Search results for "voimantuotto"
showing 10 items of 57 documents
Evidence of resistance training-induced neural adaptation in older adults
2021
The deleterious effects of aging on force production are observable from the age of 40 upwards, depending on the measure. Neural mechanisms contributing to maximum force production and rate of force development have been suggested as descending drive from supraspinal centers, spinal motoneuron excitability, and corticospinal inhibition of descending drive; all of which influence motor unit recruitment and/or firing rate. Resistance-trained Master athletes offer a good source of information regarding the inevitable effects of aging despite the countermeasure of systematic resistance-training. However, most evidence of neural adaptation is derived from longitudinal intervention studies in pre…
Changes in biomechanics of skiing at maximal velocity caused by simulated 20 km skiing race using V2 skating technique
2017
This study investigated how the fatigue caused by a 20 km simulated skating cross-country skiing race on snow affects the final spurt performance from a biomechanical perspective. Subjects performed a 100 meter maximal skiing trial before and at the end of the simulated race. Cycle characteristics, ground reaction forces from skis and poles, and muscle activity from eight muscles were recorded during each trial. Results showed that subjects were in a fatigued state after the simulated race manifested by 11.6% lower skiing speed (P < 0.01). The lower skiing speed was related to an 8.0% decrease in cycle rate (P < 0.01) whereas cycle length was slightly decreased (tendency). In temporal patte…
A test of the effort equalization hypothesis in children with cerebral palsy who have an asymmetric gait.
2022
Healthy people can walk nearly effortlessly thanks to their instinctively adaptive gait patterns that tend to minimize metabolic energy consumption. However, the economy of gait is severely impaired in many neurological disorders such as stroke or cerebral palsy (CP). Moreover, self-selected asymmetry of impaired gait does not seem to unequivocally coincide with the minimal energy cost, suggesting the presence of other adaptive origins. Here, we used hemiparetic CP gait as a model to test the hypothesis that pathological asymmetric gait patterns are chosen to equalize the relative muscle efforts between the affected and unaffected limbs. We determined the relative muscle efforts for the ank…
The Effect of Paddle Stroke Variables Measured by Trainesense SmartPaddle® on the Velocity of the Kayak
2022
(1) Background: This study aimed to compare key variables of paddle stroke measured by a commercial Trainesense SmartPaddle® against the strain-gauge shaft and investigate how these variables are associated with the velocity of the boat among national-level canoe polo players. (2) Methods: This study involved 14 Finnish national-level canoe polo players. The measurement protocol consisted of three different paddling velocities, which were performed in indoor swimming pools. The velocity of the boat was calculated based on the performance time measured with the laser photocell gate. Canoe polo equipment was used in the study and a SmartPaddle sensor was attached to the paddle blade. A strain…
Hapenkulutuksen ja reiden lihasaktiivisuuden välinen yhteys pyöräilyssä
2002
Pollari, Terhi. Hapenkulutuksen ja reiden lihasaktiivisuuden välinen yhteys pyöräilyssä. LFY.203 Johdatus omatoimiseen tutkimustyöhön —kurssin tutkielma. Liikuntabiologian laitos. Jyväskylän yliopisto. Hapenkulutuksen kasvun tietyssä harjoituksessa on monesti oletettu olevan yhteydessä lisääntyneeseen lihasaktiivisuuteen työskentelevissä lihaksissa. Vaikka täysin selvää näyttöä ei ole, uskotaan hapenkulutuksen kasvun johtuvan lisääntyneestä motoristen yksiköiden käyttöönotosta tai syttymistiheydestä tehokkaan harjoituksen aikana. Hapenkulutusta ja lihasaktiivisuutta on tutkittu polkupyöräilyssä kuormilla, jotka ovat laktaattikynnystason kummallakin puolella. Tiettävästi pyöräilyssä ei kuite…
Force Generation Profiles of Para-Nordic Sit-Skiers Representing Different Physical Impairments
2021
Abstract Purpose To biomechanically profile force generation connected to the complex role of the trunk in double poling in a representative sample of Para-Nordic sit-skiers. Methods Twelve male World Cup Para-Nordic sit-skiers (sport classes: LW10–12) were skiing on flat snow terrain at submaximal speed of 4.5 m/s (~ 73% maximum speed). 2D video (50 Hz) and pole force analyses (1000 Hz) were performed synchronously, examining angle, force and cycle characteristics to analyse the role of the trunk in generating propulsion. Results LW10–11.5 skiers lost between 21% and 4% propulsive force versus LW12 athletes only due to different geometrics of the trunk and pole angle at an equal axial pole…
Postmenopausal hormone replacement therapy modifies skeletal muscle composition and function: a study with monozygotic twin pairs
2009
We investigated whether long-term hormone replacement therapy (HRT) is associated with mobility and lower limb muscle performance and composition in postmenopausal women. Fifteen 54- to 62-yr-old monozygotic female twin pairs discordant for HRT were recruited from the Finnish Twin Cohort. Habitual (HWS) and maximal (MWS) walking speeds over 10 m, thigh muscle composition, lower body muscle power assessed as vertical jumping height, and maximal isometric hand grip and knee extension strengths were measured. Intrapair differences (IPD%) with 95% confidence intervals (CI) were calculated. The mean duration of HRT use was 6.9 ± 4.1 yr. MWS was on average 7% (0.9 to 13.1%, P = 0.019) and muscle…
Evaluating objective measures of impairment to trunk strength and control for cross-country sit skiing
2021
AbstractIn Paralympic cross-country sit skiing, athlete classification is performed by an expert panel, so it may be affected by subjectivity. An evidence-based classification is required, in which objective measures of impairment must be identified. The purposes of this study were: (i) to evaluate the reliability of 5 trunk strength measures and 18 trunk control measures developed for the purposes of classification; (ii) to rank the objective measures, according to the largest effects on performance. Using a new testing device, 14 elite sit-skiers performed two upright seated press tests and one simulated poling test to evaluate trunk strength. They were also subjected to unpredictable bal…
Neural mechanisms of bilateral deficit in maximal force production in specific groups of athletes
2016
The mechanisms of bilateral deficit (BLD) have been studied extensively, but remain obscure. Neural mechanisms have been proposed, including interhemispheric inhibition (IHI). In this study specific groups of athletes who were more likely to exhibit BLD or bilateral facilitation (BLF) were compared with controls. If IHI is truly the underlying cause of BLD it is of interest whether the nature of IHI is reflected in the magnitude of BLD. 20 male subjects (ALL) were split into three groups according to the nature of their activity: bilateral, unilateral and control. Additionally, they were split into two groups whether they exhibited BLD or BLF. Maximal unilateral (UL) and bilateral (BL) isom…
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.