bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Pregnancy on Maternal Work Tolerance
Authors: Wolfe Larry A. , Charlesworth Sarah A. , Glenn Nicole M. , Heenan Aaron P. , Davies Gregory A.L.
Published: June 2009

This review summarizes current information on the tolerance of healthy pregnant women and their fetuses to acute strenuous exertion. Maximal aerobic power, expressed in L•min−1, is not significantly affected in women who maintain an active lifestyle, whereas values expressed in mlùkg−1ùmin−1 decline with advancing gestational age in relation to maternal/fetal weight gain. Efficiency during standard exercise testing and the ventilatory anaerobic threshold (Tvent) also appear to be unaffected by pregnancy, but the ability to utilize carbohydrate and exercise anaerobically during brief strenuous exercise may be reduced. Fetal responses to short strenuous exercise are usually moderate and revert to baseline values within approximately 30 min postexercise. Future studies should examine alveolar gas exchange kinetics at the start of exercise and during recovery from both moderate and strenuous exertion. Existing studies of the responses of pregnant women to prolonged exercise have focused primarily on substrate utilization and glucose homeostasis. Other maternal responses to prolonged exercise that should be examined include acid-base regulation, temperature regulation, fluid and electrolyte balance, and perception of effort. Fetal reactions should also be examined in relation to maternal responses. Until evidence-based, occupation-specific guidelines become available, it is recommended that pregnant women use the Joint SOGC/CSEP Clinical Practice Guideline: Exercise in Pregnancy and the Postpartum Period, published by the Society of Obstetricians and Gynaecologists of Canada and the Canadian Society for Exercise Physiology (2003). Key words: human gestation, maximal exercise, prolonged exercise, fetal well-being
Effects of Different Types of Exercise on Body Composition and Fat Distribution in HIV-Infected Patients: A Brief Review
Authors: Malita Florin M. , Karelis Antony D. , Toma Emil , Rabasa-Lhoret Remi
Published: June 2009

HIV infection and its treatment is associated with unfavourable metabolic and morphological abnormalities. These metabolic abnormalities, particularly alterations in body composition and fat distribution, may increase the risk for cardiovascular and metabolic complications, as well as reduce functional independence and lower self-esteem. Thus there is an urgent need to develop interventions intended to manage secondary side effects of HIV or antiretroviral therapy-related complications. In poly-treated patients, nonpharmacological interventions are a logical first step. Exercise training in particular may help alleviate some of the metabolic adverse effects associated with antiretroviral therapy by favourably altering body composition and patterns of body fat distribution. Studies have shown that exercise training, particularly aerobic training, can help reduce total body and visceral fat, as well as normalizing lipid profiles in HIV-infected patients. The results for resistance training, however, are less conclusive. Knowledge of the use of resistance and aerobic training and its attendant effects on insulin resistance and adipocytokines may represent an effective nonpharmacologic means for treating metabolic complications of HIV-infected persons who are receiving appropriate antiretroviral therapy. In this brief review we examine the effects of aerobic and resistance training on body composition, body fat distribution, and selected metabolic outcomes. Key words: lipodystrophy, highly active anti-retroviral therapy, aerobic training, resistance training
Low Levels of Recall Among Adult Canadians of the CSEP/Health Canada Physical Activity Guidelines
Authors: Bauman Adrian , Craig Cora Lynn , Cameron Christine
Published: June 2009

In 1998, Canadian guidelines were released to encourage sedentary adults to become more active. Representative surveys of over 4,400 Canadian adults found that unprompted recall of these guidelines was low (7.4% in 1999 and 5.2% in 2002), but was higher among educated, affluent, middle-aged, and the physically active. Achieving a high level of activity was associated with demographic variables and other information sources, but not with guideline recall. Guideline promotion has not reached those most in need. Key words: intervention, evaluation, awareness
Increase of Hemoglobin Concentration After Maximal Apneas in Divers, Skiers, and Untrained Humans
Authors: Richardson Matt , Bruijn Robert de , Holmberg H.-C. , Björklund Glenn , Haughey Helena , Schagatay Erika
Published: June 2009

Human splenic contraction occurs both during apnea and maximal exercise, increasing the circulating erythrocyte volume. We investigated the hematological responses to 3 maximal apneas performed by elite apneic divers, elite cross-country skiers, and untrained subjects. Post-apnea hemoglobin concentration had increased in all groups, but especially in divers. The increases disappeared within 10 min of recovery. Apneic duration across apneas also increased the most in divers. Responses in divers could be more pronounced as a result of apnea training. Key words: breath hold, serial apneas, spleen contraction, cross-country skiing
Aging, Resistance Training, and Motor Unit Discharge Behavior
Authors: Kamen Gary
Published: June 2009

Researchers have alluded to the existence of "neural factors" in the expression and development of muscular strength. Candidate neural factors including motor unit recruitment, rate coding, doublet firing, and motor unit synchronization are discussed in this review. Aging is generally accompanied by lower motor unit discharge rates. However, both young and older adults exhibit rapid changes in muscular strength with repeated strength testing. These strength changes occur with concomitant albeit transient increases in motor unit discharge rate. These and other neural factors may contribute to the initial increases in muscular strength observed during the early phases of resistance exercise training. Key words: firing rate, muscle, exercise
Motoneurones "Learn" and "Forget" Physical Activity
Authors: Gardiner Phillip , Beaumont Eric , Cormery Bruno
Published: June 2009

