Showing papers on "Exercise physiology published in 2008"
TL;DR: Given the markedly lower training volume in the SIT group, these data suggest that high‐intensity interval training is a time‐efficient strategy to increase skeletal muscle oxidative capacity and induce specific metabolic adaptations during exercise that are comparable to traditional ET.
Abstract: Low-volume ‘sprint’ interval training (SIT) stimulates rapid improvements in muscle oxidative capacity that are comparable to levels reached following traditional endurance training (ET) but no study has examined metabolic adaptations during exercise after these different training strategies. We hypothesized that SIT and ET would induce similar adaptations in markers of skeletal muscle carbohydrate (CHO) and lipid metabolism and metabolic control during exercise despite large differences in training volume and time commitment. Active but untrained subjects (23 ± 1 years) performed a constant-load cycling challenge (1 h at 65% of peak oxygen uptake ( ˙ VO2peak) before and after 6 weeks of either SIT or ET (n = 5 men and 5 women per group). SIT consisted of four to six repeats of a 30 s ‘all out’ Wingate Test (mean power output ∼500 W) with 4.5 min recovery between repeats, 3 days per week. ET consisted of 40‐60 min of continuous cycling at a workload that elicited ∼65% ˙ VO2peak (mean power output ∼150 W) per day, 5 days per week. Weekly time commitment (∼1.5 versus ∼4.5 h) and total training volume (∼225 versus ∼2250 kJ week −1 ) were substantially lower in SIT versus ET. Despite these differences, both protocols induced similar increases (P < 0.05) in mitochondrial markers for skeletal muscle CHO (pyruvate dehydrogenase E1α protein content) and lipid oxidation (3-hydroxyacyl CoA dehydrogenase maximal activity) and protein content of peroxisome proliferator-activated receptor-γ coactivator-1α. Glycogen and phosphocreatine utilization during exercise were reduced after training, and calculated rates of whole-body CHO and lipid oxidation were decreased and increased, respectively, with no differences between groups (all main effects, P < 0.05). Given the markedly lower training volume in the SIT group, these data suggest that high-intensity interval training is a time-efficient strategy to increase skeletal muscle oxidative capacity and induce specific metabolic adaptations during exercise that are comparable to traditional ET.
1,151 citations
TL;DR: It is proposed that the risk of adverse outcomes, such as functional limitation and mortality, is better estimated by considering jointly obesity and muscle strength rather than Obesity and muscle mass and the term ‘sarcopenic obesity’ should be revisited.
Abstract: Purpose of the review
Older obese persons with decreased muscle mass or strength are at special risk for adverse outcomes. We discuss potential pathways to muscle impairment in obese individuals and the consequences that joint obesity and muscle impairment may have on health and disability. Tantamount to this discussion is whether low muscle mass or, rather, muscle weakness should be used for the definition.
899 citations
TL;DR: High-intensity interval training is a potent time-efficient strategy to induce numerous metabolic adaptations usually associated with traditional endurance training and alter metabolic control during aerobic-based exercise.
Abstract: High-intensity interval training (HIT) is a potent time-efficient strategy to induce numerous metabolic adaptations usually associated with traditional endurance training. As little as six sessions of HIT over 2 wk or a total of only approximately 15 min of very intense exercise (approximately 600 kJ), can increase skeletal muscle oxidative capacity and endurance performance and alter metabolic control during aerobic-based exercise.
665 citations
TL;DR: The vulnerability of the body to oxidative stress and diseases is significantly enhanced in a sedentary compared to a physically active lifestyle, which means that the well-known beneficial effects of exercise are due to the capability of exercise to produce increased levels of ROS.
544 citations
TL;DR: The cortisol findings support the view that moderate to high intensity exercise provokes increases in circulating cortisol levels, but, once corrections for plasma volume reduction occurred and circadian factors were examined, low intensity exercise actually resulted in a reduction in circulate cortisol levels.
