Description

This journal's original articles report on new educational developments as well as sound physical fitness practices and the treatment of sports injuries. The journal helps readers enhance their basic understanding about the role of physical activity in human health and function.

Publications in this journal

• Occupational relevance and body mass bias in military physical fitness tests.

  Authors: Paul M Vanderburgh

  Medicine and science in sports and exercise. 40(8):1538-45.

  Recent evidence makes a compelling case that US Army, Navy, and Air Force health-related physical fitness tests penalize larger, not just fatter, service members. As a result, they tend to receiveRecent evidence makes a compelling case that US Army, Navy, and Air Force health-related physical fitness tests penalize larger, not just fatter, service members. As a result, they tend to receive lower scores than their lighter counterparts, the magnitude of which can be explained by biologic scaling laws. Larger personnel, on the other hand, tend to be better performers of work-related fitness tasks such as load carriage, heavy lifting, and materiel handling. This has been explained by empirical evidence that lean body mass and lean body mass to dead mass ratio (dead mass = fat mass and external load to be carried/lifted) are more potent determinants of performance of these military tasks than the fitness test events such as push-ups, sit-ups, or 2-mile-distance run time. Because promotions are based, in part, on fitness test performance, lighter personnel have an advancement advantage, although they tend to be poorer performers on many tests of work-related fitness. Several strategies have been proposed to rectify this incongruence including balanced tests, scaled scores, and correction factors-yet most need large-scale validation. Because nearly all subjects in such research have been men, future investigations should focus on women and elucidate the feasibility of universal physical fitness tests for all that include measures of health- and work-related fitness while imposing no systematic body mass bias.

• Favorable and Prolonged Changes in Blood Lipid Profile after Muscle-Damaging Exercise.

  Authors: Michalis Nikolaidis, Vassilis Paschalis, Giannis Giakas, Ioannis Fatouros, Giorgos Sakellariou, Anastasios Theodorou, Yiannis Koutedakis, Athanasios Jamurtas

  Medicine and science in sports and exercise. 40(8):1483-1489.

  PURPOSE:: To examine the effect of repeated muscle-damaging exercise on the time-course changes in blood lipid and lipoprotein profile and compare them with changes in indices of muscle function andPURPOSE:: To examine the effect of repeated muscle-damaging exercise on the time-course changes in blood lipid and lipoprotein profile and compare them with changes in indices of muscle function and damage. METHODS:: Twelve women underwent an isokinetic exercise session consisting of 75 eccentric knee flexions, which was repeated after 3 wk. Triacylglycerols (TG), total cholesterol (TC), and high-density lipoprotein cholesterol (HDLC) in plasma were measured before, immediately, 1, 2, 3, 4, and 7 d after muscle-damaging exercise. Low-density lipoprotein cholesterol (LDLC) and TC/HDLC were also calculated. RESULTS:: The largest changes in TG and lipoproteins appeared 3 d after exercise, returning toward baseline thereafter. The magnitudes of these changes at 3 d compared with rest were -18% and -8% for TG, -14% and -10% for TC, 8% and 7% for HDLC, -25% and -18% for LDLC, and -20% and -15% for TC/HDLC after sessions 1 and 2, respectively. In addition, the incremental or decremental area under the curve for the TG and lipoproteins measured after the first session was higher than that after the second session-except for HDLC concentration. CONCLUSION:: These findings reveal that lipid and lipoprotein profile was favorably affected by both sessions of muscle-damaging exercise but relatively less so after a repeated session of muscle-damaging exercise.

• Assigning energy costs to activities in children: a review and synthesis.

  Authors: Kate Ridley, Tim S Olds

  Medicine and science in sports and exercise. 40(8):1439-46.

  PURPOSE:: Compendia of energy costs are often used to assign energy expenditures (EE) to self-reported and observed activity. As there is a lack of data on the energy cost of children's everydayPURPOSE:: Compendia of energy costs are often used to assign energy expenditures (EE) to self-reported and observed activity. As there is a lack of data on the energy cost of children's everyday activities, adult values are often used as surrogates. However, the best way to adjust adult values for use with children remains unclear. Various strategies have been used to estimate rates of EE in children. METHODS:: To evaluate these existing methods for assigning EE to children, a literature search reviewed all English-language studies that measured energy costs in healthy 6.0-17.9 yr olds using criterion EE measures. Data were combined using the Monte Carlo simulation procedure, with walking and running forming separate data sets. RESULTS:: The resultant data set (excluding walking and running) contained 5592 data points encompassing 51 activities. Analyses revealed using adults METs, combined with child resting metabolic rates, as the best existing technique to assign EE to children when measured values are not available. Prediction equations for the energy cost of walking and running were calculated using multiple regression. CONCLUSION:: This study has provided a literature base and analytical support for a compendium of energy costs for use with children with energy costs expressed as METs.

