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PubMed1999

Mineralocorticoid hypertension.

Hypertension with hypokalaemia and suppression of plasma renin activity is known as mineralocorticoid hypertension. Although mineralocorticoid hypertension accounts for a small number of patients labelled as having "essential" hypertension, it is a potentially reversible cause of high blood pressure. The most common cause of mineralocorticoid hypertension is probably primary aldosteronism; controlled posture studies to measure plasma renin activity and aldosterone concentrations, followed by adrenal imaging, will ensure the differential diagnosis between an aldosterone-producing adenoma and idiopathic adrenal hyperplasia in most cases. Three monogenic forms of mineralocorticoid hypertension have been described: glucocorticoid-suppressible hyperaldosteronism, Liddle's syndrome, and apparent mineralocorticoid excess, which have provided new insights into mineralocorticoid hormone action. Many patients with mineralocorticoid-based hypertension are now known to have normal serum potassium concentrations. Until the true prevalence of primary aldosteronism and monogenic forms of mineralocorticoid hypertension are defined, a high index of suspicion is needed in every hypertensive patient. Hypertensive patients with hypokalaemia, together with those with severe hypertension or a family history of hypertension or stroke, should be screened for mineralocorticoid excess.

Algorithms↗

PubMed2002

Organization of left-right coordination in the mammalian locomotor network.

Neuronal circuits involved in left-right coordination are a fundamental feature of rhythmic locomotor movements. These circuits necessarily include commissural interneurons (CINs) that have axons crossing the midline of the spinal cord. The properties of CINs have been described in some detail in the spinal cords of a number of aquatic vertebrates including the Xenopus tadpole and the lamprey. However, their function in left-right coordination of limb movements in mammals is poorly understood. In this review we describe the present understanding of commissural pathways in the functioning of spinal cord central pattern generators (CPGs). The means by which reciprocal inhibition and integration of sensory information are maintained in swimming vertebrates is described, with similarities between the three basic populations of commissural interneurons highlighted. The subsequent section concentrates on recent evidence from mammalian limbed preparations and specifically the isolated spinal cord of the neonatal rat. Studies into the role of CPG elements during drug-induced locomotor-like activity have afforded a better understanding of the location of commissural pathways, such that it is now possible, using whole cell patch clamp, to record from anatomically defined CINs located in the rhythm-generating region of the lumbar segments. Initial results would suggest that the firing pattern of these neurons shows a greater diversity than that previously described in swimming central pattern generators. Spinal CINs play an important role in the generation of locomotor output. Increased knowledge as to their function in producing locomotion is likely to provide valuable insights into the spinal networks required for postural control and walking.

Animals↗

PubMed2001

Space flight affects magnocellular supraoptic neurons of young prepuberal rats: transient and permanent effects.

Effects of microgravity on postural control and volume of extracellular fluids as well as stress associated with space flight may affect the function of hypothalamic neurosecretory neurons. Since environmental modifications in young animals may result in permanent alterations in neuroendocrine function, the present study was designed to determine the effect of a space flight on oxytocinergic and vasopressinergic magnocellular hypothalamic neurons of prepuberal rats. Fifteen-day-old Sprague-Dawley female rats were flown aboard the Space Shuttle Columbia (STS-90, Neurolab mission, experiment 150) for 16 days. Age-matched litters remained on the ground in cages similar to those of the flight animals. Six animals from each group were killed on the day of landing and eight animals from each group were maintained under standard vivarium conditions and killed 18 weeks after landing. Several signs of enhanced transcriptional and biosynthetic activity were observed in magnocellular supraoptic neurons of flight animals on the day of landing compared to control animals. These include increased c-Fos expression, larger nucleoli and cytoplasm, and higher volume occupied in the neuronal perikaryon by mitochondriae, endoplasmic reticulum, Golgi apparatus, lysosomes and cytoplasmic inclusions known as nematosomes. In contrast, the volume occupied by neurosecretory vesicles in the supraoptic neuronal perikarya was significantly decreased in flight rats. This decrease was associated with a significant decrease in oxytocin and vasopressin immunoreactive levels, suggestive of an increased hormonal release. Vasopressin levels, cytoplasmic volume and c-Fos expression returned to control levels by 18 weeks after landing. These reversible effects were probably associated to osmotic stimuli resulting from modifications in the volume and distribution of extracellular fluids and plasma during flight and landing. However, oxytocin levels were still reduced at 18 weeks after landing in flight animals compared to controls. This indicates that space flight during prepuberal age may induce irreversible modifications in the regulation of oxytocinergic neurons, which in turn may result in permanent endocrine and behavioral impairments.

