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1.
2.
Alen Hajnal Sergio Fonseca Jeffrey M. Kinsella-Shaw Paula Silva Claudia Carello M.T. Turvey 《Neuroscience letters》2007
Nonvisual perceptions of a wielded object's spatial properties are based on the quantities expressing the object's mass distribution, quantities that are invariant during the wielding. The mechanoreceptors underlying the kind of haptic perception involved in wielding – referred to as effortful, kinesthetic, or dynamic touch – are those embedded in the muscles, tendons, and ligaments. The present experiment's focus was the selectivity of this muscle-based form of haptic perception. For an occluded rod grasped by the hand at some intermediate position along its length, participants can attend to and report selectively the rod's full length, its partial lengths (fore or aft of the hand), and the position of the grip. The present experiment evaluated whether participants could similarly attend selectively when wielding by foot. For a given rod attached to and wielded by foot or attached to (i.e. grasped) and wielded by hand, participants reported (by magnitude production) the rod's whole length or fractional length leftward of the point of attachment. On measures of mean perceived length, accuracy, and reliability, the degree of differentiation of partial from full extent achieved by means of the foot matched that achieved by means of the hand. Despite their neural, anatomical, and experiential differences, the lower and upper limbs seem to abide by the same principles of selective muscle-based perception and seem to express this perceptual function with equal facility. 相似文献
3.
K. Hkkinen W. J. Kraemer R. U. Newton M. Alen 《Acta physiologica (Oxford, England)》2001,171(1):51-62
The effects of a 6‐month resistance training (2 day/week) designed to develop both strength and power on neural activation by electromyographic activity (EMG) of the agonist and antagonist knee extensors, muscle fibre proportion and areas of type I, IIa, and IIb of the vastus lateralis (VL) as well as maximal concentric one repetition maximum (1 RM) strength and maximal and explosive isometric strength of the knee extensors were examined. A total of 10 middle‐aged men (M40; 42 ± 2), 11 middle‐aged women (W40; 39 ± 3), 11 elderly men (M70; 72 ± 3) and 10 elderly women (W70; 67 ± 3) served as subjects. Maximal and explosive strength values remained unaltered during a 1‐month control period. After the 6‐month training maximal isometric and 1RM strength values increased in M40 by 28 ± 14 and 27 ± 7% (P < 0.001), in M70 by 27 ± 17 and 21 ± 9% (P < 0.001), in W40 by 27 ± 19 and 35 ± 14% (P < 0.001) and in W70 by 26 ± 14 and 31 ± 14% (P < 0.001), respectively. Explosive strength improved in M40 by 21 ± 41% (P < 0.05), in M70 by 21 ± 24% (P < 0.05), in W40 by 32 ± 45% (NS) and in W70 by 22 ± 28% (P < 0.05). The iEMGs of the VL and vastus medialis (VM) muscles increased during the training in M40 (P < 0.001 and 0.05), in M70 (P < 0.001 and 0.05), in W40 (P < 0.001 and 0.05) and in W70 (P < 0.001 and 0.05). The antagonist biceps femoris (BF) activity during the isometric knee extension remained unaltered in M40, in W40, and in M70 but decreased in W70 (from 42 ± 34 to 32 ± 26%; P < 0.05) during the first 2 months of training. Significant increases occurred during the training in the mean fibre areas of type I in W70 (P < 0.05) and of overall type II along with a specific increase in IIa in both W40 (P < 0.05) and in W70 (P < 0.05), while the changes in the male groups were not statistically significant. The individual percentage values for type II fibres at pretraining correlated with the individual values for 1 RM strength in both W70 (r=0.80; P < 0.05) and M70 (r=0.61; P < 0.05) and also at post‐training for maximal isometric torque in W70 (r=0.77, P < 0.05). The findings support the concept of the important role of neural adaptations in strength and power development in middle‐aged and older men and women. The muscle fibre distribution (percentage type II fibres) seems to be an important contributor on muscle strength in older people, especially older women. Women of both age groups appear to be hypertrophically responsive to the total body strength training protocol performed two times a week including heavier and lower (for fast movements) loads designed for both maximal strength and power development, while such a programme has limited effects on muscle hypertrophy in men. 相似文献
4.