In spite of our knowledge of activity related adaptations in supraspinal neurones and skeletal muscles, very little is known concerning adaptations in α-motoneurones to alterations in chronic activity levels. Recent evidence shows that the biophysical properties of α-motoneurones are plastic and adapt to both increases and decreases in chronic activation. The nature of the adaptations-in resting membrane potential, spike threshold, afterhyperpolarization amplitude, and rate of depolarization during spike generation-point to involvement of density, type, location, and/or metabolic modulation of ion conductance channels in the motoneuronal membrane. These changes will have significant effects on how motoneurones respond when activated during the generation of movements, and on the effort required to sustain activation during prolonged exercise. Since the adaptations most likely involve structural changes in the motoneurones and changes in protein synthesis, and change the output response of the cells to input, they are considered to be learning responses. Future research directions for examining this issue are outlined. Key words: α-motoneurones, exercise, training, spinal cord, learning, disuse, spinal cord transection
Does Prior 1500-m Swimming Affect Cycling Energy Expenditure in Well-Trained Triathletes?
Authors: Delextrat Anne , Brisswalter Jeanick , Hausswirth Christophe , Bernard Thierry , Vallier Jean-Marc
Published: June 2009

The purpose of this study was to determine the effects of a 1,500-m swim on energy expenditure during a subsequent cycle task. Eight well-trained male triathletes (age 26.0 ± 5.0 yrs; height 179.6 ± 4.5 cm; mass 71.3 ± 5.8 kg; [Formula: see text] 71.9 ± 7.8 ml kg−1•min−1) underwent two testing sessions in counterbalanced order. The sessions consisted of a 30-min ride on the cycle ergometer at 75% of maximal aerobic power (MAP), and at a pedaling frequency of 95 rev•min−1, preceded either by a 1,500-m swim at 1.20 m•s−1 (SC trial) or by a cycling warm-up at 30% of MAP (C trial). Respiratory and metabolic data were collected between the 3rd and the 5th min, and between the 28th and 30th min of cycling. The main results indicated a significantly lower gross efficiency (13.0%) and significantly higher blood lactate concentration (56.4%), [Formula: see text] (5.0%), HR (9.3%), [Formula: see text] (15.7%), and RF (19.9%) in the SC compared to the C trial after 5 min, p <  0.05. After 30 min, only [Formula: see text] (7.9%) and blood lactate concentration (43.9%) were significantly higher in the SC compared to the C trial, p <  0.05. These results confirm the increase in energy cost previously observed during sprint-distance triathlons and point to the importance of the relative intensity of swimming on energy demand during subsequent cycling. Key words: lactate, oxygen uptake, intensity, exercise duration, performance
Torso Stabilization Reduces the Metabolic Cost of Producing Cycling Power
Authors: McDaniel John , Subudhi Andrew , Martin James C.
Published: June 2009

Many researchers have used cycling exercise to evaluate muscle metabolism. Inherent in such studies is an assumption that changes in whole-body respiration are due solely to respiration at the working muscle. Some researchers, however, have speculated that the metabolic cost of torso stabilization may contribute to the metabolic cost of cycling. Therefore, our primary purpose was to determine whether a torso stabilization device would reduce the metabolic cost of producing cycling power. Our secondary purpose was to determine the validity of the ergometer used in this study. Nine male cyclists cycled on a Velotron cycle ergometer at mechanical power outputs intended to elicit 50, 75, and 100% of their ventilatory threshold at 40, 60, and 80 rpm, with and without torso stabilization. Power was controlled by the Velotron in iso-power mode and measured with an SRM powermeter. We determined metabolic cost by indirect calorimetery and recorded power output. Torso stabilization significantly reduced metabolic cost of producing submaximal power (1%), and reduction tended to be greatest at the lower pedaling rates where pedaling force was greatest (1.6% at 40 rpm, 1.2% at 60 rpm, 0.2% at 80 rpm). Power, measured with the SRM powermeter, was strongly correlated with that specified to the Velotron ergometer control unit (R2 > 0.99). We conclude that muscular contractions associated with torso stabilization elicit significant metabolic costs, which tend to be greatest at low pedaling rates. Researchers who intend to make precise inferences regarding metabolism in the working muscles of the legs may wish to provide torso stabilization as a means of reducing variability, particularly when comparing metabolic data across a wide range of pedaling rates. Key words: efficiency, economy, metabolism, static contraction, work
The Identification of Clinically Relevant Gait Variables in Children With Hypotonia
Authors: Chester Victoria
Published: June 2009

not available
Responses to Intermittent Swimming Sets at Velocity Associated With max
Authors: Libicz Sebastien , Roels Belle , Millet Gregoire P.
Published: June 2009

While the physiological adaptations following endurance training are relatively well understood, in swimming there is a dearth of knowledge regarding the metabolic responses to interval training (IT). The hypothesis tested predicted that two different endurance swimming IT sets would induce differences in the total time the subjects swam at a high percentage of maximal oxygen consumption [Formula: see text]. Ten trained triathletes underwent an incremental test to exhaustion in swimming so that the swimming velocity associated with [Formula: see text][Formula: see text] could be determined. This was followed by a maximal 400-m test and two intermittent sets at [Formula: see text] (a) 16 × 50 m with 15-s rest (IT50); (b) 8 × 100 m with 30-s rest (IT100). The times sustained above 95% [Formula: see text] (68.50 ± 62.69 vs. 145.01 ± 165.91 sec) and 95% HRmax (146.67 ± 131.99 vs. 169.78 ± 203.45 sec, p = 0.54) did not differ between IT50and IT100(values are mean ± SD). In conclusion, swimming IT sets of equal time duration at [Formula: see text] but of differing work-interval durations led to slightly different [Formula: see text] and HR responses. The time spent above 95% of [Formula: see text]max was twice as long in IT100as in IT50, and a large variability between mean [Formula: see text] and HR values was also observed. Key words: interval training, maximal oxygen consumption, triathletes
The Versatility of the Pump-Perfused Rat Hindlimb Preparation: Examples Relating to Skeletal Muscle Function and Energy Metabolism
Authors: Baker David J. , Hepple Russell T.
Published: June 2009

