bluuebunny/crossref_metadata_2025 huggingface dataset:
Proximate Analysis of Fish Tissue by Mid-Infrared Transmission Spectroscopy
Authors: Darwish G. S. , Voort F. R. van de , Smith J. P.
Published: June 2009

Mid-infrared spectroscopy was assessed as a means for rapidly determining the fat, protein, and moisture content of fish tissues. For fat and protein, a sample preparation protocol was developed for the conversion of fish tissue into a milk-like emulsion for analysis by a Multispec MK I infrared milk analyser. Fish (cod, tuna, and mackerel) were minced, dissolved, and emulsified in 0.2 M NaOH using a polytron and analysed for fat and protein using the conventional fat and protein wavelengths used for milk analysis. Instrument calibration for fat and protein was based on the Mojonnier and Kjeldahl procedures, respectively. Moisture was determined separately by extracting the water from the minced tissue using absolute methanol and measuring the absorbance of the resulting solution using a 5.56/6.02-μm filter pair. The instrument was calibrated using standardized water–methanol mixtures and the results compared with the standard vacuum oven method. Rapid analyses of fat and protein were possible giving individual results to within 1% of the standard chemical determinations. Moisture analysis, also worked well, being more accurate and rapid than the vacuum oven procedure. The limiting factor in its use for proximate analysis appears to be a combination of sample compositional variation and/or the general reproducibility of the standard methods. We conclude that the analysis of fish by mid-infrared transmission spectroscopy could serve as a means of rapidly carrying out the proximate analysis of fish and fish products for quality control purposes.
Mono- and Duoculture of juvenile Atlantic Salmon (Salmo salar) and Arctic Char (Salvelinus alpinus)
Authors: Holm Jens Chr
Published: June 2009

In a duoculture experiment with Atlantic salmon parr (Salmo salar) and two Arctic char (Salvelinus alpinus) strains, both species showed increased growth rates compared with monoculture. In duoculture, salmon dispersed more evenly than in monoculture, maintaining positions among the char. Less frequent occurrence of dorsal fin rot was observed in duoculture salmon, probably indicating decreased intraspecific aggression, compared with monoculture salmon. It is suggested that shading and increased dispersion allowed a decrease in intraspecific salmon aggression. Arctic char social hierarchy, indicated by variance of mean inter-renal cell nucleus area, was changed in the presence of salmon, favouring the largest individuals belonging to one of the strains. Different ecological adaptations and size differences can explain the difference in growth gain from duoculture between the char strains. Temperature is suggested as a behavioural regulator in salmon–char duoculture.
Exercise and Training in Women, Part II: Influence of Menstrual Cycle and Pregnancy on Exercise Responses
Authors: Shephard Roy J.
Published: June 2009

not available
The Acute Effects of Androstenedione Supplementation in Healthy Young Males
Authors: Ballantyne Craig S. , Phillips Stuart M. , Macdonald Jay R. , Tarnopolsky Mark A. , Macdougall J. Duncan
Published: June 2009

We examined the effects of androstenedione supplementation on the hormonal profile of 10 males and its interaction with resistance exercise. Baseline testosterone, luteinizing hormone, estradiol, and androstenedione concentrations were established by venous sampling at 3 hr intervals over 24 hr. Subjects ingested 200 mg of androstenedione daily for 2 days, with second and third day blood samples. Two weeks later, they ingested androstenedione or a placebo for 2 days, in a double-blind, cross-over design. On day 2, they performed heavy resistance exercise with blood sampled before, after, and 90 min post. The supplement elevated plasma androstenedione 2-3-fold and luteinizing hormone ∼70% but did not alter testosterone concentration. Exercise elevated testosterone, with no difference between conditions. Exercise in the supplemented condition significantly elevated plasma estradiol by ∼83% for 90 min. Androstenedione supplementation, thus, is unlikely to provide male athletes with any anabolic benefit and, with heavy resistance exercise, elevates estrogen. Key Words: testosterone, luteinizing hormone, estradiol, fluid shifts, resistance exercise
La fatigue des muscles ventilatoires a l'exercice maximal sur deux ergomètres differents
Authors: Toraa Moncef , Friemel Françoise
Published: June 2009

This study examines relationships between physical exercise and fatigue of ventilatory muscles according to training, intensity of exercise, and the ergometer. Twenty-two athletes were submitted to maximal triangular exercise on treadmill (TR) and bicycle (BE). Maximal inspiratory (PImax) and expiratory pressures and a spirometry were measured before and after exercise. In the "high level physical capacity" group (GR1) and "medium level physical capacity" group (GR2). PImax (128.4 + 36.8 cmH2O) and PEmax (175.7 ± 63.8 cmH2O) after exercise on TR decreased significantly (140.0 ± 32.6, p < .05; at rest: 196.8 + 59.8 cmH2O, p < .01). After exercise on BE. PImax and PEmax in GR1 and GR2 were significantly smaller than at rest (p < .001). In GR1, forced vital capacity (FVC) was significantly decreased after exercise on TR (5.22 ± 0.8 vs. 4.99 ± 0.61; p < .05). Key word: fatigue of ventilatory muscles, maximal exercise, training
Evidence That a Decrease in Liver Glycogen Content Stimulates FFA Mobilization During Exercise
Authors: Couturier Karine , Bélanger Patrice , Latour Martin G. , Lavoie Jean-Marc
Published: June 2009

