bluuebunny/crossref_metadata_2025 huggingface dataset:
Dietary Fat Intake, Supplements, and Weight Loss
Authors: Dyck David J.
Published: June 2009

Although there remains controversy regarding the role of macronutrient balance in the etiology of obesity, the consumption of high-fat diets appears to be strongly implicated in its development. Evidence that fat oxidation does not adjust rapidly to acute increases in dietary fat, as well as a decreased capacity to oxidize fat in the postprandial state in the obese, suggest that diets high in fat may lead to the accumulation of fat stores. Novel data is also presented suggesting that in rodents, high-fat diets may lead to the development of leptin resistance in skeletal muscle and subsequent accumulations of muscle triacylglycerol. Nevertheless, several current fad diets recommend drastically reduced carbohydrate intake, with a concurrent increase in fat content. Such recommendations are based on the underlying assumption that by reducing circulating insulin levels, lipolysis and lipid oxidation will be enhanced and fat storage reduced. Numerous supplements are purported to increase fat oxidation (carnitine, conjugated linoleic acid), increase metabolic rate (ephedrine, pyruvate), or inhibit hepatic lipogenesis (hydroxycitrate). All of these compounds are currently marketed in supplemental form to increase weight loss, but few have actually been shown to be effective in scientific studies. To date, there is little or no evidence supporting that carnitine or hydroxycitrate supplementation are of any value for weight loss in humans. Supplements such as pyruvate have been shown to be effective at high dosages, but there is little mechanistic information to explain its purported effect or data to indicate its effectiveness at lower dosages. Conjugated linoleic acid has been shown to stimulate fat utilization and decrease body fat content in mice but has not been tested in humans. The effects of ephedrine, in conjunction with methylxanthines and aspirin, in humans appears unequivocal but includes various cardiovascular side effects. None of these compounds have been tested for their effectiveness or safety over prolonged periods of time. Key words: carnitine, conjugated linoleic acid, ephedrine, pyruvate, hydroxycitrate
L'exercice Intermitent Aérobie Et Sa Relation Avec La Performance En Sports D'endurance
Authors: Babineau Charles
Published: June 2009

not available
Field Testing of in Cross-Country Skiers With Portable Breath-by-Breath System
Authors: Doyon Kristopher H. , Perrey Stéphane , Abe Daijiro , Hughson Richard L.
Published: June 2009

Peak aerobic exercise responses were determined in 8 competitive cross-country skiers during field-testing and during an incremental treadmill test (TM) to determine peak oxygen uptake [Formula: see text], heart rate, and oxygen pulse. Field testing consisted of maximal effort roller skiing using diagonal stride (DS) and double poling (DP) techniques. [Formula: see text] was measured during roller skiing by the portable Cosmed K4b2 breath-by-breath system. The portable system was compared against a standard laboratory mixing box system, and no differences were found across the full range of [Formula: see text]. During DS, [Formula: see text] and oxygen pulse were not different from TM, whereas peak HR was lower. With DP, [Formula: see text] and oxygen pulse were less than DS or TM, whereas peak HR was less than with TM but not different from DS. These results demonstrate the validity and utility of the portable breath-by-breath system for measurement of aerobic energy demand of athletes as they carry out their normal activity. Key words: oxygen uptake, oxygen pulse, Cosmed K4b2, athlete
Exercise and Lactation: Are They Compatible?
Authors: Carey Gale B. , Quinn Timothy J.
Published: June 2009

Lactation is an energy-demanding physiological process for the maternal organism and life-giving for the offspring. Likewise, exercise is an energy-demanding process. This review addresses the Compatibility of exercise during lactation. Human studies suggest no detrimental effect of exercise during lactation on milk composition and volume, infant growth and development, or maternal health. Studies also demonstrate improved cardiovascular fitness in lactating, exercising women and suggest a quicker return to pre-pregnancy body weight and a more positive sense of well-being, compared to sedentary controls. Findings from rodent studies, although of questionable value for humans, have generally shown no detrimental influence of exercise during pregnancy and lactation on pup growth and development. To date, findings suggest that exercise and lactation are compatible activities. Key words: maternal health, infant growth, breast milk composition, breast milk volume, cardiovascular fitness
Origins and Clinical Relevance of Sarcopenia
Authors: Roubenoff Ronenn
Published: June 2009

Sarcopenia is the loss of muscle mass and strength that occurs with normal aging. Because sarcopenia is not the result of a disease, it is seen in all aged adults. Sarcopenia markedly increases the risk of disability and loss of functional capacity in the elderly. The mechanisms underlying sarcopenia are complex and are reviewed here. It is not clear at this time which factors are most important in determining the severity or rate of development of sarcopenia. While progressive resistance training clearly can reverse and prevent sarcopenia, little is known about the mechanisms by which aged muscle adapts to training, or whether these adaptations reflect reversal of direct pathophysiological processes or compensation by activation of separate pathways from those leading to the deterioration in the first place. As populations in developed countries continue to age, diagnosing, treating, and preventing sarcopenia will be progressively more important to the health and well-being of modern societies. Key words: aging, muscle, cytokines
Functional and Metabolic Consequences of Sarcopenia
Authors: Vandervoort Anthony A. , Symons T. Brock
Published: June 2009

