bluuebunny/crossref_metadata_2025 huggingface dataset:
Blunted Cardiac Autonomic Responsiveness to Hypoxemic Stress in Healthy Older Adults
Authors: Lucy S. Deborah , Kowalchuk John M. , Hughson Richard L. , Paterson Donald H. , Cunningham David A.
Published: June 2009

Supine resting cardiac dynamics and responses to steady-state hypoxemia were investigated in six healthy older (59-72 yrs) adults using coarse-graining spectral analysis of heart rate variability (HRV) and were compared to six young (22-29 yrs) adults studied previously (Lucy et al., 2000). End-tidal carbon dioxide pressure (PETCO2) was clamped at 1-2 mmHg above the usual resting value for 11 min of euoxia (PETO2100 mmHg), followed by 22 min of hypoxia (PETO2 55 mmHg). During euoxia, vagally mediated harmonic and fractal power of HRV of older adults was minimal. Hypoxia induced an increase in ventilation, p < 0.01, and heart rate, p < 0.05. The heart rate increase (mean ± SE) of 0.23 ± 0.08 beats•min−1 per 1% decrease in arterial O2 saturation was 25% of that demonstrated previously by young subjects, p < 0.001. In older adults, HRV spectral power remained unchanged during hypoxia, providing further evidence of an age-related blunting of cardiac autonomic function. Key words: heart rate variability, coarse-graining spectral analysis, cardiac vagal control, acute isocapnic hypoxia, dynamic end-tidal forcing (DEF) technique
Critical Velocity and Anaerobic Distance Capacity in Prepubertal Children
Authors: Berthoin Serge , Baquet Georges , Dupont Gregory , Blondel Nicolas , Mucci Patrick
Published: June 2009

This study was designed to calculate the critical velocity (vcrit) and anaerobic distance capacity (ADC) of prepubescent children for running events. Thirty-four prepubertal children underwent a graded field test to exhaustion in order to determine peak oxygen uptake (peak [Formula: see text]) and maximal aerobic velocity (MAV). Then, in random order, they performed five runs to exhaustion (tlim) at relative velocities corresponding to 90, 95, 100, 105, and 110% of MAV. The linear relationships between distance limit (dlim) and tlim were calculated in order to determine vcrit (slope of the relationship) and ADC (intercept). Very high individual coefficients of determination were found between dlim and tlim (0.98 < r2 < 0.99; p < 0.001). The vcrit was significantly correlated with peak [Formula: see text] (r = 0.73; p < 0.001). However, no relationship was found between ADC and the maximal accumulated oxygen deficit. In conclusion, our results indicated that, for children, the relationship between dlim and tlim could be calculated with tlim ranging from 2 to 10 min, and that vcrit is a good indicator of the aerobic fitness of children. Nevertheless, further studies will have to be conducted to validate the use of ADC as an indicator of children's anaerobic capacity. Key words: aerobic power, anaerobic capacity, comparison, model, performance
Overloaded Training Increases Exercise-Induced Oxidative Stress and Damage
Authors: Palazzetti Stephane , Richard Marie-Jeanne , Favier Alain , Margaritis Irene
Published: June 2009

We hypothesized that overloaded training (OT) in triathlon would induce oxidative stress and damage on muscle and DNA. Nine male triathletes and 6 male sedentary subjects participated in this study. Before and after a 4-week OT, triathletes exercised for a duathlon. Blood ratio of reduced vs. oxidized glutathione (GSH/GSSG), plasma thiobarbituric acid reactive substances (TEARS), leukocyte DNA damage, creatine kinase (CK), and CK-MB mass in plasma, erythrocyte superoxide dismutase (SOD) activity, erythrocyte and plasma glutathione peroxidase (GSH-Px) activities, and plasma total antioxidant status (TAS) were measured before and after OT in pre- and postexercise situations. Triathletes were overloaded in response to OT. In rest conditions, OT induced plasma GSH-Px activity increase and plasma TAS decrease (both p < 0.05). In exercise conditions, OT resulted in higher exercise-induced variations of blood GSH/GSSG ratio, TBARS level (both p < 0.05), and CK-MB mass (p < 0.01) in plasma; and decreased TAS response (p < 0.05). OT could compromise the antioxidant defense mechanism with respect to exercise-induced response. The resulting increased exercise-induced oxidative stress and further cellular susceptibility to damage needs more study. Key words: lipid peroxidation, leukocyte DNA damage, antioxidant, triathlon
Activity Patterns During Pregnancy
Authors: Mottola Michelle F. , Campbell M. Karen
Published: June 2009