This study evaluated a liver glycogen content decrease before exercise on the metabolic responses during exercise. Rats injected with glucagon (20 μg•kg−1) were compared to rats with a 50% food restriction (1/2-fast) and normally fed rats. All were studied at rest and during exercise (26 m/min, 0% grade). Resting liver glycogen concentrations were twice as high (P < .01) in normally fed rats, with no significant differences between 1/2-fast and glucagon-injected rats. During exercise, liver glycogen content was significantly reduced in normally fed rats. After exercise, plasma insulin levels were decreased (P < .01) in all groups, and β-hydroxybutyrate concentrations were similar in normally fed and glucagon-injected rats and significantly (P < .01) lower in 1/2-fast rats. Exercise caused a significant increase in FFA concentrations in all groups (P < .01). No significant differences in FFA concentrations were found between 1/2-fast and glucagon-injected groups (P > 0.05). Key words: glucagon injection, fasting, insulin, hepatic receptors
The Effects of Acute Passive Stretch on Muscle Protein Synthesis in Humans
Authors: Fowles J.R. , MacDougall J.D. , Tarnopolsky M.A. , Sale D.G. , Roy B.D. , Yarasheski K. E.
Published: June 2009

We examined the effect of an isolated bout of maximal tolerated passive stretch on fractional muscle protein synthetic rate in human soleus muscle. Eight healthy males performed two separate trials with the same leg; one session of passive stretch and one of intermittent active isometric contraction at a force equivalent to that which occurred during the passive stretch trial. This force was ∼40% of maximum voluntary contraction force and produced volitional fatigue in ∼27 min. Intermittent passive stretch, for the same duration, elicited a 6.1° increase in joint angle (P < .0005) with silent electromyography. Fractional protein synthetic rate from experimental and control soleus in each trial was assessed from biopsy samples over the period 10 - 22 hr postexercise by the incorporation rate of L - (1 - 13C] leucine into muscle. Protein synthesis was elevated in the soleus of the exercised leg following the active contraction trial by 49% (P < .05) but not following the passive stretch trial. Results indicate that a single bout of maximal passive stretch does not significantly elevate fractional muscle protein synthetic rate in humans and thus suggests that muscle stretch per se is not the stimulus for the muscle hypertrophy that occurs with resistance training. Key words: fractional muscle protein synthesis, isometric, soleus, electromyography, torque
Short-term Training: When Do Repeated Bouts Become Training? Introduction to the Symposium
Authors: Philips Stuart M.
Published: June 2009

not available
Physiological Responses to Cycling for 60 Minutes at Maximal Lactate Steady State
Authors: Lajoie Claude , Laurencelle Louis , Trudeau François
Published: June 2009

Changes in physiological variables during a 60-min continuous test at maximal lactate steady state (MLSS) were studied using highly conditioned cyclists (1 female and 9 males, aged 28.3 ± 8.1 years). To determine power at MLSS, we tested at 8-min increments and interpolated the power corresponding to a blood lactate value of 4 mmol/L. During the subsequent 60-min exercise at MLSS, we observed a sequential increase of physiological parameters, in contrast to stable blood lactate. Heart rate drifted upward from beginning to end of exercise. This became statistically significant after 30 min. From 10-60 min of exercise, a change of + 12.6 ± 3.2 bpm was noted. Significant drift was seen after 30 min for the respiratory exchange ratio, after 40 min for the rate of perceived exertion using the Borg scale, and after 50 min for % [Formula: see text] and minute ventilation. This slow component of [Formula: see text] may be the result of higher recruitment of type II fibers. Key words: Rate of perceived exertion, heart rate, oxygen consumption, blood lactate, cycling
Gender Differences in Substrate Metabolism During Endurance Exercise
Authors: Tarnopolsky Mark A.
Published: June 2009

Females show a lower respiratory exchange ratio (RER) than males during submaximal endurance exercise, which translates into a proportionately lower carbohydrate and higher fat oxidation. Data from rodents show that 17-β-estradiol may mediate these metabolic differences. 17-β-estradiol supplementation in humans is less convincing; however, two studies found a reduction in glucose rate of appearance during exercise. No difference is found between genders in muscle glycogen content; however, lipid content in muscle is higher in females. Evidence shows that short chain OH-acyl CoA-dehydrogenase (SCHAD) maximal enzyme activity is higher in females. The rate of leucine oxidation is lower in females at rest and during endurance exercise. This is not apparently related to gender differences in branched chain-2-oxo-dehydrogenase (BCOAD) activity in skeletal muscle, which may implicate hepatic control. Important muscle proteins to examine in future research are hormone sensitive lipase, the enzymes of β-oxidation, and fatty acid transporters. Key words: estradiol, progesterone, testosterone, sex differences, substrate metabolism, muscle enzymes
Nutraceuticals for Health and Performance: Introduction to the Symposium
Authors: Bettger William J.
Published: June 2009

not available
Bilateral and Unilateral Contractions: Possible Differences in Maximal Voluntary Force
Authors: Jakobi Jennifer M. , Chilibeck Philip D.
Published: June 2009

The issue of whether there is a difference in the amount of force produced from a simultaneous two-limb maximal contraction compared to the sum of individual one-limb contractions has received considerable debate in the literature. A bilateral deficit (BLD) is when the resultant force from bilateral homonymous limb contractions is less than the summed force of individual limb contractions. Determining whether differences exist between one- and two-limb movements may provide insight into complex neuromuscular control patterns. Many dynamic two-limb studies report a BLD, whereas isometric studies are more numerous and controversial. It is important to categorize the movements studied in order to establish consistency. This paper purports that the BLD is an unstable phenomenon, and its presence should be considered in the context of the movement studied. Most likely, this phenomenon is dependent upon some minor deviation in descending drive between the cortical level and peripheral motor neuron. Key words: bilateral deficit, strength, neuromuscular, EMG
The Effects of Strength Training on Sarcopenia
Authors: Porter Michelle M.
Published: June 2009

