bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Heat Removal Through the Hand on Metabolism and Performance During Cycling Exercise in the Heat
Authors: Hsu Andrew R. , Hagobian Todd A. , Jacobs Kevin A. , Attallah Hamdee , Friedlander Anne L.
Published: June 2009

Objective: This two-part study tested the hypotheses that the use of a new cooling device, purported to extract heat from the body core through the palm of the hand, would (a) attenuate core temperature rise during submaximal exercise in the heat, thereby suppressing exercise-associated metabolic changes, and (b) facilitate a higher sustained workload, thus shortening the completion time of a time-trial performance test. Methods: In Study 1, 8 male triathletes (age 27.9 ± 2.0 yrs, mass 77.2 ± 3.1 kg, [Formula: see text]Peak 59.0 ± 4.1 ml•min−1•kg−1) cycled for 1 hr at the same absolute workload (∼60% [Formula: see text]peak) in a heated room (31.9 ± 0.1 °C, 24 ±1% humidity) on two occasions counterbalanced for cooling (C) or noncooling (NC). In Study 2, 8 similar subjects (age 26.9 ± 2.0 yrs, mass 75.2 ± 3.7 kg, [Formula: see text]peak 54.1 ± 3.1 ml•min−1•kg−1) performed two 30-km cycling time-trial performance tests under the same conditions (CTNCT). Results: In Study 1, cooling attenuated the rise in tympanic temperature (TTY) (1.2 ± 0.2 vs. 1.8 ± 0.2 °C; p <  0.01) and lowered mean oxygen consumption ([Formula: see text] 2.4 ± 0.1 vs. 2.7 ± 0.1 L•min−1; p <  0.05) and blood lactate (1.7 ± 0.2 vs. 2.2 ± 0.2 mmol. L−1; p <  0.01) during exercise. There were no significant differences in respiratory exchange ratio (RER), blood glucose, heart rate (HR), face temperature (TF), or back temperature (TB) between NC and C. In Study 2, time to complete 30 km was 6 ± 1% less with cooling than without cooling (60.9 ± 2.0 vs. 64.9 ± 2.6 min; p <  0.01). During the last 20% of CT, subjects sustained a workload that was 14 ± 5% (p = 0.06) higher than NCTat the same TTYand HR. Conclusions: Heat extraction through the hand during cycle ergometer exercise in the heat can (a) lower TTY, lactate concentration, and [Formula: see text] during a submaximal set-workload test and (b) reduce the time it takes to complete a 30-km time-trial test. Key words: core temperature, hyperthermia, thermoregulation, hand-cooling
Achievement of Peak During a 90-s Maximal Intensity Cycle Sprint in Adolescents
Authors: Williams Craig A. , Ratel Sébastien , Armstrong Neil
Published: June 2009

The aim of this study was to determine whether peak oxygen uptake [Formula: see text] attained in a 90-s maximal intensity cycle sprint is comparable to that from a conventional ramp test. Sixteen participants (13 boys and 3 girls, 14.6 ± 0.4 yr) volunteered for the study. On Day 1 they completed a [Formula: see text] test to exhaustion using a 25 W∙min−1 ramp protocol beginning at 50 W. Peak [Formula: see text] was defined as the highest [Formula: see text] value achieved, and aerobic power [Formula: see text] as the power output of the final 30 s. On Day 2 the participants completed two 90-s maximal sprints (S1 and S2). A 45-min recovery period separated each sprint. Mean oxygen uptake over the last 10 s of each sprint was determined as [Formula: see text] and minimum power (MinP-30 s) as the mechanical power attained in the final 30 s. A one-way ANOVA was used to analyse differences between S1, S2, and the ramp test for [Formula: see text] and MinP-30 s. Peak [Formula: see text] was not significantly different between the ramp, S1, or S2 (2.64 ± 0.5, 2.49 ± 0.5, and 2.53 ± 0.5 L∙min−1, respectively, p > 0.68). The S1 and S2 [Formula: see text] scores represented 91 ± 10% and 92 ± 10% of the ramp aerobic test. The MinP-30 s for S1 and S2 were significantly lower than the [Formula: see text] of the ramp test, p < 0.05. Hence, for researchers solely interested in [Formula: see text] values, a shorter but more intensive protocol provides an alternative method to the traditional ramp aerobic test. Key words: aerobic, anaerobic, mechanical power, pedaling
The Effects of Moderate, Strenuous, and Overtraining on Oxidative Stress Markers and DNA Repair in Rat Liver
Authors: Ogonovszky Helga , Sasvári Maria , Dosek Agoston , Berkes István , Kaneko Takao , Tahara Shoichi , Nakamoto Hideko , Goto Sataro , Radák Zsolt
Published: June 2009

Physical exercise above a certain load has been suggested as being a cause of oxidative stress. We have tested whether training with moderate (MT), strenuous (ST), or over (OT) load can cause alterations in the activities of antioxidant enzymes, lipid peroxidation, protein oxidation, DNA damage, or activity of 8-oxoG-DNA glycosylase (OGG1) in rat liver. The levels of corticosterone decreased in all exercising groups but the differences were not significant. Adrenocorticotrophin hormone (ACTH) levels decreased, not significantly, in MT and OT compared to C. Activity levels of antioxidant enzymes did not change significantly in the liver. The levels of reactive carbonyl derivative (RCD) content decreased in the liver of exercising animals, and the differences reached significance between control and moderately trained groups. The changes in the levels of lipid peroxidation (LIPOX) were not significant, but were lower in the exercised groups. The 8-hydroxydeoxyguanosine (8-OHdG) levels increased in the OT group, and the activity of OGG1 measured from crude cell extracts tended to increase in MT and ST. The findings of this study imply that overtraining induces oxidative damage to nuclear DNA, but not to liver lipids and proteins. Key words: exercise, oxidative damage, adaptation, OGG1
Effects of Eccentric Exercise on Cycling Efficiency
Authors: Moysi Joaquin Sanchis , Garcia-Romero Jerónimo Carmelo , Alvero-Cruz José Ramón , Vicente-Rodriguez Germán , Ara Ignacio , Dorado Cecillia , Calbet José A.L.
Published: June 2009

