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Limiting factors for maximum oxygen uptake and determinants of endurance performance
Abstract
In the exercising human, maximal oxygen uptake (VO2max) is limited by the ability of the cardiorespiratory system to deliver oxygen to the exercising muscles. This is shown by three major lines of evidence: 1) when oxygen delivery is altered (by blood doping, hypoxia, or beta-blockade), VO2max changes accordingly; 2) the increase in VO2max with training results primarily from an increase in maximal cardiac output (not an increase in the a-v O2 difference); and 3) when a small muscle mass is overperfused during exercise, it has an extremely high capacity for consuming oxygen. Thus, O2 delivery, not skeletal muscle O2 extraction, is viewed as the primary limiting factor for VO2max in exercising humans. Metabolic adaptations in skeletal muscle are, however, critical for improving submaximal endurance performance. Endurance training causes an increase in mitochondrial enzyme activities, which improves performance by enhancing fat oxidation and decreasing lactic acid accumulation at a given VO2. VO2max is an important variable that sets the upper limit for endurance performance (an athlete cannot operate above 100% VO2max, for extended periods). Running economy and fractional utilization of VO2max also affect endurance performance. The speed at lactate threshold (LT) integrates all three of these variables and is the best physiological predictor of distance running performance.
... Additional factors influence or limit VO 2 max improvements. These include capillary density, hemoglobin concentration, stroke volume, aerobic enzyme activity, and muscle fiber type composition [3]. While training and environmental factors play a crucial role in shaping these adaptations, genetic predisposition significantly influences an individual's baseline VO 2 max and their responsiveness to endurance training. ...
... Maximal oxygen consumption (VO 2 max) is one of the primary determinants of endurance sports performance, as it sets the upper limit for aerobic energy production and an athlete's ability to sustain prolonged efforts [3]. VO 2 max represents the highest rate at which the body can absorb, transport, and utilize oxygen during intense exercise [12]. ...
... Traditionally, athletes and coaches recognize the three classic pillars of endurance sports: maximal oxygen consumption (VO 2 max), anaerobic threshold (AT), and economy of movement (EM), which encompasses running economy, cycling economy, and swimming economy [1]. These factors have been widely established in the literature as primary determinants of endurance performance [2][3][4]. Training plans are designed based on tests that assess each of these pillars, allowing for the establishment of training zones that are continuously monitored and adjusted as adaptations occur and athletic performance progresses [5]. ...
Endurance performance is primarily determined by three key physiological pillars: maximal oxygen uptake (VO 2 max), anaerobic threshold, and economy of movement. Recent research has suggested physiological resilience as a potential fourth dimension, referring to an athlete's ability to sustain performance despite accumulating fatigue. While the role of genetic factors in endurance has been widely studied, their influence on these pillars, particularly on fatigue resistance and long-term adaptation, remains an area of growing interest. This narrative review explores the genomic basis of endurance performance , analyzing genetic contributions to oxygen transport, metabolic efficiency, muscle composition, and recovery. Additionally, it discusses how genetic variability may modulate an athlete's response to training, including aspects of physiological adaptation, injury susceptibility, sleep, and nutrition. The review highlights physiological resilience in the context of endurance sports, discussing its connection to neuromuscular and metabolic regulation. By integrating genetic insights with established physiological principles, this review provides a comprehensive perspective on endurance adaptation. Future research directions are outlined to enhance our understanding of the genetic underpinnings of endurance, with implications for personalized training and performance optimization.
... The three weeks of SIT increased VO2max and the power at the end of the incremental cycling test as well as the average power during SIT sessions to the same extent in vitamin-and placebo-treated participants (see Figure 9). VO2max represents the highest rate at which O2 can be taken up and utilized during intense physical exercise (Bassett & Howley, 2000). It depends on the integrated ability of pulmonary, cardiovascular, and skeletal preprint (which was not certified by peer review) is the author/funder. ...
... Thus, any step(s) in this functional cascade can be rate limiting for VO2max. Classically, VO2max is considered to be limited by factors that determine O2 delivery to working muscles (Bassett & Howley, 2000;Lundby et al., 2017), although the O2-utilizing capacity of mitochondria in exercising muscles might set the limit in untrained individuals (Gifford et al., 2016). In a recent study on healthy men and women, six weeks of SIT increased VO2max by ~10% and this could be explained by improved O2 delivery due to increases in both the total circulation blood volume and the left ventricular volume (Eriksson et al., 2024). ...
... Importantly, this implies ROS-independent mechanisms underlying the traininginduced improvement of O2 delivery, whereas the increase in mitochondrial protein abundance was triggered by ROS-dependent mechanisms. Nevertheless, the SIT-induced increase in mitochondrial content in muscle will improve endurance exercise performance, for instance, due to decreased lactate production at a given submaximal power output, hence limiting the depletion of muscular glycogen stores (Coyle et al., 1988;Bassett & Howley, 2000). ...
Sprint interval training (SIT) is a time-efficient type of endurance training that involves large type 2 muscle fibre recruitment. Effiective antioxidant supplementation may mitigate positive training adaptations by limiting the oxidant challenge. Our aim was to test whether SIT affiects type 2 more than type 1 muscle fibres, and whether the training response is mitigated by antioxidant treatment. Young men performed three SIT sessions (6 × 30 s all-out cycling) per week for three weeks while treated with antioxidants (vitamin C, 1 g/day; vitamin E, 235 mg/day) or placebo. Vastus lateralis biopsies were taken to measure (i) activation of genes for reactive oxygen/nitrogen species (ROS) sensors and inflammatory mediators with quantitative RT PCR and (ii) fibre type-specific proteome adaptations using mass spectrometry-based proteomics. Vitamin treatment decreased the upregulation of genes for ROS sensors and inflammatory regulators during the first SIT session. The three weeks of SIT caused generally larger proteome adaptations in type 2 than in type 1 fibres, and this included larger increases in abundance of proteins involved in mitochondrial energy production. Vitamin treatment blunted the SIT-induced proteome adaptations, whereas it did not affiect the training-induced improvement in maximal cycling performance. In conclusion, (i) the large type 2 fibre recruitment and resulting proteome adaptations are instrumental to the effiectiveness of SIT, and (ii) antioxidant supplementation counteracts positive muscular adaptations to SIT, which would blunt any improvement in submaximal endurance performance, whereas it does not affiect the improvement in maximal cycling performance, where O2 delivery to muscle would be limiting.
... Furthermore, exercise intensity at the LT inflection point has become the most important determinant of aerobic fitness [14,15] and is often used by coaches to evaluate athletes' training status or to establish training intensities. Additionally, running velocity at LT (vLT) and running economy (RE) are more sensitive than maximal oxygen consumption (V̇O2 max ) in predicting aerobic performance [16] and are also indicative of soccer players' endurance characteristics and their playing standards [17]. The most commonly used methods for detecting LT are visual inspection (VI) [18] and log-to-log transformation [19]. ...
... Field testing for aerobic power is associated with game performance [22] and has gained acceptance in evaluating aerobic fitness in youth soccer [23]. However, these tests have not been optimized [24] and lack sensitivity for predicting aerobic performance [16]. Moreover, comparisons and assessments of readiness to meet the playing standards of professional soccer players are difficult because lactate profiling is scarce in youth athletes. ...
... Despite the superiority of the professional players in incremental testing, youth players exhibited a significantly higher V̇O2 max. This finding aligns with evidence from other studies, suggesting that other factors might be more sensitive indicators of superior aerobic performance [16,17], such as shifts in lactate accumulation at higher intensities. According to an extensive review by Poole et al. (2021) [36], the mechanism that most likely regulates the relationship between exercise intensity and increases in muscle and blood lactate is the mitochondrial reticulum volume density. ...