The pump-perfused rat hindlimb model, in various forms, has been in use for several decades. There are many applications for this model, owing to the ability to control the content and rate of perfusion. In the context of exercise physiology this model has been put to particularly good use. In this report we summarize some of the central surgical differences between different versions of the pump-perfused rat hindlimb model, including the double hindlimb + trunk, double hindlimb alone, single hindlimb, and distal hindlimb-alone models. We also summarize specific elements of the perfusion medium and measurement of force used in our lab during assessment of muscle metabolic and contractile responses, and illustrate some of the differences from the in vivo condition that merit consideration. We then provide specific examples of how the single pump-perfused hindlimb and distal hindlimb-alone versions of this model have been used to study muscle function and energy metabolism. In this context we show how this model can be used to permit the experimenter to manipulate and control the rate of O2delivery and to add specific compounds that inhibit a particular aspect of muscle metabolism, such that in combination with measurements of the flux of specific substances across the muscle and/or fast-freezing of muscle after contractions, more can be understood about the metabolic state of the contracting muscles. Key words: aerobic metabolism, mitochondria, aging, adaptation
Application of Animal Models: Chronic Electrical Stimulation-Induced Contractile Activity
Authors: Ljubicic Vladimir , Adhihetty Peter J. , Hood David A.
Published: June 2009

Unilateral, chronic low-frequency electrical stimulation (CLFS) is an experimental model that evokes numerous biochemical and physiological adaptations in skeletal muscle. These occur within a short time frame and are restricted to the stimulated muscle. The humoral effects of whole body exercise are eliminated and the nonstimulated contralaterai limb can often be used as a control muscle, if possible effects on the contralateral side are considered. CLFS induces a fast-to-slow transformation of muscle because of alterations in calcium dynamics and myofibrillar proteins, and a white-to-red transformation because of changes in mitochondrial enzymes, myoglobin, and the induction of angiogenesis. These adaptations occur in a coordinated time-dependent manner and result from altered gene expression, including transcriptional and posttranscriptional processes. CLFS techniques have also been applied to myocytes in cell culture, which provide a greater opportunity for the delivery of pharmacological agents or for the application of gene transfer methodologies. Clinical applications of the CLFS technique have been limited, but they have shown potential therapeutic value in patients in whom voluntary muscle contraction is not possible due to debilitating disease and/or injury. Thus the CLFS technique has great value for studying various aspects of muscle adaptation, and its wider scientific application to a variety of neuromuscular-based disorders in humans appears to be warranted. Key words: skeletal muscle, muscle plasticity, endurance training, mitochondrial biogenesis, fiber types
Regulation of Fatty Acid Transport Across the Mitochondrial Membranes in Human and Rodent Skeletal Muscle
Authors: Bezaire Veronic S.
Published: June 2009

not available
Oxidative Stress Response in Normal and Antioxidant Supplemented Rats to a Downhill Run: Changes in Blood and Skeletal Muscles
Authors: You Tongjian , Goldfarb Allan H. , Bloomer Richard J. , Nguyen Linh , Sha Xin , McKenzie Michael J.
Published: June 2009

The purpose of this study was to determine if changes in oxidative stress biomarkers in blood and skeletal muscles are similar in normal and antioxidant supplemented rats after a downhill run. Sixty-six male Sprague-Dawley rats were pretreated with a normal rat diet or diet + antioxidants (2,000 mg vitamin C + 1,000 IU vitamin E/kg diet) for 2 weeks. Exercised rats ran 90 min on a rodent treadmill at a speed of 16 m/min at-16°grade. Rats were sacrificed either at rest, immediately, 2 hrs, or 48 hrs postexercise. Malondialdehyde (MDA) and protein carbonyl (PC) concentrations and glutathione status in blood, vastus lateralis (white fast-twitch), vastus intermedius (red fast-twitch), and soleus (slow-twitch) muscles were determined. A significant increase from rest in PC occurred in plasma, vastus intermedius and soleus muscle 2 hrs after the downhill run (p <  0.05), with no changes observed at any other times postexercise. Antioxidant supplementation significantly decreased PC concentrations in both vastus intermedius and soleus muscles at all times combined (p <  0.05). MDA and glutathione status in blood and muscles were unaffected by either the downhill run or antioxidant treatment. For PC and MDA, the concentrations were lower in blood as compared to skeletal muscle, with the opposite finding for oxidized glutathione; however, the pattern of response postexercise was similar. These data indicate that (a) PC, but not MDA or oxidized glutathione, is elevated transiently following downhill running in male rats; (b) the elevation in PC postexercise occurs in plasma, vastus intermedius, and soleus muscles; (c) antioxidant therapy can attenuate PC in vastus intermedius, and soleus muscles; and (d) while the concentrations of oxidative stress biomarkers differ between blood and the various skeletal muscles, the pattern of response postexercise is similar. Key words: protein carbonyls, lipid peroxidation, eccentric exercise
Effects of Mild Leg Exercise in a Seated Position on Haemostatic Parameters Under Normobaric Hypoxic Conditions
Authors: Schiffer Thorsten , Struder Heiko K. , Predel Hans-Georg , Hollmann Wildor
Published: June 2009

