External mechanical work in the galloping racehorse.

Horse locomotion is remarkably economical. Here, we measure external mechanical work of the galloping horse and relate it to published measurements of metabolic cost. Seven Thoroughbred horses were galloped (ridden) over force plates, under a racing surface. Twenty-six full strides of force data were recorded and used to calculate the external mechanical work of galloping. The mean sum of decrements of mechanical energy was -876 J (±280 J) per stride and increments were 2163 J (±538 J) per stride as horses were accelerating. Combination with published values for internal work and metabolic costs for galloping yields an apparent muscular efficiency of 37-46% for galloping, which would be reduced by energy storage in leg tendons. Knowledge about external work of galloping provides further insight into the mechanics of galloping from both an evolutionary and performance standpoint.

Short-interval intracortical inhibition to the biceps brachii is present during arm cycling but is not different than a position- and intensity-matched tonic contraction.

We have previously shown that supraspinal excitability is higher during arm cycling than a position- and intensity-matched tonic contraction. The present study sought to determine if short-interval intracortical inhibition (SICI) was present during arm cycling and if so, if the amount of SICI was different from an intensity-matched tonic contraction. SICI was assessed using conditioning stimuli (CS) of 70 and 90% of active motor threshold (AMT) and a test stimulus (TS) of 120% AMT at an interstimulus interval (ISI) of 2.5 ms. SICI was elicited in all participants; on average (i.e., cycling and tonic contraction grouped) test MEP amplitudes were reduced by 64.2% (p < 0.001) and 62.8% (p = 0.001) following conditioning stimuli of 70% and 90% AMT, respectively. There was no significant difference in extent of SICI between tasks (p = 0.360). These data represent the novel finding that SICI is present during arm cycling, a motor output partially mediated by spinal interneuronal networks. The amount of SICI, however, was not different from that during a position- and intensity-matched tonic contraction, suggesting that SICI is not likely a cortical mechanism contributing to higher supraspinal excitability during arm cycling compared to tonic contraction.

Intensity matters: effects of cadence and power output on corticospinal excitability during arm cycling are phase and muscle dependent.

The present study investigated the effects of cadence and power output on corticospinal excitability to the biceps (BB) and triceps brachii (TB) during arm cycling. Supraspinal and spinal excitability were assessed using transcranial magnetic stimulation (TMS) of the motor cortex and transmastoid electrical stimulation (TMES) of the corticospinal tract, respectively. Motor-evoked potentials (MEPs) elicited by TMS and cervicomedullary motor-evoked potentials (CMEPs) elicited by TMES were recorded at two positions during arm cycling corresponding to mid-elbow flexion and mid-elbow extension (i.e., 6 and 12 o'clock made relative to a clock face, respectively). Arm cycling was performed at combinations of two cadences (60 and 90 rpm) at three relative power outputs (20, 40, and 60% peak power output). At the 6 o'clock position, BB MEPs increased ~11.5% as cadence increased and up to ~57.2% as power output increased ( P < 0.05). In the TB, MEPs increased ~15.2% with cadence ( P = 0.013) but were not affected by power output, while CMEPs increased with cadence (~16.3%) and power output (up to ~19.1%, P < 0.05). At the 12 o'clock position, BB MEPs increased ~26.8% as cadence increased and up to ~96.1% as power output increased ( P < 0.05), while CMEPs decreased ~29.7% with cadence ( P = 0.013) and did not change with power output ( P = 0.851). In contrast, TB MEPs were not different with cadence or power output, while CMEPs increased ~12.8% with cadence and up to ~23.1% with power output ( P < 0.05). These data suggest that the "type" of intensity differentially modulates supraspinal and spinal excitability in a manner that is phase- and muscle dependent. NEW & NOTEWORTHY There is currently little information available on how changes in locomotor intensity influence excitability within the corticospinal pathway. This study investigated the effects of arm cycling intensity (i.e., alterations in cadence and power output) on corticospinal excitability projecting to the biceps and triceps brachii during arm cycling. We demonstrate that corticospinal excitability is modulated differentially by cadence and power output and that these modulations are dependent on the phase and the muscle examined.

Pain pressure threshold of a muscle tender spot increases following local and non-local rolling massage.

