bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of the self-contained breathing apparatus on left-ventricular function at rest and during graded exercise
Authors: Mayne Jonathan R. , Haykowsky Mark J. , Nelson Michael D. , Hartley Timothy C. , Butcher Scott J. , Jones Richard L. , Petersen Stewart R. 
Published: September 2009

The purpose of this study was to examine the effects of the self-contained breathing apparatus (SCBA) on left-ventricular (LV) function at rest and during mild- to moderate-intensity exercise, using 2-dimensional echocardiography. Twenty-three healthy male volunteers exercised on a stair-climber at work rates equivalent to 50%, 60%, 70%, and 80% of peak oxygen consumption. Esophageal pressure LV diastolic and systolic cavity areas, and myocardial areas were acquired during the final minute of each stage of exercise. As expected, the esophageal pressure response during SCBA breathing revealed significantly lower (more negative) inspiratory pressures and higher (more positive) expiratory pressures and, consequently, higher pressure swings, than free breathing (FB). End-diastolic cavity area (EDCA) and end-systolic cavity area (ESCA) were lower with the SCBA than with FB. LV contractility was higher (p < 0.05) with the SCBA, which can partially be explained by decreases in end-systolic wall stress. Therefore, the SCBA was found to decrease LV preload during moderate-intensity exercise, but did not negatively affect stroke area because of a similar reduction in ESCA.
Greater daily leisure time physical activity is associated with lower chronic disease risk in adults with spinal cord injury
Authors: Buchholz Andrea C. , Martin Ginis Kathleen A. , Bray Steven R. , Craven B. Catharine , Hicks Audrey L. , Hayes Keith C. , Latimer Amy E. , McColl Mary Ann , Potter Patrick J. , Wolfe Dalton L. 
Published: September 2009

The objective of this study was to examine the relationship between leisure time physical activity (LTPA) and common risk factors for cardiovascular disease (CVD) and type 2 diabetes in community-dwelling adults with chronic spinal cord injury (SCI). LTPA was measured using the Physical Activity Recall Assessment for People with SCI in 76 men and women with chronic (≥1 year) paraplegia or tetraplegia, living in or near Hamilton, Ontario. Body mass index (BMI), waist circumference, body composition (fat mass (FM) and fat-free mass (FFM)), blood pressure, and biochemical data were collected. Thirty-seven percent (n = 28 participants) were inactive, reporting no LTPA whatsoever, and were compared with an equal-sized group consisting of the most active study participants (≥25 min of LTPA per day). After adjusting for significant covariates, BMI (18.7%), %FM (19.4%), and C-reactive protein (143%) were all lower, and %FFM was higher (7.2%), in active participants (all p ≤ 0.05). Ten percent of active participants vs. 33% of inactive participants were insulin resistant (p = 0.03). Waist circumference (17.6%) and systolic blood pressure (15.3%) were lower in active vs. inactive participants with paraplegia (both p ≤ 0.05), but not tetraplegia. In conclusion, greater daily LTPA is associated with lower levels of selected CVD and type 2 diabetes risk factors in individuals living with SCI. Whether this relationship translates into a lower incidence of these chronic diseases has yet to be determined.
Preinfection aerobic treadmill training improves resistance against Trypanosoma cruzi infection in mice
Authors: Schebeleski-Soares Cristiano , Occhi-Soares Roberta Cristhiany , Franzói-de-Moraes Solange Marta , de Oliveira Dalálio  Márcia Machado , Almeida Felipe Natali , de Ornelas Toledo Max Jean , de Araújo Silvana Marques 
Published: September 2009

Exercise performed before infections has been linked to improvement of the immune response against infections. The purpose of this study was to evaluate the influence of preinfection moderate-intensity treadmill training on acute Trypanosoma cruzi infection in mice. Ninety-nine female BALB/c mice were divided into 4 groups, as follows: training + infection (T+I) (n = 41); no training + infection (NT+I) (n = 38); training + no infection (T+NI) (n = 10); and no training + no infection (NT+NI) (n = 10). The exercise program for trained groups was carried out on a motorized treadmill for 8 weeks. Infected groups were inoculated with the Y strain of T. cruzi. Infectivity, prepatent period, patent period, parasitemia peak, mortality, survival time, weight, food intake, tumor necrosis factor-alpha serum levels, and peritoneal macrophage hydrogen peroxide production were evaluated. We found that preinfection training induced statistically significant reductions in parasitemia peak (p < 0.03) and weight loss (p < 0.04). However, no statistically significant differences were found for the other parameters evaluated when trained and nontrained infected groups were compared. We conclude that preinfection aerobic training induces some improvement in the immune response to T. cruzi infection in female BALB/c mice.
Estimating leisure-time physical activity energy expenditure in the Canadian population: a comparison of 2 methods
Authors: Bryan Shirley N. , Katzmarzyk Peter T. 
Published: September 2009

