Showing papers in "Medicine and Science in Sports and Exercise in 2006"

Biomechanical factors associated with tibial stress fracture in female runners.

Abstract: MILNER, C. E., R. FERBER, C. D. POLLARD, J. HAMILL, and I. S. DAVIS. Biomechanical Factors Associated with Tibial Stress Fracture in Female Runners. Med. Sci. Sports Exerc., Vol. 38, No. 2, pp. 323–328, 2006. Purpose: Tibial stress fractures (TSF) are among the most serious running injuries, typically requiring 6–8 wk for recovery. This cross-sectional study was conducted to determine whether differences in structure and running mechanics exist between trained distance runners with a history of prior TSF and those who have never sustained a fracture. Methods: Female runners with a rearfoot strike pattern, aged between 18 and 45 yr and running at least 32 kmIwk j1 , were recruited for this study. Participants in the study were 20 subjects with a history of TSF and 20 ageand mileage-matched control subjects with no previous lower extremity bony injuries. Kinematic and kinetic data were collected during overground running at 3.7 mIs j1 using a six-camera motion capture system, force platform, and accelerometer. Variables of interest were vertical impact peak, instantaneous and average vertical loading rates, instantaneous and average loading rates during braking, knee flexion excursion, ankle and knee stiffness, and peak tibial shock. Tibial varum was measured in standing. Tibial area moment of inertia was calculated from tibial x-ray studies for a subset of runners. Results: The TSF group had significantly greater instantaneous and average vertical loading rates and tibial shock than the control group. The magnitude of tibial shock predicted group membership successfully in 70% of cases. Conclusion: These data indicate that a history of TSF in runners is associated with

Muscle and blood metabolites during a soccer game: implications for sprint performance.

Abstract: Purpose: To examine muscle and blood metabolites during soccer match play and relate it to possible changes in sprint performance. Methods: Thirty-one Danish fourth division players took part in three friendly games. Blood samples were collected frequently during the game, and muscle biopsies were taken before and after the game as well as immediately after an intense period in each half. The players performed five 30-m sprints interspersed by 25-s recovery periods before the game and immediately after each half (N = 11) or after an intense exercise period in each half (N = 20). Results: Muscle lactate was 15.9 ± 1.9 and 16.9 ± 2.3 mmol·kg-1 d.w. during the first and second halves, respectively, with blood lactate being 6.0 ± 0.4 and 5.0 ± 0.4 mM, respectively. Muscle lactate was not correlated with blood lactate (r2 = 0.06-0.25, P >0.05). Muscle glycogen decreased (P < 0.05) from 449 ± 23 to 255 ± 22 mmol·kg-1 d.w. during the game, with 47 ± 7% of the muscle fibers being completely or almost empty of glycogen after the game. Blood glucose remained elevated during the game, whereas plasma FFA increased (P < 0.05) from 0.45 ± 0.05 to 1.37 ± 0.23 mM. Mean sprint time was unaltered after the first half, but longer (P < 0.05) after the game (2.8 ± 0.7%) as well as after intense periods in the first (1.6 ± 0.6%) and second halves (3.6 ± 0.5%). The decline in sprint performance during the game was not correlated with muscle lactate, muscle pH, or total glycogen content. Conclusion: Sprint performance is reduced both temporarily during a game and at the end of a soccer game. The latter finding may be explained by low glycogen levels in individual muscle fibers. Blood lactate is a poor indicator of muscle lactate during soccer match play.

Effects of a classroom-based program on physical activity and on-task behavior.

Abstract: MAHAR, M. T., S. K. MURPHY, D. A. ROWE, J. GOLDEN, A. T. SHIELDS, and T. D. RAEDEKE. Effects of a Classroom-Based Program on Physical Activity and On-Task Behavior. Med. Sci. Sports Exerc., Vol. 38, No. 12, pp. 2086Y2094, 2006. Purpose: This study evaluated the effects of a classroom-based physical activity program on childrens in-school physical activity levels and on-task behavior during academic instruction. Methods: Physical activity of 243 students was assessed during school hours. Intervention- group students (N = 135) received a classroom-based program (i.e., Energizers). The control group (N = 108) did not receive Energizers. On-task behavior during academic instruction time was observed for 62 third-grade (N = 37) and fourth-grade students (N = 25) before and after Energizers activities. An independent groups t-test compared in-school physical activity levels between intervention and control classes. A multiple-baseline across-classrooms design was used to evaluate the effectiveness of the Energizers on on-task behavior. Additionally, a two-way (time (pre- vs postobservation) period (baseline vs intervention)) repeated-measures analysis of variance compared on-task behavior between observation periods. Magnitudes of mean differences were evaluated with Cohens delta (ES). Results: Students in the intervention group took significantly (P G 0.05) more in-school steps (5587 T 1633) than control-group students (4805 T 1543), and the size of this difference was moderate (ES = 0.49). The intervention was effective in improving on-task behavior; after the Energizers were systematically implemented, on-task behavior systematically improved. The improvement in on-task behavior of 8% between the pre-Energizers and post-Energizers observations was statistically significant (P G 0.017), and the difference was moderate (ES = 0.60). Likewise, the least on-task students improved on-task behavior by 20% after Energizers activities. This improvement was statistically significant (P G 0.001) and meaningful (ES = 2.20). Conclusion: A classroom-based physical activity program was effective for increasing daily in-school physical activity and improving on-task

Neighborhood Environment Walkability Scale: Validity and Development of a Short Form

Abstract: Purpose:The aim of this study was to examine the factorial and criterion validity of the Neighborhood Environment Walkability Scale (NEWS) and to develop an abbreviated version (NEWS-A).Methods:A stratified two-stage cluster sample design was used to recruit 1286 adults. The sample was drawn

Effect of physical education and activity levels on academic achievement in children.

