bluuebunny/crossref_metadata_2025 huggingface dataset:
Reliability of Concentric Ankle Dorsiflexion Fatigue Testing
Authors: Porter Michelle M. , Holmbäck Anna Maria , Lexell Jan
Published: June 2009

The purpose of this study was to determine the reliability of an isokinetic test for ankle dorsiflexion fatigue on a Biodex dynamometer. Young (21 to 32 years), recreationally active men (n = 10) and women (n = 10) performed 50 concentric (60 • s−1) dorsiflexion contractions, on two different occasions. Total work (TW), losses in work (work fatigue; WF), as well as relative losses in peak torque, an example being "3-3" which compared the first three to last three repetitions, were measured. The intra-class correlation coefficients (ICC2,1) and coefficients of variation (CV), as well as the Bland-Altman plots and analyses showed that the variables using peak torque and TW were more reliable than WF, with WF having a CV of 11.3% and the best peak torque variable, 3-3, having a CV of 5.6%. In conclusion, ankle dorsiflexion fatigue can be reliably assessed on a Biodex dynamometer. Key words: ankle joint, skeletal muscle, reproducibility of results, muscle fatigue, physical endurance
New Perspectives on the Storage and Organization of Muscle Glycogen
Authors: Shearer Jane , Graham Terry E.
Published: June 2009

Due to its large mass, skeletal muscle contains the largest depot of stored carbohydrate in the body in the form of muscle glycogen. Readily visualized by the electron microscope, glycogen granules appear as bead-like structures localized to specific subcellular locales. Each glycogen granule is a functional unit, not only containing carbohydrate, but also enzymes and other proteins needed for its metabolism. These proteins are not static, but rather associate and dissociate depending on the carbohydrate balance in the muscle. This review examines glycogen-associated proteins, their interactions, and roles in regulating glycogen metabolism. While certain enzymes such as glycogen synthase and glycogen phosphorylase have been extensively studied, other proteins such as the glycogen initiating and targeting proteins are just beginning to be understood. Two metabolically distinct forms of glycogen, pro- and marcoglycogen have been identified that vary in their carbohydrate complement per molecule and have different sensitivities to glycogen synthesis and degradation. Glycogen regulation takes place not only by allosteric regulation of enzymes, but also due to other factors such as subcellular location, granule size, and association with various glycogen-related proteins. Keywords: glycogen-associated proteins, skeletal muscle, carbohydrate metabolism, proglycogen, macroglycogen.
Modulation of Force Development by Na+, K+, Na+ K+ Pump and KATP Channel During Muscular Activity
Authors: Renaud J.M.
Published: June 2009

Extracellular K+ concentration increases during exercise and especially during fatigue development. It has been proposed that K+ is an important factor in the etiology of skeletal muscle fatigue because it suppresses membrane excitability and eventually force development. Based on the effect of K+, it has then been proposed the Na+ K+ pump reduces increases in extracellular K+ concentration while the ATP-sensitive K+ channel (KATP channel) allows for rapid increases in extracellular K+ to suppress force development when ATP levels start to fall or when the levels of metabolic end-products become high. However, recent studies have now demonstrated that an increase in extracellular K+ concentration can be advantageous to muscle during exercise because it not only stimulates vasodilatation and the exercise pressor reflex, but it also potentiates force development when the Na+ concentration gradient is maintained. A new hypothesis is therefore proposed in which the Na+ K+ pump is important in maintaining the Na+ concentration gradient (and not the K+ concentration gradient as previously suggested), while the activation of KATP channels is important to increase the K+ efflux and extracellular concentration. This situation then optimizes the development of force during exercise. Another hypothesis is proposed in which more KATP channels are activated while the activity of the Na+ K+ pump is reduced when ATP levels start to decrease to allow for an accumulation of intracellular Na+ and further increases in extracellular K+ concentration, These concentration changes then reduce membrane excitability and force development (i.e., fatigue) to protect muscle against large ATP depletion and function impairment. Key words: fatigue, exercise, energy metabolism, ATP, lactic acid, adenosine, hydrogen ion
Effect of Contraction History on Torque Deficits by Stretches of Active Rat Skeletal Muscles
Authors: Willems Mark E.T. , Stauber William T.
Published: June 2009

Effects of contraction history on torque deficits by stretches of active skeletal muscles were examined. After three contractions using maximal and submaximal activation (80 and 20 Hz) at an ankle position of 40° (i.e., long muscle length) and with maximal activation at 120° (i.e., short muscle length), the isometric and stretch torques (15 stretches) of rat plantar flexor muscles (bout 1) were measured. Controls were unconditioned. Stretches (i.e., ankle rotation from 90° to 40°, velocity: 50°•s−1) were imposed on maximal isometric contractions at 90° (i.e. preloaded stretches). All groups performed a second bout following 2 hours of rest after bout 1. After maximal contractions at long muscle length, preload torque at 90° and stretch torque at 40° for stretch 1 of bout 1 were 25% and 18% lower than the other groups. However, for all groups, bout 1 ended and bout 2 began and ended with similar isometric and stretch torques. Stretches early in bout 2, with preloads similar to stretches in bout 1, had greater stretch torques resulting in larger torque deficits. Torque deficits, possibly caused by damage to muscle structures and excitation-contraction uncoupling, were not prevented by a history of isometric contractions. Different contraction histories can result in similar isometric torques but different stretch torques. Key words: injury, warm-up, isometric contractions, prevention, eccentric contractions
Acute High-Intensity Interval Training Improves Tvent and Peak Power Output in Highly Trained Males
Authors: Laursen Paul B. , Blanchard Michelle A. , Jenkins David G.
Published: June 2009