This study tested the hypothesis that in humans mild leg exercise affects haemostasis in normobaric hypoxia and thus avoids the development of a deep venous thrombosis (DVT). Eight young men breathed in a 15.4% oxygen in nitrogen gas mixture for 2 hrs while seated at rest (R) or seated and performing a 3-min mild leg exercise program (Ex) at 15-min intervals to assess the impact of mild leg exercise on haemostatic parameters related to the risk of developing DVT, as has been discussed for hypobaric hypoxic conditions during commercial airline travel. Capillary blood gases were analysed every 30 min. Heart rate was monitored continuously. Haemostatic parameters were analysed from venous blood at the beginning, after 1 and 2 hrs, and after a 30-min resting period in normoxic conditions. Plasminogen-activator-inhibitor-1 diminished in both tests in hypoxia, but not after the resting period. Antithrombin-III decreased in R in the hypoxic period. Platelet count, international normalized ratio, partial thromboplastin time remained unchanged, as did highly sensitive parameters like tissue-plasminogen-activator, α2-antiplasmin, d-dimers, thrombin-antithrombin-III-complexes, and prothrombin-fragments 1 and 2. The haematocrit decreased significantly in R. The mild leg execise prevented the decrease of antithrombin-III and caused an increase in haematocrit after an initial drop in the first hour. The present study revealed that normobaric hypoxia did not have clinically relevant effects on haemostasis in humans. Mild leg exercise carried out under those conditions did not lead, via alterations in haemostasis, to a reduced risk of DVT. Key words: local aerobic exercise, haemostasis, hypoxia, thrombosis
Oxidative Stress After Three Different Intensities of Running
Authors: Schneider Cláudia Dornelles , Barp Jaqueline , Ribeiro Jerri Luiz , Belló-Klein Adriane , Oliveira Alvaro Reischak
Published: June 2009

In 8 trained subjects (T) and 9 untrained subjects (UT), lipid peroxidation (LPO), total antioxidant capacity (TRAP), superoxide dismutase, catalase, and glutathione peroxidase (GPx) activities were measured in the blood before and after three different intensities of exercise on the treadmill, determined from ventilatory threshold and maximal oxygen uptake data, obtained from a maximal aerobic power test. In plasma, LPO decreased from 3589 ± 193 to 3274 ± 223 cps•mg Hb−1(p <  0.05), and TRAP increased from 304 ± 45 to 384 ± 57 µmol•L−1trolox (p <  0.05) after high intensity exercise in T. GPx activity increased in the T group as compared to the UT group, after exercise in moderate (25.90 ± 3.79 to 15.05 ± 3.23 nM•min−1•mg protein−1) and high (21.75 ± 4.91 to 12.1 ± 2.46 nM•min−1•mg protein−1) intensities (p <  0.05). Superoxide dismutase activity increased after exercise at low (8.35 ± 0.85 to 9.23 ± 1.03 U SOD•mg protein−1) and moderate (8.89 ± 0.98 to 10.44 ± 0.86 U SOD•mg protein−1) intensity in UT (p <  0.05). There were no changes in catalase activity. These findings indicate that exercise in this model did not increase lipid peroxidation, probably because of the alterations in TRAP and enzymatic antioxidants. Key words: free radicals, lipid peroxidation, erythrocytes, antioxidant enzymes, exercise
Effect of Creatine and Protein Supplementation Combined With Resistance Training on Muscle Mass and Strength in Older Men
Authors: Candow Darren G.
Published: June 2009

not available
Anaerobic Capacity: A Maximal Anaerobic Running Test Versus the Maximal Accumulated Oxygen Deficit
Authors: Maxwell Neil S. , Nimmo Myra A.
Published: June 2009

The present investigation evaluates a maximal anaerobic running test (MART) against the maximal accumulated oxygen deficit (MAOD) for the determination of anaerobic capacity. Essentially, this involved comparing 18 male students performing two randomly assigned supramaximal runs to exhaustion on separate days. Post warm-up and 1, 3, and 6 min postexercise capillary blood samples were taken during both tests for plasma blood lactate (BLa) determination. In the MART only, blood ammonia (BNH3) concentration was measured, while capillary blood samples were additionally taken after every second sprint for BLa determination. Anaerobic capacity, measured as oxygen equivalents in the MART protocol, averaged 112.2 ± 5.2 ml∙kg−1∙min−1. Oxygen deficit, representing the anaerobic capacity in the MAOD test, was an average of 74.6 ± 7.3 ml∙kg−1. There was a significant correlation between the MART and MAOD (r =.83, p <.001). BLa values obtained over time in the two tests showed no significant difference, nor was there any difference in the peak BLa recorded. Peak BNH3 concentration recorded was significantly increased from resting levels at exhaustion during the MART. Key words: supramaximal intermittent exercise, treadmill running performance, blood lactate, ammonia
Allometry of Anaerobic Performance: A Gender Comparison
Authors: Batterham Alan M. , Birch Karen M.
Published: June 2009

Physiological variables must often be scaled for body size differences to permit meaningful comparisons between groups. Using multivariate allometric scaling (MAS), this study aimed to compare the anaerobic performance of adult males and females in 12 pairs matched for physical activity status. Peak power output (PPO) was assessed via a 30-s supramaximal cycle ergometer test. Fat-free mass (FFM) and thigh muscle and bone cross-sectional area (CSA) were determined anthropometrically and served as indicators of active musculature. The MAS revealed power functions of the form PPO = a∙genderc∙FFMb (or CSAb). Common b exponents of 0.1 were identified for both FFM and CSA (negative allometry). Sex differences were found in absolute PPO (1,252 vs. 681 W, p <.05). Comparison of scaled PPO data via ANCOVA (FFM0.1 and CSA0.1 entered as cavariates) did not eliminate the sex difference (adjusted means 1,243 vs. 690 W, p <.05). The results suggest that the superior anaerobic performance of males in this sample is independent of size of the involved musculature. Key words: allometric scaling, sex differences, peak power output, anthropometry.
Peak Oxygen Consumption and Ventilatory Thresholds on Six Modes of Exercise
Authors: Smith Thomas D. , Thomas Tom R. , Londeree Ben R. , Zhang Qiang , Ziogas George
Published: June 2009

