Submaximal Exercise Training Research Articles

Simulated Altitude Training and Sport Performance: Protocols and Physiological Effects

This article explores the physiological mechanisms and effects of simulated hypoxia environment training on sports performance. Different training protocols, including hypoxia high-intensity interval training (HHIIT), incremental hypoxia training, hypoxia submaximal exercise training and combined training, and hypoxia training in the recovery and sleep states, are discussed. HHIIT combines intermittent hypoxia exposure with high-intensity interval training, and has been shown to increase the maximum oxygen intake compare to the state of normoxia, improving cardiorespiratory fitness, skeletal muscle oxygen utilization, power performance, hematological adaptations, and sports performance. Incremental hypoxia training involves the gradual decrease in oxygen concentration while maintaining exercise intensity. It has been found to improve aerobic capacity; however, fewer effects were observed in hematological variables. Hypoxia submaximal exercise training and combined training in a hypoxia environment has shown to increase VO2 and VE, and only improve hemodynamic function in combined training with hypoxia. Hypoxia during the recovery state has been associated with improvements in maximum oxygen uptake, also providing benefits to sports performance. Overall, exposure to a hypoxia environment has been demonstrated to improve cardiorespiratory endurance, power performance, and specific physiological adaptations in training and resting states. However, the optimal training protocols and their effects on different sports and athlete proficiency require further research to optimize training and enhance athletic performance in hypoxia environments.

Prior brain endurance training improves endurance exercise performance

ABSTRACT Mental fatigue (MF) impairs endurance exercise performance. Brain endurance training (BET) describes the systematic repetition of mentally-fatiguing cognitive tasks designed to build resilience to MF and improve endurance performance. Evidence to date shows that mental training during physical training can benefit post-training exercise performance, however, this concurrent BET approach may not be practical for all settings. Therefore, the current study evaluated the effects of mental training before physical training (prior BET) on exercise performance. A randomised control trial design: pre-test, training (BET, control), post-test. During the pre-test and post-test sessions, participants performed a 5-min rhythmic handgrip task requiring the generation of as much force as possible, a 20-min 2-back working memory task, and another 5-min rhythmic handgrip task. Participants were randomly assigned to a BET (n = 12) or control group (n = 12). Both groups completed the same submaximal rhythmic handgrip training for five weeks (four sessions per week). The BET group also completed 20-min cognitive training (2-back working memory task, incongruent colour-word Stroop task) before each submaximal exercise training session. Endurance performance improved more (p < 0.05) following BET (24%) than physical training alone (12%). Compared to the control group, the BET group showed higher prefrontal oxygenation during the post-test exercise tasks (p < 0.05). Both groups were characterised by the same exertion, motivation, heart rate, and heart rate variability. Mental training before physical training improves endurance performance greater than physical training alone. The benefits of prior BET may be explained, at least in part, by improved prefrontal oxygenation. Highlights This study provides further evidence that brain endurance training (BET) improves performance over matched physical training. Prior BET (i.e. engaging in mentally demanding cognitive tasks before physical training) offers another option to enhance fatigue resilience, which expands the use of BET to more sports and potentially higher intensity training where concurrent BET will not be practical. The benefits of prior BET may be explained, at least in part, by improved prefrontal oxygenation.

Elevated dietary selenium rescues mitochondrial capacity impairment induced by decreased vitamin E intake in young exercising horses.