This study examined the effects of four high-intensity interval-training (HIT) sessions performed over 2 weeks on peak volume of oxygen uptake [Formula: see text] the first and second ventilatory thresholds (VT1, VT2) and peak power output (PPO) in highly trained cyclists. Fourteen highly trained male cyclists [Formula: see text] performed a ramped cycle test to determine [Formula: see text]VT1, VT2, and PPO. Subjects were divided equally into a HIT group and a control group. The HIT group performed four HIT sessions (20 × 60 s at PPO, 120 s recovery); the [Formula: see text] test was repeated < 1 wk after the HIT program. Control subjects maintained their regular training program and were reassessed under the same timeline. There was no change in [Formula: see text] for either group; however, the HIT group showed a significantly greater increase in VT1 (+22% vs. −3%), VT2 (+15% vs. −1%), and PPO (+4.3 vs. −4%) compared to controls (all P < .05). This study has demonstrated that HIT can improve VT1, VT2 and PPO, following only four HIT sessions in already highly trained cyclists. Key words: cycling, cyclists, heart rate, oxygen uptake, short-term training, ventilatory threshold
Apoptosis in Heart and Skeletal Muscle
Authors: Primeau Andy J. , Adhihetty Peter J. , Hood David A.
Published: June 2009

Apoptosis, or programmed cell death, is now recognized to be an important cellular event during normal development and in the progression of specific diseases. Apoptosis can be triggered by stimuli initiating outside of the cell, or within the mitochondria, leading to the activation of caspases and subsequent cell death. Although apoptosis has been widely studied in a variety of tissues over the last 5 years, skeletal muscle and heart have been relatively ignored in this regard. Research on apoptosis in cardiac muscle has recently taken on a higher profile as the recognition emerges that it may be an important contributor to specific cardiac pathologies, particularly in response to ischemia-reperfusion in which reactive oxygen species are formed. In skeletal muscle, very few studies have been done under specific physiological (e.g., exercise) and pathophysiological (e.g., dystrophies, denervation, myopathies) conditions. Skeletal muscle is unique in that it is mutli-nucleated, and evidence suggests that it can undergo individual myonuclear apoptosis as well as complete cell death. This review discusses the basic cellular mechanisms of apoptosis, as well as the current evidence of this process in cardiac and skeletal muscle. The need for more work in this area is highlighted, particularly in exercise and training. Key words: transcription factors, reactive oxygen species, mitochondria, caspase, mitochondrial permeability transition
Application of Simple Anthropometry in the Assessment of Health Risk: Implications for the Canadian Physical Activity, Fitness and Lifestyle Appraisal
Authors: Janssen Ian , Heymsfield Steven B. , Ross Robert
Published: June 2009

Incremental improvements in our knowledge of the associations between human body composition and disease have been facilitated by advances in research technology. Magnetic resonance imaging and computerized tomography are among the technological advances that have helped unravel the mechanisms that link body composition and disease. However, because the use of these methods in large-scale studies and field settings is impractical, the potential relationships between body composition and health risk rely on the use of anthropometric tools. Indeed, the application of simple anthropometry to identify relationships between body composition and health risk in clinical practice is no less valuable than the use of advanced technologies to gain insight into the mechanistic links between body composition and disease in the laboratory. Accordingly, the purpose of this review is to summarize current knowledge regarding the ability of anthropometry to predict health risk and to act as surrogate measures of total and abdominal fat distribution. Because the ultimate objective is to make recommendations for revision to the Healthy Body Composition section of the Canadian Physical Activity, Fitness and Lifestyle Appraisal (CPAFLA) manual, we focus on those anthropometric methods specific to CPAFLA. Consistent with this objective, when necessary we present original data to reinforce important concepts not suitably addressed in the literature. Key words: body composition, fat distribution, obesity, visceral fat, anthropometry
Statistical Analysis of Fiber Area in Human Skeletal Muscle
Authors: Mcguigan Michael R.M. , Kraemer William J. , Deschenes Michael R. , Gordon Scott E. , Kitaura Takashi , Scheett Timothy P. , Sharman Matthew J. , Staron Robert S.
Published: June 2009

Previous research has indicated that 50 fiber measurements per individual for type I and II fibers would be sufficient to characterize the fiber areas. This study replicated the work of McCall et al. (1998) using the three major fiber types (I, IIA, and IIB) and sampling larger populations of fibers. Random blocks of fibers were also examined to investigate how well they correlated with the overall mean average fiber area. Using random blocks of 50 fibers provided an accurate reflection of the type IIB fibers (r = 0.96-0.98) but not for the type I (r = 0.85-0.94) or IIA fibers (r = 0.80-0.91). Type I fibers were consistently reflected by a random block of 150 fibers (r = 0.95-0.98) while type IIA fibers required random blocks of 200 fibers (r = 0.94-0.98), which appeared to provide an accurate reflection of the cross-sectional area. These results indicate that for a needle biopsy different numbers of fibers are needed depending on the fiber type to accurately characterize the mean fiber population. Key words: fiber type, sample size, cross-sectional area, biopsy
Physical Activity, Aerobic Fitness, and Seven-Year Changes in Adiposity in the Canadian Population
Authors: Fortier Michelle D. , Katzmarzyk Peter T. , Bouchard Claude
Published: June 2009