Abstract: Purpose: This study was conducted to determine the effect of physical education class enrollment and physical activity on academic achievement in middle school children. Methods: Participants were 214 sixth-grade students randomly assigned to physical education during either first or second semesters. Moderate and vigorous physical activity (MVPA) (number of 30-min time blocks) outside of school was assessed using the 3-d physical activity recall (3DPAR). The 3DPAR time blocks were converted to ordinal data with scores of 1 (no activity), 2 (some activity), or 3 (activity meeting Healthy People 2010 guidelines). Academic achievement was assessed using grades from four core academic classes and standardized test scores (Terra Nova percentiles). Results: Grades were similar regardless of whether students were enrolled in physical education during first or second semesters. Physical education classes averaged only 19 min of MVPA. Students who either performed some or met Healthy People 2010 guidelines for vigorous activity had significantly higher grades (P < 0.05) than students who performed no vigorous activity in both semesters. Moderate physical activity did not affect grades. Standardized test scores were not significantly related to physical education class enrollment or physical activity levels. Conclusion: Although academic achievement was not significantly related to physical education enrollment, higher grades were associated with vigorous physical activity, particularly activity meeting recommended Healthy People 2010 levels.

International Physical Activity Questionnaire: Validity against fitness.

Abstract: Purpose: This study was conducted to criterion-validate the short format of International Physical Activity Questionnaire (IPAQ) against health-related fitness. Methods: Participants included 951 men, aged 21-43 yr. V?O2max by ergometer was used to measure cardiorespiratory fitness. Muscular fitness tests included the number of sit-ups, push-ups, and squats performed during 60 s. Physical activity was assessed from IPAQ by categories for health (health-enhancing physical activity (HEPA)) and by calculating total and vigorous MET-hours per week. The participants were classified in five groups of almost equal size by the IPAQ outcomes. Moreover, the frequency of vigorous activity was assessed by one precoded question (single-item question on leisure-time vigorous physical activity (SIVAQ)). Results: The mean fitness improved from the first through the fourth IPAQ group. V?O2max in the most active IPAQ group, however, was lower than in the fourth group (P < 0.05), both with HEPA categories and vigorous METs as the outcome. In contrast, the weekly frequency of vigorous physical activity showed a positive association with fitness through all six categories. The 65 sedentary (according to SIVAQ) and unfit individuals who belonged to the highest 20% (by IPAQ total METs) were older (30.6 ± 5.1 vs 28.9 ± 3.8, P = 0.02), more obese (waist 93 ± 12 vs 89 ± 10 cm), more often current smokers (59.4 vs 42.0%; P = 0.03), and less educated (<12 yr of education 70.8 vs 52.0%; P = 0.02), compared with the others in the highest IPAQ group. Conclusions: Almost 10% of young men had poor fitness and apparently low physical activity, but they reported very high physical activity by IPAQ. An evident need therefore exists to develop IPAQ further to solve the apparent overreporting by a considerable proportion of sedentary individuals.

Active Commuting to School: Associations with Environment and Parental Concerns

Abstract: Purpose: This study examined the association of objective and perceived neighborhood environmental characteristics and parent concerns with active commuting to school, investigated whether parental concerns varied by environmental characteristics, and compared the association of the perceived environment, parental concerns, and objective environment on the outcome active commuting to school. Methods: Randomly selected parents of children (aged 5-18 yr), in neighborhoods chosen for their variability in objectively measured walkability and income, completed questionnaires about their neighborhood environment, concerns about children walking to school, and children's behavior (N = 259). Objective measures of the environment were available for each participant and each neighborhood. Logistic regression analyses were used to investigate the relationships among environment, parental concerns, and walking or biking to or from school at least once a week. Results: A parental concerns scale was most strongly associated with child active commuting (odds ratio: 5.2, 95% CI: 2.71-9.96). In high-income neighborhoods, more children actively commuted in high-walkable (34%) than in low-walkable neighborhoods (23%) (odds ratio: 2.1, 95% CI: 1.12-3.97), but no differences were noted in low-income neighborhoods. Parent concerns and neighborhood aesthetics were independently associated with active commuting. Perceived access to local stores and biking or walking facilities accounted for some of the effect of walkability on active commuting. Conclusion: Both parent concerns and the built environment were associated with children's active commuting to school. To increase active commuting to school, interventions that include both environmental change and education campaigns may be needed.

Validity of the polar S810 heart rate monitor to measure R-R intervals at rest.