Sarcopenia associated with the normal aging process is often combined with the detrimental effects of a sedentary lifestyle in older adults, leading to a significant reduction in reserve capacity of the neuromuscular system. A clear example of the aging effect is the pattern of reduction in muscle strength after the sixth decade for both isometric and concentric contractions. However, older adults are relatively stronger for movements in which muscles lengthen, due to the inherent advantage of eccentric contractions, plus their stiffer muscle structures and prolonged myosin cross-bridge cycles. Also, the capacity for physiological adaptations in the motor pathways remains into very old age when an appropriate exercise stimulus is given, and older adults can obtain adaptations in both enhanced neural control of motor units and increased protein synthesis leading to moderate muscle hypertrophy. Since periods of sedentary lifestyle or bed rest due to illness can have severe detraining consequences on the neuromuscular function of an older person, long-term prevention strategies are advocated to avoid excessive physical impairments and activity restrictions in this age group. Keywords: aging, muscle, strength, contraction, atrophy
Back Fitness and Back Health Assessment Considerations for the Canadian Physical Activity, Fitness and Lifestyle Appraisal
Authors: Albert Wayne J. , Bonneau Jean , Stevenson Joan M. , Gledhill Norm
Published: June 2009

The Canadian Physical Activity, Fitness, and Lifestyle Appraisal (CPAFLA) is used as a measure for the health-related fitness of the general population. The CPAFLA includes an evaluation of back health, which is comprised of abdominal muscular endurance (partial curl-ups) and trunk flexion (sit and reach). This paper reviews the occupational, lifestyle, and physical risks associated with back pain and examines the measurement techniques used to assess health-related fitness components of back health in fitness assessments, such as the CPAFLA. Recommendations for future revisions of the CPAFLA's back health assessment and future research needs are presented. Key words: lower back pain, physical activity, muscular fitness, health and lifestyle, back health
A Decrease in Soleus Muscle Force Generation in Rats After Downhill Running
Authors: Kyparos Antonios , Matziari Chrysoula , Albani Maria , Arsos Georgios , Sotiriadou Sofia , Deligiannis Asterios
Published: June 2009

The purpose of the present study was to investigate the immediate and 48-hr post-exercise effects of eccentric contraction-biased exercise on the contractile properties of the soleus muscle in situ. Adult male Wistar rats were categorised into sedentary control rats (n = 10), rats studied immediately (n = 10), and rats studied 48 hours after the exercise (n = 10). The exercise protocol consisted of a 90-min intermittent downhill running (-16°, 16 m/min) on a motor-driven treadmill. The contractile properties of the soleus muscle were recorded following i.p. chloral hydrate anaesthesia. Isometric twitch force (Pt), time-to-peak tension (TPT), half-relaxation time (1/2 RT), and tetanic force at stimulation frequencies of 40, 80, and 100 Hz were recorded. A low-frequency muscle fatigue protocol (stimulation at 4 Hz for 5 min) was applied to test for fatigability. The main findings indicated that Pt generation dropped both immediately and 48 hr after the exercise, while tetanic force was partially restored after 48 hr. Exercise-induced E-C coupling failure and contractile machinery disorganisation due to muscle injury are put forward as the main force reduction causes. Key words: eccentric exercise, muscle injury, SR, E-C coupling, tension recording
Gender Differences in Temperature and Vascular Characteristics During Exercise Recovery
Authors: Marchand Ingrid , Johnson Dominique , Montgomery David , Brisson Guy R. , Perrault Hélène
Published: June 2009

Temperature and vascular responses during exercise recovery were examined in men and women of similar age and fitness status ([Formula: see text] 76 ± 5 vs 73 ± 5 mL O2/kg Fat Free Mass • min). Forearm blood flow (venous occlusion plethysmography: FBF), rectal (Trectal) and forearm skin (Tskin) temperatures (°C) were measured before and every 15 min up to 105 min (t105) during recovery from a 45-min run at 75% of [Formula: see text]. Results indicate Trectal decreased to pre-exercise levels within 25 min in men but reached and remained at values lower than baseline between 60 and 105 min of recovery in women. From 90 to 105 min of recovery. Tskin was lower in women than men (t105: 29.0 ± 1.3 vs 30.7 ± 1.5; p < .05). Recovery FBF (mL/100mL • min) was higher in men than women from the start (6.2 ± 1.9 vs 4.9 ± 1.9) to the end of recovery (t105 = 1.7 ± 0.6 vs 2.6 ± 1.1) (p < .05). Heat flux calculated at the forearm was higher in women and increased throughout the last hour of recovery (p < .05). Further investigations are needed to examine mechanisms underlying failure of post-exercise core and skin temperatures in women to stabilize at pre-exeivise levels. Key words: exercise recovery, peripheral vascular resistance, thermoregulation
Effects of Creatine Monohydrate Supplementation During Combined Strength and High Intensity Rowing Training on Performance
Authors: Syrotuik Daniel G. , Game Alex B. , Gillies Ellen M. , Bell Gordon J.
Published: June 2009

This study investigated the effect of creatine monohydrate (Cr) supplementation on performance and training volume in rowers. Twenty-two rowers trained with continuous and interval rowing and resistance training 4 and 2 days/week, respectively, for 6 weeks. Cr supplementation consisted of a 5-day load (0.3 g/kg−1•day−1) followed by a 5-week maintenance dose (0.03 g/kg−1•day−1) while training. Five days of Cr loading did not change body composition, repeated interval rowing performance, 2,000-m rowing times, or strength performance. Five additional weeks of training with a maintenance dose of Cr or placebo significantly improved body composition, [Formula: see text] 2,000-m rowing times, repeated power interval performance, and strength to a similar extent in both groups. Subjects training with Cr did not perform more repetitions per set of strength exercise nor produce or maintain higher power outputs during repeated rowing sessions. Cr supplementation did not increase performance or training volume over a placebo condition in rowers that performed a combined high intensity rowing and strength program. Key Words: ergogenic, anaerobic, resistance training, interval training
Evaluation of the Monark Wingate Ergometer by Direct Measurement of Resistance and Velocity
Authors: Macintosh Brian R. , Bryan Shirley N. , Rishaug Peter , Norris Stephen R.
Published: June 2009

