Search results for "Biomechanic"
showing 10 items of 706 documents
Do equilibrium constraints modulate postural reaction when viewing imbalance?
2011
Abstract Action observation and action execution are tightly coupled on a neurophysiological and a behavioral level, such that visually perceiving an action can contaminate simultaneous and subsequent action execution. More specifically, observing a model in postural disequilibrium was shown to induce an increase in observers’ body sway. Here we reciprocally questioned the role of observers’ motor system in the contagion process by comparing participants’ body sway when watching displays of antero-posterior vs. lateral imbalance. Indeed, during upright standing, biomechanical constraints differ along the antero-posterior (A-P) and medio-lateral (M-L) axes; hence an impact of observers’ post…
Neuromuscular fatigue and recovery in maximal compared to explosive strength loading.
1997
The purpose of this study was to examine acute neuromuscular fatigue and its recovery in men (n = 8) and women (n = 8). Two strenuous, but clearly different exercises were compared: maximal (MSL) versus explosive strength loading (ESL). The MSL included five sets of ten repetition maximum bilateral leg extensions. The same task and the same number of sets was performed in ESL but with 40% from the load used in MSL and performed as explosively as possible. Isometric force-time curves were measured during maximal voluntary bilateral isometric action of the leg extensors before the fatigue loading and after each set. The measurements were repeated after resting for 1 h, 2 h, 1 day and two days…
Daily hormonal and neuromuscular responses to intensive strength training in 1 week.
1988
Daily adaptive responses in the neuromuscular and endocrine systems to a 1-week very intensive strength training period with two training sessions per day were investigated in eight elite weight lifters. The morning and the afternoon sessions resulted in acute decreases (P less than 0.05-0.01) in maximal isometric strength and in the maximal neural activation (iEMG) of the leg extensor muscles, but the basic levels remained unaltered during the entire training period. Significant (P less than 0.05-0.01) acute increases in serum total and free testosterone levels were found during the afternoon sessions. During the 1-week training period, serum total and free testosterone concentrations decr…
Individual Region- and Muscle-specific Hamstring Activity at Different Running Speeds
2019
Introduction \ud Hamstring strain injuries typically occur in the proximal biceps femoris long head (BFlh) at high running speeds. Strain magnitude seems to be the primary determinant of strain injury, and may be regulated by muscle activation. In running, BFlh strain is largest in the proximal region, especially at high speeds. However, region-specific activity has not been examined. This study examined the proximal–distal and intermuscular activity of BFlh and semitendinosus (ST) as a function of increasing running speed.\ud \ud Methods \ud Thirteen participants ran at steady speeds of 4.1 (slow), 5.4 (moderate), and 6.8 m·s−1 (fast) on a treadmill. Region- and muscle-specific EMG activit…
A method for monitoring intensity during aquatic resistance exercises.
2008
The aims of this study were (i) to check whether monitoring of both the rhythm of execution and the perceived effort is a valid tool for reproducing the same intensity of effort in different sets of the same aquatic resistance exercise (ARE) and (ii) to assess whether this method allows the ARE to be put at the same intensity level as its equivalent carried out on dry land. Four healthy trained young men performed horizontal shoulder abduction and adduction (HSAb/Ad) movements in water and on dry land. Muscle activation was recorded using surface electromyography of 1 stabilizer and several agonist muscles. Before the final tests, the ARE movement cadence was established individually follow…
Influence of foot orthosis customisation on perceived comfort during running
2014
Although running is associated with many health benefits, it also exposes the body to greater risk of injury. Foot orthoses are an effective strategy to prevent such injuries. Comfort is an essential element in orthosis design since any discomfort alters the runner's biomechanics, compromising performance and increasing the risk of injury. The present study analyses the perceived comfort of three types of orthoses: custom-made, prefabricated and original running shoe insoles. Nine comfort variables for each insole were assessed in a sample of 40 runners. Custom-made and prefabricated insoles were both perceived as significantly more comfortable than the original insoles. The differences wer…
Kinematics and electromyographic activity of horse riders during various cross-country jumps in equestrian
2019
International audience; The objective of this study was to identify the key biomechanical patterns (functional muscles and kinematics) of amateur horse riders during various cross-country jumps in equestrian. Eleven riders first performed a control condition that corresponded to jumps over three different obstacles (log wall, brush and tree trunk) before jumping over the same three obstacles in a cross-country course. 3D Kinematics and electromyographic (EMG) activity was synchronously collected which included seven muscles of the riders back, lower and upper limbs. Maximum voluntary isometric strength of knee extensors was also measured before and immediately after the race to investigate …
The effect of visual focus on spatio-temporal and kinematic parameters of treadmill running
2017
The characteristics of a treadmill and the environment where it is based could influence the user’s gaze and have an effect on their running kinematics and lower limb impacts. The aim of this study was to identify the effect of visual focus on spatio-temporal parameters and lower limb kinematics during treadmill running. Twenty six experienced runners ran at 3.33 m s−1 on a treadmill under two visual conditions, either looking ahead at a wall or looking down at the treadmill visual display. Spatio-temporal parameters, impact accelerations of the head and tibia, and knee and ankle kinematics were measured for the final 15 s of a 90 s bout of running under each condition. At the end of the te…
Biomechanical Loading of Achilles Tendon During Normal Locomotion
1992
Direct in vivo Achilles tendon force measurements open up new possibilities for understanding the loading of the Achilles tendon during natural locomotion. This article describes how these human experiments can be performed. The results of these experiments imply that Achilles tendon forces are unexpectedly high in certain activities (e.g., hopping) and that the rates of loading rather than the absolute magnitudes of the recorded forces may be more relevant for clinical purposes as well as for the construction of artificial tendon materials.
Age-related differences in Achilles tendon properties and triceps surae muscle architecture in vivo
2012
This study examined the concurrent age-related differences in muscle and tendon structure and properties. Achilles tendon morphology and mechanical properties and triceps surae muscle architecture were measured from 100 subjects [33 young (24 ± 2 yr) and 67 old (75 ± 3 yr)]. Motion analysis-assisted ultrasonography was used to determine tendon stiffness, Young's modulus, and hysteresis during isometric ramp contractions. Ultrasonography was used to measure muscle architectural features and size and tendon cross-sectional area. Older participants had 17% lower ( P < 0.01) Achilles tendon stiffness and 32% lower ( P < 0.001) Young's modulus than young participants. Tendon cross-section…