BACKGROUND: The aim of the present study was to determine the acute effect of rolling massage on pressure pain threshold (PPT) in individuals with tender spots in their plantar flexor muscles. METHODS: In a randomized control trial and single blinded study, tender spots were identified in 150 participants' plantar flexor muscles (gastrocnemius or soleus). Then participants were randomly assigned to one of five intervention groups (n = 30): 1) heavy rolling massage on the calf that exhibited the higher tenderness (Ipsi-R), 2) heavy rolling massage on the contralateral calf (Contra-R), 3) light stroking of the skin with roller massager on the calf that exhibited the higher tenderness (Sham), 4) manual massage on the calf that exhibited the higher tenderness (Ipsi-M) and 5) no intervention (Control). PPT was measured at 30 s and up to 15 min post-intervention via a pressure algometer. RESULTS: At 30 s post-intervention, the Ipsi-R (24 %) and Contra-R (21 %) demonstrated higher (p < 0.03) PPT values compared with Control and Sham. During 15 min post-intervention, PPT was higher (p < 0.05) following Ipsi-R (19.2 %), Contra-R (15.9 %) and Ipsi-M (10.9 %) compared with Control. There was no difference between the effects of three deep tissue massages (Ipsi-R, Ipsi-M and Contra-R) on PPT. DISCUSSION: Whereas the increased PPT following ipsilateral massage (Ipsi-R and Ipsi-M) might be attributed to the release of fibrous adhesions; the non-localized effect of rolling massage on the contralateral limb suggests that other mechanisms such as a central pain-modulatory system play a role in mediation of perceived pain following brief tissue massage. CONCLUSION: Overall, rolling massage over a tender spot reduces pain perception. TRIAL REGISTRATION: ClinicalTrials.gov ( NCT02528812 ), August 19(th), 2015.

High speed field kinematics of foot contact in elite galloping horses in training.

REASONS FOR PERFORMING STUDY: Mechanical characterisation of the high speed gallop has significant importance for animal welfare and basic biology. Kinematic parameters such as the velocity of each foot at contact can inform theories of why animals gallop, and supplant epidemiological investigation into the mechanisms of musculoskeletal injury. OBJECTIVE: To determine the velocity at which the fore and hind hooves of elite galloping horses impact the surface. METHODS: High speed videography was used to measure the horizontal and vertical velocity of the hoof immediately prior to impact, and the subsequent sink (vertical) and slip (horizontal) distances travelled by the hoof into the surface. Horse speed ranged from 11-19 m/s. In total 170 forelimb and 168 hindlimb foot falls from 89 horses were analysed. RESULTS: Horizontal and vertical hoof velocity increased with speed (P<0.001). Horizontal hoof velocity was significantly greater in the hindlimbs compared to the forelimbs (P<0.001) and was greater in the nonlead limbs compared to the lead limbs (P<0.001). Vertical hoof velocity was significantly greater in the lead limb than the nonlead limb (P<0.001). Overall, forelimbs contacted the ground with a more acute velocity vector angle than hindlimbs (P<0.001). Lead limbs contacted the ground at more acute angles than nonlead limbs (P<0.001). Vertical and horizontal velocities were highly correlated to sink and slip distance. CONCLUSION: Hindlimbs impact the surface at higher velocity than forelimbs, which is likely to result in higher peak impact forces in the hindlimbs. This runs counter to the finding of lower incidence of injury in hindlimbs. POTENTIAL RELEVANCE: Explanations consistent with these findings include the hindlimbs more effectively dampening peak impact forces, or that other injury mechanisms, such as limb vibration and limb load at mid stance, play an important role in injury.

Short communication: Evaluation of supercritical fluid extraction aids for optimum extraction of nonpolar lipids from buttermilk powder.

The milk fat globule membrane, present in buttermilk, contains complex lipids such as phospholipids. Microfiltration coupled with supercritical fluid extraction (SFE) may provide a method of enriching these nutritionally valuable lipids into a novel ingredient. Therefore, SFE as a method for phospholipid enrichment needs to be optimized for lipid removal effectiveness. The role of matrix additions to the buttermilk powder for extraction efficiency was evaluated. Diatomaceous earth (biosilicates), Teflon beads, and physical vibration were tested and shown to reduce total lipid by 86, 78, and 70%, respectively. Four consecutive treatments were shown to exhaust the system; however, similar extraction efficiencies were noted for 1 treatment with biosilicate addition, 2 treatments with physical vibration, or 3 treatments with added Teflon beads. The extracted lipid material consisted of the nonpolar fraction, and protein concentration was observed to increase slightly compared with the control. Although higher lipid extraction was achieved from the powder with addition of diatomaceous earth, a removable aid is ideal for an edible product.

The influence of temperature and pressure factors in supercritical fluid extraction for optimizing nonpolar lipid extraction from buttermilk powder.

