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The use of remote sensing to monitor animal populations has greatly expanded during the last decade. Drones (i.e., Unoccupied Aircraft Systems or UAS) provide a cost- and time-efficient remote sensing option to survey animals in various landscapes and sampling conditions. However, drone-based surveys may also introduce counting errors, especially when monitoring mobile animals. Using an agent-based model simulation approach, we evaluated the error associated with counting a single animal across various drone flight patterns under three animal movement strategies (random, directional persistence, and biased toward a resource) among five animal speeds (2, 4, 6, 8, 10 m/s). Flight patterns represented increasing spatial independence (ranging from lawnmower pattern with image overlap to systematic point counts). Simulation results indicated that flight pattern was the most important variable influencing count accuracy, followed by the type of animal movement pattern, and then animal speed. A  awnmower pattern with 0% overlap produced the most accurate count of a solitary, moving animal on a landscape (average count of 1.1 ± 0.6) regardless of the animal's movement pattern and speed. Image overlap flight patterns were more likely to result in multiple counts even when accounting for mosaicking. Based on our simulations, we recommend using a lawnmower pattern with 0% image overlap to minimize error and augment drone efficacy for animal surveys. Our work highlights the importance of understanding interactions between animal movements and drone survey design on count accuracy to inform the development of broad applications among diverse species and ecosystems., Competing Interests: The authors have no conflict of interest., (© 2024 The Author(s). Ecology and Evolution published by John Wiley & Sons Ltd.)

Wildlife tagging provides critical insights into animal movement ecology, physiology, and behavior amid global ecosystem changes. However, the stress induced by capture, handling, and tagging can impact post-release locomotion and activity and, consequently, the interpretation of study results. Here, we analyze post-tagging effects on 1585 individuals of 42 terrestrial mammal species using collar-collected GPS and accelerometer data. Species-specific displacements and overall dynamic body acceleration, as a proxy for activity, were assessed over 20 days post-release to quantify disturbance intensity, recovery duration, and speed. Differences were evaluated, considering species-specific traits and the human footprint of the study region. Over 70% of the analyzed species exhibited significant behavioral changes following collaring events. Herbivores traveled farther with variable activity reactions, while omnivores and carnivores were initially less active and mobile. Recovery duration proved brief, with alterations diminishing within 4-7 tracking days for most species. Herbivores, particularly males, showed quicker displacement recovery (4 days) but slower activity recovery (7 days). Individuals in high human footprint areas displayed faster recovery, indicating adaptation to human disturbance. Our findings emphasize the necessity of extending tracking periods beyond 1 week and particular caution in remote study areas or herbivore-focused research, specifically in smaller mammals., (© 2024. The Author(s).)

Accelerometers worn by animals produce distinct behavioral signatures, which can be classified accurately using machine learning methods such as random forest decision trees. The objective of this study was to identify accelerometer signal separation among parsimonious behaviors. We achieved this objective by (1) describing functional differences in accelerometer signals among discrete behaviors, (2) identifying the optimal window size for signal pre-processing, and (3) demonstrating the number of observations required to achieve the desired level of model accuracy,. Crossbred steers (Bos taurus indicus; n = 10) were fitted with GPS collars containing a video camera and tri-axial accelerometers (read-rate = 40 Hz). Distinct behaviors from accelerometer signals, particularly for grazing, were apparent because of the head-down posture. Increasing the smoothing window size to 10 s improved classification accuracy ( p < 0.05), but reducing the number of observations below 50% resulted in a decrease in accuracy for all behaviors ( p < 0.05). In-pasture observation increased accuracy and precision (0.05 and 0.08 percent, respectively) compared with animal-borne collar video observations.