In order to compare responses on six modes of exercise for maximal oxygen consumption [Formula: see text] and ventilatory thresholds (VT-I, VT-2), 10 male recreational exercisers (23 ± 3 yrs) completed incremental maximal tests on treadmill, stationary skier, shuffle skier, stepper, stationary cycle, and rower. After extensive habituation, [Formula: see text], VT-1, and VT-2 were determined during each maximal bout. A MANOVA followed by ANOVAs, Tukey post hoc tests, and noncentral F tests indicated that the treadmill elicited a significantly higher peak oxygen consumption than did the other modes, and the skier and stepper values were higher than the rower. [Formula: see text] at VT-1 was higher on the treadmill than cycle. The treadmill also elicited a higher [Formula: see text] at VT-2 than the shuffle skier, cycle, and rower. However, no differences were observed among modes for VT-1 and VT-2 when expressed as a percentage of [Formula: see text]. These results suggest that the treadmill elicits a higher aerobic capacity measure than other modes, but the ventilatory threshold responses [Formula: see text] are similar among modes. Key words: exercise mode, aerobic capacity, lactate threshold
Heat Strain in Protective Clothing Following Hot-Wet or Hot-Dry Heat Acclimation
Authors: McLellan Tom M. , Aoyagi Yukitoshi
Published: June 2009

The purpose of the present study was to compare the heat strain while wearing nuclear, biological, and chemical (NBC) protective clothing following a hot-wet (HW) or hot-dry (HD) heat acclimation protocol. Twenty-two males were assigned to groups HW (n = 7), HD (n = 8), or control (C, n = 7). Subjects were evaluated during continuous treadmill walking while wearing lightweight combat clothing and during intermittent exercise while wearing the NBC protective clothing. While wearing Combat clothing, greater decreases in rectal temperature (Tre), mean skin temperature [Formula: see text], and heart rate were observed for both acclimation groups. For the NBC clothing trials, lower Tre, [Formula: see text], and heart rates were observed only for group HW. The time required for Tre to increase 1.0 °C and 1.5 °C was significantly delayed for groups HW and HD. Sweat evaporation increased for HW, whereas no change was found for HD. The most significant changes in Tre, [Formula: see text], and heart rate while wearing the NBC protective clothing occur following heat acclimation that involves wearing the clothing during exercise. Key words: rectal temperature, mean skin temperature, heart rate, sweat rate
Reliability and Validity of a Portable Metabolic Measurement System
Authors: Melanson Edward L. , Freedson Patty S. , Hendelman Devra , Debold Edward
Published: June 2009

The purpose of this study was to assess the reliability and validity of a portable metabolic system (TEEM 100) during submaximal and maximal [Formula: see text] exercise using a computer-based metabolic system as the reference system (REF). Between repeated trials of submaximal exercise at three constant loads, differences in ventilation [Formula: see text] and oxygen consumption [Formula: see text] were 0.2 ± 4.9 L∙min−1 and 0.03 ± 0.10 L∙min−1 for REF, and 1.9 ± 0.7 L∙min−1 and 0.00 ± 0.17 L∙min−1 for TEEM 100. Pooled intraclass reliability coefficients for [Formula: see text] and [Formula: see text] calculated from the repeated submaximal trials were r =.89 and r =.94 for REF, and r =.86 and r =.94 for the TEEM 100. Respiratory exchange ratio (RER) measured by the TEEM 100 was significantly higher (p =.01) at only the lowest workload. At [Formula: see text], the TEEM 100 recorded significantly higher values for FeO2 (p =.01) and RER (p <.001). These results suggest that the TEEM 100 provides reliable and valid measurements of [Formula: see text] during submaximal and maximal exercise. Key words: oxygen consumption, indirect calorimetry, portable analysis, exercise, metabolism
Lower Leg High-Intensity Resistance Training and Peripheral Hemodynamic Adaptations
Authors: Bond Jr. Vernon , Johnson Arthur T. , Vaccaro Paul , Wang Paul , Adams Richard G. , Tearney Russell J. , Millis Richard M. , Franks B. Don , Bassett Jr. David R.
Published: June 2009

High-intensity resistance (HIR) training has been associated with muscle hypertrophy and decreased microvascular density that might produce a blood flow limitation. The effect of HIR training on lower leg maximal blood flow and minimum vascular resistance (Rmin) during reactive hyperemia were investigated in 7 healthy males. The gastrocnemius-soleus muscles of one leg were trained using maximal isokinetic concentric contractions for 4 weeks; the nontrained leg was the control. Lower leg blood flow was measured by venous occlusion plethysmography. Lower leg muscle volume was determined using magnetic resonance imaging. Peak isokinetic torque increased in both the trained (T) and nontrained (NT) legs (p <.05). Lower leg muscle volume increased by 2% in the T leg only (p <.05). In the T leg, maximal blood flow decreased and Rmin increased (p <.05); no hemodynamic change was detected in the NT leg. It is concluded that HIR training of the calf muscles is associated with a decrease in hyperemia-induced blood flow; thereby, indicating a blood flow limitation to the calf muscles. Key words: Isokinetic strength training, reactive hyperemia
The Potential Role of Insulin-Like Growth Factors in Skeletal Muscle Regeneration
Authors: MacGregor Jamie , Parkhouse Wade S.
Published: June 2009