• Exercise-Associated Increases in Cardiac Biomarkers.

  Authors: Jürgen Scharhag, Keith George, Rob Shave, Axel Urhausen, Wilfried Kindermann

  Medicine and science in sports and exercise. 40(8):1408-1415.

  At present, the risk of myocardial damage by endurance exercise is under debate because of reports on exercise-associated increases in cardiac biomarkers troponin and B-type natriuretic peptideAt present, the risk of myocardial damage by endurance exercise is under debate because of reports on exercise-associated increases in cardiac biomarkers troponin and B-type natriuretic peptide (BNP); these markers are typically elevated in patients with acute myocardial infarction and chronic heart failure, respectively. Exercise-associated elevations of cardiac biomarkers can be present in elite and in recreational athletes, especially after prolonged and strenuous endurance exercise bouts (e.g., marathon and ultratriathlon). However, in contrast to cardiac patients, it is still unclear if the exercise-associated appearance or increase in cardiac biomarkers in obviously healthy athletes represents clinically significant cardiac insult or is indeed part of the physiological response to endurance exercise. In addition, elevations in cardiac biomarkers in athletes after exercise may generate difficulties for clinicians in terms of differential diagnosis and may result in inappropriate consequences. Therefore, the aim of this article is to provide an overview of exercise-associated alterations of the cardiac biomarkers troponin T and I, ischemia-modified albumin, BNP, and its cleaved inactive fragment N-terminal pro BNP for the athlete, coach, scientist, and clinician.

• Postexercise changes in left ventricular function: the evidence so far.

  Authors: Rob Shave, Keith George, Gregory Whyte, Emma Hart, Natalie Middleton

  Medicine and science in sports and exercise. 40(8):1393-9.

  Whether prolonged exercise results in a transient depression in left ventricular (LV) function has been the focus of numerous studies since the 1960s. This review attempts to summarize the findingsWhether prolonged exercise results in a transient depression in left ventricular (LV) function has been the focus of numerous studies since the 1960s. This review attempts to summarize the findings of this growing body of research. Understanding in this area has followed the advances in imaging techniques and specifically in echocardiographic technology. As such, the review focuses on evidence from the traditional echocardiographic technology (two-dimensional and Doppler measures), the more advanced technique of tissue Doppler imaging (TDI), and finally the assessment of myocardial strain and strain rate. Although many of the studies have adopted a similar cross-sectional pre- to postexercise design, there are often significant differences in terms of subject characteristics, exercise duration, and exercise modality. Accordingly, we draw together the common findings from this growing body of research in an attempt to reach a consensus regarding the influence of prolonged exercise on LV function.

• Intermittent versus Continuous Exercise: Effects of Perceptually Lower Exercise in Obese Women.

  Authors: Jérémy B J Coquart, Christine Lemaire, Alain-Eric Dubart, David-Pol Luttembacher, Claire Douillard, Murielle Garcin

  Medicine and science in sports and exercise. 40(8):1546-53.

  INTRODUCTION:: Exercise has beneficial effects on obesity and diabetes treatments. However, obese subjects do not closely adhere to training programs probably because of the monotony of theINTRODUCTION:: Exercise has beneficial effects on obesity and diabetes treatments. However, obese subjects do not closely adhere to training programs probably because of the monotony of the continuous exercise that is frequently proposed. To increase adherence to training programs, intermittent exercise, which is less monotonous, may be more appropriate. PURPOSE:: The purposes of this study were to determine the perceptually less hard exercise (continuous vs intermittent exercise) and to analyze the impact of a training program on the basis of this exercise in obese women with and without type 2 diabetes. METHODS:: Twenty type 2 diabetic obese women and 20 obese women without diabetes were recruited. In each group, 10 patients integrated a training program (i.e., training groups), whereas the remaining patients were untrained (i.e., control groups). The training groups performed a continuous exercise and an intermittent exercise to determine the perceptually less hard exercise thanks to lower ratings of perceived exertion (RPE). Then, a training program that included 32 min (3 d.wk.10 wk) of the perceptually less hard exercise was proposed to training groups. RESULTS:: RPE were significantly lower during the intermittent exercise compared to the continuous exercise in the obese women with or without diabetes (RPE = 12.3 +/- 2.3 vs 13.7 +/- 2.3 and RPE = 11.9 +/- 1.1 vs 13.2 +/- 1.6, respectively). After the training program, significant beneficial effects on the glycosylated hemoglobin (6.8 +/- 1.4% vs 6.5 +/- 1.2%), body mass (97.1 +/- 16.9 vs 95.2 +/- 16.2 kg), body mass index (37.6 +/- 6.1 vs 36.8 +/- 6.0 kg.m), and on the HR and the walked distance limit were noticed in the training groups. CONCLUSION:: The obese women with or without diabetes perceived the intermittent exercise as being less hard than the continuous exercise, and a training program based on intermittent exercises produced beneficial effects on obesity and type 2 diabetes.