In the past decade strength training has been investigated extensively as a means of reversing the muscle mass loss that occurs with aging (sarcopenia). High intensity resistance training (HIRT) has led to increased protein synthesis, along with muscle hypertrophy measured at the whole body, whole muscle, and muscle fibre levels, in older adults. Typically, the strength increments associated with HIRT have been much larger than the hypertrophic response. However, most HIRT periods have been quite short. Less is known about the long term hypertrophic response to HIRT in older adults. In order to lessen the effects of sarcopenia, HIRT should continue over the long-term in older adults, to improve functional performance and health. Key words: aging, muscle physiology, hypertrophy, exercise, weight lifting
Reduced Oxygen Uptake During Steady State Exercise After 21-Day Mountain Climbing Expedition to 6,194 m
Authors: Macdonald Maureen J. , Green Howard J. , Naylor Heather L. , Otto Christian , Hughson Richard L.
Published: June 2009

We investigated the effect of a 21-day climbing expedition to 6,194 m on the oxygen uptake [Formula: see text] and leg blood flow (LBF) responses to submaximal exercise in five healthy, fit men during two-leg kicking exercise at 0-W and 50-W. Tests were completed 1 week before and 3 days after altitude acclimatization. The adaptation of [Formula: see text] at exercise onset was described by the time to 63% of the new steady state. Steady state [Formula: see text] during 50-W exercise was less post-climb (1290 ± 29 mL/min, mean ± SE) than pre-climb (1413 + 63 mL/min, P < .05). [Formula: see text] adapted more slowly at the onset of 50-W exercise post-climb. There were no differences in the steady state LBF during 50-W exercise, the increase above baseline, or the adaptation post-climb. Respiratory exchange ratio was greater at 50-W post-climb compared to pre-climb. Reduced steady state [Formula: see text] during exercise after exposure to high altitude is consistent with an increase in metabolic efficiency. Key words: work efficiency, leg blood flow, altitude, hypoxia, Doppler ultrasound
The Role of Hyperbaric Oxygen in Sports Medicine
Authors: Webster Dr Anthony L.
Published: June 2009

not available
Adaptation to Eccentric Exercise: Neutrophils and E-selectin During Early Recovery
Authors: Pizza Francis X. , Baylies Heather , Mitchell Joel B.
Published: June 2009

The purpose was to determine the responses of blood neutrophils and E-selectin concentrations during early recovery (< 24 hr)from 2 bouts of eccentric exercise. Subjects (N = 9) completed 2 bouts of eccentric arm exercise using their non-dominant arm (Bout 1 and Bout 2) and 1 non-exercise control condition. The exercise bouts were separated by 4 weeks, and the control condition preceded Bout 1. Neutrophil concentrations were significantly higher at 3, 6, and 9 hr post-exercise for Bout 1 relative to Bout 2 and control. No significant changes in blood E-selectin concentrations were observed. Isometric strength deficit was similar for Bout 1 and Bout 2 at 5 min and 3 hr post-exercise and was significantly greater for Bout 1 relative to Bout 2 at 6, 9, and 24 hr post-exercise. The adaptation to eccentric exercise is associated with a lower concentration of blood neutrophils during early recovery. The neutrophilia associated with novel eccentric arm exercise precedes secondary changes in isometric strength and is not associated with changes in the concentration of blood E- selection. Key Words: muscle inflammation, muscle damage, leukocyte adhesion
Meniscus and Synovial Membrane: An Electronmicroscopic Study on Rabbits
Authors: Hu S.Y. , Wang S. , Zuo R.T. , Wang K.L. , Qin L.
Published: June 2009

Seven healthy mature rabbits were used to study both the surface morphology of the meniscus using both transmission electronmicroscopy (TEM) and scanning electronmicroscopy (SEM) and articular cartilage of the femoral condyle using SEM. Results showed that the membrane covering the meniscus was structurally the extension of synovial membrane of the knee joint capsule. Additionally, the presence of canal-like openings over the membranous surface to the meniscus was noted, which were absent over the articular cartilage surface. Key words: transmission and scanning electronmicroscopy, meniscus, articular cartilage, rabbits
Contribution to the Study of Giucose Metabolism and Gluconeogenesis During Prolonged Exercise and in Response to Training
Authors: Burelle Yan
Published: June 2009

not available
Evolution du profil physiologique des gymnastes durant les 40 dernieres annees (revue de littérature)
Authors: Jemni Monèm , Friemel Françoise , Sands William , Mikesky Alan
Published: June 2009

Authors illustrate the evolution of the physiological profile of gymnasts over the past 40 years. Gymnasts are demonstrating increased anaerobic power. Maximal power output measured by the Wingate test in high level male gymnasts is currently between 12 and 14 W • kg−1. Female gymnasts show maximal power between 10 and 12 W • kg−1. In spite of an increase in the number of training hours, they have a low aerobic aptitude. It is still adequate and sufficient for their practice.Maximal heart rate values measured during gymnastic exercises have mirrored technical and acrobatic demands of increasing difficulty. Currently, exercise heart rates exceed 190 beat • min−1 as compared to 135 to 151 beat • min−1 in the seventies. Measurement of higher blood lactate values suggests that anaerobic glycolysis has increased in importance. Glycolytic contributions differ between apparatuses. Data from energy cost studies demonstrate that gymnastics energy demands are greater now than in the seventies. Key words: maximal anaerobic power, maximal oxygen uptake, heart rate, blood lactate, energetic cost
Hormone Responses to Resistance vs. Endurance Exercise in Premenopausal Females
Authors: Consitt Leslie A. , Copeland Jennifer L. , Tremblay Mark S.
Published: June 2009