The purpose of this study was to investigate determinants of the activity patterns of women prior to pregnancy and factors associated with quitting activities during pregnancy. Methods: These data arose from a study designed to look at the impact of exercise in pregnancy on birth weight (Campbell and Mottola, 2001). This secondary analysis explored relationships between subject characteristics and exercise patterns via a self-completed questionnaire. Univariable and multivariable odds ratios were estimated using logistic regression. Multivariable models used backward stepwise variable selection. Results: A total of 853 women agreed to participate and 529 women (62%) returned completed questionnaires. Of these, 369 (70%) and 258 (49%) engaged in a structured exercise program before pregnancy and in Trimester 3, respectively. Factors associated with engaging in regular structured exercise prior to pregnancy included: postsecondary education (OR = 1.50; 0.98, 2.30), no children (OR = 2.44; 1.56, 3.82), nonsmoker (OR = 1.84; 1.18, 2.88), and involvement in regular recreational activities (OR = 3.07; 1.81, 5.20). During pregnancy, all categories of activity decreased except walking, which increased by Trimester 3. Factors associated with quitting a regular structured exercise program by Trimester 3 were: having children (OR = 1.67; 1.05, 2.67), a prepregnancy BMI of >= 25 (OR = 1.79; 1.04, 3.13), and higher weight gain. Implications: Community programs that encourage active living should address these factors. Key words: active living, pregnant, community walking programs
Increase in Serum S100B Protein Level After a Swimming Race
Authors: Dietrich Marcelo O. , Tort Adriano B. , Schaf Débora V. , Farina Marcelo , Gonçalves Carlos A. , Souza Diogo O. , Portela Luis V.
Published: June 2009

Physical activity has been shown to be a beneficial stimulus to the central and peripheral nervous systems. The S100B is a cytokine physiologically produced and released predominantly by astrocytes on the central nervous system (CNS). In order to study the possible influence of a nonimpact exercise on S100B serum levels, we measured this protein serum level after a 7,600-meter swimming race. We observed an increase in S100B levels in athletes post-race compared with their baseline values, pointing to a potential acute influence of physical exercise on serum S100B levels not related with CNS injury. We discuss this result and emphasize the possible central and peripheral origins of S100B serum levels. Key words: exercise, serotonin, astrocytes
Effet de 4 semaines d'entraînement sur le temps limite à max
Authors: Heubert Richard , Bocquet Valéry , Koralsztein Jean Pierre , Billat Véronique
Published: June 2009

The purpose of this study was to examine the effect of 4 weeks training in running on the time spent at [Formula: see text]max (tlim [Formula: see text]max). Eight athletes carried out, before and after an aerobic training, an incremental and five exhaustive tests at 90, 95, 100, 115% v [Formula: see text]max and at the critical power at [Formula: see text]max (CV'; slope of the linear relation between the tlim [Formula: see text]max and the distance limit at [Formula: see text]max). This training did not significantly improve [Formula: see text]max (p = 0.17) or tlim [Formula: see text]max (p = 0.72). However, the "tlim [Formula: see text]max-intensity" curve was shifted toward the right, meaning that the athlete had to run at a higher intensity after training to obtain the same tlim [Formula: see text]max. Tlim [Formula: see text]max at CV' before training was significantly higher than tlim [Formula: see text]max at 90, 95, 100, and 115%v[Formula: see text]max(p < 0.05). This training increased CV' in absolute value (13.9 ± 1.3 vs. 14.9 ± 1.2 km h−1, p < 0.05; n = 6) but not in relative value (86 ± 4 vs. 86 ± 5% v [Formula: see text]max; p = 0.9). In conclusion, in spite of the shift of the "tlim [Formula: see text]max-intensity" curve, tlim [Formula: see text]max was not significantly increased by this training. Furthermore, CV' allowed subjects to spend the longest time of exercise at [Formula: see text]max during a continuous exercise with constant speed, but CV', expressed in % v [Formula: see text]max, did not improve with this training. Key words: time limit at [Formula: see text]max, time to reach [Formula: see text]max, performance, oxygen kinetics
Potential Interactions Among Vascular and Muscular Functional Compartments During Active Hyperemia
Authors: Barclay Jack K. , Murrant Coral L. , Woodley Nancy E. , Reading Stacey A.
Published: June 2009

The increase in blood flow that accompanies the start of contractions (active hyperemia) is a complex phenomenon involving a fast phase in which blood flow increases quickly and then slows or decreases (seek phase) before stabilizing at a flow corresponding to the metabolic rate (matched phase). This pattern of blood flow change involves contributions from a flow-induced increase in flow, a response to short periods of occlusion or partial occlusion due to force generated by the muscle contraction, and metabolism. Even denervated, the vascular bed, which consists of endothelial cells, vascular smooth muscle cells, and an adventitial layer that has significant secretory potential, is able to coordinate the response pattern. Within the vascular wall, communication is possible bidirectionally across the wall and also along the wall in a retrograde or upstream direction. The signals involved, which range from endothelial cell products such as nitric oxide and endothelin to adenosine, a skeletal muscle metabolite, appear to be situation- and time-dependent. In addition to the communication potential within and along the vascular wall, signals from the vascular system are able to exert inotropic effects on mammalian skeletal muscle. Key words: bidirectional signaling, postcontraction hyperemia, flow-induced flow changes, signal plasticity
Strenuous Exercise Increases Plasmatic and Urinary Leukotriene E4 in Cyclists
Authors: Caillaud Corinne , Creff Cyrille Le , Legros Patrick , Denjean André
Published: June 2009

