bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic Responses of O2 Uptake at the Onset and End of Exercise in Trained Subjects
Authors: Cleuziou Christophe , Perrey Stéphane , Borrani Fabio , Lecoq Anne Marie , Candau Robin , Courteix Daniel , Obert Philippe
Published: June 2009

Inconsistencies about dynamic asymmetry between the on- and off-transient responses in [Formula: see text] are found in the literature. Therefore the purpose of this study was to examine [Formula: see text]on- and off-transients during moderate- and heavy-intensity cycling exercise in trained subjects. Ten men underwent an initial incremental test for the estimation of ventilatory threshold (VT) and, on different days, two bouts of square-wave exercise at moderate (< VT) and heavy (> VT) intensities. [Formula: see text] kinetics in exercise and recovery were better described by a single exponential model (< VT), or by a double exponential with two time delays (> VT). For moderate exercise, we found a symmetry of [Formula: see text] kinetics between the on- and off-transients (i.e., fundamental component), consistent with a system manifesting linear control dynamics. For heavy exercise, a slow component superimposed on the fundamental phase was expressed in both the exercise and recovery, with similar parameter estimates. But the on-transient values of the time constant were appreciably faster than the associated off-transient, and independent of the work rate imposed (< VT and > VT). Our results do not support a dynamically linear system model of [Formula: see text] during cycling exercise in the heavy-intensity domain. Key words: oxygen uptake kinetics, on- and off-transients, slow component
Ambulatory Activity and Simple Cardiorespiratory Parameters at Rest and Submaximal Exercise
Authors: Tudor-Locke Catrine , Ainsworth Barbara E. , Whitt Melicia C. , Thompson Raymond W. , Addy Cheryl L. , Jones Deborah A.
Published: June 2009

The purpose of this study was to explore the relationship between objectively determined ambulatory activity and simple cardiorespiratory parameters (heart rate and blood pressure at rest and during submaximal exercise) in individuals who were stratified for self-reported participation (yes/any vs. no/none) in vigorous physical activity (PA). Ninety-eight subjects (African Americans: 7 M, 16 F; Caucasians: 33 M, 42 F; mean age 46.4 ± 15.4 yrs; mean BMI 26.7 ± 4.8) wore a pedometer for 21 consecutive days and completed a 10-min submaximal treadmill graded exercise test with HR (beats/min) and BP (mmHg) measured while walking at 4.8 km/hr and a 10% grade. Subjects averaged 7,618 ± 3,045 steps/day. There were no differences in steps/day by self-reported vigorous PA strata. There was an inverse relationship (r = −0.35, p = 0.03) between steps/day and resting HR in subjects who reported no vigorous PA. There was an inverse relationship (r = −0.22, p = 0.04) between steps/day and submaximal HR in all subjects. When stratified for self-reported vigorous PA, the inverse relationship between steps/day and submaximal HR was stronger for those reporting no vigorous PA (r = −0.39, p = 0.01) vs. those reporting any vigorous PA (r = 0.28, p = 0.05). There was no relationship between steps/day and BP at rest or during exercise in this normotensive sample. Key words: walking, blood pressure, heart rate
Metabolic Control of Muscle Blood Flow During Exercise in Humans
Authors: Boushel Robert
Published: June 2009

During muscle contraction, several mechanisms regulate blood flow to ensure a close coupling between muscle oxygen delivery and metabolic demand. No single factor has been identified to constitute the primary metabolic regulator, yet there are signal transduction pathways between skeletal muscle and the vasculature that induce vasodilation. A link between muscle metabolic events and microvascular control of blood flow is illustrated by local dilation of terminal arterioles during contraction of muscle fibers and conduction of vasodilation upstream. Endothelial-derived vasodilator mechanisms are known to exert control of muscle vasodilation. Adenosine, nitric oxide (NO), prostacyclin (PGI2), and endothelial-derived hyperpolarization factor (EDHF) are possible mediators of muscle vasodilation during exercise. In humans, adenosine has been shown to contribute to functional hyperemia as blood flow is reduced under nonselective adenosine-receptor blockade. No clear role has been demonstrated for either NO or PGI2, based on studies employing selective inhibition of these substances individually, suggesting a redundancy of vasodilator mechanisms. This is supported by recent work demonstrating that combined blockade of NOS and PGI2, and NOS and cytochrome P450, both attenuate exercise-induced hyperemia in humans. Combined vasodilator blockade studies offer the potential to uncover important interactions and compensatory vasodilator responses. The signaling pathways that link metabolic events evoked by muscle contraction to vasodilatory signals in the local vascular bed remains an important area of study. Key words: metabolic vasodilation, endothelium
Regulation of Blood Flow at the Onset of Exercise by Feed Forward and Feedback Mechanisms
Authors: Hughson Richard L.
Published: June 2009