Background: The wild pig (Sus scrofa) is an exotic species that has been present in the southeastern United States for centuries yet continues to expand into new areas dominated by bottomland and upland forests, the latter of which are less commonly associated with wild pigs. Here, we aimed to investigate wild pig movement and space use attributes typically used to guide wild pig management among multiple spatiotemporal scales. Our investigation focused on a newly invaded landscape dominated by bottomland and upland forests., Methods: We examined (1) core and total space use using an autocorrelated kernel density estimator; (2) resource selection patterns and hot spots of space use in relation to various landscape features using step-selection analysis; and (3) daily and hourly differences in movement patterns between non-hunting and hunting seasons using generalized additive mixed models., Results: Estimates of total space use among wild pigs (n = 9) were smaller at calculated core (1.2 ± 0.3 km 2 ) and 90% (5.2 ± 1.5 km 2 ) isopleths than estimates reported in other landscapes in the southeastern United States, suggesting that wild pigs were able to meet foraging, cover, and thermoregulatory needs within smaller areas. Generally, wild pigs selected areas closer to herbaceous, woody wetlands, fields, and perennial streams, creating corridors of use along these features. However, selection strength varied among individuals, reinforcing the generalist, adaptive nature of wild pigs. Wild pigs also showed a tendency to increase movement from fall to winter, possibly paralleling increases in hard mast availability. During this time, there were also increases in anthropogenic pressures (e.g. hunting), causing movements to become less diurnal as pressure increased., Conclusions: Our work demonstrates that movement patterns by exotic generalists must be understood across individuals, the breadth of landscapes they can invade, and multiple spatiotemporal scales. This improved understanding will better inform management strategies focused on curbing emerging invasions in novel landscapes, while also protecting native natural resources., (© 2024. This is a U.S. Government work and not under copyright protection in the US; foreign copyright protection may apply.)

Since 2012, control of invasive wild pigs (Sus scrofa) in the United States (US) has become a state and national priority due to their propensity to damage agricultural commodities and infrastructure, transmit disease, detrimentally affect ecological processes, and compete with native wildlife for resources. While several life-history characteristics certainly aided their proliferation, the recreational value of wild pigs was likely the stimulus for translocation and subsequent establishment of populations in ≥35 states, causing an annual economic burden of $1.5 billion in the US. Consequently, state-level legislative procedures regarding wild pigs are expanding in scope and priority, but policy among states lacks uniformity. States vary in their treatment of wild pig control based on differing resource appropriations and stakeholder interests. We conducted an evaluation to determine if policy was associated with state-level 1) presence of wild pigs, 2) spatial extent of wild pig population occupancy, and 3) trajectory of wild pig population occupancy. Our results suggest the presence of wild pigs in various states was influenced by hunting preserves and the sale of hunting opportunities. In occupied states, the spatial extent of wild pigs was again associated with the sale of hunting opportunities and a wild pig hunting culture. Finally, the trajectory of state-level wild pig spatial occupancy was positively influenced by the sale of hunting opportunities, and negatively influenced by transportation policies. Based on these findings, we propose state governments standardize transportation policy and fenced hunting regulations across regions of the US in a more prohibitive fashion to diminish range expansion through illegal and negligent introductions via transportation, release, and escapes from game farms. Moreover, in states where wild pigs have yet to establish, we strongly recommend states proactively prohibit transportation through intra- and interstate movement., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Published by Elsevier Ltd.)

Agricultural development has been causing changes to the environment and the abundance and distribution of avian species. Agriculture is dynamic with changes in products occurring at large scales over relatively short time periods. The catfish aquaculture industry is one such agriculture industry that has undergone dramatic changes over the last 25 years. The double-crested cormorant (Nannopterum auritum) is a piscivorous bird that has an extensive history with the aquaculture industry of Mississippi due to its depredation of cultured catfish. A large-scale monitoring program began in 1989 to estimate the abundance and location of cormorants at every known roost in the primary catfish producing region of the state, regionally known as the Delta. We used this data set to address hypotheses pertaining to cormorant ecology within the Delta over time, particularly in relation to aquaculture. We found that, although the Midwest breeding population of cormorants has been increasing, the abundance of cormorants wintering in the Delta has been decreasing, closely following the decline of aquaculture, suggesting aquaculture area is the primary reason for cormorant inhabitation of the region. We also modeled cormorant presence and abundance at all roost sites to determine what factors most influenced cormorant distribution. Aquaculture area around roosts was a significant predictor of both cormorant presence and abundance. However, the influence of aquaculture area was seasonally dependent, with greater positive influences occurring prior to migration. Lastly, we found peak cormorant abundance in the Delta is occurring 2.14 days earlier each year, which may be indicative of changes to migration phenology. Information gained using this large dataset aids in cormorant damage mitigation and to further our understanding of cormorant ecology. Data indicate changes in agriculture, and potentially climate change, can influence phenology, distribution, and abundance of avian species at large geographic scales., Competing Interests: The authors have declared that no competing interests exist., (Copyright: This is an open access article, free of all copyright, and may be freely reproduced, distributed, transmitted, modified, built upon, or otherwise used by anyone for any lawful purpose. The work is made available under the Creative Commons CC0 public domain dedication.)