The aim of this study was to find out whether the efficiency of concentric muscle contraction is impaired by eccentric squatting exercise. The study involved 25 male physical education students in two experiments. In the first experiment 14 subjects undertook cycling exercise at 65% [Formula: see text]max until exhaustion on two occasions. During the experimental condition their cycling was interrupted every 10 min so they could perform eccentric squatting exercise, whereas in the control condition they rested seated on the bike during the interruptions. Eccentric squatting consisted of 10 series of 25 reps with a load equivalent to 150% of the subject's body mass on the shoulders. During the first experiment gross efficiency decreased (mean ± SE) from 17.1 ± 0.3 to 16.0 ± 0.4%, and from 17.2 ± 0.3 to 16.5 ± 0.4%, between the 2nd and 9th cycling bouts of the experimental and control conditions, respectively (both p <  0.05). The reduction in cycling efficiency was similar in both conditions (p = 0.10). Blood lactate concentration [La] was higher during the experimental than in the control condition (p <  0.05), but substrate oxidation was similar. MVC was decreased similarly (25-28%) in both conditions. The 11 subjects participating in the second experiment undertook 25 reps of eccentric squatting exercise only, each with a load equivalent to 95% of his maximal voluntary contraction (MVC), repeated every 3 min until exhaustion. One hour after the end of the eccentric squatting exercise series cycling, [Formula: see text] and gross cycling efficiency were comparable to the values observed before the eccentric exercise. Both experimental protocols with eccentric exercise elicited similar muscle soreness 2 days later; however, at this time cycling efficiency was similar to that observed prior to eccentric exercise. The interposition of cycling exercise between the eccentric exercise bouts accelerated the recovery of MVC. We conclude that eccentric exercise does not alter or has only a marginal effect on gross cycling efficiency even in presence of marked muscle soreness. Key words: performance, fatigue, muscle soreness, lactate, triathlon
Mobilization of Glucose From the Liver During Exercise and Replenishment Afterward
Authors: Pencek R. Richard , Fueger Patrick T. , Camacho Raul C. , Wasserman David H.
Published: June 2009

The liver is anatomically well situated to regulate blood glucose. It is positioned downstream from the pancreas, which releases the key regulatory hormones glucagon and insulin. It is also just downstream from the gut, permitting efficient extraction of ingested glucose and preventing large excursions in systemic glucose after a glucose-rich meal. The position of the liver is not as well situated from the standpoint of experimentation and clinical assessment, as its primary blood supply is impossible to access in conscious human subjects. Over the last 20 years, to study hepatic glucose metabolism during and after exercise, we have utilized a conscious dog model which permits sampling of the blood that perfuses (portal vein, artery) and drains (hepatic vein) the liver. Our work has demonstrated the key role of exercise-induced changes in glucagon and insulin in stimulating hepatic glycogenolysis and gluconeogenesis during exercise. Recently we showed that portal venous infusion of the pharmacological agent 5'-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside leads to a marked increase in hepatic glucose production. Based on this, we propose that the concentration of AMP may be a component of a physiological pathway for stimulating hepatic glucose production during exercise. Insulin-stimulated hepatic glucose uptake is increased following exercise by an undefined mechanism that is independent of liver glycogen content. The fate of glucose taken up by the liver is critically dependent on hepatic glycogen stores, however, as glycogen deposition is greatly facilitated by prior glycogen depletion. Key words: pancreas, carbohydrate, feeding, exertion, AICAR
The Effect of Sweetness on the Efficacy of Carbohydrate Supplementation During Exercise in the Heat
Authors: Carter James , Jeukendrup Asker E. , Jones David A.
Published: June 2009

The aim of the present study was to investigate potential mechanisms responsible for the improvement in prolonged exercise capacity in hot environments with exogenous carbohydrate. Eight endurance-trained men ([Formula: see text]60.5 ± 2.4 ml kg−1•min−1, mean ± SE) cycled to exhaustion on three occasions at 60% [Formula: see text] at an ambient temperature of 35 °C. They ingested either a sweet 6.4% carbohydrate solution (SC), a nonsweet 6.4% carbohydrate solution (NSC), or water (W). Exercise capacity was significantly increased with SC and NSC compared to W, the improvements corresponding to 15.8% and 11.8%, respectively. No difference in exercise capacity was seen between SC and NSC solutions. Plasma glucose concentrations were higher during the SC and NSC trials compared to W, significantly so at 10 min and at fatigue. Rates of carbohydrate oxidation were higher in the SC and NSC trials, although the rates never declined below 2.1 ± 0.2 g•min−1 in the W trial. There was no difference in the rate of rise of rectal temperature between trials, but there was a trend for subjects to fatigue at higher temperatures during the two carbohydrate trials. In conclusion, exogenous carbohydrate, independent of sweetness, improves exercise capacity in the heat compared to water alone. Key words: cycling, thermoregulation, maltodextrin
Chronic But Not Acute Oral L-Arginine Supplementation Delays the Ventilatory Threshold During Exercise in Heart Failure Patients
Authors: Doutreleau Stéphane , Mettauer Bertrand , Piquard François , Schaefer Adrien , Lonsdorfer Evelyne , Richard Ruddy , Geny Bernard
Published: June 2009