Abstract: This study examined the influence of exercise intensity upon the cortisol response of the hypothalamic-pituitary-adrenal (HPA) axis. Specifically, we examined exercise at intensities of 40, 60, and 80% maximal oxygen uptake (VO2max) in an attempt to determine the intensity necessary to provoke an increase in circulating cortisol. Twelve active moderately trained men performed 30 min of exercise at intensities of 40, 60, and 80% of their VO2max, as well as a 30-min resting-control session involving no exercise on separate days. Confounding factors such as time of day--circadian rhythms, prior diet--activity patterns, psychological stress, and levels of exercise training were controlled. Cortisol and ACTH were assessed in blood collected immediately before (pre-) and after (post-) each experimental session. Statistical analysis involved repeated measures analysis of variance and Tukey post-hoc testing. The percent change in cortisol from pre- to post-sampling at each session was: resting-control, 40, 60, and 80% sessions (mean+/-SD) =-6.6+/-3.5%, +5.7+/-11.0%, +39.9+/-11.8%, and +83.1+/-18.5%, respectively. The 60% and 80% intensity magnitude of change was significantly greater than in the other sessions, as well as from one to another. The ACTH responses mirrored those of cortisol, but only the 80% exercise provoked a significant (p<0.05) increase pre- to post-exercise. The calculated changes in plasma volume for the resting-control, 40%, 60%, and 80% sessions were: +2.2+/-3.0%, -9.9+/-5.0%, -15.6+/-3.5%, and -17.2+/-3.3%, respectively. Collectively, the cortisol findings support the view that moderate to high intensity exercise provokes increases in circulating cortisol levels. These increases seem due to a combination of hemoconcentration and HPA axis stimulus (ACTH). In contrast, low intensity exercise (40%) does not result in significant increases in cortisol levels, but, once corrections for plasma volume reduction occurred and circadian factors were examined, low intensity exercise actually resulted in a reduction in circulating cortisol levels.
506 citations
TL;DR: The results support the request for more acute CE in schools, even in elite performance schools, and suggest that CE might lead to a pre-activation of parts of the brain which are also responsible for mediating functions like attention.
490 citations
TL;DR: The hypothesis that the "critical power" (CP) represents the highest constant work rate that can be sustained without a progressive depletion of muscle high-energy phosphates and a rapid accumulation of metabolites is supported.
Abstract: We tested the hypothesis that the asymptote of the hyperbolic relationship between work rate and time to exhaustion during muscular exercise, the “critical power” (CP), represents the highest const...
445 citations
TL;DR: Declines in endurance exercise performance and its physiological determinants with ageing appear to be mediated in large part by a reduction in the intensity (velocity) and volume of the exercise that can be performed during training sessions.
Abstract: Older (‘Masters’) athletes strive to maintain or even improve upon the performance they achieved at younger ages, but declines in athletic performance are inevitable with ageing. In this review, we describe changes in peak endurance exercise performance with advancing age as well as physiological factors responsible for those changes. Peak endurance performance is maintained until ∼35 years of age, followed by modest decreases until 50–60 years of age, with progressively steeper declines thereafter. Among the three main physiological determinants of endurance exercise performance (i.e. maximal oxygen consumption , lactate threshold and exercise economy), a progressive reduction in appears to be the primary mechanism associated with declines in endurance performance with age. A reduction in lactate threshold, i.e. the exercise intensity at which blood lactate concentration increases significantly above baseline, also contributes to the reduction in endurance performance with ageing, although this may be secondary to decreases in . In contrast, exercise economy (i.e. metabolic cost of sustained submaximal exercise) does not change with age in endurance-trained adults. Decreases in maximal stroke volume, heart rate and arterio-venous O2 difference all appear to contribute to the age-related reductions in in endurance-trained athletes. Declines in endurance exercise performance and its physiological determinants with ageing appear to be mediated in large part by a reduction in the intensity (velocity) and volume of the exercise that can be performed during training sessions. Given their impressive peak performance capability and physiological function capacity, Masters athletes remain a fascinating model of ‘exceptionally successful ageing’ and therefore are highly deserving of our continued scientific attention as physiologists.
432 citations
TL;DR: Higher capacity to secrete adrenaline was observed both in response to physical exercise and to other stimuli such as hypoglycaemia and hypoxia, and this phenomenon can partly explain the higher physical performance observed in trained compared with untrained subjects.
Abstract: Stress hormones, adrenaline (epinephrine) and noradrenaline (norepinephrine), are responsible for many adaptations both at rest and during exercise. Since their discovery, thousands of studies have focused on these two catecholamines and their importance in many adaptive processes to different stressors such as exercise, hypoglycaemia, hypoxia and heat exposure, and these studies are now well acknowledged. In fact, since adrenaline and noradrenaline are the main hormones whose concentrations increase markedly during exercise, many researchers have worked on the effect of exercise on these amines and reported 1.5 to >20 times basal concentrations depending on exercise characteristics (e.g. duration and intensity). Similarly, several studies have shown that adrenaline and noradrenaline are involved in cardiovascular and respiratory adjustments and in substrate mobilization and utilization. Thus, many studies have focused on physical training and gender effects on catecholamine response to exercise in an effort to verify if significant differences in catecholamine responses to exercise could be partly responsible for the different performances observed between trained and untrained subjects and/or men and women. In fact, previous studies conducted in men have used different types of exercise to compare trained and untrained subjects in response to exercise at the same absolute or relative intensity. Their results were conflicting for a while. As research progressed, parameters such as age, nutritional and emotional state have been found to influence catecholamine concentrations. As a result, most of the recent studies have taken into account all these parameters. Those studies also used very well trained subjects and/or more intense exercise, which is known to have a greater effect on catecholamine response so that differences between trained and untrained subjects are more likely to appear. Most findings then reported a higher adrenaline response to exercise in endurance-trained compared with untrained subjects in response to intense exercise at the same relative intensity as all-out exercise. This phenomenon is referred to as the 'sports adrenal medulla'. This higher capacity to secrete adrenaline was observed both in response to physical exercise and to other stimuli such as hypoglycaemia and hypoxia. For some authors, this phenomenon can partly explain the higher physical performance observed in trained compared with untrained subjects. More recently, these findings have also been reported in anaerobic-trained subjects in response to supramaximal exercise. In women, studies remain scarce; the results are more conflicting than in men and the physical training type (aerobic or anaerobic) effects on catecholamine response remain to be specified. Conversely, the works undertaken in animals are more unanimous and suggest that physical training can increase the capacity to secrete adrenaline via an increase of the adrenal gland volume and adrenaline content.