Abstract: This study was conducted to compare R-R intervals and the subsequent analysis of heart rate variability (HRV) obtained from the Polar S810 heart rate monitor (HRM) (Polar Electro Oy) with an electrocardiogram (ECG) (Physiotrace, Estaris, Lille, France) during an orthostatic test. A total of 18 healthy men (age: 27.1 +/- 1.9 yr; height: 1.82 +/- 0.06 m; mass 77.1 +/- 7.7 kg) performed an active orthostatic test during which R-R intervals were simultaneously recorded with the HRM and the ECG recorder The two signals were synchronized and corrected before a time domain analysis, the fast Fourier transform (FFT) and a Poincare plot analysis. Bias and limits of agreement (LoA), effect size (ES), and correlation coefficients were calculated. R-R intervals were significantly different in the supine and standing position between the ECG and the HRM uncorrected and corrected signal (P 0.05) and well correlated (r > 0.97, P < 0.05), except root mean square of difference (RMSSD) and SD1 in standing position (P < 0.05, ES = 0.052 and 0.057; r = 0.99 and 0.98, respectively). Narrow LoA, good correlations, and small effect sizes support the validity of the Polar S810 HRM to measure R-R intervals and make the subsequent HRV analysis in supine position. Caution must be taken in standing position for the parameters sensitive to the short-term variability (i.e., RMSSD and SD1).

Inverse association between physical inactivity and mental health in men and women.

Abstract: GALPER, D. I., M. H. TRIVEDI, C. E. BARLOW, A. L. DUNN, and J. B. KAMPERT. Inverse Association between Physical Inactivity and Mental Health in Men and Women. Med. Sci. Sports Exerc., Vol. 38, No. 1, pp. 173–178, 2006. Purpose: The Aerobics Center Longitudinal Study (ACLS) provides the opportunity to evaluate associations between measures of physical activity and mental health in a large and well-characterized population of men and women. Methods: Participants were 5451 men and 1277 women (20–88 yr) who completed a maximal fitness treadmill test and self-report measures of habitual physical activity, depressive symptoms (Center for Epidemiological Studies Scale for Depression; CES-D) and emotional well-being (General Well-Being Schedule; GWB). To evaluate the dose–response gradient of the association, we classified the sample, separately for men and women, into three levels of relative cardiorespiratory (CR) fitness (low, moderate, high) on the maximal treadmill test, and four levels on a physical activity index of weekly walking, jogging, and running. Results: In both men and women, there was a significant inverse graded dose–response relationship between maximal CR fitness and the CES-D score (P 0.0001), and a significant positive graded dose–response relationship between CR fitness and the GWB score (P 0.0001). We also observed dose–response associations between the level of physical activity and both CES-D and GWB scores (P 0.0001) that peaked at 11–19 miles per week. Conclusion: Among men and women in the ACLS, relative increases in maximal CR fitness and habitual physical activity are cross-sectionally associated with lower depressive symptomatology and greater emotional well-being. Prospective epidemiological studies and controlled clinical trials are needed to identify the minimal and optimal levels of physical activity and CR fitness associated with various mental health benefits in different segments of the general population. Key Words: CARDIORESPIRATORY FITNESS, DEPRESSION, CES-D, WELLBEING

Anabolic androgenic steroids: a survey of 500 users.

Abstract: Purpose: The use of anabolic androgenic steroids (AAS) to increase muscle size and strength is widespread. Information regarding self-administered AAS used nonmedically to enhance athletic performance or improve physical appearance is sparse and poorly documented. The purpose of this study is to identify current trends in the drug-taking habits of AAS users. Methods: An anonymous self-administered questionnaire was posted on the message boards of Internet Web sites popular among AAS users. Results: Of the 500 AAS users who participated in the survey, 78.4% (392/500) were noncompetitive bodybuilders and nonathletes; 59.6% (298/500) of the respondents reported using at least 1000 mg of testosterone or its equivalent per week. The majority (99.2%) of AAS users (496/500) self-administer injectable AAS formulations, and up to 13% (65/500) report unsafe injection practices such as reusing needles, sharing needles, and sharing multidose vials. In addition to using AAS, 25% of users admitted to the adjuvant use of growth hormone and insulin for anabolic effect, and 99.2% (496/500) of users reported subjective side effects from AAS use. Conclusions: This survey reveals several trends in the nonmedical use of AAS. Nearly four out of five AAS users are nonathletes who take these drugs for cosmetic reasons. AAS users in this sample are taking larger doses than previously recorded, with more than half of the respondents using a weekly AAS dose in excess of 1000 mg. The majority of steroid users self-administer AAS by intramuscular injection, and approximately 1 in 10 users report hazardous injection techniques. Polypharmacy is practiced by more than 95% of AAS users, with one in four users taking growth hormone and insulin. Nearly 100% of AAS users reported subjective side effects.

The Yo-Yo IR2 test: physiological response, reliability, and application to elite soccer.