The purpose of this study was to determine, in heart failure patients (HF), whether acute or chronic L-arginine supplementation (LAS) might delay the ventilatory threshold (VT) and whether chronic LAS might reduce exercise-induced plasma lactate increase. HF patients undertook 4 cardiopulmonary bicycle exercises tests. The first 3 were maximal without (EX1), after acute (EX2), or chronic (EX3) oral LAS (6 gm twice a day for 6 weeks). The 4th test (EX4), performed after chronic LAS, was similar to the first in order to investigate the effect of chronic LAS on circulating lactate levels. Results showed that acute LAS failed to improve both submaximal and maximal exercise capacities. Similarly, maximal exercise capacity remained unmodified after chronic LAS. Nevertheless, chronic LAS delayed significantly the patients' ventilatory threshold. Thus exercise duration prior to VT increased (mean ± SEM) from 6.04 ± 0.9 to 7.7 ± 1.03 min (p = 0.04), resulting in a significant increase in oxygen uptake (1.05 ± 0.08 to 1.24 ± 0.12 L•min−1; p = 0.03), CO2 release (0.94 ± 0.10 to 1.2 ± 0.12 L•min−1; p = 0.018), minute ventilation (29.31 ± 2.8 to 34.5 ± 2.7 L; p = 0.009), and workload (60.7 ± 9.8 to 78.5 ± 10.2 watts; p = 0.034). Furthermore, chronic LAS significantly reduced the exercise-induced increase in postexercise plasma lactate concentration (−21 ± 7%). In conclusion, unlike acute supplementation, chronic LAS significantly delays the ventilatory threshold, and chronic LAS reduces circulating plasma lactate in HF patients. These data suggest that chronic LAS might improve the ability of HF patients to perform their daily-life activities. Key words: maximal exercise, heart device, vasodilator
Maximizing Acute Fat Utilization: Effects of Exercise, Food, and Individual Characteristics
Authors: Bennard Patrick , Imbeault Pascal , Doucet Éric
Published: June 2009

In discussion of the physiological mechanisms that regulate fat metabolism, and with consideration of the metabolic stimuli that modulate substrate metabolism, the issue of how an acute state of negative lipid balance can be maximized is addressed. The regulation of lipolysis by catecholamines and insulin is reviewed, and the mechanisms of fatty acid mobilization and uptake by muscle are also briefly discussed. The implications of substrate availability and the hormonal response during physiological states such as fasting, exercise, and after food intake are also addressed, with particular regard to the influences on fatty acid mobilization and/or oxidation from eliciting these stimuli conjointly. Finally, a brief discussion is given of both the nature of exercise and the exercising individual, and how these factors influence fat metabolism during exercise. It is also a primary thrust of this paper to underline gaps in the existing literature with regard to exercise timing concerning food ingestion for maximizing acute lipid utilization. Key words: lipid balance, catecholamines, insulin, exercise, glycemic index
Effect of Endurance Training on Different Mechanical Efficiency Indices During Submaximal Cycling in Subjects Unaccustomed to Cycling
Authors: Hintzy Frédérique , Mourot Laurent , Perrey Stéphane , Tordi Nicolas
Published: June 2009

The purpose of this study was to evaluate different efficiency indices, i.e., gross (GE: no baseline correction), net (NE: resting metabolism as baseline correction), and work (WE: unloaded exercise as baseline correction), to reveal the effect of endurance training on mechanical efficiency. Nine healthy sedentary women undertook an incremental test and submaximal cycling exercise, at an intensity corresponding to 50% of the pretraining peak oxygen uptake, before and after 6 weeks of endurance training (18 sessions of 45 min). The training effects on efficiency indices were tested by comparisons based on GE, NE, and WE as well as by the differences between the percentage changes of all indices (% GE, % NE, % WE). Endurance training resulted in significantly higher GE (+ 11.1%; p <  0.001) and NE (+ 9.1%; P <  0.01). Only minor significant improvement (+ 2.4%; p <  0.05) was observed with the WE index because the value used for baseline subtraction was significantly reduced by the training sessions, due perhaps to improvement in pedaling skill. As a consequence, % WE was significantly lower than % GE (p <  0.01) and % NE (p <  0.05), while % GE and % NE were not significantly different. We conclude that mechanical efficiency of cycling increases with training in women previously unfamiliar with cycling, and that the WE index is less sensitive to this training effect than GE and NE indices. Key words: gross efficiency, net efficiency, work efficiency, internal work, cycle ergometer
Attenuation of Protective Effect Against Eccentric Exercise-Induced Muscle Damage
Authors: Nosaka Kazunori , Newton Michael J. , Sacco Paul
Published: June 2009

