Showing papers in "Applied Physiology, Nutrition, and Metabolism in 2008"
TL;DR: DXA-based analysis of fat and fat-free mass was performed in 50 cancer patients and compared with bioelectrical impedance analysis (BIA) and with regional computed tomography (CT) images available in the patients' medical records, finding CT presents great practical significance due to the prevalence of these images in patient diagnosis and follow-up.
Abstract: Human body composition is important in numerous cancer research domains. Our objective was to evaluate clinically accessible methods to achieve practical and precise measures of body composition in...
1,563 citations
TL;DR: The available literature that follows guidelines suggests that performance benefits can be seen with moderate amounts of caffeine, and these benefits are likely to occur across a range of sports, including endurance events, stop-and-go events, and sports involving sustained high-intensity activity lasting from 1-60 min.
Abstract: Athletes are among the groups of people who are interested in the effects of caffeine on endurance and exercise capacity. Although many studies have investigated the effect of caffeine ingestion on exercise, not all are suited to draw conclusions regarding caffeine and sports performance. Characteristics of studies that can better explore the issues of athletes include the use of well-trained subjects, conditions that reflect actual practices in sport, and exercise protocols that simulate real-life events. There is a scarcity of field-based studies and investigations involving elite performers. Researchers are encouraged to use statistical analyses that consider the magnitude of changes, and to establish whether these are meaningful to the outcome of sport. The available literature that follows such guidelines suggests that performance benefits can be seen with moderate amounts (~3 mg.kg-1 body mass) of caffeine. Furthermore, these benefits are likely to occur across a range of sports, including endurance events, stop-and-go events (e.g., team and racquet sports), and sports involving sustained high-intensity activity lasting from 1-60 min (e.g., swimming, rowing, and middle and distance running races). The direct effects on single events involving strength and power, such as lifts, throws, and sprints, are unclear. Further studies are needed to better elucidate the range of protocols (timing and amount of doses) that produce benefits and the range of sports to which these may apply. Individual responses, the politics of sport, and the effects of caffeine on other goals, such as sleep, hydration, and refuelling, also need to be considered.
370 citations
TL;DR: An RT program that is within a child's or adolescent's capacity and involves gradual progression under qualified instruction and supervision with appropriately sized equipment can involve more advanced or intense RT exercises, which can lead to functional and health benefits.
Abstract: Many position stands and review papers have refuted the myths associated with resistance training (RT) in chil- dren and adolescents. With proper training methods, RT for children and adolescents can be relatively safe and improve overall health. The objective of this position paper and review is to highlight research and provide recommendations in as- pects of RT that have not been extensively reported in the pediatric literature. In addition to the well-documented increases in muscular strength and endurance, RT has been used to improve function in pediatric patients with cystic fibrosis and cerebral palsy, as well as pediatric burn victims. Increases in children's muscular strength have been attributed primarily to neurological adaptations due to the disproportionately higher increase in muscle strength than in muscle size. Although most studies using anthropometric measures have not shown significant muscle hypertrophy in children, more sensitive measures such as magnetic resonance imaging and ultrasound have suggested hypertrophy may occur. There is no mini- mum age for RT for children. However, the training and instruction must be appropriate for children and adolescents, in- volving a proper warm-up, cool-down, and appropriate choice of exercises. It is recommended that low- to moderate- intensity resistance exercise should be done 2-3 times/week on non-consecutive days, with 1-2 sets initially, progressing to 4 sets of 8-15 repetitions for 8-12 exercises. These exercises can include more advanced movements such as Olympic- style lifting, plyometrics, and balance training, which can enhance strength, power, co-ordination, and balance. However, specific guidelines for these more advanced techniques need to be established for youth. In conclusion, an RT program that is within a child's or adolescent's capacity and involves gradual progression under qualified instruction and supervi- sion with appropriately sized equipment can involve more advanced or intense RT exercises, which can lead to functional (i.e., muscular strength, endurance, power, balance, and co-ordination) and health benefits.
305 citations
TL;DR: This study demonstrated that 18 h of repeated high-intensity exercise sessions over 6 weeks (3 d.week-1) is a powerful method to increase whole-body and skeletal muscle capacities to oxidize fat and carbohydrate in previously untrained individuals.