Associations among baseline physical activity, aerobic fitness, changes in physical activity, and 7-y changes in adiposity were determined. The sample consisted of 602 males and 644 females, aged 20-69 y, from the 1981 Canada Fitness Survey and the 1988 Campbell's Survey. Questionnaire-derived measures of physical activity level consisted of activity energy expenditure (AEE) and time spent on physical activity. Participants were grouped into physical activity level categories by AEE and physical activity intensity (based on MET values), and physical activity level changes were determined from movement between tertiles of AEE from baseline to follow-up. Aerobic fitness levels at baseline were determined using the Canadian Aerobic Fitness Test. Changes in body mass, the sum of five skinfolds (SF5), and waist circumference (WC) were used as indicators of adiposity change. ANCOVA and multiple regression analyses indicated that neither baseline physical activity levels, intensity, physical activity change categories, nor aerobic fitness levels were significant predictors of changes in adiposity. In conclusion, physical activity was not predictive of 7-y changes in indicators of adiposity in this sample. Key words: weight gain, longitudinal study, obesity, lifestyle
Maximal Accumulated O2Deficit in Running and Cycling
Authors: Hill David W. , Davey Krista M. , Stevens Emily C.
Published: June 2009

The purpose of this study was to compare values for maximal accumulated O2deficit measured in running and cycling. Nine university students performed five fatiguing constant-velocity treadmill tests and five fatiguing constant-power cycle ergometer tests at intensities within the severe domain. O2deficit was determined making the traditional assumptions that (1) the O2demand increases linearly with the exercise intensity and (2) the O2demand is constant from the onset of exercise if the intensity is kept constant (Medbø, 1996). [Formula: see text] was 11% higher in running than in cycling. In contrast, O2deficit was ∼50% higher in cycling than treadmill running. Inspection of the data suggested that the O2demand may have been underestimated, especially in the treadmill tests. It was concluded that assumptions associated with measuring maximal accumulated O2deficit in running must be revisited. Key words: aerobic, anaerobic, cycling, running, [Formula: see text]
Ankle Plantar Flexion Strength in Resistance and Endurance Trained Middle-Aged Adults
Authors: Krishnathasan Dhivo , Vandervoort Anthony A.
Published: June 2009

Maximum concentric (CONC) and eccentric (ECC) strength of the ankle plantar flexor muscles were compared between middle-aged adults who regularly participated in resistance exercise training versus those who participated in weight-bearing endurance exercise. A total of 40 men and women with a mean age of 48.9 years (SD = 5.3) were tested for CONC and ECC plantar flexor (PF) strength, using an isokinetic device at 3 velocities: 30, 90 and 180°/s. Mean strength values for the groups of men and women involved in resistance exercise were consistently higher than those involved in the endurance training for the CONC tests, where values ranged from 35% to 46% (avg. 41%, p < .01), but less between-group difference was observed for the ECC loading condition: 4% to 30% (avg. 18%). Thus ECC/CONC ratios, which rose with increasing velocity, were consistently higher for the endurance group vs. resistance-trained. Finally, since concentric PF torque values were found to be quite low for the middle-aged women who did only endurance training, this movement may require preventive strengthening exercises. Key words: muscle, exercise, isokinetic, aging, human
Molecular Control of Capillary Growth in Skeletal Muscle
Authors: Haas Tara L.
Published: June 2009

Angiogenesis, the growth of new capillaries, enhances the oxygen delivery capacity of an existing vascular network. This adaptation is a well-documented occurrence in exercising skeletal muscle. The purpose of this review is to summarize our current understanding of the various stimuli that are involved in the initiation of capillary growth in skeletal muscle. The roles of humoral and mechanical signals in the cellular regulation of several key angiogenic players, vascular endothelial cell growth factor and matrix metalloproteinases, will be discussed. Evidence will be presented supporting the existence of angiogenesis processes that are distinct from the "classically" defined process. Determining how specific angiogenic stimuli can initiate unique patterns of capillary growth will provide insight into the complex task of developing effective pro-angiogenic therapies. Key words: endothelium, matrix metalloproteinases, growth factors, shear stress, muscle stretch
Physical Fitness in Young College Men and Women
Authors: Tremblay Angelo , Chiasson Luc
Published: June 2009

This study was designed to investigate fitness characteristics of college women and men (n = 427 and 423, respectively) aged 17-20 years whose values were compared to the data of the 1981 Canada Fitness Survey (CFS). Muscular fitness as revealed by the maximal number of arm extensions (push ups) was lower in subjects of this study compared to those tested in the 1981 CFS. On the other hand, body weight, waist circumference and the sum of five skinfolds were greater in subjects of the present study. These differences between the results of this study and those of the 1981 CFS were particularly pronounced in the upper percentile ranks. The classification of subjects on the basis of the number of grades completed during a step test revealed significant differences in subcutaneous adiposity between fitness subgroups. Reported participation in vigorous physical activities was also predictive of subcutaneous adiposity in men but to a lesser extent than the number of grades completed during a step test. When the number of grades and exercise participation were combined to detect between-group morphological differences, large differences in subcutaneous adiposity were observed in both men and women. This suggests that the effect of vigorous activity and aerobic fitness on adiposity may be much greater than what is generally perceived by health professionals and agencies. Keywords: exercise, fatness, adiposity, physical activity, obesity, adolescents
Evaluation of the Interchangeability of and Oxygen Uptake Efficiency Slope
Authors: Pichon Aurélien , Jonville Sophie , Denjean André
Published: June 2009