Blood flow adapts quickly after the onset of exercise to meet the metabolic demands of skeletal muscle. This review approaches the issue of how rapidly blood flow adapts and what the mechanisms for adaptation are primarily from a control theory perspective. Several recent papers have suggested that O2 transport proceeds at a rate that anticipates the metabolic demand over a very wide range of work rates. When considered from a control theory perspective, this implies involvement of feed forward control. Although there is one very important feed forward mechanism in the muscle pump that is activated with the onset of exercise, other evidence suggests that adjustment of blood flow to match the metabolic demand relies on feedback control from local dilator factors released in proportion to the metabolic demand. These distinct mechanisms with different onset times mean that blood flow adapts to the exercise demand with at least two distinct phases. The time course of the adaptation varies greatly between work rates, showing that blood flow control cannot be described by a linear control system and that the mechanisms responsible for vasodilation are dependent on work rate. Key words: oxygen uptake, kinetics, vasodilation, muscle metabolism
Effect of Menstrual Phase on the Acetate Correction Factor Used in Metabolic Tracer Studies
Authors: Oosthuyse Tanja , Bosch Andrew N. , Jackson Susan
Published: June 2009

The acetate correction factor is used to account for retention of carbon label in exchange reactions of the tricarboxylic acid cycle in studies estimating free fatty acid oxidation with carbon-labeled tracers. Previous evidence indicates that substrate utilisation and metabolic rate vary across the menstrual cycle, which may alter the correction factor. We therefore derived the acetate correction factor for each of three menstrual phases (early follicular [EF], late follicular [LF], and midluteal [ML] phase) from the fractional recovery of 13CO2 from a constant infusion of sodium-[1-13C]acetate during 90 min of submaximal exercise (60%[Formula: see text]) in sedentary eumenorrhoeic women. There was no difference in the correction factor between the EF and LF or the LF and ML phases, but the correction factor derived in the ML phase was significantly lower than in the EF phase (p < 0.05). Neither energy expenditure nor whole body substrate utilisation during exercise varied significantly between menstrual phases and therefore cannot explain the observed difference in the correction factor. The lower correction factor in the ML phase, compared to the EF phase, would result in only a small increase of ∼6% in the calculated plasma free fatty acid oxidation rate. Key words: carbon isotopes, women, ovarian hormones, exercise, substrate oxidation
Etudes comparées des rythmes circadiens et reflet actimétrique du sommeil de sportifs et de sédentaires en poste régulier de nuit
Authors: Mauvieux Benoît , Gouthière Laurent , Sesboüe Bruno , Davenne Damien
Published: June 2009

The aim of this study was to show the resistance and persistence of the circadian rhythm of temperature (T°) and the sleep quality of athletic subjects and sedentary subjects engaged in night work, and attempt to explain the mechanisms that influence these differences. The effects of night work on biological rhythms have been studied extensively in the past few years. The contradictory situations for the night workers irrefutably affect their biological systems. Individuals with high amplitudes in their circadian rhythms have been found to be more tolerant to shift work and this results in a greater stability of circadian rhythms. This seems beneficial in coping with frequent rhythm disturbances. The physical training program seems to improve several mechanisms of the human biological system: amplitudes of circadian rhythms were increased and the circadian rhythm period was more resistant to an environment extreme (night work, shift work, sleep deprivation, or jet lag). To test this hypothesis, athletes and sedentary subjects who were engaged in regular night work were selected in the PSA Peugeot Citroën Automobiles Group in French Normandy country. The circadian rhythm of the T° for both groups was studied with a specific methodology and with extensive spectral analysis, especially the spectral elliptic inverse method. Study models of the rhythm of the T° were determined and the characteristic parameters were exposed. A complementary actigraphic study showed the physical training program's effects on the sleep quality. The results revealed a large stability in the rhythm of circadian variation of T° for the athletes: the amplitude was still large but for the sedentary subjects the amplitude of the T° decreased and it was difficult to adjust a period on the rhythm of T°. The stability and persistent quality of the athletes' circadian rhythm was confirmed. We observed that the actigraphic sleep was greater for athletes than for sedentary subjects, and the acrophase time for the athletes was later than for the sedentary subjects during the night shift. Key words: circadian rhythm of temperature, actimetry, sleep quality, exercise, night work, methodology of rhythms analysis
Effects of Helium and 40% O2 on Graded Exercise With Self-Contained Breathing Apparatus
Authors: Eves Neil D. , Petersen Stewart R. , Jones Richard L.
Published: June 2009

Maximal exercise performance is decreased when breathing from a self-contained breathing apparatus (SCBA), owing to a ventilatory limitation imposed by the increased expiratory resistance. To test the hypothesis that decreasing the density of the breathing gas would improve maximal exercise performance, we studied 15 men during four graded exercise tests with the SCBA. Participants breathed a different gas mixture during each test: normoxia (NOX; 21% O2, 79% N2), hyperoxia (HOX; 40% O2, 60% N2), normoxic helium (HE-OX; 21% O2, 79% He), and hyperoxic helium (HE-HOX; 40% O2, 60% He). Compared to NOX, power output at the ventilatory threshold and at maximal exercise significantly increased with both hyperoxic mixtures. Minute ventilation was increased at peak exercise with both helium mixtures, and maximal aerobic power ([Formula: see text]) was significantly increased by 12.9 ± 5.6%, 10.2 ± 6.3%, and 21.8 ± 5.6% with HOX, HE-OX, and HE-HOX, respectively. At peak exercise, the expired breathing resistance imposed by the SCBA was significantly decreased with both helium mixtures, and perceived respiratory distress was lower with HE-HOX. The results show that HE-OX improved maximal exercise performance by minimizing the ventilation limitation. The performance-enhancing effect of HOX may be explained by increased arterial oxygen content. Moreover, HE-HOX appeared to combine the effects of helium and hyperoxia on [Formula: see text]Key words:[Formula: see text] breathing resistance, ventilatory limitation, heliox, firefighting
Dynamic Responses of Oxygen Uptake at the Onset and End of Moderate and Heavy Exercise in Trained Subjects
Authors: Cleuziou Christophe , Perrey Stéphane , Borrani Fabio , Lecoq Anne Marie , Candau Robin , Courteix Daniel , Obert Philippe
Published: June 2009