Maintenance of mitochondrial health, which is supported in part by dietary antioxidants such as selenium (Se) and vitamin E (vitE), is pertinent to optimizing athletic performance. Deficiencies in Se and vitE negatively impact muscle health but mitochondrial adaptations to various levels of dietary Se and vitE are poorly understood. Young Quarter Horses (mean ± SD: 17.6 ± 0.9 mo) undergoing submaximal exercise training were used to test the hypothesis that a proprietary antioxidant blend containing elevated Se yeast (EconomasE, Alltech, Inc., Nicholasville, KY) would improve mitochondrial characteristics compared to Se at current requirements, even with reduced vitE intake. Horses were balanced by age, sex, body weight (BW), and farm of origin and randomly assigned to one of three custom-formulated concentrates fed at 1% BW (dry matter, DM basis) for 12 wk: 1) 100 IU vitE/kg DM and 0.1 mg Se/kg DM (CON, n = 6); 2) no added vitE plus EconomasE to provide 0.1 mg Se/kg DM (ESe1, n = 6); or 3) no added vitE plus EconomasE to provide 0.3 mg Se/kg DM (ESe3, n = 6). Samples collected at week 0 and 12 were analyzed for serum Se and middle gluteal glutathione peroxidase (GPx) and mitochondrial enzyme activities by kinetic colorimetry and mitochondrial capacities by high-resolution respirometry. Data were analyzed using mixed linear models in SAS v9.4 with repeated measures (time) and fixed effects of time, diet, and time × diet; horse(diet) served as a random effect. Serum Se tended to increase in all horses by week 12 (P = 0.08) but was unaffected by diet. Muscle GPx activity remained similar among all horses throughout the duration of the study. Mitochondrial volume density (citrate synthase [CS] activity), integrative function (cytochrome c oxidase [CCO] activity per mg protein), and integrative (per mg tissue) oxidative (P) and electron transfer (E) capacities increased from week 0 to 12 in all horses (P ≤ 0.01). Intrinsic (relative to CS) CCO activity decreased in all horses (P = 0.001), while intrinsic P and E capacities decreased only in ESe1 horses from week 0 to 12 (P ≤ 0.002). These results suggest that feeding EconomasE to provide 0.3 mg Se/kg DM may prevent adverse effects of removing 100 IU dietary vitE/kg DM on mitochondria in young horses. More research is needed to determine optimal dietary Se and vitE levels in performance horses to maximize mitochondrial energy production.

31 Relationship of Mitochondrial Phenotype to Muscle Function and Performance

Abstract Skeletal muscle mitochondria are vital for producing sufficient energy to fuel muscle contractions during exercise. Embedded within the inner mitochondrial membrane are 4 separate protein complexes that are responsible for transferring electrons from specific substrates to the final electron acceptor, oxygen. The proton gradient that is formed from the movement of electrons then drives complex V, synthesizing ATP to fuel cellular work. Recent technological advancements enable exploration beyond simple measures of mitochondria, such as density and overall function, to identify how the organelles produce energy. Specifically, high-resolution respirometry allows investigation into the capacity of each of these mitochondrial protein complexes to determine if they are differentially utilized during specific types of exercise. Further, unique profiles of utilization of these complexes may be hallmarks of success within a certain performance discipline (e.g., racing, dressage, western work, or jumping). In recent years, our laboratory has substantially contributed to progress in this area of research. Under 3 specific scenarios we: 1) defined in horses as young as 6-months-old differential utilization of complexes among breeds destined for certain racing distances; 2) demonstrated differential impacts on specific mitochondrial complexes between submaximal and high-intensity exercise training; and 3) identified a signature of mitochondrial energy production in Thoroughbred racehorses as weanlings that correlates with their race performance later in life. Complex-specific skeletal muscle mitochondrial research in horses is its infancy but has substantial promise to be used as a tool to optimize performance and prevent fatigue-induced injury in performance horses. Further, greater understanding of the inter-relationships of mitochondrial energy production, exercise training, management, and feeding protocols will be crucial to ensure horses realize their peak performance potential and to maintain animal welfare during intense training and competition schedules.

Sub-maximal aerobic exercise training reduces haematocrit and ameliorates symptoms in Andean highlanders with chronic mountain sickness.