Abstract: High-intensity aerobic interval training (HIIT) is a compromise between time-consuming moderate-intensity training and sprint-interval training requiring all-out efforts. However, there are few dat...
284 citations
TL;DR: It is evident that a better understanding of the role of coffee in the development and prevention of T2D has the potential to uncover novel therapeutic targets and nutraceutical formulations for the disease.
Abstract: Epidemiological studies show coffee consumption to be correlated to large risk reductions in the prevalence of type 2 diabetes (T2D). Such correlations are seen with decaffeinated and caffeinated c...
156 citations
TL;DR: The purpose of this review is to introduce the reader to the major HSP families, the control of their expression, and some of their biologic functions, specifically with respect to the influence of exercise.
Abstract: Heat shock proteins (HSPs) are, in general, prosurvival molecules within the cellular environment, and the overexpression of even just 1 family of HSPs can lead to protection against and improvements after a variety of stressors. Not surprisingly, a fertile area of study has grown out of efforts to exploit the innate biologic behaviour of HSPs. Exercise, because of the inherent physiologic stresses associated with it, is but 1 stimulus that can result in a robust increase in various HSPs in several tissues, not the least of which happen to be the heart and skeletal muscle. The purpose of this review is to introduce the reader to the major HSP families, the control of their expression, and some of their biologic functions, specifically with respect to the influence of exercise. Moreover, as the first in a series of reviews from a common symposium, we will briefly introduce the concepts presented by the other authors, which include the effects of different exercise paradigms on skeletal muscle HSPs in the adult and aged systems, HSPs as regulators of inflammation, and the ion channel stabilizing effects of HSPs.
154 citations
TL;DR: There is a decline in skeletal muscle oxidative capacity with aging, due in part to mitochondrial dysfunction, which appears to play a particularly important role in extreme old age (senescence) where skeletal muscle VO2 max is observed to decline by approximately 50% even under conditions of similar oxygen delivery as young adult muscle.
Abstract: Aging is associated with a progressive decline in the capacity for physical activity. Central to this decline is a reduction in the maximal rate of oxygen utilization, or VO2 max. This critical perspective examines the roles played by the factors that determine the rate of muscle oxygen delivery versus those that determine the utilization of oxygen by muscle as a means of probing the reasons for VO2 max decline with aging. Reductions in muscle oxygen delivery, principally due to reduced cardiac output and perhaps also a maldistribution of cardiac output, appear to play the dominant role up until late middle age. On the other hand, there is a decline in skeletal muscle oxidative capacity with aging, due in part to mitochondrial dysfunction, which appears to play a particularly important role in extreme old age (senescence) where skeletal muscle VO2 max is observed to decline by approximately 50% even under conditions of similar oxygen delivery as young adult muscle. It is noteworthy that at least the struc...
153 citations
TL;DR: It is clear from the data discussed that regular resistance training can effectively disturb processes that contribute to the progression of aging as it pertains to the mitochondrial theory.
Abstract: Skeletal muscle aging is associated with a significant loss of muscle mass, strength, function, and quality of life. In addition, the healthcare cost of aging and age-related disease is growing, an...
148 citations
TL;DR: The ergogenic effects of caffeine during endurance activity are mediated partly by enhanced contractile force and partly by a reduction in perceived exertion, possibly though a blunting of effort and (or) pain.
Abstract: The ergogenic effect of caffeine on endurance exercise performance is multifactorial; however, there is evidence for an effect on both the central nervous system and the excitation–contraction coupling of skeletal muscle. The increase in exercise performance seen following intracerebroventrical caffeine injection in rats provides strong evidence for a central ergogenic effect. The central ergogenic effect is not likely related to the ability of caffeine to promote wakefulness, but could be due to an increase in the pain and effort perception threshold. There is no evidence that caffeine alters peripheral nerve conduction velocity or neuromuscular transmission, and 1 study showed that motor unit synchronization was not altered by caffeine. Studies have also shown that caffeine can have a direct effect on skeletal muscle that could be ergogenic. For example, patients with high cervical spinal cord lesions showed improvements in stimulated contractile force during cycling, in spite of the fact that they have...