Sixteen, cross-trained, premenopausal women participated in an endurance, resistance, and control session to compare hormone responses. The resistance session included 3 sets of eight exercises at 10 RM intensity. The endurance session consisted of a 40-min cycling protocol at 75% of maximal heart rate. During the control session, subjects rested for 35 min. Serum DHEA, estradiol, testosterone, growth hormone, IGF-I, cortisol, and plasma lactate concentrations were measured pre-exercise, post-exercise, and 30 min into recovery. Differences in intensity variables existed between the three sessions. Endurance exercise elicited increases in growth hormone, estradiol, and testosterone compared to the control session, and growth hormone increased after the resistance compared to the control session. The exercise protocols used in this study indicate that an acute bout of exercise can stimulate the endocrine system in premenopausal females. In addition, these results indicate that differences exist between these two exercise protocols when compared to a control session. Key words: dehydroepiandrosterone, testosterone, estradiol, growth hormone, IGF-I
What Is Fatigue?
Authors: Macintosh Brian R. , Rassier Dilson E.
Published: June 2009

Fatigue and potentiation are two forms of force modulation. A general definition of fatigue is "a circumstance where less than the anticipated contractile response is obtained." Fatigue is associated with depressed Ca2+ release and possibly decreased Ca2+ sensitivity. Potentiation results from increased Ca2+ sensitivity due to regulatory light chain phosphorylation. Muscle fatigue and potentiation can coexist, making it difficult to quantify these processes. With repetitive 10 Hz stimulation, the developed tension first increases, then decreases. Is fatigue present when developed tension first begins to decrease or when it falls below the developed tension of the first response? Intermittent incompletely fused tetanic contractions for which peak developed tension first decreases, then increases, is another unusual example of fatigue. A third example is when twitch contractions following a tetanic contraction decrease to a level below the pretetanic twitch amplitude, indicating that fatigue may have been coexistent with posttetanic potentiation. These observations illustrate the complexity of detecting fatigue, based on the simple, but commonly accepted definition presented above. Care must be taken in interpreting "before vs. after" contractile responses. Even when the contraction amplitude is greater than the initial response, there is no guarantee that mechanisms associated with fatigue are not present. Key words: calcium sensitivity, staircase, posttetanic potentiation, myosin light chains, skeletal muscle
Muscle Fatigue: The Role of Intracellular Calcium Stores
Authors: Allen David G. , Kabbara Akram A. , Westerblad Håkau
Published: June 2009

Force declines when muscles are used repeatedly and intensively and a variety of intracellular mechanisms appear to contribute to this muscle fatigue. Intracellular calcium release declines during fatigue and has been shown to contribute to the reduction in force. Three new approaches have helped to define the role of calcium stores to this decline in calcium release. Skinned fibre experiments show that when intracellular phosphate is increased the amount of Ca2+ released from the sarcoplasmic reticulum (SR) declines. Intact fibre experiments show that the size of the calcium store declines during fatigue and recovers on rest. Intact muscles which lack the enzyme creatine kinase, do not exhibit the usual rise of phosphate during fatigue and, under these conditions, the decline of Ca2+ release is absent or delayed. These results can be explained by the "calcium phosphate precipitation" hypothesis. This proposes that if phosphate in the myoplasm rises, it enters the SR and binds to Ca2+ as Ca2+ phosphate. The resultant reduction in free Ca2+ within the SR contributes to the reduced Ca2+ release during fatigue. Key words: sarcoplasmic reticulum, myoplasmic phosphate, calcium phosphate precipitation, creatine kinase, glycogen
A Quantitative Analysis of the Subcellular Distribution of Human Skeletal Muscle Glycogen
Authors: Marchand Ingrid
Published: June 2009

not available
Critical Velocity and Time Spent at a High Level of for Short Intermittent Runs at Supramaximal Velocities
Authors: Dupont Grégory , Blondel Nicolas , Lensel Ghislaine , Berthoin Serge
Published: June 2009

This study was designed to determine the intermittent critical velocity, the time spent at maximal oxygen uptake [Formula: see text] and the time spent above 90% of [Formula: see text] for short intermittent runs of 15 s at supramaximal velocities, alternating with 15 s of passive recovery. Nine male subjects performed 5 field-tests to exhaustion (tlim): 4 intermittent runs at 110%, 120%, 130% and 140% of maximal aerobic speed (MAS) and 1 continuous run at 100% of MAS. Results have shown the mean intermittent critical velocity (4.82 ± 0.41 m.s−1) was not significantly different from MAS (4.63 ± 0.37 m.s−1). Intermittent runs at 110% and 120% of MAS and the continuous run at 100% of MAS lead all subjects to reach [Formula: see text]. However, intermittent runs at 120% of MAS (202 ± 66 s) allowed subjects to spend a significantly longer time at [Formula: see text](p < .05) than intermittent runs at 110% (116 ± 42 s), 130% (50 ± 47 s), 140% (48 ± 59 s) of MAS and continuous run at 100% of MAS (120 ± 42 s). The time spent between 90 and 100% of [Formula: see text] was significantly longer (p < .05) for intermittent runs at 110% (383 ± 180 s) and for 120% (323 ± 272 s) of MAS than for intermittent runs at 130% (135 ± 133 s), 140% of MAS (77 ± 96 s) and for continuous run at 100% of MAS (217 ± 114 s). Consequently, this kind of intermittent exercise with intensities from intermittent critical velocity to 120% of MAS could be introduced in a training program when the purpose is to increase [Formula: see text]. Key words: intermittent exercise, maximal oxygen consumption, performance, training
Exercise- and Insulin-Stimulated Muscle Glucose Transport: Distinct Mechanisms of Regulation
Authors: Khayat Zayna A. , Patel Nish , Klip Amira
Published: June 2009