The purpose of this study was to determine the impact of 2 different calculation methods for total leisure-time physical activity energy expenditure (LTPAEE) and LTPAEE from different intensity activities on the classification of level of physical activity in the population. Nationally representative cross-sectional data from the Canadian Community Health Survey Cycle 4.1 (2007) were used for this study (N = 64 397). LTPAEE was calculated using a metabolic equivalent (MET) value of 4.0 for all activities in the “other activity” category for method 1 (currently employed by Statistics Canada) and using activity-specific MET values for method 2. The weighted prevalence and 95% confidence intervals of active (≥3 kcal·kg–1·day–1 (kkd)), moderately active (1.5–2.9 kkd), and inactive (<1.5 kkd) were determined for each method by demographic characteristics. The agreement between the 2 methods was assessed overall, and for light, moderate, and vigorous activities. There was no difference between methods in the proportion classified as active, moderately active, or inactive for any of the subgroups studied and there was no difference in the distribution or mean LTPAEE between methods. However, assessment of the agreement showed a large number of outliers and a tendency to underestimate LTPAEE from light and vigorous activities while overestimating LTPAEE from moderate activities at the individual level. The results of this study should be considered when performing inferential statistics on the relationship between physical activity and health outcomes.
The effect of an inverted body position on lower limb muscle force and activation
Authors: Paddock Natasha , Behm David 
Published: September 2009

Complete inversion of the body in a seated position may occur in exceptional circumstances such as in overturned vehicles and during military maneuvers, with direct consequences on health and fatalities. However, the physiological responses to this condition have not been published previously. The purpose of this study was to compare neuromuscular responses to upright and inverted seated positions. Sixteen subjects performed maximal voluntary contraction (MVC) and submaximal voluntary contraction knee extensions (25%, 50%, and 75% of MVC) under upright and inverted seated positions. Force, quadriceps activation as measured by the interpolated twitch technique, electromyographic (EMG) activity of the vastus lateralis, and semitendenosis and evoked contractile properties of the quadriceps were measured. Results demonstrated that MVC force (p = 0.01, ↓6.1%) and vastus lateralis EMG (p = 0.009, ↓29.6%) decreased in the inverted compared with the upright position. Instantaneous strength in the inverted position was 19.3% lower than in the upright position (p = 0.005). Heart rate and diastolic and systolic blood pressures were 12.4%, 9.2%, and 10.7% lower (p < 0.0001), respectively, in the inverted position. In conclusion, a seated inverted position impaired MVC force and EMG activity, which could not be attributed to evoked contractile properties. The changes in heart rate and blood pressure may suggest inversion-induced alterations to the sympathetic nervous stimulation.
Sex alters impact of repeated bouts of sprint exercise on neuromuscular activity in trained athletes
Authors: Billaut François , Smith Kurt 
Published: September 2009