The milk fat globule membrane, readily available in buttermilk, contains complex lipids claimed to be beneficial to humans. Phospholipids, including sphingolipids, exhibit antioxidative, anticarcinogenic, and antiatherogenic properties and have essential roles in numerous cell functions. Microfiltration coupled with supercritical fluid extraction (SFE) may provide a method for removing triacylglycerols while concentrating these nutritionally valuable lipids into a novel ingredient. Therefore, SFE as a method for phospholipid concentration needs to be optimized for triacylglycerol removal in buttermilk. The SFE conditions were assessed using a general full factorial design; the experimental factors were pressure (15, 25, and 35 MPa) and temperature (40, 50, and 60 degrees C). Particularly interesting is that only triacylglycerols were removed from buttermilk powder. Little to no protein loss or aggregation was observed compared with the untreated buttermilk powder. Calculated theoretical values showed a linear increase for lipid solubility as pressure, temperature, or both were increased; however, experimental values showed nonlinearity, as an effect of temperature. In addition, the particular SFE parameters of 35 MPa and 50 degrees C displayed enhanced extraction efficiency (70% total lipid reduction).

Phospholipid enrichment in sweet and whey cream buttermilk powders using supercritical fluid extraction.

Milk fat globule membrane contains many complex lipids implicated in an assortment of biological processes. Microfiltration coupled with supercritical fluid extraction (SFE) has been shown to provide a method of concentrating these nutritionally valuable lipids into a novel ingredient. In the dairy industry there are several by-products that are rich in phospholipids (PL) such as buttermilk, whey, and whey cream. However, PL are present at low concentrations. To enrich PL in buttermilk powders, regular buttermilk and whey buttermilk (by-product of whey cream after making butter) were microfiltered and then treated with SFE after drying. The total fat, namely nonpolar lipids, in the powders was reduced by 38 to 55%, and phospholipids were concentrated by a factor of 5-fold. Characterization of the PL demonstrated specific molecular fatty amide combinations on the sphingosine (18:1) backbone of sphingomyelin with the greatest proportion being saturated; the most common were 16:0, 20:0, 21:0, 22:0, 23:0, and 24:0. Two unsaturated fatty amide chains, 23:1 and 24:1, were shown to be elevated in a whey cream buttermilk sample compared with the others. However, most unsaturated species were not as abundant.

Accuracy of the TurfTrax Racing Data System for determination of equine speed and position.

REASONS FOR PERFORMING STUDY: The speed and position data collected by TurfTrax Racing Data Limited during UK Thoroughbred racing have potential to benefit equine science and welfare. The size (the 2006 data set alone consists of 30,932 individual horse starts across 2667 races) and nature (speed and 2D position for each horse at 4 updates per second) of the data make it a unique resource for questions in equine safety, welfare, performance, and animal locomotion. OBJECTIVE: To determine the accuracy of the TurfTrax tracking system in estimating the speed and position of horses during racing. METHODS: Measurements from the TurfTrax wireless tracking system were compared with those of a survey-grade global positioning system (GPS) receiver. RESULTS: The TurfTrax system was found to give position measurements to within +/- 11 and +/- 64 cm in the fore-aft and lateral directions, respectively, averaging +/- 38 cm (interquartile range) and speed to within 0.15 m/s. POTENTIAL RELEVANCE: The data collected by the TurfTrax system are of sufficient accuracy to inform new diagnoses, training regimens and basic locomotor scientific studies. The position data can provide the precise distance, going, inclination, rate of turn and pack positioning through which each horse has raced. The speed profile can be used to examine the level of exertion, effect of training regimens and influence of racecourse features on performance. A first clinical application would be to analyse retrospectively these factors on occurrence of injury to compare with past training regimens, levels of exertion, and/or racecourse conditions.

A micromachined silicon multielectrode for multiunit recording.

A 16-channel multielectrode was used to record propagating action potentials from multiple units in the ventral nerve cord of the cricket Gryllus bimaculatus. The multielectrode was fabricated using photolithographic and bulk silicon etching techniques. The fabrication differs from standard methods in its use of deep reactive ion etching (DRIE) to form the bulk electrode structure. This technique enables the fabrication of relatively thick (>100 microm), rigid structures whose top surface can have any form of thin film electronics. The multielectrode tested in this paper consists of 16 narrow silicon bridges, 150 microm wide and 350 microm tall, spaced evenly over a centimeter, with passive rectangular gold recording sites on the top surface. The nerve cord was placed perpendicularly across the bridges. In this geometry, the nerve spans a 350 microm deep, 450 microm wide trench between each recording site, permitting adequate isolation of recording sites from each other and a platinum ground plane. Spike templates for eight neurons were formed using principle component analysis and clustering of the concatenated multichannel waveforms. Clean templates were generated from a 40 s recording of stimulus evoked activity. Conduction velocities ranged from 2.59+/-0.05 to 4.99+/-0.12 m/s. Two limitations of extracellular electrode arrays are the resolution of overlapping spikes and relation of discriminated units to known anatomy. The high density, precise positioning, and controlled impedance of recording sites achievable in microfabricated devices such as this one will aid in overcoming these limitations. The rigid devices fabricated using this process offer stable positioning of recording sites over relatively large distances (several millimeters) and are suitable for clamping or squeezing of nerve cords.