The lactate threshold (LT) and the associated running velocities are important markers used to define physical readiness and prescribe exercise intensity in athletes. This study examined blood LT during maximal cardiopulmonary exercise testing using four methods: visual inspection, log-to-log transformation, the Dmax method, and the 4 mmol/L fixed blood lactate accumulation (FBLA) method. The participants included 96 soccer players, comprising 52 professional (27.37 ± 5.67 years) and 44 elite youth players (16.20 ± 0.8 years). A total of 554 capillary blood lactate samples were analyzed. Bland-Altman and ICC analyses for running velocities, determined using the four LT detection methods, demonstrated poor agreement in both groups. Results indicated that the youth players had significantly (p < 0.05) higher V̇O2 max (59.89 ± 5.6 mL·kg −1 ·min −1) compared to the professional players (56.43 ± 4.81 mL·kg −1 ·min −1). However, the professional players had significantly better running performance and running economy. A two-way ANOVA revealed a main effect of playing standard, with professional players exhibiting significantly higher 4 mmol/L FBLA LT compared to youth players. A mixed-design ANOVA indicated a significant (p < 0.01) interaction, with the youth exhibiting higher lactate accumulation only after completing the 18 Km/h stage. Therefore, youth and professional players should not use the different LT concepts interchangeably. Additionally, the 4 mmol/L FBLA LT method appears to be more robust for youth soccer players.
... However, because the intensity associated with V O 2 max cannot be sustained for more than a few minutes during a long-distance event, a percentage of V O 2 max is maintained throughout the race. In this context, the V O 2 sustained during a long event is determined by both the V O 2 max and the percentage of it that can be sustained [10]. These characteristics are typically measured during a maximum incremental test using lactate or ventilatory thresholds [10]. ...
... In this context, the V O 2 sustained during a long event is determined by both the V O 2 max and the percentage of it that can be sustained [10]. These characteristics are typically measured during a maximum incremental test using lactate or ventilatory thresholds [10]. In cycling, another test called functional power threshold (FTP) has also been proposed to determine the highest mean power output that can be sustained over extended periods, providing a more feasible and cost-effective alternative to the more labor-intensive and expensive lactate or ventilatory threshold tests. ...
... Regarding overall race time, V O 2 max is the best variable associated with it; additionally, V O 2 max was able to explain 66.7% of the race performance. These data are not surprising given that high V O 2 max values have been extensively demonstrated to be required for good performance in longterm races [10]. ...
Purpose
Previous study has shown that cycling is the most predictive modality in the Ironman 70.3 triathlon distance. As a result, understanding the physiological and anthropometric variables that are mostly closely related to cycling performance can help coaches and athletes to direct their training programs. This study aimed to investigate the physiological, anthropometric, and general training characteristics influencing overall race time and cycling split time in Ironman 70.3. The present study also investigated the significance of body composition as a performance-related variable.
Methods
A questionnaire was used to assess training characteristics in 12 athletes (six men and six women), body composition in dual X-ray absorptiometry, and physiological variables in an incremental cardiopulmonary test. Ironman 70.3 São Paulo–Brazil 2023 was completed by all participants. The relationship between performance and the variables measured were investigated, and a multiple regression model for cycling split time and overall race time was developed.
Results
Functional threshold power (FTP) can predict cycling split time in Ironman 70.3 (r² = 0.638, p = 0.002). Maximal oxygen uptake (O2max) (r² = 0.667, p = 0.001) can predict overall race time. FTP and O2max are also strongly related to lean mass and fat mass percentage.
Conclusion
While FTP is the most important predictor of cycling split time, O2max is the most important predictor of overall race time in an Ironman 70.3. Furthermore, because body composition (fat mass %) and muscle mass (kg) are variables strongly related to FTP and O2max, we recommend that coaches and athletes consider to conduct a body composition assessment.
... Връзката на VO 2 max с размера на тялото изисква корекция на измерванията на VȮ 2 max, отчетени в ml/kg/min. Съществените фактори, допринасящи за индивидуалните вариации във VO 2 max, включват: размер на тялото, възраст, пол, генетични фактори, обем на червените кръвни клетки и физически упражнения [7]. Проучвания предполагат, че VȮ 2 max намалява с 3-6% на всеки 10 години, като се започне от 20-30-годишна възраст и с > 20% на всеки Introduction Hodgkin's disease or Hodgkin's lymphoma (HL) is a malignant disease of the lymphatic tissue, clinically presenting most often with lymphadenomegaly. ...
... The relationship of V O 2 max to body size requires correction of V O 2 max measurements reported in ml/kg/min. Significant factors contributing to individual variation in V O 2 max include body size, age, sex, genetic factors, red blood cell volume, and exercise [7]. Studies suggest that V O 2 max declines by 3-6% every 10 years starting at age 10 години след 70-годишна възраст [8]. ...
Hodgkin's lymphoma is a systemic disease of the lymphatic tissue that most commonly affects adolescents and young adults. Modern treatment of the disease aims at long-term remission in patients. During this process, some patients develop complications that require timely diagnosis and treatment. It is fundamental to ensure continuity between pediatric oncologists, pulmonologists, and cardiologists, pediatricians on the one hand, and specialists in the relevant field treating adult patients. Keeping and maintaining accurate patient medical data serves as a springboard for screening adolescents and young adults in remission after treatment for Hodgkin's lymphoma. The treatment methods (radiation, chemotherapy, etc.) have different mechanisms of action on the disease and, accordingly, different potential early and late complications. The role of functional breathing studies and cardiopulmonary stress tests with exercise in this group of patients can explain the etiology of clinical complaints, assess the functional status and effect of treatment, as well as timely diagnosis of complications during the treatment process with the aim of early cardio rehabilitation and achieving durable clinical remission.
... Despite this, current findings indicate that 2-3 weeks of short-term RST with BFR does not alter VO 2max or further enhance peak aerobic power compared to Non-BFR (Giovanna et al., 2022;McKee, Girard, Peiffer, Hiscock, et al., 2024). However, VO 2max is primarily limited by systemic oxygen delivery and current research has not investigated the impact of RST with BFR on submaximal endurance performance, which may better reflect peripheral aerobic adaptations (Bassett & Howley, 2000). Six weeks of running RST (1-3 × 3-5 20-m sprints with 20 seconds passive recovery) for competitive volleyball players increased VO 2 at VT 1 (+5%) and VT 2 (+11%) along with VT 2 speed (+11%). ...
... Six weeks of running RST (1-3 × 3-5 20-m sprints with 20 seconds passive recovery) for competitive volleyball players increased VO 2 at VT 1 (+5%) and VT 2 (+11%) along with VT 2 speed (+11%). Delayed onset of anaerobic thresholds and improved submaximal endurance performance following RST could be explained by enhanced skeletal muscle buffering and oxidative capacity, which have also been observed with BFR training (Bassett & Howley, 2000;Mckee et al., 2023). ...
... It represents a measure of cardiorespiratory fitness (CRF) and has a strong inverse relation with all-cause mortality and cardiovascular diseases [14][15][16]. VO2max also has an important relationship to endurance performance among athletes, often being cited as the most important single factor-or among the most important factors-in predicting race performance [17][18][19]. Pulse oximeters can non-invasively measure the amount of oxygen bound to hemoglobin based on how light reflects off the blood cells when broadcast from the device. Devices with pulse oximeters to measure BOS can also be used to monitor cardiorespiratory functions, especially in people with pulmonary diseases. ...
... In addition to the role of VO2max in personal health, it is also an important measure for endurance athletes. VO2max is among the most important single measures to determine performance in an endurance event and is considered by many to be the single most important metric in determining performance [17][18][19]. Having the ability to know an athlete's VO2max allows for improved training programs to be developed that are tailored to the athlete's specific fitness level. ...