Abstract: KRUSTRUP, P., M. MOHR, L. NYBO, J. MAJGAARD JENSEN, J. JUNG NIELSEN, and J. BANGSBO. The Yo-Yo IR2 Test: Physiological Response, Reliability, and Application to Elite Soccer. Med. Sci. Sports Exerc., Vol. 38, No. 9, pp. 1666–1673, 2006. Purpose: To examine the physiological response, reliability, and validity of the Yo-Yo intermittent recovery level 2 test (Yo-Yo IR2). Methods: Thirteen normally trained male subjects carried out four Yo-Yo IR2 tests, an incremental treadmill test (ITT), and various sprint tests. Muscle biopsies and blood samples were obtained, and heart rate was measured before, during, and after the Yo-Yo IR2 test. Additionally, 119 Scandinavian elite soccer players carried out the Yo-Yo IR2 test on two to four occasions. Results: Yo-Yo IR2 performance was 591 T 43 (320–920) m or 4.3 (2.6–7.9) min. Test–retest coefficient of variation in distance covered was 9.6% (N = 29). Heart rate (HR) at exhaustion was 191 T 3 bpm, or 98 T 1% HRmax. Muscle lactate was 41.7 T 5.4 and 68.5 T 7.6 mmolIkg j1 d.w. at 85 and 100% of exhaustion time, respectively, with corresponding muscle CP values of 40.4 T 5.2 and 29.4 T 4.7 mmolIkg j1 d.w. Peak blood lactate was 13.6 T 0.5 mM. Yo-Yo IR2 performance was correlated to ITT performance (r = 0.74, P G 0.05) and V u O2max (r = 0.56, P G 0.05) but not to 30- and 50-m sprint performance. Yo-Yo IR2 performance was better (P G 0.05) for international elite soccer players than for moderate elite players (1059 T 35 vs 771 T 26 m) and better (P G 0.05) for central defenders (N = 21), fullbacks (N =2 0), and midfielders (N = 48) than for goalkeepers (N = 6) and attackers (N = 24). Fifteen elite soccer players improved (P G 0.05) Yo-Yo IR2 performance by 42 T 8% during 8 wk of preseasonal training. Conclusion: This study demonstrates that the Yo-Yo IR2 test is reproducible and can be used to evaluate an athlete_s ability to perform intense intermittent exercise with a high rate of aerobic and anaerobic energy turnover. Specifically, the Yo-Yo IR2 test was shown to be a sensitive tool to differentiate between intermittent exercise

Core strength and lower extremity alignment during single leg squats.

Abstract: WILLSON, J. D., M. L. IRELAND, and I. DAVIS. Core Strength and Lower Extremity Alignment during Single Leg Squats. Med. Sci. Sports Exerc., Vol. 38, No. 5, pp. 945–952, 2006. Introduction/Purpose: Muscles of the trunk, hip, and knee influence the orientation of the lower extremity during weight bearing activities. The purpose of this study was threefold: first, to compare the orientation of the lower extremity during a single leg (SL) squat among male and female athletes; second, to compare the strength of muscle groups in the trunk, hips, and knees between these individuals; and third, to evaluate the association between trunk, hip, and knee strength and the orientation of the knee joint during this activity. Methods: Twenty-four male and 22 female athletes participated in this study. Peak isometric torque was determined for the following muscle actions: trunk flexion, extension, and lateral flexion, hip abduction and external rotation, and knee flexion and extension. The frontal plane projection angle (FPPA) of the knee during a 45SL squat was determined using photo editing software. Results: Males and females moved in opposite directions during the SL squat test (F(1,42) = 5.05, P = 0.03). Females typically moved toward more extreme FPPA during SL squats (P = 0.056), while males tended to move toward more neutral alignment (P = 0.066). Females also generated less torque in all muscle groups, with the exception of trunk extension. The projection angle of the knee during the SL squat test was most closely associated with hip external rotation strength. Conclusion: Using instruments suitable for a clinical setting, females were found to have greater FPPA and generally decreased trunk, hip, and knee isometric torque. Hip external rotation strength was most closely associated with the frontal

Children's pedometer-determined physical activity during the segmented school day.

Abstract: Purpose: To describe the sex-specific patterns of school children's daily pedometer-determined physical (PA) during physical education (PE), recess and lunchtime, and before and after school. Methods: Eighty-one sixth-grade students (28 boys, age = 11.9 ± 0.4 yr, BMI = 18.8 ± 4.1 kg·m-2; 53 girls, 11.8 ± 0.5 yr, BMI = 20.2 ± 4.6 kg·m-2) wore pedometers for four school days and were prompted to record steps accumulated at arrival and departure from school and during pre- and postrecess, lunchtime, and PE class. Results: Boys took significantly (P < 0.001) more steps per day than girls: 16,421 ± 5,444 vs 12,332 ± 3,056 steps per day, and more steps during release time (e.g., before-school ? = 1289 steps, recess ? = 479 steps, lunchtime ? = 608 steps, and after-school ? = 1872 steps) but the same number of steps during structured PE classes (1429 ± 567 vs 1410 ± 445 steps; P = 0.87). Lunchtime PA represented the most important source of daily PA (15-16%) obtained during school hours for both boys and girls, whereas recess accounted for 8-9% and PE class accounted for 8-11% of total steps per day. Regardless, almost half of daily steps taken are attributable to after-school activities. Conclusion: These data provide greater understanding of sex-specific PA patterns and the relative contribution of distinct segments of the school day to school children's total PA.

Effects of resistance training on insulin sensitivity in overweight Latino adolescent males.