147 citations
TL;DR: The KL and the AG are moderately priced accelerometers that provide researchers and clinicians with accurate estimates of step counts and activity EE at most walking and running speeds.
Abstract: Accelerometer-based activity monitors are commonly used by researchers and clinicians to assess physical activity. Recently, the Kenz Lifecorder EX (KL) and ActiGraph GT1M (AG) accelerometers have been made commercially available, but there is limited research on the validity of these devices. Therefore, we sought to validate step count, activity energy expenditure (EE), and total EE output from the KL and AG during treadmill walking and running. Ten male and 10 female participants performed 10 min treadmill walking and running trials, at speeds of 54, 80, 107, 134, 161, and 188 m.min-1. Step counts were hand tallied by 2 observers, and indirect calorimetry was used to validate the accelerometers' estimates of EE. AG total EE was calculated using the Freedson equation. Analysis of variance (ANOVA) and Pearson's correlations were used to analyze the data. At the slowest walking speed, the AG and KL counted 64% +/- 15% and 92% +/- 6% of the observed steps, respectively. At all other treadmill speeds, both activity monitors undercounted, compared with observed steps, by < or =3%. The KL underestimated activity EE at faster running speeds (p < 0.01), overestimated total EE at some walking speeds, and underestimated total EE at some running speeds (p < 0.01). The Freedson equation inaccurately measured total EE at most walking and running speeds. The KL and the AG are moderately priced accelerometers that provide researchers and clinicians with accurate estimates of step counts and activity EE at most walking and running speeds.
143 citations
TL;DR: Parents perceived that there are various intrapersonal, interpersonal, and environmental barriers to supporting healthy eating and physical activity among their children and program planners and health professionals can consider these barriers when developing interventions to promote healthy bodyweights among preschoolers.
Abstract: There is an increasing trend in childhood obesity in Canada and many preschool children are overweight or obese. The objective of this study was to explore parents’ experiences and challenges in supporting healthy eating and physical activity among their preschool children. A qualitative descriptive study involving 5 focus groups was conducted. A convenience sample of 39 parents from 3 childcare centres in Hamilton, Ontario, participated. Parents were English speaking and had a child aged 2–5 years attending the childcare centre for at least 3 months. The research team read transcripts of the audio-taped sessions and used a constant comparison approach to develop themes, which involved coding comments by continually referring to previously coded comments for comparison. The social ecological model was used to organize the themes into 3 higher-level categories: (i) intrapersonal (individual): preschoolers’ preferences and health; (ii) interpersonal (interactions): parents’ and others’ different views and p...
TL;DR: At 48 h post-EIMD, milk and milk-based protein-CHO supplementation resulted in the attenuation of decreases in isokinetic muscle performance and increases in CK and Mb.
Abstract: Exercise-induced muscle damage (EIMD) leads to the degradation of protein structures within the muscle. This may subsequently lead to decrements in muscle performance and increases in intramuscular enzymes and delayed-onset muscle soreness (DOMS). Milk, which provides protein and carbohydrate (CHO), may lead to the attenuation of protein degradation and (or) an increase in protein synthesis that would limit the consequential effects of EIMD. This study examined the effects of acute milk and milk-based protein–CHO (CHO-P) supplementation on attenuating EIMD. Four independent groups of 6 healthy males consumed water (CON), CHO sports drink, milk-based CHO-P or milk (M), post EIMD. DOMS, isokinetic muscle performance, creatine kinase (CK), and myoglobin (Mb) were assessed immediately before and 24 and 48 h after EIMD. DOMS was not significantly different (p > 0.05) between groups at any time point. Peak torque (dominant) was significantly higher (p < 0.05) 48 h after CHO-P compared with CHO and CON, and M co...
TL;DR: The currently available evidence on coffee and risk of cardiovascular diseases and cancer is largely reassuring, and suggests that, for the general population, addressing other health-related behaviors has priority for the prevention of chronic diseases.
Abstract: Numerous epidemiological studies have evaluated the association between coffee consumption and risk of type 2 diabetes, coronary heart disease, and various cancers. This paper briefly reviews the e...