Age Factors↗

PubMedDate not supplied

Effects of intra-striatal GDNF on motor coordination and striatal electrophysiology in aged F344 rats.

The purpose of this study was to examine whether improvement in motor function could be demonstrated in old rats, and to see if GDNF affected post-synaptic DA function. Aged (20 month old) versus young rats were tested following GDNF treatment for postural control by using an inclined balance beam and a wire grip strength test. Rats were also examined electrophysiologically for spontaneous striatal cell firing rate alone and in the presence of DA receptor agonists, and histologically for the intensity of striatal TH staining, and number of DA containing nigral cells. Behavior was significantly improved in the aged animals who received central GDNF infusions, although the extent of improvement was less than what has been observed in 16-month-old rats. There was no effect of GDNF treatment in the aged animals on spontaneous firing rate in the striatum, or on the post synaptic response to locally applied D(1) and D(2) receptor family agonists. However, there was an effect of age alone on firing rate, and on the response to locally applied SKF 38393 and quinpirole. By using unbiased cell counting we observed no age-related decline in the number of TH positive cells in the substantia nigra. There was no effect of GDNF on the number of TH positive cells in the substantia nigra in either young or aged rats, although there were morphological improvements in DA neurons of the GDNF treated aged rats. These results replicate earlier studies showing an effect of age on striatal firing rate and dopamine receptor function, and suggest that the GDNF mediated improvement in behavior may be located other than post synaptically within the striatum.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

PubMed2002

Swimming behavior of larval Medaka fish under microgravity.

Fish exhibit looping and rolling behaviors when subjected to short periods of microgravity during parabolic flight. Strain-differences in the behavioral response of adult Medaka fish (Oryzias latipes) were reported previously, however, there have been few studies of larval fish behavior under microgravity. In the present study, we investigated whether microgravity affects the swimming behavior of larvae at various ages (0 to 20 days after hatching), using different strains: HNI-II, HO5, ha strain, and variety of different strains (variety). The preliminary experiments were done in the ground laboratory: the development of eyesight was examined using optokinetic response for the different strains. The visual acuity of larvae improved drastically during 20 days after hatching. Strain differences of response were noted for the development of their visual acuity. In microgravity, the results were significantly different from those of adult Medaka. The larval fish appeared to maintain their orientation, except that a few of them exhibited looping and rolling behavior. Further, most larvae swam normally with their backs turning toward the light source (dorsal light response, DLR), and the rest of them stayed with their abdomen touching the surface of the container (ventral substrate response, VSR). For larval stages, strain-differences and age-differences in behavior were observed, but less pronounced than with adult fish under microgravity. Our observations suggest that adaptability of larval fish to the gravitational change and the mechanism of their postural control in microgravity are more variable than in adult fish.

Animals↗

PubMed1997

Central vestibular networks in the guinea-pig: functional characterization in the isolated whole brain in vitro.