The purpose of this study was to investigate plasma and urinary levels of leukotriene (LT) and the changes in pulmonary function induced by strenuous exercise in highly trained cyclists (HT) with mild exercised-induced hypoxemia (EIH). Method: Nine HT and five untrained subjects (UT) performed a 30-min exercise at 78% of their [Formula: see text] Leukotriene E4 (LTE4) was assayed in plasma and urine. Pulmonary function tests and pulmonary diffusion capacity (DLCO) were examined before and after exercising. Ear arterialized blood gases were assessed at rest and during exercise. Results: The mean drop in partial oxygen pressure was 15 mmHg in HT during exercise; and the DLCO decreased by 7.5% following exercise. No significant changes were found in forced vital capacity or forced expiratory flows. LTE4 levels increased significantly in HT following exercise: urinary LTE4 was 42.9 ± 6.3 ng•mmol−1 creatinine at rest and 66.3 ± 11.9 ng•mmol−1 creatinine 2 hrs after exercise, and plasma LTE4 rose from 528 ± 91 pg•mL−1 at rest to 897 ± 123 pg•mL−1 after exercise. By contrast, urinary LTE4 level was unchanged in the UT group. Among the HT group, there was no significant correlation between urinary LTE4 changes and PO2, air flow rates, or DLCO changes. Conclusion: These results suggest that strenuous exercise induces an increase of LTE4 release in highly trained cyclists with mild EIH. These changes in LTE4 levels were not related to significant impairment of lung function. Key words: athletes, hypoxemia, pulmonary function, leukotrienes
The Effect of an Intercollegiate Soccer Game on Maximal Power Performance
Authors: Hoffman Jay R. , Nusse Victoria , Kang Jie
Published: June 2009

The effect of a competitive soccer match on maximal power performance was assessed on 19 members of an NCAA Division III female soccer team. Performance testing occurred within 24 hours prior to the game (Pre), immediately postgame (IP), and 24 hours postgame (24P). Each subject performed a squat jump (SJ) and countermovement jump (CMJ). Comparisons between starters (n = 10) and nonstarters (n = 9) revealed no between-group differences in power performance at IP, but starters were found to have significantly lower power and force measures at 24P than nonstarters. There were significant correlations between playing time and peak force during the SJ at 24P (r = −0.47), and between playing time and peak power during the SJ at IP (r = −0.57) and 24P (r = −0.51), and during the CMJ at IP (r = −0.49). Comparisons between different positions revealed no differential fatigue patterns. Results of this study show that power performance appears to be maintained for the duration of a soccer match but declines significantly within 24 hours after the match. Position played does not appear to affect performance decrements seen at 24 hours postmatch. Key words: athletes, sport, exercise, female
Influence of Intensive Cycling Training on Heart Rate Variability During Rest and Exercise
Authors: Leicht Anthony S. , Allen Graham D. , Hoey Andrew J.
Published: June 2009

The current study examined whether changes in heart rate variability (HRV) following intensive cycling training contribute to the mechanism of training-induced bradycardia. Thirteen healthy untrained subjects, ages 18-27 years, underwent recordings of heart rate (HR) and [Formula: see text] before and after 8 weeks of cycling, 25-60 min/day, 5 days/week at > 80% maximum HR (HRmax). Heart rate recordings were obtained during supine rest and submaximal exercise and were analysed for the following components of HRV: low frequency (LF, 0.041-0.15 Hz); high frequency (HF, 0.15-0.40 Hz); LF/HF ratio and total power (TP, 0-0.40 Hz). At posttraining, VO2max was significantly increased while HR was significantly reduced at rest and all absolute exercise work rates. Training-induced lower HR was accompanied by significantly greater HF and TP during rest as well as LF, HF, and TP during all absolute exercise work rates. Posttraining HR and the majority of HRV measures were similar to pretraining values at the same relative exercise intensity (% HRmax). These results indicated that 8 weeks of intensive cycling training increased HRV and cardiac vagal modulation during rest and absolute exercise work rates but had little effect during relative exercise work rates. Increased vagal modulation resulting from intensive exercise training may contribute to the mechanism of training-induced bradycardia. Key words: exercise training, autonomic nervous system, bradycardia, vagal modulation
Validation of Pulse Oximetry During Progressive Normobaric Hypoxia Utilizing a Portable Chamber
Authors: Kolb Jon C. , Farran Peter , Norris Stephen R. , Smith David , Mester Joachim
Published: June 2009

Validation of pulse oximetry in commercially available normobaric hypoxic chambers (NHC) has not been previously reported. The present study examined the validity of pulse oximetry (SpO2) against direct measurements of arterial oxygen saturation (SaO2) via co-oximetry (AVOXimeter 4000) in 13 young adults age 21.3 ± 0.6 years. Over a period of 2.5 hrs, the inspired fraction of oxygen inside a NHC (Hypoxico, Inc.) was progressively reduced from 20.9% to 11.5%. Measurements of SaO2 at baseline and at 15, 30, 60, 90, 120, and 150 min during the hypoxic exposures were compared with SpO2 estimates of oxygen saturation (Nellcor 295) using reflectance (RS-10, temporal) and transmission (D-25, finger) sensors. Regression analysis and methods for assessing agreement (bias, b; precision, p) of SaO2 with SpO2 were similar (R2 = 0.92, 0.89; b = 0.016, −0.47; p = 2.47, 3.03; RS-10 and D-25, respectively). When SaO2 < 85%, RS-10 had greater validity than D-25 (R2 = 0.73, 0.56; b = 1.38, 1.13; p = 2.72, 4.34; RS-10 and D-25, respectively). In light of these findings, caution should be exercised when monitoring individuals with pulse oximetry during desaturation episodes below 85%. When employing frequent NHC exposures, a priori validation of SpO2 utilized to assess blood oxygen status appears warranted. Key words: oxygen saturation, co-oximetry, altitude
Exercise and Estrogen or Estrogen Alternatives (Phytoestrogens, Bisphosphonates) for Preservation of Bone Mineral in Postmenopausal Women
Authors: Chilibeck Philip D.
Published: June 2009

