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Thomas Gotschi

Background:

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.

Methods:

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.

Results:

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.

Conclusions:

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.

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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.

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Faye Prior, Margaret Coffey, Anna Robins and Penny Cook

Background: Exercise referral schemes (ERSs) support inactive adults, who have chronic health conditions, to become physically active. Uncertainty exists regarding the effectiveness of ERSs, with few studies evaluating their long-term impact. The aims of this study were to evaluate the long-term impact (12 mo) of participation in an ERS on self-reported physical activity (PA) and a range of health-related outcomes. Methods: Data were analyzed for participants of a 24-week ERS who attended a week 52 follow-up between July 2015 and 2017. PA and health-related outcomes collected at weeks 1, 24, and 52 were analyzed using the Friedman test and Wilcoxon signed-ranks test. Results: A total of 273 participants attended the week 52 follow-up. Self-reported PA significantly increased by a median of 636 MET minutes at week 52. There were also significant improvements in body mass index, systolic blood pressure, mental well-being, and health-related quality of life. Conclusions: For every 8 participants referred to this 24-week ERS, 1 participant went on to show long-term improvements in at least 1 health indicator. The evidence base requires further long-term evaluations to confirm these findings across a range of ERS providers. Changes in self-reported PA would be supported by the inclusion of device-based measurment of PA.

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Cyril Schmit, Rob Duffield, Christophe Hausswirth, Aaron J. Coutts and Yann Le Meur

Purpose:

To describe the effect of the initial perceptual experience from heat familiarization on the pacing profile during a freepaced endurance time trial (TT) compared with temperate conditions.

Methods:

Two groups of well-trained triathletes performed two 20-km TTs in either hot (35°C and 50% relative humidity [RH], n = 12) or temperate (21°C and 50% RH, n = 22) conditions, after standardization of training for each group before both trials. To ensure no physiological acclimation differences between conditions, the TTs for both groups were separated by 11 ± 4 d.

Results:

Performance improvement in the heat (11 ± 24 W) from the 1st to 2nd trial appeared comparable to that in temperate conditions (8 ± 14 W, P = .67). However, the specific alteration in pacing profile in the heat was markedly different than temperate conditions, with a change from “positive” to an “even” pacing strategy.

Conclusions:

Altered perceptions of heat during heat familiarization, rather than physiological acclimatization per se, may mediate initial changes in pacing and TT performance in the heat. These results highlight the need for athletes without time for sufficient heat acclimatization to familiarize themselves with hot conditions to reduce the uncertainty from behavior-based outcomes that may impede performance.

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Taija Finni and Paavo V. Komi

During dynamic activities it is difficult to assess in vivo length changes in human tendon and aponeurosis. The present study compared the outcome of two methods during unilateral squat jump and drop jump performances of four volunteers. Tendinous tissue elongation of vastus lateralis muscle was estimated using either (a) direct measurement of in vivo fascicle length change and muscletendon length estimation (kinematic method), or (b) prediction using a quadratic force function in combination with direct tendon force measurement (force method). In the kinematic method the most critical measures contributing to the 10% uncertainty were the fascicle angle and fraction of the estimated fascicle length. The force method was most sensitive to resting length, with 1% error margin. Both methods predicted the same pattern of tendinous elongation because of the monotonic force/length relationship. The magnitude of length change, however, differed considerably between both methods. Based on the force method, the changes were only 20% (absolute values) or 30% (strain values) of those obtained with the kinematic method. On average, the maximum strains were 5% with the force method and 15% with the kinematic method. This difference can be explained by the fact that the kinematic method characterizes not only the changes in tendon length but also includes aponeurosis strain along the muscle belly. In addition, the kinematic method may be affected by non-uniform distribution of fascicle length change along the length of the muscle. When applying either method for estimating the patterns of tendon and tendinous tissue length changes during human locomotion, the given methodological considerations should be acknowledged.

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Christos K. Argus, Nicholas D. Gill, Justin W.L. Keogh, Michael R. McGuigan and Will G. Hopkins

Purpose:

There is little literature comparing contrast training programs typically performed by team-sport athletes within a competitive phase. We compared the effects of two contrast training programs on a range of measures in high-level rugby union players during the competition season.