The role of the insulin-like growth factors I and II (IGF-I and IGF-II), previously known as the somatomedins, in general growth and development of various tissues has been known for many years. Thought of exclusively as endocrine factors produced by the liver, and under the control of growth hormone, the somatomedins were known as the intermediaries by which growth hormone exerted its cellular effects during tissue growth and maturation. Eventually it was discovered that virtually every tissue type is capable of autocrine production of the IGFs, and their involvement in skeletal muscle tissue repair and regeneration became apparent. Recent advances in technology have allowed the characterisation of many of the different growth factors believed to play a role in muscle regeneration, and experimental manipulations of cells in culture have provided insight into the effects of the various growth factors on the myoblast. This paper explores the potential role of the IGFs in skeletal muscle regeneration. A critical role of IGF-II in terminal differentiation of proliferating muscle precurser cells following injury is proposed. Key words: growth factors, myogenesis, skeletal muscle regeneration
Endurance-Trained and Untrained Skeletal Muscle Bioenergetics Observed With Magnetic Resonance Spectroscopy
Authors: Guthrie Bart M. , Frostick Simon P. , Mikulis David J. , Marshall K. Wayne , Goodman Jack , Plyley Mike J.
Published: June 2009

Resting and submaximal isometric exercise 31P magnetic resonance spectroscopy (MRS) was carried out on 7 endurance-trained males (26.0 ± 3 yrs) and 7 sedentary males (27.0 ± 4 yrs). Spectral analysis provided peak areas of phosphocreatine (PCr), inorganic phosphate (Pi), adenosine triphosphate (ATP), and the chemical shift of Pi relative to PCr. The ratio of PCr/Pi was moderately lower during rest (preexercise p =.13, postexercise p =.18), and significantly higher during exercise (p < .05) in the trained subjects. Intracellular pH patterns were the same for both groups; a transient alkalosis was observed at the onset of exercise with a return to resting levels after 2 min. Differences suggest improved ATP resynthesis rate in the trained subjects during exercise. Intracellular pH changes can be attributed to the utilization of hydrogen ions that accompany PCr hydrolysis during work. The findings are congruent with previous reports indicating a superior oxidative capacity in trained skeletal muscle. Key words: 31P MRS, isometric exercise, phosphocreatine, inorganic phosphate, adenosine triphosphate, intracellular pH
Maximal Accumulated Oxygen Deficit of Resistance-Trained Men
Authors: Pizza Francis X. , Naglieri Thomas A. , Holtz Robert W. , Mitchell Joel B. , Starling Raymond D. , Phillips Melody D. , Cavender Daniel L. , Braun William A.
Published: June 2009

The primary purpose of the study was to compare maximal accumulated oxygen deficit (MAOD) in resistance-trained (RT), endurance-trained (ET), and untrained men (UT). A secondary purpose was to determine the influence of leg muscle mass (MM) on MAOD by examining the relationship between MM and MAOD and by comparing MAOD expressed relative to MM between the groups. MAOD was determined during 2-4 min of constant-load fatiguing cycling. MM, estimated via anthropometric measurements, was higher (p <.05) for RT (mean ± SE; 25.5 ± 3.4 kg) compared to ET (20.3 ± 3.5) and UT (21.6 ± 3.4). MAOD in liters O2 eq was larger in RT (4.75 ± 0.3) compared to UT (3.07 ± 0.3) and ET (3.75 ± 0.3). A significant positive correlation was observed between MAOD (LO2 eq) and MM (kg) for RT only (RT, r =.85; ET, r =.55; UT, r =.20). Based on the correlational and mean MM data, the higher MAOD (LO2 eq) in RT relative to ET and UT is predominantly the result of their larger leg muscle mass. Key words: exercise, anaerobic capacity, muscle mass
Androgen Use by Athletes: A Reevaluation of the Health Risks
Authors: Street Chris , Antonio Jose , Cudlipp David
Published: June 2009

It has been estimated that 1 to 3 million male and female athletes in the United States have used androgens. Androgen use has been associated with liver dysfunction, altered blood lipids, infertility, musculotendinous injury, and psychological abnormalities. Although androgens have been available to athletes for over 50 years, there is little evidence to show that their use will cause any long-term detriment; furthermore, the use of moderate doses of androgens results in side effects that are largely benign and reversible. It is our contention that the incidence of serious health problems associated with the use of androgens by athletes has been overstated. Key words: testosterone, exercise, muscle, steroids, hypertrophy
Gender Differences in Isometric Contractile Properties and Fatigability in Elderly Human Muscle
Authors: Hicks Audrey L. , McCartney Neil
Published: June 2009

This study had two purposes: to compare the isometric contractile characteristics and fatigability in the elbow flexors (EF) and ankle dorsiflexors (DF) in older males and females (60-80 years), and to determine the effects of almost 2 years of twice weekly dynamic weight-lifting training on these properties One hundred nine male and female subjects completed the 22-month intervention, 54 in the exercise group and 55 in the control group. Isometric contractile properties and fatigue characteristics were assessed at baseline, 10 months, and 22 months. At baseline, males were significantly stronger (p <.05) than females in evoked twitch torque (Pt) and maximal voluntary strength (MVC) in both EF and DF. Females exhibited significantly less fatigue (expressed either absolutely or relatively) than males in both Pt and MVC during a 3-min protocol of intermittent MVCs (5 s contraction; 2 s rest). There were no significant effects of the 22 months of dynamic training on either the isometric contractile properties or the fatigue characteristics, suggesting a very strong and persistent specificity of training effect. Key words: aging, muscle, fatigue, training
Heart Rate Variability at Rest and Exercise: Influence of Age, Gender, and Physical Training
Authors: Gregoire Jason , Tuck Stephanie , Hughson Richard L. , Yamamoto Yoshiharu
Published: June 2009