New Findings What is the central question of this study? What is the effect of sub‐maximal aerobic exercise training on signs and symptoms of chronic mountain sickness (CMS) in Andean highlanders? What is the main finding and its importance? Aerobic exercise training (ET) effectively reduces haematocrit, ameliorates symptoms and improves aerobic capacity in CMS patients, suggesting that a regular aerobic ET programme might be used as a low‐cost non‐invasive/non‐pharmacological management strategy of this syndrome. Excessive erythrocytosis is the hallmark sign of chronic mountain sickness (CMS), a debilitating syndrome associated with neurological symptoms and increased cardiovascular risk. We have shown that unlike sedentary residents at the same altitude, trained individuals maintain haematocrit within sea‐level range, and thus we hypothesise that aerobic exercise training (ET) might reduce excessive haematocrit and ameliorate CMS signs and symptoms. Eight highlander men (38 ± 12 years) with CMS (haematocrit: 70.6 ± 1.9%, CMS score: 8.8 ± 1.4) from Cerro de Pasco, Peru (4340 m) participated in the study. Baseline assessment included haematocrit, CMS score, pulse oximetry, maximal cardiopulmonary exercise testing and in‐office plus 24 h ambulatory blood pressure (BP) monitoring. Blood samples were collected to assess cardiometabolic, erythropoietic, and haemolysis markers. ET consisted of pedalling exercise in a cycloergometer at 60% of V˙O2peak for 1 h/day, 4 days/week for 8 weeks, and participants were assessed at weeks 4 and 8. Haematocrit and CMS score decreased significantly by week 8 (to 65.6 ± 6.6%, and 3.5 ± 0.8, respectively, P < 0.05), while V˙O2peak and maximum workload increased with ET (33.8 ± 2.4 vs. 37.2 ± 2.0 ml/min/kg, P < 0.05; and 172.5 ± 9.4 vs. 210.0 ± 27.8 W, P < 0.01; respectively). Except for an increase in high‐density lipoprotein cholesterol, other blood markers and BP showed no differences. Our results suggest that reduction of haematocrit and CMS symptoms results mainly from haemodilution due to plasma volume expansion rather than to haemolysis. In conclusion, we show that ET can effectively reduce haematocrit, ameliorate symptoms and improve aerobic capacity in CMS patients, suggesting that regular aerobic exercise might be used as a low‐cost non‐invasive and non‐pharmacological management strategy.

Submaximal exercise training, more than dietary selenium supplementation, improves antioxidant status and ameliorates exercise-induced oxidative damage to skeletal muscle in young equine athletes.

Submaximal exercise training, more than dietary selenium supplementation, improves antioxidant status and ameliorates exercise-induced oxidative damage to skeletal muscle in young equine athletes.

The effects of submaximal exercise training on cardiovascular functions and physical capacity in dogs with myxomatous mitral valve disease

The effects of submaximal exercise training on cardiovascular functions and physical capacity in dogs with myxomatous mitral valve disease

High-intensity interval training in overweight and obese children and adolescents: systematic review and meta-analysis.

While High Intensity Interval Training is praised in many populations for its beneficial effects on body composition and cardiometabolic health, its use among obese youth remain uncertain. This study aimed at determining whether HIIT is effective to improve aerobic fitness and reduce cardiometabolic risk factors in overweight and obese youth. A systematic search was conducted and articles reporting studies that investigated the effects of HIIT in 6 to 18-year-old youth were eligible. Meta-analyses were performed when appropriate. Fifteen studies were included for the systematic review and meta-analyses. HIIT significantly improves maximal oxygen uptake (1.117 [95% CI: 0.528 to 1.706], P<0.001), and reduces body mass (-0.295 [95% CI: -0.525 to -0.066], P<0.05), body fat (-0.786 [95% CI: -1.452 to -0.120], P<0.05), systolic and diastolic blood pressure (-1.026 [95% CI: -1.370 to -0.683], P<0.001; -0.966 [95% CI: -1.628 to -0.304], P<0.01 respectively), and the HOMA-IR (-1.589 [95% CI: -2.528 to -0.650], P<0.01). However, there is significant heterogeneity, and low to high inconsistency for most cardiometabolic risk factors and aerobic fitness. Although few studies have reported cardiometabolic risks, HIIT may also be as effective as traditional endurance continuous training to decrease blood pressure and insulin resistance. HIIT is effective to improve aerobic fitness, body composition, and cardiometabolic risk factors in obese youth, but data are insufficient to determine whether it is more effective than traditional continuous submaximal intensity exercise training.