The isolated, in vitro whole brain of guinea-pig was used to assess some of the main physiological and pharmacological properties of the vestibulo-ocular pathways in this species. Extracellular and intracellular recordings were obtained from the vestibular, abducens and oculomotor nuclei, as well as from the abducens and oculomotor nerves, while inputs from the vestibular afferents, the visual pathways and the spinal cord were activated. The three main types of medial vestibular nucleus neurons (A, B and B+LTS), previously described on slices, were also identified in the isolated brain. They had similar membrane properties in both preparations. Eighty-five per cent of cells recorded in the vestibular nucleus responded with monosynaptic, excitatory postsynaptic potentials (latency 1.05-1.9 ms) to stimulation of the ipsilateral vestibular nerve, and were thus identified as second-order vestibular neurons. In addition, stimulation of the contralateral vestibular afferents revealed in most cases a disynaptic or trisynaptic, commissural inhibition. Second-order vestibular neurons displayed in the isolated brain a high degree of variability of their spontaneous activity, as in alert guinea-pigs. Type A neurons always exhibited a regular firing, while type B and B+LTS cells could have very irregular patterns of spontaneous discharge. Thus, type A and type B neurons might correspond, respectively, to the tonic and phasic vestibular neurons described in vivo. The regularity of spontaneous discharge was positively correlated with the amplitude of spike after hyperpolarization, and there was a trend for irregular neurons to be excited from ipsilateral vestibular afferents at shorter latencies than regular units. Synaptic activation could trigger subthreshold plateau potentials and low-threshold spikes in some of the second-order vestibular neurons. As a second step, the pharmacology of the synaptic transmission between primary vestibular afferents and second-order neurons was assessed using specific antagonists of the glutamatergic receptors. Both the synaptic field potentials and excitatory postsynaptic potentials elicited in the medial vestibular nucleus by single shock stimulation of the ipsilateral vestibular nerve were largely or, sometimes, totally blocked by 6-cyano-7-nitroquinoxaline-2,3-dione, indicating a dominating role of alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor-mediated glutamatergic transmission. The remaining component of the responses was completely or partially suppressed by DL-2-amino-5-phosphonovaleric acid in 35% of the cases, suggesting a concomitant, moderate involvement of N-methyl-D-asparate receptors. In addition, a synaptic response resistant to both antagonists, but sensitive to a zero Ca2+/high Mg(2+)-containing solution, was often observed. Finally, recordings from abducens and oculomotor complexes confirmed the existence in the guinea-pig of strong bilateral, disynaptic excitatory and inhibitory inputs from vestibular afferents to motoneurons of extraocular muscles, which contribute to generation of the vestibulo-ocular reflex. The functional integrity of vestibular-related pathways in the isolated brain was additionally checked by stimulation of the spinal cord and optic tract. Stimulation of the spinal cord evoked, in addition to antidromic responses in the vestibular nucleus, short-latency synaptic responses in both the vestibular nucleus and abducens motoneurons, suggesting possible recruitment of spinal afferents. Activation of visual pathways at the level of the optic chiasm often induced long latency responses in the various structures under study. These results demonstrate that the in vitro isolated brain can be readily used for detailed, functional studies of the neuronal networks underlying gaze and posture control.

Animals↗

PubMed2000

Experience-dependent development of spinal motor neurons.

Locomotor activity in many species undergoes pronounced alterations in early postnatal life, and environmental cues may be responsible for modifying this process. To determine how these events are reflected in the nervous system, we studied rats reared under two different conditions-the presence or absence of gravity-in which the performance of motor operations differed. We found a significant effect of rearing environment on the size and complexity of dendritic architecture of spinal motor neurons, particularly those that are likely to participate in postural control. These results provide evidence that neurons subserving motor function undergo activity-dependent maturation in early postnatal life in a manner analogous to sensory systems.

Animal Husbandry↗

PubMed2002

Consequences of a ligament injury on neuromuscular function and relevance to rehabilitation - using the anterior cruciate ligament-injured knee as model.

The purpose of this article is to survey current knowledge concerning the consequences of a ligament injury on neuromuscular function and its relevance to rehabilitation, in relation to clinical practice. Although it deals with the ACL-injured knee, these views may also apply to other joints. The effects of a ligament injury on neuromuscular function are first considered - i.e., proprioception, postural control, muscle strength, functional performance, movement and activation pattern, central mechanisms, motor control and learning. The treatment and effects of rehabilitation on neuromuscular function are then discussed. The survey is concluded by discussing the clinical significance.

Anterior Cruciate Ligament↗

PubMed2003

Neurophysiology of developing fish at altered gravity: background--facts--perspectives.