The adaptive responses of the cardiovascular system to regular physical activity appear to include a reduction in sympathetic (SNS) activity and an increase in parasympathetic (PNS) activity during rest and at different absolute intensities of exercise. In a cross-sectional design, trained individuals who exercised at least 5 days/week for 45 min/day or more were compared with age- and gender-matched untrained controls. There was a relative bradycardia in the trained groups at rest and at the same absolute intensity of exercise in both young and middle-aged subjects. There were no differences in indicators of PNS and SNS activity at rest in young subjects. There was a reduced SNS activity and increased PNS activity in middle-aged trained subjects versus their age-matched controls. Spectral analysis was capable of showing changes in autonomic control of heart rate at rest and across intensities of exercise. These data showed significant shifts to increased PNS and reduced SNS indicators at rest in trained versus untrained middle-aged subjects and in females in both age groups versus males. Key words: spectral analysis, parasympathetic nervous system, sympathetic nervous system, female, male, fitness
A Comparison of Three Fluid Replacement Strategies for Maintaining Euhydration During Prolonged Exercise
Authors: Schroeder Jan M. , Heck Kris L. , Potteiger Jeffrey A.
Published: June 2009

The effectiveness of a new water delivery system (the Water-Del) was examined for maintaining euhydration compared to other fluid replacement strategies. Subjects (N = 10) performed three 60-min cycling trials (@ 50% of VO2max) in an environmental chamber (27 °C; RH = 50%). Trials were randomly assigned from Water-Del (metered: 200 ml water every 15 min), ad libitum every 15 min (ad-lib-15), and ad libitum (ad-lib). Total water intake (TWI), changes in plasma volume (ΔPV), body Weight (ΔBW), thirst, skin temperature (Tsk), and heart rate (HR) were measured. A significant difference (p ≤.05) among trials was observed for TWI, with metered (1.200 ± 0.12 ml) being greater than ad-lib-15 (358 ± 48 ml) and ad-lib (522 ± 106 ml). No significant difference was found for ΔPV. A significant difference (p ≤.05) for ΔHW was observed with metered (0.28 ± 0.16 kg) being different than ad-lib-l5 (−0.63 ± 0.12 kg) and ad-lib (−0.34 ± 0.14 kg). No significant differences (p > .05) were found for thirst, Tsk, or HR. The Water-Del provides for greater fluid intake during exercise compared to other replacement strategies. Key words: hydration, dehydration, plasma volume
Frequent Serum Sampling in Healthy Men Discloses Testosterone Peaks Exacerbated by Testosterone Propionate Administration
Authors: Brisson Guy R. , Sáinz Ángel Guttiérez , Ayotte Christiane , Gareau Raynald , Senécal Louis , Castillo Manuel J.
Published: June 2009

Interval samplings uncover blood diurnal oscillations for several hormones, highlighting the importance of short time intervals in the disclosure of subtle pulsatile patterns of some peptide hormones, namely LH. In a study designed to develop new probes against steroid misuse, venous blood was sampled at 5-min intervals for 4 hours from 12 eugonadal adult male athletes, 6 receiving transcutaneous administrations of testosterone propionate and 6 placebo subjects. Brief supraphysiologic serum testosterone peaks were disclosed, the amplitude and frequency of these peaks being larger for the treated group. No solid explanation could be given to explain these bursts. Neither the binding/dissociation kinetics of SHBG molecules with and without increased circulating level of dihydrotestosterone, nor brief testosterone-inducing LH bursts, nor increased Leydig cell release could be invoked to explain these peaks. Their occurrence, although relatively rare, could represent a threat and lead to improper treatment. Key words: blood testosterone, transcutaneous administration
Relationship Between Aerobic Fitness and Metabolic Recovery From Intermittent Exercise in Endurance Athletes
Authors: Bell Gordon J. , Snydmiller Gary D. , Davies Diane S. , Quinney H. Art
Published: June 2009

This investigation examined the relationship between several different aerobic fitness test results and measurements of metabolic recovery from intermittent, high-intensity exercise in 16 male cyclists. No significant correlations were found between maximal oxygen consumption, ventilation threshold, various submaximal endurance measures and the rate of metabolic recovery, net excess postexercise oxygen consumption, or blood lactate removal after intermittent high-intensity exercise except for submaximal heart rate (r = .66, p < .05). These data indicate that aerobic fitness assessments do not indicate the ability to recover after intermittent, high-intensity exercise in endurance-trained cyclists. Key words: maximal oxygen consumption, recovery oxygen consumption, ventilation threshold, lactate, heart rate
The Effect of Eumenorrheic Menstrual Cycle Phase on Physiological Responses to a Repeated Lifting Task
Authors: Birch Karen M. , Reilly Thomas
Published: June 2009