A single bout of eccentric exercise confers a long-lasting protective effect against subsequent bouts of the same exercise. This study investigated how the protective effect was lessened when the interval between the initial and secondary exercise bouts was increased from 4 to 12 weeks. Thirty young men performed two bouts of 12 maximal eccentric actions of the elbow flexors of the nondominant arm separated by either 4 (n = 9), 8 (n = 10), or 12 (n = 11) weeks. Maximal isometric strength, flexed and relaxed elbow joint angles, range of motion, upper arm circumference, muscle soreness, plasma creatine kinase (CK), and myoglobin (Mb) were measured before, immediately after, and for 4 days after exercise. Changes in criterion measures were compared between bouts for each group and among groups by two-way repeated-measures ANOVA. There were no significant differences among groups in the changes in all measures following the first bout. Significantly (p <  0.05) smaller responses in all measures were observed after the second bout as compared with first bout for the 4 and 8 weeks, but only in strength, muscle soreness, CK, and Mb for the 12 weeks. It was concluded that some aspects of the protective effect were attenuated after 8 weeks, and the factors responsible for the effect vary among the measures. Key words: maximal isometric strength, creatine kinase, myoglobin, range of motion, muscle soreness
Blood Flow to Exercising Limbs Varies With Age, Gender, and Training Status
Authors: Koch Dennis W. , Newcomer Sean C. , Proctor David N.
Published: June 2009

Understanding the effects of physiological aging on blood flow to active skeletal muscle and its regulation during exercise has important functional, hemodynamic, and metabolic implications for our rapidly expanding elderly population. During peak exercise involving a large muscle mass, blood flow to the legs is lower in healthy older compared to younger persons; this results from central (reduced cardiac output) and peripheral (reduced leg vascular conductance) limitations. There is considerable variability in the literature concerning age-related changes in leg blood flow during submaximal exercise, with reports of similar or reduced leg blood flaw and vascular conductance in older vs. younger subjects depending on the exercise intensity and the gender and training status of the subjects. However, all the studies involving non-endurance-trained subjects are consistent in that older subjects achieve the requisite leg blood flow at higher arterial perfusion pressures than young subjects, suggesting altered local vasoregulatory mechanisms with aging. Although the nature of these age- related alterations is poorly understood, we have preliminary evidence for augmented sympathetic vasoconstrictor responsiveness in the legs of older men during exercise, and blunted leg vasodilator responsiveness in older women. Systematic research will be needed in order to define the central and local mechanisms underlying these age- and gender-specific differences in muscle vascular responsiveness. Such information will be important for designing future interventions aimed at improving muscle blood supply and functional capacity in older persons. Key words: exercise, vascular responsiveness, human
Muscle Hypertrophy Models: Applications for Research on Aging
Authors: Alway Stephen E. , Siu Parco M. , Murlasits Zsolt , Butler David C.
Published: June 2009

Muscle hypertrophy is an adaptive response to overload that requires increasing gene transcription and synthesis of muscle-specific proteins resulting in increased protein accumulation. Progressive resistance training (PRT) is thought to be among the best means for achieving hypertrophy in humans. However, hypertrophy and functional adaptations to PRTin the muscles of humans are often difficult to evaluate because adaptations can take weeks, months, or even years before they become evident, and there is a large variability in response to PRTamong humans. In contrast, various animal models have been developed which quickly result in extensive muscle hypertrophy. Several such models allow precise control of the loading parameters and records of muscle activation and performance throughout overload. Scientists using animal models of muscle hypertrophy should be familiar with the advantages and disadvantages of each and thereby choose the model that best addresses their research question. The purposes of this paper are to review animal models currently being used in basic research laboratories, discuss the hypertrophic and functional outcomes as well as applications of these models to aging, and highlight a few mechanisms involved in regulating hypertrophy as a result of applying these animal models to questions in research on aging. Key words: overload-induced growth, muscle strength, apoptosis, contraction
Age and Sex Differences in Blood Lactate Response to Sprint Running in Elite Master Athletes
Authors: Korhonen Marko T. , Suominen Harri , Mero Antti
Published: June 2009

The effect of age and sex on anaerobic glycolytic capacity in master athletes is currently unclear. To study this issue, we determined blood lactate concentrations after competitive sprint running in male and female master athletes of different age. Eighty-one men (40-88 yrs) and 75 women (35-87 yrs) participating in the sprint events (100-m, 200-m, 400-m) in the European Veterans Athletics Championships were studied. Blood samples were taken from the fingertip and analysed for peak lactate concentration ([La]bpeak). The [La]bpeak following 100-m to 400-m races showed a curvilinear decline (p <  0.001-0.05) with age in both men and women. However, the age related differences in the [La]bpeak were not significant before 70 years of age. No significant sex related differences were found in [La]bpeak for any sprint event. The [La]bpeak correlated significantly (p <  0.001-0.05) with running times in all sprint distances except for the age-controlled correlation in men for the 100-m and 200-m. In conclusion, the present study showed age but not sex differences in blood lactate response to competitive sprint running in master athletes. Although the [La]bpeak level of the athletes was considerably higher than that reported for untrained men and women, these cross-sectional findings suggest that anaerobic energy production from glycolysis declines in later years and may be a factor in the deterioration in sprint performance. Key words: aging, anaerobic metabolism, exercise performance
Pedometer-Determined Step Count Guidelines for Classifying Walking Intensity in a Young Ostensibly Healthy Population
Authors: Tudor-Locke Catrine , Sisson Susan B. , Collova Tracy , Lee Sarah M. , Swan Pamela D.
Published: June 2009