Methods:

The programs consisted of a higher volume-load (strength-power) or lower volume-load (speed-power) resistance training; each included a tapering of loading (higher force early in the week, higher velocity later in the week) and was performed twice a week for 4 wk. Eighteen players were assessed for peak power during a bodyweight countermovement jump (BWCMJ), bodyweight squat jump (BWSJ), 50 kg countermovement jump (50CMJ), 50 kg squat jump (50SJ), broad jump (BJ), and reactive strength index (RSI; jump height divided by contact time during a depth jump). Players were then randomized to either training group and were reassessed following the intervention. Inferences were based on uncertainty in outcomes relative to thresholds for standardized changes.

Results:

There were small between-group differences in favor of strength-power training for mean changes in the 50CMJ (8%; 90% confidence limits, ±8%), 50SJ (8%; ±10%), and BJ (2%; ±3%). Differences between groups for BWCMJ, BWSJ, and reactive strength index were unclear. For most measures there were smaller individual differences in changes with strength-power training.

Conclusion:

Our findings suggest that high-level rugby union athletes should be exposed to higher volume-load contrast training which includes one heavy lifting session each week for larger and more uniform adaptation to occur in explosive power throughout a competitive phase of the season.

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Kyle R. Barnes, Will G. Hopkins, Michael R. McGuigan and Andrew E. Kilding

Purpose:

Runners use uphill running as a movement-specific form of resistance training to enhance performance. However, the optimal parameters for prescribing intervals are unknown. The authors adopted a dose-response design to investigate the effects of various uphill interval-training programs on physiological and performance measures.

Methods:

Twenty well-trained runners performed an incremental treadmill test to determine aerobic and biomechanical measures, a series of jumps on a force plate to determine neuromuscular measures, and a 5-km time trial. Runners were then randomly assigned to 1 of 5 uphill interval-training programs. After 6 wk all tests were repeated. To identify the optimal training program for each measure, each runner’s percentage change was modeled as a quadratic function of the rank order of the intensity of training. Uncertainty in the optimal training and in the corresponding effect on the given measure was estimated as 90% confidence limits using bootstrapping.

Results:

There was no clear optimum for time-trial performance, and the mean improvement over all intensities was 2.0% (confidence limits ±0.6%). The highest intensity was clearly optimal for running economy (improvement of 2.4% ± 1.4%) and for all neuromuscular measures, whereas other aerobic measures were optimal near the middle intensity. There were no consistent optima for biomechanical measures.

Conclusions:

These findings support anecdotal reports for incorporating uphill interval training in the training programs of distance runners to improve physiological parameters relevant to running performance. Until more data are obtained, runners can assume that any form of high-intensity uphill interval training will benefit 5-km time-trial performance.

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Chris McGlory and James P. Morton

The aim of this study was to determine the effects of postexercise ingestion of different-molecular-weight glucose polymer solutions on subsequent high-intensity interval-running capacity. In a repeated-measures design, 6 men ran for 60 min in the morning at 70% VO2max. Immediately post- and at 1 and 2 hr postexercise, participants consumed a 15% low-molecular-weight (LMW) or high-molecular-weight (HMW) carbohydrate solution, at a rate of 1.2 g of carbohydrate/kg body mass, or an equivalent volume of flavored water (WAT). After recovery, participants performed repeated 1-min intervals at 90% VO2max interspersed with 1 min active recovery (walking) until volitional exhaustion. Throughout the 3-hr recovery period, plasma glucose concentrations were higher (p = .002) during the HMW and LMW conditions than with WAT (M 7.0 ± 0.8, 7.5 ± 1.0, and 5.6 ± 0.2 mmol/L, respectively), although there was no difference (p = .723) between HMW and LMW conditions. Exercise capacity was 13 (43 ± 10 min; 95% CI for differences: 8–18; p = .001) and 11 min (41 ± 9 min; 95% CI for differences; 2–18: p = .016) longer with HMW and LMW solutions, respectively, than with WAT (30 ± 9 min). There was no substantial difference (2 min; 95% CI for differences: –5 to 10; p = .709) in exercise capacity between LMW and HMW solutions. Although this magnitude of difference is most likely trivial in nature, the uncertainty allows for a possible small substantial enhancement of physiological significance, and further research is required to clarify the true nature of the effect.

