ECONOMICALLY OPTIMAL WILDFIRE INTERVENTION REGIMES

Wildfires in the United States result in total damages and costs that are likely to exceed billions of dollars annually. Land managers and policy makers propose higher rates of prescribed burning and other kinds of vegetation management to reduce amounts of wildfire and the risks of catastrophic losses. A wildfire public welfare maximization function, using a wildfire production function estimated using a time series model of a panel of Florida counties, is employed to simulate the publicly optimal level of prescribed burning in an example county in Florida (Volusia). Evaluation of the production function reveals that prescribed fire is not associated with reduced catastrophic wildfire risks in Volusia County Florida, indicating a short-run elasticity of -0.16 and a long-run elasticity of wildfire with respect to prescribed fire of -0.07. Stochastic dominance is used to evaluate the optimal amount of prescribed fire most likely to maximize a measure of public welfare. Results of that analysis reveal that the optimal amount of annual prescribed fire is about 3 percent (9,000 acres/year) of the total forest area, which is very close to the actual average amount of prescribed burning (12,700 acres/year) between 1994-99.Resource /Energy Economics and Policy,

THE RELATIONSHIP BETWEEN MUSCULOSKELETAL STRENGTH, PHYSIOLOGICAL CHARACTERISTICS, AND KNEE KINESTHESIA FOLLOWING FATIGUING EXERCISE

Fatiguing exercise may result in impaired functional joint stability and increased risk of unintentional injury. While there are several musculoskeletal and physiological characteristics related to fatigue onset, their relationship with proprioceptive changes following fatigue has not been examined. The purpose of this study was to establish the relationship between musculoskeletal and physiological characteristics and changes in proprioception, measured by threshold to detect passive motion (TTDPM), following fatiguing exercise. Twenty, physically active females participated (age: 28.65 ± 5.6 years, height: 165.6 ± 4.3 cm, weight: 61.8 ± 8.0 kg, BMI: 22.5± 2.3 kg/m2, BF: 23.3 ± 5.4%). During Visit 1, subjects completed an exercise history and 24-hour dietary questionnaire, and body composition, TTDPM familiarization, isokinetic knee strength, and maximal oxygen uptake/lactate threshold assessments. During Visit 2, subjects completed TTDPM and isometric knee strength testing prior to and following a fatiguing exercise protocol. Wilcoxon signed rank tests determined TTDPM and isometric knee strength changes from pre- to post- fatigue. Spearman’s rho correlation coefficients determined the relationship between strength and physiological variables with pre- to post-fatigue changes in TTDPM and with pre-fatigue and post-fatigue TTDPM in extension and flexion (α=0.05). No significant differences were demonstrated from pre-fatigue to post-fatigue TTDPM despite a significant decrease in isometric knee flexion strength (P<0.01) and flexion/extension ratio (P<0.05) following fatigue. No significant correlations were observed between strength or physiological variables and changes in TTDPM from pre- to post-fatigue in extension or flexion. Flexion/extension ratio was significantly correlated with pre-fatigue TTDPM in extension (r=-0.231, P<0.05). Peak oxygen uptake was significantly correlated with pre-fatigue (r=-0.500, P<0.01) and post-fatigue (r=-0.520, P<0.05) TTDPM in extension. No significant relationships were demonstrated between musculoskeletal and physiological characteristics and changes in TTDPM following fatigue. The results suggest that highly trained individuals may have better proprioception, and that the high fitness level of subjects in this investigation may have contributed to absence of TTDPM deficits following fatigue despite reaching a high level of perceptual and physiological fatigue. Future studies should consider various subject populations, other musculoskeletal strength characteristics, and different modalities of proprioception to determine the most important contributions to proprioceptive changes following fatigue

Comparing Energy Expenditure During Land and Shallow Water Walking in Overweight and Obese Females