Purpose: (a) To establish pedometer steps/min intensity categories (i.e., light, moderate, hard, very hard) for adults under controlled conditions, and (b) use these cut-points to ascertain the number of steps expected in 30 minutes of moderate intensity activity. Methods: 25 men and 25 women, ages 18-39 years, performed 6-min exercise bouts at 3 treadmill speeds (4.8, 6.4, and 9.7 km/hr). Yamax SW-200 pedometers indicated steps, and steady-state [Formula: see text] was recorded. METs were calculated by dividing steady-state [Formula: see text] by 3.5 ml•kg−1min−1. Linear regression was used to quantify the relationships between steps/min and METs across all speeds. Ten participants (5 M, 5 F) were randomly selected from the original 50 and constituted a holdout sample for cross-validation purposes (i.e, comparing actual and predicted METs; paired t-test). Results: The regression equation for males was: METs = −7.065 + (0.105*steps/min) r2 = 0.803. For females it was: METs = −8.805 + (0.110*steps/min) r2 = 0.830. Cross-validation was confirmed. Conclusions: Pedometer cut-points corresponding to minimal moderate intensity walking were 96 steps/min in men and 107 steps/min in women, or roughly 100 steps/min for both. This translates to approximately 3,000 steps in 30 min of moderate-intensity ambulatory activity for both genders. Key words: exercise, outcome assessment, motion sensor
Performing Triple and Quadruple Figure Skating Jumps: Implications for Training
Authors: King Deborah L.
Published: June 2009

The purpose of this paper is to review the biomechanics of triple and quadruple figure skating jumps, focusing on information that has implications for strength and conditioning programs. At a minimum, to complete the required revolutions in a jump, a skater must balance the average angular velocity with the time in the air. Vertical velocity at takeoff is similar in high revolution jumps to that in low revolution jumps; however, when comparing skaters of different abilities, those with higher abilities generate greater vertical velocities at takeoff for the same type of jump. Powerful extension of the legs is the primary factor in generating vertical velocity. Some jumps use asymmetrical extension of both legs, while other jumps involve extension of only one leg. Angular velocity is controlled primarily by the skater's moment of inertia, which means skaters must forcefully arrest the motion of the arms and legs after the propulsion phase and then quickly position the arms and legs close to the axis of rotation during flight. Training exercises that emphasize eccentric and concentric muscle actions and which are adaptable to asymmetrical or unilateral motions, such as box jumps and medicine ball throws, are a crucial component to off-ice training programs for figure skaters. Key words: ice skating, biomechanics, power, technique, strength, conditioning
Lifestyle Modifications to Prevent and Manage Hypertension for Exercise Physiologists and Fitness Professionals
Authors: Jamnik Veronica K. , Gledhill Norman , Touyz Rhian M. , Campbell Norman R.C. , Logan Alexander G. , Padwal Raj , Petrella Rob
Published: June 2009

Information tailored to the interest of exercise physiologists and fitness professionals is provided regarding the Canadian Hypertension Society's 2005 evidence-based recommendations on lifestyle modifications for the prevention and management of hypertension. The evidence from randomized controlled (RC) trials and systematic reviews of RC trials published in peer reviewed journals was reviewed by subject matter experts and then appraised independently by content and methodology experts. Blood pressure lowering was accepted as a primary outcome. All recommendations were debated and then voted on by the 43 members of the Canadian Hypertension Education Program's Evidence-Based Recommendations Task Force and achieved at least 95% consensus. Lifestyle modifications to prevent and/or manage hypertension include: (1) perform 30-60 minutes of aerobic exercise on 4-7 days of the week; (2) maintain a healthy body weight (BMI 18.5-24.9 kg/m2) and waist circumference (<  102 cm for men and <  88 cm for women); (3) limit alcohol consumption to no more than 14 standard drinks per week in men or 9 standard drinks per week in women; (4) follow a diet that emphasizes fruits, vegetables, and low-fat dairy products and which is reduced in fat and cholesterol (DASH diet); (5) restrict salt intake; and (6) consider stress management in selected individuals. Key words: blood pressure, lifestyle interventions, physical activity, body weight, diet
Facteurs Limitants de la Performance en Triathlon
Authors: Margaritis Irène
Published: June 2009

Triathlon is a multievent sport (swimming, cycling, running). Long duration triathlons can induce physiological stress that can be modulated by environmental conditions. Certain factors promote performance, others limit it. A minimal level of maximal oxygen uptake is required, but it does not always determine the performance. For triathletes, the low hematocrit values do not reflect anemia and therefore do not limit performance. The appearance of clinical signs of dehydratation and of digestive impairment may limit performance. The performance in swimming does not play the most important role in triathlon performance, but the physiological conditions in which the first transition is made can limit performance in the two following events; this is also the case for the second transition. Triathlon races cause muscle damage whose signs persist several days. Given the hormonal responses and the indices of muscle damage, it appears necessary to rest at least 5 days to avoid overtraining. It is difficult to define precisely how much one should train for each of the three events. However, it can be concluded that triathlon training has to be taken as a whole. Key words: training, endurance, recovery, triathlete
Determination of Accumulated O2 Deficit in Exhaustive Short-Duration Exercise
Authors: Hill David W.
Published: June 2009