Journal Article•
TL;DR: The differences appear to suggest thermoregulatory inferiority, but no epidemiological data show higher heat-injury rates in children, even during heat waves, and it is suggested that children employ a different thermoreGulatory strategy.
Abstract: The review revisits some child–adult differences relevant to thermoregulation and offers alternatives to accepted interpretations. Morphologically, children have a higher body surface area to mass ...
TL;DR: The Jamar handgrip dynamometer shows more consistency than the Biodex hand grip attachment in ACPs, and should therefore be the preferred measure of changes in strength over time.
Abstract: Important deteriorations in body composition and strength occur and need to be accurately measured in advanced cancer patients (ACPs). The aim of this study was to establish the relationship betwee...
TL;DR: A brief review explores the interactions between cortisol and DHEA and their effects on immune function in aging, as well as potential methods to combat the endocrine-related contribution to immunosenescence, including D HEA supplementation and exercise.
Abstract: A decline in the human immune system that occurs with aging is known as immunosenescence. Several factors are involved in the process, including reduced neutrophil function and cytotoxic capacity o...
TL;DR: There is very little evidence to support the hypothesis that caffeine has ergogenic effects as a result of enhanced fat oxidation, and there is growing evidence that this could be explained by common genetic variations.
Abstract: Caffeine, an adenosine receptor antagonist, has been studied for decades as a putative ergogenic aid. In the past 2 decades, the information has overwhelmingly demonstrated that it indeed is a powe...
TL;DR: The fitness profile for a professional NHL ice-hockey team exhibited increases in player size and anaerobic and aerobic fitness parameters over a 26 year period that differed by position, however, this evolution of physiological profile did not necessarily translate into team success in this particular NHL franchise.
Abstract: The primary purpose of this investigation was to examine the physiological profile of a National Hockey League (NHL) team over a period of 26 years. All measurements were made at a similar time of ...
TL;DR: 6 weeks of strength training combining weight lifting and plyometric exercises results in significant improvement of kicking performance, as well as other physical capacities related to success in football (soccer).
Abstract: The effects of a training program consisting of weight lifting combined with plyometric exercises on kicking performance, myosin heavy-chain composition (vastus lateralis), physical fitness, and body composition (using dual-energy X-ray absorptiometry (DXA)) was examined in 37 male physical education students divided randomly into a training group (TG: 16 subjects) and a control group (CG: 21 subjects). The TG followed 6 weeks of combined weight lifting and plyometric exercises. In all subjects, tests were performed to measure their maximal angular speed of the knee during instep kicks on a stationary ball. Additional tests for muscle power (vertical jump), running speed (30 m running test), anaerobic capacity (Wingate and 300 m running tests), and aerobic power (20 m shuttle run tests) were also performed. Training resulted in muscle hypertrophy (+4.3%), increased peak angular velocity of the knee during kicking (+13.6%), increased percentage of myosin heavy-chain (MHC) type IIa (+8.4%), increased 1 repe...
TL;DR: Despite previous data demonstrating potent antioxidant actions of quercetin in vitro, this study indicates that this effect is absent in vivo and that chronic quercETin ingestion does not exert protection from exercise-induced oxidative stress and inflammation.
Abstract: Quercetin is a flavonoid compound that has been demonstrated to be a potent antioxidant in vitro. The objective of this study was to evaluate if quercetin ingestion would increase plasma antioxidan...
TL;DR: An effective role in glucose regulation is suggested for this structured low-intensity walking program for women with gestational diabetes mellitus.
Abstract: Exercise prescriptions that can be translated into clinical recommendations are clearly needed for women with gestational diabetes mellitus (GDM). A pilot project was developed to document the effectiveness of a structured low- intensity walking protocol on capillary glucose control in GDM women. Ten GDM women followed conventional manage- ment of diet and insulin therapy, plus a low-intensity walking program (W) from diagnosis to delivery. Capillary glucose concentrations, insulin requirements, and pregnancy outcomes were compared with a matched cohort by body mass index (BMI), age, and insulin usage (20 GDM women who followed conventional management alone (C)). Baseline capillary glucose concentrations were not significantly different between the W and C groups. The W group had an average acute drop in capillary glucose concentration from pre- to post-exercise of 2.0 mmolL -1 . In addition, the W group had signifi- cantly lower mean glucose concentrations in the fasted state and 1 h after meals than the C group in the week prior to de- livery. These lower glucose concentrations were achieved while requiring fewer units of insulin per day (C, 0.50 ± 0.37 Ukg -1 ; W, 0.16 ± 0.13 Ukg -1 ; p < 0.05), injected less frequently. These results suggest an effective role in glucose regulation for this structured walking program.