A reliable submaximal test for assessing cardiorespiratory function would be of interest in clinical practice. Baba et al. (1996) proposed the oxygen uptake efficiency slope (OUES) derived from the relation between oxygen uptake ([Formula: see text] and minute ventilation [Formula: see text] during incremental exercise. We evaluated the validity of OUES by comparing maximal oxygen uptake [Formula: see text] predicted from OUES to measured [Formula: see text] in 50 healthy males who performed a maximal treadmill test. They had widely differing physical fitness levels ([Formula: see text]range, 32.7 to 80.2 mlO2 ∙ min−1 ∙ kg−1). Predicted [Formula: see text] was not significantly different (p > 0.99) from measured [Formula: see text] (56.8 ± 7.0 vs. 56.8 ± 8.8 mlO2 ∙ min−1 ∙ kg−1). The limits of agreement (Bland & Altman, 1986) were plus or minus 10.5 mlO2 ∙ min−1 ∙ kg−1. Although OUES and [Formula: see text]were significantly correlated (r = 0.79), the wide interindividual variations in the difference between these two parameters may limit the usefulness of OUES in clinical practice. Key Words: exercise, testing, OUES, fitness, agreement
A Comparison of Skating Economy On-Ice and On the Skating Treadmill
Authors: Nobes K.J. , Montgomery D.L. , Pearsall D.J. , Turcotte R.A. , Lefebvre R. , Whittom F.
Published: June 2009

The purpose of this study was to compare skating economy and oxygen uptake (VO2) on-ice and on the skating treadmill (TM). Male varsity hockey players (n = 15, age = 21.0 yr) performed skating tests on a TM and on-ice. The subjects skated for 4 min at each of 3 submaximal velocities (18, 20, and 22 km • h−1), separated by 5 min of passive recovery. A VO2max test followed the submaximal tests and commenced at 24 km • h−1 with the velocity increasing by 1 km • hr−1 every minute until volitional fatigue. VO2 was 39.7, 42.9, 46.0, and 53.4 ml • kg−1 • min−1 at 18, 20, 22, and maximum speed (km • hr−1) on the TM. VO2 was significantly lower (p < .05) 31.5, 36.9, and 42.7 ml • kg−1 • min−1 at 18, 20, and 22 km • h−1 on-ice. The on-ice VO2max (54.7 ml • kg−1 • min−1) was similar to TM. Stride rate, stride length and heart rate (HR) were significantly different on-ice compared to TM. These results show that at submaximal velocities, VO2, HR, and stride rate are higher on TM compared to on-ice. VO2max was similar while HRmax was higher on the skating treadmill compared to on-ice. Keywords: VO2, ice hockey, stride kinetics, heart rate
Stroke Volume Response to Incremental Submaximal Exercise in Aerobically Trained, Active, and Sedentary Men
Authors: Boutcher Stephen H. , Mclaren Peter F. , Cotton Yvette , Boutcher Yati
Published: June 2009

Stroke volume response of trained cyclists (n = 10; Trained), active but untrained men (n = 10; Active), and sedentary men (n = 10; Sedentary) was determined by impedance cardiography during cycle ergometer exercise. For the Trained, at a heart rate of 90 beats • min−1, stroke volume increased by 27% compared to baseline levels, whereas stroke volume of Active and Sedentary groups did not significantly increase. Throughout exercise indices of ventricular emptying and filling of Trained were significantly greater than that of the other two groups whereas ventricular rates of the Active were significantly greater than those of the Sedentary. Throughout exercise cardiac contractility of the Trained was significantly greater than the other two groups. Results indicate that despite similar resting heart rate, stroke volume, and body mass, Trained compared to Active men significantly enhanced stroke volume, ventricular filling, and cardiac contractility during incremental ergometry exercise. Active compared to Sedentary men, however, displayed significantly larger stroke volume and ventricular filling rates during ergometry. We conclude that impedance cardiography indices of ventricular performance of aerobically trained men were superior to those of active, untrained men possessing similar resting stroke volume and heart rate. Furthermore, the ventricular performance of the active men possessing large resting stroke volume was superior to that of sedentary men. Keywords: ventricular function, aerobic training, impedance cardiography
Muscle Activation Is Enhanced With Multi- and Uni-Articular Bilateral Versus Unilateral Contractions
Authors: Behm David G. , Power Kevin E. , Drinkwater Eric J.
Published: June 2009