Executive control processes are associated with individual fitness outcomes following regular exercise training: blood lactate profile curves and neuroimaging findings

Cardiovascular training has been associated with neuroimaging correlates of executive control functions (ECF) in seniors and children/adolescents, while complementary studies in middle-aged populations are lacking. Ascribing a prominent role to cardiorespiratory fitness improvements, most studies concentrated on training-induced gains in maximal oxygen uptake (VO2max), although other fitness indices may provide complementary information. Here, we investigated the impact of long-term sub-maximal exercise training on interference control, considering individual training-induced shifts in blood lactate profile curves (BLC) and VO2max. Twenty-three middle-aged sedentary males (M = 49 years) underwent a six-month exercise program (intervention group, IG). Additionally, 14 individuals without exercise training were recruited (control group, CG, M = 52 years). Interference control was assessed before and after the intervention, using a functional magnetic resonance imaging (fMRI) flanker paradigm. Task performance and brain activations showed no significant group-by-time interactions. However, regression analyses in the IG revealed significant associations between individual fitness gains and brain activation changes in frontal regions, which were not evident for VO2max, but for BLC. In conclusion, training-induced plasticity of ECF-related brain activity can be observed in late middle adulthood, but depends on individual fitness gains. For moderate training intensities, BLC shifts may provide sensitive markers for training-induced adaptations linked to ECF-related brain function.

Submaximal exercise training improves mitochondrial efficiency in the gluteus medius but not in the triceps brachii of young equine athletes

We tested the hypothesis that, similar to humans and rodents, exercise training would enhance mitochondrial (Mt) biogenesis and function in skeletal muscle of young horses. Twenty-four Quarter Horse yearlings were randomly assigned to either submaximal exercise training or no forced exercise (untrained). Biopsies were collected from the gluteus medius and triceps brachii before and after 9 wk of treatment. Citrate synthase activity was lower (P < 0.0001) and cytochrome c oxidase activity per Mt unit was higher (P < 0.0001) in gluteus compared to triceps, but neither changed over the trial period. From wk 0 to 9, intrinsic Mt respiration (PCI, PCI+II; P = 0.008) and electron transport capacity (ECI+II; P = 0.01) increased, and LEAK-related flux control factor (FCFL; P = 0.02) decreased in both muscles. After 9 wk of training, gluteus muscle exhibited higher (P < 0.05) intrinsic PCI, PCI+II, ECI+II, and FCFCI and FCFCI+II, and lower FCFL (P = 0.0002). Mitochondrial content did not change from wk 0 to 9, and also not in response to submaximal exercise training. Improvements in Mt function were most directly related to ongoing growth of horses independent of muscle group, and training further enhanced Mt function in the gluteus medius.

Submaximal exercise training, more than dietary selenium supplementation, improves antioxidant status and ameliorates exercise-induced oxidative damage to skeletal muscle in young equine athletes.