During the entire evolution of life on Earth, the phylogenetic as well as the individual development of all organisms took place under constant gravity conditions, against which they achieved specific countermeasures for compensation and adaptation. On the one side, gravity represents a factor of physical restriction, which compelled the ancestors of all extant living beings to develop basic achievements to counter the gravitational force (e.g., elements of statics like any kind of skeleton--from actin to bone--to overcome gravity enforced size limits or to keep form). On the other side, already early forms of life possibly used gravity as an appropriate cue for orientation and postural control, since it is continuously present and has a fixed direction. Due to such a thorough adaptation to the Earthly gravity vector, both orientation behaviour as well as the ontogenetic development of animals is impaired, when they have to experience altered gravity (delta g; i.e., hyper- or microgravity). On this background, it is still an open question to which extent delta g affects the normal individual development, either on the systemic level of the whole organism or on the level of individual organs or even single cells. The present review provides information on these questions, focusing on developing fish as model systems. Special emphasis is being laid on the effect of delta g on the developing brain and vestibular system, comprising investigations on behaviour and plastic reactivities of the brain and inner ear. Moreover, clues and insights into the possible basic causes of space motion sickness-phenomena (SMS; a kinetosis) are provided. Overall, the results speak in favour of the following concept: short-term altered gravity (< or = 1 day) can induce transitional aberrant behaviour due to malfunctions of the inner ear, originating from asymmetric otoliths or, generally, from a mismatch between canal and otolith afferents. The vanishing aberrant behaviour is due to a reweighing of sensory inputs and neurovestibular compensation, probably on bioelectrical basis. During long-term altered gravity (several days and more), step by step neuroplastic reactivities on molecular basis (i.e., molecular facilitation) in the brain and inner ears obviously activate feedback mechanisms between the CNS and the vestibular organs for the regain of normal behaviour. Mainly, the following areas of research with animals at altered gravity need to be addressed in the future: (1) Maintenance of animals through two complete life cycles in the space environment (developmental deficiencies?). (2) Investigation of the peripheral and central vestibular system by ground-based studies (mutants, hypergravity experiments...), focusing on plasticity in developing animals as well as in adults. (3) Investigation of the effect of microgravity during critical developmental periods (imprinting phase for graviperception?). Answers to these questions may be of crucial interest for basic gravitational research.

Animals↗

PubMed2005

Aquatic exercise for children with cerebral palsy.

Exercise for children with cerebral palsy (CP) is gaining popularity among pediatric physical therapists as an intervention choice. Exercise in water appeals to children with CP because of the unique quality of buoyancy of water that reduces joint loading and impact, and decreases the negative influences of poor balance and poor postural control. In this paper, research of land-based exercise and aquatic exercise for children with CP is reviewed. Clinically relevant considerations for aquatic exercise programming for children with CP are discussed.

Cerebral Palsy↗

PubMed1999

Shortening properties of two biochemically defined muscle fibre types of the Norway lobster Nephrops norvegicus L.

Mechanical properties of myofibrillar bundles from single chemically skinned fibres from the superficial abdominal flexor muscle of the Norway lobster Nephrops norvegicus were measured, and the protein content of these fibres was analysed by SDS-PAGE. Two slow fibre phenotypes (S1, S2) were distinguished on the basis of their myofibrillar protein assemblages. Data from 9 S1 and 8 S2 fibres obtained at similar sarcomere length demonstrate significant differences between the fibre types in maximal tension (N cm-2, S1: 10.5 +/- 3.9; S2: 3.1 +/- 0.8), in the delay of the peak of stretch activation (ms, S1: 122 +/- 18; S2: 412 +/- 202), in fibre stiffness (N cm-2 per nm half sarcomere, S1: 0.36 +/- 0.19; S2: 0.09 +/- 0.03) and in maximal shortening velocity (fibre length s-1, S1: 0.53 +/- 0.10; S2: 0.27 +/- 0.06). Furthermore, the maximal power output of the type S1 fibres was about five times larger than that of S2 fibres. The power output was maximal at lower loads in S1 fibres (relative load = 0.37 +/- 0.04) than in S2 fibres (relative load = 0.44 +/- 0.05). This study represents a comprehensive investigation of two slow muscle fibre types which are thought to be specialized for slow movements (S1 fibres) and for the postural control of the abdomen (S2 fibres).

Animals↗

PubMed2003

Morphology and monoaminergic modulation of Crustacean Hyperglycemic Hormone-like immunoreactive neurons in the lobster nervous system.

Neuronal somata located near branch points in the second thoracic nerve roots of the lobster are immunoreactive for Crustacean Hyperglycemic Hormone (CHH)-like peptides, a family of putative stress hormones. We have employed intracellular dye injection, immunostaining, and confocal imaging to observe the anatomy of these root neurons, which are morphologically diverse and dye coupled. Some root neurons contribute to neurosecretory structures at the points of exit of the root from the nerve cord. Other CNS-projecting root neurons send projections into the T5-A1 interganglionic connectives. Neurosecretory elements of the serotonin (5HT) and octopamine (OCT) systems, implicated in postural control and aggression, terminate densely in the vicinity of the second thoracic root neurons. We have confirmed by double immunostaining for 5HT and CHH-like peptides that the endings of the 5HT neurons are in close apposition to root neurons in the superficial regions of the root. We have also extended previous studies documenting electrophysiological responses of the root neurons to 5HT or OCT. Bath-applied 5HT and OCT inhibit the spontaneous bursting activity of root neurons at concentrations higher than 100 nM. The root neurons desensitize to the persistent presence of high concentrations of 5HT, but not OCT, in the bath. Nanomolar concentrations of OCT, but not 5HT have an excitatory effect on the spontaneous bursting activity of root neurons. This region of the lobster nervous system is of continuing interest, as identified neurons of three neuromodulatory systems implicated in stress and aggression converge and interact at the level of identified neurons.