411 citations
TL;DR: The potential of using heart rate recovery as a measure of training-induced disturbances in autonomic control, which may provide useful information for training prescription, is investigated.
Abstract: Endurance training decreases resting and submaximal heart rate, while maximum heart rate may decrease slightly or remain unchanged after training. The effect of endurance training on various indices of heart rate variability remains inconclusive. This may be due to the use of inconsistent analysis methodologies and different training programmes that make it difficult to compare the results of various studies and thus reach a consensus on the specific training effects on heart rate variability. Heart rate recovery after exercise involves a coordinated interaction of parasympathetic re-activation and sympathetic withdrawal. It has been shown that a delayed heart rate recovery is a strong predictor of mortality. Conversely, endurance-trained athletes have an accelerated heart rate recovery after exercise. Since the autonomic nervous system is interlinked with many other physiological systems, the responsiveness of the autonomic nervous system in maintaining homeostasis may provide useful information about the functional adaptations of the body. This review investigates the potential of using heart rate recovery as a measure of training-induced disturbances in autonomic control, which may provide useful information for training prescription.
402 citations
TL;DR: The present data indicate that body composition changes are affected by the intensity of exercise training with HIET more effectively for reducing total abdominalfat, subcutaneous abdominal fat, and AVF in obese women with the metabolic syndrome.
Abstract: The metabolic syndrome is a complex clustering of metabolic defects associated with physical inactivity, abdominal adiposity, and aging.
Purpose: To examine the effects of exercise training intensity on abdominal visceral fat (AVF) and body composition in obese women with the metabolic syndrome.
Methods: Twenty-seven middle-aged obese women (mean +/- SD; age = 51 +/- 9yr and body mass index = 34 +/- 6 kg[middle dot]m-2) with the metabolic syndrome completed one of three 16-wk aerobic exercise interventions: (i) no-exercise training (Control): seven participants maintained their existing levels of physical activity; (ii) low-intensity exercise training (LIET): 11 participants exercised 5 d[middle dot]wk-1 at an intensity LT and 2 d[middle dot]wk-1 <= LT. Exercise time was adjusted to maintain caloric expenditure (400 kcal per session). Single-slice computed tomography scans obtained at the L4-L5 disc space and midthigh were used to determine abdominal fat and thigh muscle cross-sectional areas. Percent body fat was assessed by air displacement plethysmography.
Results: HIET significantly reduced total abdominal fat (P < 0.001), abdominal subcutaneous fat (P = 0.034), and AVF (P = 0.010). There were no significant changes observed in any of these parameters within the Control or the LIET conditions.
Conclusions: The present data indicate that body composition changes are affected by the intensity of exercise training with HIET more effectively for reducing total abdominal fat, subcutaneous abdominal fat, and AVF in obese women with the metabolic syndrome.
TL;DR: This review focuses on how the cardiovascular system is regulated when exercising in the heat and how restrictions in locomotor skeletal muscle and/or skin perfusion might limit athletic performance in hot environments.
Abstract: Exercise in the heat can pose a severe challenge to human cardiovascular control, and thus the provision of oxygen to exercising muscles and vital organs, because of enhanced thermoregulatory demand for skin blood flow coupled with dehydration and hyperthermia Cardiovascular strain, typified by reductions in cardiac output, skin and locomotor muscle blood flow and systemic and muscle oxygen delivery accompanies marked dehydration and hyperthermia during prolonged and intense exercise characteristic of many summer Olympic events This review focuses on how the cardiovascular system is regulated when exercising in the heat and how restrictions in locomotor skeletal muscle and/or skin perfusion might limit athletic performance in hot environments
TL;DR: It is suggested that feedback from fatiguing muscle plays an important role in the determination of central motor drive and force output, so that the development of peripheral muscle fatigue is confined to a certain level.