Introduction: As wearable technology becomes increasingly popular and sophisticated, independent validation is needed to determine its accuracy and potential applications. Therefore, the purpose of this study was to evaluate the accuracy (validity) of VO2max estimates and blood oxygen saturation measured via pulse oximetry using the Garmin fēnix 6 with a general population participant pool. Methods: We recruited apparently healthy individuals (both active and sedentary) for VO2max (n = 19) and pulse oximetry testing (n = 22). VO2max was assessed through a graded exercise test and an outdoor run, comparing results from the Garmin fēnix 6 to a criterion measurement obtained from a metabolic system. Pulse oximetry involved comparing fēnix 6 readings under normoxic and hypoxic conditions against a medical-grade pulse oximeter. Data analysis included descriptive statistics, error analysis, correlation analysis, equivalence testing, and bias assessment, with the validation criteria set at a concordance correlation coefficient (CCC) > 0.7 and a mean absolute percentage error (MAPE) < 10%. Results: The Garmin fēnix 6 provided accurate VO2max estimates, closely aligning with the 15 s and 30 s averaged laboratory data (MAPE for 30 s avg = 7.05%; Lin’s concordance correlation coefficient for 30 s avg = 0.73). However, it failed to accurately measure blood oxygen saturation (BOS) under any condition or combined analysis (MAPE for combined conditions BOS = 4.29%; Lin’s concordance correlation coefficient for combined conditions BOS = 0.10). Conclusion: While the Garmin fēnix 6 shows promise for estimating the VO2max, reflecting its utility for both individuals and researchers, it falls short in accurately measuring BOS, limiting its application for monitoring acclimatization and managing pulmonary diseases. This research underscores the importance of validating wearable technology to leverage its full potential in enhancing personal health and advancing public health research.
... The evaluation of CRF is usually performed by an incremental exercise test until exhaustion 8 . Testing requires up to 1 h and specialised equipment to assess O 2 /CO 2 in expired volume through a mask connected to specific sensors 9 . ...
... A total of 242 children and adolescents (102 females) were recruited from the primary health care system who were in a state of health compatible with the performance of a physical exhaustion test. The mean age was 12.5 ± 2.6 (range [8][9][10][11][12][13][14][15][16]. 51.6% were overweight or obese (48.5% male and 55% female) ( Table 1). ...
Cardiorespiratory fitness is the most important variable related to health and a strong predictor of mortality. However, it is rarely used in clinics due to costs, specialized equipment, space needs, and the requirements of expert staff such as an exercise physiologist, physician, or other health professional. This work aims to validate and test the reliability of a submaximal step test to estimate VO2max of 8-to 16-year-old pediatric populations as a simple and low-cost tool for clinical practice. A cross-sectional study included 242 children and adolescents (42.1% girls) aged 8–16. Cardiorespiratory fitness was determined by a maximal incremental test on a treadmill until exhaustion. The step test entailed maintaining a steady pace of 22 steps per minute for 3 min (60 bpm), with the heart rate being recorded at the end of the test. Nutritional status was computed through BMI z-score. A multiple linear regression model validated the step test and developed a new equation to predict VO2max, including the third-minute heart rate, weight, and height. The reliability among predicted and measured VO2max was assessed by Bland-Altman analysis. The mean age was 12.5 ± 2.6; 51.6% were overweight or obese. The cardiorespiratory fitness measured as VO2max was 35.01 ± 0.58 ml·min-¹·kg⁻¹. A robust correlation was observed between the predicted VO2max from the step test and the measured VO2max (r = 0.86, p < 0.001). Bland-Altman analysis indicated statistical concordance between predicted and measured VO2max. Our findings indicate that the step test protocol is valid and reliable for estimating VO2max in children and adolescents. Furthermore, the predictive equation is suitable for application among children aged 8–16.
... athletes. An athlete›s performance in performing activities usually lasts for 5 minutes or more and requires an intensity approximately equal to the VO2max capacity, this is related to the capacity of the circulatory and respiratory systems to supply fuel and resynthesize adenosine triphosphate (ATP) through oxidative metabolism (Bassett and Howley 2000;Joyner and Coyle 2008). Therefore, endurance performance is determined by the level of maximum oxygen volume (VO2max). ...
... Previous studies (Bassett and Howley 2000;Joyner and Coyle 2008;Pasa et al. 2022;Rizal and Segalita 2018;Arimbi, Usman, and Wahid 2022;Nyawose et al. 2022;Mukti et al. 2021) have examined the effect of supplement use on athlete fitness levels tend to focus on energy metabolism indicators of aerobic athletes, water polo players, and increased physical activity and use the Citrulline variable. However, research examining L-Arginine Supplementation in West Kalimantan Muaythai Athletes can be considered an important step to explore the potential for activities or fitness levels that have not been studied before. ...
This study aims to determine the extent of the effect of L-Arginine amino acid supplementation on oxygen saturation and lactic acid levels at the fitness level (VO2Max) of West Kalimantan muaythai athletes. High lactic acid levels can be an indicator of fatigue in athletes after undergoing a physical fitness test. This type of quantitative descriptive research used a randomized group pretest-posttest group design sampling method. The subjects in the study used were male athletes on the West Kalimantan Muaythai team who will be prepared for the 2024 International Student Muaythai Championship. In this study, the subjects were divided into two groups, the first group was given a placebo and the second group was given the amino acid L-arginine. Each group was given the same treatment, namely a physical fitness test to determine the VO2Max level using a bleep test. Before and after carrying out the physical fitness test, the subjects were checked for oxygen saturation, and blood lactic acid samples were taken. The results showed that L-Arginine supplementation had a positive effect in helping to maintain optimal oxygen saturation in the body and reducing the accumulation of blood lactic acid levels that can cause fatigue in Muay Thai athletes. This shows the significant role of L-arginine supplementation in helping to enhance physical endurance performance and speed up recovery during and after physical activity.
... Notably, during all these short-term responses (at normoxia), the cardiorespiratory adjustments are essential to managing O 2 demands from several cells, tissues, and organs (10)(11)(12)(13). However, in a hypoxic environment, where the O 2 availability is decreased, the V _ O 2max and endurance performance are markedly reduced (14)(15)(16)(17)(18)(19)(20)(21); nevertheless, the evidence is not completely clear, showing the precise mechanism that explains the exercise performance deterioration in this environment (22). Although physical performance deterioration during hypoxia is undeniable, the mechanisms explaining this phenomenon are not fully described, leading to various hypothetical scenarios. ...
... Thus, during exercise, the sympathoexcitation contributes to venous contraction, and together, active muscles, which can function as a pump, promote an increase in the cardiac preload; on the other hand, the exercise-dependent parasympathetic overactivation could contribute to facilitated O 2 uptake of heart muscle during physical exertion. Notably, during a reduction of O 2 availability, the aerobic capacity is markedly reduced (14)(15)(16)(17)(18)(19)(20)(21). Nevertheless, there are no severe changes in the left ventricle chamber diameter during hypoxia. ...
The cardiorespiratory and metabolic response to exercise has been associated with meeting the organism′s metabolic demands during physical exertion. Of note, an incremental exercise is characterized by i) cardiodynamic phase related to cardiac output enhancement mainly determined by a positive chronotropic response, ii) ventilatory threshold one, associated with a significant contribution of cardiovascular and pulmonary ventilation, and iii) ventilatory threshold two, correlated with a tremendous increase in breathing and metabolic responses to exercise. Notably, it has been shown that the ventilatory response to exercise increases concomitantly with the release and accumulation of metabolites (i.e., lactate released from skeletal muscle). The principal peripheral chemoreceptors are the carotid bodies (CB), allocated into the carotid bifurcation and demonstrated to respond to several stimuli, triggering autonomic and ventilatory responses. Indeed, in past and recent years, it has been shown that CB could respond to lactate in in vitro and in vivo preparation, eliciting an increase in CB activity and ventilation. However, not all evidence indicates that peripheral chemoreceptors respond to lactate. Thus, considering that CB chemoreceptors' role in lactate-dependent breathing response is not completely clear and their potential preponderance as metabolic sensors during exercise has not been thoroughly explored, the present review was focused on the possible role of CB chemoreceptors as metabolic sensors during physical exertion in a physiological context, proposing it as a new actor in exercise physiology.