The purpose of this study was to assess the accuracy of the new basket-loaded Wingate ergometer introduced by Monark (Model 834E). Velocity was measured directly from the pedal switch while tension was measured with transducers on each end of the brake lacing. Moment of inertia of the flywheel was determined and accounted for in the calculation of power. Constant load tests (39.24 to 98.1 N), were done at pedaling speeds from 80 to 140 r•min−1 (flywheel angular velocity = 30-50 rad•s−1). The load transmitted to the lacing at the front and back of the flywheel was 95.5 ± 0.8% (mean ± SEM) and 6.71 ± 0.8%, respectively, of the load in the basket. Thus, the resultant tension (front minus back) was on average 88.8 ± 0.57% of the applied load. The velocity recorded by the Monark Wingate Ergometer computer program (MWECP) was the same (100.4 ± 1.56%) as that determined from the pedal switch directly. Five male mountain bikers performed a 30-s all-out test. Peak power calculated by MWECP (1181 ± 55W) was always higher (p < .01) than that calculated from direct measures of tension and velocity (1102 ± 66W), when not taking into account the moment of inertia. These experiments suggest that the basket-loaded Monark Wingate ergometer does not provide a correct calculation of power because of incomplete load transmission to the flywheel. Key words: power, anaerobic power, moment of inertia, cycle ergometer
Human Pregnancy: An Integrated Model for the Study of Physiological Contril Systens
Authors: Heenan Aaron Paul
Published: June 2009

not available
Cellular and Molecular Basis of Age-Related Sarcopenia
Authors: Welle Stephen
Published: June 2009

Sarcopenia, the decline in muscle bulk and performance associated with normal aging, is an important component of frailty in the elderly. The gradual loss of both motor nerves and muscle fibers during senescence appears to be the major problem. Atrophy (especially in fast-twitch fibers) and impaired function of the surviving cells also contribute to sarcopenia. Although skeletal muscle has the capacity to regenerate itself, this process is not activated by the gradual age-related loss of muscle fibers. The endocrine, autocrine, and paracrine environment in old muscle is less supportive of protein synthesis, reinnervation of muscle fibers, and satellite cell activation, proliferation, and differentiation. Lifelong exposure of DNA to free radical damage results in accumulation of somatic mutations in nerves and muscle fibers. Reduced protein synthesis leads to atrophy, and slower fractional protein turnover contributes to longer retention of proteins that may have been damaged by free radicals. Many genes are differentially expressed in young and old muscle, but additional research is needed to determine which of these genes have a significant role in the pathogenesis or adaptation to sarcopenia. Key words: muscle atrophy, motor neurons, gene expression, hormonal effects in muscle, muscle protein metabolism
The Putative Roles of Adenosine in Insulin- and Exercise-Mediated Regulation of Glucose Transport and Glycogen Metabolism in Skeletal Muscle
Authors: Thong Farah S.L. , Graham Terry E.
Published: June 2009

Skeletal muscle is the primary site of whole-body glucose disposal and is vital in determining the overall insulin sensitivity and carbohydrate management. Insulin and physical exercise are important stimuli for muscle glucose transport and glycogen metabolism. While it is known that both insulin and contraction stimulate muscle glucose uptake and glycogen metabolism, the post-receptor mechanisms are not completely understood. Local metabolic factors, such as adenosine, have been suggested to play a role in insulin and contraction regulation of carbohydrate metabolism in skeletal muscle. While adenosine has clearly been shown to potentiate insulin-stimulated glucose transport in adipocytes and heart muscle, its role in carbohydrate metabolism in skeletal muscle is less clear, with numerous diverging findings published to date. This review article summarizes findings on the putative roles of adenosine in insulin and exercise-mediated regulation of carbohydrate metabolism and the signalling pathways proposed to be central to these metabolic stimuli in skeletal muscle. Key words: carbohydrate metabolism, adenosine receptor, signal transduction, insulin resistance, diabetes mellitus, obesity
The Lactate Minimum Test for Cycling: Estimation of the Maximal Lactate Steady State
Authors: Macintosh Brian R. , Esau Shane , Svedahl Krista
Published: June 2009

This study evaluated the reliability and validity of the lactate minimum test (LMT), an incremental test given after lactic acidosis wax induced by sprint exercise. This test is purported to accurately estimate the intensity of exercise at which the transport of lactate into and out of the blood is in equilibrium (maximal lactate steady state or MLSS) and should be a good predictor of endurance performance. Fourteen athletes (mean age 27.2 ± 3.7 yrs) completed the following on Kreitler rollers: (a) two 20-km time-trials (35.1 ± 3.3 and 35.7 ± 3.5 km • hr−1, p < .05); (b) two LMTs yielding lactate minimum speeds (LMS) of 33.6 ± 3.4 and 33.4 ± 3.1 km • hr−1 (p > 0.6); and (c) four constant intensity rides, at speeds bracketing the LMS. At 33.5 ± 3.1 km • hr−1 plasma lactate concentration decreased 0.4 ± 1.6 mM from 10 to 30 min. Plasma lactate increased 1.6 ± 0.7 mM white riding 0.9 ± 0.9 km • hr−1 faster. The LMT is a reliable (r2 = 0.904) and valid method to predict MLSS and a good predictor of endurance performance (LMT vs. 20-km time-trial, r2 = 0.86). Key words: anaerobic threshold, endurance, blood lactate
Assuring Gender Equity in Recruitment Standards for Police Officers
Authors: Shephard Roy J. , Bonneau Jean
Published: June 2009