Abstract: We asked whether the central effects of fatiguing locomotor muscle fatigue exert an inhibitory influence on central motor drive to regulate the total degree of peripheral fatigue development. Eight cyclists performed constant-workload prefatigue trials (a) to exhaustion (83% of peak power output (Wpeak), 10 ± 1 min; PFT83%), and (b) for an identical duration but at 67%Wpeak (PFT67%). Exercise-induced peripheral quadriceps fatigue was assessed via changes in potentiated quadriceps twitch force (ΔQtw,pot) from pre- to post-exercise in response to supra-maximal femoral nerve stimulation (ΔQtw,pot). On different days, each subject randomly performed three 5 km time trials (TTs). First, subjects repeated PFT83% and the TT was started 4 min later with a known level of pre-existing locomotor muscle fatigue (ΔQtw,pot−36%) (PFT83%-TT). Second, subjects repeated PFT67% and the TT was started 4 min later with a known level of pre-existing locomotor muscle fatigue (ΔQtw,pot−20%) (PFT67%-TT). Finally, a control TT was performed without any pre-existing level of fatigue. Central neural drive during the three TTs was estimated via quadriceps EMG. Increases in pre-existing locomotor muscle fatigue from control TT to PFT83%-TT resulted in significant dose-dependent changes in central motor drive (−23%), power output (−14%), and performance time (+6%) during the TTs. However, the magnitude of locomotor muscle fatigue following various TTs was not different (ΔQtw,pot of −35 to −37%, P= 0.35). We suggest that feedback from fatiguing muscle plays an important role in the determination of central motor drive and force output, so that the development of peripheral muscle fatigue is confined to a certain level.
TL;DR: Exceeding the intensity of the ventilatory threshold appears to reduce pleasure, an effect that could negatively impact adherence, and hypotheses derived from the dual-mode model were tested.
Abstract: A causal chain linking exercise intensity, affective responses (e.g., pleasure–displeasure), and adherence has long been suspected as a contributor to the public health problem of physical inactivity. However, progress in the investigation of this model has been limited, mainly due to inconsistent findings on the first link between exercise intensity and affective responses. The purpose was to reexamine the intensity–affect relationship using a new methodological platform. Thirty young adults (14 women and 16 men) participated in 15-min treadmill exercise sessions below, at, and above their ventilatory threshold. The innovative elements were the following: (a) Affect was assessed in terms of the dimensions of the circumplex model; (b) assessments were made repeatedly during and after exercise; (c) patterns of interindividual variability were examined; (d) intensity was determined in relation to the ventilatory threshold; and (e) hypotheses derived from the dual-mode model were tested. Intensity did not influence the positive changes from pre- to post-exercise, but it did influence the responses during exercise, with the intensity that exceeded the ventilatory threshold eliciting significant and relatively homogeneous decreases in pleasure. Exceeding the intensity of the ventilatory threshold appears to reduce pleasure, an effect that could negatively impact adherence.
TL;DR: Moderate physical activity is important for youth whose brains are highly plastic and perhaps even more critical for young people with physical disability.
Abstract: This commentary reviews selected biomedical and clinical research examining the relationship between physical exercise and cognitive function especially in youth with disability. Youth with physical disability may not benefit from the effects of exercise on cardiovascular fitness and brain health since they are less active than their non-disabled peers. In animal models, physical activity enhances memory and learning, promotes neurogenesis and protects the nervous system from injury and neurodegenerative disease. Neurotrophins, endogenous proteins that support brain plasticity likely mediate the beneficial effects of exercise on the brain. In clinical studies, exercise increases brain volume in areas implicated in executive processing, improves cognition in children with cerebral palsy and enhances phonemic skill in school children with reading difficulty. Studies examining the intensity of exercise required to optimize neurotrophins suggest that moderation is important. Sustained increases in neurotrophin levels occur with prolonged low intensity exercise, while higher intensity exercise, in a rat model of brain injury, elevates the stress hormone, corticosterone. Clearly, moderate physical activity is important for youth whose brains are highly plastic and perhaps even more critical for young people with physical disability.
TL;DR: When volume of exercise is controlled, higher intensities of exercise are more effective for improving VO2max than lower intensitiesof exercise in healthy, young adults.