Introduction: The prevalence of overweight and obesity in the United States has reached epidemic levels. Reduction in body weight is of great importance for overweight and obese individuals through the increase in physical activity. One particular mode of physical activity that is currently growing in popularity is shallow water walking, although little research has been done examining the energy cost of this activity in an overweight and obese population. Purpose: To compare the energy expenditure (kcal/min) and rating of perceived exertion (RPE) of a bout shallow water walking at a self-selected pace to a bout of land walking at a matched heart rate response and to a bout of land walking at a self-selected pace in overweight and obese women. Methods: Nineteen participants completed three 10-minute experimental trials including a self-selected pace shallow water walking trial, a matched heart rate response land walking trial, and a self-selected pace land walking trial. Results: Significantly lower energy expenditure (p= 0.046) was observed for shallow water walking (6.46 ± 1.38 kcal/min) compared to the matched heart rate response land walking bout (7.26 ± 1.29 kcal/min), although no significant differences were detected for energy expenditure for shallow water walking and self-selected pace land walking (6.92 ± 1.61 kcal/min). No significant differences were detected for RPE across conditions (p=0.439). Exploratory analyses revealed correlations between measures of body composition (BMI and percent body fat) and the difference in energy expenditure between shallow water walking and matched heart rate response land walking. Conclusions: Findings from the current study suggest that although producing energy expenditure compared to heart rate matched land walking, shallow water walking is a viable alternative that can elicit and increase in energy expenditure performed at a moderate intensity, meeting ACSM criteria. Results of the exploratory analyses revealed an association between measures of body composition and differences in energy expenditure. Although only a limited number of participants of the present study had BMI’s above 35.0 kg/m2 (n=2), findings suggest that water exercise may be an alternative form of exercise and produce higher caloric expenditure at higher ranges of BMI and percent body fat

Energy Cost of Land and Shallow Water Walking in Females who are Overweight and Obese

Nineteen overweight or obese females completed three 10-minute experimental trials including a self-selected pace shallow water walking trial, a matched heart rate response land walking trial, and a self-selected pace land walking trial. Energy expenditure (kcal·min-1) was computed from expired gases assessed via indirect calorimetry. Results showed energy expenditure was lower (p= 0.046) during shallow water walking (6.46 ± 1.38 kcal·min-1) compared to matched heart rate response land walking trial (7.26 ± 1.29 kcal·min-1), with no significant difference in between shallow water and self-selected pace land walking (6.92 ± 1.61 kcal·min-1 ). The present study did not demonstrate superior energy cost of shallow water walking. However, results demonstrate that shallow water walking elicits an increase in energy expenditure, which may indicate that this form of activity is a reasonable alternative to land-based walking. Moreover, this form of activity may be particularly effective for individuals with mobility limitations during land-based exercise

Energy Cost of Land and Shallow Water Walking in Females who are Overweight and Obese

Nineteen overweight or obese females completed three 10-minute experimental trials including a self-selected pace shallow water walking trial, a matched heart rate response land walking trial, and a self-selected pace land walking trial. Energy expenditure (kcal·min-1)was computed from expired gases assessed via indirect calorimetry. Results showed energy expenditure was lower (p= 0.046) during shallow water walking (6.46 ± 1.38 kcal·min-1) compared to matched heart rate response land walking trial (7.26 ± 1.29 kcal·min-1), with no significant difference in between shallow water and self-selected pace land walking (6.92 ± 1.61 kcal·min-1). The present study did not demonstrate superior energy cost of shallow water walking. However, results demonstrate that shallow water walking elicits an increase in energy expenditure, which may indicate that this form of activity is a reasonable alternative to land-based walking. Moreover, this form of activity may be particularly effective for individuals with mobility limitations during land-based exercise

Ecological integrity and western water management: a Colorado perspective

Sept. 1995.Includes bibliographical references

Accuracy of Recall of Musculoskeletal Injuries in Elite Military Personnel: A Cross-Sectional Study