This study characterized the effect of sex on neuromuscular activity during repeated bouts of sprint exercise. Thirty-three healthy male and female athletes performed twenty 5-s cycle sprints separated by 25 s of rest. Mechanical work and integrated electromyograhs (iEMG) of 4 muscles of the dominant lower limb were calculated in every sprint. The iEMG signals from individual muscles were summed to represent overall electrical activity of these muscles (sum-iEMG). Neuromuscular efficiency (NME) was calculated as the ratio of mechanical work and sum-iEMG for every sprint. Arterial oxygen saturation was estimated (SpO2) with pulse oximetry throughout the protocol. The sprint-induced work decrement (18.9% vs. 29.6%; p < 0.05) and sum-iEMG reduction (11.4% vs. 19.4%; p < 0.05) were less for the women than for the men. However, the sprints decreased NME (10.1%; p < 0.05) and SpO2(3.4%; p < 0.05) without showing sex dimorphism. Changes in SpO2and sum-iEMG were strongly correlated in both sexes (men, R2= 0.87; women, R2= 0.91; all p < 0.05), although the slope of this relationship differed (6.3 ± 2.9 vs. 3.8 ± 1.6, respectively; p < 0.05). It is suggested that the sex difference in fatigue during repeated bouts of sprint exercise is not likely to be explained by a difference in muscle contractility impairment in men and women, but may be due to a sex difference in muscle recruitment strategy. We speculate that women would be less sensitive to arterial O2desaturation than men, which may trigger lower neuromuscular adjustments to exhaustive exercise.
Effects of ovariectomy and resistance training on MMP-2 activity in skeletal muscle
Authors: Prestes Jonato , de Cássia Marqueti Rita , Shiguemoto Gilberto Eiji , Leite Richard Diego , Pereira Guilherme Borges , Selistre-de-Araújo Heloisa Sobreiro , Baldissera Vilmar , de Andrade Perez Sérgio Eduardo 
Published: September 2009

Matrix metallopeptidases (MMPs) are crucial to the maintenance of healthy tissue. The aim of this study was to investigate MMP-2 activity in gastrocnemius, soleus, tibialis anterior (TA), and extensor digitorium longus (EDL) muscle after resistance training in ovariectomized rats. Wistar adult female rats were grouped into 7 groups (n = 10 per group): sedentary (Sed-Intact); ovariectomized sedentary (Sed-Ovx); pseudo-ovariectomized sedentary (Sed-Pseudo); acute exercise (AcuteEx-Intact); ovariectomized acute exercise (AcuteEx-Ovx); strength trained (ChronicEx-Intact); and ovariectomized strength trained (ChronicEx-Ovx). A 12-week resistance training period, during which the animals climbed a 1.1-m vertical ladder with weights secured to their tails, was used. The sessions were performed once every 3 days, with 4–9 climbs and 8–12 dynamic movements per climb. The MMP-2 activity was analyzed by zymography. There was higher MMP-2 activity in soleus muscle in the ChronicEx-Intact and ChronicEx-Ovx groups, and lower MMP-2 activity in the AcuteEx-Ovx group, compared with the Sed-Intact group (p ≤ 0.05). The Sed-Ovx and ChronicEx-Ovx groups presented lower MMP-2 activity than the Sed-Intact group in TA. There was higher MMP-2 activity in AcuteEx-Intact and the AcuteEx-Ovx compared with the Sed-Intact and Sed-Ovx in TA, respectively (p ≤ 0.05). In TA and EDL, training increased MMP-2 activity in the Sed-Intact group. No statistically significant alterations were observed for gastrocnemius muscle. Strength training increases MMP-2 activity in soleus, TA, and EDL muscle, which may be important for muscle remodeling. Ovariectomy downregulates MMP-2 in TA and EDL, which may compromise muscle function.
Physical activity of children in family child care
Authors: Temple Viviene A. , Naylor Patti-Jean , Rhodes Ryan E. , Higgins Joan Wharf 
Published: September 2009

Physical activity was monitored for 65 boys and girls, during family child care, using accelerometry. Average accelerometer wear time was 7.0 h (SD = 0.83), and average counts per epoch were 104.6 (SD = 31.6). Mean minutes per hour of moderate-vigorous physical activity and sedentary behaviour were 1.76 min (SD = 0.90) and 39.49 min (SD = 4.50), respectively. The very low levels of moderate-vigorous physical activity suggest that the young children in this study may be insufficiently active during child care.
Age- and sex-associated differences in isokinetic knee muscle endurance between young children and adults
Authors: De Ste Croix Mark B.A. , Deighan Martine A. , Ratel Sebastien , Armstrong Neil 
Published: September 2009