Neuromuscular adaptations during concurrent strength and endurance training versus strength training 总被引:5,自引:0,他引:5
Häkkinen K Alen M Kraemer WJ Gorostiaga E Izquierdo M Rusko H Mikkola J Häkkinen A Valkeinen H Kaarakainen E Romu S Erola V Ahtiainen J Paavolainen L 《European journal of applied physiology》2003,89(1):42-52
The purpose of this study was to investigate effects of concurrent strength and endurance training (SE) (2 plus 2 days a week)
versus strength training only (S) (2 days a week) in men [SE: n=11; 38 (5) years, S: n=16; 37 (5) years] over a training period of 21 weeks. The resistance training program addressed both maximal and explosive
strength components. EMG, maximal isometric force, 1 RM strength, and rate of force development (RFD) of the leg extensors,
muscle cross-sectional area (CSA) of the quadriceps femoris (QF) throughout the lengths of 4/15–12/15 (L
f) of the femur, muscle fibre proportion and areas of types I, IIa, and IIb of the vastus lateralis (VL), and maximal oxygen
uptake (V˙O2max) were evaluated. No changes occurred in strength during the 1-week control period, while after the 21-week training period
increases of 21% (p<0.001) and 22% (p<0.001), and of 22% (p<0.001) and 21% (p<0.001) took place in the 1RM load and maximal isometric force in S and SE, respectively. Increases of 26% (p<0.05) and 29% (p<0.001) occurred in the maximum iEMG of the VL in S and SE, respectively. The CSA of the QF increased throughout the length
of the QF (from 4/15 to 12/15 L
f) both in S (p<0.05–0.001) and SE (p<0.01–0.001). The mean fibre areas of types I, IIa and IIb increased after the training both in S (p<0.05 and 0.01) and SE (p<0.05 and p<0.01). S showed an increase in RFD (p<0.01), while no change occurred in SE. The average iEMG of the VL during the first 500 ms of the rapid isometric action increased
(p<0.05–0.001) only in S. V˙O2max increased by 18.5% (p<0.001) in SE. The present data do not support the concept of the universal nature of the interference effect in strength
development and muscle hypertrophy when strength training is performed concurrently with endurance training, and the training
volume is diluted by a longer period of time with a low frequency of training. However, the present results suggest that even
the low-frequency concurrent strength and endurance training leads to interference in explosive strength development mediated
in part by the limitations of rapid voluntary neural activation of the trained muscles.
Electronic Publication 相似文献
5.
Neuromuscular adaptation during prolonged strength training, detraining and re-strength-training in middle-aged and elderly people 总被引:6,自引:0,他引:6
Häkkinen K Alen M Kallinen M Newton RU Kraemer WJ 《European journal of applied physiology》2000,83(1):51-62
Effects of a 24-week strength training performed twice weekly (24 ST) (combined with explosive exercises) followed by either
a 3-week detraining (3 DT) and a 21-week re-strength-training (21 RST) (experiment A) or by a 24-week detraining (24 DT) (experiment
B) on neural activation of the agonist and antagonist leg extensors, muscle cross-sectional area (CSA) of the quadriceps femoris,
maximal isometric and one repetition maximum (1-RM) strength and jumping (J) and walking (W) performances were examined. A
group of middle-aged (M, 37–44 years, n=12) and elderly (E, 62–77, n=10) and another group of M (35–45, n=7) and E (63–78, n=7) served as subjects. In experiment A, the 1-RM increased substantially during 24 ST in M (27%, P < 0.001) and E (29%, P < 0.001) and in experiment B in M (29%, P < 0.001) and E (23%, P < 0.01). During 21 RST the 1-RM was increased by 5% at week 48 (P < 0.01) in M and 3% at week 41 in E (n.s., but P < 0.05 at week 34). In experiment A the integrated electromyogram (IEMG) of the vastus muscles in the 1-RM increased during
24 ST in both M (P < 0.05) and E (P < 0.001) and during 21 RST in M for the right (P < 0.05) and in E for both legs (P < 0.05). The biceps femoris co-activation during the 1-RM leg extension decreased during the first 8-week training in M (from
29 ± 5% to 25 ± 3%, n.s.) and especially in E (from 41 ± 11% to 32 ± 9%, P < 0.05). The CSA increased by 7% in M (P < 0.05) and by 7% in E (P < 0.001), and by 7% (n.s.) in M and by 3% in E (n.s.) during 24 ST periods. Increases of 18% (P < 0.001) and 12% (P < 0.05) in M and 22% (P < 0.001) and 26% (P < 0.05) in E occurred in J. W speed increased (P < 0.05) in both age groups. The only decrease during 3 DT was in maximal isometric force in M by 6% (P < 0.05) and by 4% (n.s.) in E. During 24 DT the CSA decreased in both age groups (P < 0.01), the 1-RM decreased by 6% (P < 0.05) in M and by 4% (P < 0.05) in E and isometric force by 12% (P < 0.001) in M and by 9% (P < 0.05) in E, respectively, while J and W remained unaltered. The strength gains were accompanied by increased maximal voluntary
neural activation of the agonists in both age groups with reduced antagonist co-activation in the elderly during the initial
training phases. Neural adaptation seemed to play a greater role than muscle hypertrophy. Short-term detraining led to only
minor changes, while prolonged detraining resulted in muscle atrophy and decreased voluntary strength, but explosive jumping
and walking actions in both age groups appeared to remain elevated for quite a long time by compensatory types of physical
activities when performed on a regular basis.
Accepted: 2 May 2000 相似文献
6.