Inconsistencies about dynamic asymmetry between the on- and off-transient responses in [Formula: see text] are found in the literature. Therefore the purpose of this study was to examine [Formula: see text]on-and off-transients during moderate- and heavy-intensity cycling exercise in trained subjects. Ten men underwent an initial incremental test for the estimation of ventilatory threshold (VT) and, on different days, two bouts of square-wave exercise at moderate (< VT) and heavy (> VT) intensities. [Formula: see text] kinetics in exercise and recovery were better described by a single exponential model (< VT), or by a double exponential with two time delays (> VT). For moderate exercise, we found a symmetry of [Formula: see text] kinetics between the on- and off-transients (i.e., fundamental component), consistent with a system manifesting linear control dynamics. For heavy exercise, a slow component superimposed on the fundamental phase was expressed in both the exercise and recovery, with similar parameter estimates. But the on-transient values of the time constant were appreciably faster than the associated off-transient, and independent of the work rate imposed (< VT and > VT). Our results do not support a dynamically linear system model of [Formula: see text] during cycling exercise in the heavy-intensity domain. Key words: oxygen uptake kinetics, on- and off-transients, slow component
Exercise Endocrinology in Women: Issues Across the Lifespan Symposium Introduction
Authors: Tremblay Mark S.
Published: June 2009

Recent concerns over the risks of hormone replacement therapy in postmenopausal women have increased interest in assessing alternative therapies to preserve the health and well-being of women as they age. Because of the dramatic changes observed in the endocrine system as women age, particularly with anabolic hormones, there is interest in the potential for exercise to promote a hormonal milieu that preserves or enhances physiological function, especially muscle and bone mass, and healthy aging. To examine this potential, the papers from this symposium assessed different but related areas of exercise endocrinology in women. The symposium addressed important work on energy balance and reproductive function, exercise and estrogen interactions on health in postmenopausal women, and how age affects hormonal responses to exercise in women. Methodological inconsistencies make it difficult to draw definitive conclusions, which highlights the need for additional, carefully controlled work in this area. Key words: hormones, physical activity, female, methodological issues
Energy Balance and Reproductive Function in Active Women
Authors: Harber Vicki J.
Published: June 2009

Athletes engaged in rigorous training programs expend large amounts of energy and require appropriate energetic compensation to maintain or improve performance. If these exercise regimens are not fueled sufficiently, a negative energy balance will likely emerge and lead to a broad spectrum of menstrual cycle disturbances and less than optimal performance. This review examines the theory and evidence surrounding energy availability and reproductive function. Implications for performance and treatment strategies are also addressed. Key words: energy intake, energy expenditure, energy availability, menstrual disorders, LH pulsatility, amenorrhea
Perfused Skeletal Muscle-An Experimental Preparation for Many Questions¡
Authors: Barclay Jack K. , Stainsby Wendell N.
Published: June 2009

Perfused mammalian skeletal muscle preparations either in vitro or in situ are one of the options to be considered when planning a physiological research program or project. Such preparations have been and continue to be used to investigate research questions as diverse as skeletal muscle function and metabolism, peripheral vascular function, and an approximation of exercise. When selecting a perfused muscle preparation, both anatomical and physiological organization must be evaluated in the context of the planned experiment. In any experiment, a number of physiologically significant variables can be manipulated, such as the level of flow and the arterial or inflow concentration of a gas or substance to control substrate supply and metabolite removal as well as the stimulation parameters to alter metabolic rate. The choice of blood or an artificial perfusate is of paramount importance because, when compared to blood-perfused preparations, those receiving artificial perfusates show depressed vascular autoregulation among other changes, indicating a decrease in physiological quality. Overall, perfused skeletal muscle preparations can be used to examine many and varied research questions with close to in-vivo quality and a high degree of accuracy and control if blood-perfused. Keywords: choice of preparation, experimentally controllable variables, evaluation of preparations, pressure-flow autoregulation, flow-independent oxygen uptake
Effect of a 15% Increase in Preferred Pedal Rate on Time to Exhaustion During Heavy Exercise
Authors: Nesi Xavier , Bosquet Laurent , Berthoin Serge , Dekerle Jeanne , Pelayo Patrick
Published: June 2009