Research in animal models indicates that without estrogen, the effectiveness of exercise for increasing bone mineral in females is reduced. With decreased estrogen levels, there is an increase in the threshold at which strains are detected by bone, in turn reducing the transmission of mechanical to biochemical signals for bone formation. Studies combining estrogen replacement and exercise training in postmenopausal women have yielded mixed results but indicate that the combination of interventions may be more effective than either intervention alone for increasing bone mass. Given the continued debate over the risks and benefits of estrogen replacement, other compounds such as bisphosphonates or phytoestrogens may be preferred in combination with exercise training for optimally increasing bone mass and preventing osteoporotic fracture. Studies on animals show that the combination of bisphosphonate or phytoestrogen supplementation with exercise training is effective, but trials in humans are lacking. Key words: osteoporosis, hormone replacement therapy, bisphosphonates, phytoestrogens, isoflavones
Anabolic Hormones in Aging Women: Effects of Supplementation vs. Physical Activity
Authors: Copeland Jennifer L.
Published: June 2009

Aging is associated with a decline in bone mass, muscle mass, strength, and physical function, and women are more likely to suffer from these physical changes than men. The model presented in this paper illustrates the age related changes in anabolic hormones and how this may partly explain the diminished physical function of older women. The model can also be used to identify potential sites of intervention that could delay the atrophy of the musculoskeletal system. Various pharmacological hormone therapies have been shown to be beneficial, but there may be health risks associated with their use. There is evidence that regular physical activity is related to higher levels of anabolic hormones in older persons, therefore exercise could be an alternative to drugs for slowing the age related changes in the endocrine system. However, some research suggests that the hormone response to exercise is blunted in older women. This lower hormonal response may not be a consequence of aging per se but instead may result from secondary characteristics of aging such as a decline in physical fitness and exercise intensity or changes in body composition. Further research is needed to determine whether exercise-induced increases in endogenous hormones have clinical significance in improving muscle or bone mass in aging women. Key words: hormone replacement therapy, exercise, sex steroids, growth hormone, IGF-I
Do Gender Differences in Running Performance Disappear With Distance?
Authors: Coast J. Richard , Blevins Jennifer S. , Wilson Brian A.
Published: June 2009

It has been suggested that gender differences in running should disappear as distances increase, particularly past the marathon. This suggestion is primarily based on differences in fuel utilization, muscle damage following exercise, relative improvements in performance over the past decades, and on the analysis of marathon vs. ultramarathon performances of men and women. We reasoned that the best comparison of the potential of a human is by the use of world best times, which should be reasonable indicators of the effect of distance on relative performance of women and men. We compared current world best running performances at distances from 100 m to 200 km. Records as of December 2002 were obtained. T-tests analyzed speed differences between genders, and regression analysis tested the percent differences between men and women across distance. Speeds were different, with the average difference being 12.4% faster for men. There was a significant slope to the speed difference across distances in that longer distances were associated with greater differences. These results may be confounded by the reduced number of women in longer distance events. Furthermore, the proposed metabolic advantage for women because of increased fat metabolism may be masked by regular feeding during endurance races. Key words: running records, male vs. female, human locomotion
Determinants and Upper-Limit Heritabilities of Skeletal Muscle Mass and Strength
Authors: Huygens Wim , Thomis Martine A. , Peeters Maarten W. , Vlietinck Robert F. , Beunen Gaston P.
Published: June 2009

The purpose of this study was to estimate the genetic and environmental contribution to variation in skeletal muscle mass and strength. In addition, important determinants were analyzed by stepwise multiple regression. In a large (N = 748) sibling pair sample of young brothers, ages 24.3 ± 4.5 years, upper-limit heritabilities (t2) were estimated as a proportion of genetic and shared environmental variability over total phenotypic variability by the variance components method in QTDT. Maximal isometric strength measures of knee, trunk, and elbow had higher t2 (82 to 96%) than concentric strength (63 to 87%) on Cybex isokinetic dynamometers. Indicators of muscle mass revealed very high transmissions (> 90%) whereas t2 was lower for adiposity (< 70%). Stepwise regression showed that fat-free mass was the primary determinant in knee and trunk strength (partial explained variance, R2 = 33-45%), but a local muscularity estimate (forearm circumference) was the main covariable for elbow strength (partial R2 = 18-39%). In this sample neither age nor physical activity, measured by the sport index of Baecke, appeared to be an important determinant of muscle mass or strength. These results show that maximal muscle strength and mass are highly transmissible and that muscle mass is the primary determinant of muscle strength. Key words: genetic variability, QTDT, variance components, covariates, transmissibility
Anaerobic Exercise and Oxidative Stress: A Review
Authors: Bloomer Richard J. , Goldfarb Allan H.
Published: June 2009