... These assessments are achieved through continuous or periodical monitoring of physiological biomarkers [35]. Common biomarkers used to assess health and fitness levels include VO 2max [36], where higher levels indicate better athletic performance and cardiovascular fitness; resting heart rate (RHR), with lower RHR signifying higher cardiovascular fitness [37]; heart rate variability (HRV), with higher HRV indicating better cardiovascular health [38]; and more intricate measurements that concern underlying longterm variations in heart rate, such as detrended fluctuation analysis (DFA), which has proven to be useful for monitoring physical responses to exercise intensities [39]. ...
Predicting performance outcomes has the potential to transform training approaches, inform coaching strategies, and deepen our understanding of the factors that contribute to athletic success. Traditional non-automated data analysis in sports are often difficult to scale. To address this gap, this study analyzes factors influencing athletic performance by leveraging passively collected sensor data from smartwatches and ecological momentary assessments (EMA). The study aims to differentiate between 14 collegiate volleyball players who go on to perform well or poorly, using data collected prior to the beginning of the season. This is achieved through an integrated feature set creation approach. The model, validated using leave-one-subject-out cross-validation, achieved promising predictive performance (F1 score = 0.75). Importantly, by utilizing data collected before the season starts, our approach offers an opportunity for players predicted to perform poorly to improve their projected outcomes through targeted interventions by virtue of daily model predictions. The findings from this study not only demonstrate the potential of machine learning in sports performance prediction but also shed light on key features along with subjective psycho-physiological states that are predictive of, or associated with, athletic success.
... The findings of the present study imply that young talented adolescents from the high hill population, having polygenic endurance profiles linked with higher TGS could be selected and given appropriate training in endurance-related sports activities with prospects of competing in Olympics and other sports events held in high-altitude environment. Earlier studies have shown that whole body physiological variables related to O 2 consumption are influenced by the level of training of the individual [68][69][70][71]. It has been shown that long-term endurance training in a coordinated fashion impacts muscle epigenetics and affects thousands of methylation sites and genes associated with improvement in muscle function and health [72]. ...
... 15 CRF is indicated by maximal oxygen uptake per minute (VO2max) as the international standard and primarily determined by the efficiency of mechanisms supplying active muscles with oxygen from the air. 16 The basic unit of measuring maximal oxygen uptake is its absolute value expressed in liters or milliliters per minutes. However, the absolute value is highly affected by body mass (BM), so it is often expressed as relative value in milliliter/kg/minutes . ...
Search aim:
The aim of the study is to describe the associations between body composition of Egyptian pre-school children and their cardiorespiratory fitness
Curriculum used: Descriptive method
Research Sample and Characteristics:
The research sample was randomly chosen and consisted of (400) children who are members of the basic sample from pre-school children in kindergarten stage in Qaliubiya Governorate
The most important results:
69.8 % of pre-school children are of abnormal weight (43% obese, 21.5% over-weight &5.3% under-weight). Pre-school children showed poor CRF and there is a strong inverse correlation between body composition measurements like ( body fat & water content) and respiratory fitness measurements like (VC, FVC, FEV1, PEF and VO2max).On the contrary , there is strong direct correlation between body composition and SBP & DBP , MAP& resting pulse)(P<0.05).
Conclusions: There is poor cardio-respiratory fitness among Egyptian pre-school children.
... The amount of exercise an individual is able to perform is dependent on their aerobic capacity and exercise tolerance (17). Aerobic capacity is limited by the ability of the cardiovascular system to deliver oxygen to the working musculature (18). In addition to aerobic capacity, lactate threshold, defined as the exercise intensity at which blood lactate concentrations accumulate faster than they can be removed, also decreases with age (19). ...
... Running economy (RE) refers to the energy or oxygen cost associated with submaximal, steady-state running (1). RE is an important contributor to endurance performance alongside maximal oxygen consumption (V O 2max ), and is considered a more accurate predictor of distance running performance among elite endurance athletes than V O 2max (2). ...
Purpose
This study examined the separate and combined effects of advanced footwear technology (AFT) and acute ingestion of a ketone monoester on running economy (RE), time-to-exhaustion (TTE), and other metabolic and cardiorespiratory parameters.
Methods
In a four-condition, placebo-controlled, randomized crossover design, 18 middle- and long-distance runners (male/female, 10/8, V̇O 2peak : 59.4 ± 7.2 mL·kg ⁻¹ ·min ⁻¹ ) completed five 8 min stages of submaximal running (male: 10–14 km·h ⁻¹ ; female: 9–13 km·h ⁻¹ ) on a motorized treadmill, immediately followed by a ramp test to volitional exhaustion. Participants consumed 500 mL of either a 10% carbohydrate solution (CHO) or 500 mg·kg ⁻¹ body mass of an (R)-3-hydroxybutyl (R)-3-hydroxybutyrate ketone monoester with flavored water (KME) 20 min before exercise, and an additional 300 mL of the 10% carbohydrate solution or 250 mg·kg ⁻¹ body mass of KME during exercise, while wearing either Nike Pegasus Turbo (PEG) or Nike ZoomX Vaporfly Next% 3 (VAP) running shoes. The four randomized conditions were PEG+CHO, PEG+KME, VAP + CHO, and VAP + KME.
Results
RE was significantly improved during the third and fourth submaximal running stages in VAP + CHO and VAP + KME compared to PEG+CHO and PEG+KME (all P < 0.05; ES = 0.53-0.84). RE was also improved during the fifth submaximal running stage in VAP + KME compared to PEG+CHO, and in VAP + CHO and VAP + KME compared to PEG+KME (all P < 0.05; ES = 0.56-0.66). No differences in RE were found between CHO and KME conditions. TTE was significantly longer in VAP + CHO (381 ± 125 s) than PEG+CHO (356 ± 140 s; ES = 0.18, P = 0.023) and PEG+KME (329 ± 131 s, ES = 0.40, P < 0.001) and in VAP + KME (375 ± 125 s) than PEG+KME (ES = 0.35, P < 0.001).
Conclusions
AFT, but not the acute ingestion of a ketone monoester, improved the RE of trained male and female middle- and long-distance runners at submaximal running speeds.
... The mechanisms underlying the decline in CRF are complex. Abnormal CRF may be associated with multiple factors, including maximal cardiac output, arterial oxygen content, the proportion of cardiac output directed to exercising muscles, and the muscles' capacity to utilize oxygen 37 . Impairment in any of these processes can lead to a reduction in CRF. ...
Previous studies have found a significant association between type 2 diabetes (T2DM) and impaired cardiopulmonary fitness (CRF); however, little evidence was shown in patients after percutaneous coronary intervention (PCI). This study aimed to evaluate the independent effects of T2DM on CRF in patients who have undergone successful percutaneous coronary intervention (PCI) and received guideline-directed medical therapy. Additionally, we explored whether this association is influenced by factors such as demographic features, physical activity level, duration of diabetes, time from index PCI, and history of occlusion myocardial infarction. We retrospectively analyzed data from post-PCI patients who consecutively visited the Cardiac Rehabilitation Center at Beijing Anzhen Hospital between September 2023 and July 2024. To isolate the impact of T2DM on cardiovascular fitness, we implemented strict exclusion criteria for confounding comorbidities, particularly heart failure. Cardiorespiratory fitness was quantified through gold-standard measures: peak oxygen uptake (VO2max) and metabolic equivalents (METs). Baseline characteristics were compared between patients with T2DM and non-diabetic patients (DM group vs. non-DM group). A multivariable regression model was used to evaluate the independent effect of T2DM on CRF, adjusting for confounding factors such as demographic features, physical activity level, duration of diabetes, time since index PCI, and residual comorbidities. Subgroup analyses and interaction tests were performed to assess the impact of T2DM across different subgroups. 201 patients (150 non-DM and 51 DM patients) were included in the final analysis. Hypertension was significantly more prevalent in DM patients (68.6 vs. 42.7%, p = 0.001), while other comorbidities, anthropometric measurements, lifestyle factors, and time from index PCI showed no significant differences between groups (all p > 0.05). Multivariate logistic regression analyses demonstrated significant negative associations between T2DM and both VO2max and METs. After adjusting for basic demographic and lifestyle factors (Model 1), T2DM was inversely associated with VO2max (β=−98.3, 95% CI −193.4 to −3.3, p = 0.044) and METs (β=−0.4, 95% CI −0.8 to −0.0, p = 0.05). These negative associations remained robust and became stronger in Model 2, which further adjusted for physical activity status, hypertension, hyperlipidemia, history of occlusion myocardial infarction, time from index PCI, DM duration, and using beta-blockers, showing more pronounced inverse relationships with both VO2max (β=−212.3, 95% CI −389.4 to −35.3, p = 0.02) and METs (β=−0.9, 95% CI −1.6 to −0.2, p = 0.014). Subgroup analyses indicated consistent inverse associations, with no significant effect modification based on sex, age, body mass index (BMI), time since the index PCI, physical activity status, or a history of occlusion myocardial infarction. Our study demonstrates that T2DM is an independent negative predictor of CRF in post-PCI patients, with consistent findings across various subgroups and robust results after adjusting for confounding factors. These findings underscore the importance of CRF assessment in post-PCI patients and highlight the need for targeted interventions to improve CRF in individuals with T2DM.