Human Rights Tribunals require application of non-discriminatory fitness standards in the hiring, promotion, and retention of employees. This issue has become controversial for public safety officers such as police, where differences in average levels of absolute fitness between men and women cause a high proportion of female applicants to fail many entrance tests. The present review summarizes the impact on physical working capacity of commonly encountered gender differences in size, body composition, haemoglobin levels, and muscular strength. The principles applied in designing content- and construct-validity occupational fitness tests are described, and Human Rights policies are reviewed in the light of the Meiorin judgment. Criteria are indicated for establishing a bona-fide occupational fitness requirement, and description is given of the approach used in developing standards that satisfy these criteria. Requirements are based on the task to be accomplished. The potential training response of female applicants is likely at least to match that of their male peers, and the needs of female police recruits are thus best accommodated by providing every opportunity to augment fitness to the required minimum level. The main weakness of any current requirement is that most police forces do not yet apply an equivalent criterion to older incumbent officers, where similar issues may arise. Key words: human rights, occupational fitness, police officers, test validity
Ultra-sound Imaging for Precision Implantation of a Multi Sensor Temperature Probe in Skeletal Muscle Tissue
Authors: Kenny Glen P. , Reardon Frank D. , Ducharme Michel B. , Reardon Mark L. , Zaleski Wytek
Published: June 2009

A technique for implanting multi sensor temperature probes in muscle tissue was developed to optimize the accuracy of the tissue temperature measurements and the internal localization of the probe. Real time ultra-sound imaging was used to (a) determine the best perpendicular insertion tract, (b) guide the insertion of the probe in order to avoid major blood vessels, and (c) verify the insertion point relative to discernable anatomic reference structures such as arteries and bone. Key words: muscle temperature, temperature transients, heat content
Tissue Temperature Transients in Resting Contra-Lateral Leg Muscle Tissue During Isolated Knee Extension
Authors: Kenny Glen P. , Reardon Frank D. , Ducharme Michel B. , Reardon Mark L. , Zaleski Wytek
Published: June 2009

This study was designed to evaluate the role of non-active tissue in the retention and dissipation of heat during and following intense isolated muscle activity. Six subjects performed an incremental isotonic test (constant angular velocity, increases in force output) on a KIN-COM' isokinetic apparatus to determine their maximal oxygen consumption during single knee extensions [Formula: see text] In a subsequent session, a thin wire multi-sensor temperature probe was inserted into the left vastus medialis under ultrasound guidance at a specific internal marker. The deepest temperature sensor (tip, Tmu10) was located ∼10 mm from the femur and deep femoral artery with 2 additional sensors located at 15 (Tmu25) and 30 (Tmu40) mm from the tip. Implant site was midway between and medial to a line joining the anterior superior iliac spine and base of patella. Esophageal temperature (Tes) temperature was measured as an index of core temperature. Subjects rested in a supine position for 60 min followed by 30 min of seated rest in an ambient condition of 22 °C. Subjects then performed 15 min of isolated single right knee extensions against a dynamic resistance on a KIN COM corresponding to 60% of [Formula: see text] at 60° • sec−1. Exercise was followed by 60 min of seated rest. Resting Tes was 37 °C while Tmu10, Tmu25, and Tmu40 were 36.58, 36.55 and 36.45 °C, respectively. Exercise resulted in a Tes increase of 0.31 °C above pre-exercise resting. Tmu of the non-exercising leg increased 0.23, 0.19 and 0.09 °C for Tmu10, Tmu25, and Tmu40, respectively. While Tes decreased to baseline values within ∼15 min of end-exercise, Tmu10 reached resting values following ∼40 min of recovery. These results suggest that during isolated muscle activity, convective heat transfer by the blood to non-active muscle tissue may have a significant role in maintaining resting core temperature. Key words: heat load, thermoregulation, hyperthermia
Effect of Fourteen Days of Acclimatization on Athletic Performance in Tropical Climate
Authors: Voltaire Bruno , Galy Olivier , Coste Olivier , Racinais Sébastien , Callis André , Blonc Stephen , Hertogh Claude , Hue Olivier
Published: June 2009

In order to study the acclimatization process over 14 days of exposure to tropical climate, 9 triathletes performed 4 outdoor indirect continuous multistage tests in both thermoneutral and tropical conditions. The thermoneutral test (TN, 14 °C, 45% rh) was performed before traveling to the tropical area (Martinique, FWI). The tropical tests were performed 2, 8, and 14 days after arrival (32.9 °C, 78% rh). During each trial, we measured tympanic temperature, sweat rate, body mass loss, heart rate (HR), and performance. The results showed that 1) the mean tympanic temperature was greater in T2 (P < .001), T8 (P < .01) and T14 (P < .01) than in TN and significantly lower in T14 than in T2 (P < .05); 2) the mean sweat rate was significantly greater (P < .001) in T2, T8 and T14 than in TN and significantly greater (P < .05) in T8 and T14 than in T2; 3) the body mass loss after trials was significantly greater (P < .001) in T2, T8 and T14 than in TN and significantly greater (P < .05) in T8 and T14 than in T2; 4) the mean HR and HR at rest were significantly higher (P < .005) in T2 than in TN, T8, T14 and the mean HR was significantly lower (P < .05) in T14 than in the other trials; and 5) the performance time was significantly lower in T2 (P < 0.02), T8 (P < 0.03) and T14 (P < 0.05) than in TN. We concluded that 14 days of exposure to tropical climate led to changes in physiological parameters but were still insufficient to ensure complete acclimatization in well-trained athletes. The hot/wet climate induced impairment of physiological responses and performance that were still evident on the 14th day. Keywords: triathletes, aerobic performance, jet lag, dehydration, hyperthermia
Effects of Conjugated Linoleic Acid (CLA) on Immune Responses, Body Composition and Stearoyl-CoA Desaturase
Authors: Ntambi James M. , Choi Youngjin , Park Yeonhwa , Peters Jeffrey M. , Pariza Michael W.
Published: June 2009