Brain responses to micro-machined silicon devices.

Micro-machined neural prosthetic devices can be designed and fabricated to permit recording and stimulation of specific sites in the nervous system. Unfortunately, the long-term use of these devices is compromised by cellular encapsulation. The goals of this study were to determine if device size, surface characteristics, or insertion method affected this response. Devices with two general designs were used. One group had chisel-shaped tips, sharp angular corners, and surface irregularities on the micrometer size scale. The second group had rounded corners, and smooth surfaces. Devices of the first group were inserted using a microprocessor-controlled inserter. Devices of the second group were inserted by hand. Comparisons were made of responses to the larger devices in the first group with devices from the second group. Responses were assessed 1 day and 1, 2, 4, 6, and 12 weeks after insertions. Tissues were immunochemically labeled for glial fibrillary acidic protein (GFAP) or vimentin to identify astrocytes, or for ED1 to identify microglia. For the second comparison devices from the first group with different cross-sectional areas were analyzed. Similar reactive responses were observed following insertion of all devices; however, the volume of tissue involved at early times, <1 week, was proportional to the cross-sectional area of the devices. Responses observed after 4 weeks were similar for all devices. Thus, the continued presence of devices promotes formation of a sheath composed partly of reactive astrocytes and microglia. Both GFAP-positive and -negative cells were adherent to all devices. These data indicate that device insertion promotes two responses-an early response that is proportional to device size and a sustained response that is independent of device size, geometry, and surface roughness. The early response may be associated with the amount of damage generated during insertion. The sustained response is more likely due to tissue-device interactions.

Speed and incline during thoroughbred horse racing: racehorse speed supports a metabolic power constraint to incline running but not to decline running.

We used a radio tracking system to examine the speed of 373 racehorses on different gradients on an undulating racecourse during 33 races, each lasting a few minutes. Horses show a speed detriment on inclines (0.68 m · s(-1) · 1% gradient(-1), r(2) = 0.97), the magnitude of which corresponds to trading off the metabolic cost (power) of height gain with the metabolic cost (power) of horizontal galloping. A similar relationship can be derived from published data for human runners. The horses, however, were also slower on the decline (-0.45 m · s(-1) · 1% gradient(-1), r(2) = 0.92). Human athletes run faster on a decline, which can be explained by the energy gained by the center of mass from height loss. This study has shown that horses go slower, which may be attributable to the anatomical simplicity of their front legs limiting weight support and stability when going downhill. These findings provide insight into limits to athletic performance in racehorses, which may be used to inform training regimens, as well as advancing knowledge from both veterinary and basic science perspectives.

Dexamethasone treatment reduces astroglia responses to inserted neuroprosthetic devices in rat neocortex.

Microfabricated neural prosthetic devices hold great potential for increasing knowledge of brain function and treating patients with lost CNS function. Time-dependent loss of brain-device communication limits long-term use of these devices. Lost CNS function is associated with reactive responses that produce an encapsulating cellular sheath. Since early reactive responses may be associated with injuries produced at the time of device insertion, for example, vascular damage and disruption of the blood-brain barrier, we tested the effectiveness of the synthetic glucocorticoid, dexamethasone, in controlling insertion- and device-associated reactive responses. Dexamethasone (200 microg/kg) was administered as subcutaneous injections for 1 or 6 days beginning on the day of device insertion. Single shank microfabricated silicon devices were inserted into pre-motor cortex of adult rats. Reactive responses were assessed by immunohistochemistry for glial fibrillary acidic protein (astrocytes), CD11b (microglia), and laminin that labeled extracellular protein deposited around the insertion site and in association with vascular elements. Data were collected by confocal microscopy imaging of 100-microm-thick tissue slices. Reactive responses in vehicle control animals were similar to non-injected control animals. Dexamethasone treatment profoundly effected early and sustained reactive responses observed 1 and 6 weeks following device insertion, respectively. Dexamethasone treatment greatly attenuated astroglia responses, while microglia and vascular responses appeared to be increased. The 6-day treatment was more effective than the single injection regime. These results suggest that anti-inflammatory agents can be used to control reactive responses around inserted neural prosthetic devices and may provide a means to insure their long-term function.