The purpose of this study was to examine the age- and sex-associated differences of repeated isokinetic knee extension and flexion. Fifty one participants, 30 young children (16 boys and 14 girls; aged 11 and 12 years) and 21 adults (9 males and 12 females; aged 18–35 years), agreed to participate in the study. Isokinetic concentric peak knee extension (PET) and flexion (PFT) torque were measured using a calibrated Biodex System 3. Participants performed 4 concentric extension–flexion cycles with maximum effort; after a 2 min rest, 50 continuous concentric cycles were performed at 1.56 rad·s–1. Total work of the extensors (WKEX) and flexors (WKFL) for the complete 50 repetitions was recorded. Average peak torque and average work for the first and last 3 repetitions were calculated to represent the percentage decline in torque and work. There were no significant differences between groups in the peak torque generated during the pretrial and endurance task, suggesting that participants gave a maximal effort at the start of the endurance task. There was a significant interaction effect in the total work done for both extensors and flexors, with adult males producing the greatest amount of work (6622 and 3444 J, respectively). When total work was divided by body mass, there were no significant sex effects, only main effects for group. The percentage decline for PET (40% vs. 60%), PFT (50% vs. 65%), WKET(43% vs. 61%), and WKFL(60% vs. 69%) demonstrated significant main effects for group, with greater fatigue in adults. We found no significant sex effect for fatigue. This study concludes that females do not resist fatigue from repeated isokinetic muscle actions to a greater extent than males, and that the greater fatigue in adults than in children is probably a product of greater initial torque production and work performed.
Postexercise rehydration in man: the effects of carbohydrate content and osmolality of drinks ingested ad libitum
Authors: Evans Gethin H. , Shirreffs Susan M. , Maughan Ronald J. 
Published: September 2009

The effectiveness of different carbohydrate solutions in restoring fluid balance in situations of voluntary fluid intake has not been examined previously. The effect of the carbohydrate content of drinks ingested after exercise was examined in 6 males and 3 females previously dehydrated by 1.99 ± 0.07% of body mass via intermittent exercise in the heat. Beginning 30 min after the cessation of exercise, subjects drank ad libitum for a period of 120 min. Drinks contained 31 mmol·L–1 Na+ as NaCl and either 0%, 2%, or 10% glucose with mean ± SD osmolalities of 74 ± 1, 188 ± 3, and 654 ± 4 mosm·kg–1, respectively. Blood and urine samples were collected before and after exercise, midway through rehydration, and throughout a 5 h recovery period. Total fluid intake was not different among trials (0%: 2258 ± 519 mL; 2%: 2539 ± 436 mL; 10%: 2173 ± 252 mL; p = 0.173). Urine output was also not different among trials (p = 0.160). No differences among trials were observed in net fluid balance or in the fraction of the ingested drink retained. In conclusion, in situations of voluntary fluid intake, hypertonic carbohydrate-electrolyte solutions are as effective as hypotonic carbohydrate-electrolyte solutions at restoring whole-body fluid balance.
Relationship of blood pressure, behavioral mood state, and physical activity following caffeine ingestion in younger and older women
Authors: Arciero Paul J. , Ormsbee Michael J. 
Published: September 2009

The purpose of this study was to examine the age-related differences in blood pressure, heart rate, and behavioral mood state after caffeine ingestion in younger and older women. Using a placebo-controlled, double-blind design, 10 younger (Y; 18–22 years) and 10 older (O; 50–67 years) healthy women who were moderate consumers of caffeine (self-reported mean intake: Y, 139 ± 152 mg·day–1; O, 204 ± 101 mg·day–1) were investigated. All volunteers were characterized for fasting plasma glucose, insulin, free-fatty acids and caffeine levels, body composition, cardiovascular fitness, physical activity, and energy intake. Before and after placebo and caffeine ingestion (5 mg·kg–1 fat-free mass; ~208–270 mg) test days, the following variables were measured in all subjects: plasma caffeine levels, heart rate, blood pressure, and behavioral mood state. Results showed that, following caffeine ingestion: (i) both systolic and diastolic blood pressure (SBP and DBP, respectively) increased significantly (p < 0.05) in the older women (SBP, 128.4 ± 14.2 vs. 132.1 ± 13.0 mm Hg (3%); DBP, 80.2 ± 6.9 vs. 83.4 ± 7.5 mm Hg (4%), whereas only DBP increased in the youger women (67.1 ± 4.7 vs. 69.9 ± 5.4 mm Hg (4.2%); p < 0.05); (ii) heart rate decreased significantly (Y, 59.2 ± 8.7 to 53.9 ± 10.6 beats·min–1 (p < 0.05); O, 61.9 ± 9.2 to 59.2 ± 8.4 beats·min–1 (p < 0.05)) in both groups; and (iii) self-reported feelings of tension and vigor increased and feelings of fatigue decreased (p < 0.05) in younger women, whereas depression decreased (p ≤ 0.05) in older women. Self-reported level of physical activity was inversely related to change in DBP following caffeine ingestion in younger women. In conclusion, blood pressure response is augmented and subjective feelings of behavioral mood state are attenuated to a greater degree in older than in younger women following acute caffeine ingestion. Less physically active younger women are more vulnerable to the pressor response to caffeine than more active younger women. It should be noted that these findings are limited to moderate consumers of caffeine who abstained for 48 h prior to testing, and who ingested caffeine in pill form (~240 mg).
Physiological correlates of 2-mile run performance as determined using a novel on-demand treadmill
Authors: Tolfrey Keith , Hansen Simon A. , Dutton Katie , McKee Tom , Jones Andrew M. 
Published: September 2009