Conjugated linoleic acid (CLA) has shown a wide range of biologically beneficial effects; reduction of incidence and severity of animal carcinogenesis, reduction of the adverse effects of immune stimulation, reduction of severity of atherosclerosis, growth promotion in young rats, and modulation of stearoyl-CoA desaturase (SCD). One of the most interesting aspects of CLA is its ability to reduce body fat while enhancing lean body mass which is associated with the trans-10,cis-12 isomer of CLA. The effects of CLA are unique characteristics that have not been observed with other polyunsaturated fatty acids. In this review, we will focus on the effects of CLA on immune responses, body compositional changes and stearoyl-CoA desaturase. Key words:trans-10,cis-12 CLA
Effects of Prohormone Supplementation in Humans: A Review
Authors: Ziegenfuss Tim N. , Berardi John M. , Lowery Lonnie M. , Antonio Jose
Published: June 2009

Despite a relative dearth of information on their effects, supplementation with prohormones has become a popular practice. Unlike synthetic anabolic-androgenic steroids, many of these over-the-counter androgens are produced endogenously by adrenal, gonadal and peripheral steroidogenic pathways as part of the normal sexual and reproductive hormonal milieu. It has been contended that peripheral enzymatic conversion of these prohormones to testosterone or nortestosterone (via ingestion of androstenedione/androstenediol or 19-nor-androstenedione/androstenediol, respectively) might lead to anabolic and/or ergogenic effects. Existing data suggest that acute oral ingestion of >= 200 mg androstenedione or androstenediol modestly and transiently increases serum testosterone concentrations in men; however, this is accompanied by greater increases in circulating estrogen(s). At doses < 300 mg/d, oral supplementation for as long as 12-weeks with androstenedione or androstenediol has no effect on body composition or physical performance and decreases high-density lipoprotein cholesterol. Similarly, oral supplementation with norandrostenedione and norandrostenediol for up to eight weeks has no effect on body composition or physical performance. In light of these data, new products have been developed that use alternative modes of prohormone administration (sublingual/transbuccal and cyclodextrin-complexation). Future studies should critically examine the effects of these approaches. However, within the framework of the research reviewed, over-the-counter oral prohormone supplementation is ineffective at increasing muscle mass or athletic performance. As a result of the potential health concerns that have been raised, the risk to benefit ratio of using these substances orally seems unfavorable. Keywords: androstenediol, androstenedione, norandrostenedione, norandrostenediol, ergogenic aid
Dietary Creatine Supplementation and Exercise Performance: Why Inconsistent Results?
Authors: Lemon Peter W.R.
Published: June 2009

Over the past few years there has been considerable interest in both the use of creatine (Cr) supplementation by athletes and the documentation of its effects by scientists. Some believe that this nitrogen-containing compound found in meat and fish has a performance-enhancing capability as important for brief intense exercise efforts as dietary carbohydrate is for activities where glycogen supplies limit performance. The mechanisms thought to be responsible for any ergogenic effect of acute (few d) Cr supplementation include: increased stores of muscle phosphocreatine (PCr), faster regeneration of PCr during exercise recovery, enhanced adenosine triphosphate (ATP) production from glycolysis secondary to increased hydrogen ion buffering, and/or possible shortened post contraction muscle relaxation time. With chronic (wk & mo) supplementation when combined with strength training, Cr may alter muscle protein metabolism directly (via decreasing protein breakdown or increasing synthesis) and/or indirectly as a result of a greater training load made possible by its acute ergogenic effects on strength and power. Cr supplementation is not banned by the International Olympic Committee and, with the exception of a small increase in body mass (∼1 kg) over the initial 3-6 d, does not appear to have any adverse side effects, at least with short-term use. Few scientific data are available for more prolonged use (mo or y) but considering the large numbers of athletes using Cr over the past 6+ y and the absence of reported problems, it may be that the often discussed somewhat nebulous long term adverse effects are presently being overestimated. Intakes of 285-300 mg Cr/kg body mass • d−1 over 3-6 d or 30-50 mg/kg body mass • d−1 over ∼4 wk are sufficient to produce benefits (muscle mass and high intensity power gains); however, not all study results are consistent. The focus of this review is to outline some possible explanations for the inconsistent observations reported in the literature. Clearly, if proven to be consistent the benefits of Cr supplementation could extend far beyond the athletic arena to include individuals who experience muscle weakness for a variety of other reasons (e.g., age/disuse, muscle disease, exposure to microgravity, etc). Key words: creatine monohydrate, phosphocreatine, adenosine triphosphate, intense exercise, performance benefits, adverse effects, dosage
Reliability Assessment of Two Militarily Relevant Occupational Physical Performance Tests
Authors: Pandorf Clay E. , Nindl Bradley C. , Montain Scott J. , Castellani John W. , Frykman Peter N. , Leone Cara D. , Harman Everett A.
Published: June 2009