In mammals, skeletal muscle is the primary target for the stimulation of glucose transport by a variety of activators. These include the hormone insulin and stimuli which increase energy demand such as exercise, hypoxia, and challenges to the oxidative chain. While it is known that both stimuli rapidly elevate glucose uptake into muscle by signalling the translocation of glucose transporters from intracellular stores to the plasma membrane, there are numerous contrasts between energy stressors and insulin in their mechanisms of glucose transport activation. Exercise and insulin recruit distinct intracellular pools of glucose transporters in skeletal muscle and the maximal effects of contraction and insulin are additive. Activation of phosphatidylinositol 3-kinase (PI3-K) is utilized by insulin to induce glucose transporter translocation, but does not participate in the responses to exercise or hypoxia. These findings suggest that energy stressors utilize different mechanisms from insulin to increase glucose influx; however, how these factors elicit their response is not clear. This review will summarize our current knowledge of these alternative pathways of glucose transport regulation. Emphasis is placed on the use of the mitochondrial uncoupler dinitrophenol to investigate mediators of this alternative signalling pathway in L6 muscle cells, a line used to characterize physiological responses in muscle such as glucose transport. Key words: contraction, GLUT4, cPKC, Ca2+, AMPK
Effects of Heavy Resistance/Power Training on Maximal Strength, Muscle Morphology, and Hormonal Response Patterns in 60-75-Year-Old Men and Women
Authors: Häkkinen Keijo , Kraemer William J. , Pakarinen Arto , Tripleltt-Mcbride Travis , Mcbride Jeffrey M. , Häkkinen Arja , Alen Markku , Mcguigan Michael R. , Bronks Roger , Newton Robert U.
Published: June 2009

Eleven women (TRW; 64 ± 4 yrs) and ten men (TRM; 65 ± 5 yrs) participated in the strength/power training twice a week for 24 weeks. Basal concentrations of serum total and free testosterone, growth hormone (GH), dehydroepiandrosterone sulfate (DHEAS), cortisol and sex hormone binding globulin (SHBG) as well as acute responses of serum total and free testosterone, growth hormone (GH) were measured. Maximal 1RM strength in the squat, chair rise time and muscle fibre distribution and areas of type I and IIa and IIb of the vastus lateralis were also examined. 1RM squat increased in TRW by 26 (SDIO) % (p < .001), and in TRM by 35(7) % (p < .001) and chair rise time improved in both groups (p < .001). Fibre areas increased in type I, (p < .01), IIa (p < .01) and IIb (p < .01) in TRM and type I (p < .05) and IIa (p < .05) in TRW. The proportion of type IIa increased from 31% to 43% (p < .05) in TRW and that of type IIb decreased from 27% to 17% (p < .05) in TRW and from 25% to 17% (p < .05) in TRM. Individual concentrations of testosterone/cortisol ratios correlated (r = 0.63; p < .05) with the individual increases in 1RM strength in TRW. The exercise sessions resulted in acute increases in serum GH in both groups (p < .05) with a further increase (p < .01) up to 10 minutes post-loading in TRM at post-training. Key words: aging, strength training, power training, muscle hypertrophy, serum hormones
Force-Velocity Relationship on a Cycle Ergometer and Knee-Extensor Strength Indices
Authors: Driss Tarak , Vandewalle Henry , Chevalier Jean-Michel Le , Monod Hugues
Published: June 2009

Maximal anaerobic power (Pmax) is often measured on a friction loaded cycle ergometer by means of an all-out exercise against a single braking force or from the force-velocity relationship. The relationship between braking force (F) and peak velocity (V) in cycling is linear: V = V0(1 − F/F0) where V0 and F0 correspond to the intercepts with the velocity axis and force axis, respectively. The aim of the present paper was to test the hypothesis that parameter F0, expresses strength ability. The first study (12 male volleyball players) showed significant correlations between F0 and maximal isometric voluntary force (MVF) or maximal isometric rate of force development (MRFD) during isometric knee extension with data expressed either in absolute units (0.66 < r < 0.81, P < 0.01) or related to quadriceps muscle mass kgQ or kgQ2/3 (0.58 < r < 0.82, 0.05 < P < 0.001). In the second study (24 male athletes), F0 was significantly correlated with the peak torques in isokinetic Biodex knee extension at four angular velocities (0, 1.57, 3.14 and 4.19 rad • s−1) with the values expressed in absolute units (0.49 < r < 0.83, 0.05 < P < 0.001). When the results were related to kgQ or kgQ2/3 the correlation coefficients increased with velocity (0.22 < r < 0.69) and were significant (0.05 < P <  0.001) except at 0 rad • s−1. Nevertheless, the interest of the determination of F0 in addition to Pmax is questionable because similar coefficients of correlation were obtained between Pmax and strength performances. Key words: force, rate of force development, isometric exercise, isokinetic testing, maximal anaerobic power
The Adaptive Potential of Skeletal Muscle Fibers
Authors: Pette Dirk
Published: June 2009

