Leg Shock Research Articles

Development and evaluation of a sensory panel for collecting reliable player perceptions of third-generation synthetic turf football surfaces

Perceptions of synthetic surfaces used in football can vary considerably between players, and obtaining reliable feedback is challenging. The aim of this study was to develop a suitable process and evaluate the merits of establishing a sensory panel to assess the subjective attributes of third generation synthetic turf surfaces (3G turf) used in football. Focus groups with 12 male and 13 female footballers were conducted on an outdoor 3G turf pitch to develop a common language to describe sensory feedback related to player–surface interactions. Post-session analysis revealed two main themes related to player–surface interactions: hardness and grip. These themes were broken down further into five sensory attributes (Movement Speed, Slip, Movement Confidence, Leg Shock and Give) which were investigated further in an indoor test area containing ten 3G turf surfaces with controlled surface properties. A panel consisting of 18 University footballers (11 male and 7 female) undertook a screening and training session to refine the language associated with the sensory attributes and become familiar with the testing protocol. During a final evaluation session, players were asked to discriminate between surfaces using the paired comparison method for each of the sensory attributes. Player consistency remained similar between the screening and evaluation sessions whilst the panel’s ability to discriminate between surfaces improved during the evaluation session. Sensory training can therefore be a useful approach to aid players in differentiating between surfaces and lead to a greater understanding of athlete perceptions of surface attributes.

Comparison of player perceptions to mechanical measurements of third generation synthetic turf football surfaces

Mechanical testing of synthetic turf football surfaces is considered essential to ensure player performance and safety. However, it remains unknown how well the mechanical outputs reflect player perceptions of these surfaces. The first objective of this study was to investigate the agreement between the outputs from the Rotational Traction Tester and the Advanced Artificial Athlete with player perceptions across a range of controlled third generation turf football surfaces. The second objective was to identify the modifications to the Rotational Traction Tester and the Advanced Artificial Athlete configurations and output variables that give the strongest agreement with player perceptions. An indoor test area containing ten third generation turf surfaces with controlled hardness and traction properties was constructed. Each surface was tested using the Advanced Artificial Athlete and Rotational Traction Tester in their current configuration and in several modified configurations aimed at better replicating the player–surface interaction. Using a trained panel paired comparisons technique, 18 University footballers (11 males and 7 females) identified differences in the surfaces based on four sensory attributes Movement Speed, Slip, Leg Shock and Give. Results indicated strong agreement (correlation coefficients between 0.7 and 1.0) across several Rotational Traction Tester and Advanced Artificial Athlete testing configurations and output variables with player perceptions. It is recommended that the current Rotational Traction Tester is improved through added instrumentation to allow surface stiffness to be evaluated (the rate of generation of traction resistance). It is further recommended that the Advanced Artificial Athlete adopts a new algorithm to improve the accuracy of the surface’s Vertical Deformation and Energy Restitution, and the number of drops is reduced from three to one.

Sparing of Descending Axons Rescues Interneuron Plasticity in the Lumbar Cord to Allow Adaptive Learning After Thoracic Spinal Cord Injury.

This study evaluated the role of spared axons on structural and behavioral neuroplasticity in the lumbar enlargement after a thoracic spinal cord injury (SCI). Previous work has demonstrated that recovery in the presence of spared axons after an incomplete lesion increases behavioral output after a subsequent complete spinal cord transection (TX). This suggests that spared axons direct adaptive changes in below-level neuronal networks of the lumbar cord. In response to spared fibers, we postulate that lumbar neuron networks support behavioral gains by preventing aberrant plasticity. As such, the present study measured histological and functional changes in the isolated lumbar cord after complete TX or incomplete contusion (SCI). To measure functional plasticity in the lumbar cord, we used an established instrumental learning paradigm (ILP). In this paradigm, neural circuits within isolated lumbar segments demonstrate learning by an increase in flexion duration that reduces exposure to a noxious leg shock. We employed this model using a proof-of-principle design to evaluate the role of sparing on lumbar learning and plasticity early (7 days) or late (42 days) after midthoracic SCI in a rodent model. Early after SCI or TX at 7 days, spinal learning was unattainable regardless of whether the animal recovered with or without axonal substrate. Failed learning occurred alongside measures of cell soma atrophy and aberrant dendritic spine expression within interneuron populations responsible for sensorimotor integration and learning. Alternatively, exposure of the lumbar cord to a small amount of spared axons for 6 weeks produced near-normal learning late after SCI. This coincided with greater cell soma volume and fewer aberrant dendritic spines on interneurons. Thus, an opportunity to influence activity-based learning in locomotor networks depends on spared axons limiting maladaptive plasticity. Together, this work identifies a time dependent interaction between spared axonal systems and adaptive plasticity in locomotor networks and highlights a critical window for activity-based rehabilitation.