The aim of this study was to evaluate the effect of a 15% increase in preferred pedal rate (PPR) on both time to exhaustion and pulmonary O2 uptake [Formula: see text] response during heavy exercise. Seven competitive cyclists underwent two constant-power tests (CPT) at a power output that theoretically requires 50% of the difference in [Formula: see text] between the second ventilatory threshold and [Formula: see text]max (PΔ50). Each cyclist cycled a CPT at PPR (CPTPPR) and a CPT at +15% of PPR (CPT+15%) in a randomized order. The average PPR value was 94 ± 4 rpm, and time to exhaustion was significantly longer in CPTPPR compared with CPT+15% (465 ± 139 vs. 303 ± 42 s, respectively; p = 0.01). A significant decrease in [Formula: see text] values in the first minutes of exercise and a significant increase in [Formula: see text] slow component was reported in CPT+15% compared with CPTPPR. These data indicate that the increase of 15% PPR was associated with a decrease in exercise tolerance and a specific [Formula: see text] response, presumably due to an increase of negative muscular work, internal work, and an altering of motor unit recruitment patterns. Key words: aerobic demand, cadence, cyclists, exercise tolerance, pedaling frequency
Effects of Jump Training on Procollagen α1(I) mRNA Expression and Its Relationship
Authors: Concentration With Collagen
Published: June 2009

The aim of this study was to examine the effects of a prolonged high-intensity exercise, jumping, on procollagen α1(I) mRNA level and collagen concentration in different muscles of trained (T) and control (C) rabbits. Procollagen α1 (I) mRNA expression was much higher (2.8 to 23.5 times) in semimembranosus proprius (SMP), a slow-twitch oxidative muscle, than in extensor digitorum longus (EDL), rectus femoris (RF), and psoas major (Psoas) muscles, both fast-twitch mixed and glycolytic, whatever group was considered (p <  0.001). Procollagen α1(I) mRNA level also decreased significantly between 50 and 140 days in all muscles (0.001 <  p <  0.01). However, mRNA levels were 16 to 97% greater at 140 days in all muscles of T animals compared to C ones (0.01 <  p < 0.05). Collagen concentrations of EDL and RF muscles were also higher (14 to 19%) in T than in C rabbits at 90 and 140 days (0.001 <  p <  0.05). In the whole sample, collagen concentration was negatively associated with the procollagen α1(I) mRNA level in EDL and RF muscles (−0.49 <  r <  −0.44, p <  0.05), while being positively related to mRNA expression in SMP and Psoas muscles (0.65 <  r <  0.85, p <  0.01). It is concluded that jump training clearly restricts the decrease of procollagen (I) mRNA level and probably affects collagen synthesis level. In trained rabbit muscles, the maintenance of a better synthesis level could partly explain the higher collagen concentrations found in EDL and RF at 140 days. Nevertheless, the collagen degradation process seems to play the main role in the increase of total collagen concentration with age in EDL and RF muscles. Key words: collagen synthesis, high intensity exercise, muscle type, age
L'activité physique habituelle au cours du développement
Authors: Gavarry Olivier , Falgairette Guy
Published: June 2009

The three objectives of the present review of the literature were to: characterize the evolution of habitual physical activity (HPA) during growth; evaluate the tracking of HPA from childhood to adulthood; and analyse the level of HPA in children and adolescents according to public health recommendations. Data indicates that HPA decreases from childhood to adulthood about 7% per year, with a great reduction during puberty and adolescence concurrent to changes in the type of physical activity. It appears that HPA is not quite steady (0.09 <  r <  0.66) during growth, which means that behavioural changes occur. Being very active during childhood or adolescence does not necessarily translate into a high level of HPA in adulthood. The mean values of HPA of children and adolescents vary from 15 to 90 min•day−1between studies, and for most of them HPA has been higher or close to public health recommendations. However, these results mask a great number of children and adolescents who are inactive or becoming inactive (40 to 45% of the population). Key words: children, adolescents, heart rate monitoring, questionnaire, health
Force Maintenance With Submaximal Fatiguing Contractions
Authors: Behm David G.
Published: June 2009

Whereas many definitions of fatigue include externally measurable decrements in force or performance, fatigue can be present with no change in the external output of the muscle. The maintenance of submaximal forces can be considered a compromise between neuromuscular force enhancement and competing inhibitory influences. An example of a muscle facilitatory process includes postactivation potentiation that results in an increased sensitivity to Ca++. The neuromuscular system copes with metabolic disruption and subsequent loss of force by recruiting additional motor units and increasing the firing frequency. If the contraction persists, firing frequency may decrease so as to optimize the stimulus rate with the prolonged duration of the muscle fibre action potential (muscle wisdom). The insertion of additional neural impulses into the train of stimuli can result in force potentiation (catch-like properties). Furthermore, there is evidence of neural potentiation and a dissociation of muscle activity with submaximal fatigue. Conversely, inhibition may be derived supraspinally or at the spinal level. While there may be some evidence of intrinsic motoneuronal fatigue, inhibitory afferent influences from chemical, tensile, pressure, and other factors play an important role in the competing influences on force output. Key words: postactivation potentiation, recruitment, rate coding, inhibition, catch-like properties
Membrane Excitability, Weakness, and Fatigue
Authors: Green Howard J.
Published: June 2009