Ten resistance trained (RT) and 6 non-resistance trained (NRT) subjects were used to determine differences in quadriceps activation between isometric single and double knee extensions and squat contractions. Greater inactivation, as measured by the interpolated twitch technique, was recorded with single (RT: 16.5%, NRT: 17.6%) than double leg extensions (RT: 8.4%, NRT: 13.4%) or squats (RT: 4.03%, NRT: 1.7%). There was no significant difference between the maximum voluntary contraction (MVC) force of the dominant leg during single and double leg extensions. However, in NRT subjects, the contralateral or non-dominant leg during double leg extensions exhibited significantly less force than the dominant leg (715.9 vs 566.9 N). This deficit may be due to a lesser reliance on the non-dominant limb. The contractions of multiple lower body muscle groups enhanced the activation of the dominant quadriceps. Greater levels of activation may be necessary to cope with the stabilization necessary for bilateral and multi-articular contractions. Key words: interpolated twitch technique, quadriceps, leg extensions, squat, isometric, electromyography
The Influence of Exercise Test Protocol on Perceived Exertion at Submaximal Exercise Intensities in Children
Authors: Mahon Anthony D. , Plank David M. , Hipp Molly J.
Published: June 2009

This study examined ratings of perceived exertion (RPE) using Borg's 6-20 scale at 50 W, 80 W, and ventilatory threshold (VT) in 10-year-old children (n = 15) during two different graded exercise tests. Power output was increased by 10 W•min−1 in one protocol and by 30 W•3 min−1 in the other. The cardiorespiratory responses at VT and peak exercise were similar between protocols. At 50 W and 80 W the cardiorespiratory responses were generally lower (P < 0.05) in the 10-W trial. However, RPE was 11.5 ± 2.9 and 12.1 ± 3.2 at 50 W and 15.1 ± 2.7 and 15.3 ± 2.8 at 80 W in the 10-W and 30-W trials, respectively (P > 0.05). The RPE at VT was 13.9 ± 2.4 in the 10-W trial and 12.4 ± 2.4 in the 30-W trial (P < 0.05). In that variations in submaximal RPE did not coincide with variations in central mediators of exertion, locals cues of exertion may have provided the dominate sensory signal. Key words: ventilatory threshold, cardiorespiratory measures, exercise test, peak VO2, cycle ergometry, RPE
Childhood Obesity in Canada: A Review of Prevalence Estimates and Risk Factors for Cardiovascular Diseases and Type 2 Diabetes
Authors: Ball Geoff D.C. , McCargar Linda J.
Published: June 2009

Childhood obesity in Canada has become increasingly prevalent over the past 2 decades. Despite inconsistencies regarding different anthropometric indicators, cut-offs, and reference populations, both regional and national investigations have revealed high numbers of overweight and obese children and adolescents. A number of risk factors and health consequences have been associated with increased levels of body fatness in youth. Specifically, risk factors for cardiovascular diseases (CVD) and type 2 diabetes are known to develop early in life and tend to emerge in clusters among overweight youngsters. Unhealthy lifestyle behaviours (i.e., physical inactivity), a genetic disposition, and a centralized body fat distribution, all contribute to increased risk. In order to prevent future generations of children from experiencing increased morbidity and mortality as overweight and obese adults, coordinated efforts at all levels (family, school, community, and government) must be established with a long-term commitment to promote healthy nutrition and physical activity behaviours in our youth. Key words: obesity, body mass index, body fat distribution, risk factors, youth
Late Potentials in Female Triathletes Before and After Prolonged Strenuous Exercise
Authors: Warburton Darren E.R. , McGavock Jonathon , Welsh Robert C. , Haykowsky Mark J. , Quinney H. Arthur , Taylor Dylan , Dzavik Vladimir
Published: June 2009

The objectives of this study were to evaluate the prevalence of late potentials (LP) in female triathletes before and after prolonged strenuous exercise (PSE), and to determine whether LP are related to greater left ventricular (LV) dimensions and/or mass. Thirteen female triathletes were examined immediately before (Pre), one hour after (Post), and 24 to 48 hours after PSE (Recovery) using signal-averaged electrocardiography (SAECG). Late potentials were evaluated by two or more standard SAECG anomalies. Left ventricular dimensions and mass were measured Pre using two-dimensional echocardiography. Results revealed that no significant differences existed between Pre, Post, and Recovery in the SAECG parameters. Four athletes displayed LP during Pre. The incidence of LP during did not increase Post. There were no significant relationships between LV dimensions or mass and SAECG parameters. In conclusion, a small portion of female triathletes display LP before and after PSE, which are not worsened by PSE nor related to increased LV dimensions and/or mass. Keywords: signal-averaged electrocardiogram, triathlon, left ventricular dimensions, women
Influence of Regular Exercise on Age-Related Changes in Arterial Elasticity: Mechanistic Insights From Wall Compositions in Rat Aorta
Authors: Nosaka Toshiya , Tanaka Hirofumi , Watanabe Izumi , Sato Masaaki , Matsuda Mitsuo
Published: June 2009

Arterial stiffness increases with age in healthy sedentary adults. We previously reported that the age-related increases in arterial stiffness are absent or attenuated in regularly exercising adults. However, the mechanism underlying this training effect is unknown. One possibility is that regular exercise minimizes age-related changes in the arterial wall composition of elastin and collagen. To gain insight into this issue, we studied four groups of rats (N = 23): young (42-46 wks) and old (80-84 wks), sedentary and exercise-trained. The exercise group swam 1 hr•d−1, 6 d•wk−1 for 17-21 weeks. There was no significant difference in the incremental elastic modulus between young sedentary and exercise-trained rats. The elastic moduli of the old exercise-trained rats were 31% lower than in the old sedentary controls. As such, the magnitude of age-related increase in the elastic modulus was smaller in the exercise-trained (110%) vs. the sedentary group (151%) (p < 0.05). In both activity groups, elastin content was lower and collagen content was higher in old vs. young rats (p < 0.05). However, there were no significant differences between the two activity groups. These results are not consistent with the hypothesis that regular physical exercise minimizes age-related compositional changes in the arterial wall and attenuates the age-related increase in arterial stiffness. Key words: elastin, collagen, exercise training
Supervision of Occupational Fitness Assessments
Authors: Shephard Roy J. , Bonneau Jean
Published: June 2009