Exercise is associated with increased production of reactive oxygen species (ROS) as metabolism is upregulated to fuel muscle activity. If antioxidant systems become overwhelmed, ROS can negatively affect health and performance. Adaptation to exercise through regular training has been shown to improve defense against oxidative insult. Given selenium's role as an antioxidant, we hypothesized that increased Se intake would further enhance skeletal muscle adaptations to training. Quarter Horse yearlings (18 ± 0.2 mo; 402 ± 10 kg) were randomly assigned to receive either 0.1 or 0.3 mg Se/kg DM and placed in either an untrained or a trained (30 min walk-trot-canter, 4 d/wk) group for 14 wk. Phase 1 (wk 1 to 8) consisted of 4 treatments: trained and fed 0.1 mg Se/kg DM through wk 14 (CON-TR; n = 10), trained and fed 0.3 mg Se/kg DM through wk 14 (HIGH-TR; n = 10), untrained and fed 0.1 mg Se/kg DM through wk 14 (CON-UN; n = 5), or untrained and fed 0.3 mg Se/kg DM through wk 14 (HIGH-UN; n = 5). During Phase 2 (wk 9 to 14), dietary Se level in half of the trained horses was reversed, resulting in 6 treatments: CON-TR (n = 5), trained and fed 0.1 mg/kg Se in Phase 1 and then switched to 0.3 mg/kg Se for Phase 2 (ADD-TR; n = 5), trained and fed 0.3 mg/kg Se in Phase 1 and then switched to 0.1 mg/kg Se for Phase 2 (DROP-TR; n = 5), HIGH-TR (n = 5), CON-UN (n = 5), or HIGH-UN (n = 5). All horses underwent a 120-min submaximal exercise test (SET) at the end of Phase 1 (SET 1) and 2 (SET 2). Blood samples and biopsies from the middle gluteal muscle were collected before and after each phase of the study and in response to each SET and analyzed for markers of oxidative damage and antioxidant enzyme activity. In both phases, serum Se was higher (P < 0.0001) when horses received a diet with 0.3 than 0.1 mg Se/kg DM. Throughout the 14-wk study, resting activities of muscle glutathione peroxidase (GPx; P = 0.004) and superoxide dismutase (SOD; P = 0.06) were greater in trained horses than in untrained horses. In response to SET 1, serum creatine kinase (CK) activity was lower in trained horses than in untrained horses (P < 0.0001), indicating less muscle damage, but plasma lipid hydroperoxides (LPO) and muscle GPx and SOD activities were unaffected by training or Se. In response to SET 2, trained horses had greater muscle SOD activity (P = 0.0002) and lower serum CK activity (P = 0.003) and showed a trend for lower plasma LPO (P = 0.09) and muscle malondialdehyde (P = 0.09) than untrained horses. Muscle GPx activity did not change in response to SET 2 and was unaffected by training or Se. Results indicate that exercise training lessens muscle damage and improves antioxidant defense following an acute bout of prolonged exercise and was not further enhanced by feeding Se above the NRC requirement.

28 Mitochondrial adaptations to submaximal exercise training in the gluteus medius and triceps brachii of young equine athletes

s / Journal of Equine Veterinary Science 35 (2015) 392e397 395 but the use of electrolyte pastes in races was less common (31%). Analyzing the data set using logistic regression, there was a trend (P 1⁄4 0.10) for metabolic failure to increase 0.66 for each increasing level of alfalfa feeding (0 1⁄4 none, 1 1⁄4 occasional, 2 1⁄4 regular, 3 1⁄4 daily). OR for metabolic failure reduced by 0.10 for each additional ride > 90 km the rider had entered in the last 2 years (P < 0.05). Highest current level of competition and total distance completed over 90 km also approached significance for reducing the risk of metabolic failure. Electrolyte use is common among endurance riders competing at all levels in the UK. In this small survey, experience of horse and rider appeared to have a greater influence on the risk of metabolic failure than electrolyte use or nutrition per se. 28 Mitochondrial adaptations to submaximal exercise training in the gluteus medius and triceps brachii of young equine athletes S.H. White*, L.K. Warren, C. Li, and S. Wohlgemuth University of Florida, Gainesville, FL, USA Exercise training has been shown to enhance mitochondrial biogenesis and efficiency in human and rodent models. We hypothesized that lowto moderate-intensity exercise training would result in similar mitochondrial improvements in skeletal muscle of young horses, and that responses would be muscle dependent. Quarter Horse long-yearlings (mean ± SE, 21 ± 0.2 mo, 410 ± 9 kg) were randomly assigned to either: submaximal exercise training (TR; n 1⁄4 18) comprised of walk-trot-canter exercise in a round-pen or while being ridden 30e45min/d, 3 d/wk; or no controlled exercise (UT; n 1⁄4 6). UT horses were grouphoused on 16-ha pastures, whereas housing for TR horses was split between pasture and stall (~6 h/d). Biopsies were taken from the gluteus medius of all horses (n 1⁄4 24) and from the triceps brachii of a randomly selected subset of TR (n 1⁄4 6) and all UT (n 1⁄4 6) before (wk 0) and after 9 wk of training. Muscle was assessed for activities of cytochrome c oxidase (CCO) and citrate synthase (CS) as indicators of mitochondrial function and number, respectively. Additionally, saponin-permeabilized muscle fibers were analyzed for mitochondrial function via high-resolution respirometry, and data were normalized to mitochondrial number in the sample (CS activity). Data were analyzed using a mixed-model ANOVA. The triceps had greater CS activity (P < 0.0001) and lower CCO activity (P < 0.0001) than the gluteus in all horses; however, enzyme activities were unaffected by time or training. An overall effect of time across both muscle groups and training levels was observed, whereby electron transport system capacity (ETSC) increased (P 1⁄4 0.02), and state 3 respiration (P 1⁄4 0.06) and the respiratory control ratio (P 1⁄4 0.06) tended to increase during the 9-wk observation period. Leak respiration (P 1⁄4 0.01) and state 3 with both complex I and II substrates (GMS; P1⁄4 0.007) were higher across bothmuscle groups in TR compared with UT horses. The gluteus in TR horses appeared to be most greatly affected, as demonstrated by an increase in state 3 with complex I substrates (P 1⁄4 0.04), state 3 GMS (P 1⁄4 0.005), ETSC (P 1⁄4 0.04), and the phosphorylation system control ratio with complex I substrates (P 1⁄4 0.01) from wk 0 to 9. As both young untrained and trained horses exhibited improvements in mitochondrial adaptations over time, these changes could reflect alterations in mitochondria due to growth. Nevertheless, submaximal exercise training appeared to further enhance mitochondrial efficiency in the gluteus medius of young horses.