Abstract: GORMLEY, S. E., D. P. SWAIN, R. HIGH, R. J. SPINA, E. A. DOWLING, U. S. KOTIPALLI, and R. GANDRAKOTA. Effect of Intensity of Aerobic Training on VO2max. Med. Sci. Sports Exerc., Vol. 40, No. 7, pp. 1336-1343, 2008. Purpose: To determine whether various intensities of aerobic training differentially affect aerobic capacity as well as resting HR and resting blood pressure (BP). Methods: Sixty-one health young adult subjects were matched for sex and VO2max and were randomly assigned to a moderate- (50% VO2 reserve (VO2R), vigorous (75% VO2R), near-maximal-intensity (95% VO2R), or a nonexercising control group. Intensity during exercise was controlled by having the subjects maintain target HR based on HR reserve. Exercise volume (and thus energy expenditure) was controlled across the three training groups by varying duration and frequency. Fifty-five subjects completed a 6-wk training protocol on a stationary bicycle ergometer and pre- and posttesting. During the final 4 wk, the moderate-intensity group exercised for 60 min, 4 dIwk j1 the vigorous-intensity group exercised for 40 min, 4 dIwk j1 and the near-maximal-intensity group exercised 3 dIwk j1 performing 5 min at 75% VO2R followed by five intervals of 5 min at 95% VO2R and 5 min at 50% VO2R. Results: VO2max significantly increased in all exercising groups by 7.2, 4.8, and 3.4 mLImin j1 Ikg j1 in the near-maximal-, the vigorous-, and the moderate-intensity groups, respectively. Percent increases in the near-maximal- (20.6%), the vigorous- (14.3%), and the moderate-intensity (10.0%) groups were all significantly different from each other (P G 0.05). There were no significant changes in resting HR and BP in any group. Conclusion: When volume of exercise is controlled, higher intensities of exercise are more effective
TL;DR: Beneficial effects of various exercise programs on aspects of cognition have been observed in studies among subjects with and without cognitive decline, however, the majority of the studies did not find any effect.
Abstract: Objective: To systematically review the effect of physical exercise on cognition in older adults with and without cognitive decline. Data sources: Randomized controlled trials were identified by literature searches in PubMed, EMBASE, CENTRAL, PsycINFO, and AgeLine. Study selection: Papers were included on the basis of predefined inclusion criteria. Data extraction: Data on study population, exercise intervention, and effectiveness were extracted. Two independent reviewers assessed methodological quality. Data synthesis: Twenty-three studies were included-15 among cognitively healthy subjects and 8 among subjects with cognitive decline. Seven studies were qualified as high-quality studies, 2 in cognitively healthy subjects and 5 in subjects with cognitive decline. In cognitively healthy subjects, significant beneficial intervention effects were observed in 5 studies on information processing, executive function, or memory. Interventions in these studies included aerobic exercise only (n = 2); strength exercise (n = 1); strength and balance exercise (n = 1); or all-round exercise including aerobic, strength, balance and flexibility training (n = 1). In subjects with cognitive decline, 5 studies observed beneficial effects on general cognition, executive functions, and memory. Interventions included aerobic (n = 3) or strength exercise combined with flexibility or balance exercise (n = 2). Conclusions: Beneficial effects of various exercise programs on aspects of cognition have been observed in studies among subjects with and without cognitive decline. The majority of the studies, however, did not find any effect. The small number of included studies; lack of high-quality studies; and the large variability in study populations, exercise protocols, and outcome measures complicate interpretation of the results. More high-quality trials are needed to assess the effects of different types of exercise on cognitive function in older adults with and without cognitive decline. © 2008 by Lippincott Williams & Wilkins.
TL;DR: Higher O(2) pulse is associated with better exercise performance, whereas adolescence and male gender are associated with decreased performance compared with healthy subjects, in Fontan patients.
TL;DR: Findings suggest that respiratory muscle fatigue may be involved in limiting exercise tolerance or that other factors, including alterations in the sensation of dyspnea or mechanical load, may be important.
Abstract: It is commonly held that the respiratory system has ample capacity relative to the demand for maximal O2 and CO2 transport in healthy humans exercising near sea level. However, this situation may n...
TL;DR: The liver function parameters, AST and ALT, were significantly increased for at least 7 days after the exercise and LD and, in particular, CK and myoglobin showed highly elevated levels.
Abstract: Aim
To investigate the effect of intensive muscular exercise (weightlifting) on clinical chemistry parameters reflecting liver function in healthy men.
TL;DR: Although it is generally accepted that the promotion of exercise accords with clinical best practice, the anecdotal experience of many primary care physicians, cardiologists, and exercise physiologists is that, even when exercise prescriptions are adhered to, risk factors often fail to demonstrate.
Abstract: although it is generally accepted that the promotion of exercise accords with clinical best practice, the anecdotal experience of many primary care physicians, cardiologists, and exercise physiologists is that, even when exercise prescriptions are adhered to, risk factors often fail to demonstrate
TL;DR: Visceral adipose tissue is lost preferentially with modest weight Loss, but the effect is attenuated with greater weight loss, which may help to explain the metabolic benefits of modest weight loss.