A failure in membrane excitability, defined as an inability of the sarcolemma and T-tubule to translate the neural discharge command into repetitive action potentials, represents an inviting cause of mechanical disfunction in both health and disease. A failure at this level would precipitate a disturbance in signal transmission between the T-tubule and the calcium release channels of the sarcoplasmic reticulum, resulting in reduced release of Ca2+, lower cytosolic free Ca2+ levels, and depressed myofibrillar activation and force generation. The ability of the sarcolemma and T-tubules to conduct repetitive action potentials is intimately dependent on active transport of Na+ and K+ following an action potential. The active transport of these cations is mediated by the Na+-K+-ATPase, an integral membrane protein that uses the energy from the hydrolysis of 1 ATP to transport 3Na+ out of the cell and 2K+ into the cell. A failure to recruit sufficient Na+-K+-ATPase activity during contractile activity could result in a rundown of the transmembrane gradients for Na+ and K+, leading to a loss of membrane excitability. The Na+-K+-ATPase activity depends on the amount and isoform composition of the protein, substrate availability, and acute regulatory factors. Each of these factors is examined as a potential cause of altered activation of the Na+-K+-ATPase activity and loss of membrane excitability in fatigue. Regular exercise represents a potent stimulus for upregulating Na+-K+-ATPase levels and for increasing the ability for cation transport across the sarcolemma and T-tubule membrane. As such, training may be a valuable tool in the management of fatigue in health and disease. Key words: muscle, Na+-K+-ATPase, isoforms, action potentials
Sedentary Death Syndrome
Authors: Lees Simon J. , Booth Frank W.
Published: June 2009

Sedentary death syndrome (SeDS) is a major public health burden due to its causing multiple chronic diseases and millions of premature deaths each year. Despite the impact of physical inactivity, very little is known about the actual causes of physical inactivity-induced chronic diseases. It is important to study the mechanisms underlying molecular changes related to physical inactivity in order to better understand the scientific basis of individualized exercise prescription and the rapies for chronic diseases, and to support improved public health efforts by providing molecular proof that physical inactivity is an actual cause of chronic diseases. Physical activity has a genetic basis. A subpopulation of genes, which have functioned to support physical activity for survival through most of humankind's existence, require daily exercise to maintain long-term health and vitality. Type 2 diabetes (T2D) is an example of a SeDS condition, as it is almost entirely preventable with physical activity. To determine the true role of physical inactivity in the development and progression of T2D, information is presented which indicates that comparisons should be made to physically active controls, rather than sedentary controls, as this population is the healthiest. Use of sedentary subjects as the control group has led to potentially misleading interpretations. If physically active individuals were designated as the control group, a different interpretation would have been drawn. It is thought that there is no difference in GLUT4 concentration between T2D and sedentary groups. However, GLUT4 expression is higher in active controls than in sedentary and T2D groups. Therefore, to obtain causal mechanisms for SeDS in order to allow for scientifically based prevention and therapy strategies, physically active subjects must serve as the control group. Key words: physical inactivity, chronic diseases, diabetes, glucose
Near Infrared Spectroscopy: From the "Black Box to the Ice Arena." Symposium Introduction
Authors: Neary J. Patrick , Bhambhani Yagesh N.
Published: June 2009

not available
Principles, Techniques, and Limitations of Near Infrared Spectroscopy
Authors: Ferrari Marco , Mottola Leonardo , Quaresima Valentina
Published: June 2009

In the last decade the study of the human brain and muscle energetics underwent a radical change, thanks to the progressive introduction of noninvasive techniques, including near-infrared (NIR) spectroscopy (NIRS). This review summarizes the most recent literature about the principles, techniques, advantages, limitations, and applications of NIRS in exercise physiology and neuroscience. The main NIRS instrumentations and measurable parameters will be reported. NIR light (700-1000 nm) penetrates superficial layers (skin, subcutaneous fat, skull, etc.) and is either absorbed by chromophores (oxy- and deoxyhemoglobin and myoglobin) or scattered within the tissue. NIRS is a noninvasive and relatively low-cost optical technique that is becoming a widely used instrument for measuring tissue O2 saturation, changes in hemoglobin volume and, indirectly, brain/muscle blood flow and muscle O2 consumption. Tissue O2 saturation represents a dynamic balance between O2 supply and O2 consumption in the small vessels such as the capillary, arteriolar, and venular bed. The possibility of measuring the cortical activation in response to different stimuli, and the changes in the cortical cytochrome oxidase redox state upon O2 delivery changes, will also be mentioned. Key words: tissue oximetry, oxidative metabolism, optical imaging, blood flow, oxygen consumption, exercise physiology
Fatty Acids and Exercise Affect Glucose Transport But Not Tumour Growth in F-344 Rats
Authors: Foley Jennifer M. , Stark Ken D. , Zajchowski Sheri , Meckling Kelly A.
Published: June 2009

This study examined the effect of diet and exercise on tumour growth, and the effect of dietary fatty acids on glucose uptake. Male Fischer 344 rats were divided into 4 dietary groups and fed for 2 weeks. The diets were 5% (wt/wt) safflower oil, 10% safflower oil, 5% docosahexaenoic acid(DHA)-rich, and 10% DHA-rich. On Day 14 the animals were injected with rat fibrosarcoma tumour cells. After 3 days of tumour growth the animals in each diet group were divided into exercise and nonexercise groups. Exercise was achieved by voluntary wheel running. Dietary intake, body weight, tumour growth, and distance run were determined daily. Two weeks later the animals were euthanized and the following tissues were dissected out: tumour, liver, heart, epididymal fat pads, gastrocnemius, epitrochlearis, and soleus muscles. Glucose transport experiments were performed on the epitrochlearis and soleus muscles whereas phospholipid analysis was completed on the gastrocnemius muscle. We observed no effect of either diet or exercise on tumour growth. The glucose transport data demonstrates that short-term voluntary running can cause increased insulin-sensitive transport and that DHA may inhibit transport. DHA-containing diets were associated with increased oxidation products TBARM. In conclusion, exercise benefits on glucose disposal are maintained in tumour-bearing animals but are influenced by fat content and composition. High DHA diets may also increase oxidative damage in muscle through enhanced TBARM production. Key words: DHA, voluntary exercise, sarcoma, muscle transport, C-10
Validity and Reliability of the Huet Questionnaire to Assess Maximal Oxygen Uptake
Authors: Trivel Damien , Calmels Paul , Léger Luc , Busso Thierry , Devillard Xavier , Castells Josiane , Denis Christian
Published: June 2009