Controversy continues regarding an appropriate level of supervision for occupational fitness assessments. A bout of vigorous physical activity can augment the immediate risk of a cardiac catastrophe by a factor of 5-100 depending on age, cardiac risk factors, and the physical and emotional circumstances of the participant. However, if a person engages regularly in such activity, the immediate risk is more than offset by an improvement in prognosis during intervening periods of rest. During demanding physical work, there is a small but measurable risk of sudden death (3 to 7 episodes per 100,000 personnel per year). The risk associated with a brief (< 15 min) but vigorous occupational fitness assessment is so low as to preclude attempts to reduce it still further by direct medical supervision. If testing encourages an increase in personal fitness, any immediate increase in risk is enormously offset by a reduction in the number of cardiac deaths while resting. Furthermore, evidence is unconvincing that the average medical practitioner can prevent or treat any emergencies that may arise better than a well-trained professional fitness and lifestyle consultant (PFLC), a person certified by the Canadian Society for Exercise Physiology who has had frequent opportunities to practice the necessary skills. Since occupational fitness assessments are not diagnostic procedures, they appear to fall outside the jurisdiction of medical licensing bodies. In the absence of a history of cardiovascular disease, supervision of such assessments is safely and appropriately undertaken by the PFLC. Unnecessary insistence on medical supervision could preclude annual evaluation of occupational fitness and a resulting enhancement of physical condition, thus increasing rather than diminishing the risk to the worker. Key words: cardiac catastrophe, professional fitness and lifestyle consultant, medical delegation, medical supervision, sudden death
Tracking of Physical Fitness From Childhood to Adulthood
Authors: Trudeau François , Shephard Roy J. , Arsenault François , Laurencelle Louis
Published: June 2009

The purpose of the present study was to investigate the tracking of selected aspects of physical fitness (peak handgrip force, sit-ups, aerobic fitness, and blood pressure) from childhood to adulthood. The investigation studied a randomly selected subgroup from the original participants in the Trois-Rivières growth and development study, 95 women (57 experimental and 38 control) and 96 men (56 experimental and 40 control). During their primary-school education, the experimental group had received 5 hours of physical education each week whereas the control group had received 40 minutes per week. Data were gathered when subjects were 10-12 years old (baseline) and during follow-up around the age of 35 years. Tracking between 10, 11, 12, and 35 years of age was assessed by correlation analysis. In females the tracking of grip strength increased from the interval 10-35 to the intervals 11-35 and 12-35 years of age (r = 0.54 to 0.69 and 0.67, respectively, all p < 0.001). In males the tracking of grip strength was less consistent, but also increased over the same intervals to become significant for the correlation between 12 and 35 years of age (r = 0.32, p < 0.05). Tracking for sit-ups also increased, from 0.29 to 0.38 for females and from 0.23 to 0.54 for males. The tracking of PWC170/kg between 11 and 35 years was significant but low in females (r = 0.24) as well as in males (r = 0.34). The ability of childhood blood pressure to predict adult values was low in females (r = 0.24 for diastolic, ns; and r = 0.26 for systolic, p < 0.05) and absent in males. Presumably because some of the influence of the added physical education was lost by adulthood, the tracking of PWC170/kg and grip strength was weaker for experimental than for control subjects. In conclusion, data from the Trois-Rivières longitudinal study showed limited tracking of PWC170/kg and sit-ups in both sexes. The tracking of grip strength was moderately high in females but less consistent in males. This may reflect the larger influence of sex hormones on the muscle strength of males at puberty. Key words: fitness, physical education, blood pressure, longitudinal study
Prediction of Maximal Aerobic Power From the 20-m Multi-stage Shuttle Run Test
Authors: Stickland Michael K. , Petersen Stewart R. , Bouffard Marcel
Published: June 2009

The purpose of this study was to test the accuracy of the 20-m multi-stage shuttle run (SR) test to predict [Formula: see text] in young adults. [Formula: see text] was measured during a graded treadmill test in 60 men and 62 women (mean age 25.3 and 25.1 years, respectively). Each subject was familiarized with the SR procedure and then completed the SR test to predict [Formula: see text] on a separate day. The mean terminal SR stage was 9.5 for men and 7.8 for women. The regression equations of Léger et al. (1988) and Léger and Gadoury (1989) systematically underpredicted [Formula: see text]max for both males and females (p < 0.05). New regression equations were developed from present data to predict [Formula: see text] for males: Ŷ = 2.75X + 28.8 (r2 = 0.77, SEE = 4.07 ml•kg−1•min−1); and for females: Ŷ = 2.85X + 25.1 (r2 = 0.66, SEE = 3.64 ml•kg−1•min−1), where X equals the last half-stage of the SR completed. We suggest that these gender-distinct equations provide more accurate predictions of [Formula: see text] from the SR. Key words: aerobic fitness, maximal oxygen consumption, field test, test validity
Cardiovascular and Oxygen Uptake Kinetics During Sequential Heavy Cycling Exercises
Authors: Perrey Stéphane , Scott Jodie , Mourot Laurent , Rouillon Jean-Denis
Published: June 2009