Instrumental learning within the spinal cord: V. Evidence the behavioral deficit observed after noncontingent nociceptive stimulation reflects an intraspinal modification

Spinally transected rats given leg shock whenever one hindlimb is extended learn to maintain the leg in a flexed position, which minimizes net shock exposure. Yoked rats, that receive an equal amount of shock independent of leg position (noncontingent shock), do not exhibit an increase in flexion duration. Yoked rats also fail to learn when response contingent shock is applied to the previously shocked leg, a behavioral deficit that resembles learned helplessness. This deficit could reflect either a peripheral (e.g. muscle fatigue) or central effect. Experiment 1 showed that spinalized rats given noncontingent shock to one hind limb fail to learn when response-contingent shock is applied to the contralateral leg. Experiment 2 demonstrated that blocking the afferent input to the spinal cord, by cutting the sciatic nerve, blocked the development of the deficit. Experiment 3 found that intrathecal lidocaine has a protective effect and prevents the deficit. These findings suggest that noncontingent nociceptive stimulation induces an intraspinal modification that undermines behavioral potential.

The Influence of Midsole Cushioning on Mechanical and Hematological Responses during a Prolonged Downhill Run

The purpose of this study was to investigate the influence of midsole durometer on mechanical and hematological responses during a prolonged downhill run. Twenty-four men completed a 30-min downhill run (-12% grade) wearing either soft, medium, or hard midsole shoes. Data describing mean peak tibial acceleration (PTA), stride frequency, plasma free hemoglobin, hemoglobin concentration, hematocrit, and creatine kinase (CK) were collected. While there were no significant differences in PTA among midsole durometer shoes, PTA increased by 20% after the first 5 min of the run over all other time intervals during the run (p < .05). Hemolysis showed a 50.2% increase from prerun to postrun values (p < .05). CK increased from the prerun state to 24 hr after the run (p < .05). Downhill running, irrespective of midsole durometer, showed increased levels of leg shock, hemolysis, and muscle damage over values that are present in the literature for a level running protocol.

Long-Term Consolidation and Retention of Learning-Induced Tuning Plasticity in the Auditory Cortex of the Guinea Pig

The major goal of this study was to determine whether classical conditioning produces long-term neural consolidation of frequency tuning plasticity in the auditory cortex. Local field potentials (LFPs) were obtained from chronically implanted adult male Hartley guinea pigs that were divided into conditioning (n = 4) and sensitization control (n = 3) groups. Tuning functions were determined in awake subjects for average LFPs (∼0.4 to 36.0 kHz, −20 to 80 dB) immediately before training as well as 1 h and 1, 3, 7, and 10 days after training; sensitization subjects did not have a 10-day retention test. Conditioning consisted of a single session of 30 to 45 trials of a 6-s tone (CS, 70 dB) that was not the best frequency (BF, peak of a tuning curve), followed by a brief leg shock (US) at CS offset. Sensitization control animals received the same density of CS and US presentations unpaired. Heart rate recordings showed that the conditioning group developed conditioned bradycardia, whereas the sensitization control group did not. Local field potentials in the conditioning group, but not in the sensitization group, developed tuning plasticity. The ratio of responses to the CS frequency versus the BF were increased 1 h after training, and this increase was retained for the 10-day period of the study. Both tuning plasticity and retention were observed across stimulus levels (10–80 dB). Most noteworthy, tuning plasticity exhibited consolidation (i.e., developed greater CS-specific effects across retention periods), attaining asymptote at 3 days. The findings indicate that LFPs in the auditory cortex have three cardinal features of behavioral memory: associative tuning plasticity, long-term retention, and long-term consolidation. Potential cellular and subcellular mechanisms of LFP tuning plasticity and long-term consolidation are discussed.

Spectral Analysis of Impact Shock during Running

The purpose of this study was to determine the effects of increasing impact shock levels on the spectral characteristics of impact shock and impact shock wave attenuation in the body during treadmill running. Twelve male subjects ran at 2.0, 3.0, 4.0, and 5.0 m s−1 on a treadmill. Axial accelerations of the shank and head were measured using low-mass accelerometers. The typical shank acceleration power spectrum contained two major components which corresponded to the active (5–8 Hz) and impact (12–20 Hz) phases of the time-domain ground reaction force. Both the amplitude and frequency of leg shock transients increased with increasing running speed. Greatest attenuation of the shock transmitted to the head occurred in the 15–50 Hz range. Attenuation increased with increasing running speed. Thus transmission of the impact shock wave to the head was limited, despite large increases in impact shock at the lower extremity.