The usual fitness tests available to assess maximal oxygen uptake [Formula: see text] a key fitness component, are not particularly useful for epidemiological studies. Questionnaires to assess [Formula: see text] however, are simple, easy to use, and inexpensive. In 1986, Huet developed such a French general questionnaire, which now also has an English version. Its simplicity is interesting as it could be used to survey large populations. The purpose of this study was to assess the validity and reliability of this Huet questionnaire in a sample of healthy French volunteers. A total of 108 subjects were included in this study, 88 males and 20 females. The validity of the questionnaire was checked using correlation coefficients and a Bland-Altman plot between questionnaire estimations and measures of [Formula: see text] obtained with a stress test on a cycle ergometer. An intraclass correlation coefficient (ICC) was also calculated to determine the reliability of the questionnaire. Significant correlation was obtained with the Huet questionnaire and measured [Formula: see text] (r2 = 0.77, p = 0.0001, SEE = 5.97 ml•kg−1•min−1, n = 108). The ICC showed very high reliability (ICC = 0.988, n = 21). The Huet questionnaire is an easy, rapidly administered tool that correlated highly with [Formula: see text] in this sample population. Key words: physical activity, epidemiology, evaluation
Physical Exposures in Work Commonly Done by Women
Authors: Messing Karen
Published: June 2009

The North American workforce is still highly sex-segregated, with most members of each sex in jobs composed primarily of workers of the same sex. This division is accentuated when jobs involve physical demands. Women have traditionally been assigned to tasks whose physical demands are considered to be light. Nevertheless, these tasks can have biological effects, sometimes serious. Phenomena related to physical demands of women's work can be considered in three categories: (a) musculoskeletal and cardiovascular demands of tasks often assigned to women in factories and service work; (b) sex- and gender-specific effects of toxic substances found in the workplace; and (c) interactions between work and the domestic responsibilities of many women. These phenomena are described, using examples recently gathered from workplaces. Effects of biological sex are distinguished, as far as possible, from effects of gender (social roles). Keywords: ergonomics, gender, occupation, anthropometry, toxicity, repetitive movements, static effort
Elevation of Creatine in Red Blood Cells in Vegetarians and Nonvegetarians After Creatine Supplementation
Authors: Maccormick Vanessa M. , Hill Lisa M. , Macneil Lauren , Burke Darren G. , Smith-Palmer Truis
Published: June 2009

The purpose of this study was to examine the effect of a 5-day creatine (CR) supplementation period on red blood cell (RBC) CR uptake in vegetarian and nonvegetarian young women. Blood samples were collected from lacto-ovo vegetarians (VG, n = 6, age 21.8 ± 1.9 yrs) and nonvegetarians (NV, n = 6, age 21.7 ± 1.9 yrs) before and after a 5-day CR loading period (0. 3 g CR/kg lean body mass/day), and from a control group of nonvegetarians (NV, n = 5, age 22.0 ± 0.7 yrs) who did not supplement with creatine. RBC and plasma samples were analyzed for the presence of creatine. Significant increases (p < .05) in RBC and plasma CR levels were found for vegetarians and nonvegetarians following supplementation. The initial RBC CR content was significantly lower (p < .05) in the vegetarian group. There was no significant difference between vegetarians and nonvegetarians in final RBC CR content, suggesting that a ceiling had been reached. As the uptake into both muscle and RBC is moderated by creatine transporter proteins, analysis of the uptake of CR into RBC may reflect the uptake of CR into muscle, offering an alternative to biopsies. Key words: plasma, erythrocyte, loading
Food Habits and Nutritional Status Assessment of Adolescent Soccer Players. A Necessary and Accurate Approach
Authors: Iglesias-Gutiérrez Eduardo , García-Rovés Pablo M. , Rodríguez Carmen , Braga Socorro , Garcia-Zapico Pedro , Patterson Ángeles M.
Published: June 2009