Mammalian skeletal muscle fibers display a great adaptive potential. This potential results from the ability of muscle fibers to adjust their molecular, functional, and metabolic properties in response to altered functional demands, such as changes in neuromuscular activity or mechanical loading. Adaptive changes in the expression of myofibrillar and other protein isoforms result in fiber type transitions. These transitions occur in a sequential order and encompass a spectrum of pure and hybrid fibers. Depending on the quality, intensity, and duration of the alterations in functional demand, muscle fibers may undergo functional transitions in the direction of slow or fast, as well as metabolic transitions in the direction of aerobic-oxidative or glycotytic. The maximum range of possible transitions in either direction depends on the fiber phenotype and is determined by its initial location in the fiber spectrum. Key words: Ca-sequestering proteins, energy metabolism, fiber type transition, myofibrillar protein isofonns, myosin, neuromuscular activity
Variability in Estimating Eccentric Contraction-Induced Muscle Damage and Inflammation in Humans
Authors: Beaton Louise J. , Tarnopolsky Mark A. , Phillips Stuart M.
Published: June 2009

We studied five young healthy volunteers who performed a "damage protocol" consisting of 240 (24 sets x 10 repetitions/set) maximal isokinetic eccentric muscle contractions (30°/s) on each leg one week apart. Biopsies were taken from the vastus lateralis on two occasions. Two biopsies were taken from within the same muscle 24 h following the damage protocol. On a second occasion a single biopsy was taken from the contralateral leg at 24 h following the same damage protocol. Biopsies at all three sites showed Z-band disruption, much greater (i.e., ∼14-fold) than is typically observed in resting biopsies, with no significant differences (ANOVA) according to site location (within legs or between legs). The within-leg coefficient of variation (CV) was, however, 41 ± 30%, and the between-leg CVs were 57 ± 36% and 68 ± 36%. Macrophage cells were also detected within the muscle, and cell numbers were not statistically different between biopsy sites. However, the within-biopsy CV = 52 ± 19% and the between-biopsy CVs of 34 ± 24% and 48 ± 27%. We conclude that eccentric contraction-induced Z-band streaming and inflammatory cell response, as detected in muscle biopsy samples from humans, is highly variable with a CV of 40-70%. Key words: muscle damage; eccentric exercise; biopsy; coefficient of variation
Development and Validation of a One-Mile Treadmill Walk Test to Predict Peak Oxygen Uptake in Healthy Adults Ages 40 to 79 Years
Authors: Pober David M. , Freedson Patty S. , Kline Gregory M. , Mcinnis Kyle J. , Rippe James M.
Published: June 2009

The purpose of this investigation was to determine whether the Rockport one-mile walk test equation to predict maximal oxygen uptake was valid for application to treadmill walking. When the Rockport model was found to be inappropriate, a new regression model was developed for predicting peak oxygen uptake [Formula: see text] from a one-mile treadmill walk. 304 healthy volunteers ages 40 to 79 years (mean age = 57.6 years, 154 men and 150 women) completed a [Formula: see text] test and a one-mile treadmill walk. Stepwise regression was used to build a model for the relationship between [Formula: see text]and a variety of predictor variables in a sub-sample development group (n = 154). This new model was then applied to a sub-sample validation group (n = 150). The new equation produced a correlation of 0.87, SEE = 4.7 ml • kg−1 • min−1 with a mean residual of 0.96 ml • kg−1 • min−1. The equation for predicting [Formula: see text] developed in this investigation provides a means of assessing [Formula: see text] that is easy to administer, allows for careful supervision of subjects, and can be completed at a low financial and temporal cost. Key words:[Formula: see text]estimation, sub-maximal exercise testing, fitness, aerobic power, Treadwalk test
Effect of Paddling Cadence on Time to Exhaustion and Kinetics at the Intensity Associated With in Elite White-Water Kayakers
Authors: Leveque Jean Michel , Brisswalter Jeanick , Bernard Olivier , Goubault Claude
Published: June 2009

The influence of paddling cadence on the time to exhaustion (t.lim) and [Formula: see text] kinetics at the intensity associated with [Formula: see text] [Formula: see text] was examined in seven highly-trained white water kayakers. All subjects were engaged in national or international competitions. Subjects took part in three constant-load tests at [Formula: see text], each test performed at a different paddling cadence (50, 60 or 70 cycles ∙ min−1). The [Formula: see text] kinetics recorded during these constant-load tests at [Formula: see text] were fitted with a mono-exponential equation. A significant increase in t.lim (P <.05) was observed as the paddling cadence increased from 50 to 70 cycles·min−1. No effect was found either on values of [Formula: see text] post-exercise blood lactate concentration, or on the time at which [Formula: see text] was attained [Formula: see text]. Our results suggest that experienced kayakers may choose a high paddling cadence during physiological assessments at [Formula: see text] Further experiments are needed in order to identify the physiological significance of t.lim at [Formula: see text] Key words: performance, exercise test, pulmonary gas exchange, locomotory pattern, kayaking
Role of Leucine in Protein Metabolism During Exercise and Recovery
Authors: Layman Donald K.
Published: June 2009