The purpose of this study was to assess the reproducibility of an on-demand motorised treadmill to measure 2-mile (3.2 km) race performance and to examine the physiological variables that best predict this free-running performance in active men. Twelve men (mean (SD): age, 28 (9) years; stature, 1.79 (0.05) m; body mass, 72 (9) kg) completed the study in which maximum oxygen uptake (VO2 max), running economy, and running speed at VO2 max (vVO2 max), lactate threshold (vLT), and 4 mmol·L–1 fixed blood lactate concentration (v4) were measured. Subsequently, the maximal lactate steady state (MLSS) was identified using a series of 30-min treadmill runs. Finally, each participant completed a 2-mile running performance trial on 2 separate occasions, using an on-demand treadmill that adjusts belt speed according to the participant’s position on the moving belt. The average 2-mile run speed was 15.7 (SD, 1.9) km·h–1, with small individual differences between repeat-performance trials (intraclass correlation coefficient = 0.99, 95% CI 0.953 to 0.996; standard error of measurement as coefficient of variation = 1.5%, 95% CI 1.0% to 2.5%). Bivariate regression analyses identified VO2 max, vVO2 max, VO2 (mL·kg–1·min–1) at MLSS, vLT, v4, and velocity at MLSS (vMLSS) as the strongest individual predictor variables (r2 = 0.69 to 0.87; standard error of the estimate = 1.08 to 0.72 km·h–1) for 2-mile running performance. The vLT and vMLSS explained 85% and 87% of the variance in running performance, respectively, suggesting that there is considerable shared variance between these parameters. In conclusion, the on-demand treadmill system provided a reliable measure of distance running performance. Both vLT and vMLSS were strong predictors of 2-mile running performance, with vMLSS explaining marginally more of the variance.
A hydrodynamic approach to address Yamuna riverbed development in Delhi
Authors: Vijay Ritesh , Sargaonkar Aabha , Gupta Apurba 
Published: September 2009

Most critical flood problems occur in urban areas where values at risk are higher and damages tend to be heavier. In the present study, a hydrodynamic simulation of the river Yamuna has been generated under different designated flood flows to delineate the land availability under existing and modified riverbed geometry including channel dredging and riverbed dressing. Flood flows for various return periods, namely once in 10, 25, 50, and 100 years are estimated based on the past 41 years of recorded data using flood frequency analysis. The model set up considered the river stretch of 23 km from the Wazirabad barrage upstream to the Okhla barrage downstream, which includes manmade structures like bridges and barrages. Model calibration is achieved by comparing the water surface elevations with observed data at various downstream gauge stations. The land availability based on submergence scenarios under existing riverbed condition is estimated to be 1147.6, 873.1, and 762.6 ha, respectively, for 10, 50, and 100 year return flood. Various simulations are generated including channel dredging and riverbed dressing to obtain safe height and safe width for dressing the riverbed. The modified river geometry considered channel dredging in 750 to 1350 m width, and riverbed dressing for safe height and width in three levels in various sections. The land availability under this scenario is estimated to be 2197, 1129, and 545 ha for 10, 50, and 100 year return flood, respectively. It is proposed to dress the riverbed by utilizing the material obtained from channel dredging in three levels to maintain the transverse and longitudinal slope, river morphology, and river system. Developmental planning in the riverbed may include utilization of land at three levels for various purposes such as playgrounds, nursery, etc. However, it is suggested that the feasibility study of the project requires detailed engineering including slope stability prior to implementation of the riverbed development.