The composition of land use/land cover (LULC) in coastal watersheds has many implications for estuarine system ecological function. Land use/land cover can influence allochthonous inputs and can enhance or degrade the physical characteristics of estuaries, which in turn affects estuaries' ability to support local biota. However, these implications for estuaries are often poorly considered when assessing the value of lands for conservation. The focus of research regarding terrestrial and estuarine interfaces often evaluates how LULC may stress estuarine ecosystems, but in this study we sought to understand how LULC may both positively and negatively affect estuaries using measures of observed biotic richness as proxies for estuarine function. We investigated the influence of LULC on estuarine biotic richness with Bayesian hierarchical models using multiple geospatial data sets from 33 estuaries and their associated watersheds along the Gulf of Mexico coastal region of the United States. We designed the hierarchical models with observed species richness of three functional groups (FGs) (i.e., pelagic fishes, forage fishes, and shrimp) from fishery-independent trawl surveys as response variables. We then set salinity and water temperature as trawl-specific covariates and measures of influence from six LULC classes as estuary-specific covariates and allowed the models to vary by estuary, trawl program, salinity, and temperature. The model results indicated that the observed richness of each FG was both positively and negatively associated with different LULC classes, with estuarine wetlands and forested lands demonstrating the strongest positive influences on each FG. The results are generally consistent with past studies, and the modeling framework provides a promising way to systematically quantify LULC linkages with the biotic health of estuaries for the purposes of potentially valuing the estuarine implications of land conservation., (© 2022 The Authors. Ecological Applications published by Wiley Periodicals LLC on behalf of The Ecological Society of America.)

Introduction: Weightbearing activities such as gymnastics, soccer, weightlifting, and running have often been used as benchmarks in skeletal research since they have been shown to promote densitometric and geometric benefits. In comparison with other sports, there is a paucity of information in relation to dance and its osteogenic potential., Objective: This study aimed to compare tibial geometry, density, and strength in college-aged dancers versus gymnasts and runners.
Methods: A total of 60 trained eumenorrheic collegiate-aged female dancers (n = 11), gymnasts (n = 11), runners (n = 19), and sedentary controls (n = 19) were included in the study. Bone measure- ments, including total area (ToA), volumetric (total vBMD) and cortical density (CoD), compressive bone strength (BSI), and polar strength stress index (SSIp) of the dominant limb, were assessed using peripheral quantitative computed tomography (pQCT) at the distal and proximal tibia (4% and 66% of limb length).
Results: No significant differences in ToA, CoD, CoA, and total vBMD were found between dancers and the comparison athletes at the measured sites. In addition, strength indices (BSI and SSIp) at the distal and proximal sites were similar between the dancing and both athlete groups.
Conclusion: Results suggest dance elicits similar structural adaptations at the tibia compared to benchmark high-impact and repetitive impact sports; thus, indicating dance, in its various forms, can have a positive effect on important bone variables that influence density and strength. These adaptations may potentially delay or prevent bone fragility later in life. Future studies should compare individual styles of dance separately, longitudinally, and include other important lower (e.g., hip) and upper body (e.g., radius) sites to further identify which forms provide the greatest osteogenic benefits.