Abstract: Visceral adipose tissue (VAT) is associated with greater obesity-related metabolic disturbance. Many studies have reported preferential loss of VAT with weight loss. This systematic review looks for factors associated with preferential loss of VAT relative to subcutaneous abdominal fat (SAT) during weight loss. Medline and Embase were searched for imaging-based measurements of VAT and subcutaneous abdominal adipose tissue (SAT) before and after weight loss interventions. We examine for factors that influences the percentage change in VAT versus SAT (%δV/%δS) with weight loss. Linear regression analyses were performed on the complete data set and on subgroups of studies. Factors examined included percentage weight loss, degree of caloric restriction, exercise, initial body mass index (BMI), gender, time of follow-up and baseline VAT/SAT. There were 61 studies with a total of 98 cohort time points extracted. Percentage weight loss was the only variable that influenced %δV/%δS (r=−0.29, P=0.005). Modest weight loss generated preferential loss of VAT, but with greater weight loss this effect was attenuated. The method of weight loss was not an influence with one exception. Very-low-calorie diets (VLCDs) provided exceptional short-term (<4 weeks) preferential VAT loss. But this effect was lost by 12–14 weeks. Visceral adipose tissue is lost preferentially with modest weight loss, but the effect is attenuated with greater weight loss. Acute caloric restriction, using VLCD, produces early preferential loss of VAT. These observations may help to explain the metabolic benefits of modest weight loss.
TL;DR: The consistent and robust finding of higher mRNA abundance for most components ofFat oxidation pathways in women compared with men is directionally consistent with the substrate-oxidation data, implying that fat oxidation is regulated and that carbohydrate and protein oxidation follow by metabolic demand.
Abstract: Women oxidize more lipid and less carbohydrate and protein compared with men during endurance exercise. The increase in fat oxidation is associated with higher intramyocellular lipid content and use as well as greater adipocyte lipolysis. Glucose rates of appearance and disappearance are lower for women than for men, with no change in basal muscle glycogen, and some evidence for muscle glycogen sparing during endurance exercise. Women oxidize less protein compared with men and show lower leucine oxidation during exercise. The consistent and robust finding of higher mRNA abundance for most components of fat-oxidation pathways in women compared with men is directionally consistent with the substrate-oxidation data. A lack of directional consistency between mRNA species involved in carbohydrate and protein metabolism and the known sex differences during exercise implies that fat oxidation is regulated and that carbohydrate and protein oxidation follow by metabolic demand. Administration of 17-beta-estradiol to men recapitulates most of the described sex differences in metabolism and mRNA content. The greater fat oxidation for women during submaximal endurance exercise compared with men seems to occur partly through a sex hormone-mediated enhancement of lipid-oxidation pathways.
TL;DR: In this paper, the authors evaluated 12 wk of exercise (aerobic and resistance) or 12wk of weight loss (approximately 7% reduction) on skeletal muscle mRNAs for toll-like receptor-4 (TLR-4), mechanogrowth factor (MGF), TNF-alpha, and IL-6 in 16 obese (body mass index 38+/-2 kg/m2) older (69+/-1 yr) physically frail individuals.
Abstract: Many obese elderly persons have impaired physical function associated with an increased chronic inflammatory response. We evaluated 12 wk of exercise (aerobic and resistance) or 12 wk of weight loss (approximately 7% reduction) on skeletal muscle mRNAs for toll-like receptor-4 (TLR-4), mechanogrowth factor (MGF), TNF-alpha, and IL-6 in 16 obese (body mass index 38+/-2 kg/m2) older (69+/-1 yr) physically frail individuals. Vastus lateralis muscle biopsies were obtained at 0 and 12 wk and analyzed by real-time RT-PCR. Body composition was assessed by dual-energy x-ray absorptiometry. Body weight decreased (-7.5+/-1.2 kg, P=0.001) in the weight loss group but not in the exercise group (-0.3+/-0.8 kg, P=0.74). Fat-free mass (FFM) decreased (-2.9+/-0.6 kg, P=0.010) in the weight loss group and increased (1.6+/-0.6 kg, P=0.03) in the exercise group. Exercise resulted in a 37% decrease in TLR-4 mRNA (P<0.05) while weight loss had no significant effect. Additionally, exercise led to a significant (50%) decrease in IL-6 and TNF-alpha mRNA (P<0.05) while weight loss had no effect. Exercise increased MGF mRNA (approximately 2 fold, P<0.05), but weight loss had no effect. In conclusion, exercise but not weight loss had a beneficial effect on markers of muscle inflammation and anabolism in frail obese elderly individuals.