Exercise produces changes in protein and amino acid metabolism. These changes include degradation of the branched-chain amino acids, production of alanine and glutamine, and changes in protein turnover. One of the amino acid most affected by exercise is the branched-chain amino acid leucine. Recently, there has been an increased understanding of the role of leucine in metabolic regulations and remarkable new findings about the role of leucine in intracellular signaling. Leucine appears to exert a synergistic role with insulin as a regulatory factor in the insulin/phosphatidylinositol-3 kinase (PI3-K) signal cascade. Insulin serves to activate the signal pathway, while leucine is essential to enhance or amplify the signal for protein synthesis at the level of peptide initiation. Studies feeding amino acids or leucine soon after exercise suggest that post-exercise consumption of amino acids stimulates recovery of muscle protein synthesis via translation regulations. This review focuses on the unique roles of leucine in amino acid metabolism in skeletal muscle during and after exercise. Key words: branched-chain amino acids, insulin, protein synthesis, skeletal muscle
Canadian Population Trends in Leisure-Time Physical Activity Levels, 1981-1998
Authors: Bruce Marny J. , Katzmarzyk Peter T.
Published: June 2009

Age, sex, geographic and temporal trends in leisure-time physical activity levels were examined using data from five national surveys conducted between 1981 and 1998. Physical activity energy expenditure (AEE) was higher among men compared to women, and in younger versus older adults. AEE increased from Eastern to Western Canada, with a significant temporal trend of increasing AEE. The prevalence of physical inactivity (expending < 12.6 kJ • kg−1• day−1) has decreased; however, it remains high (women: 77%; men: 74%). The high prevalence of physical inactivity emphasizes the importance of population-level physical activity surveillance and interventions. Key words: exercise, lifestyle, Canada Fitness Survey
Effect of Force Level and Training Status on Contractile Properties Following Fatigue
Authors: Garland S. Jayne , Walton David , Ivanova Tanya D.
Published: June 2009

This study examined the effects of fatigue on the contractile properties of the twitch contraction evoked by the H-reflex and the maximal M-wave. Untrained subjects demonstrated more pronounced slowing of half relaxation time (HRT) in the H-reflex twitch than in the M-wave twitch and also more slowing of HRT in high force vs. low force contractions. Endurance-trained subjects, however, demonstrated a shortening of the H-reflex twitch. The twitch contractile properties following fatigue are dependent on force level and training status. Key words: human, muscle fatigue, endurance, submaximal contractions
Oral Andro-Related Prohormone Supplementation: Do the Potential Risks Outweigh the Benefits?
Authors: Broeder Craig E.
Published: June 2009

Androstenedione, 4-androstenediol, 5-androstenediol, 19-norandrostenediol and 19-norandrostenedione are commonly referred to as "Andro" prohormones. Over the last few years, supplementation using these prohormones has been aggressively marketed to the general public. Supplement manufacturers often claim that Andro use improves serum testosterone concentrations, increases muscular strength and muscle mass, helps to reduce body fatness, enhances mood, and improves sexual performance. However, to date, most studies contradict these claims. In contrast, several studies using oral Andro related prohormones show that Andro use can abnormally elevate estrogen related hormones as well as alterations in hormonal markers (i.e., abnormal elevations in serum estrogen) thought to increase a person's risk for developing prostate or pancreatic cancers. In addition, most studies also indicate that significant declines in high-density lipoproteins occur leading to an increased cardiovascular disease risk. Thus, to date, the current research base suggests that Andro prohormone use does not support manufacturer claims. But it does suggest there should be strong concerns regarding long-term oral Andro prohormone use, especially regarding its effects on blood lipids and estrogen hormone profiles. Key words: resistance exercise, androstenedione, androstenediol, anti-aging
Study of the Sensitivity of Skeletal Muscle to Mechanical Stimulation, as Assessed by Mechanically Responsive Biochemical Events
Authors: Martineau Louis
Published: June 2009

not available
Training for Muscle Power in Older Adults: Effects on Functional Abilities
Authors: Hruda Kim V. , Hicks Audrey L. , Mccartney Neil
Published: June 2009

The purpose of this study was to determine the influence of simple, progressive lower body exercise training, focusing on strength and power, on functional abilities in frail older adults. Twenty-five residents of a long-term care facility (75-94 yrs) participated in this randomized controlled trial of 10 wks duration. The exercise group (Ex, n = 18) underwent simple, progressive lower body resistance exercises, specifically aimed at improving muscle power, 3 times/wk; the control subjects (Con, n = 7) maintained their usual daily activities. Knee extensor strength and power were measured on an isokinetic dynamometer (180°/s), and functional performance was assessed from a 6 m walk timed test, a 30 s chair stand, and an 8 ft up-and-go timed test, before and after the 10 wk intervention period. Significant increases were found in the Ex group for eccentric (44%) and concentric (60%) average power (p < 0.05), and improvements were seen on each functional test: the 8-foot up-and-go, chair stand, and walk time improved by 31%, 66%, and 33%, respectively (p < 0.05). No significant change occurred in the Con group. In conclusion, simple progressive exercise training, even in the 10th decade, increases muscle power and is associated with an improved performance of functional activities using the trained muscles. Key words: frail elderly, leg strength, functional performance
Anaerobic Threshold: The Concept and Methods of Measurement
Authors: Svedahl Krista , MacIntosh Brian R.
Published: June 2009