Given climate change threats to ecosystems, it is critical to understand the responses of species to warming. This is especially important in the case of apex predators since they exhibit relatively high extinction risk, and changes to their distribution could impact predator-prey interactions that can initiate trophic cascades. Here we used a combined analysis of animal tracking, remotely sensed environmental data, habitat modeling, and capture data to evaluate the effects of climate variability and change on the distributional range and migratory phenology of an ectothermic apex predator, the tiger shark (Galeocerdo cuvier). Tiger sharks satellite tracked in the western North Atlantic between 2010 and 2019 revealed significant annual variability in the geographic extent and timing of their migrations to northern latitudes from ocean warming. Specifically, tiger shark migrations have extended farther poleward and arrival times to northern latitudes have occurred earlier in the year during periods with anomalously high sea-surface temperatures. A complementary analysis of nearly 40 years of tiger shark captures in the region revealed decadal-scale changes in the distribution and timing of shark captures in parallel with long-term ocean warming. Specifically, areas of highest catch densities have progressively increased poleward and catches have occurred earlier in the year off the North American shelf. During periods of anomalously high sea-surface temperatures, movements of tracked sharks shifted beyond spatial management zones that had been affording them protection from commercial fishing and bycatch. Taken together, these study results have implications for fisheries management, human-wildlife conflict, and ecosystem functioning., (© 2022 The Authors. Global Change Biology published by John Wiley & Sons Ltd.)

Understanding broiler behaviours provides important implications for animal well-being and farm management. The objectives of this study were to classify specific broiler behaviours by analysing data from wearable accelerometers using two machine learning models, K-Nearest Neighbour (KNN) and Support Vector Machine (SVM). Lightweight triaxial accelerometers were used to record accelerations of nine 7-week-old broilers at a sampling frequency of 40 Hz. A total of 261.6-min data were labelled for four behaviours - walking, resting, feeding and drinking. Instantaneous motion features including magnitude area, vector magnitude, movement variation, energy, and entropy were extracted and stored in a dataset which was then segmented by one of the six window lengths (1, 3, 5, 7, 10 and 20 s) with 50% overlap between consecutive windows. The mean, variation, SD, minimum and maximum of each instantaneous motion feature and two-way correlations of acceleration data were calculated within each window, yielding a total of 43 statistic features for training and testing of machine learning models. Performance of the models was evaluated using pure behaviour datasets (single behaviour type per dataset) and continuous behaviour datasets (continuous recording that involved multiple behaviour types per dataset). For pure behaviour datasets, both KNN and SVM models showed high sensitivities in classifying broiler resting (87% and 85%, respectively) and walking (99% and 99%, respectively). The accuracies of SVM were higher than KNN in differentiating feeding (88% and 75%, respectively) and drinking (83% and 62%, respectively) behaviours. Sliding window with 1-s length yielded the best performance for classifying continuous behaviour datasets. The performance of classification model generally improved as more birds were included for training. In conclusion, classification of specific broiler behaviours can be achieved by recording bird triaxial accelerations and analysing acceleration data through machine learning. Performances of different machine learning models differ in classifying specific broiler behaviours., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

Piscivorous avian species are the main source of catfish depredation at aquaculture facilities in Mississippi, resulting in the economic loss of millions of dollars every year. Most notable of these avian species are the double-crested cormorant (Phalacrocorax auritus), great blue heron (Ardea herodias), and great egret (A. alba). Understanding why these species select specific ponds can increase management efficiency directed at avian dispersal and provide insight into their decision making with respect to foraging behavior. We collected species presence data on catfish ponds by flying 35 surveys from October through April of 2015-2017, during which an average of 973 catfish ponds were observed each year. We collected data associated with each pond's physical surroundings and contents and used occupancy modeling to determine their influence on avian occupancy probability. We also collected data associated with stocking practices and catfish health on a subset of ponds, and constructed resource selection functions to model their influence on avian presence. Pond area was positively related to occupancy probability of each species. Cormorant occupancy increased as pond distance from forest cover and activity centers, such as workshops and offices, increased. Distance to nearest activity center was positively related to egret occupancy, while distance to nearest forested area was negative. Ponds containing diseased catfish had an increased probability of use by both herons and egrets. In general, cormorants and egrets showed greater probability of use on the periphery of pond clusters. The abundance of catfish was positively related to cormorant and heron presence. Specific pond contents and characteristics influenced presence of each avian species in different ways, including fish species cultured, production methods, pond systems, and fish types. Many pond selection relationships were species-specific, illustrating inherent differences in their foraging ecology. Consequently, specific management actions aimed to reduce avian presence will depend on the targeted species., Competing Interests: The authors have declared that no competing interests exist.