Action Potentials↗

PubMed1998

Early walking in the neonatal rat: a kinematic study.

The development of the early stage of locomotion (between Postnatal Days 3 and 10) was studied in newborn rats. At this age, rats are known to perform limited locomotor activities, consisting of an inefficient nonpostural gait termed crawling. By providing appropriate olfactory stimulation, it was possible to override the pups' reluctance to walk and to discover their actual locomotor abilities. The step period decreased from 1,200 ms to 900 ms from Postnatal Days 4 to 9, showing both a regular decrease in the swing and a discontinuous decrease in the stance phase. The fore- and hindlimb periods stabilized early on an alternate pattern of coupling. The ipsilateral coupling shifted progressively from 220 degrees to 260 degrees in relation with the change in the gait pattern. In parallel with the change in timing, the newborn rats showed gradual changes in the foot position and in the interlimb spatial coordination. These results show that quadruped locomotion develops before postural control is acquired, in a continuous process as the nervous system develops.

Animals↗

PubMed2005

Movement patterns and muscular demands during posterior transfers toward an elevated surface in individuals with spinal cord injury.

STUDY DESIGN: Three-dimensional kinematic analysis and surface electromyography (EMG) of 10 male adults with complete spinal cord injury (C7 to L2). OBJECTIVE: To examine movement patterns and muscular demands in individuals with spinal cord injury (SCI) during posterior transfers. SETTING: Pathokinesiology Laboratory at a Rehabilitation Centre, Montreal, Canada. METHODS: Kinematic variables that described the positions and angular displacements of the head, trunk, shoulder and elbow were obtained by videotaping markers placed on the subject segments. EMG data were recorded for the biceps, triceps, anterior deltoid, pectoralis major, latissimus dorsi and trapezius muscles of the dominant upper extremity during posterior transfers using surface electrodes. To quantify the muscular demand, the EMG data recorded during the transfers were normalized to values obtained during maximal static contractions (EMGmax). The mean muscular demand was calculated for every muscle during the lift phase of the transfers. The lift phase was determined by pressure-sensitive contacts. RESULTS: All subjects were able to execute the posterior transfers on an even surface, whereas nine subjects completed at least one of the transfers to the elevated surface. A forward-flexion pattern at the head and trunk was observed when either one or two hands remained on the lower surface, whereas a lift strategy was seen when both hands were placed on the elevated surface. Transferring to the elevated surface with hands on the lower surface required inferior electromyographic muscular utilization ratio (EMUR) than the transfer on the even surface for all muscles. The lowest EMUR were calculated for the transfer to the elevated surface with hands on the lower surface (triceps (18%), pectoralis major (53.8%), trapezius (66%) and latissimus dorsi (24.5%)) while performing the same transfer with hands on the elevated surface generated the highest EMUR (triceps (40.2%), anterior deltoid (73.2%), trapezius (83.6%) and latissimus dorsi (55.3%)). CONCLUSIONS: Subjects presented different movement characteristics and muscular demands during the posterior transfers. It is suggested that the forward-flexion pattern improves the dynamic trunk stability and reduces the muscular demand required to transfer. High muscular demand developed when hands were positioned on the elevated surface might be due to increased postural control demands on the upper limb and reduced angular momentum.

Adult↗

PubMed2002

Complexities in ETS-domain transcription factor function and regulation: lessons from the TCF (ternary complex factor) subfamily. The Colworth Medal Lecture.

The ETS-domain transcription factor family can be divided into a series of subfamilies. Elk-1 represents the founding member of the ternary complex factor (TCF) subfamily. By focusing on the TCF subfamily, we can demonstrate the complexities that exist in the function and regulation of ETS-domain transcription factors. This article focuses on Elk-1 in detail and summarizes the functions of other TCFs. The key themes covered include the domain structure of the TCFs, the mechanisms of complex formation with serum response factor, regulation of TCFs by mitogen-activated protein kinase cascades, and transcriptional regulatory properties of the TCFs. Finally, the emerging role of the TCFs in vivo is discussed. A picture is developing indicating that, while these proteins exhibit significant sequence and functional conservation, key differences in their structure and regulation are being identified which may relate to unique functions of these proteins in vivo.