Influence of fatigue, stress, muscle soreness and sleep on perceived exertion during submaximal effort

The aim of this study was to assess the effects of the Hooper's Index variations (i.e., self-ratings of fatigue, stress, delayed onset muscle soreness (DOMS), and sleep) on rating of perceived exertion during a 10min submaximal exercise training session (RPE-10min) and then check the stability and the internal consistency of RPE-10min. Seventeen junior soccer players took part in this study. The individual Hooper's indices taken before each training session were correlated with RPE-10min during a constant intensity and duration effort (10min) using Pearson product moment correlation. Intraclass correlation (ICC) was used to assess the internal consistency of the RPE-10min. All individual correlations between RPE-10min and quality of sleep and quantity of fatigue, stress, and DOMS were non-significant (p>0.05). No significant correlations were resulted between RPE-10min and Hooper's Index in all athletes. The ICC of RPE-10min was 0.77 thus demonstrating internal consistency. The results of the present study demonstrated the objectivity and utility of RPE as a psychological tool for monitoring training during traditional soccer training. Therefore, the results of the present study suggest that fatigue, stress, DOMS and sleep are not major contributors of perceived exertion during traditional soccer training without excessive training loads. It seems that psychobiological factors other than fatigue, stress, DOMS and sleep may have mediated the 10min exercise perceptual intensity.

Exercise in pulmonary hypertension

Background: Pulmonary hypertension (PH) is a disorder characterized by elevation in mean pulmonary arterial pressure of 25 mmHg or greater at rest or 30 mmHg during exercise. Due to the complex clinical presentation and poor prognosis of PH, exercise or increased physical exertion was thought to be detrimental and hence not recommended in these patients. Although physiotherapists may be required to consider exercise prescription for patients with PH, the safety of exercise for these patients remains unclear.Objective: To describe the evidence regarding effectiveness and safety of exercise training in patients with PH.Results: A total of seven studies which evaluated the effect of exercise training in patients with idiopathic and secondary PH were identified for review. The majority of studies found that sub-maximal exercise training enhanced patients’ exercise capacity and improved their health-related quality of life. Most importantly, none of the studies reported any adverse effects during or after exercise training.Conclusion: Sub-maximal exercise training may have beneficial effects in patients with PH. Therefore, participation in an exercise program and/or supervised rehabilitation program should be encouraged for patients with stable PH.