To determine the number of test sessions needed to stabilize performance on two military occupational physical tests and to assess their reliability, 10 male soldiers (22 ± 3 yrs, 183 ± 7 cm, 87 ± 8 kg) performed both an indoor 6-station obstacle course (OC) and a repetitive box-lifting task (RBLT). The OC consisted of 46 cm-high hurdles, zigzag sprint, low crawl, horizontal pipe shimmy, 1.4 m wall traversal, and straight sprint. The RBLT required subjects to lift 20.5 kg boxes, continuously for 10 minutes, from the ground onto 1.3 m high platforms positioned 2.4 m apart. The OC mean ± SD times (s), for sessions 1-4 respectively, were 37.4 ± 2.2, 35.8 ± 2.5, 34.7 ± 2.1, and 34.5 ± 1.7 seconds. The number of boxes lifted was 177 ± 31, 194 ± 28, 189 ± 32, and 186 ± 37 for the RBLT. Performance stabilized on the 3rd session for the OC (7% improvement over first trial, p < 0.05) and on the 2nd session for the RBLT (9% improvement over first trial, p < 0.05). The intraclass correlation coefficients were 0.92 and 0.94 for the OC and RBLT, respectively. This study demonstrates that both are reliable tests, but they do require administration of 1 single-trial session of RBLT and 2 two-trial sessions of OC before highly reliable performance data are obtained. Key words: repetitive box lifting, obstacle course, soldiers, muscular endurance
Estradiol Effects on the Growth Hormone/Insulin-Like Growth Factor-1 Axis in Amenorrheic Athletes
Authors: Waters Debra L. , Dorin Richard I. , Qualls Clifford R. , Ruby Brent C. , Baumgartner Richard N. , Robergs Robert A.
Published: June 2009

Disruption of the growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis has been reported and studied in menopause, hypothalamic amenorrhea, and anorexia nervosa, but not in weight-stable amenorrheic athletes. We investigated the effects of short-term transdermal estradiol on basal and exercise-stimulated serum GH, IGF-1, and associated binding proteins (IGFBP-1 and IGFBP-3) in seven weight-stable female amenorrheic athletes with percentage body fats greater that 12%. Each subject received a 72 h placebo patch followed by 144 h of transdermal estradiol. Serum samples for GH, IGF-1, IGFBP-1, and IGFBP-3 were obtained at baseline (t1), 72 hr (t2), 144 hr (t3), and during three 90-minute trials of aerobic exercise. Basal, and exercise GH, IGF-1, and IGFBP-1 were not different between trials. Baseline IGFBP-3 decreased from t1 to t2 (p = 0.04) and serum free fatty acids increased from t1 to t2, and t1 to t3 (p = 0.04, and 0.02 respectively). These findings differ from postmenopausal women, and women having weightloss-associated amenorrhea, suggesting that estrogen, exercise, and nutritional deficiencies may have independent effects on the GH/IGF-1 axis. Key words: transdermal estradiol, insulin-like growth factor binding protein-3, insulin-like growth factor binding protein-1, free fatty acids
Physical Fitness and Plasma Non-Enzymatic Antioxidant Status at Rest and After a Wingate Test
Authors: Groussard Carole , Machefer Guillaume , Rannou Françoise , Faure Henri , Zouhal Hassane , Sergent Odile , Chevanne Martine , Cillard Josiane , Gratas-Delamarche Arlette
Published: June 2009

We tested seven physical education students whether 30-s sprint anaerobic exercise (Wingate test) would result in oxidative stress (evaluated by lipid radical levels) sufficient to alter plasma non-enzymatic antioxidant status (plasma uric acid, ascorbic acid, α-tocopherol, β-carotene). This study demonstrates that 1) Wingate test increases plasma uric and ascorbic acid concentrations (p < .05), and decreases plasma α-tocopherol and β-carotene levels (p < .05); 2) lipid radical levels at rest and sprint performance are negatively correlated with resting plasma uric acid and α-tocopherol concentrations (p < .05). In conclusion, this study 1) demonstrates that a 30-s sprint anaerobic exercise is associated with acute changes in plasma non-enzymatic antioxidant status, 2) indicates that the subjects with largest leg peak power are those who exhibit the lowest plasma antioxidant status at rest (uric acid and α-tocopherol), 3) and suggests that antioxidant intake by maintaining plasma antioxidant concentration at rest in the normal range might protect athletes against oxidative stress induced by exercise. Key words: ascorbic acid, α-tocopherol, β-carotene, uric acid, oxidative stress
Relationships Between Lumbar Flexibility, Sit-and-Reach Test, and a Previous History of Low Back Discomfort in Industrial Workers
Authors: Grenier Sylvain G. , Russell Caryl , Mcgill Stuart M.
Published: June 2009

The sit-and-reach (S&R) test is often included in standard fitness tests (e.g., Canadian Physical Activity, Fitness and Lifestyle Appraisal [CPAFLA]), justified on the assumption that it is an indicator of low back health. Two issues were examined here: Is low back flexibility linked to having a history of low back disorders? And is the S&R test an indicator of low back flexibility? The relationship between S&R test scores, lumbar range of motion, and having a history of low back discomfort was examined in 72 asymptomatic (at test time) industrial workers (70 M, 2 F; mean age 35 ys; height 1.79 m; mass 84.7 kg). The S&R test, among many collected, was performed according to the CPAFLA guidelines. History of low back discomfort (LBD) was categorized based on whether or not time was lost from work. The S&R test was unable to distinguish between those with a history of LBD and those without. Specific lumbar sagittal range of motion could make this distinction. A moderate correlation (r = 0.42) surfaced between S&R and lumbar flexibility. This study suggests that the value of S&R as an indicator of previous back discomfort is questionable and there may be better indicators for inclusion in the CPAFLA. Key words: trunk flexibility, fitness testing, range of motion, low back pain, lumbar kinematics
Effets du statut socioéconomique sur l'activité physique d'enfants prépubères
Authors: Melin Alexandre , Obert Philippe , Bonnet Pierre , Courteix Daniel
Published: June 2009