The purpose of the present study was to assess the relationship between the rapidity of increased oxygen uptake [Formula: see text] and increased cardiac output (CO) during heavy exercise. Six subjects performed repeated bouts on a cycle ergometer above the ventilatory threshold (∼80% of peak [Formula: see text]) separated by 10-min recovery cycling at 35% peak [Formula: see text]. [Formula: see text] was determined breath-by-breath and CO was determined continuously by impedance cardiography. CO and [Formula: see text] values were significantly higher during the 2-min period preceding the second bout. The overall responses for [Formula: see text] and CO were significantly related and were faster during the second bout. Prior heavy exercise resulted in a significant increase in the amplitude of the fast component of [Formula: see text] with no change in the time constant and a decrease in the slow component. Under these circumstances, the amplitude of the fast component was more sensitive to prior heavy exercise than was the associated time constant. Key words: impedance cardiography, exercise transitions, cardiac output, prior exercise
Joint SOGC/CSEP Clinical Practice Guideline: Exercise in Pregnancy and the Postpartum Period
Authors: Davies Gregory A. L. , Wolfe Larry A. , Mottola Michelle F. , MacKinnon Catherine
Published: June 2009

Objective: To design Canadian guidelines advising obstetric care providers of the maternal, fetal, and neonatal implications of aerobic and strength-conditioning exercises in pregnancy. Outcomes: Knowledge of the impact of exercise on maternal, fetal, and neonatal morbidity, and of the maternal measures of fitness. Evidence: MEDLINE search from 1966 to 2002 for English-language articles related to studies of maternal aerobic and strength conditioning in a previously sedentary population, maternal aerobic and strength conditioning in a previously active population, impact of aerobic and strength conditioning on early and late pregnancy outcomes, impact of aerobic and strength conditioning on neonatal outcomes, as well as for review articles and meta-analyses related to exercise in pregnancy. Values: The evidence collected was reviewed by the Society of Obstetricians and Gynaecologists of Canada (SOGC Clinical Practice Obstetrics Committee) with representation from the Canadian Society for Exercise Physiology, and quantified using the evaluation of evidence guidelines developed by the Canadian Task Force on the Periodic Health Exam.Recommendations:1. All women without contraindications should be encouraged to participate in aerobic and strength-conditioning exercises as part of a healthy lifestyle during their pregnancy. (II-1,2B)2. Reasonable goals of aerobic conditioning in pregnancy should be to maintain a good fitness level throughout pregnancy without trying to reach peak fitness or train for an athletic competition. (II-1,2C)3. Women should choose activities that will minimize the risk of loss of balance and fetal trauma. (III-C)4. Women should be advised that adverse pregnancy or neonatal outcomes are not increased for exercising women. (II-1,2B)5. Initiation of pelvic floor exercises in the immediate postpartum period may reduce the risk of future urinary incontinence. (II-1C)6. Women should be advised that moderate exercise during lactation does not affect the quantity or composition of breast milk or impact infant growth. (I-A)Validation: This guideline has been approved by the SOGC Clinical Practice Obstetrics Committee, the Executive and Council of SOGC, and the Board of Directors of the Canadian Society for Exercise Physiology. Sponsors: This guideline has been jointly sponsored by the Society of Obstetricians and Gynaecologists of Canada and the Canadian Society for Exercise Physiology. Key words: fetus, neonate, outcomes, aerobic, strength
Evaluation of Anthropometric, Physiological, and Skill-Related Tests for Talent Identification in Female Field Hockey
Authors: Keogh Justin W.L. , Weber Clare L. , Dalton Carl T.
Published: June 2009

The purpose of the present study was to develop an effective testing battery for female field hockey by using anthropometric, physiological, and skill-related tests to distinguish between regional representative (Rep, n = 35) and local club level (Club, n = 39) female field hockey players. Rep players were significantly leaner and recorded faster times for the 10-m and 40-m sprints as well as the Illinois Agility Run (with and without dribbling a hockey ball). Rep players also had greater aerobic and lower body muscular power and were more accurate in the shooting accuracy test, p < 0.05. No significant differences between groups were evident for height, body mass, speed decrement in 6 × 40-m repeated sprints, handgrip strength, or pushing speed. These results indicate that %BF, sprinting speed, agility, dribbling control, aerobic and muscular power, and shooting accuracy can distinguish between female field hockey players of varying standards. Therefore talent identification programs for female field hockey should include assessments of these physical parameters. Key words: fitness profile, field testing, women, team sport
Neuromuscular Fatigue After a Ski Skating Marathon
Authors: Millet Guillaume Y. , Martin Vincent , Maffiuletti Nicola A. , Martin Alain
Published: June 2009