Safety of early exercise training after elective coronary stenting in patients with stable coronary artery disease

Early exercise after coronary stenting is considered to have a risk of stent thrombosis (ST). We investigate the safety of submaximal exercise training based on the Borg scale from the next day after coronary stenting. We enrolled 2351 patients who underwent successful coronary stenting. They were divided into early exercise training (EET) group (n=865) and control group (n=1486). Submaximal exercise training based on the Borg scale was performed on the next day after coronary stenting and same degree exercise was continued more than two times a week after discharge. Primary endpoint was the incidence of ST. Secondary endpoint was major adverse cardiovascular event (death, myocardial infarction, and stroke), incidence of postoperative complications, and rate of exercise continuation. Exercise training was performed in 800 (92.5%) patients. No serious complication developed during and after exercise. Clinical follow-up data were obtained in 99% patients. At 30 days, there was no significant difference in the incidence of ST (0.58 vs. 0.47%, P=0.73), major adverse cardiovascular event (1.4 vs. 1.3%, P=0.72), and complication rate (6.9 vs. 7.3%, P=0.72). No exercise-related ST was found in either group. The rate of exercise continuation was significantly higher in the EET group (49.3 vs. 28.3%, P<0.001). EET up to submaximal level based on the Borg scale from the day after elective coronary stenting does not increase the incidence of ST or postoperative complications.

Failure of hypoxia to exaggerate the metabolic stress in working muscle following short-term training

This study investigated the effects of hypoxia (experiment 1) and the effects of hypoxia following short-term training (experiment 2) on metabolism in working muscle. In experiment 1, eight males with a peak aerobic power (VO2peak) of 45 +/- 1.7 ml x kg(-1) x min(-1) (x +/- SE) cycled for 15 min at 66.1 +/- 2.1% VO2peak while breathing room air [normoxia (N)] or 14% O(2) [hypoxia (H)]. In experiment 2, nine males with a VO2peak of 43.3 +/- 1.6 ml x kg(-1) x min(-1) performed a similar protocol at 60.7 +/- 1.4% VO2peak during N and during H following 5 days of submaximal exercise training (H + T). Tissue samples extracted from the vastus lateralis before exercise and at 1, 3, and 15 min of exercise indicated that compared with N, H resulted in lower (P < 0.05) concentrations (mmol/kg dry wt) of creatine phosphate and higher (P < 0.05) concentrations of creatine, inorganic phosphate, and lactate, regardless of exercise time. When the exercise was performed at H + T and compared with N, no differences were observed in creatine phosphate, creatine, inorganic phosphate, and lactate, regardless of duration. Given the well-documented effects of the short-term training model on elevating VO2 kinetics and attenuating the alterations in high-energy phosphate metabolism and lactate accumulation, it would appear that the mechanism underlying the reversal of these adaptations during H is linked to a more rapid increase in oxidative phosphorylation, mediated by increased oxygen delivery and/or mitochondrial activation.

Genomics and Sports: Building a Bridge Towards a Rational and Personalized Training Framework

It is now widely acknowledged that several genes influence the athletic performance and it is increasingly being highlighted that a major integration between genetic and environmental factors might contribute towards unveiling the most important determinants of physiology and pathology in humans, allowing the construction of a rational personalized framework that would be applied in both clinical and sport settings [[7], [9]]. The alpha-actinin 3 (ACTN3) gene, which encodes for a protein of the Z disk of myofibers, has been found to be associated with performance in elite athletes, in whom the R allele was more common in sprint and power athletes and the X allele more common in endurance athletes [[15]]. Data in a large sample size have also shown that women with the nonsense allele in ACTN3 are at a disadvantage in the ability to produce high-force isometric strength, but they are at an advantage in developing dynamic muscular strength in response to a progressive resistance training program. Up to 2 % of the variability in the absolute and relative difference in 1-repetition maximum strength and in the baseline elbow flexor isometric strength are attributable to the ACTN3 genotype [[2]]. Turley et al. further confirmed the presence of a substantial genetic influence on acute submaximal exercise and regular endurance training, as maximal oxygen uptake and training response are influenced by multigenetic effects, which account for nearly 40 % and 20 % of the variance, respectively [[13]].