In order to assess possible influences of socioeconomic status and gender on habitual physical activity (HPA) of prepubertal French children, daily heart rate was 24-hr-monitored in 65 normal subjects for 2 days in the same school week. HPA was evaluated as the mean daily time spent at heart rates greater than 140 bpm (tFC > 140), 160 bpm (tFC > 160), 50% (tFC > 50%), and 70% (tFC > 70%) of the heart rate reserve. An effect of socioeconomic status (determined by questionnaire) was found in boys, with HPA being greater in the underprivileged ones (tFC > 140: 51.8 ± 30.1 vs 33.0 ± 14.1 min, p < .05; tFC > 160: 22.7 ± 16.6 vs 11.1 ± 7.4 min, p < .05; tFC > 50%: 61.4 ± 33.5 vs 46.5 ± 17.1 min, p < .06; tFC > 70%: 20.1 ± 15.2 vs 10.6 ± 7.1, p < .05). Boys were more active than girls, but only in the underprivileged group (tFC > 140: 51.8 ± 30.1 vs 32.8 ± 26.0 min, tFC > 160: 22.7 ± 16.6 vs 9.9 ± 8.2 min, p < .05; tFC > 50%: 61.4 ± 33.5 vs 37.4 ± 23.8 min, p < .05; tFC > 70%: 20.1 ± 15.2 vs 8.1 ± 6.3, p < .05). Cultural factors could be involved in these results. Key words: habitual physical activity, heart rate, heart rate meter, gender, energy expenditure
Durée de la récupération et puissance maximale anaérobie au cours de la journée
Authors: Falgairette Guy , Billaut François , Ramdani Sophiane
Published: June 2009

Effects of recovery duration (2-3 s, 15 s, 30 s, 1 min, and 2 min) and time of day (9 a.m., 2 p.m., and 6 p.m.) on sprint performance were studied in 9 subjects using a cycle ergometer. The peak power (Ppeak) and the total work performed (W) were determined from changes in instantaneous power, taking into account the inertia of the flywheel. A decrease in Ppeak and W was observed after 15 s and 2-3 s recovery (p < 0.001). A logarithmic relationship (y = 3.92 ln x + 81.5; r = 0.82; n = 9) was found between Ppeak (%Ppeak of the first sprint) and the duration of the recovery (half-time = 14.3 s; SD = 7.6). Data indicated that there was no significant effect of time of day on Ppeak and W, regardless of the duration of recovery. The recovery processes occurred in a very short time and did not seem to be affected by biological rhythms. Key words: performance, diurnal variation, fatigue, ergometry, inertia
Effect of Active and Passive Recovery on Blood Lactate and Performance During Simulated Competition in High Level Gymnasts
Authors: Jemni Monèm , Sands William A. , Friemel Françoise , Delamarche Paul
Published: June 2009

The purpose of this study was to investigate the effect of two recovery strategies between men's gymnastics events on blood lactate removal (BL) and performance as rated by expert "blind" judges. Twelve male gymnasts (21.8 ± 2.4 years) participated. The sessions were composed of routine performances in the six Olympic events, which were separated by 10 min of recovery. All gymnasts performed two recovery protocols between events on separate days: Rest protocol, 10 min rest in a sitting position; combined protocol, 5 min rest and 5 min self-selected active recovery. Three blood samples were taken at 2, 5, and 10 min following each event. Gymnasts produced moderate values of BL following each of the six events (2.2 to 11.6 mmolúL−1). There was moderate variability in BL values between events that could not be accounted for by the athlete's event performance. Gymnasts showed higher BL concentration (p > .05) and significantly (p < .05) higher scoring performances (as rated by a panel of certified judges) when they used a combined recovery between gymnastics events rather than a passive recovery (ΔBL = 40.51% vs. 28.76% of maximal BL, p < .05, and total score = 47.28 ± 6.82 vs. 38.39 ± 7.55, p < .05, respectively). Key words: oxidation, removal, heart rate
Sympathetic Responses to Valsalva's Manoeuvre Following Bed Rest
Authors: Shoemaker J. Kevin , Hogeman Cynthia S. , Sinoway Lawrence I.
Published: June 2009