• Energetic Costs of Incidental Visual Coupling during Treadmill Running.

  Authors: Daniel Eaves, Nicola Hodges, A Williams

  Medicine and science in sports and exercise. 40(8):1506-1514.

  PURPOSE:: To determine the role of visual-spatial information in stabilizing movement during treadmill locomotion. METHODS:: Physiological, biomechanical, and psychological indices of coordinationPURPOSE:: To determine the role of visual-spatial information in stabilizing movement during treadmill locomotion. METHODS:: Physiological, biomechanical, and psychological indices of coordination stability were recorded while participants were visually coupled with a whole-body image of themselves during treadmill locomotion. Ten participants ran on a treadmill under three visual conditions: two dynamic images (symmetrical, mirror image; asymmetrical, reversed mirror image) and one static. Performance was examined at two speeds. RESULTS:: Participants ran more economically (mL.kg.min) when they were visually coupled with a symmetrical rather than with an asymmetrical or static image. An asymmetrical coupling resulted in increased variability in footfall position at the faster speed, in comparison to the symmetrical and static conditions. However, at slower speeds, footfall variability and frequency were higher under both dynamic visual conditions in comparison to the static control. Changes in metabolic economy (mL.kg.min) were only partially mediated by movement kinematics. CONCLUSION:: Visual information influences treadmill locomotion and associated measures of stability even when there is no intention to coordinate with external stimuli.

• Effects of high altitude on substrate use and metabolic economy: cause and effect?

  Authors: Barry Braun

  Medicine and science in sports and exercise. 40(8):1495-500.

  In a variety of experimental models, hypoxia causes a shift in substrate use to favor increased dependence on glucose. One explanation for this phenomenon is a selective advantage derived from theIn a variety of experimental models, hypoxia causes a shift in substrate use to favor increased dependence on glucose. One explanation for this phenomenon is a selective advantage derived from the increased metabolic economy (more ATP derived per unit oxygen consumed) that results when glucose is oxidized rather than lipid. In support of this hypothesis, after acclimatization to hypoxia, lower oxygen consumption at a given submaximal workload has often been reported. However, evidence from several experimental models is inconsistent with the idea that the increase in glucose use is causally related to greater metabolic economy.

• Acute Exercise Does Not Cause Sustained Elevations in AMPK Signaling or Expression.

  Authors: Robert S Lee-Young, George Koufogiannis, Benedict J Canny, Glenn K McConell

  Medicine and science in sports and exercise. 40(8):1490-4.

  PURPOSE:: No study has examined the response of skeletal muscle AMP-activated protein kinase (AMPK) signaling beyond the first 3 h after an acute exercise bout in humans. The purpose of this studyPURPOSE:: No study has examined the response of skeletal muscle AMP-activated protein kinase (AMPK) signaling beyond the first 3 h after an acute exercise bout in humans. The purpose of this study was to assess AMPK signaling in human skeletal muscle immediately after a single bout of moderate-intensity endurance exercise and 3 and 24 h after the exercise bout. METHODS:: We examined AMPK signaling, and protein expression of AMPK alpha, ACC-beta, and nNOSmu in untrained individuals (four females and four males) during the 24-h period after a 60-min bout of moderate-intensity (63 +/- 1% V O2peak) cycling endurance exercise. RESULTS:: AMPK alpha2 activity, AMPK alpha2 Thr phosphorylation, and ACC-beta Ser phosphorylation were increased immediately after exercise. These increases had all returned to basal levels at 3 and 24 h after exercise. Furthermore, an acute bout of exercise did not alter AMPK alpha1, AMPK alpha2, ACC-beta, or nNOSmu protein expression during the 24-h period after exercise. CONCLUSION:: Although an acute bout of exercise elicits increases in AMPK signaling, this alone is not sufficient to induce sustained increases in either AMPK signaling or protein expression during the postexercise period.

• beta-Glucan, Immune Function, and Upper Respiratory Tract Infections in Athletes.

  Authors: David C Nieman, Dru A Henson, Mary McMahon, Jenna L Wrieden, J Mark Davis, E Angela Murphy, Sarah J Gross, Lisa S McAnulty, Charles L Dumke

  Medicine and science in sports and exercise. 40(8):1463-71.

