Movement reprogramming in a task requiring timing accuracy was investigated in young and elderly individuals. The task consisted of manually hitting a hemiball in synchrony with the arrival of a moving light stimulus running through an electronic trackway. Movement reprogramming was required by unexpectedly changing the regular stimulus velocity at different moments before the due time of arrival at the interception position. Such changes produced times after velocity decrease (TAVD) between 150 ms and 750 ms, representing the periods of time available for generation of new movement timing specifications. Effect of probability of stimulus velocity change was investigated by comparing the conditions of 25% and 50% of chance of velocity decrease. Analysis of performance in conditions of velocity decrease showed an enlargement of temporal error as a function of longer TAVDs up to 300-375 ms. In conditions in which TAVDs were longer than 375 ms young participants showed a progressive improvement of accuracy over time, while the elderly were unable to improve their performance even for a TAVD of 750 ms. A trend toward a more efficient reprogramming with reduced uncertainty was observed only in the young. These results indicate that movement reprogramming is a continuous process in young individuals, but it is impaired in the elderly, preventing an appropriate reorganization of the action.
Luis Augusto Teixeira, Mariana Marília Franzoni and Juliana Bayeux da Silva
Gary R. Gray
This study was conducted to determine the reasons that influence the decision to settle a personal injury lawsuit rather than proceed to court for a trial. Additionally, this study compared plaintiff attorneys’ and insurance company attorneys’ reasons for settlement in personal injury lawsuits to determine whether there are significant differences between the two groups. Subjects, 28 plaintiff attorneys and 57 insurance company attorneys, rated the importance of or degree of agreement with 77 statements related to their decision to settle or to recommend settlement. T tests revealed significant differences between the two groups on 31 of the 77 items. Among all 85 attorneys, the top four reasons for settlement were (a) if the opposing attorney offers realistic settlement figures, a jury trial will offer more risk than advantage; (b) settlements are an attractive alternative to a trial partly because of the high costs of litigation; (c) in deciding whether to settle, attorneys attempt to determine the probable verdict in light of the evidence; and (d) attorneys attempt to determine the value of an immediate settlement compared to the uncertainty of a trial.
Scott J. Montain, Samuel N. Cheuvront and Henry C. Lukaski
Uncertainty exists regarding the effect of sustained sweating on sweat mineral-element composition.
To determine the effect of multiple hours of exercise-heat stress on sweat mineral concentrations.
Seven heat-acclimated subjects (6 males, 1 female) completed 5 × 60 min of treadmill exercise (1.56 m/s, 2% grade) with 20 min rest between exercise periods in 2 weather conditions (27 °C, 40% relative humidity, 1 m/s and 35 °C, 30%, 1 m/s). Sweat was collected from a sweat-collection pouch attached to the upper back during exercise bouts 1, 3, and 5. Mineral elements were determined by using inductively coupled plasma-emission spectrography.
At 27 °C, sweat sodium (863  µg/mL; mean [SD]), potassium (222  µg/mL), calcium (16 ) µg/mL), magnesium (1265  ng/mL), and copper (80  ng/mL) remained similar to baseline over 7 h of exercise-heat stress, whereas sweat zinc declined 42–45% after the initial hour of exercise-heat stress (Ex1 = 655 , Ex3 = 382 , Ex5 = 355  µg/mL, P < 0.05). Similar outcomes were observed for sweat zinc at 35 °C when sweat rates were higher. Sweat rate had no effect on sweat trace-element composition.
Sweat sodium, potassium, and calcium losses during multiple hours of sustained sweating can be predicted from initial sweat composition. Estimates of sweat zinc losses, however, will be overestimated if sweat zinc conservation is not accounted for in sweat zinc-loss estimates.
Michael Joch, Mathias Hegele, Heiko Maurer, Hermann Müller and Lisa K. Maurer
Motor learning can be monitored by observing the development of neural correlates of error processing. Among these neural correlates, the error- and feedback-related negativity (Ne/ERN and FRN) represent error processing mechanisms. While the Ne/ERN is more related to error prediction, the FRN is found after an error is manifested. The questions the current study strives to answer are: What information is needed by the system to make error predictions and how is this represented by the Ne/ERN and FRN in a complex motor task? We reduced the information and increased the difficulty level for the prediction in a semivirtual throwing task and found no Ne/ERN but a large FRN when the action result was finally observed (hitting or missing a target). We assume that uncertainty for error prediction was too high (either due to insufficient information or due to lacking prerequisites for prediction), such that error processing had to be mainly based on feedback. The finding is in line with the reinforcement theory of learning, after which Ne/ERN and FRN should behave complementary.
Caroline Barelle, Anne Ruby and Michel Tavernier
Aerodynamic properties are one of the factors that determine speed performance in Alpine skiing. Many studies have examined the consequences of this factor in downhill skiing, and the impact of postural modifications on speed is now well established. To date, only wind tunnel tests have enabled one to measure aerodynamic drag values (a major component of the aerodynamic force in Alpine skiing). Yet such tests are incompatible with the constraints of a regular and accurate follow-up of training programs. The present study proposes an experimental model that permits one to determine a skier's aerodynamic drag coefficient (SCx) based on posture. Experimental SCx measurements made in a wind tunnel are matched with the skier's postural parameters. The accuracy of the model was determined by comparing calculated drag values with measurements observed in a wind tunnel for different postures. For postures corresponding to an optimal aerodynamic penetration (speed position), the uncertainty was 13%. Although this model does not permit an accurate comparison between two skiers, it does satisfactorily account for variations observed in the aerodynamic drag of the same skier in different postures. During Alpine ski training sessions and races, this model may help coaches assess the gain or loss in time induced by modifications in aerodynamic drag corresponding to different postures. It may also be used in other sports to help determine whether the aerodynamic force has a significant impact on performance.