The purpose of this study was to examine whether 14 days of head-down tilt bed rest (HDBR) alters autonomic regulation during Valsalva's manoeuvre (VM) and if this would predict blood pressure control during a 60° head-up tilt (HUT) test. To examine autonomic control of blood pressure, we measured the changes in systolic (ΔSBP) and diastolic (ΔDBP) blood pressure between baseline and the early straining (Phase IIE) period of VM (20 sec straining to 40 mmHg; N = 7) in conjunction with changes in muscle sympathetic nerve activity (MSNA; microneurography) burst frequency (B/min) and total activity (%Δ) from baseline over the 20-sec straining period. MSNA data were successfully recorded from 6 of the 7 individuals. The averaged responses from three repeated VMs performed in the supine position were compared between the pre- and post-HDBR tests. Compared with the pre-HDBR test, a greater reduction in SBP, DBP, and MAP was observed during Phase IIE following HDBR, p < 0.05. The increase in MSNA burst frequency during straining was augmented in the post- compared with the pre-HDBR test, p < 0.0001, as was the Phase IV blood pressure overshoot, p < 0.05. Although all subjects completed the 20-min pre-HDBR tilt test without evidence of hypotension or orthostatic intolerance, the post-HDBR test was stopped early in 5 of the 7 subjects due to systolic hypotension. The responses during the VM suggest that acute autonomic adjustments to rapid blood pressure changes are preserved after bed rest. Furthermore, MSNA and blood pressure responses during VM did not predict blood pressure control during orthostasis following HDBR. Key words: muscle sympathetic nerve activity, blood pressure, orthostatic tolerance, head-up tilt
Port de combinaison et depense energétique lors d'un enchaînement natation-cyclisme
Authors: Delextrat Anne , Bernard Thierry , Hausswirth Christophe , Vercruyssen Fabrice , Brisswalter Jeanick
Published: June 2009

The aim of this study was to investigate the effects of swimming with a wetsuit on energy expenditure during subsequent cycling. Nine well-trained triathletes underwent three submaximal trials. The first trial (SC) consisted of a 750-m swim realised at a competition pace, followed by a 10-min cycling exercise at a power output corresponding to the ventilatory threshold +5%. The two other trials were composed of the same cycling exercise, preceded either by a 750-m swim with a wetsuit (WSC) or by a cycling warm-up (Ctrl). The main results are that the WSC trial was characterised by significantly lower swimming cadence (−14%), heart rate (−11%), and lactate values (−47%) compared to the SC trial, p < 0.05. Moreover, cycling efficiency was significantly higher in the WSC trial compared to the SC trial (12.1% difference, p < 0.05). The lower relative intensity observed during swimming with a wetsuit suggest the relative importance of swimming condition on the total performance in a sprint triathlon. Key words: triathlon, energy cost, cycling efficiency, locomotion
Influence of Physical Training on Plasma Leptin in Obese Youths
Authors: Barbeau Paule , Gutin Bernard , Litaker Mark S. , Ramsey Leigh T. , Cannady William E. , Allison Jerry , Lemmon Christian R. , Owens Scott
Published: June 2009

Little is known about the effects of different intensities of physical training on plasma leptin. This study examined the effect of two intensities of physical training on leptin in obese teenagers, and explored correlates at baseline and in response to 8 months of physical training. The participants were 55 obese youths 12-16 years of age who completed both baseline and posttesting. The youths were randomized to engage in lifestyle education only (LSE), moderate-intensity physical training and LSE, or high-intensity physical training and LSE. Baseline leptin was positively associated with fat mass. Girls had higher leptin levels at lower levels of fasting insulin than boys. The 8-mo physical training doses prescribed to obese teenagers did not result in significant group differences in mean change in leptin, although there was large variability in individual response. The change in leptin was inversely associated with baseline leptin and change in cardiovascular fitness. Diet, physical activity level, visceral adiposity, and glucose concentrations were not associated with leptin, neither at baseline nor in response to physical training. At baseline, total fat mass rather than visceral adiposity was associated with higher leptin levels. Over the 8-mo intervention period, regardless of group membership, youths who had the lowest increase in cardiovascular fitness tended to have the highest increase in leptin. Key words: pediatrics, obesity, insulin, cardiovascular fitness
Glycogen Depletion of Human Skeletal Muscle Fibers in Response to High-Frequency Electrical Stimulation
Authors: Johnson Michel J. , Lortie Gilles , Simoneau Jean-Aimé , Boulay Marcel R.
Published: June 2009

The purpose of the present study was to evaluate the pattern of change in muscular glycogen content in response to high-frequency electrical stimulation (HFES). Muscle biopsies were taken from the vastus lateralis muscle of 7 healthy young men before, 15 min after, and 30 min after electrical stimulation delivered at a 50-Hz frequency (15 s on, 45 s off) at an intensity of 100 mA. The glycogen content of type I, IIA, and IIB muscle fibres was evaluated using microphotometry of periodic acid Schiff (PAS) stained fibres. After 15 min of electrical stimulation, the glycogen content in type I, IIA, and IIB muscle fibres significantly decreased from 113 ± 10 (mean ± SE) to 103 ± 10 (p ≤ 0.05), 129 ± 9 to 102 ± 12 (p ≤ 0.01), and 118 ± 8 to 90 ± 13 (p ≤ 0.01) arbitrary relative units, respectively. No further decrement in glycogen content was observed in all three fibre types following an additional 15 min of HFES. In addition, isometric force decreased by approximately 50%, from 125.9 ± 20.0 N to 64.2 ± 7.7 N (p ≤ 0.01), during the first 15 contractions. No further decrease in isometric force was observed following an additional 15 contractions of HFES. These results reveal that significant reductions in isometric force of knee extensor muscles and glycogen content of all human skeletal muscle fibre types in vastus lateralis muscle are observable after 15 min of neuromuscular high-frequency transcutaneous electrical stimulation. Key words: energy metabolism, isometric strength
Insulin Regulation of Glucose Transport in Skeletal Muscle: Influence of Caffeine, Adenosine, and Epinephrine
Authors: Thong Farah
Published: June 2009

not available
Acute and Chronic Effects of Leptin on Skeletal Muscle Fatty Acid Metabolism
Authors: Steinberg Gregory Robert
Published: June 2009

not available