Specificity of training adaptation: time for a rethink?

The key components of any training programme are the volume (how much), intensity (how hard) and frequency (how often) of exercise sessions. These ‘training impulses’ determine the magnitude of adaptive responses that either enhance (fitness) or decrease (fatigue) exercise capacity (Hawley, 2002). A long held view is that the training response/adaptation is directly related to the volume of exercise undertaken (Fitts et al. 1975). However, there is obviously a threshold volume/duration beyond which additional stimuli do not induce further increases in functional capacity. This ‘biological ceiling’ is important because it implies that the regulatory control mechanisms signalling adaptive responses are ultimately titrated by exercise duration (Booth & Watson, 1985). Competitive athletes are all too aware of this phenomenon: many elite performers walk a tightrope between chronic intensive training and inadequate recovery that can culminate in decrements in performance and the ‘overtraining syndrome.’ Biological scientists are also mindful that training volume and adaptation can be dissociated. Over 35 years ago Dudley et al. (1982) demonstrated that rats undertaking intense workbouts for shorter time induced similar increases in the maximal activities of several oxidative enzymes (i.e. cytochrome c) to those observed after more prolonged submaximal exercise training.

Submaximal effort tolerance as a predictor of all‐cause mortality in patients undergoing cardiac rehabilitation

Submaximal effort tolerance is routinely available during cardiac rehabilitation, but its prognostic value in relation to underlying referral diagnosis is not known. Treadmill effort capacity during submaximal exercise training predicts all-cause mortality after cardiac rehabilitation. We followed 600 consecutive patients (450 men and 150 women, mean age 65 years) who were referred to a 12-week outpatient program of cardiac rehabilitation; 37% had a prior myocardial infarction (MI), 44% had a recent percutaneous intervention (PCI), and 39% had history of coronary artery bypass surgery (CABG). There were 48 deaths during a mean follow-up period of 1603 +/- 822 days. By multivariate Cox analysis, exit MET activity was the most significant predictor of all-cause mortality. In this model, each 1 MET increase in exit submaximal effort tolerance was associated with a 34% decrease in mortality (hazard ratio [HR] 0.66, 95% confidence interval 0.56-0.77) alone and 28% decrease after adjustment for age (HR = 0.72, confidence interval 0.60-0.85). Enty MET level also had predictive value. Subgroup analysis revealed that the predictive value of exit METs was limited to patients after recent CABG and with MI. None of the variables predicted death after PCI, in whom mortality was significantly lower than in the other groups. Submaximal effort tolerance at completion of cardiac rehabilitation, and also at entry, is a strong and age-independent predictor of mortality in patients who have had either recent CABG or MI without intervention, but not in patients after recent PCI.

Influences of Acute and Chronic Aerobic Exercise on the Plasma Homocysteine Level

Background and Aims: Elevated plasma homocysteine (PH) levels have been identified as a risk factor for cardiovascular diseases. The aims of this study were to investigate the influences of submaximal acute aerobic exercise and aerobic training on PH levels and lipid profiles. Methods: 69 volunteersubjects (21.12 ± 2.08 years) were randomized to three groups as acute, training and control groups. Examination and blood samples were collected before and immediately after exercise in the acute group and before and 6 weeks later in the training and control groups. Results: A significant increase in PH concentration was recorded immediately after aerobic exercise, compared with baseline values (p = 0.001). Although, in the training group, total cholesterol (p = 0.00) and LDL cholesterol (p = 0.001) decreased significantly after training, no significant changes in PH concentration, HDL cholesterol (p = 0.087) and triglyceride (p = 194) levels were found. Conclusions: It can be said that the PH level increases following submaximal acute aerobic exercise, but does not alter after submaximal aerobic training due to training duration or intensity. Therefore, submaximal aerobic training decreases lipid profiles independent of the PH level.