... Submaximal V O , measured during steady-state running, serves as a proxy for running economy and reflects the efficiency of neuromuscular and metabolic systems under controlled conditions. Previous research has shown that improved running economy is associated with refined motor patterns and enhanced performance, suggesting that sub-maximal V O may play a role in reducing variability during repetitive tasks [23,24]. ...
This study investigates the relationship between total running experience, defined as cumulative years of running multiplied by weekly mileage, and variability in lower leg joint kinematics during treadmill running. Twenty-seven male athletes participated, running while kinematic and kinetic data were collected. Linear regression revealed significant negative correlations between total running experience and variability in both knee and ankle joint range of motion (ROM). Specifically, ankle ROM variability (p = 0.001, R2 = 0.35) and knee ROM variability (p = 0.002, R2 = 0.32) were reduced in runners with more experience. A stepwise regression model further identified ankle ROM variability as a significant predictor (p = 0.033), explaining 44.25% of the variance in total running experience. A significant positive correlation between running experience and instantaneous vertical loading rate (IVLR) (p = 0.025, R2 = 0.15) suggests that more experienced runners generate higher load rates. These findings indicate that more experienced runners exhibit more consistent and stable movement patterns, reflecting refined motor control. The results support the hypothesis that greater running experience is associated with reduced variability in movement patterns within a controlled environment, providing insights into the mechanisms that could contribute to enhanced performance and injury prevention.
... VO 2 Max is strongly influenced by genetic factors, and late-stage training may not significantly enhance it [35,45]. While past studies have shown that increases in VO 2 Max are influenced by factors beyond genetics, such as the cardiorespiratory system's ability to deliver oxygen to exercising muscles [46], improvements in blood oxygen content [19,47], and exercise economy [48], altitude training's impact on VO 2 Max remains unclear. Additionally, high-intensity interval training (HIIT) has shown significant effects on hematological indices but a lesser impact on VO 2 Max [49]. ...
Purpose: This study systematically evaluated the effects of altitude training on athletes' aerobic capacity, focusing on optimal training modalities and intervention durations. Methods: Eight databases (CNKI, CSPD, PubMed, Ovid Medline, ProQuest, Cochrane Library, Embase, and Scopus) were searched for randomized controlled trials on altitude training and aerobic capacity following PRISMA guidelines, covering publications up to 15 October 2024. The risk of bias was assessed using Cochrane tools, and a meta-analysis was conducted using Review Manager 5.4 with a random-effects model. Sensitivity and subgroup analyses were performed to identify heterogeneity and influencing factors. Results: Thirteen studies involving 276 participants (aged 18-35) were included. Meta-analysis revealed that compared to low-altitude training, altitude training significantly increased hemoglobin (SMD = 0.7, 95% CI: 0.27-1.13, p = 0.03) and hemoglobin mass (SMD = 0.49, 95% CI: 0.1-0.89, p = 0.16) but had no significant effect on maximal oxygen uptake (SMD = −0.13, 95% CI: −1.21-0.96, p = 0.68). Altitude training also improved performance in trial tests (SMD = −28.73, 95% CI: −58.69-1.23, p = 0.002). Sensitivity analysis confirmed the robustness of hemoglobin and trial test results. Subgroup analysis showed that the "live high, train high" (LHTH) approach and interventions lasting longer than three weeks were most effective in enhancing aerobic capacity. Conclusions: Altitude training improves athletes' aerobic capacity by enhancing hematological indicators and trial test performance, though its impact on maximal oxygen uptake is minimal. LHTH and interventions exceeding three weeks yield superior outcomes. However, the findings are limited by the number and quality of the available studies.
... As outlined in the results, both the FAST and FED groups experienced significant increases (p < 0.05) from pre to post in VO2 Max (see Fig. 10 and Table XI), functional threshold power (see Fig. 11) and 90-minute endurance power (see Fig. 12). These increases would all benefit endurance performance outcomes (Bassett & Howley, 2000;Sørensen et al., 2019). Both groups also displayed similar deceases in blood lactate from pre to post which again would be beneficial towards improved performance (see Fig. 9 and Table X) However, when FATMAX test results were analysed in both groups, peak fat oxidation had increased significantly in the FAST group (p < 0.05) from pre to post but decreased in the FED group from pre to post. ...
Background: Combining training stimuli with nutritional interventions to maximise the training effect has become the topic of numerous research studies and reviews. The Sleep Low Train Low (SLTL) protocol has become popular amongst endurance athletes as a method of increasing fat oxidation and thereby reduce glycogen dependence in events in excess of 90 minutes. The SLTL protocol was adopted for this study. Purpose: It was hypothesised that implementing a 12-week SLTL protocol would increase fat oxidation and beta-hydroxybutyrate (BHB) production during exercise without negatively effecting performance. Methods: 25 women who are endurance trained were recruited. 21 women (mean age 41.9 years +/- 7 years) completed the 12-week training intervention. 12 incorporated a sleep low train low element, while 9 were pre-fuelled for all sessions (pre & post testing consisted of a FATMAX/VO2 max test, 20-minute functional threshold power test & 90 minute endurance power test on a bike ergometer). Menstrual cycle (MC) phase and function where appropriate were established, tracked and accounted for using questionnaires/test data sheets and morning oral temperature. Results: Analysis highlighted a significant increase in mean peak fat oxidation (PFO in g/min) (p < 0.05) and BHB production @90watts (p < 0.05) from pre to post within the FAST group. Also, the FAST group experienced a significant change in PFO when compared to the FED group from pre to post (p < 0.05). The FED group experienced a reduction in PFO, but this was not significant (p = 0.21). BHB production in the FED group reduced significantly at rest, at 60 watts and 90 watts (p < 0.05) from pre to post. Blood lactate adaptations were similar in both groups with the FAST group exhibiting a significant decrease in blood lactate at 120 watts and 150 watts (p < 0.05) with the FED group displaying a significant decrease at 90 watts and 150 watts (p < 0.05). VO2 max and 90-minute endurance power significantly improved from pre to post (FASTED p < 0.05, FED<0.05) in both groups. Functional Threshold Power (FTP) increased significantly in the FAST group (p < 0.05) but the increase in the FED group (p = 0.11) was not significant. The results of this study suggest that adopting a 12-week Sleep Low Train Low protocol in conjunction with regular high-intensity training significantly increases fat oxidation and BHB production in women who are recreationally endurance trained without negatively impacting performance.
... However, an increase evidences that suggest not only the lactate threshold but also the exercise economy -an energy cost (VO2) of sub maximal exercise-are important determinants of an individual potential in endurance exercise [2]. It has been reported a limitation in the ability of human beings to improve their maximal oxygen uptake of endurance performance [3]. Alternatively, the VO2max. ...