TL;DR: An emerging approach to the study of alcohol consumption in populations is to consider both the volume and pattern of consumption as they relate to mortality and disease burden.
Abstract: Dietary ethanol (alcohol) is the most widely consumed drug worldwide. High levels of mortality, morbidity, and social malaise are associated with abuse of alcohol, and increasing numbers of women a...
TL;DR: A nutritive effect of post-exercise protein content was not discernible short term, but a delayed performance benefit was observed following protein-enriched high-carbohydrate ingestion.
Abstract: Nutrition is an important aspect of recuperation for athletes during multi-day competition or hard training. Post-exercise carbohydrate is likely to improve recovery, but the effect of protein is equivocal. The objective of this study was to determine the effect of post-exercise dietary protein content imposed over a high-carbohydrate background on subsequent performance. Using a crossover design, 12 cyclists completed 3 high-intensity rides over 4 days. Day 1 comprised 2.5 h intervals, followed by repeat-sprint performance tests on days 2 (15 h post) and 4 (60 h post), interspersed with a rest day. During 4 h recovery on days 1 and 2, cyclists ingested either 1.4 g·kg–1·h–1 carbohydrate, 0.7 g·kg–1·h–1 protein and 0.26 g·kg–1·h–1 fat (protein-enriched) or 2.1 g·kg–1·h–1 carbohydrate, 0.1 g·kg–1·h–1 protein, and equal fat (control). At other times, cyclists ingested a standardized high-carbohydrate diet. Anabolism was gauged indirectly by nitrogen balance, stress and inflammation via cortisol and cytokine...
TL;DR: It is speculated that optimal targeting of PGC-1alpha upregulation, whether by diet, exercise, or a combination of both, could represent effective prophylactic or therapeutic means to improve insulin sensitivity.
Abstract: The discovery 10 years ago of PGC-1alpha represented a major milestone towards understanding of the molecular processes regulating energy metabolism in many tissues, including skeletal muscle. PGC-1alpha orchestrates a metabolic program regulating oxidative lipid metabolism and insulin sensitivity. This is essentially the same metabolic program that is activated by exercise and down-regulated by sedentary lifestyles and high-fat diets, as well as in cases of obesity and type 2 diabetes. The present review examines the evidence in support of the key role for PGC-1alpha regulation of substrate metabolism and mitochondrial biogenesis in skeletal muscle. Surprisingly, studies with PGC-1alpha null and transgenic mice have revealed unexpected pathologies when PGC-1alpha is completely repressed (KO animals) or is massively overexpressed. In contrast, PGC-1alpha overexpression within normal physiological limits results in marked improvements in fatty acid oxidation and insulin-stimulated glucose transport. Exercise, sedentary lifestyles, and nutritional factors can regulate PGC-1alpha expression. We speculate that optimal targeting of PGC-1alpha upregulation, whether by diet, exercise, or a combination of both, could represent effective prophylactic or therapeutic means to improve insulin sensitivity. Indeed, using modern molecular tools, it may indeed be possible to prescribe optimally individualized nutrition and exercise programs.
TL;DR: Exercise and allopurinol alone increased the levels of most of the oxidative stress markers measured in plasma, erythrocytes, and gastrocnemius muscle, and provoked a marked reduction in physical performance.
Abstract: The aim of this study was to examine the effect of allopurinol, a xanthine oxidase inhibitor, on oxidative stress and physical performance after swimming until exhaustion in rats. Blood and gastroc...
TL;DR: It is concluded that a moderate dose of ibuprofen ingested after repeated resistance training sessions does not impair muscle hypertrophy or strength and does not affect ratings of muscle soreness.
Abstract: High doses of ibuprofen have been shown to inhibit muscle protein synthesis after a bout of resistance exercise. We determined the effect of a moderate dose of ibuprofen (400 mg·d–1) consumed on a ...