Amino Acid Sequence↗

PubMed2001

Age-related changes in rat cerebellar basket cells: a quantitative study using unbiased stereological methods.

Cortical cerebellar basket cells are stable postmitotic cells; hence, they are liable to endure age-related changes. Since the cerebellum is a vital organ for the postural control, equilibrium and motor coordination, we aimed to determine the quantitative morphological changes in those interneurons with the ageing process, using unbiased techniques. Material from the cerebellar cortex (Crus I and Crus II) was collected from female rats aged 2, 6, 9, 12, 15, 18, 21 and 24 mo (5 animals per each age group), fixed by intracardiac perfusion, and processed for transmission electron microscopy, using conventional techniques. Serial semithin sections were obtained (5 blocks from each rat), enabling the determination of the number-weighted mean nuclear volume (by the nucleator method). On ultrathin sections, 25 cell profiles from each animal were photographed. The volume density of the nucleus, ground substance, mitochondria, Golgi apparatus (Golgi) and dense bodies (DB), and the mean surface density of the rough endoplasmic reticulum (RER) were determined, by point counting, using a morphometric grid. The mean total volumes of the soma and organelles and the mean total surface area of the RER [SN (RER)] were then calculated. The results were analysed with 1-way ANOVA; posthoc pairwise comparisons of group means were performed using the Newman-Keuls test. The relation between age and each of the parameters was studied by regression analysis. Significant age-related changes were observed for the mean volumes of the soma, ground substance, Golgi, DB, and SN (RER). Positive linear trends were found for the mean volumes of the ground substance, Golgi, and DB; a negative linear trend was found for the SN (RER). These results indicate that rat cerebellar basket cells endure important age-related changes. The significant decrease in the SN (RER) may be responsible for a reduction in the rate of protein synthesis. Additionally, it may be implicated in a cascade of events leading to cell damage due to the excitotoxic activity of glutamate, which could interfere in the functioning of the complex cerebellar neuronal network.

Aging↗

PubMed2002

Deep brain stimulation of the pedunculopontine region in the normal non-human primate.

Lesions in the pedunculopontine nucleus (PPN) cause akinesia. The PPN degenerates in Parkinson's disease. Stimulation of the PPN region induces stepping movements in rats and cats. These findings suggest that the PPN may play an important role in akines ia and that stimulating it may alleviate akinesia.Therefore, we have stereotactically implanted a macroelectrode in the left PPN region in a normal macaque to investigate the effects of deep brain stimulation at different frequencies. Motor activity was recorded with an infra-red counter and behaviour videotaped. At frequencies above 45 Hz there was significantly more severe akinesia than at lower frequencies (paired t -test, n=15, P<0.005). At 100 Hz, there was gross impairment of postural control. At low frequencies (5-30 Hz), stimulation induced a 5-Hz tremor in the right arm. We conclude that stimulating the PPN region at high frequency causes akinesia, whereas low frequencies induce some positive motor effects.

Animals↗

PubMed1999

Validation of simple tests of biathlon shooting ability.

The aim of this study was to validate three simple tests of biathlon shooting abilities. Twelve expert biathletes performed visual reaction time tests adapted for the rifle in the standing (RT-S) and prone positions (RT-P), and a tremometer test adapted for the rifle in the standing position (TT-S). Six consecutive days' measurements showed an acceptable reproducibility for these tests (coefficient of variation = 1.2% for RT-S, 1.1% for RT-P and 6.5% for TT-S). A significant difference was observed between TT-S at rest and after roller skiing 2.1 km at 90 % of maximal heart rate. This finding demonstrates the sensitivity of TT-S to discriminate the effects of fatigue on postural control. Among 24 biathletes of regional to expert level, significant correlations were observed between resting RT-P and prone shooting performance after roller skiing (r2 = 0.23; p = 0.01) and between resting TT-S and shooting performance in the standing position after roller skiing (r2 = 0.68; p = 0.0001), demonstrating the specificity of these tests. From these results, we conclude that TT-S is a valid field test of biathlon shooting performance.

Adult↗