Oxidative stress and subsequent damage to cellular proteins, lipids, and nucleic acids, as well as changes to the glutathione system, are well documented in response to aerobic exercise. However, far less information is available on anaerobic exercise-induced oxidative modifications. Recent evidence indicates that high intensity anaerobic work does result in oxidative modification to the above-mentioned macromolecules in both skeletal muscle and blood. Also, it appears that chronic anaerobic exercise training can induce adaptations that act to attenuate the exercise-induced oxidative stress. These may be specific to increased antioxidant defenses and/or may act to reduce the generation of pro-oxidants during and after exercise. However, a wide variety of exercise protocols and assay procedures have been used to study oxidative stress pertaining to anaerobic work. Therefore, precise conclusions about the exact extent and location of oxidative macromolecule damage, in addition to the adaptations resulting from chronic anaerobic exercise training, are difficult to indicate. This manuscript provides a review of anaerobic exercise and oxidative stress, presenting both the acute effects of a single exercise bout and the potential for adaptations resulting from chronic anaerobic training. Key words: antioxidants, free radicals, training, lipid peroxidation, protein carbonyls
Mechanisms and Management of Fatigue in Health and Disease: Symposium Introduction
Authors: Green Howard J.
Published: June 2009

Exercise intolerance is a condition commonly experienced by both the healthy and those with disease. Yet we have only a limited understanding of the underlying mechanisms and, consequently, the management of this condition. In this Symposium, a major objective was to address the role of the muscle cell in weakness and fatigue. We have focused on addressing the advances made in characterizing the basis of muscle cell contractility with particular respect to the processes and proteins involved in excitation and contraction, and how these processes can be modified during repetitive activity. Three reviews are provided on this subject. Each addresses a specific link in the cascade of events from neural activation of the muscle to the generation of force. In the first review the processes involved in signal transduction in the sarcolemma and T-tubule, and which regulate membrane excitability, are examined. The second review analyzes the sarcoplasmic reticulum regulation of the intracellular messenger that controls the myofibrillar complex, namely free calcium. The final review in this series deals with the events regulating actin-myosin behaviour and the mechanical response. All reviews place special emphasis on how different sites can be modified by repetitive activity and, as a consequence, how they can represent a potential source of fatigue. Since it is important to understand the nature, manifestations, and measurement of weakness and fatigue, a comprehensive review on these topics is also provided. Key words: weakness, muscle, measurement, excitation, contraction
The Myofibrillar Complex and Fatigue: A Review
Authors: Vandenboom Rene
Published: June 2009

The basis for all biological movement is the conversion of chemical energy to mechanical energy by different classes of motor proteins. In skeletal muscle this motor protein is myosin II, a thick filament-based molecule that harnesses the free energy furnished by ATP hydrolysis to perform mechanical work against actin proteins of the thin filament. The cyclic attachment and detachment of myosin with actin that generates muscle force and shortening is Ca2+regulated. Intense muscle activity may lead to metabolically induced inhibitions to the function of these myofibrillar proteins when Ca2+regulation is normal, a phenomenon referred to as myofibrillar fatigue. Studies using single muscle fibers at room temperature or lower have shown that myosin motor function is inhibited by the accumulation of the ATP-hydrolysis products ADP, Pi, and H+as well as by excess generation of reactive oxygen species (ROS). These metabolically induced impairments to myosin motor function reduce muscle work and power output by impairing maximal Ca2+activated force, the Ca2+sensitivity of force, and/or unloaded shortening velocity. Based on uncertainties about their inhibitory effect on muscle function at more physiological temperatures, the influence of ATP-hydrolysis product and ROS accumulation on myofibrillar protein function of human skeletal muscle remains to be clarified. Key words: actin, myosin, muscle contraction
Adoption of Canada's Physical Activity Guide and Handbook for Older Adults: Impact on Functional Fitness and Energy Expenditure
Authors: Jiang Xuesong , Cooper Juliette , Porter Michelle M. , Ready A. Elizabeth
Published: June 2009

This study investigated whether a behaviour change program, based on Canada's Physical Activity Guide and Handbook to Healthy Active Living for Older Adults (Health Canada, 1999a), would elicit greater benefits than adoption of the guide and handbook alone. Fifteen older adults received the guide and accompanying handbook and completed the 8-week behaviour change program (mean age 73.2 ± 5.2 yrs), while 14 others received only the guide and handbook (mean age 76.8 ± 10.0 yrs). Functional fitness (lower body strength/endurance, flexibility, agility/dynamic balance) (Rikli and Jones, 1999), and estimated energy expenditure (DiPietro et al., 1993) were measured at baseline and after 8 weeks. Lower body strength/endurance and agility/dynamic balance differed between groups at baseline, p <  0.05. All three functional fitness tests improved in both groups over time, p <  0.05. Estimated energy expended in physical activity increased in both groups over time, p <  0.05; however, there was a significantly greater increase in the behaviour-change group (Group × Time interaction, p <  0.05). Participant response to using the guide and handbook was positive. These results indicate that introduction to Canada's Physical Activity Guide and Handbook to Healthy Active Living for Older Adults leads to benefits, whether or not accompanied by program supports. The group receiving the behaviour change program had a greater increase in energy expenditure, which suggests that such an intervention may ultimately lead to greater health benefits. Key words: behaviour change, chair stand test, community residing, lifestyle activity
Acute Interleukin-6 Administration Impairs Athletic Performance in Healthy, Trained Male Runners
Authors: Robson-Ansley Paula J. , Milander Liesl de , Collins Malcolm , Noakes Timothy D.
Published: June 2009