Abstract: Purpose: Insulin resistance is thought to be a core defect in the pathophysiology of obesity-related comorbidities in children, such as type 2 diabetes. Exercise training is known to improve insulin resistance and reduce the risk of type 2 diabetes in adults. However, very little is known regarding the effects of exercise on insulin resistance in youth. Therefore, we examined the effects of a 16-wk resistance training exercise intervention on insulin sensitivity in youth at high risk for developing type 2 diabetes. Methods: Twenty-two overweight Latino adolescent males were randomly assigned to either a twice-per-week resistance training group (RT = 11) or a nonexercising control group (C = 11) for 16 wk. Strength was assessed by one-repetition maximum, body composition was quantified by dual-energy x-ray absorptiometry, and insulin sensitivity was determined by the frequently sampled intravenous glucose tolerance test with minimal modeling. Results: Significant increases in upper- and lower-body strength were observed in the RT compared with the C group. The RT group significantly increased insulin sensitivity compared with the C group (P < 0.05), and this increase remained significant after adjustment for changes in total fat mass and total lean tissue mass (P < 0.05). Compared with baseline values, insulin sensitivity increased 45.1 ± 7.3% in the RT group versus -0.9 ± 12.9% in controls (P < 0.01). Conclusion: A twice-per-week 16-wk resistance training program can significantly increase insulin sensitivity in overweight Latino adolescent males independent of changes in body composition.

Serum creatine kinase levels and renal function measures in exertional muscle damage.

Abstract: CLARKSON P. M., A. K. KEARNS, P. ROUZIER, R. RUBIN, and P. D. THOMPSON. Serum Creatine Kinase Levels and Renal Function Measures in Exertional Muscle Damage. Med. Sci. Sports Exerc.,Vol. 38, No. 4, pp. 623–627, 2006. Purpose: Serum creatinekinase (CK)levels arecommonlyusedtojudge theseverityof muscledamageandtodeterminewhento hospitalize patientswho present with symptoms of exertional rhabdomyolysis in order to prevent renal failure. However, no CK standard exists because of the limited information available regarding exercise-induced CK elevation and renal function. This study determined the magnitude of CK elevation and the effect on renal function produced by exercise in a large subject group. Methods: Blood samples were obtained from 203 volunteers who performed 50 maximal eccentric contractions of the elbow flexor muscles. The samples, taken before and 4, 7, and 10 d after exercise, were analyzed for markers of muscle damage (CK, myoglobin (Mb), lactate dehydrogenase, alanine aminotransferase, and aspartate aminotransferase and for measures of renal function (creatinine, blood urea nitrogen, phosphorus, potassium, osmolality, and uric acid). Results: All indicators of muscle damage increased significantly after exercise (P G 0.01). CK levels were 6420, 2100, and 311% above baseline on days 4, 7, and 10 after the exercise, respectively (P G 0.01), and Mb was 1137, 170, and 28% above baseline on days 4, 7, and 10 after exercise, respectively (P G 0.01). Of the 203 participants, 111 had CK values at 4 d postexercise > 2,000 UIL j1 and 51 had values > 10,000 UIL j1 , levels used to diagnose myopathy (e.g., statin myositis) and rhabdomyolysis, respectively. There were no significant

Resistance training and reduction of treatment side effects in prostate cancer patients.

Abstract: Purpose: To examine the effect of progressive resistance training on muscle function, functional performance, balance, body composition, and muscle thickness in men receiving androgen deprivation for prostate cancer. Methods: Ten men aged 59-82 yr on androgen deprivation for localized prostate cancer undertook progressive resistance training for 20 wk at 6- to 12-repetition maximum (RM) for 12 upper- and lower-body exercises in a university exercise rehabilitation clinic. Outcome measures included muscle strength and muscle endurance for the upper and lower body, functional performance (repeated chair rise, usual and fast 6-m walk, 6-m backwards walk, stair climb, and 400-m walk time), and balance by sensory organization test. Body composition was measured by dual-energy x-ray absorptiometry and muscle thickness at four anatomical sites by B-mode ultrasound. Blood samples were assessed for prostate specific antigen (PSA), testosterone, growth hormone (GH), cortisol, and hemoglobin. Results: Muscle strength (chest press, 40.5%; seated row, 41.9%; leg press, 96.3%; P < 0.001) and muscle endurance (chest press, 114.9%; leg press, 167.1%; P < 0.001) increased significantly after training. Significant improvement (P < 0.05) occurred in the 6-m usual walk (14.1%), 6-m backwards walk (22.3%), chair rise (26.8%), stair climbing (10.4%), 400-m walk (7.4%), and balance (7.8%). Muscle thickness increased (P < 0.05) by 15.7% at the quadriceps site. Whole-body lean mass was preserved with no change in fat mass. There were no significant changes in PSA, testosterone, GH, cortisol, or hemoglobin. Conclusions: Progressive resistance exercise has beneficial effects on muscle strength, functional performance and balance in older men receiving androgen deprivation for prostate cancer and should be considered to preserve body composition and reduce treatment side effects.

Effects of supplement timing and resistance exercise on skeletal muscle hypertrophy.

Abstract: CRIBB, P. J., and A. HAYES. Effects of Supplement Timing and Resistance Exercise on Skeletal Muscle Hypertrophy. Med. Sci. Sports Exerc., Vol. 38, No. 11, pp. 1918–1925, 2006. Purpose: Some studies report greater muscle hypertrophy during resistance exercise (RE) training from supplement timing (i.e., the strategic consumption of protein and carbohydrate before and/or after each workout). However, no studies have examined whether this strategy provides greater muscle hypertrophy or strength development compared with supplementation at other times during the day. The purpose of this study was to examine the effects of supplement timing compared with supplementation in the hours not close to the workout on muscle-fiber hypertrophy, strength, and body composition during a 10-wk RE program. Methods: In a single-blind, randomized protocol, resistance-trained males were matched for strength and placed into one of two groups; the PRE-POST group consumed a supplement (1 gIkg j1 body weight) containing protein/creatine/ glucose immediately before and after RE. The MOR-EVE group consumed the same dose of the same supplement in the morning and late evening. All assessments were completed the week before and after 10 wk of structured, supervised RE training. Assessments included strength (1RM, three exercises), body composition (DEXA), and vastus lateralis muscle biopsies for determination of muscle fiber type (I, IIa, IIx), cross-sectional area (CSA), contractile protein, creatine (Cr), and glycogen content. Results: PRE-POST demonstrated a greater (P G 0.05) increase in lean body mass and 1RM strength in two of three assessments. The changes in body composition were supported by a greater (P G 0.05) increase in CSA of the type II fibers and contractile protein content. PRE-POST supplementation also resulted in higher muscle Cr and glycogen values after the training program (P G 0.05). Conclusion: Supplement