The aim of this study was to assess the food habits and nutritional status of high level adolescent soccer players (N = 33; ages 14-16 yrs) living in their home environment. Body composition (height, mass, skinfolds), biochemical and hematological parameters, performance in soccer-specific tests (sprinting, jumping, intermittent endurance), and dietary intake (weighed food intake method) and related behaviors (nutrient supplement use, daily activity profile) were assessed. Daily energy expenditure and energy intake were 12.5 MJ and 12.6 MJ, respectively. Protein (16% of energy intake; 1.9 g/kg of body mass), lipid (38%), and cholesterol (385 mg) intake were above recommendations, while carbohydrates (45%) were below. The food intake of these adolescents was based on cereals and derivates; meat, fish, and eggs; milk and dairy products; biscuits and confectionery; and oil, butter and margarine, which provided 78% of total energy intake, 85% of proteins, 64% of carbohydrates, 90% of lipids, and 47% of fiber. Although diet provided sufficient iron, 48% of individuals showed iron deficiency without anemia. Based on these results, a well designed nutrition intervention would be advisable for optimizing performance, and especially for promoting healthy eating habits in adolescent soccer players. Key words: young athletes; association football; dietary, anthropometric, biochemical, hematological, and functional measures
Trunk Muscle Activity Increases With Unstable Squat Movements
Authors: Anderson Kenneth , Behm David G.
Published: June 2009

The objective of this study was to determine differences in electromyographic (EMG) activity of the soleus (SOL), vastus lateralis (VL), biceps femoris (BF), abdominal stabilizers (AS), upper lumbar erector spinae (ULES), and lumbo-sacral erector spinae (LSES) muscles while performing squats of varied stability and resistance. Stability was altered by doing the squat movement on a Smith machine, a free squat, and while standing on two balance discs. Fourteen male subjects performed the movements. Activities of the SOL, AS, ULES, and LSES were highest during the unstable squat and lowest with the Smith machine protocol (p <  0.05). Increased EMG activity of these muscles may be attributed to their postural and stabilization role. Furthermore, EMG activity was higher during concentric contractions compared to eccentric contractions. Performing squats on unstable surfaces may permit a training adaptation of the trunk muscles responsible for supporting the spinal column (i.e., erector spinae) as well as the muscles most responsible for maintaining posture (i.e., SOL). Key words: electromyography, concentric, eccentric, resistance training, stabilizers
The Isocapnic Buffering Phase and Mechanical Efficiency: Relationship to Cycle Time Trial Performance of Short and Long Duration
Authors: Bentley David J. , Vleck Veronica E. , Millet Gregoire P.
Published: June 2009

The purpose of this study was to determine the relationship between the isocapnic buffer (βisocapnic) and hypocapnic hyperventilation (HHV) phases as well as performance in a short (20-min) and long (90-min) time trial (TT) in trained athletes. In addition, gross (GE, %) and delta (ΔE, %) efficiency were calculated and the relationship between these variables and the average power output (W) in each TT was determined. Thirteen male endurance athletes (Mean ± SD age 31 ± 6 yrs; body mass 75.6 ± 6.3 kg; height 185 ± 6 cm) completed a continuous incremental test to exhaustion for determination of the βisocapnicand HHV phases. A second submaximal test was used to determine GE and ΔE. The average power output (W) was measured in a 20-min and 90-min cycling TT. The βisocapnicphase (W) was significantly correlated to the average power output (W) in the 20-min TT (r = 0.58; p <  0.05), but not in the 90-min TT (r = 0.28). The HHV phase (W) was not significantly correlated to the average power output in the 20-min or 90-min TT. No significant correlation was found for GE or for ΔE and performance in the TT. The data from this study shows that βisocapnictogether with HHV is not likely to be a useful indicator of cycle TT performance of 20- to 90-min duration. Furthermore, GE and ΔE determined from a submaximal incremental stepwise test are not related to cycling TT performance of different duration. Key words: incremental, correlation, metabolism, athletes, fatigue
Does Intermittent Hypoxia Increase Erythropoiesis in Professional Cyclists During a 3-Week Race?
Authors: Villa José G. , Lucía Alejandro , Marroyo José A. , Avila Concepción , Jiménez Fernando , García-López Juan , Earnest Conrad P. , Córdova Alfredo
Published: June 2009

In this study we examined the effects of intermittent hypoxia exposure (IHE) in a group of professional cyclists (n = 6; age 26 ± 1 yr) competing in the 2001 Vuelta a España. After each daily stage, treated subjects received four 5-min bouts of normobaric IHE (mean O2concentration of 12.6%, simulating a mean altitude of 4,000 m) interspersed with 5-min bouts of breathing hotel room air (normoxia) until completing a total IHE of 20-min duration. The primary outcome, compared to a control group of similar characteristics not receiving IHE (n = 5; age 25 ± 1 yr), was the % increase in erythropoietin (Epo) from the beginning to the end of the Vuelta. Statistical analysis showed that Epo increase tended to be higher (p = 0.052) in the IHE group than in controls (37.4 + 5.8% vs. -4.4 ± 19.5%, respectively). However, IHE had no effect on reticulocytes or erythrocyte count (p > 0.05). Key words: haemoglobin, haematocrit, erythrocytes, reticulocytes, erythropoietin
Resting Membrane Potential of Rat Plantaris Muscle Fibers After Prolonged Indirect Stimulation in Situ: Effect of Glucose Infusion
Authors: Karelis Antony D. , Péronnet François , Gardiner Phillip F.
Published: June 2009