This case study was aimed to study and establish the physiological variables caused by incremental endurance training of one sub-athletic male subject. It was designed to test the lactate threshold [LT], economy and maximal oxygen uptake (VO2max.) throughout two distinct parts of incremental endurance exercise using cycling ergometer. in contrast to the main hypothesis that was suggesting; the lactate threshold, the point of sudden rise in blood (systemic) lactate during incremental endurance exercise will have a fatiguing effect on performance and would not allow researcher to ascertaining a true VO2 max. However, the main results indicated lactate threshold [LT] taken place at work rate of 120 (w) represents 66.5% of maximum subject’s heart rate, obviously it did not affect the true VO2 max. result. So, a combination of factors may explain the variation of lactate threshold. Or rather, that lactate does accumulate as [LT] has variable effects on the outcome of subject’s endurance performance. That is to say, the uneconomical increase in power expenditure (economy), in addition to other metabolic determinants.
... In laboratory conditions, task failure in cycling is induced by means of time-to-exhaustion and maximal graded exercise tests. In both instances, the reasons for stopping the exercise have been extensively studied from a physiological perspective (Åstrand & Saltin, 1961;Bassett & Howley, 2000;Duncan et al., 1997). If the availability of energy substrate is compromised (Hargreaves & Spriet, 2020), or if there is a reduction in oxygen supply (Amann & Calbet, 2008), metabolic acidosis occurs, and the individual is unable to maintain exercise intensity (Debold et al., 2016). ...
Cycling challenges athletes to their physiological and psychological limits, often culminating in task failure: an abrupt reduction in intensity or cessation of effort. While physiological mechanisms such as metabolic acidosis and oxygen supply have been widely studied, less is known about the subjective experience associated with task failure. In this study, a survey of 2,818 licensed cyclists provided novel insights into the subjective dimensions of task failure. Participants reported that physical sensations, especially breathing and muscle pain, were the most prominent cues at the limit of effort. Notably, 60.5% indicated they do not always reach their maximum perceived effort before task failure, suggesting a significant psychological component. Age, experience, and the use of feedback tools like powermeters influenced whether task failure was perceived as voluntary or involuntary. Cyclists in higher age categories more frequently perceived reaching their limits as voluntary, while younger or less experienced athletes reported involuntary task failure. Furthermore, strategies such as self-motivation, focusing on goals, and regulating breathing were commonly employed to sustain performance. Altered time perception during maximum effort was also a notable finding, with most cyclists perceiving time as passing more slowly. These results underline the multifactorial nature of task failure, involving complex interactions between physiological, psychological, and perceptual factors. Understanding these dynamics could inform targeted training approaches, enabling athletes to better manage effort and delay task failure, thereby optimizing performance.
... The arterial system also plays an important role in increased CO with training through vascular adaptions (i.e., increased artery diameters and decreased wall thickness) that increase arterial compliance supporting enhanced delivery of oxygenated blood to exercising muscle [6]. Together, these central and peripheral factors largely contribute to maximal aerobic capacity (i.e., VO 2 max); in fact, 70-85% of the variance in VO 2 max can be explained by cardiac output alone [9,10]. ...
Background
Aerobic capacity measured by maximal oxygen uptake (VO 2 max) is related to functional capacity and is a strong independent predictor of all-cause and disease-specific mortality. Sex-specific cardiac and vascular responses to endurance training have been observed, however, their relative contributions to VO 2 max are less understood. The purpose of this study was to evaluate sex-specific ventricular-vascular interactions associated with VO 2 max in healthy males and females.
Methods
Sixty-eight males and females (38% females, 35 ± 10y) characterised as recreational exercisers to highly trained endurance athletes, and free of chronic disease underwent a cycle ergometer to assess VO 2 max. Resting arterial compliance and echocardiographic evaluation of left ventricular (LV) structure and function were measured and indexed to body surface area.
Results
VO 2 max was similar between groups (54 ± 6 vs. 50 ± 7 ml/kg/min, p = 0.049). Indexed LV mass (LVMi) was higher (96 ± 15 vs. 81 ± 11, p = 0.001) in males versus females, respectively. Linear regression analysis revealed two models that were significantly associated with VO 2 max in males and females. In males, the two models included (1) longitudinal diastolic strain rate and LVMi (r ² = 0.31, p = 0.003) and (2) indexed end-diastolic volume (EDVi) and longitudinal diastolic strain rate (r ² = 0.34, p < 0.001). In females, the linear regression models included (1) LVMi, large arterial compliance, longitudinal systolic strain rate, and age (r ² = 0.69, p < 0.001) and (2) EDVi, large arterial compliance, longitudinal systolic strain rate, and age (r ² = 0.52, p = 0.003).
Conclusion
These findings reveal that while in both sexes, LVMi and LVEDVi are associated with VO 2 max, arterial compliance was also found to contribute to the variance in VO 2 max in females, but not in males. Further, ventricular relaxation was a significant factor in aerobic capacity in males, while in females ventricular contraction was a significant factor.
... VO 2 max is a function of oxygen delivery and utilization. In healthy individuals, VO 2 max is thought to be limited by systemic oxygen delivery, which in turn is mainly limited by stroke volume (Bassett Jr. & Howley, 2000;Levine, 2008). The cause behind a reduced VO 2 max in individuals with CKD is likely multifactorial. ...
Maximal oxygen uptake (VO2max) in healthy subjects is primarily limited by systemic oxygen delivery. In chronic kidney disease (CKD), VO2max is potentially reduced by both central and peripheral factors. We aimed to investigate the effect on VO2peak of adding arm exercise to leg exercise. Ten individuals with CKD stages 3–5 and 10 healthy controls, matched for age, sex, body size, and physical activity level, were included. Subjects performed two maximal exercise tests, one with legs only (L exercise) and one test where arm exercise was added to leg exercise (LA exercise). The increase in VO2peak, when comparing LA exercise with L exercise, was significantly higher in CKD (0.20 ± 0.18 L/min or 2.31 ± 1.78 mL/(kg·min)) than in controls (0.019 ± 0.12 L/min or 0.26 ± 1.62 mL/(kg·min); p = 0.02 and 0.01, respectively). The decrease in peak leg workload, when comparing L exercise with LA exercise, was larger in controls than in CKD, in absolute terms (p = 0.002) and relative to body weight (p = 0.01). VO2max in individuals with CKD is dependent on the active muscle mass, supporting a peripheral limitation to VO2max in CKD. By contrast, the control group appeared to have a more central limitation to VO2max.
... In an exercising person, maximal oxygen uptake is limited by the ability of the cardiorespiratory system to deliver oxygen to the exercising muscles. [16] The increase in the O2 pulse after the training session may reflect the degree of peripheral and cardiac adaptation to training. In our study, we observed that O2 pulse (the amount of oxygen consumed per heartbeat during exercise), which can be used as an indirect indicator of cardiac stroke volume, [17] was significantly higher in mesomorphs as compared to endomorphs. ...
Objectives:
Somatotype rating is used to categorise human physiques using parameters related to body shape and composition. These parameters are adiposity, musculoskeletal robustness, and linearity. Somatotype rating is based on anthropometric dimensions that influence a person’s ability to perform physical activity. This study aimed to measure cardiorespiratory responses to incremental exercise in different somatotypes.
Materials and Methods:
Fifty (50) healthy male participants with a mean age of 24.10 ± 4.55 years were recruited in this study. The dominant somatotype was determined using the Heath and Carter method. Cardiopulmonary exercise testing was done to measure peak VO2, peak VO2/kg, metabolic equivalents (METS), breathing reserve (BR), minute ventilation (V.E), oxygen pulse (VO2/HR), and heart rate.