Fatigue is an inevitable consequence of physical activity; yet its biological cause remains uncertain. During exercise, a polypeptide messenger molecule interleukin-6 (IL-6) is actively produced. Previously, the administration of recombinant IL-6 (rhIL-6) induced a heightened sensation of fatigue in healthy humans at rest. In contrast, anti-IL-6 receptor antibodies reduced the symptoms of chronic fatigue. In the present study, athletic performance during an exercise challenge consisting of a 10-km running time trial was significantly impaired in trained male runners following the administration of a low dose of rhIL-6 compared to the placebo trial. Key words: prolonged exercise, fatigue, exercise challenge
Natural Killer Cells and Exercise Training in the Elderly: A Review
Authors: Dipenta Jennifer M. , Green-Johnson Julia , Murphy René J.L.
Published: June 2009

Consistent reports of the positive relationship between regular physical activity and immunosenescence have generated much excitement in the field of exercise immunology. It is generally accepted that natural killer (NK) cell activity per NK cell decreases with age; decreases in NKCA have been associated with infection and death in the aged. The effects of exercise and training on natural killer cells, components of the innate immune system, have been studied extensively in young people. However, the published research on the elderly population is limited. Generally it has been found that training increases or does not change natural killer cell activity or counts in the elderly. The clinical relevance of these results is yet to be fully explored. In addition, the limitations of these studies on immune function have been many, and studies are often difficult to compare due to differences in their methods and presentation of results. Key words: aging, immune function, NKCA
Acute Hormonal Responses to Heavy Resistance Exercise in Strength Athletes Versus Nonathletes
Authors: Ahtiainen Juha P. , Pakarinen Arto , Kraemer William J. , Hakkinen Keijo
Published: June 2009

The aim of the present study was to investigate acute hormonal and neuromuscular responses and recovery in strength athletes versus nonathletes during heavy resistance exercise performed with the forced and maximum repetitions training protocol. Eight male strength athletes (SA) with several years of continuous resistance training experience and 8 physically active but non-strength athletes (NA) volunteered as subjects. The experimental design comprised two loading sessions: maximum repetitions (MR) and forced repetitions (FR). MR included 12-RM squats for 4 sets with a 2-min recovery between sets. In FR the initial load was higher than in MR so that the subject could lift approximately 8 repetitions by himself and 4 additional repetitions with assistance. Before and after the loading protocols, blood samples were drawn to determine serum testosterone, free testosterone, cortisol and growth hormone concentrations, and blood lactate. Maximal voluntary isometric force and EMG activity of the leg extensors was measured before and after the loading as well as 24 and 48 hrs after the loading. The concentrations of the hormones measured increased significantly (p < .01-.001) after both loadings in both groups. The responses tended to be higher in FR than the MR loading and the increases of testosterone concentrations were significantly (p < .01) greater in both loadings in SA than in NA. Both loading protocols in both groups also led to neuromuscular fatigue observable with significant acute decreases in isometric strength by 32-52 % (p < .001) and in maximal iEMG (p < .05-01) associated with large increases in blood lactate. These data suggest that, at least in experienced strength athletes, the forced-repetition protocol is a viable alternative to the more traditional maximum-repetition protocol and may even be a superior approach. Key words: forced repetitions, recovery, EMG, isometric force
Cardiopulmonary Physiology and Responses of Ultramarathon Athletes to Prolonged Exercise
Authors: Blaber Andrew P. , Walsh Michael L. , Carter James B. , Seedhouse Erik L.O. , Walker Valerie E.
Published: June 2009

The purpose of this study was to determine the changes of pulmonary function and autonomic cardiovascular control after an ultramarathon and their relation to performance. Eight entrants to the Canadian National Championship 100-km running race participated in the study. Pulmonary function and 30-s maximum voluntary ventilation (MVV30s) tests were conducted one day before the race and within 5 minutes of race completion. Heart rate and blood pressure data were collected 30 min before and 5 min after the race as well as during a 10-min stand test one day prior to the race. During the race, beat-by-beat R-R interval data were collected over the first and last 20 km. The results showed that MW30s and MW30s tidal volumes were reduced postrace (p < 0.001). Prerace supine total harmonic variation (p < 0.01) and prerace MVV values (10 s to 30 s) (p < 0.05) were correlated with race finish time. The changes in pulmonary function and MW30s values from pre- and postrace were not significantly correlated to race performance. We conclude that maximal sustainable ventilatory power and dynamic autonomic cardiovascular control are important factors in determining overall performance in an ultramarathon. Key words: ultra-endurance, performance, pulmonary function, maximal ventilatory power, heart rate variability
Effects of an External Nasal Dilator on Athletic Performance of Male Adolescents
Authors: Macfarlane Duncan J. , Fong Stanley K. K.
Published: June 2009