The purpose of this study was to determine whether glucose infusion during prolonged indirect muscle stimulation (50 Hz for 200 ms every 2.7 s at 5 V) would have an effect on resting membrane potential (BMP). The BMP measured at Min 1 in the recovery period following stimulation of the rat plantaris muscle for 60 min in situ was significantly decreased in control rats, but was back to baseline values within 2 min. When glucose was infused ([glucose] ∼10 mM), no change was observed in RMP, and muscle fatigue and the reduction in M-wave peak-to-peak amplitude were both attenuated. However, muscle force and the electrical properties of the membrane were deteriorated both in rats infused with glucose and in control rats at Min 2 during the recovery period, at a time when RMP was not modified. These observations suggest that the effect of increased circulating glucose on fatigue-associated reductions in muscle fiber RMP seems to be modest and short-lived. Therefore, the attenuating effect of elevated glucose on muscle fatigue responses could be through mechanisms other than those associated with maintenance of RMP during fatigue. Key words: Na+/K+ pump, muscle fatigue, muscle force, M-wave, contractility
Skin Cooling Alters the Activation Patterns of Different Heads of the Quadriceps
Authors: Kinugasa Ryuta , Yoshida Kazumasa , Watanabe Takayuki , Kuchiki Kousuke , Horii Akira
Published: June 2009

The purpose of this study was to examine the effect of selective skin cooling over m. vastus lateralis (VL) on the activation patterns of quadriceps femoris muscle during knee extension exercise (KEE) using muscle function magnetic resonance imaging (mfMRI). The isometric force production of the right thigh was tested in 7 healthy young men at maximum voluntary contraction (MVC), and the transverse relaxation time (T2) value was taken from mfMR images at rest and immediately after KEE with 4 sets of 10 repetitions at a load equal to 60% of their 10-rep maximum, with and without skin cooling. The cooling was carried out by ice pack on the surface of the skin of the VL for 3 min before resting mfMRI and MVC tests, and before KEE, during KEE, and during the KEE rest intervals. The percent change in T2 of the m. vastus intermedius was significantly increased by skin cooling in comparison to the change without skin cooling, p < 0.05. This result suggests that skin cooling alters the activation pattern of the different heads of the quadriceps. Key words: cold, mfMRI, synergy, recruitment, neuromuscular plasticity
Protective Effects of Moderate Exercise With Dietary Vitamin C and E on Blood Antioxidative Defense Mechanism in Rats With Streptozotocin-Induced Diabetes
Authors: Naziroğlu Mustafa , Butterworth Peter J.
Published: June 2009

Daily moderate exercise and supplementation of vitamins C and E (VCE) can be beneficial in diabetes by ameliorating the effects of free radical production. The present study sought to analyze the effect of moderate exercise accompanying VCE supplementation on lipid peroxidation (LP) and antioxidative systems in the blood of streptozotocin-induced diabetic rats. Forty female Wistar rats were randomly divided 4 groups. The 1st and 2nd groups served as the control and diabetic groups, respectively. The 3rd group was the diabetic-exercise group. The 4th group, also diabetic-exercise rats, received VCE-supplemented feed. Animals in the exercised groups were moderately exercised on a treadmill 5 days a week for 3 weeks. Diabetes was induced on Day 0 of the exercise. Plasma and red blood cell (RBC) samples were taken from all animals on Day 20. Glutathione peroxidase, catalase, and reduced glutathione levels in plasma and RBCs, and vitamins A, E, and β-carotene in plasma were lower in diabetic rats than in control animals, whereas there was a significant increase in platelet counts in both plasma and RBC LP levels. The decreased antioxidant enzymes and vitamins, and the increased LP levels and WBC counts, did improve through exercise only, although their levels were mostly increased by exercise + VCE supplementation. There were no significant changes in the hemoglobin and hematocrit values in the 4 groups. In conclusion, these data demonstrate an increase in LP in the blood of diabetic animals whereas there was a decrease in the antioxidant vitamins and enzymes. However, dietary VCE with moderate exercise may strengthen the antioxidant defense system by decreasing reactive oxygen species. Key words: hyperglycemia, glutathione peroxidase, oxidative stress, hematological values
Immune Alterations, Lipid Peroxidation, and Muscle Damage Following a Hill Race
Authors: Simpson Richard J. , Wilson Martin R. , Black James R. , Ross James A. , Whyte Greg P. , Guy Keith , Florida-James Geraint D.
Published: June 2009

Hill races usually include large downhill running sections, which can induce significant degrees of muscle damage in a field setting. This study examined the link between muscle damage, oxidative stress, and immune perturbations following a 7-km mountainous hill race with 457 m of ascent and 457 m of descent. Venous blood samples were taken from 7 club level runners before, immediately after, and 48 hrs postrace. Samples were analysed for total and differential leukocyte counts, markers of muscle damage (CK), lipid peroxidation (MDA), and acute phase proteins (CRP; fibrinogen; α-1-ACT). The total antioxidant status (TEAC) and plasma levels of the proinflammatory cytokines IL-6, IL-8, and TNF-α were also determined. Subjective pain reports, and plasma activities of CK, MDA, and circulatory monocytes reached peak values at 48 hrs postrace (p <  0.05). TEAC and the cytokine IL-8 increased immediately after the race (p <  0.05). Plasma TNF-α remained unchanged (p > 0.05). Despite the reports of muscle damage and soreness, no evidence of an acute phase response was observed (p > 0.05), which may be explained by the failure of the race to induce a plasma TNF-α response. Future studies should examine the link between muscle damage, oxidative stress, and the acute phase response following hill races of longer duration with larger eccentric components. Key words: acute phase response, cytokines, antioxidant capacity, creatine kinase, field study