Usually, an initial step in determining accumulated O2 deficit is the estimation of the O2 demand of high intensity exercise by extrapolation from [Formula: see text] measured during steady-state submaximal exercise. It was hypothesized that O2 deficit could be determined without the need to estimate O2 demand by extrapolation. Ten women performed all-out cycle ergometer exercise tests at each of four power outputs selected so that exhaustion would occur after 90 to 600 s. Power output (W), accumulated VO2 (ml), and time to exhaustion (s) were measured in each test and then fit to the following equation: O2 deficit (ml) = O2 demand (ml∙min−1∙W−1)∙time (min)∙power (W) - accumulated VO2 (ml). This procedure generated values for two parameters (O2 demand and O2 deficit) for each subject. The O2 deficit was also calculated for each individual using conventional methods. The values for O2 deficit obtained using the two methods were correlated (r =.96, p <.01), and the value obtained using the experimental method tended to be larger, t(9) = 2.15, p =.06. It is concluded that O2 demand and O2 deficit can be determined from the results of several high-intensity tests without the need to extrapolate from submaximal exercise to estimate the O2 demands of supramaximal exercise. Key words: anaerobic, anaerobic capacity
Metabolic Response of Forearm Muscle to Graded Exercise in Type II Diabetes Mellitus: Effect of Endurance Training
Authors: DeVries Deborah A. , Marsh Gregory D. , Thompson R. Terry , Rodger N. Wilson
Published: June 2009

In this study, 31P nuclear magnetic resonance spectroscopy was used to monitor muscle metabolism in Type II diabetic subjects (n = 10) during an incremental exercise test. Also the exercise responses of diabetic subjects (n = 4) following submaximal endurance training were assessed and compared to healthy controls (n = 5). Responses to incremental exercise in the diabetic subjects were consistent over time despite minor fluctuations in metabolic control. In the diabetic and control groups, after 12 weeks of training the forearm flexor muscles, power output at the intracellular threshold of acidosis (IT) increased (p <.01) similarly: T0 versus T12: 0.90 ± 0.09 versus 1.20 ± 0.13 and 1.03 ± 0.07 versus 1.22 ± 0.10 W, respectively. Minimum intracellular pH reached at peak exercise was unchanged after training. The control group, however, became more acidic versus the diabetic group (p <.05) in response to progressive exercise. This difference was maintained over time. Endurance training elicited similar adaptations in forearm muscles of Type II diabetic and control subjects, although there were differences between the two groups in intracellular pH during exercise. Key words: magnetic resonance spectroscopy, muscle metabolism, exercise
Design and Evaluation of a Modified Underwater Cycle Ergometer
Authors: Chen An A. , Kenny Glen P. , Johnston Chad E. , Giesbrecht Gordon G.
Published: June 2009

An underwater cycle ergometer was designed consisting of an aluminum cycle frame in water connected with a 1:1 gear ratio to a mechanically braked standard cycle ergometer supported above the water. Three progressive maximal exercise tests were performed (n = 10): (a) the underwater ergometer in water (UEW), (b) underwater ergometer in air (UEA), and (c) a standard cycle ergometer in air (SEA). At submaximal power outputs, oxygen consumption [Formula: see text] and heart rate (HR) were generally lower in the SEA condition (p <.05), indicating that exercise in the upright position was more efficient. Exercise in water (UEW) resulted in lower total exercise duration, maximal HR, and maximal Tes than in air conditions. The upright position (SEA) resulted in greater total exercise duration and maximal power output than the semirecumbent positions. Because of positional differences between the standard and underwater ergometers, air-water comparisons should be made by using the underwater ergometer in water and on land. Key words: core temperature, esophageal temperature, skin temperature, exercise, resistance, work, power output, heat balance, heat loss, heat production, thermoregulation
Seated Versus Standing Cycling in Competitive Road Cyclists: Uphill Climbing and Maximal Oxygen Uptake
Authors: Tanaka Hirofumi , Bassett Jr. David R. , Best Shane K. , Baker Jr. Kenny R.
Published: June 2009

Seven competitive road cyclists (M ± SE = 23.7 ± 1.5 yr, 70.5 ± 1.7 kg) participated to determine the effects of cycling body position on physiological responses during uphill cycling and maximal oxygen uptake [Formula: see text]. There was no significant difference in [Formula: see text] between seated and standing positions on a cycle ergometer (66.4 ± 1.6 vs. 66.4 ± 1.7 ml∙kg−1∙min−1). When the subjects rode their own bicycle on a treadmill, oxygen uptake and heart rate were significantly (p < 0.05) higher during standing when subjects bicycled at 20.0 km∙h−1 (4% grade), but no difference was observed when riding at 12.3 km−1 (10% grade). Leg RPE was significantly (p < 0.05) lower for standing position up a 10% grade. The results suggest that the standing position is less economical during moderate hill climbing, but during steep hill climbing, it results in a decreased sensation of effort in the legs. Key words: bicycling, heart rate, rating of perceived exertion
The Influence of Age and Cardiorespiratory Fitness on Kinetics of Oxygen Uptake
Authors: Chilibeck Philip D. , Paterson Donald H. , Petrella Robert J. , Cunningham David A.
Published: June 2009

The purpose of this study was to determine the influences of ageing and cardiorespiratory fitness on kinetics of VO2 during the transition to exercise of moderate intensity. Subjects performed three transitions to and from a 6-minute square wave constant load, at an intensity corresponding to 90% of ventilatory threshold (VET), to determine VO2 kinetics. The young group had a significantly faster time constant of VO2 (τVO2). τVO2 was significantly correlated with VO2max for both young and old groups; however, the slope of the τVO2 - VO2max regression equation was steeper for the old group, indicating that fit older subjects had VO2 kinetics that approached those of fit young. A multiple linear regression indicated that relative fitness was the strongest significant predictor of τVO2, followed by sex and age. Although VO2 kinetics are definitely slowed with age, relative levels of cardiorespiratory fitness also have a great influence on the dynamic response of VO2. Key words: VO2max, ventilatory threshold, heart rate kinetics
Augmented Hyperventilation Via Normoxic Helium Breathing Does Not Prevent Exercise-Induced Hypoxemia
Authors: Buono Michael J. , Maly Richard
Published: June 2009