This study examined the effect of an external nasal dilator strip (ENDS) on three field tests of maximal performance and monitored the rating of perceived breathing effort (RPBE). Thirty male Chinese students (age 15.2 ± 1.6 yrs) performed three maximal field tests: (a) short-term anaerobic power (SAnP: 40-m sprint); (b) long-term anaerobic power (LAnP: shuttle sprint); and (c) peak aerobic performance (AeP: multistage 20-m shuttle run) under three conditions: ENDS, placebo, and control. Students were randomly placed into 6 groups using a fully counterbalanced single-blind design. No significant differences were seen between conditions in the anaerobic performances measured by SAnP and LAnP. However, the ENDS produced a significant improvement in peak aerobic performance (p = 0.037) compared to the control condition of 3.2% (95 %CI = 6.2-0.2; Cohen effect size = 0.2), and also compared to the placebo condition (p = 0.018) of 2.9% (95% CI = 5.1-0.2; Cohen effect size = 0.2). The ENDS condition also significantly reduced RPBE during the AeP and LAnP tests by an average of 5.5% and 3.8%, respectively. Wearing an external nasal dilator can significantly reduce breathing effort and improve peak aerobic performance during field tests involving maximal running. Key words: performance enhancement, nasal strip, oronasal ventilation, perceived breathing effort
Physical Activity and Atherosclerosis: Which Animal Model?
Authors: Turk James R. , Laughlin M. Harold
Published: June 2009

Atherosclerosis is a progressive disease that is the most important single contributor to human cardiovascular morbidity and mortality. Epidemiologic studies show that physical activity, or routine exercise, reduces the risk of developing cardiovascular disease. The mechanisms through which exercise may function in primary or secondary prevention of atherosclerosis remain largely to be established. Most studies in humans are performed after the onset of clinical signs when disease is well advanced and the prescription of exercise is based on empirical evidence of benefit in secondary prevention. Animal models permit the study of the initiation and progression of preclinical stages of atherosclerosis. In order to provide information relevant to treatment and prevention, these models should mimic human disease and interactions of physical activity with disease processes as closely as possible. The purpose of this review is to compare animal models of atherosclerosis and to summarize the available data in those models in regard to the effects of exercise. Key words: hypercholesterolemia, exercise, pathology, porcine
Hormonal and Metabolic Adaptation in Professional Cyclists During Training
Authors: Chennaoui Mounir , Gomez-Merino Danielle , Drogou Catherine , Bourrilhon Cyprien , Sautivet Samuel , Guezennec Charles Yannick
Published: June 2009

The aim of this study was to examine hormonal and metabolic changes in a group of 18 professional male cyclists ([Formula: see text]69.9 [95% CI 64.9 to 74.9] m L kg−1ùmin−1) during two successive periods of adapted intensive training. The second training period included 4 days of cycling competition. Intensity was increased while volume was decreased in the second training. Anthropometric data were collected before and at the end of the two training periods. Venous blood samples were taken in a basal state before the two training sessions and after each training session. Serum concentrations of cortisol (C), testosterone (T), dehydroepiandrosterone sulfate (DHEAs), and catecholamines were determined as well as branched-chain amino acids (valine, leucine, isoleucine) (BCAA) and free fatty acids (FFAs). At the end of the two training periods, the subjects lost fat mass whereas mean body mass was unchanged. The T/C ratio was reduced transiently after the first training session (45.90%), while DHEAs/C remained unchanged. T/C and DHEAs/C were significantly increased after the second training session compared to the first (48.40 and 97.18%, respectively). Catecholamines and FFAs were unchanged. The significant increase in BCAA levels after the second training session was of note as it might constitute a "store shape" of amino acids in anticipation of future intense training loads. Based on the responses of testosterone, DHEAs, and cortisol, and on the training-induced increase in BCAA, there appeared to be hormonal and metabolic adaptation despite the inherent psychological stress of competition. Key words: cycling training, cortisol, testosterone, DHEAs, amino acids
Heart Rate Running Speed Relationships During Exhaustive Bouts in the Laboratory
Authors: Boudet Gil , Albuisson Elianne , Bedu Mario , Chamoux Alain
Published: June 2009

The present study was designed to investigate the heart rate-running speed (HR-RS) relationship while exercising continuously, at high intensities, on a treadmill. The purpose was to precisely measure the magnitude of drop in RS necessary to maintain HR during intense exhaustive exercises, and to determine whether the magnitude of drop in RS is directly depedent on exercise intensity. Sixteen male endurance athletes performed five treadmill tests: an incremental test for maximal O2 uptake and maximum aerobic velocity (VMA), and four exhaustive tests: at 82, 86, 89, and 92% VMA. After an adaptation period of 3 min, the objective was to stabilise HR by adjusting the treadmill speed continuously by ± 0.5 km•h−1 every 30 sec. Attained intensities were: 82% (±6), 84% (±6), 89% (±3), and 90% (±6) VMA, respectively [L1, L2] vs. [L3, L4], p <  0.05. Time to exhaustion accross the increasing intensities, respectively, were: 36.58 (±4.45), 24.63 (±3.25), 15.80 (±2.00), and 9.87 (±1.15) min, p <  0.05, with the exception of L3 vs. L4. The RS/HR ratio vs. speed showed three phases: an increasing adaptive (AB) phase 0-165 sec with an averaging maximal level of 1.67 m•beat−1 at 165 sec, a transitional period 170-245 sec, and a decreasing (BC) phase 250-1800 sec with a lower level of 1.29 m•beat−1 at 1800 sec. In our experimental conditions, for high intensities 82 to 90% VMA, cardiac drift which disturbed the RS-HR relationship with duration was evaluated: −0.143 km•h−1 per minute for HR stabilisation. This cardiac drift is a linear function of time. Results suggest that HR and RS are not interchangeable variables for this kind of exercises, and it seems more reliable to gauge exercise intensity using RS than HR. Key words: cardiac drift, exhaustive tests, treadmill
Resting Mechanomyography After Aerobic Exercise
Authors: McKay William P.S. , Chilibeck Philip D. , Chad Karen E. , Daku Brian L.F.
Published: June 2009