TL;DR: The extent and duration of post-exercise cardiac injury with particular attention to right ventricular (RV) dysfunction was quantified, with a significant reduction in RV function.
Abstract: Background: There is evidence that ultra-endurance exercise causes myocardial injury. The extent and duration of these changes remains unresolved. Recent reports have speculated that structural adaptations to exercise, particularly of the right ventricle, may predispose to tachyarrhythmias and sudden cardiac death. Objective: To quantify the extent and duration of post-exercise cardiac injury with particular attention to right ventricular (RV) dysfunction. Methods: 27 athletes (20 male, 7 female) were tested 1 week before, immediately after and 1 week after an ultra-endurance triathlon. Tests included cardiac troponin I (cTnI), B-type natriuretic peptide (BNP) and comprehensive echocardiographic assessment. Results: 26 athletes completed the race and testing procedures. Post-race, cTnI was raised in 15 athletes (58%) and the mean value for the entire cohort increased (0.17 vs 0.49 μg/l, p Conclusion: Myocardial damage occurs during intense ultra-endurance exercise and, in particular, there is a significant reduction in RV function. Almost all abnormalities resolve within 1 week.
TL;DR: In this review, the current literature describing the molecular signals underlying skeletal muscle responses to acute and chronic exercise are summarized and the search for possible exercise/contraction‐stimulated signaling proteins involved in glucose transport, muscle fiber type, and mitochondrial biogenesis is ongoing.
Abstract: Physical activity elicits physiological responses in skeletal muscle that result in a number of health benefits, in particular in disease states, such as type 2 diabetes. An acute bout of exercise/muscle contraction improves glucose homeostasis by increasing skeletal muscle glucose uptake, while chronic exercise training induces alterations in the expression of metabolic genes, such as those involved in muscle fiber type, mitochondrial biogenesis, or glucose transporter 4 (GLUT4) protein levels. A primary goal of exercise research is to elucidate the mechanisms that regulate these important metabolic and transcriptional events in skeletal muscle. In this review, we briefly summarize the current literature describing the molecular signals underlying skeletal muscle responses to acute and chronic exercise. The search for possible exercise/contraction-stimulated signaling proteins involved in glucose transport, muscle fiber type, and mitochondrial biogenesis is ongoing. Further research is needed because full elucidation of exercise-mediated signaling pathways would represent a significant step toward the development of new pharmacological targets for the treatment of metabolic diseases such as type 2 diabetes.
TL;DR: The results indicate that low-intensity resistance training increases muscular size and strength when combined with resistance exercise with blood flow restriction for other muscle groups.
Abstract: Purpose: This study investigated whether muscle hypertrophy-promoting effects are cross-transferred in resistance training with blood flow restriction, which has been shown to evoke strong endocrine activation.
Methods: Fifteen untrained men were randomly assigned into the occlusive training group (OCC, N = 8) and the normal training group (NOR, N = 7). Both groups performed the same unilateral arm exercise (arm curl) at 50% of one-repetition maximum (1RM) without occlusion (three sets, 10 repetitions). Either the dominant or nondominant arm was randomly chosen to be trained (OCC-T, NOR-T) or to serve as a control (OCC-C, NOR-C). After the arm exercise, OCC performed leg exercise with blood flow restriction (30% of 1RM, three sets, 15-30 repetitions), whereas NOR performed the same leg exercise without occlusion. The training session was performed twice a week for 10 wk. In a separate set of experiments, acute changes in blood hormone concentrations were measured after the same leg exercises with (N = 5) and without (N = 5) occlusion.
Results: Cross-sectional area (CSA) and isometric torque of elbow flexor muscles increased significantly in OCC-T, whereas no significant changes were observed in OCC-C, NOR-T, and NOR-C. CSA and isometric torque of thigh muscles increased significantly in OCC, whereas no significant changes were observed in NOR. Noradrenaline concentration showed a significantly larger increase after leg exercise with occlusion than after exercises without occlusion, though growth hormone and testosterone concentrations did not show significant differences between these two types of exercises.
Conclusion: The results indicate that low-intensity resistance training increases muscular size and strength when combined with resistance exercise with blood flow restriction for other muscle groups. It was suggested that any circulating factor(s) was involved in this remote effect of exercise on muscular size
TL;DR: It is suggested that short-duration, high-intensity exercise increases the secretion rate of s-IgA and s-Lys despite no change in the saliva flow rate, and these effects appear to be associated with changes in sympathetic activity and not the hypothalamic – pituitary – adrenal axis.