  PURPOSE:: This study investigated the effects of oat beta-glucan (BG) supplementation on chronic resting immunity, exercise-induced changes in immune function, and self-reported upper respiratoryPURPOSE:: This study investigated the effects of oat beta-glucan (BG) supplementation on chronic resting immunity, exercise-induced changes in immune function, and self-reported upper respiratory tract infection (URTI) incidence in human endurance athletes. METHODS:: Trained male cyclists were randomized to BG (N = 19) or placebo (P; N = 17) groups and under double-blind procedures received BG (5.6 g.d) or P beverage supplements for 2 wk before, during, and 1 d after a 3-d period in which subjects cycled for 3 h.d at approximately 57% maximal watts. URTI symptoms were monitored during BG supplementation and for 2 wk afterward. Blood samples were collected before and after 2 wk of supplementation (both samples, 8:00 a.m.), immediately after the 3-h exercise bout on day 3 (6:00 p.m.), and 14 h after exercise (8:00 a.m.) and were assayed for natural killer cell activity (NKCA), polymorphonuclear respiratory burst activity (PMN-RBA), phytohemagglutinin-stimulated lymphocyte proliferation (PHA-LP), plasma interleukin 6 (IL-6), IL-10, IL-1 receptor agonist (IL-1ra), and IL-8, and blood leukocyte IL-10, IL-8, and IL-1ra mRNA expression. RESULTS:: Chronic resting levels and exercise-induced changes in NKCA, PMN-RBA, PHA-LP, plasma cytokines, and blood leukocyte cytokine mRNA did not differ significantly between BG and P groups. URTI incidence during the 2-wk postexercise period did not differ significantly between groups. CONCLUSIONS:: An 18-d period of BG versus P ingestion did not alter chronic resting or exercise-induced changes in immune function or URTI incidence in cyclists during the 2-wk period after an intensified exercise.

• Effects of weather on pedometer-determined physical activity in children.

  Authors: James Scott Duncan, Will G Hopkins, Grant Schofield, Elizabeth K Duncan

  Medicine and science in sports and exercise. 40(8):1432-8.

  ABSTRACT: The effects of weather conditions on children's physical activity have not been well described. PURPOSE:: To evaluate the effects of meteorological variables on the number of pedometerABSTRACT: The effects of weather conditions on children's physical activity have not been well described. PURPOSE:: To evaluate the effects of meteorological variables on the number of pedometer steps accumulated by children. METHODS:: Between August and December 2004 (winter to summer), 1115 Auckland children (536 boys, 579 girls; aged 5-12 yr) from 27 socioeconomically and ethnically diverse schools wore sealed multiday memory pedometers for five consecutive days (three weekdays and two weekend days). Values of daily (7 a.m. to 7 p.m.) mean ambient temperature, mean wind speed, precipitation, and duration of bright sunshine were obtained from local meteorological stations. The independent effects of each of these variables on step counts were estimated using composite mixed linear models. Effects were standardized for interpretation of magnitudes. RESULTS:: Weekday and weekend-day step counts for boys were 16,100 +/- 5000 and 12,900+/- 5900 (mean +/- SD), whereas those for girls were 14,200 +/- 4200 and 11,300 +/- 4800. A 10 degrees C rise in mean ambient temperature was associated with a small increase in weekday steps [1700; 90% confidence intervals (CI) +/-1300] and a moderate increase in weekend-day steps (3400; 90% CI +/-1500) for boys, whereas for girls the effects were small (2300; 90% CI +/-1000) and unclear (-300; 90% CI +/-1200), respectively. There were substantial decreases in weekday and weekend-day steps during moderate rainfall (1.1-4.9mm) for both sexes. Most effects of day length, wind speed, and hours of bright sunshine on step counts were trivial or unclear. CONCLUSIONS:: Ambient temperature and rainfall have substantial effects on children's daily step counts and should therefore be considered when comparing physical activity across different locations or periods. Strategies to increase activity on cold or rainy daysmay also be appropriate.

• Clinical significance of cardiac damage and changes in function after exercise.

  Authors: Gregory P Whyte

  Medicine and science in sports and exercise. 40(8):1416-23.

  Acute bouts of ultraendurance exercise may result in the appearance of biomarkers of cardiac cell damage and a transient reduction in left ventricular function. The clinical significance of theseAcute bouts of ultraendurance exercise may result in the appearance of biomarkers of cardiac cell damage and a transient reduction in left ventricular function. The clinical significance of these changes is not fully understood. There seems to be two competing issues to be resolved. First, could prolonged endurance exercise produce a degree of cardiac stress and/or damage that results, during the short or long term, in deleterious consequences for cardiac health. Second, there is a clear need to educate those responsible for the medical care of endurance athletes about the possibility of a transient reduction in cardiac function and the appearance of cTnT/cTnI after an exercise. Minor elevations in cardiac troponins are commonplace after an endurance exercise in elite and recreational athletes and may occur alongside exercise-associated collapse. Misdiagnosis of myocardial injury and subsequent mismanagement can be unnecessarily expensive and psychologically damaging to the athlete. Diagnosis of myocardial injury after prolonged exercise should be made on the basis of all available information and not blood tests alone. The clinical significance of chronic exposure to endurance exercise is unknown. The development of myocardial fibrosis has been suggested as a long-term outcome to chronic exposure to repetitive bouts of endurance exercise and has been linked to an exercise-induced inflammatory process observed in an animal model. This hypothesis is supported by a limited number of studies reporting postmortem studies in athletes and an increased prevalence of complex arrhythmia in veteran athletes. Care is warranted in promoting this hypothesis without further detailed work, given the unequivocal link between exercise and mortality and morbidity. It would seem erroneous, however, to assume that a linear relationship exists between exercise volume and cardiac health.