A number of mechanisms have been proposed for the elevation in oxygen consumption following exercise. Biochemical processes that return muscle to its preexercise state do not account for all the oxygen consumed after exercise. It is possible that mechanical activity in resting muscle, which produces low frequency vibrations (i.e., muscle sounds: mechano-myographic [MMG] activity), could contribute to the excess postexercise oxygen consumption. Therefore the purpose of this study was to determine whether the resting MMG amplitude changes after exercise, and whether the change is related to the elevation in oxygen consumption [Formula: see text] Ten young male subjects (22.9 yrs) performed 30 minutes of exercise on a cycle ergometer at an intensity corresponding to 70%peak [Formula: see text] Oxygen consumption was measured by indirect calorimetry, and MMG by an accelerometer placed over the mid-quadriceps before exercise and for 5.5 hours after exercise. MMG activity, expressed as mean absolute acceleration, was significantly elevated for the 5.5 hours of measurement after exercise (p <  0.05). MMG and [Formula: see text] decayed exponentially after exercise with time constants of 7.2 minutes and 7.4 minutes, respectively. We conclude that muscle is mechanically active following exercise and that this may contribute to an elevated [Formula: see text] Key words: excess postexercise oxygen consumption, muscle sounds, acoustic myography
Exercise, Postprandial Triacylglyceridemia, and Cardiovascular Disease Risk
Authors: Graham Terry E.
Published: June 2009

An elevation of plasma triacylglycerides (TAG) is a well recognized cardiovascular risk factor. Less appreciated is that high and prolonged elevations in TAG in the postprandial (PP) phase is also a risk factor. Given that we spend approximately 18 hrs a day in the PP state, this is particularly critical. The elevation is due to both cylomicron and very low density lipoprotein TAG. It is thought that enhancing the concentrations of these lipoproprotein fractions increases the production of smaller, more dense low density lipoprotein and that this leads to increased cardiovascular disease risk. The PP TAG response is greater in men, in obese individuals, and in type 2 diabetics. It has been reported repeatedly that exercise the day before ingestion of a high fat meal is associated with a marked dampening of the PP TAG rise. The mechanisms for this are not clear and do not appear to be due to changes in the exercised muscle itself. There is some speculation that the production of plasma TAG may be decreased. The exercise benefits are lost within 3 days. The minimum exercise required has not been determined, but even 30 min of intermittent aerobic exercise or mild resistance exercise has a positive effect. This demonstrates a clear benefit from an active lifestyle and one that does not require intense exercise or months of training. Key words: atherosclerosis, type 2 diabetes, dietary fats, carbohydrates, VLDL, LDL, triglycerides, sex differences
Aerobic Exercise, Lipoproteins, and Cardiovascular Disease: Benefits and Possible Risks
Authors: Herzberg Gene R.
Published: June 2009

Aerobic exercise has been shown to reduce the risk of cardiovascular disease (CVD). This reduction is proportional to the intensity of the exercise. The reduction in CVD risk is at least partially mediated by changes in circulating lipoproteins resulting from adaptive changes in enzymes involved in their metabolism. Specifically, aerobic exercise is associated with reductions in low density lipoprotein (LDL), total cholesterol and triacylglycerol (TAG), and increases in high density lipoprotein (HDL). Exposure to oxygen can oxidatively damage LDL. Oxidized LDL is a risk factor for atherosclerosis. Although aerobic exercise can cause oxidative damage, there are adaptive changes resulting from chronic exercise that result in lower rather than higher levels of oxidized LDL. Key words: oxidized LDL, triacylglycerol, atherosclerosis, HDL
Metabolic Syndrome, a Cardiovascular Disease Risk Factor: Role of Adipocytokines and Impact of Diet and Physical Activity
Authors: Robinson Lindsay E. , Graham Terry E.
Published: June 2009

The metabolic syndrome comprises an array of cardiovascular disease (CVD) risk factors such as abdominal obesity, dyslipidemia, hypertension, and glucose intolerance. Insulin resistance and/or increased abdominal (visceral) obesity have been suggested as potential etiological factors. More recently, increasing evidence has associated insulin resistance and subclinical inflammation involving cytokines derived from adipose tissue, or adipocytokines. Despite the fact that precise mechanisms have yet to be established, there is a significant role for both diet and physical activity to improve the many factors associated with the metabolic syndrome, including modulation of various adipocytokines. Although both diet and physical activity have been studied for their ability to modify cytokines in more traditional inflammatory conditions, such as rheumatoid arthritis, they have been less studied in relation to inflammation as an underlying cause of the metabolic syndrome and/or CVD. A more thorough understanding of the clustering of metabolic abnormalities and their underlying etiology will help to define diet and physical activity guidelines for preventing and treating the metabolic syndrome, an important aspect of CVD prevention. This paper will address potential underlying causes of the metabolic syndrome, with a focus on the putative mechanistic role of adipocytokines, and will discuss the impact of diet and physical activity on the metabolic syndrome. Key words: insulin resistance syndrome, obesity, adipose tissue, skeletal muscle, cytokines, TNF-α, IL-6, PAI-1, inflammation, nutrition, exercise