The purpose of this study was to determine if augmented hyperventilation produced via normoxic helium breathing would reduce exercise-induced hypoxemia (EIH). Seven highly trained endurance athletes with a mean maximum oxygen uptake of 65 ml∙kg−1∙min−1, performed two cycle ergometer tests to volitional exhaustion. During one of the tests the subjects breathed ambient air, while during the other they breathed normoxic helium (21% O2, 79% He). Mean maximum expired ventilation significantly (p <.05) increased from 139 L∙min−1 during the ambient trial to 168 L∙min−1 while breathing normoxic helium. Mean arterial oxygen saturation obtained at maximum exercise, however, was not significantly different for the two trials (ambient = 90%, helium = 89%). These results suggest that significantly augmenting exercise hyperventilation by 21% essentially had no effect on EIH in endurance athletes. Thus, the data do not support the hypothesis that inadequate hyperventilation is an important mechanism for arterial oxygen desaturation during graded exercise to exhaustion in highly trained individuals. Key words: arterial oxygen saturation, endurance athletes, maximal exercise
Epinephrine Infusion Does Not Enhance Net Muscle Glycogenolysis During Prolonged Aerobic Exercise
Authors: Wendling Paula S. , Peters Sandra J. , Spriet Lawrence L. , Heigenhauser George J. F.
Published: June 2009

The role of physiological elevations of plasma epinephrine concentration on muscle glycogenolysis during prolonged exercise was investigated. Eight healthy volunteers cycled for 90 min at 65% VO2max on two occasions; once with an infusion of epinephrine (EPI) and once without (control). Biopsy samples were taken from the vastus lateralis muscle both prior to and following exercise for the analysis of muscle glycogen. EPI infusion significantly elevated venous plasma EPI ~2.5-fold over control values throughout exercise (90 min: 5.78 ± 0.95 vs. 2.35 ± 0.49 nM). EPI infusion did not significantly alter net glycogenolysis as compared to control (310.0 ± 30.8 vs. 299.5 ± 41.1 mmol glucosyl units/kg dry mass). Venous concentrations of plasma FFA and whole blood glycerol were unaffected by EPI infusion. Whole blood glucose was significantly elevated during EPI infusion at 10, 30, 60 and 90 min of exercise compared to control values. Whole blood lactate was elevated to a greater extent during EPI infusion as compared to control at 10, 30, and 60 min of exercise. In conclusion, EPI infusion had no effect on muscle glycogenolysis and appeared to have little effect on adipose tissue lipolysis. The explanation for the elevation of blood lactate is unknown while the elevation in blood glucose suggests that EPI infusion potentiated liver glycogenolysis. Key words: muscle metabolism, plasma catecholamines, blood lactate, lipolysis, blood glucose
Weight and Plyometric Training: Effects on Eccentric and Concentric Force Production
Authors: Wilson Greg J. , Murphy Aron J. , Giorgi Anthony
Published: June 2009

The study was performed in an effort to gain greater insights into the adaptations invoked by plyometric and weight training. Forty-one previously trained males were randomly allocated in either a control, plyometric, or weight-training group. The experimental groups trained for 8 weeks, performing either heavy lifts or dynamic plyometric exercises. The following test items were performed prior to and at the completion of the training period: (a) vertical jump, (b) a series of isoinertial concentric and eccentric tests, (c) push-up tests, and (d) maximal bench press and squat lifts. Plyometric training significantly enhanced the rate of eccentric lower body force production. The weight-training group primarily enhanced concentric function. These results were attributed to the specific stresses imposed by the differing forms of training and are discussed with reference to methods of enhancing training induced adaptations and the types of movements such training would tend to facilitate. Key words: rate of force development, isoinertial assessment, stretch-shorten cycle performance
Role of Calcium-Activated Neutral Protease (Calpain) With Diet and Exercise
Authors: Belcastro Angelo N. , Albisser Tracie A. , Littlejohn Brent
Published: June 2009

Although the proteolytic events accompanying acute and chronic perturbations in striated muscle protein turnover remain to be fully elucidated, the purpose of this paper is to (a) review the chemistry of the nonlysosomal calpain-calpastatin system, and (b) provide evidence for the involvement of a nonlysosomal, calcium-activated neutral protease (calpain) in the response of skeletal muscle protein breakdown to altered nutritional status (diet composition; energy restriction) and increased periods of contractile activity (exercise). In reviewing the literature, it is apparent that calpain is involved in the protein catabolism which accompanies alterations in diet composition and/or energy restriction. The precise mechanism of calpain action remains to be elucidated; however, the role of altered metabolic status contributing to calcium imbalances is discussed relative to increasing protein degradation. Hypotheses for further investigation are provided in regard to identifying the targeting of selected proteins (and organelles) for degradation by calpain. Key words: preteolysis, muscle, protein degredation
Energy Cost and Stride Duration Variability at Preferred Transition Gait Speed Between Walking and Running
Authors: Brisswalter Jeanick , Mottet Denis
Published: June 2009