• Mechanisms underpinning exercise-induced changes in left ventricular function.

  Authors: Jessica M Scott, Darren E R Warburton

  Medicine and science in sports and exercise. 40(8):1400-7.

  Despite a growing body of evidence suggesting that prolonged strenuous exercise (PSE) is associated with a transient reduction in right (RV) and left ventricular (LV) performance, the exactDespite a growing body of evidence suggesting that prolonged strenuous exercise (PSE) is associated with a transient reduction in right (RV) and left ventricular (LV) performance, the exact mechanism(s) responsible for this phenomenon is not fully understood. As such, the primary objective of this article was to critically review the available literature (both animal and human) to provide insight into the potential mechanism(s) responsible for the development of "exercise-induced cardiac fatigue." We pay particular attention to the major mechanisms that have been linked to transient changes in systolic function after PSE including altered loading conditions, myocardial ischemia/damage, altered beta-receptor responsiveness, and altered cardiac autonomic modulation. We also examine the potential mechanisms that may contribute to transient changes in diastolic function often observed after PSE including changes in LV pressure gradients and alterations in intrinsic myocardial relaxation. Although further mechanistic investigations are clearly warranted, several key mechanisms have received support for at least a partial contribution to the transient changes in myocardial performance often observed after PSE.

• Exercise and the Heart: Can you Have too Much of a Good Thing?

  Authors: Keith George, Rob Shave, Darren Warburton, Jürgen Scharhag, Greg Whyte

  Medicine and science in sports and exercise. 40(8):1390-1392.

  Reports that participation in prolonged exercise can lead to a transient depression in ventricular function and/or a minor increase in biomarkers of cardiomyocyte insult have stimulated significantReports that participation in prolonged exercise can lead to a transient depression in ventricular function and/or a minor increase in biomarkers of cardiomyocyte insult have stimulated significant media and scientific attention in the last few years. Despite being of relevance to the scientist, the clinician, and a broad spectrum of athletes, these phenomena are poorly defined and controversial. Specifically, the definition and the description of these topics are quite limited, and conflicting data are available. Further, the mechanisms underpinning these events are not clear. Finally, a clear message related to the short- and the long-term impact on cardiovascular health and/or sports performance is lacking. The symposium "Exercise and the heart: Can you have too much of a good thing?" was presented at the ACSM Annual Meeting in New Orleans on June 1, 2007 to specifically address these issues. This initial introduction sets out the background to the main articles that will document our current understanding of these problems as well as suggest important avenues for further research.

• Resistance training for medial compartment knee osteoarthritis and malalignment.

  Authors: Lauren K King, Trevor B Birmingham, Crystal O Kean, Ian C Jones, Dianne M Bryant, J Robert Giffin

  Medicine and science in sports and exercise. 40(8):1376-84.

  PURPOSES:: 1) To evaluate the effects of a 12-wk high-intensity knee extensor and flexor resistance training program on strength, pain, and adherence in patients with advanced knee osteoarthritis andPURPOSES:: 1) To evaluate the effects of a 12-wk high-intensity knee extensor and flexor resistance training program on strength, pain, and adherence in patients with advanced knee osteoarthritis and varus malalignment and 2) to generate pilot data for change in dynamic knee joint load, patent-reported outcomes, and self-efficacy after training. METHODS:: Fourteen patients (48.35 +/- 6.51 yr) with radiographically confirmed medial compartment knee osteoarthritis and varus malalignment of the lower limb were recruited from a surgical waiting list for high tibial osteotomy. Participants completed a high-intensity isokinetic resistance training program three times per week for 12 wk. Knee extensor and flexor strength were assessed every third week, whereas pain and adherence were recorded at every training session. The external knee adduction moment during the gait, the 6-min-walk test, the Knee Injury and Osteoarthritis Outcome Score (KOOS), and the Arthritis Self-Efficacy Scale (ASES) were also evaluated before and after training. RESULTS:: Significant improvements in knee extensor and flexor strength were observed without increases in pain during or after training. Adherence to the high-intensity program was high. No significant changes were observed for dynamic knee joint load or the KOOS. There was a significant increase in the function subscale of the ASES only. CONCLUSIONS:: These findings suggest that patients with advanced knee osteoarthritis and malalignment can experience substantial gains in strength after a high-intensity resistance training program without concomitant increases in pain, adverse events, or compromised adherence. These findings provide support for future clinical trials with longer-term outcomes.

