Search results for "weight-bearing"
showing 10 items of 88 documents
Grip force regulates hand impedance to optimize object stability in high impact loads
2011
Anticipatory grip force adjustments are a prime example of the predictive nature of motor control. An object held in precision grip is stabilized by fine adjustments of the grip force against changes in tangential load force arising from inertia during acceleration and deceleration. When an object is subject to sudden impact loads, prediction becomes critical as the time available for sensory feedback is very short. Here, we investigated the control of grip force when participants performed a targeted tapping task with a hand-held object. During the initial transport phase of the movement, load force varied smoothly with acceleration. In contrast, in the collision, load forces sharply incre…
Behavior of fascicles and the myotendinous junction of human medial gastrocnemius following eccentric strength training
2009
This study is the first in which measurements of thickness, fascicle angle and length, and tendon elongation were combined to examine the impact of eccentric strength training on both muscle architecture and tendinous structures. Eighteen healthy male subjects were divided into an eccentric strength training group (n = 10) and a control group (n = 8). The training program consisted of 18 sessions of eccentric exercises over a 7-week period. All subjects were tested at baseline and after the last training session. Using ultrasound imaging, the fascicle angle and length and thickness of the medial gastrocnemius (MG) were analyzed at rest (i.e., theta(p), Fl(p), and t(p), respectively), at 50%…
Axial loading and posture cues in contraction of transversus abdominis and multifidus with exercise
2020
AbstractAstronauts are at increased risk of spine injury. With a view to developing training approaches for the muscles of the spine in microgravity, this study examined the effects of axial loading and postural cues on the contraction of transversus abdominis and lumbar multifidus in supine lying using a novel exercise device (GravityFit). Thirty (18 males and 12 females) endurance-trained runners without a history of spinal pain aged 33–55 years were recruited. Magnetic resonance imaging (MRI) was performed under one rest and five exercise conditions, which involved variations in axial loading and postural cues. Whole volume of the abdominal and lumbar paraspinal muscles was imaged and tr…
Biomechanical loading in the triple jump
2000
The triple jump is a demanding field event in which a jumper must tolerate extremely high impact forces while maintaining high horizontal speed. The present study was designed to clarify the mechanical loading characteristics and the role of neuromuscular function in the triple jump. Seven national triple jumpers (4 males, 3 females) volunteered to perform 3-6 jumps. The mean best performances were 14.32+/-0.45 m and 11.90+/-0.28 m for males and females, respectively. The three longest triple jumps for each jumper were selected for final analysis. The mean contact times were 0.139 s (hop), 0.157 s (step) and 0.177 s (jump). The largest ground reaction forces were observed in the step (15.2 …
Flexible multibody simulation approach in the analysis of tibial strain during walking.
2007
Strains within the bone tissue play a major role in bone (re)modeling. These small strains can be assessed using experimental strain gage measurements, which are challenging and invasive. Further, the strain measurements are, in practise, limited to certain regions of superficial bones only, such as the anterior surface of the tibia. In this study, tibial strains occurring during walking were estimated using a numerical approach based on flexible multibody dynamics. In the introduced approach, a lower body musculoskeletal model was developed by employing motion capture data obtained from walking at a constant velocity. The motion capture data were used in inverse dynamics simulation to teac…
Effects of long-term training specificity on maximal strength and power of the upper and lower extremities in athletes from different sports
2002
Maximal concentric one repetition maximum half-squat (1RM(HS)), bench-press (1RM(BP)), power-load curves during concentric actions with loads ranging from 30% to 100% of 1RM(HS) and 1RM(BP)were examined in 70 male subjects divided into five groups: weightlifters (WL, n=11), handball players (HP, n=19), amateur road cyclists (RC, n=18), middle-distance runners (MDR, n=10) and age-matched control subjects (C, n=12). The 1RM(HS)values in WL, HP and RC were 50%, 29% and 28% greater, respectively, ( P<0.001-0.01) than those recorded for MDR and C. The half-squat average power outputs at all loads examined (from 30% to 100%) in WL and HP ( P<0.001 at 45% and 60% with HP) were higher ( P<0.05-0.00…
Reduced stretch reflex sensitivity and muscle stiffness after long-lasting stretch-shortening cycle exercise in humans
1998
It has been suggested that during repeated long-term stretch-shortening cycle (SSC) exercise the decreased neuromuscular function may result partly from alterations in stiffness regulation. Therefore, interaction between the short latency stretch-reflex component (M1) and muscle stiffness and their influences on muscle performance were investigated before and after long lasting SSC exercise. The test protocol included various jumps on a sledge ergometer. The interpretation of the sensitivity of the reflex was based on the measurements of the patellar reflexes and the M1 reflex components. The peak muscle stiffness was measured indirectly and calculated as a coefficient of the changes in the…
Soleus aponeurosis strain distribution following chronic unloading in humans: an in vivo MR phase-contrast study.
2006
The in vivo strain properties of human skeletal muscle-tendon complexes are poorly understood, particularly following chronic periods of reduced load bearing. We studied eight healthy volunteers who underwent 4 wk of unilateral lower limb suspension (ULLS) to induce chronic unloading. Before and after the ULLS, maximum isometric ankle plantar flexion torque was determined by using a magnetic resonance (MR)-compatible dynamometry. Volumes of the triceps surae muscles and strain distribution of the soleus aponeurosis and the Achilles tendon at a constant submaximal plantar flexion (20% pre-maximal voluntary contraction) were measured by using MRI and velocity-encoded, phase-contrast MRI techn…
Do palatal implants remain positionally stable under orthodontic load? A clinical radiologic study.
2009
Introduction The aim of this study was to determine the positional stability and success rate of palatally placed length-reduced temporary anchorage devices (LRTADs) (length, 4 or 6 mm). Methods Twenty-two patients (ages, 21-62 years; 14 women, 8 men) were enrolled in the study. Each received 1 LRTAD (Orthosystem, Straumann, Switzerland) placed in the midsagittal palate for multifunctional anchorage tasks. Standardized cephalograms were taken directly after implant placement and at the end of treatment to analyze any implant movements. The cephalometric tracings were superimposed on anterior nasal spine to posterior nasal spine in posterior nasal spine to analyze changes in implant angulati…
Validity of Using Velocity to Estimate Intensity in Resistance Exercises in Men and Women
2020
AbstractThis study aimed to examine the validity of using bar velocity to estimate relative load in squat and bench-press exercises for both young men and women. Twenty-five men and 25 women performed a progressive loading test up to 1-RM in the squat and bench-press exercises, which were repeated after 2-weeks. Relationships between mean propulsive velocity and%1-RM were analysed. A second-order polynomial equation for predicting the corresponding velocity of each percentage of 1-RM was developed for men (validation). This equation was then applied in women (cross-validation). Moreover, a specific equation for women was developed (validation) and was also applied in a sub-sample of women (…