The United States, particularly the southern portion, has recently suffered drastic population expansion of wild pigs causing destruction of prime farmland. An associated concern, which has been understudied, is the potential transfer of nutrients and pathogens to surface water. This study aimed to identify the abiotic and biotic impacts of captive wild pigs on water quality, including nutrients, fecal indicator and pathogenic bacteria, and antimicrobial resistance. Overall, the study demonstrated that wild pigs harbored Salmonella spp., Campylobacter spp., Escherichia coli, and Clostridium perfringens, which were found in water runoff collected directly beneath the hog paddock, often 2 log 10 greater than above-paddock levels. However, the impacts to downstream water quality were limited, perhaps because of a relatively large riparian buffer between the paddock and surface water. A higher rate of ammonium concentration changes over time was detected in the runoff water below the paddock; additionally, microbial releases detected in runoff were also time dependent, possibly associated with increasing pig numbers. Antibiotic resistance was generally not associated with the wild pigs. Antibiotic resistance genes were found in upstream as well as downstream surface water, suggesting that nonpoint sources of microbial contamination were present. Interestingly, intI1 levels were greater in below-paddock runoff by nearly 2 log 10 . Overall, it appears that wild pigs potentially pose a threat to water quality but only if they have direct access to the water. Pathogen, fecal indicator bacteria, and some nutrient release were significantly associated with wild pigs, but riparian buffers limited water quality impairment., (© 2019 The Authors. Journal of Environmental Quality © 2019 American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America.)

Determining how animals respond to differences in resource availabilities across spatiotemporal extents is critical to our understanding of organism distributions. Variations in resource distribution leading to changes in spatial arrangements across landscapes are indicative of a habitat functional response. Our goal was to assess how resource availabilities influenced both second-order (i.e., home ranging behavior) and third-order (i.e., habitat or resource selection) selection by feral pigs ( Sus scrofa ) in an agricultural landscape. We defined agriculturally based seasons to estimate home range characteristics using autocorrelated kernel density estimation within each season. We then modeled home range size as a function of resource availability (i.e., resource selection analyses) to determine whether individual behaviors were predicted by shifts in home ranging behavior. Both home range analyses and resource selection analyses indicated seasonal differences in selection for agricultural resources as availabilities changed, suggesting second- and third-order selection is mechanistically linked through a habitat functional response., Competing Interests: The authors declare that there is no conflict of interest.

Background: The spatiotemporal distribution of resources is a critical component of realized animal distributions. In agricultural landscapes, space use by generalist consumers is influenced by ephemeral resource availability that may produce behavioral differences across agricultural seasons, resulting in economic and production consequences and increased human-wildlife conflict. Our objective was to assess changes in habitat selection across seasons in an invasive generalist omnivore (feral pigs, Sus scrofa). Hypothesizing that pig space use is primarily driven by forage availability, we predicted strong selection for the most nutritionally beneficial crops and resource types as agricultural seasons progressed. We deployed GPS collars on 13 adult feral pigs in the Mississippi Alluvial Valley to study resource selection in a fragmented agricultural landscape. We estimated resource selection using mixed-effect logistic regression to assess variation in selection across planting, growing, harvest, and fallow seasons., Results: We found that feral pigs varied resource selection across seasons, particularly for corn (Zea mais). We also detected seasonal dependencies in proportional coverage on the net probability of selection of a land unit (e.g., selection was generally strongest for locations composed of both agricultural and natural habitat), resulting in marked variation in predicted space use among agricultural seasons., Conclusions: These findings indicate behavioral changes in selection across agricultural seasons are driven by complex interactions between the availabilities of temporally dynamic resources and temporally static natural cover. Temporal variations in resource selection trends indicate seasonal responses to crop phenology which suggests a season-specific habitat functional response., Competing Interests: The authors have declared that no competing interests exist.