Jeffrey B. Wagman Alen Hajnal 《Experimental brain research. Experimentelle Hirnforschung. Expérimentation cérébrale》2014,232(11):3591-3599
Behavior is typically organized in terms of a goal one intends to achieve rather than in terms of the anatomical components used in doing so. Similarly, perceptual behavior is typically organized in terms of a property one intends to perceive rather than in terms of the anatomical components used in doing so. Such task-specificity and anatomical independence are manifest in perception of properties of wielded objects. We investigated whether these properties are also manifest in perception of properties by means of wielded objects. Blindfolded participants explored an inclined surface with a rod attached to their preferred or non-preferred foot and reported whether they would be able to stand on that surface. Perception reflected action capabilities, but was unaffected by foot used, highlighting the haptic system as a smart perceptual device. 相似文献
7.
8.
Sarah T. Menacho Ramesh Grandhi Alen Delic Mohammad Anadani Wendy C. Ziai Issam A. Awad Daniel F. Hanley Adam de Havenon 《Journal of stroke and cerebrovascular diseases》2021,30(3):105540
Objectives: Intracranial pressure (ICP) monitors have been used in some patients with spontaneous intracranial hemorrhage (ICH) to provide information to guide treatment without clear evidence for its use in this population. We assessed the impact of ICP monitor placement, including external ventricular drains and intraparenchymal monitors, on neurologic outcome in this population.Materials and MethodsIn this secondary analysis of the Minimally Invasive Surgery Plus Alteplase for Intracerebral Hemorrhage Evacuation III trial, the primary outcome was poor outcome (modified Rankin Scale score 4-6) and the secondary outcome was death, at 1 year from onset. We compared outcomes in patients with or without an ICP monitor using unadjusted and adjusted logistic regression models. The analyses were repeated in a balanced cohort created with propensity score matching.ResultsSeventy patients underwent ICP monitor placement and 424 did not. Poor outcome was seen in 77.1% of patients in the ICP-monitor subgroup compared with 53.8% in the no-monitor subgroup (p<0.001). Of patients in the ICP-monitor subgroup, 31.4% died, compared with 21.0% in the no-monitor subgroup (p=0.053). In multivariate models, ICP monitor placement was associated with a >2-fold greater risk of poor outcome (odds ratio 2.76, 95% CI 1.30–5.85, p=0.008), but not with death (p=0.652). Our findings remained consistent in the propensity score-matched cohort.ConclusionThese results question whether ICP monitor–guided therapy in patients with spontaneous nontraumatic ICH improves outcome. Further work is required to define the causal pathway and improve identification of patients that might benefit from invasive ICP monitoring. 相似文献
9.
Qin Wang Decai Chen Shu Mei Cheng Patrick Nicholson Markku Alen Sulin Cheng 《Journal of bone and mineral research》2015,30(3):528-534
Osteoporotic hip fracture is a serious clinical event associated with high morbidity and mortality. Understanding femoral growth patterns is important for promoting bone health in the young and preventing fractures in later life. In this study, growth patterns of areal bone mineral density (aBMD) and geometric properties of the proximal femur were measured by dual‐energy X‐ray absorptiometry. They were studied in 251 girls from premenarche (11.2 ± 0.7 years) to late adolescence (18.3 ± 1.1 years) and compared with their premenopausal mothers (n = 128, aged 44.9 ± 4.1 years) and postmenopausal grandmothers (n = 128, aged 70.0 ± 6.3 years). Hip axis length (HAL) was the first to reach peak growth velocity (?10.5 months before menarche), followed by neck diameter (ND) and neck cross‐sectional area (CSA), (?7.1 and ?4.1 months before menarche, respectively). Both neck‐shaft angle (NSA) and aBMD of neck and total hip peaked at menarche. At 18 years (7‐year follow‐up), girls already had higher femoral neck aBMD but similar HAL and NSA compared with their mothers. Grandmothers had the longest HAL, narrowest NSA, widest ND but lowest aBMD and CSA. Hip strength index (HSI), an index of femoral neck strength during a fall, dropped rapidly after menarche in girls but thereafter remained relatively constant. Grandmothers had lower HSI than either mothers or girls. In conclusion, differences in proximal femoral bone mass and structure in adulthood are largely established before menarche, indicating that heritable factors are responsible for most of the individual variance. The development of geometric properties precedes aBMD in puberty, resulting in relatively constant hip strength after menarche. This asynchronous growth leads to adaptation of bone strength to the imposed loads, avoiding fractures in a biologically efficient manner. Both deterioration of aBMD and inadequate compensatory change in bone geometry after menopause contribute to the increased fracture risk later in life. © 2014 American Society for Bone and Mineral Research. 相似文献
10.
Neven LJubi?i? ?eljko Puljiz Ivan Budimir Alen Bi??anin Andre Bratani? Tajana Pavi? Marko Nikoli? Davor Hrabar Vladimir Supanc 《Digestive diseases and sciences》2012,57(12):3195-3204