TL;DR: The relationship between HR and VO2 remains strong, but the two are not equivalent in this population group, so THR zones equivalent to 20%-39%VO2 reserve were developed and validated based on the strongest relationship.
Abstract: Validated target heart rate (THR) zones for exercise prescription for overweight and obese pregnant women have not been developed The purposes of this study were to determine if heart rate reserve
TL;DR: Short-term treatment with metformin has statistically significant, but physiologically subtle, effects that reduce key outcomes related to maximal exercise capacity Whether this small but consistent effect is manifested in people with insulin resistance or diabetes who already have some degree of mitochondrial dysfunction remains to be determined.
Abstract: Individually, exercise and the drug metformin have been shown to prevent or delay type 2 diabetes. Metformin mildly inhibits complex I of the electron transport system and may impact aerobic capacity in people exercising while taking metformin. The purpose of the study was to evaluate the effects of metformin on maximal aerobic capacity in healthy individuals without mitochondrial dysfunction. Seventeen healthy, normal-weight men (n=11) and women (n=6) participated in a double-blind, placebo-controlled, cross-over design. Peak aerobic capacity was measured twice using a continuous, incrementally graded protocol; once after 7-9 d of metformin (final dose=2000 mg/d) and once with placebo, with 1 week between tests. The order of the conditions was counterbalanced. Peak oxygen uptake (VO2 peak), heart rate (HR), ventilation (VE), respiratory exchange ratio (RER), rating of perceived exertion (RPE), and test duration were compared across conditions using paired t tests with the R statistical program. VO2 peak (-2.7%), peak heart rate (-2.0%), peak ventilation (-6.2%), peak RER (-3.0%), and exercise duration (-4.1%) were all reduced slightly, but significantly, with metformin (all p<0.05). There was no effect of metformin on RPE or ventilatory breakpoint. Correlations between the decrement in VO2 peak and any of the other outcome variables were weak (r2<0.20) and not significant. Short-term treatment with metformin has statistically significant, but physiologically subtle, effects that reduce key outcomes related to maximal exercise capacity. Whether this small but consistent effect is manifested in people with insulin resistance or diabetes who already have some degree of mitochondrial dysfunction remains to be determined.
TL;DR: Examination of pre-practice hydration, on-ice fluid intake, and sweat and sodium losses of Canada's junior men's hockey team found that elite junior hockey players incurred large sweat and Sodium losses during an intense practice, but 2/3 of players drank enough to minimize body mass loss.
Abstract: Previous research in many sports suggests that losing ~1%-2% body mass through sweating impairs athletic performance. Elite-level hockey involves high-intensity bursts of skating, arena temperatures are >10 degrees C, and players wear protective equipment, all of which promote sweating. This study examined the pre-practice hydration, on-ice fluid intake, and sweat and sodium losses of 44 candidates for Canada's junior men's hockey team (mean +/- SE age, 18.4 +/- 0.1 y; height, 184.8 +/- 0.9 cm; mass, 89.9 +/- 1.1 kg). Players were studied in groups of 10-12 during 4 intense 1 h practices (13.9 degrees C, 66% relative humidity) on 1 day. Hydration status was estimated by measuring urine specific gravity (USG). Sweat rate was calculated from body mass changes and fluid intake. Sweat sodium concentration ([Na]) was analyzed in forehead sweat patch samples and used with sweat rate to estimate sodium loss. Over 50% of players began practice mildly hypohydrated (USG > 1.020). Sweat rate during practice was 1.8 +/- 0.1 L.h(-1) and players replaced 58% (1.0 +/- 0.1 L.h(-1)) of the sweat lost. Body mass loss averaged 0.8% +/- 0.1%, but 1/3 of players lost more than 1%. Sweat [Na] was 54.2 +/- 2.4 mmol.L(-1) and sodium loss averaged 2.26 +/- 0.17 g during practice. Players drank only water during practice and replaced no sodium. In summary, elite junior hockey players incurred large sweat and sodium losses during an intense practice, but 2/3 of players drank enough to minimize body mass loss. However, 1/3 of players lost more than 1% body mass despite ready access to fluid and numerous drinking opportunities from the coaches.