Cyclic variations in physiological and endocrinolgical baselines are known to be consistent with the eumenorrheic (healthy) menstrual cycle. The aim of this study was to examine the interaction of these variations with the physiological responses to repeated lifting. Sixteen females visited the laboratory in each of five phases of their menstrual cycle. During each visit, subjects performed a repetitive lifting task, lifting a weighted box, from knee to shoulder height, at six repetitions per minute for 10 min. Oxygen consumption, minute ventilation, heart rate (HR), and perceived exertion were monitored throughout the task. The variation in physiological and subjective responses to lifting with menstrual cycle phase did not reach statistical significance (p > .05). However, the HR response to lifting was elevated by approximately 10 beats min−1 in the postovulatory phases of the cycle (effect size > 0.61). Although the impact of the menstrual cycle upon lifting performance is minimal, alterations in HR must be taken into account in determining new international standards for manual handling. Key words: lifting, maximal oxygen consumption, subjective response, effect size
Dynamics of the Ventilatory Response to Step Changes in End-Tidal PCO2 in Older Humans
Authors: Poulin Marc J. , Cunningham David A. , Paterson Donald H.
Published: June 2009

The purpose of this study was to examine the ventilatory response to carbon dioxide (CO2) in young and older men. Six square-wave steps of end-tidal CO2 (PETCO2) were administered in euoxia (PETO2 = 100 torr), hyperoxia (PETO2 = 500 torr), and mild hypoxia (PETO2 = 60 torr) The peripheral and central chemoreflex loops were described by three parameters including a gain (gp and gc), time constant of the response(τp, τc), and a time delay (Tp, Tc), respectively. The young and older men showed similar characteristics for Tp and Tc, with Tp, being 3 to 5 s shorter than Tc. In hypoxia, the ventilatory responses of the old group were characterised by a significantly smaller gc and a smaller gp. In hypoxia, τc was significantly shortened from its euoxic value in the young group, but not in the old group. Thus, this study demonstrated that in older men, the ventilatory responses to CO2 in euoxia and hyperoxia are similar to younger men, while in hypoxia the ventilatory responses are characterised by smaller gain terms. Key words: ageing, hypercapnia, hypoxia, hyperoxia, control of breathing
Glycogen Storage in Fetuses of Trained Pregnant Rats
Authors: Houghton Pamela E. , Mottola Michelle F. , Mezzapelli Jamie , Vandermolen Richard , Christopher Paul D.
Published: June 2009

The purpose was to determine if running 30 m/min on a 10° incline, 60 min/day for 5 days/week altered fetal glycogen storage in prepregnancy trained rats. Animals that exercised for 3 weeks prior to pregnancy either continued the same exercise program until Day 19 of gestation (pregnant running group [PR]), or ceased exercising at conception (pregnant controls [PC]). A separate set of animals did not exercise either before or during pregnancy (pregnant nonrunning control group [PNRC]). On Day 20 of gestation, fetal organs and placenta were weighed and analyzed for glycogen concentration. Glycogen concentrations were not different in either fetal liver, heart, or placenta of PR rats compared to PNRC animals. However, fetal liver glycogen concentration was significantly lower in the fetal heart and liver of PC animals compared to glycogen measured in both PNRC and PR animals (p < .0.5). These results suggest that exercise of this intensity does not compromise fetal glycogen storage in trained pregnant rats. However, chronic prepregnancy exercise and then abrupt cessation of exercise at conception may compromise fetal growth and development. Key words: exercise training, pregnancy, fetal glycogen
Muscle Fatigue and Induction of Stress Protein Genes: A Dual Function of Reactive Oxygen Species?
Authors: Essig David A. , Nosek Thomas M.
Published: June 2009

Definitive characterization of the mechanisms of skeletal muscle fatigue is still an area of active investigation. One emerging theory concerns a role for the reactive oxygen species (ROS) produced primarily as a consequence of elevated rates of mitochondrial respiration. It has been theorized that the long-lasting effects of low-frequency fatigue (LFF) can be attributed to disruption of some stage of the excitation contraction coupling (ECC) process. Recent evidence suggests that ROS likely denature one or more proteins directly associated with the sarcoplasmic reticulum (SR) Ca2+ release mechanism. Given the potential of ROS to damage intracellular proteins during subsequent bouts of muscle contractions, the capacity of preexisting antioxidant pathways may be complemented by the synthesis of inducible heat-stress proteins (HSPs). HSPs collectively function to maintain cellular protein conformation during stressful proteotoxic insults. The goal of this article is to illustrate how recent findings suggest a dual role of ROS generated during muscle contractions. Key words: skeletal muscle, gene expression, sarcoplasmic reticulum
A Model of Oxygen Transport Capacity Changes for Independently Living Older Men and Women
Authors: Cunningham David A. , Paterson Donald H. , Koval John J , St. Croix Claudette M.
Published: June 2009

The purpose of the present investigation was to describe, for a subset of a large random survey of men and women, restricted to the ages of 55 to 85 years, the physiological decay pattern for aerobic fitness and contributing factors of cardiovascular and pulmonary function. The time course of the age-related changes in maximal oxygen uptake [Formula: see text] ventilatory threshold (TVE), maximal ventilation [Formula: see text] maximal heart rate (HRmax), and O2 pulse [Formula: see text] were examined by fitting the data to a decaying exponential model by use of a least-squares parameter estimation technique. The time constant (τ) was used to describe the rate of decline. The women showed a much slower decline in [Formula: see text] (τ = 47.4 years) and τVE (τ = 83.3 years) than the men (τ = 20.8 and 15.4 years, respectively). There was a significant age-related decrease in body weight (0.45 kg yr−1) in the men, whereas the women showed no change. Pulmonary function did not limit performance based on the very slow decline in [Formula: see text] and the normal FEV1.0. The decay in HRmax was better described by a linear model, resulting in an extremely slow τ. Maximal O2 pulse clearly exhibited an exponential decay, with a shorter τ (τmen = 13,5 years; τwomen = 28.5 years) than any other variable. Key words: aging, exercise, maximal oxygen uptake, ventilatory threshold