Background Self-reported data are often used in research studies among military populations. Objective The accuracy of self-reported musculoskeletal injury data among elite military personnel was assessed for issues with recall. Design Cross-sectional study. Setting Applied research laboratory at a military installation. Participants A total of 101 subjects participated (age 28.5±5.6 years). Study participants were active duty military personnel, with no conditions that precluded them from full duty. Primary and secondary outcome measures Self-reported and medical record reviewed injuries that occurred during a 1-year period were matched by anatomic location, injury side (for extremity injuries), and injury year and type. The accuracy of recall was estimated as the per cent of medical record reviewed injuries correctly recalled in the self-report. The effect of injury anatomic location, injury type and severity and time since injury, on recall, was also assessed. Injuries were classified as recent (≤4 years since injury) or old injuries (\u3e4 years since injury). Recall proportions were compared using Fisher\u27s exact tests. ResultsA total of 374 injuries were extracted from the subjects\u27 medical records. Recall was generally low (12.0%) and was not different between recent and old injuries (P=0.206). Injury location did not affect recall (P=0.418). Recall was higher for traumatic fractures as compared with less severe non-fracture injuries (P values 0.001 to \u3c0.001). Recall for non-fracture injuries was higher for recent as compared with old injuries (P=0.033). This effect of time since injury on recall was not observed for fractures (P=0.522). Conclusions The results of this study highlight the importance of weighing the advantages and disadvantages of self-reported injury data before their use in research studies in military populations and the need for future research to identify modifiable factors that influence recall

Seasonal Shifts in Jumping Patterns: A Study of Countermovement Jump Strategies in High School Football Athletes

Modern sporting trends have begun to adopt sport science and load monitoring to identify in-season trends with the goal of improving performance and reducing injury. Although these resources have become increasingly common in professional and collegiate sports, many high school athletic programs have yet to adopt such technologies. While previous research has demonstrated season-long changes in jump performance, no research has investigated the impact of in-season demands on the changes in jump strategy in male high school football athletes. PURPOSE: The purpose of this study was to examine changes in jump strategy in high school football players over a single football season. METHODS: Sixty-nine male high school football athletes, including 25 offensive skill, 23 linemen, 12 linebackers, 7 defensive backs, and 2 special teams players were tested for maximal jump performance at the beginning and end of a high school football season. Testing was conducted using three attempts of a maximal hands-on-hips countermovement jump on portable force plates, with the average of the three jumps used for analysis. A minimum of 10-weeks between sessions accounted for the time between pre- and post-testing. A dependent-samples t-test was performed to calculate differences between the two time points. RESULTS: Significant reductions were observed across all phases of the jump movement revealed significant differences from pre- to post- testing. The largest reduction was seen during the unweighting phase (0.40 to 0.36s), followed by braking phase (0.22 to 0.19s), and finally propulsive phase (0.30 to 0.28s). Resulting in a total time to takeoff decrease of 0.92 seconds to 0.83 seconds, resulting in an increase in mean jump height (14.15 to 14.89 inches). Jump strategy differences were also significantly different between time points for modified reactive strength index (0.40 to 0.47 and stiffness metrics (-4996.86 to -5622.46N/m). No differences were seen for countermovement depth (t(68) = 0.44, p=0.663) between the two time points. CONCLUSION: At the end of a competitive season, high school football athletes increased their speed at all phases of the jumping motion. Despite the increased speed during the movement, there were no changes in the countermovement depth prior to takeoff. Our research indicates that football athletes become faster and more efficient with their CMJ strategy to achieve increased performance as measured by Jump Height. Future studies may benefit from collecting follow-up data collection to examine the detraining effect that can occur post-competition, and to incorporate differences between double and single leg jumping strategy. Doing so has the potential to identify injury risk and asymmetries throughout the season

Countermovement Jump Performance Trends in High School Football Players Throughout a Competitive Season