Neighborhood environmental factors correlated with walking near home: Using SPACES.

Abstract: Purpose: The physical environment plays an important role in influencing participation in physical activity, although the specific factors that are correlated with different patterns of walking remain to be determined. We examined correlations between physical environmental factors and self-reported walking for recreation and transport near home. Methods: The local neighborhood environments (defined as a 400-m radius from the respondent's home) of 1678 adults were assessed for their suitability for walking. The environmental data were collected during 2000 using the Systematic Pedestrian and Cycling Environmental Scan (SPACES) instrument together with information from other sources. We used logistic regression modeling to examine the relationship between the attributes of the physical environment and the self-reported walking behavior undertaken near home. Results: Functional features were correlated with both walking for recreation (odds ratio (OR) 1.62; 95% confidence interval (CI): 1.20-2.19) and for transport (OR 1.30; 95% CI: 0.97-1.73). A well-maintained walking surface was the main functional factor associated with walking for recreation (OR 2.04; 95% CI: 1.43-2.91) and for transport (OR 2.13; 95% CI: 1.53-2.96). Destination factors, such as shops and public transport, were significantly correlated with walking for transport (OR 1.80; 95% CI: 1.33-2.44), but not recreation. Conclusion: The findings suggest that neighborhoods with pedestrian facilities that are attractive and comfortable and where there are local destinations (such as shops and public transport) are associated with walking near home.

Effects of an entire season on physical fitness changes in elite male handball players.

Abstract: GOROSTIAGA, E. M., C. GRANADOS, J. IBANEZ, J. J. GONZALEZ-BADILLO, and M. IZQUIERDO. Effects of an Entire Season on Physical Fitness Changes in Elite Male Handball Players. Med. Sci. Sports Exerc., Vol. 38, No. 2, pp. 357-366, 2006. Purpose: Fifteen elite male handball players were studied to examine the effects of an entire season of play on physical fitness and throwing velocity. Methods: One repetition maximal bench press (1RMBP), jumping explosive strength, power-load relationship of the leg and arm extensor muscles, 5- and 15-m sprint running time, endurance running, and handball throwing velocity (standing and three-step running throw) were assessed on four times (T1, T2, T3, and T4), during a 45-wk season. Individual volumes and intensities of training and competition were quantified for 11 activities. Results: From T1 to T3, significant increases occurred in free fatty mass (1.4%), 1RMBP (1.9%), standing throwing velocity (6.5%), and three-step throwing velocity (6.2%). No significant changes were observed throughout the season in endurance running and explosive strength-related variables. Significant correlations (P G 0.05-0.01) were observed between strength training time and changes in standing throwing velocity as well as between high-intensity endurance training time and changes in endurance running. In addition, linear inverse relationships were observed between low-intensity endurance training time and changes in muscle power output of the lower extremities. Conclusion: The handball season resulted in significant increases in maximal and specific strength of the upper-extremity but not in the lower-extremity actions. The correlations observed suggest that training time at low intensity should be given less attention, whereas the training stimuli for high-intensity

Impact of physical activity during pregnancy and postpartum on chronic disease risk

Abstract: Research over the past 20 years has focused on the safety of physical activity during pregnancy. Guidelines for health care providers and pregnant/postpartum women have been developed from the results of these studies. The overwhelming results of most studies have shown few negative effects on the pregnancy of a healthy gravida, but rather, be beneficial to the maternal-fetal unit. Recently, researchers have begun to consider the role of maternal physical activity in a more traditional chronic disease prevention model, for both mother and offspring. To address the key issues related to the role of physical activity during pregnancy and postpartum on chronic disease risk, the American College of Sports Medicine convened a Scientific Roundtable at Michigan State University in East Lansing, MI. Topics included preeclampsia, gestational diabetes, breastfeeding and weight loss, musculoskeletal disorders, mental health, and offspring

Concurrent strength and endurance training: from molecules to man.

Abstract: Strength and endurance training produce widely diversified adaptations, with little overlap between them. Strength training typically results in increases in muscle mass and muscle strength. In contrast, endurance training induces increases in maximal oxygen uptake and metabolic adaptations that lead to an increased exercise capacity. In many sports, a combination of strength and endurance training is required to improve performance, but in some situations when strength and endurance training are performed simultaneously, a potential interference in strength development takes place, making such a combination seemingly incompatible. The phenomenon of concurrent training, or simultaneously training for strength and endurance, was first described in the scientific literature in 1980 by Robert C. Hickson, and although work that followed provided evidence for and against it, the interference effect seems to hold true in specific situations. At the molecular level, there seems to be an explanation for the interference of strength development during concurrent training; it is now clear that different forms of exercise induce antagonistic intracellular signaling mechanisms that, in turn, could have a negative impact on the muscle's adaptive response to this particular form of training. That is, activation of AMPK by endurance exercise may inhibit signaling to the protein-synthesis machinery by inhibiting the activity of mTOR and its downstream targets. The purpose of this review is to briefly describe the problem of concurrent strength and endurance training and to examine new data highlighting potential molecular mechanisms that may help explain the inhibition of strength development when strength and endurance training are performed simultaneously.