The ideal free distribution (IFD) requires that individuals can accurately perceive density-dependent habitat quality, while failure to discern quality differences below a given perception threshold results in distributions approaching spatial uniformity. Here, we investigate the role of population growth in restoring a nonideal population to the IFD. We place a simple model of discrete patch choice under limits to the resolution by which patch quality is perceived and include population growth driven by that underlying quality. Our model follows the population's distribution through both breeding and dispersal seasons when perception limits differ in their likely influence. We demonstrate that populations of perception limited movers can approximate an IFD provided sufficient population growth; however, the emergent IFD would be temporally inconstant and correspond to reproductive events. The time to emergence of the IFD during breeding is shorter under exponential growth than under logistic growth. The IFD during early colonization of a community persists longer when more patches are available to individuals. As the population matures and dispersal becomes increasingly random, there is an oscillation in the observance of IFD, with peaks most closely approximating the IFD occurring immediately after reproductive events, and higher reproductive rates producing distributions closer to the IFD.

1. Although local variation in territorial predator density is often correlated with habitat quality, the causal mechanism underlying this frequently observed association is poorly understood and could stem from facultative adjustment in either group size or territory size. 2. To test between these alternative hypotheses, we used a novel statistical framework to construct a winter population-level utilization distribution for wolves (Canis lupus) in northern Ontario, which we then linked to a suite of environmental variables to determine factors influencing wolf space use. Next, we compared habitat quality metrics emerging from this analysis as well as an independent measure of prey abundance, with pack size and territory size to investigate which hypothesis was most supported by the data. 3. We show that wolf space use patterns were concentrated near deciduous, mixed deciduous/coniferous and disturbed forest stands favoured by moose (Alces alces), the predominant prey species in the diet of wolves in northern Ontario, and in proximity to linear corridors, including shorelines and road networks remaining from commercial forestry activities. 4. We then demonstrate that landscape metrics of wolf habitat quality - projected wolf use, probability of moose occupancy and proportion of preferred land cover classes - were inversely related to territory size but unrelated to pack size. 5. These results suggest that wolves in boreal ecosystems alter territory size, but not pack size, in response to local variation in habitat quality. This could be an adaptive strategy to balance trade-offs between territorial defence costs and energetic gains due to resource acquisition. That pack size was not responsive to habitat quality suggests that variation in group size is influenced by other factors such as intraspecific competition between wolf packs., (© 2015 The Authors. Journal of Animal Ecology © 2015 British Ecological Society.)

Movement patterns offer a rich source of information on animal behaviour and the ecological significance of landscape attributes. This is especially useful for species occupying remote landscapes where direct behavioural observations are limited. In this study, we fit a mechanistic model of animal cognition and movement to GPS positional data of woodland caribou (Rangifer tarandus caribou; Gmelin 1788) collected over a wide range of ecological conditions. The model explicitly tracks individual animal informational state over space and time, with resulting parameter estimates that have direct cognitive and ecological meaning. Three biotic landscape attributes were hypothesized to motivate caribou movement: forage abundance (dietary digestible biomass), wolf (Canis lupus; Linnaeus, 1758) density and moose (Alces alces; Linnaeus, 1758) habitat. Wolves are the main predator of caribou in this system and moose are their primary prey. Resulting parameter estimates clearly indicated that forage abundance is an important driver of caribou movement patterns, with predator and moose avoidance often having a strong effect, but not for all individuals. From the cognitive perspective, our results support the notion that caribou rely on limited sensory inputs from their surroundings, as well as on long-term spatial memory, to make informed movement decisions. Our study demonstrates how sensory, memory and motion capacities may interact with ecological fitness covariates to influence movement decisions by free-ranging animals., (© 2015 The Authors. Journal of Animal Ecology © 2015 British Ecological Society.)

The purpose of this study was to identify the differences that exist between collegiate (CS) and scholastic (SS) longsnappers. Six CS (21.4 +/- 1.37 years) and 7 SS (16.7 +/- 1.11 years) longsnappers were filmed performing 10 longsnaps each. The CS and SS longsnappers had 7.0 +/- 0.89 and 2.7 +/- 0.95 years experience longsnapping, respectively. Each of the 10 longsnaps for all subjects were analyzed for takeoff velocity and accuracy. The snap that most closely approximated the individual snapper's median values for takeoff velocity and accuracy was digitized using a 20-point model. CS were both faster (0.85 +/- 0.10 seconds vs. 1.25 +/- 0.19 seconds) and more accurate in terms of mean radial error (29.36 +/- 8.4 cm vs. 47.2 +/- 8.26 cm) than their SS counterparts. These differences were related to body positioning both before and during the longsnap. CS exhibited more shoulder flexion (135 +/- 6.33 degrees ; vs. 98 +/- 9.01 degrees ) and greater elbow extension (133 +/- 8.1 degrees vs. 95 +/- 6.77 degrees ) in the set position phase, along with greater center of mass movement (0.27 +/- 0.02 m vs. 0.14 +/- 0.04 m) in the anterior-posterior direction and less hip flexion (72 +/- 1.85 degrees vs. 49 +/- 9.42 degrees ) during the preflight phase. Longsnapping experience and accuracy were significantly related (r = -0.82, p < 0.05). These results suggest that body positioning both before and during the longsnap motion significantly influence the velocity and accuracy of the longsnap.