Football is the largest participation sport amongst male high school athletes in the country with over one million participants. Previous research has demonstrated that countermovement jump (CMJ) performance is negatively affected by in-season fatigue in contact sports such as rugby and hockey. However, little data are available to describe how CMJ performance and force metrics change in high school athletes throughout a competitive football season. PURPOSE: The purpose of this study was to examine the changes in strength and power metrics in high school football players over a single football season. METHODS: Sixty-nine male high school football athletes comprised of 25 offensive skill players, 23 linemen, 12 linebackers 7 defensive backs, and 2 special teams players were tested for maximal lower body force output at the beginning and end of a high school football season. Testing was conducted using three attempts of a maximal hands-on-hips countermovement jump on portable force plates, with the average of the three jumps used for analysis. Pre-testing occurred prior to the first game of the season, and post-test was conducted after the final game of the season with a minimum of 10-weeks between sessions accounted for the time between pre- and post-testing. A dependent-samples t-test was performed to calculate differences between the two time points. RESULTS: Significant improvements in jump height (14.15 to 14.89 inches), relative force at minimum displacement (220.36 to 235.77% body weight), peak relative braking force (220.72 to 236.39% body weight), peak relative propulsive force (238.07 to 248.02% body weight), peak braking velocity (-1.17 to -1.30m/s), and takeoff velocity (2.64 to 2.71m/s). No significant differences were seen in relative peak landing force (t(68) = 0.53, p=0.600). CONCLUSION: At the end of a competitive season, high school football athletes produced more force and increased their movement velocity, resulting in improvements in jump height compared to the beginning of the season. However, there were no significant differences in landing metrics indicating no changes in force absorption capacity. These increases in jump performance do not reflect results previously reported in contact sports such as rugby and hockey where jump performance typically decreased over the course of a season. Future studies may benefit from collecting additional performance data to assess the impact seasonal fatigue has on other body systems separate to lower body power production, and the effect to which practice and strength and conditioning programming impact force metrics. Without appropriate monitoring strategies, coaches are leaving the assessment of load management to chance, which can potentially lead to decreased performance and an increased chance of injury

A Comparison of Cervical and Trunk Musculoskeletal Characteristics between Female and Male Army Helicopter Pilots

Introduction: Neck pain (NP) and low back pain (LBP) are prevalent among military helicopter pilots. Although there have been few studies on sex differences in the NP/LBP prevalence in this population, females are shown to be at a greater risk of NP/LBP in civilian studies. This disparity may be due to musculoskeletal characteristics differences that predispose females for NP/LBP. The purpose of this study was to compare cervical and trunk musculoskeletal characteristics between male and female pilots. Methods: A total of 8 female pilots (Age: 27.6 ± 4.2yrs, HT: 166.1 ± 7.7cm, WT: 67.9 ± 10.6kg) were tested, and they were matched (1:1 matching ratio) with male pilots (Age: 27.8 ± 4.2yrs, HT: 175.0 ± 6.8cm, WT: 79.5 ± 5.8kg), based on age (± three years) and flight experience (± two years). Cervical/trunk strength and flexibility were tested using the hand-held/isokinetic dynamometer and inclinometers, respectively. Strength values were normalized to body weight for analyses. Paired t-tests or Wilcoxon Signed Rank tests were used to examine sex differences across all variables (p \u3c 0.05). Results: Female pilots had significantly lower cervical flexion strength, trunk flexion strength, and trunk rotation strength (p \u3c 0.05). For flexibility measures, female pilots had significantly greater cervical rotation flexibility (p \u3c 0.05). No significant differences were observed in the lumbar spine flexibility. Discussion/Conclusion: The current preliminary study found sex differences in cervical and trunk musculoskeletal characteristics in Army helicopter pilots. Continued efforts are warranted to explore sex-specific intervention strategy and its effectiveness in reducing the NP/LBP prevalence among military helicopter pilots