Active Travel to School and Cardiovascular Fitness in Danish Children and Adolescents

Abstract: PURPOSE: Active travel to school provides an opportunity for daily physical activity. Previous studies have shown that walking and cycling to school are associated with higher physical activity levels. The purpose of this study was to investigate whether the way that children and adolescents travel to school is associated with level of cardiovascular fitness. METHODS: Participants were recruited via a proportional, two-stage cluster sample of schools (N = 25) in the region of Odense, Denmark as part of the European Youth Heart Study (EYHS). Nine hundred nineteen participants (529 children, age 9.7 +/- 0.5 yr; 390 adolescents, age 15.5 +/- 0.4 yr) completed a maximal cycle ergometer test to assess cardiorespiratory fitness (Wmax x kg(-1)). Mode of travel to school was investigated by questionnaire. Physical activity was measured in 531 participants using an accelerometer. Regression analyses with robust standard errors and adjustment for confounders (gender, age, body composition (skinfolds), pubertal status, and physical activity) and the cluster sampling procedure were used to compare fitness levels for different travel modes. Multinomial logistic regression was applied to assess the odds for belonging to quartiles of fitness. RESULTS: Children and adolescents who cycled to school were significantly more fit than those who walked or traveled by motorized transport and were nearly five times as likely (OR 4.8; 95% CI 2.8-8.4) to be in the top quartile of fitness. CONCLUSION: Cycling to school may contribute to higher cardiovascular fitness in young people. KW: SR2S

Technical reliability assessment of three accelerometer models in a mechanical setup.

Abstract: Purpose: To determine which of the three most commonly used accelerometer models has the best intra- and interinstrument reliability using a mechanical laboratory setup. Secondly, to determine the effects that acceleration and frequency have on these reliability measures. Methods: Three experiments were performed. In the first, five each of the Actical, Actigraph, and RT3 accelerometers were placed on a hydraulic shaker plate and simultaneously accelerated in the vertical plane at varying accelerations and frequencies. Six different conditions of varying intensity were used to produce a range of accelerometer counts. Reliability was calculated using standard deviation, standard error of the measurement, coefficient of variation, and intraclass correlation coefficients. In the second and third experiments, 39 Actical and 50 Actigraph accelerometers were put through the same six conditions. Results: Experiment 1 showed poor reliability in the RT3 (intra- and interinstrument CV > 40%). Experiments 2 and 3 clearly indicated that the Actical (CVintra = 0.5%, CVinter = 5.4%) was more reliable than the Actigraph (CVintra = 3.2%, CVinter = 8.6%). Variability in the Actical was negatively related to the acceleration of the condition, whereas no relationship was found between acceleration and reliability in the Actigraph. Variability in the Actigraph was negatively related to the frequency of the condition, whereas no relationship was found between frequency and reliability in the Actical. Conclusion: Of the three accelerometer models measured in this study, the Actical had the best intra- and interinstrument reliability. However, discrepant trends in the variability of Actical and Actigraph counts across accelerations and frequencies preclude the selection of a superior model. More work is needed to understand why accelerometers designed to measure the same thing behave so differently.

Development of novel techniques to classify physical activity mode using accelerometers.

Abstract: Purpose: Use of accelerometers to assess physical activity (PA) is widespread in public health research, but their utility is often limited by the accuracy of data-processing techniques. We hypothesized that more sophisticated approaches to data processing could distinguish between activity types based on accelerometer data, providing a more accurate picture of PA. Methods: Using data from MTI Actigraphs worn by six subjects during four activities (walking, walking uphill, vacuuming, working at a computer), quadratic discriminant analysis (QDA) was performed, and a hidden Markov model (HMM) was trained to recognize the activities. The ability of the new analytic techniques to accurately classify PA was assessed. Results: The mean (SE) percentage of time points for which the QDA correctly identified activity mode was 70.9% (1.2%). Computer work was correctly recognized most frequently (mean (SE) percent correct = 100% (0.01%)), followed by vacuuming (67.5% (1.5%)), uphill walking (58.2% (3.5%)), and walking (53.6% (3.3%)). The mean (SE) percentage of time points for which the HMM correctly identified activity mode was 80.8% (0.9%). Vacuuming was correctly recognized most frequently (mean (SE) percent correct = 98.8% (0.05%)), followed by computer work (97.3% (0.7%)), walking (62.6% (2.3%)), and uphill walking (62.5% (2.3%)). In contrast to a traditional method of data processing that misidentified the intensity level of 100% of the time spent vacuuming and walking uphill, the QDA and HMM approaches correctly estimated the intensity of activity 99% of the time. Conclusion: The novel approach of estimating activity mode, rather than activity level, may allow for more accurate field-based estimates of physical activity using accelerometer data, and this approach warrants more study in a larger and more diverse population of subjects and activities