A common mode of limb suspension for transtibial amputees is the pin liner/shuttle lock system. Despite its popularity, some clinicians question its use because of observed daily and chronic changes to the residual limb. For this study, we measured limb interface pressures during ambulation with pin and suction suspension systems. No pressure differences were seen between the modes of suspension during stance phase. However, during swing phase, pin suspension maintained an average occlusive compressive pressure of 6.7 kPa on the proximal tissues, as compared to the subocclusive pressure of 1.1 kPa with suction suspension. Simultaneously, pin suspension elevated the peak magnitude of suction to -39.5 kPa at the distal residual limb, compared to -26.1 kPa with suction suspension. During swing phase, the pin liner squeezes proximally while creating a large suction distally on the residual limb and is the likely cause of daily and chronic skin changes observed in pin users.

Interface pressures were measured during ambulation with a normal total-surface weight-bearing suction socket and a vacuum-assisted socket. The vacuum-assisted socket has been shown to eliminate daily volume loss. Urethane liners were instrumented with five force-sensing resistors to measure positive pressures and one air pressure sensor at the distal end of the liner to document negative pressures. Nine unilateral transtibial amputees participated in the study. The vacuum-assisted socket created significantly lower positive-pressure impulse (42.8, 39.6 kPa x s) and peak pressures (83.5, 80.0 kPa) during the stance phase. The pressure impulse (-10.5, -13.3 kPa x s), average (-21.2, -26.5 kPa), and peak (-28.5, -36.3 kPa) negative pressures during swing phase were significantly greater in magnitude with the vacuum-assisted socket. We believe that lower positive pressures seen during stance using the vacuum-assisted socket reduces the fluid forced out and greater negative pressures seen during swing increases the amount of fluid drawn into the limb, thereby preventing volume loss.

Daily volume loss of the stump leads to a poor fit of the prosthetic socket. A method of preventing this volume loss and maintaining a good fit was developed. A vacuum (-78 kPa) was drawn on the expulsion port of a total surface-bearing suction socket to hold the liner tightly against the socket. Stump volume of 10 trans-tibial amputees was measured prior to and immediately after a 30 minute walk with normal and vacuum socket conditions. Under the normal condition, the limb lost an average of 6.5% of its volume during the walk. In contrast, with the liner held tightly by vacuum, the limb gained an average of 3.7% in volume. It is believed that the difference observed between conditions resulted from a greater negative pressure developed during the swing phase of gait with the vacuum condition. X-rays revealed that the limb and tibia pistoned 4 mm and 7 mm less, respectively, under the vacuum condition. The combination of reduced pistoning and maintenance of volume is thought to account for the more symmetrical gait observed with the vacuum.

Nordic skiing has a long history dating back to at least 2500 B.C. It is not surprising then that skiing equipment has undergone many changes. Today's skis, poles, and boots use the latest in space-age synthetics including carbon and Kevlar fibers, which has resulted in an unprecedented advance in ski equipment technology, producing ultralight yet strong equipment. These changes have played an important role in bringing about an improvement in racing performance with today's skiers being able to ski a course in half the amount of time that it would have taken just 60 yr ago. Estimates indicate the change in mass of racing equipment accounts for a relatively small amount (12%) of the improvement in race performance with changes in the functional characteristics of equipment, track preparation, and training practices being responsible for the remaining 88%. In addition to improvements in ski equipment, advances are being made in developing laboratory equipment used to assess an athlete's upper body power and endurance capacities. Lab testing with an arm ergometer showed its utility when it exposed a glaring deficiency in upper body power among a group of U.S. developmental skiers. Further improvement in ski equipment and lab testing tools are expected in the future as the worldwide technological revolution continues and Olympic Teams and sports science groups continue to work cooperatively.