The aim of this study was to characterize neuromuscular fatigue in knee extensor muscles after a marathon skiing race (mean ± SD duration = 159.7 ± 17.9 min). During the 2 days preceding the event and immediately after, maximal percutaneous electrical stimulations (single twitch, 0.5-s tetanus at 20 and 80 Hz) were applied to the femoral nerve of 11 trained skiers. Superimposed twitches were also delivered during maximal voluntary contraction (MVC) to determine maximal voluntary activation (%VA). EMG was recorded from the vastus lateralis muscle. MVC decreased with fatigue from 171.7 ± 33.7 to 157.3 ± 35.2 Nm (-8.4%; p < 0.005) while %VA did not change significantly. The RMS measured during MVC and peak-to-peak amplitude of the compound muscle action potential (PPA) from the vastus lateralis decreased with fatigue by about 30% (p < 0.01), but RMS•PPA−1was similar before and after the ski marathon. Peak tetanus tension at 20 Hz and 80 Hz (P020 and P080, respectively) did not change significantly, but P020•P080−1 increased (p < 0.05) after the ski marathon. Data from electrically evoked single twitches showed greater peak mechanical response, faster rate of force development, and shorter contraction time in the fatigued state. From these results it can be concluded that a ski skating marathon (a) alters slightly but significantly maximal voluntary strength of the knee extensors without affecting central activation, and (b) induces both potentiation and fatigue. Key words: low- and high-frequency electrical stimulation, central activation, potentiation
Nitric Oxide and Physiologic Vasodilation in Human Limbs: Where Do We Go From Here?
Authors: Joyner Michael J. , Tschakovsky Michael E.
Published: June 2009

This brief review highlights human studies on the role of nitric oxide (NO) and limb vasodilation conducted at the Mayo Clinic over the last 10 years. These studies have attempted to determine whether NO is responsible for the "unexplained" limb vasodilation seen with body heating, limb ischemia, exercise, and mental stress. Our findings are placed in context with data from others, and possible future areas of study are identified. Key words: skin blood flow, reactive hyperemia, exercise hyperemia, mental stress
Prediction of Drafted-Triathlon Race Time From Submaximal Laboratory Testing in Elite Triathletes
Authors: Hue Olivier
Published: June 2009

Purpose and methods: To determine which physiological variables accurately predict the race time of an Olympic-distance International Triathlon undertaken in drafted conditions, 8 elite triathletes underwent both maximal and submaximal laboratory and field physiological testing: a 400-m maximal swim test; an incremental treadmill test; an incremental cycling test; 30 min of cycling followed by 20 min of running (C-R); and 20 min of control running (R) at the exact same speed variations as in running in C-R. Blood samples were drawn to measure venous lactate concentration after the 400-m swim and the cycle and run segments of C-R. During the maximal cycling and running exercises, data were collected using an automated breath-by-breath system. Results: The only parameters correlated with the overall drafted-triathlon time were lactate concentration noted at the end of the cycle segment (r = 0.83, p < 0. 05) and the distance covered during the running part of the submaximal C-R test (r = -0.92, p < 0.01). Stepwise multiple regression analysis revealed a highly significant (r = 0.96, p < 0.02) relationship between predicted race time (from laboratory measures) and actual race time, using the following calculation: Predicted Triathlon Time (s) = -1.128 (distance covered during R of C-R [m]) + 38.8 ([lactate] at the end of C in C-R) + 13,338. The high R2 value of 0.93 indicated that, taken together, these two laboratory measures could account for 93% of the variance in race times during a drafted triathlon. Conclusion: Complementing previous studies, this study demonstrates that different parameters seem to be reliable for predicting performance in drafted vs. nondrafted Olympic-triathlon races. It also demonstrates that, for elite triathletes competing in a drafted Olympic-distance triathlon, performance is accurately predicted from the results of submaximal laboratory measures. Key words: swimming, cycling, running, lactate, oxygen uptake
Prolonged Daytime Exercise Repeated Over 4 Days Increases Sleeping Heart Rate and Metabolic Rate
Authors: Mischler Isabelle , Vermorel Michel , Montaurier Christophe , Mounier Rémi , Pialoux Vincent , Péquignot Jean-Marc , Cottet-Emard Jean-Marie , Coudert Jean , Fellmann Nicole
Published: June 2009

The aim of this study was to determine the influence of prolonged exercise repeated for 4 days on sleeping heart rate (SHR) and metabolic rate (SMR). Eleven young untrained men exercised at moderate intensity 5 hrs daily for 4 days, alternately on a cycle ergometer (57.0 ± 1.3% [Formula: see text]) and a treadmill (64.7 ± 1.6% [Formula: see text]). They spent the night prior to the exercise period (control, C) and the 4 nights following exercise days (N1 to N4) in room calorimeters for the measurement of SHR, SMR, and respiratory quotient (RQ) from midnight until 6 a.m. Every morning, before the exercise bouts, plasma-free epinephrine (E) and norepinephrine (NE) levels were measured. After exercise, all SHR values were significantly higher than at C level (52 ± 1 bpm, p < 0.001) and the highest value was observed on N2 (61 ± 2 bpm). SMR increased by 11.2 ± 1.5% from C to N1, p < 0.001, and then plateaued up to N4, whereas RQ decreased from C (0.833 ± 0.009) to N2 (0.798 ± 0.005) and then plateaued. Plasma NE levels were higher the morning after each day of exercise and peaked on N2, whereas no significant variations were found for E. Variations of SHR between C and N2, and N3 and N4 were correlated with changes of SMR. No significant relationships were found between morning plasma NE, and either SMR or SHR variations. To conclude, prolonged exercise repeated for 4 days was associated with increases in SHR and SMR during the night following each day of exercise concomitantly with an enhanced lipid oxidation. The sustained stimulation of the sympathetic nervous system may be partly responsible for these effects. Key words: lipid oxidation, catecholamines, room calorimeter, endurance trial