The anaerobic threshold (AnT) is defined as the highest sustained intensity of exercise for which measurement of oxygen uptake can account for the entire energy requirement. At the AnT, the rate at which lactate appears in the blood will be equal to the rate of its disappearance. Although inadequate oxygen delivery may facilitate lactic acid production, there is no evidence that lactic acid production above the AnT results from inadequate oxygen delivery. There are many reasons for trying to quantify this intensity of exercise, including assessment of cardiovascular or pulmonary health, evaluation of training programs, and categorization of the intensity of exercise as mild, moderate, or intense. Several tests have been developed to determine the intensity of exercise associated with AnT: maximal lactate steady state, lactate minimum test, lactate threshold, OBLA, individual anaerobic threshold, and ventilatory threshold. Each approach permits an estimate of the intensity of exercise associated with AnT, but also has consistent and predictable error depending on protocol and the criteria used to identify the appropriate intensity of exercise. These tests are valuable, but when used to predict AnT, the term that describes the approach taken should be used to refer to the intensity that has been identified, rather than to refer to this intensity as the AnT. Key words: maximal lactate steady state, lactate threshold, ventilatory threshold, OBLA, individual anaerobic threshold
Regular Moderate Exercise Training Prevents Decrease of CD4+ T-Lymphocytes Induced by a Single Bout of Strenuous Exercise in Mice
Authors: Fu Sai Chuen , Qin Lin , Leung Chi Kam , Chan Barbara Pui , Chan Kai Ming
Published: June 2009

The biphasic effects of exercise training on the immune system have been studied extensively and represented by the well-known J-shaped curve with respect to training intensity. However, the relationship and interactions between "beneficial" exercise training and "harmful" strenuous exercise have not been researched. This study was designed to determine whether regular moderate exercise training could affect the changes of percentage of T-lymphocytes induced by a single bout of strenuous exercise. A protocol to run uphill on a 10° tilted treadmill for 4 weeks was employed as moderate exercise training in mice, while a sedentary control group of mice was exposed to the same handling stress without training. The trained and untrained mice were then exposed to a single bout of strenuous exercise until exhaustion. Total leukocytes were collected from spleen and peripheral blood at 0 hr, 3 hrs, and 24 hrs postexhaustion, as well as from the control groups. Flow cytometric analyses were conducted to determine the percentages of selected leukocyte populations. It was demonstrated that moderate exercise training prevented the decrease of CD4+ but stimulated the increase of CD25+CD8+ T-lymphocytes induced by a single bout of strenuous exercise, indicating an adaptive response that can affect changes of leukocyte subpopuplations. Key words: CD8, flow cytometry, exhaustion, splenic T-cell
Responses to Different Intermittent Runs at Velocity Associated With
Authors: Millet Gregoire P. , Candau Robin , Fattori Philippe , Bignet Frank , Varray Alain
Published: June 2009

The purposes of this study were (1) to determine the time sustained above 90% of [Formula: see text] in different intermittent running sessions having the same overall time run at the velocity ([Formula: see text]) associated with [Formula: see text] and (2) to test whether the use of a fixed-fraction (50%) of the time to exhaustion at [Formula: see text] (Tlim) leads to longer time spent at a high percentage of [Formula: see text]. Subjects were 8 triathletes who, after determination of their track [Formula: see text] and Tlim, performed three intermittent running sessions alternating the velocity between 100% and 50% of [Formula: see text], termed 30s ∼ 30s, 60s ∼ 30s, and 1/2Tlim ∼ 1/2Tlim, where the overall time at [Formula: see text] was similar (= 3 × Tlim). [Formula: see text] achieved in the incremental test was 71.1 ± 3.9 mlùmin−1•kg−1and Tlimwas 236 ± 49 s. [Formula: see text] and peak heart rate were lower in 30s ∼ 30s than in the other intermittent runs. The time spent above 90% of [Formula: see text] was significantly (p < 0.001) longer either in 60s ∼ 30s (531 ± 187 s) or in 1/2Tlim ∼ 1/2Tlim(487 ± 176 s) than in 30s ∼ 30s (149 ± 33 s). Tlimwas negatively correlated with the time (in % of Tlim) spent above 90% of [Formula: see text] in 30s ∼ 30s (r = -0.75, p < 0.05). Tlimwas also correlated with the difference of time spent over 90% of [Formula: see text] between 60s ∼ 30s and 30s ∼ 30s (r = 0.77, p < 0.05), or between 1/2Tlim ∼ 1/2Tlimand 30s ∼ 30s (r = 0.97, p < 0.001). The results confirm that [Formula: see text] and Tlimare useful for setting interval-training sessions. However, the use of an individualized fixed-fraction of Tlimdid not lead to longer time spent at a high percentage of [Formula: see text] compared to when using a fixed work-interval duration. Key words: interval-training, maximal oxygen consumption, performance, time to exhaustion
Influence of Age and Moderate-Intensity Exercise Training on Heart Rate Variability in Young and Mature Adults
Authors: Leicht Anthony S. , Allen Graham D. , Hoey Andrew J.
Published: June 2009

The purpose of this study was to examine the influence of age and moderate-intensity exercise training on heart rate variability (HRV), and to elucidate further the mechanism of training-induced bradycardia and cardioprotection. Electrocardiograms were recorded from 12 young (18-24 yrs) and 12 mature (29-43 yrs) individuals during supine rest and submaximal moderate exercise. Recordings were obtained prior to, midway, and following 16 weeks of aerobic exercise training designed to improve cardiorespiratory fitness and health. Training resulted in augmented estimated [Formula: see text] and bradycardia during rest and submaximal exercise. Total and low frequency components of HRV during exercise were significantly increased for the mature subjects following training whereas other measures of HRV were not significantly changed for either group. It was concluded that training of moderate intensity was insufficient to induce changes in the autonomic control of heart rate for young to mature subjects. The lack of significant HRV changes may suggest the existence of a vagal critical point, below which training-induced increases in vagal modulation may be forthcoming, and above which changes in vagal modulation may be negligible. Training-induced bradycardia and the cardioprotective effect of regular aerobic exercise may result from factors other than an increased vagal modulation. Key words: physical activity, ageing, autonomic nervous system, bradycardia, spectral analysis