The aim of this study was to explore the relationship between energy cost of locomotion and stride duration variability in the region of the walk-run transition speed. Ten subjects participated in this experiment during four treadmill sessions. The first session was used to habituate subjects to treadmill walking or running. During the second session the treadmill speed was increased from 6 km∙h−1to 10 km∙h−1in steps of 0.2 km∙h−1to determine the freely chosen transition speed between walking and running (ST). The last two sessions consisted of five walks or five runs conducted at five intensities selected to represent respectively ST−1 km∙h−1; ST−0.5 km∙h−1; ST; ST + 0.5 km∙h−1; and ST + 1 km∙h−1. Exhaled gases were collected during the last two sessions, and stride duration was continuously recorded. The results indicated a significant increase in stride duration variability before ST for the freely chosen gait condition only. These findings point to an alternative hypothesis to that classically proposed to describe a transition as an energy saving mechanism. Key words: variability, locomotion, energy cost, transition speed
A New Measurement of Tissue Capillarity: The Capillary-to-Fibre Perimeter Exchange Index
Authors: Hepple Russell T.
Published: June 2009

The surface area of contact between capillaries and muscle fibres has been suggested to be the site of greatest oxygen flux density in the movement of oxygen from the capillaries to the muscle fibres. A new measurement of tissue capillarity, designed specifically for use on non-perfusion fixed muscle tissue (i.e., that obtained via needle biopsy) is presented that describes the capillary supply from this perspective. The Capillary-to-Fibre Perimeter Exchange Index (the CFPE Index) is derived as the quotient of the individual capillary-to-fibre ratio (i.e., the capillary-to-fibre ratio calculated for each fibre individually) and the fibre perimeter. This method is suggested to provide a means of quantitating potential alterations in the capacity for oxygen flux (e.g., as may occur in response to a training intervention) and any carrier- or receptor-mediated aspect of blood-tissue exchange between the capillaries and muscle fibres (e.g., insulin or glucose delivery). Key words: capillary supply, muscle fibres, oxygen flux, training, diabetes
The Ventilatory Response to Hypoxia Below the Carbon Dioxide Threshold
Authors: Rapanos Theodore , Duffin James
Published: June 2009

The ventilatory response to acute progressive hypoxia below the carbon dioxide threshold using rebreathing was investigated. Nine subjects rebreathed after 5 min of hyperventilation to lower carbon dioxide stores. The rebreathing bag initially contained enough carbon dioxide to equilibrate alveolar and arterial partial pressures of carbon dioxide to the lowered mixed venous partial pressure (≈ 30 mmHg), and enough oxygen to establish a chosen end-tidal partial pressure (50-70 mmHg), within one circulation time. During rebreathing, end-tidal partial pressure of carbon dioxide increased while end-tidal partial pressure of oxygen fell. Ventilation increased linearly with end-tidal carbon dioxide above a mean end-tidal partial pressure threshold of 39 ± 2.7 mmHg. Below this peripheral-chemoreflex threshold, ventilation did not increase, despite a progressive fall in end-tidal oxygen partial pressure to a mean of 37 ± 4.1 mmHg. In Conclusion, hypoxia does not stimulate ventilation when carbon dioxide is below its peripheral-chemoreflex threshold. Key words: peripheral chemoreflex, rebreathing technique, hyperventilation
Effects of 5-Day Exercise Training in Elderly Subjects on Resting Left Ventricular Diastolic Function and VO2max
Authors: Petrella Robert J. , Cunningham Donald A. , Paterson David H.
Published: June 2009

We evaluated the effects of short-term, high-intensity exercise training and detraining on resting left ventricular diastolic function (LVDF) and maximal aerobic power (VO2max) in 7 sedentary older (age = 68 ± 4 years) men (n = 5) and women (n = 2). Training consisted of cycling for 60 min with power output set at 70% (Day 1), 80% (Day 2), and 90% (Days 3-5) of the pretraining peak work rate. Detraining consisted of a return to regular exercise habits. LVDF increased 10% in the early (E) flow velocity, decreased 18% in the late (A) flow velocity wave, and decreased 31% in the isovolumic relaxation time. VO2max was increased 12% while plasma volume (PV) increased 10% following, training and returned to baseline after detraining. The exercise-induced change in VO2max was directly related to the change in E/A (r =.52) and indirectly related to the change in IVRT (r = −.62). It was concluded that short-term, high-intensity exercise training improves LVDF and is tolerated well in older subjects, and that the calculated changes in PV and aerobic power are similar to those observed previously in a younger population. Key words: aging, training, cardiac filling
Interactions Between Sleep, Other Body Rhythms, Immune Responses, and Exercise
Authors: Shephard Roy J. , Shek Pang N.
Published: June 2009

Biological rhythms can influence both exercise tolerance and immune function. Most studies have focussed upon circadian rhythms, but some circaseptan, circatrigintan, and circannual cycles have also been described. Rhythms may have an endogenous or an exogenous basis. Endogenous rhythms originate in the cells of the suprachiasmatic nucleus. Impulses from this region pass to the pineal gland, where they regulate the production of melatonin, a compound that modulates the sleep/wakefulness cycle. Endocrine, physiological, and psychological parameters all show evidence of periodicity. Most components of the immune system, both cellular and humoral, also show large rhythmic changes. It is not yet clear how far such periodicity is secondary to changes in other body systems. Nevertheless, the magnitude of variation is such that it is vital to obtain experimental and control data at identical time points in both acute and chronic studies of exercise and immune function. Disturbance of the sleep/wakefulness cycle can constitute a form of stress, with adverse consequence for immune function. Key words: circadian rhythms, cytokines, hormones, hypothalamus, leukocytes, melatonin