• Differentiation of RVOT-VT and ARVC in an Elite Athlete.

  Authors: Gregory Whyte, Nigel Stephens, Roxy Senior, Nicholas Peters, Rory O'Hanlon, Sanjay Sharma

  Medicine and science in sports and exercise. 40(8):1357-1361.

  BACKGROUND:: Differentiation of right ventricular outflow tract-ventricular tachycardia (RVOT-VT) and arrhythmogenic right ventricular cardiomyopathy (ARVC) can be problematic in athletes. The highBACKGROUND:: Differentiation of right ventricular outflow tract-ventricular tachycardia (RVOT-VT) and arrhythmogenic right ventricular cardiomyopathy (ARVC) can be problematic in athletes. The high incidence of sudden death as the first clinical manifestation in ARVC highlights the importance of correct diagnosis and treatment. We report on the case of RVOT-VT in an elite female sprinter, and we review the literature on ventricular tachycardia (VT) in the absence of structural heart disease and ARVC. DISCUSSION:: Of patients who present with VT, 10% have no obvious structural disease. In the case of idiopathic VT from the RVOT and LVOT, the arrhythmia is monomorphic and generally not familial. In both disorders, the resting ECG has no identifiable abnormalities, and the echocardiogram and coronary angiography are usually normal. ARVC is a heart muscle disorder characterized by structural and functional abnormalities of the right ventricle due to a fibro-fatty replacement of the myocardium. The natural history of ARVC is considered to include four distinct phases. The early concealed phase of ARVC demonstrates ECG abnormalities concomitant to right and left ventricular dyskinesias. Differential diagnosis during this phase is problematic due to the presence of left bundle branch block morphology VT together with ECG anomalies commonly observed in athletes in RVOT-VT. Furthermore, long-standing VT in RVOT-VT may result in ventricular wall motion abnormalities mimicking ARVC. Radiofrequency ablation may be a valuable tool in the differential diagnosis, because this technique is highly effective in the treatment of RVOT-VT and of limited value in ARVC. Continued follow-up evaluation is an important for the confirmation of disease status after the diagnosis of idiopathic RVOT-VT.

• Let's keep walking.

  Authors: Weimo Zhu

  Medicine and science in sports and exercise. 40(7 Suppl):S509-11.

• Epidemiology of walking and type 2 diabetes.

  Authors: Carl J Caspersen, Janet E Fulton

  Medicine and science in sports and exercise. 40(7 Suppl):S519-28.

  PURPOSE: Diabetes is prevalent, deadly, serious, and costly. It affects an estimated 20.8 million Americans in 2005, having doubled from 1980, and is expected to reach at least 29 million by 2050. InPURPOSE: Diabetes is prevalent, deadly, serious, and costly. It affects an estimated 20.8 million Americans in 2005, having doubled from 1980, and is expected to reach at least 29 million by 2050. In 2002, diabetes was responsible for an estimated $132 billion in costs. Diabetes concerns leaders in public health and clinicians, and its personal, social, and economic burdens require preventive efforts such as the promotion of walking. As such, we reviewed the limited epidemiologic data of walking and incident diabetes (two studies) and walking and mortality outcomes among diabetic persons (three studies). METHODS: We abstracted information from each paper to identify characteristics of the study population, details of the disease outcomes (diabetes incidence, mortality outcomes, or cardiovascular disease events among persons with diabetes), relative risks, risk reductions, and adjustment for covariates. RESULTS: The reviewed studies were adjusted for important covariates such as age, body mass index, the coexistence of other nonwalking and vigorous activities, and so on and for biases such as differential misclassification of exposure. The strength of the observed reductions in risk were between approximately 20% and 40% for incident diabetes and between 40% and 55% for mortality due to all causes and due to cardiovascular disease (and related nonfatal events). Moderate to faster pace of walking seemed to enhance risk reduction. These reductions fit well with results of earlier reviews of physical activity and diabetes, and basically corresponded to 2-3 h of weekly walking. CONCLUSION: Available dose-response data between walking and the aforementioned outcomes suggest that public health recommendations for physical activity might also apply to walking in particular. Regardless, important areas remain for future research on walking and diabetes.

• Built environment correlates of walking: a review.

  Authors: Brian E Saelens, Susan L Handy

  Medicine and science in sports and exercise. 40(7 Suppl):S550-66.