Abstract: In the present study, we assessed the effects of exercise intensity on salivary immunoglobulin A (s-IgA) and salivary lysozyme (s-Lys) and examined how these responses were associated with salivary markers of adrenal activation. Using a randomized design, 10 healthy active men participated in three experimental cycling trials: 50% maximal oxygen uptake (VO2max), 75%VO2max, and an incremental test to exhaustion. The durations of the trials were the same as for a preliminary incremental test to exhaustion (22.3 min, sx = 0.8). Timed, unstimulated saliva samples were collected before exercise, immediately after exercise, and 1 h after exercise. In the incremental exhaustion trial, the secretion rates of both s-IgA and s-Lys were increased. An increase in s-Lys secretion rate was also observed at 75%VO2max. No significant changes in saliva flow rate were observed in any trial. Cycling at 75%VOmax and to exhaustion increased the secretion of alpha-amylase and chromogranin A immediately after exercise; higher cortisol values at 75%VO2max and in the incremental exhaustion trial compared with 50%VO2max were observed 1 h immediately after exercise only. These findings suggest that short-duration, high-intensity exercise increases the secretion rate of s-IgA and s-Lys despite no change in the saliva flow rate. These effects appear to be associated with changes in sympathetic activity and not the hypothalamic - pituitary - adrenal axis.
TL;DR: Regular exercise that incorporates PRT should be used to attenuate muscle mass loss in frail obese older adults on weight-loss therapy.
Abstract: Purpose: To evaluate the effect of adding exercise to a hypocaloric diet on changes in appendicular lean mass and strength in frail obese older adults undergoing voluntary weight loss.
Methods: Thirty frail older (age, 70 +/- 5 yr) obese (body mass index, 37 +/- 5 kg[middle dot]m-2) adults were randomly assigned to 6 months of diet/behavioral therapy (diet group, n = 15) or diet or behavioral therapy plus exercise that incorporated progressive resistance training (PRT; diet + exercise group; n = 15). Body composition was assessed using dual-energy x-ray absorptiometry, and muscle strength was assessed using one-repetition maximum. The volume of upper extremity (UE) and lower extremity (LE) exercise training was determined by multiplying the average number of repetitions performed by the average weight lifted during the first three exercise sessions and during the last three exercise sessions of the study.
Results: The diet and the diet + exercise groups had similar (P > 0.05) decreases in weight (10.7 +/- 4.5 vs 9.7 +/- 4.0 kg) and fat mass (6.8 +/- 3.7 vs 7.7 +/- 2.9 kg). However, the diet + exercise group lost less fat-free mass (FFM; 1.8 +/- 1.5 vs 3.5 +/- 2.1 kg), LE lean mass (0.9 +/- 0.8 vs 2.0 +/- 0.9 kg), and UE lean mass (0.1 +/- 0.2 vs 0.2 +/- 0.2 kg) than the diet group (P < 0.05). The diet + exercise group had greater increases in percent of weight as FFM (FFM / weight x 100) than the diet group (7.9 +/- 3.3 vs 5.4 +/- 3.7%; P < 0.05). Despite lean mass losses, the diet + exercise group increased UE and LE strength in response to exercise (17-43%), whereas the diet group maintained strength. The volume of UE and LE exercises correlated with the amount of UE and LE lean mass (r = 0.64-0.84; P < 0.05).
Conclusion: Exercise added to diet reduces muscle mass loss during voluntary weight loss and increases muscle strength in frail obese older adults. Regular exercise that incorporates PRT should be used to attenuate muscle mass loss in frail obese older adults on weight-loss therapy.
Journal Article•
TL;DR: Playing new generation active computer games uses significantly more energy than playing sedentary computer games but not as much energy as playing the sport itself.
Abstract: Objective To compare the energy expenditure of adolescents when playing sedentary and new generation active computer games. Design Cross sectional comparison of four computer games. Setting Research laboratories. Participants Six boys and fi ve girls aged 13-15 years. Procedure Participants were fi tted with a monitoring device validated to predict energy expenditure. They played four computer games for 15 minutes each. One of the games was sedentary (XBOX 360) and the other three were active (Wii Sports). Main outcome measure Predicted energy expenditure, compared using repeated measures analysis of variance. Results Mean (standard deviation) predicted energy expenditure when playing Wii Sports bowling (190.6 (22.2) kJ/kg/min), tennis (202.5 (31.5) kJ/kg/min), and boxing (198.1 (33.9) kJ/kg/min) was signifi cantly greater than when playing sedentary games (125.5 (13.7) kJ/kg/min) (P<0.001). Predicted energy expenditure was at least 65.1 (95% confi dence interval 47.3 to 82.9) kJ/kg/min greater when playing active rather than sedentary games. Conclusions Playing new generation active computer games uses signifi cantly more energy than playing sedentary computer games but not as much energy as playing the sport itself. The energy used when playing active Wii Sports games was not of high enough intensity to contribute towards the recommended daily amount of exercise in children.