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Damien Moore, Tania Pizzari, Jodie McClelland and Adam I. Semciw

Context: Many different rehabilitation exercises have been recommended in the literature to target the gluteus medius (GMed) muscle based mainly on single-electrode, surface electromyography (EMG) measures. With the GMed consisting of 3 structurally and functionally independent segments, there is uncertainty on whether these exercises will target the individual segments effectively. Objective: To measure individual GMed segmental activity during 6 common, lower-limb rehabilitation exercises in healthy young adults, and determine if there are significant differences between the exercises for each segment. Method: With fine-wire EMG electrodes inserted into the anterior, middle, and posterior segments of the GMed muscle, 10 healthy young adults performed 6 common, lower-limb rehabilitation exercises. Main Outcome Measures: Recorded EMG activity was normalized, then reported and compared with median activity for each of the GMed segments across the 6 exercises. Results: For the anterior GMed segment, high activity was recorded for the single-leg squat (48% maximum voluntary isometric contraction [MVIC]), the single-leg bridge (44% MVIC), and the resisted hip abduction–extension exercise (41% MVIC). No exercises recorded high activity for the middle GMed segment, but for the posterior GMed segment very high activity was recorded by the resisted hip abduction–extension exercise (69% MVIC), and high activity was generated by the single-leg squat (48% MVIC) and side-lie hip abduction (43% MVIC). For each of the GMed segments, there were significant differences (P < .05) in the median EMG activity levels between some of the exercises and the side-lie clam with large effect sizes favoring these exercises over the side-lie clam. Conclusions: Open-chain hip abduction and single-limb support exercises appear to be effective options for recruiting the individual GMed segments with selection dependent on individual requirements. However, the side-lie clam does not appear to be effective at recruiting the GMed segments, particularly the anterior and middle segments.

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Adriana V. Savescu, Mark L. Latash and Vladimir M. Zatsiorsky

This article proposes a technique to calculate the coefficient of friction for the fingertip– object interface. Twelve subjects (6 males and 6 females) participated in two experiments. During the first experiment (the imposed displacement method), a 3-D force sensor was moved horizontally while the subjects applied a specified normal force (4 N, 8 N, 12 N) on the surface of a sensor covered with different materials (sandpaper, cotton, rayon, polyester, and silk).The normal force and the tangential force (i.e., the force due to the sensor motion) were recorded. The coefficient of frictiond) was calculated as the ratio between the tangential force and the normal force. In the second experiment (the beginning slip method), a small instrumented object was gripped between the index finger and the thumb, held stationary in the air, and then allowed to drop. The weight (200 g, 500 g, and 1,000 g) and the surface (sandpaper, cotton, rayon, polyester, and silk) in contact with the digits varied across trials. The same sensor as in the first experiment was used to record the normal force (in a horizontal direction) and the tangential force (in the vertical direction). The slip force (i.e., the minimal normal force or grip force necessary to prevent slipping) was estimated as the force at the moment when the object just began to slip. The coefficient of friction was calculated as the ratio between the tangential force and the slip force. The results show that (1) the imposed displacement method is reliable; (2) except sandpaper, for all other materials the coefficient of friction did not depend on the normal force; (3) the skin–sandpaper coefficient of friction was the highest µd = 0.96 ± 0.09 (for 4-N normal force) and the skin–rayon rayon coefficient of friction was the smallest µd = 0.36 ± 0.10; (4) no significant difference between the coefficients of friction determined with the imposed displacement method and the beginning slip method was observed. We view the imposed displacement technique as having an advantage as compared with the beginning slip method, which is more cumbersome (e.g., dropped object should be protected from impacts) and prone to subjective errors owing to the uncertainty in determining the instance of the slip initiation (i.e., impeding sliding).