  INTRODUCTION: The past decade has seen a dramatic increase in empirical investigation into the relations between built environment and physical activity. To create places that facilitate andINTRODUCTION: The past decade has seen a dramatic increase in empirical investigation into the relations between built environment and physical activity. To create places that facilitate and encourage walking, practitioners need an understanding of the specific characteristics of the built environment that correlate most strongly with walking. This article reviews evidence on the built environment correlates with walking. METHOD: Included in this review were 13 reviews published between 2002 and 2006 and 29 original studies published in 2005 and up through May 2006. Results were summarized based on specific characteristics of the built environment and transportation walking versus recreational walking. RESULTS: Previous reviews and newer studies document consistent positive relations between walking for transportation and density, distance to nonresidential destinations, and land use mix; findings for route/network connectivity, parks and open space, and personal safety are more equivocal. Results regarding recreational walking were less clear. CONCLUSIONS: More recent evidence supports the conclusions of prior reviews, and new studies address some of the limitations of earlier studies. Although prospective studies are needed, evidence on correlates appears sufficient to support policy changes.

• New techniques and issues in assessing walking behavior and its contexts.

  Authors: Patty S Freedson, Keith Brendley, Barbara E Ainsworth, Harold W Kohl, Eva Leslie, Neville Owen

  Medicine and science in sports and exercise. 40(7 Suppl):S574-83.

  In the first section of this article, we discuss the metabolic responses to walking by describing the economy of walking during different locomotion velocities. Gender, weight status, and growthIn the first section of this article, we discuss the metabolic responses to walking by describing the economy of walking during different locomotion velocities. Gender, weight status, and growth effects on metabolic responses to walking are reviewed. In the second section, we examine the use of technology to assess walking patterns and behavior in the community. We use an engineering approach for understanding how to measure objects that move, and these methods are used to assess walking used in transportation. In the third part of the paper, we summarize self-report methods that have been used to assess walking behavior and highlight the strengths and weaknesses of these methods. We illustrate how self-report methods are used to quantify walking behavior in the surveillance systems that are now widely used to ascertain walking prevalence and temporal changes in different populations. In the final section, we discuss ways of measuring the walkability of neighborhoods and the community to understand the influence of the built environment on walking behavior.

• Assessing walking behaviors of selected subpopulations.

  Authors: Guy C Le Masurier, Adrian E Bauman, Charles B Corbin, James F Konopack, Renee M Umstattd, Richard E A VAN Emmerik

  Medicine and science in sports and exercise. 40(7 Suppl):S594-602.

  Recent innovations in physical activity (PA) assessment have made it possible to assess the walking behaviors of a wide variety of populations. Objective measurement methods (e.g., pedometers,Recent innovations in physical activity (PA) assessment have made it possible to assess the walking behaviors of a wide variety of populations. Objective measurement methods (e.g., pedometers, accelerometers) have been widely used to assess walking and other prevalent types of PA. Questionnaires suitable for international populations (e.g., the International Physical Activity Questionnaire and the Global Physical Activity Questionnaire) and measurement techniques for the assessment of gait patterns in disabled populations allow for the study of walking and its health benefits among many populations. Results of studies using the aforementioned techniques indicate that children are more active than adolescents and adolescents are more active than adults. Males, particularly young males, are typically more active than females. The benefits associated with regular participation in PA for youth and walking for older adults have been well documented, although improvements in the assessments of physical, cognitive, and psychosocial parameters must be made if we are to fully understand the benefits of walking for people of all ages. Most youth meet appropriate age-related PA activity recommendations, but adults, particularly older adults and adults with disabilities, are less likely to meet PA levels necessary for the accrual of health benefits. International studies indicate variation in walking by culture. It is clear, however, that walking is a prevalent form of PA across countries and a movement form that has great potential in global PA promotion. Continued development of measurement techniques that allow for the study of individualized gait patterns will help us add to the already rich body of knowledge on chronically disabled populations and allow for individual prescriptions for these populations.

• Heatstroke during endurance exercise: is there evidence for excessive endothermy?

  Authors: Dale E Rae, Gideon J Knobel, Theresa Mann, Jeroen Swart, Ross Tucker, Timothy D Noakes

  Medicine and science in sports and exercise. 40(7):1193-204.

  PURPOSE: Five of 28,753 cyclists participating in an annual 109-km bicycle race died, four within 24 h of the race and the fifth 17 d later. All five deaths were reported to be the consequence ofPURPOSE: Five of 28,753 cyclists participating in an annual 109-km bicycle race died, four within 24 h of the race and the fifth 17 d later. All five deaths were reported to be the consequence of exertional heatstroke. One runner of 6874 participating in an annual 56-km ultramarathon developed heatstroke and required active cooling for 10 h to achieve normothermia. The purpose of this article was to postulate (i) why only 6 of 35,627 athletes were hospitalized for heatstroke in these races, (ii) if exercise alone could have elevated their body temperatures sufficiently to cause heatstroke, and (iii) why the runner required such prolonged cooling. METHODS: Clinical and autopsy data are presented for three of the cyclists and the runner for whom access to this information was granted. Calculations were made to predict the work rates necessary to produce their measured rectal temperatures. RESULTS: The rectal temperatures of two of the cyclists were 42.0 and 41.2 degrees C on hospitalization, and that of the runner was 41.8 degrees C on collapse. Standard calculations showed that in the prevailing environmental conditions and with their exercise speeds, none should have developed exertional heatstroke. The third cyclist experienced a cardiac arrest to which his elevated (rectal) temperature may have contributed. CONCLUSION: The hyperthermic states experienced by the cases presented may have resulted from failure of their heat-losing mechanisms. Alternatively, they might have resulted from excessive endothermy, triggered by physical exertion and other unknown initiating factors. Excessive endothermy should be considered in cases of heatstroke that occur in mild to moderate environmental conditions. Furthermore, prompt initiation of cooling is crucial in all cases of suspected heatstroke.