Neuronal pathways involved in transfer of information related to leg position learning in the cockroach, P. Americana

The transfer of information related to shock avoidance leg position learning was studied in cockroaches. Behavioral experiments in which a prothoracic leg was trained and a mesothoracic leg tested helped to characterize what kind of information is transferred and the gross pathways by which this transfer occurs. Anatomical experiments showed that the relevant sensory and motor neurons have their central processes confined to the ganglia of origin. Some large interneurons were characterized in the prothoracic-mesothoracic connectives and were found to have branches in both the prothoracic and mesothoracic ganglia. Electrophysiological experiments revealed that some large connective fibers carry corollary discharges of motorneuron activity—a one-to-one correspondence of spikes in the corollary units of flexor motorneurons and an approximate correspondence of spikes in the corollary units of extensor motorneurons. We hypothesize that sensory information related to prothoracic leg shock and motor information related to prothoracic leg position are independently transferred down each prothoracic-mesothoracic connective to the mesothoracic ganglion, where they are associated and lead to a behavior change in mesothoracic legs.

Attenuation of pain reactivity by caudate nucleus stimulation in monkeys

The effect of caudate nucleus stimulation on reactivity to painful was investigated in Macaca speciosa monkeys chronically implanted with electrodes in the right caudate nucleus. The force with which subjects escaped from electrocutaneous leg shock was used as a measure of pain reactivity and was decreased by caudate stimulation. Escape thresholds and latencies were not influenced by the brain stimulation. Decreased escape force was obtained only when 50 msec trains of caudate stimulation preceded 20 msec trains of leg shock by 0–100 msec. Pain reactivity was not affected if brain stimulation followed leg shock or if leg shock followed brain stimulation by more than 100 msec. Intershock response distributions indicated that direct motor inhibition was not responsible for the depression of escape force, and the effectiveness of a restricted range of caudate-leg stimulation intervals ruled out generalized effects on arousal. The results indicate that the effect of caudate stimulation is to reduce the affective components of pain elicited by noxious electrocutaneous stimuli. The time course of this caudate effect parallels that previously reported for the caudate-induced depression of evoked activity in the non-specific somatosensory projections of the reticular formation and thalamus.

Suppression of headbanging on the ward.

Effects of leg shock and a conditioned aversive stimulus (a loud, verbal “No”) on the self-injurious responses of a profoundly retarded patient were assessed. The “No” and shock produced a significant decrement in self-injurious responding. The procedure was then modified for use in the regular ward environment. The staff delivered the loud, verbal “No” contingent on each self-injurious response they observed, and occasional leg shocks. The procedure afforded clinically significant control of the patient's self-injurious behavior, but it was not possible to evaluate the long-term effectiveness of the procedure.

Behavioral assessment of pain detection and tolerance in monkeys.

Cebus albifrons monkeys received electrical stimulation of the hindlimbs over a wide range of intensities. On trials signalled by a blue light, the animals were permitted to escape shock by pressing a disc, or shock was terminated after 8 sec (free escape). Escape force (disc pressure) was found to increase as stimulation intensity increased well beyond escape threshold, while shock duration curves reached plateau at the mid-range of intensities. The shock duration curves generated by free escape responses should be comparable to pain detection functions obtained by similar operations in humans, and the curves were stable over months of testing, as is generally found in pain-detection studies. On trials signalled by a red light, the animals received intense tail shock immediately after escape responses (punished escape), or, if they endured leg shock for 8 sec without escaping, then they could avoid tail shock with a panel press. The shock duration curves generated by punished escape responses should be comparable to pain tolerance functions as defined for human subjects, and the escape thresholds were considerably higher on red-light trials. As in human studies, the tolerance curves were not stable over repeated testing sessions, and some feature of the paradigm forced a progression toward extremely high levels of tolerance.

A comparison of the pituitary adrenal activity elicited by electrical stimulation of preoptic, amygdaloid and hypothalamic sites in the rat brain.

In rats anesthetized with pentobarbital, increments in corticosterone concentration were elicited upon electrical stimulation through chronically implanted electrodes. Prestimulation steroid levels were low. Poststimulation levels varied according to the site stimulated. These sites, ranging in order of responsiveness from greatest to least, were amygdala, mammillary hypothalamus, tuberal hypothalamus, and preoptic area. The corticosterone increments obtained under anesthesia were similar in magnitude to those obtained in the absence of anesthesia. Placement of the electrodes in the median eminence itself did not enhance the responsiveness. Hind leg shock evoked a steroid increment comparable to that produced by tuberal stimulation ; and ketamine, a centrally acting drug, provided an estimate of the maximal centrally elicited response. The evidence is consistent with the view that excitatory afferent paths to corticotropin releasing factor (CRF) neurons and the CRF neurons themselves lie distributed in the tissue stimulated.

Changes in colored or flavored food preferences in chickens as a function of shock

Twenty-four two-week old chicks were first tested to determine which of two mashes, differing either in color or in taste only, was preferred; Ss were then trained such that the Experimentals received a painful leg shock when they ate their preferred food, while the Controls were either shocked in the absence of the test food or not shocked. Feeding on the nonpreferred food went undisturbed in all three groups. Several posttraining tests were given to detect any changes in colored or flavored food preferences. Electric shock proved to be an effective noxious stimulus for changing food preferences based on visual cues but not for those distinguishable by taste alone.