Search results for "Biomekaniikka"
showing 10 items of 125 documents
Self-selected running gait modifications reduce acute impact loading, awkwardness, and effort
2021
Impact loading has been associated with running-related injuries, and gait retraining has been suggested as a means of reducing impact loading and lowering the risk of injury. However, gait retraining can lead to increased perceived awkwardness and effort. The influence of specifically trained and self-selected running gait modifications on acute impact loading, perceived awkwardness and effort is currently unclear. Sixteen habitual rearfoot/midfoot runners performed forefoot strike pattern, increased step rate, anterior trunk lean and self-selected running gait modifications on an instrumented treadmill based on real-time biofeedback. Impact loading, perceived awkwardness and effort scores…
Motor unit activation and force production during eccentric, concentric and isometric actions
2002
The aim of the present series of studies is to examine force and myoelectrical activity in human forearm flexors and knee extensors during dynamic and isometric muscle actions. The main purposes are 1) to clarify the methodological issues regarding the measurements of maximal force, EMG and EMG power spectrum in eccentric, concentric and isometric conditions, 2) to examine the motor unit activation patterns during dynamic and isometric actions by following the behavior of the EMG power spectrum and by utilizing selective intramuscular fine wire electrodes, and 3) to examine the effects of fatigue on force production, aEMG and EMG power spectrum in eccentric and concentric actions.
Factors related to excessive patellofemoral loading in rearfoot running
2015
Running is recognized as one of the most popular exercise methods. Furthermore, running related injuries have been under the scope for the last few decades. Synchronous function between the segments of the lower limbs is necessary for efficient locomotion. Patellofemoral pain syndrome is a common exercise related syndrome and multifactorial in nature. The purpose of this study was to measure contact forces and frontal plane moments to detect the factors that are associated with atypically high patellofemoral joint loading in rearfoot striking (RFS) running pattern, and moreover, which could possibly contribute to development of the patellofemoral pain syndrome. 39 team sport female athletes…
Non-uniformity of displacement and strain within the Achilles tendon is affected by joint angle configuration and differential muscle loading.
2020
Although the Achilles tendon (AT) has been studied for more than a century, a complete understanding of the mechanical and functional consequences of AT structural organization is currently lacking. The aim of this study was to assess how joint angle configuration affects subtendon displacement and strain of soleus (SOL) and lateral gastrocnemius (LG) muscles. Knots sutured onto SOL and LG subtendons of 12 Wistar rats, were videotaped to quantify displacements and the ankle torque was assessed for different isometric activation conditions (i.e., individual and simultaneous) of the triceps surae muscles. Changing ankle and knee joint angle affected the magnitude of displacement, relative dis…
Contribution and effectiveness of ski and pole forces in selected roller skiing techniques on treadmill at moderate inclines
2023
BackgroundMost of the studies about the effects of incline on cross-country skiing are related to the metabolic efficiency. The effective skiing biomechanics has also been indicated to be among the key factors that may promote good performance. The aims of this study were to provide biomechanical characteristics and investigate the relative contribution and effectiveness of ski and pole forces in overcoming the total external resistance with double poling (DP) and Gear 3 (G3) techniques at varying moderate uphill inclines.Methods10 male cross-country skiers participated in this study. Custom-made force measurement bindings, pole force sensors, and an 8-camera Vicon system were used to colle…
Propulsion Calculated by Force and Displacement of Center of Mass in Treadmill Cross-Country Skiing
2022
This study evaluated two approaches for estimating the total propulsive force on a skier’s center of mass (COM) with double-poling (DP) and V2-skating (V2) skiing techniques. We also assessed the accuracy and the stability of each approach by changing the speed and the incline of the treadmill. A total of 10 cross-country skiers participated in this study. Force measurement bindings, pole force sensors, and an eight-camera Vicon system were used for data collection. The coefficient of multiple correlation (CMC) was calculated to evaluate the similarity between the force curves. Mean absolute force differences between the estimated values and the reference value were computed to evalua…
Optimal inter-stimulus interval for interpolated twitch technique when using double pulse stimulation
2013
Interpolated twitch technique is a method frequently used to assess voluntary activa- tion. This method uses electrically evoked twitch superimposed on the voluntary activi- ty and its comparison with the twitch in rested muscle i.e. control twitch, to evaluate completeness of muscle activation. The purpose of this study was to investigate the ef- fect of interval in paired stimulation on control twitch in young and elderly individuals with bent and flexed knee positions. Supramaximal electrical stimulation consisted of one single stimulus and eight paired stimulation with intervals from 5 to 40ms, with increments of 5ms. In evoked twitches normalized peak torque amplitude (NPT), time to pe…
A Comparison of Methodological Approaches to Measuring Cycling Mechanical Efficiency
2019
Background: Much is known about theoretical bases of different mechanical efficiency indices and effects of physiological and biomechanical factors to them. However, there are only a few studies available about practical bases and interactions between these efficiency indices, which were the aims of the present study. Methods: Fourteen physically active men (n = 12) and women (n = 2) participated in this study. From the incremental test, six different mechanical efficiency indices were calculated for cycling work: gross (GE) and net (NE) efficiencies, two work efficiencies (WE), and economy (T) at 150 W, and in addition delta efficiency (DE) using 3–5 observation points. Results: It was fou…
Estrogeenitason vaikutus lihasaktivaation jälkeiseen voimantuoton potentoitumiseen
2017
Ikääntymisen myötä luustolihaksen toiminta muuttuu ja lihasmassa vähenee. Ikääntymisen vaikutukset eroavat naisten ja miesten välillä. Estrogeenituotannon vähenemistä pidetään eräänä osatekijänä naisten suorituskyvyn laskun kiihtymiselle, joka ajoittuu vaihdevuosien yhteyteen. Vaikka estrogeenin vaikutusmekanismia lihasten toiminnassa ei tunnetakaan kovin hyvin, on viitteitä, että estrogeenin vaikutus kohdistuu myosiinimolekyylin fosforylaatioon. Myosiinifosforylaatiolla on merkittävä rooli lihasaktivaation jälkeisessä voimantuoton potentoitumisessa (PAP). PAP:lla tarkoitetaan ilmiötä, jossa lihaksen aiempi supistus vaikuttaa lihaksen voimantuottoon. Tämän tutkimuksen tarkoituksena oli selv…
Sagittal Plane Hip, Knee, and Ankle Biomechanics and the Risk of Anterior Cruciate Ligament Injury: A Prospective Study
2018
Background: Stiff landings with less knee flexion and high vertical ground-reaction forces have been shown to be associated with an increased risk of anterior cruciate ligament (ACL) injury. The literature on the association between other sagittal plane measures and the risk of ACL injuries with a prospective study design is lacking. Purpose: To investigate the relationship between selected sagittal plane hip, knee, and ankle biomechanics and the risk of ACL injury in young female team-sport athletes. Study Design: Case-control study; Level of evidence, 3. Methods: A total of 171 female basketball and floorball athletes (age range, 12-21 years) participated in a vertical drop jump test usin…