• Strength training effects on bone mineral content and density in premenopausal women.

  Authors: Meghan Warren, Moira A Petit, Peter J Hannan, Kathryn H Schmitz

  Medicine and science in sports and exercise. 40(7):1282-8.

  PURPOSE: Mechanical loading, such as that seen with physical activity, is thought to be the primary factor influencing bone strength. Previous randomized studies that assessed the effect of strengthPURPOSE: Mechanical loading, such as that seen with physical activity, is thought to be the primary factor influencing bone strength. Previous randomized studies that assessed the effect of strength training on bone in premenopausal women report inconsistent results. The analysis herein examines the effect of a strength training program following published guidelines (US Department of Health and Human Services) on bone mineral content (BMC) and areal bone mineral content (aBMD) in the proximal femur and lumbar spine in premenopausal women. METHODS: One hundred and forty-eight overweight, sedentary, premenopausal women aged 25-44 were randomized to progressive strength training (ST, n = 72) or standard care (CO, n = 76) for 2 yr. Measurements occurred at baseline, 1 yr, and 2 yr. Proximal femur and lumbar spine BMC and aBMD were measured by dual energy x-ray absorptiometry. Intention-to-treat analyses were completed, and repeated-measures ANCOVA adjusted for baseline height and weight was used to assess the effect of strength training on bone. RESULTS: aBMD showed little change and did not differ between groups at any site. Femoral neck BMC showed a significant difference in the slopes between ST and CO (P = 0.04) with no change in the ST group and a 1.5% decrease in the CO. There were no significant between-group differences at any other measurement site. CONCLUSION: Strength training had no effect on aBMD after 2 yr of strength training. Femoral neck BMC decreased in CO and had no change in ST. Because there was no change in aBMD, strength training may have influenced bone size. Research to better understand changes in bone dimensions and geometry with strength training in premenopausal women is warranted.

• Electrode shift and normalization reduce the innervation zone's influence on EMG.

  Authors: Travis W Beck, Terry J Housh, Joel T Cramer, Moh H Malek, Michelle Mielke, Russell Hendrix, Joseph P Weir

  Medicine and science in sports and exercise. 40(7):1314-22.

  PURPOSE: The purpose of the present study was twofold: (a) to examine the influence of the innervation zone (IZ) on EMG signals from bipolar electrode arrangements that have their center pointPURPOSE: The purpose of the present study was twofold: (a) to examine the influence of the innervation zone (IZ) on EMG signals from bipolar electrode arrangements that have their center point directly over the IZ, 10 mm distal to the IZ, 10 mm proximal to the IZ, and 20 mm distal to the IZ and (b) to investigate the effects of normalization on EMG amplitude and mean power frequency (MPF) values over the IZ. METHODS: Ten men (mean +/- SD age = 23.6 +/- 3.0 yr) performed submaximal to maximal isometric muscle actions of the dominant leg extensors, and four separate bipolar surface EMG signals were detected simultaneously from the vastus lateralis. One bipolar electrode arrangement had its center point located directly over the IZ for the vastus lateralis, whereas the other electrode arrangements had their center points 10 mm proximal, 10 mm distal, and 20 mm distal to the IZ. RESULTS: The results showed that there were no consistent patterns among the four electrode arrangements for the absolute and the normalized EMG amplitude and MPF versus isometric torque relationships. The IZ had the greatest influence on absolute EMG amplitude and MPF values when the center point of the electrode arrangement was directly over the IZ and a decreased effect when the center point was shifted away from the IZ. In addition, normalization reduced the influence of the IZ on EMG amplitude and MPF values. CONCLUSION: Thus, these findings suggested that in situations where it is difficult to identify the precise location and/or avoid the IZ, the EMG signals can provide useful information regarding isometric torque-related changes in normalized EMG amplitude and center frequency values.

• Reductions in postprandial lipemia with exercise: is timing important?

  Authors: Stephen F Burns

  Medicine and science in sports and exercise. 40(7):1353; author reply 1354.

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