Continuous heart rate recordings were obtained on elite American bi-athletes during competitions to provide a better understanding of the physiological demands of biathlon and the strategies used in approaching the shooting range. The findings demonstrate that the average age heart rate during skiing was approximately 90% of maximum heart rate. Heart rates decreased 10-12 bpm over a time period of approximately 50-60 sec during the approach to the firing line. At arrival to the firing line, heart rates were similar for prone and standing shooting averaging 85-87% of maximum heart rate. Mean minimum heart rates while at the firing line dropped to 61-73% of maximum heart rate and averaged approximately 20 bpm lower for prone shooting. The lower minimum heart rates during prone shooting were accounted for by the bi-athletes spending a longer time at the firing line and having a more rapid decrease in heart rate while in the prone position.

This study was originally presented at the American College of Sports Medicine annual meeting in San Diego, CA, 1984. Following repair of the anterior cruciate ligament, it is fairly typical for a patient to return to activity at approximately 12 months postsurgery. The purpose of the study was to quantify quadriceps size and function at 1 year postsurgery. Bilateral isokinetic torque measurements, tomographic scans, muscle biopsies, and anthropometrics were performed on 13 patients (3 females, 10 males) at 13 months post-surgery. The operative leg was 3% smaller in circumference, 10% smaller in total muscle area, 12% smaller in quadriceps area (all p < 0.05) and had a 9% larger subcutaneous fat area (p = 0.06). No difference in hamstrings area was seen. Isokinetic torques for the quadriceps were reduced by 11-15% in the operative leg (p < .05) with no difference seen between the hamstrings torques. Types I and II fibers were clinically smaller in both legs with the type II fibers being significantly (p < 0.05) reduced in the operative leg. It was concluded that 1) leg circumference was a poor indicator of muscle size due to the selective fat deposition in the operative leg, 2) the cross-sectional area of muscle was proportional to isokinetic torque at 240/sec, and 3) there were clinically and statistically significant isokinetic torque differences between quadriceps 13 months post-surgery.J Orthop Sports Phys Ther 1988;9(7):245-249.

Clinical isokinetic characteristics for professional ballet artists were determined preseason and at "peak" season. Twenty-eight dancers (equal N/sex) were studied at 45, 90, and 180 per second. The data indicated that, while male relative torques were similar to other athletes previously reported, the females were lower than most other female athletes. With training, males showed virtually no change at the slow and intermediate speeds, but improved at 180 per second, while females improved at all three speeds but, significantly, only at 180 per second. Males generated significantly more torque than females and the torque-velocity characteristics between sexes were parallel. Clinical characteristics showed the dancers to have quadricep balance between legs and proportional (hamstrings/quadriceps) within legs (no effects of training on either). The data indicates that male dancers have characteristics similar to other athletes, that females are lower in relative torque than other female athletes, and that dance training affects only torque at functional velocities.J Orthop Sports Phys Ther 1984;5(4):207-211.

The Wingate cycle ergometer test is a widely used test of sustained muscular power. A limitation of the test is the lack of development and retrieval of stored elastic energy due to a lack of an eccentric phase. To measure mechanical power output of the entire stretch-shortening cycle, the test of Bosco et al (1983) was administered to 119 male athletes in 7 different activities during their pre-participation evaluations. The sports tested were indoor soccer, American football and ballet (professionals), outdoor soccer, basketball and wrestling (collegiate) and amateur bobsled. Results showed the overall average power output to be 20.37 W.kg-1 for the 60s reciprocal jumping test. Ballet dancers generated significantly less mechanical power than indoor soccer, basketball and bobsled athletes, while wrestlers generated significantly less power than indoor soccer and basketball athletes (all p less than 0.05). No other between-sport differences were seen. A subset of indoor soccer players (n = 10) were retested after 4 months of training. Power improved from 20.8 to 24.3 W.kg-1 (p less than 0.05). While between sport differences were limited, training differences in one subset of athletes were readily identified.