Prevention of Cold Injuries during Exercise

Abstract: It is the position of the American College of Sports Medicine that exercise can be performed safely in most cold-weather environments without incurring cold-weather injuries. The key to prevention is use of a comprehensive risk management strategy that: a) identifies/assesses the cold hazard; b) identifies/assesses contributing factors for cold-weather injuries; c) develops controls to mitigate cold stress/strain; d) implements controls into formal plans; and e) utilizes administrative oversight to ensure controls are enforced or modified. The American College of Sports Medicine recommends that: 1) coaches/athletes/medical personnel know the signs/symptoms and risk factors for hypothermia, frostbite, and non-freezing cold injuries, identify individuals susceptible to cold injuries, and have the latest up-to-date information about current and future weather conditions before conducting training sessions or competitions; 2) cold-weather clothing be chosen based on each individual's requirements and that standardized clothing ensembles not be mandated for entire groups; 3) the wind-chill temperature index be used to estimate the relative risk of frostbite and that heightened surveillance of exercisers be used at wind-chill temperatures below -27 degrees C (-18 degrees F); and 4) individuals with asthma and cardiovascular disease can exercise in cold environments, but should be monitored closely.

A 3-min all-out test to determine peak oxygen uptake and the maximal steady state

Abstract: Burnley, M., Doust, J., Vanhatalo, A., A 3-min all-out test to determine peak oxygen uptake and the maximal steady state, Medicine & Science in Sports & Exercise. 38(11):1995-2003, November 2006. RAE2008

Shoe Midsole Longitudinal Bending Stiffness and Running Economy, Joint Energy, and EMG

Abstract: Purpose:It has been shown that mechanical energy is dissipated at the metatarsophalangeal (MTP) joint during running and jumping. Furthermore, increasing the longitudinal bending stiffness of the midsole significantly reduced the energy dissipated at the MTP joint and increased jump performa

Validation and calibration of the Actical accelerometer in preschool children.

Abstract: Purpose: Decreased physical activity (PA) is likely a contributor to the rising prevalence of obesity in children. Lack of valid and acceptable measures of PA has been an issue in studies involving young children. The Actical accelerometer is a promising tool for measurement of PA in young children. The purpose of this study was to calibrate and validate the Actical accelerometer for use with 3- to 5-yr-old children. Methods: Eighteen preschool children wore an Actical accelerometer and a Cosmed portable metabolic system during a period of rest, while performing three structured activities in a laboratory setting (used for calibration), and during 20 min each of unstructured indoor and outdoor activities at their preschool (used for cross-validation). Expired respiratory gases were collected, and oxygen consumption was measured on a breath-by-breath basis. Accelerometer data were collected in 15-s intervals. Results: For the accelerometer calibration, the correlation between [latin capital V with dot above]O2 and counts was r = 0.89 across all activities. The calibration equation established was [latin capital V with dot above]O2 = counts[middle dot]15 s-1 (0.01437) + 9.73 (R2 = 0.96, SEE = 3.02). The cut-point for moderate activity (20 mL[middle dot]kg-1[middle dot]min-1) was 715 counts[middle dot]15 s-1 (sensitivity 97.2%, specificity 91.7%), and the cut-point for vigorous activity (30 mL[middle dot]kg-1[middle dot]min-1) was 1411 counts[middle dot]15 s-1 (sensitivity 98.2%, specificity 61.1%). For the cross-validation, the intraclass correlation coefficient was R = 0.59 and the Spearman correlation coefficient was R = 0.80 (P < 0.001) between measured and predicted [latin capital V with dot above]O2. Percentage of agreement, kappa, and modified kappa for moderate activity were 0.73, 0.40, and 0.46, respectively. For vigorous activity, the same measures were 0.85, 0.26, and 0.71, respectively. Conclusion: The Actical accelerometer is a valid tool for measuring PA in young children

Predictive validity of three ActiGraph energy expenditure equations for children

Abstract: Purpose This Study evaluated the predictive validity of three previously published ActiGraph energy expenditure (EE) prediction equations developed for children and adolescents. Methods A total of 45 healthy children and adolescents (mean age: 13.7 +/- 2.6 yr) completed four 5-min activity trials (normal walking. brisk walking, easy running, and fast running) in ail indoor exercise facility. During each trial, participants were all ActiGraph accelerometer oil the right hip. EE was monitored breath by breath using the Cosmed K4b(2) portable indirect calorimetry system. Differences and associations between measured and predicted EE were assessed using dependent t-tests and Pearson correlations, respectively. Classification accuracy was assessed using percent agreement, sensitivity, specificity, and area under the receiver operating characteristic (ROC) curve. Results None of the equations accurately predicted mean energy expenditure during each of the four activity trials. Each equation, however, accurately predicted mean EE in at least one activity trial. The Puyau equation accurately predicted EE during slow walking. The Trost equation accurately predicted EE during slow running. The Freedson equation accurately predicted EE during fast running. None of the three equations accurately predicted EE during brisk walking. The equations exhibited fair to excellent classification accuracy with respect to activity intensity. with the Trost equation exhibiting the highest classification accuracy and the Puyau equation exhibiting the lowest. Conclusions These data suggest that the three accelerometer prediction equations do not accurately predict EE on a minute-by-minute basis in children and adolescents during overground walking and running. The equations maybe, however, for estimating participation in moderate and vigorous activity.