Results:
The cardiorespiratory parameters showed significant differences between the endomorphs and mesomorphs. Mesomorphs showed significantly higher peak oxygen consumption (mL/min) (2487 ± 364.3 vs. 2151 ± 287.8; P = 0.013) and exhibited significantly higher peak VO2 % predicted values (78.13 ± 10.11 vs. 66.92 ± 10.09; P = 0.003) than the endomorphs. METS % predicted was significantly higher in mesomorphs than endomorphs (78.13 ± 11.95 vs. 66.92 ± 10.09; P = 0.003). Similarly, the V.E (L) of mesomorphs was also higher than that of endomorphs (95.32 ± 18.63 vs 71.13 ± 25.39), but the BR (L) of mesomorphs was lower than endomorphs (38.38 ± 11.87 vs 53.80 ± 17.16) and ectomorphs (38.38 ± 11.87 vs 52.79 ± 9.47). Mesomorphs showed higher O2 pulse than endomorphs (14.8 [10.3–24.0] vs 12.8 [9.2–21.9]; P = 0.02); they also showed significantly higher respiratory frequency than endomorphs (1/s) (48.25 ± 11.34 vs. 38.19 ± 6.89; P = 0.001) and ectomorphs (48.25 ± 11.34 vs. 40.92 ± 7.03; P = 0.03).
Conclusion:
Cardiorespiratory responses to exercise vary among different somatotypes. Exercise capacity, as measured by VO2 peak, is higher in mesomorphs.
... We found very good evidence for greater enhancement when HIIT was implemented in the onseason for sprint speed/power andVO 2max (forVO 2max also for HIIT relative to control), but the effect was unclear for repeated-sprint ability and could not be estimated for other performance measures. The greater on-season effect of HIIT on sprint speed/power andVO 2max is presumably driven by different adaptations in metabolic pathways-predominantly anaerobic pathways for sprint speed/power (Bangsbo et al., 1994;Rodas et al., 2000) and predominantly aerobic pathways forVO 2max (Fox et al., 1973;Bassett and Howley, 2000). Given that repeated-sprint performance is mediated by anaerobic and aerobic pathways Nevill et al., 1989;Bishop and Edge, 2006;Bishop et al., 2004), one could expect a greater benefit from HIIT for this measure in the on-season, and the uncertainty in the unclear effect allows for this outcome. ...
Introduction
Meta-analysts have found that high-intensity interval training (HIIT) improves physical performance, but limited evidence exists regarding its effects on highly trained athletes, measures beyond maximum oxygen uptake ( V ˙ O2max), and the moderating effects of different types of HIIT. In this study, we present meta-analyses of the effects of HIIT focusing on these deficits.
Methods
The effects of 6 types of HIIT and other moderators were derived from 34 studies involving highly trained endurance and elite athletes in percent units via log-transformation from separate meta-regression mixed models for sprint, time–trial, aerobic/anaerobic threshold, peak speed/power, repeated-sprint ability, V ˙ O2max, and exercise economy. The level of evidence for effect magnitudes was evaluated based on the effect uncertainty and the smallest important change of 1%.
Results
Compared with control training, HIIT showed good to excellent evidence for the substantial enhancement of most measures for some athlete subgroups in practically important study settings defined by effect moderators (maximum of 12.6%, for endurance female athletes after 6 weeks of aerobic traditional long intervals). The assessment of the moderators indicated good evidence of greater effects as follows: with more aerobic types of HIIT for V ˙ O2max (+2.6%); with HIIT added to conventional training for most measures (+1.1–2.3%); during the competition phase for V ˙ O2max (+4.3%); and with tests of longer duration for sprint (+5.5%) and time trial (+4.9%). The effects of sex and type of athlete were unclear moderators. The heterogeneity of HIIT effects within a given type of setting varied from small to moderate (standard deviations of 1.1%–2.3%) and reduced the evidence of benefit in some settings.
Conclusion
Although athletes in some settings can be confident of the beneficial effects of HIIT on some measures related to competition performance, further research is needed. There is uncertainty regarding the mean effects on exercise economy and the modifying effects of sex, duration of intervention, phase of training, and type of HIIT for most measures.
Systematic Review Registration
https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=236384.
... Maximal oxygen uptake, or VO₂max, represents the maximum rate at which the body can utilize oxygen during intense exercise, serving as a 1 key indicator of aerobic fitness and cardiovascular endurance . VO₂max varies across individuals and is influenced by a variety of factors, including age, gender, body composition, and lifestyle habits. ...
Background: VO₂max, or maximal oxygen uptake, is a vital indicator of cardiovascular and respiratory fitness, yet research on the impact of deep breathing exercises on VO₂max across different BMI categories remains limited. Our study addresses this gap by examining both immediate and short-term effects of deep breathing on VO₂max among young adults with varying BMI levels.Aim: To evaluate the immediate and short-term effects of deep breathing exercises on VO₂max in young adult males across different BMI groups.Methods: This cross-sectional study was conducted among 100 male students aged 18-25 years. Participants were divided into BMI groups (normal weight, overweight, obese) and underwent baseline VO₂max assessment using indirect calorimetry with the Bruce Protocol on Day 1. A deep breathing routine, performed twice daily for 10 minutes, was continued over four weeks, with VO₂max reassessed on Day 2 (immediate effect) and Day 30 (short-term effect). Results: Baseline VO₂max showed significant variation among BMI groups (p < 0.05). After a single deep breathing session on Day 2, all groups saw VO₂max improvements, with the highest increase in the normal-weight group. By Day 30, all groups exhibited statistically significant VO₂max gains (p < 0.05), especially among normal-weight participants. Conclusion: Deep breathing exercises positively impact VO₂max in young adults, particularly in those of normal weight, suggesting an effective, non-invasive method for enhancing Cardiorespiratory fitness.
... The maximal oxygen consumption, known as VO 2max , achieved during a graded maximal exercise test to voluntary exhaustion, is recognized by the World Health Organization as the premier measure of cardio-respiratory fitness. 2 VO 2max is a critical factor for endurance exercise performance because it sets the upper limit for aerobic metabolism. 3,4 The primary limitation of VO 2max is the rate of oxygen delivery to the working muscle, 5 many physiological parameters that influence oxygen delivery during exercise have been described previously. 6 VO 2max can be estimated through both maximal and submaximal tests, using direct or indirect methods. ...
Introduction: VO2max, a measure of the maximum oxygen uptake during physical exertion, is a critical indicator of cardiovascular fitness. Evaluating VO2max in young adults helps in understanding their fitness levels and guiding improvements. This study aimed to assess normal VO2max levels and investigate the relationships between oxygen saturation (SpO2) and VO2max, as well as between blood pressure and VO2max, in both male and female participants. Methods: A total of 93 students (45 males, 48 females) aged 18 to 25 years from Gandaki Medical College, Pokhara, were selected through simple random sampling. VO2max was estimated using the Queen’s College Step Test (QCT), a widely accepted indirect method to assess cardiorespiratory fitness. QCT provides a convenient way to evaluate maximum oxygen uptake in a non-laboratory setting. Results: The mean VO2max for male participants was 62.00±8.77 ml/kg/min, while for females, it was 41.79±3.18 ml/kg/min. Males exhibited significantly higher VO2max values compared to females (p<0.001). Both diastolic blood pressure (p = 0.013) and SpO2 (p < 0.001) were found to have a significant influence on VO2max in female but not changed in the male. Conclusions: This study confirms that gender-related differences in cardiovascular fitness exist, with males generally showing higher endurance levels compared to females. The lower VO2max values observed in females were primarily associated with variations in SpO2 and diastolic blood pressure. These findings highlight the importance of considering physiological variables such as oxygen saturation and blood pressure in the assessment of female cardiorespiratory fitness.
... Endurance athletes rely on an efficient balance of oxygen delivery and uptake to sustain high-intensity exercise and enhance their athletic performance 1 , 2 . The maximal oxygen uptake test (VO 2-max ) is a vital physiological assessment that determines sports performance by analyzing exhaled-gases and cardiorespiratory variables during incremental exercise intensity 1 . This assessment, known as ergospirometry or Cardiopulmonary Exercise Testing (CPET), reflects the exercise response of the cardiovascular, respiratory, and muscular systems 3 . ...
