jaar) resulteerde in een gering verschil in productie van 1 kg/m2 (65.7 om 64.7). De besparing in CO2 komt vooral door minder ventilatie verlies bij geopende luchtramen. De blad opbouw bij beide doseerstrategiën verschilde. De fotosynthese capaciteit verschilde niet voor de twee CO2 doseerstrategieën. Om CO2 gebruik te verminderen moet zoveel worden gedoseerd als voor opname door het gewas en een klein ventilatie verlies nodig is. Een andere uitkomst van dit onderzoek is dat Komeett in uitgroeiduur duidelijk anders op temperatuur reageert dan Cappricia. Een lage etmaal temperatuur leidt bij Komeett tot een sterke toename van de uitgroeiduur

International Society of Biomechanics in Sport October Newsletter 2015

IN THIS ISSUE: Message from the President, ISBS 2015 Post Conference Report, Student Mini Research Grant Reports, ISBS Awards 2015, Call for ISBS Awards 2016, Report of Student Mentoring Program, Short Communications, ISBS Sponsors, Introducing Biomch-V, C-Motion Group Meetin