Ceyda Mumcu and Kimberly Mahoney
When individuals need to make a decision, they often face alternatives and some uncertainty. Identifying alternatives and anticipating outcomes in a systematic way provides value in better decision-making. Decision trees help to clarify the choices, risks, monetary gains, and other information involved in the decision. As a result, managers can make an informed decision when choosing the alternative that provides the best net gain and whether the net gain is worthwhile to pursue. As such, this case presents a scenario in which the sport marketing manager of the local sports commission is working with the convention center to bring a sporting event to the city in order to enhance the city’s image and generate positive economic impact. The manager is faced with evaluating three alternatives (Event A, Event B, or neither) and making a recommendation to the sports commission and convention center executives regarding which event to pursue, if any. This case provides an opportunity for students to practice using this strategic management tool to assist in systematic decision-making while investigating the event bidding process.
Paul G. Montgomery and Will G. Hopkins
Australian Football is an intense team sport played over ~120 min on a weekly basis. To determine the effects of game and training load on muscle soreness and the time frame of soreness dissipation, 64 elite Australian Football players (age 23.8 ± 1.8 y, height 183.9 ± 3.8 cm, weight 83.2 ± 5.0 kg; mean ± SD) recorded perceptions of muscle soreness, game intensity, and training intensity on scales of 1–10 on most mornings for up to 3 competition seasons. Playing and training times were also recorded in minutes. Data were analyzed with a mixed linear model, and magnitudes of effects on soreness were evaluated by standardization. All effects had acceptably low uncertainty. Game and training-session loads were 790 ± 182 and 229 ± 98 intensity-minutes (mean ± SD), respectively. General muscle soreness was 4.6 ± 1.1 units on d 1 postgame and fell to 1.9 ± 1.0 by d 6. There was a small increase in general muscle soreness (0.22 ± 0.07–0.50 ± 0.13 units) in the 3 d after high-load games relative to low-load games. Other soreness responses showed similar timelines and magnitudes of change. Training sessions made only small contributions to soreness over the 3 d after each session. Practitioners should be aware of these responses when planning weekly training and recovery programs, as it appears that game-related soreness dissipates after 3 d regardless of game load and increased training loads in the following week produce only small increases in soreness.
Promoting bicycling has great potential to increase overall physical activity; however, significant uncertainty exists with regard to the amount and effectiveness of investment needed for infrastructure. The objective of this study is to assess how costs of Portland’s past and planned investments in bicycling relate to health and other benefits.
Costs of investment plans are compared with 2 types of monetized health benefits, health care cost savings and value of statistical life savings. Levels of bicycling are estimated using past trends, future mode share goals, and a traffic demand model.
By 2040, investments in the range of $138 to $605 million will result in health care cost savings of $388 to $594 million, fuel savings of $143 to $218 million, and savings in value of statistical lives of $7 to $12 billion. The benefit-cost ratios for health care and fuel savings are between 3.8 and 1.2 to 1, and an order of magnitude larger when value of statistical lives is used.
This first of its kind cost-benefit analysis of investments in bicycling in a US city shows that such efforts are cost-effective, even when only a limited selection of benefits is considered.
Stephan Swinnen, Joost Vandenberghe and Erik Van Assche
This study sought to determine the relationships between the cognitive styles field dependence-independence and reflection-impulsivity and the acquisition of a gross motor skill in an unstructured learning environment. In reference to the first cognitive style construct, it was hypothesized that field-independent subjects perform better than field-dependent subjects because they provide organization when the material to be learned lacks structure, leading them to rely on their analyzing and restructuring ability. The second construct refers to cognitive inhibition required for response uncertainty tasks as well as motor impulse inhibition. Subjects (57 boys, 65 girls) were 13-year-old junior high school students. Several visual perceptual tests were administered and gymnastic performance scores were measured at pretest, during the learning session, and posttest. The hypothesis that field-independent subjects are more successful in an unstructured learning environment than field-dependent subjects was confirmed for boys only. The correlations between the reflection-impulsivity variables and gymnastic performance were generally low, and no support could be found for the hypothesis that reflective subjects are more successful in learning the skill than impulsive subjects.
Xavier Ohl, Pierre-Yves Lagacé, Fabien Billuart, Olivier Gagey, Wafa Skalli and Nicola Hagemeister
A robust and reproducible scapular coordinate system is necessary to study scapulothoracic kinematics. The coordinate system recommended by the ISB (International Society of Biomechanics) is difficult to apply in studies using medical imaging, which mostly use a glenoid-centered coordinate system. The aim of this study was to assess the robustness of a glenoid-centered coordinate system compared with the ISB coordinate system, and to study the reproducibility of this coordinate system measure during abduction. A Monte-Carlo analysis was performed to test the robustness of the two coordinate systems. This method enabled the variability of the orientation of the coordinate system to be assessed in a laboratory setting. A reproducibility study of the glenoid-centered coordinate system in the thorax reference frame was performed during abduction in the scapular plane using a low-dose stereoradiography system. We showed that the glenoid-centered coordinate system was slightly more robust than the ISB-recommended coordinate system. Most reproducible rotation was upward/downward rotation (x axis) and most reproducible translation was along the Y axis (superior-inferior translation). In conclusion, the glenoid-centered coordinate system can be used with confidence for scapular kinematics analysis. The uncertainty of the measures derived from our technique is acceptable compared with that reported in the literature. Functional quantitative analysis of the scapulothoracic joint is possible with this method.