The gold standard to assess the aerobic capacity in physically active subjects and athletes is the maximal oxygen consumption test (VO2-max), which involves analysis of exhaled–gases and cardiorespiratory variables obtained via the breath–by–breath method in an ergospirometer during an incremental exercise. However, this method cannot elucidate metabolic changes at the muscular level. Near-infrared spectroscopy (NIRS) has emerged as a valuable technology to evaluate local oxygen levels (Tissular Saturation Index, TSI) by quantifying the concentrations of oxygenated (O2–Hb) and deoxygenated (H–Hb) hemoglobin in the microvasculature of tissues. NIRS applications extend to respiratory and locomotor muscles, assessing metabolic changes associated with the cost of breathing (COB) and peripheral workload, respectively. Additionally, cerebral regions, such as the prefrontal cortex, have been explored with NIRS technology to assess physiological changes related to cognitive demand associated with planning or ideation of motor tasks linked to sports performance. Thus, by analyzing exercise-induced changes (D) in O2–Hb, H–Hb, and TSI, it is possible to identify central and peripheral exercise limitations, particularly when endurance training is the main component of physical fitness (e.g., running, cycling, triathlon, etc.). Addressing these factors is paramount for coaches and exercise physiologists to optimize athletic performance, incorporating training strategies focused on the primary exercise-limiting factors. This study outlines a protocol for utilizing wearables devices equipped with NIRS technology to analyze exercise changes in TSI, O2–Hb, and H–Hb, alongside cardiorespiratory variables typically registered in athletes during VO2–max tests. This approach offers a comprehensive method for identifying the primary systems involved in stopping exercise progression and sports performance improvement.
... For example, VO2max is highly praised in the running and cycling community. On the other hand, this parameter on its own is not a perfect metric for assement of endurance athlete's performance (Bassett & Howley, 2000). This could originate from the fact that the VO2max testing does not include the endurance aspects of performance and it does not consider the actual performance of an athlete (velocity). ...
Purpose: Performance assessment and analysis of aerobic endurance athlete usually requires the use of expansive measurement equipment in a laboratory setting. The main motivation for the paper was the fulfilment of a goal of obtaining a reliable, objective and easily measurable endurance athlete’s performance parameter, which would serve coaches and athletes to track their progress, as well as a benchmark for comparison amongst the athletes competing in the same discipline. Methods: The main idea of the paper originates from the fact that each individual endurance workout causes a physiological response in a human body. Therefore, the newly developed athlete’s performance parameter - velocity quotient (VQ) considers both the athlete’s actual performance (velocity) and his/her response (heart rate) to it. The VQ parameter’s behavior was theoretically investigated in case of running. The reliability of the VQ parameter was also experimentally validated with dataset obtained during multiple running exercises of a single recreational level athlete. Results: The velocity quotient showed potential for being a reliable predictor of endurance runners’ performance on a theoretical base which was supported by the preliminary experimental validation study, which produced the value of Pearson's correlation coefficient between the velocity quotient and the sports watch estimated VO2max of 0.7942. Conclusion: The behavior of the velocity quotient was predicted at various exercise intensities (average heart rates) and fitness levels. Fairly good correlation between the velocity quotient and the sports watch estimated VO2max was found while more daily variations of VQ than for VO2max were observed.
... Sabe-se que o pico de VO 2 é afetado por diversos fatores, incluindo oxigenação muscular, capacidade de transporte de oxigênio, função endotelial, volume expiratório forçado no primeiro segundo (VEF 1 ), capacidade de difusão do pulmão para monóxido de carbono (D LCO ) e massa muscular. 18,19 Sendo assim, os resultados inconsistentes e a ausência geral de uma diferença significativa no pico de VO 2 com o treinamento com exercícios aeróbicos podem ser atribuídos aos grupos de estudo heterogêneos e à influência de múltiplos fatores sobre o pico de VO 2 . Os valores basais de pico de VO 2 também impactam os resultados pós-exercício. ...
Resumo
Fundamento
As diretrizes atuais orientam a prática de exercícios para a maioria dos pacientes com cardiopatia congênita (CPC). No entanto, a atividade física continua baixa em indivíduos com CPC, com pesquisas limitadas sobre os efeitos dos exercícios em adultos.
Objetivos
O objetivo deste estudo é avaliar a segurança e a eficácia do treinamento físico sobre a capacidade de realização do exercício e a qualidade de vida para pacientes com cardiopatia congênita adulta (CPCA).
Métodos
Pesquisamos as bases de dado da PubMed/Medline, Cochrane Library, Web of Science e Scopus até dezembro de 2022 em busca de estudos clínicos randomizados que avaliassem os efeitos do treinamento aeróbico e de resistência sobre a capacidade de realização de exercícios e a qualidade de vida na CPCA. Das 3.517 citações obtidas, dez artigos elegíveis foram incluídos.
Resultados
A metanálise dos estudos clínicos randomizados incluídos (286 participantes) não revelou mudanças significativas no consumo de máximo de oxigênio ou na qualidade de vida na CPCA com treinamento com exercícios (diferença média combinada = 0,33 ml/kg/min [IC de 95%, -0,88 a 1,54 ml/kg/min]; p = 0,60; I² = 3%). No entanto, o aumento na carga de trabalho máxima foi significativo (diferença média combinada = 8,86 watts [IC de 95%, 0,78 a 16,93], p = 0,03, I² = 0%).
Conclusões
Nossa revisão confirma que o treinamento com exercícios aumenta a carga de trabalho máxima em pacientes com CPCA. No entanto, a falta de um protocolo padronizado entre as intervenções de exercícios nessa população pode ter contribuído para a ausência de uma mudança significativa no pico de VO2 e na qualidade de vida observada nos estudos conduzidos. Além disso, a heterogeneidade dos programas de exercícios pode ser um fator contribuinte para a inconsistência dos resultados. Neste contexto, a implementação de protocolos de exercícios padronizados em pesquisas futuras, particularmente com tamanhos de amostra maiores, é fundamental para melhorar a comparabilidade dos resultados. Estudos clínicos randomizados bem projetados, que avaliem o treinamento com exercícios estruturados em pacientes com CPCA, fornecerão dados mais claros.
... The inclusion of these conditions, which involve different pathologies, results in the formation of heterogeneous groups. It is known that peakVO 2 is affected by many factors such as muscle oxygenation, oxygencarrying capacity, endothelial function, forced expiratory volume in the first second (FEV 1 ), diffusing capacity of the lung for carbon Winter et al. 16 Step 18,19 Therefore, the inconsistent results and overall lack of a significant difference in peakVO 2 with aerobic exercise training may be attributable to the heterogeneous study groups and the influence of multiple factors on peakVO 2 . Baseline peakVO 2 values also impact post-exercise results. ...
Background Current guidelines advise exercise for most congenital heart disease patients (CHD). However, physical activity remains low in CHD individuals, with limited research on exercise’s effects in adults. Objectives The aim of this study is to evaluate the safety and efficacy of exercise training on exercise capacity and quality of life in adult congenital heart disease (ACHD) patients. Methods We searched PubMed/Medline, Cochrane Library, Web of Science, and Scopus through December 2022 for randomized controlled trials assessing aerobic and resistance training effects on exercise capacity and quality of life in ACHD. Out of 3,517 citations, ten eligible articles were included. Results Meta-analysis of the included randomized controlled trials (286 participants) found no significant change in peak oxygen consumption or quality of life in ACHD with exercise training (pooled mean difference = 0.33 ml/kg/min [95% CI, -0.88 to 1.54 ml/kg/min]; p = 0.60; I2= 3%). However, the increase in maximum workload was significant (pooled mean difference = 8.86 watts [95% CI, 0.78 to 16.93], p = 0.03, I2 = 0%). Conclusions Our review confirms that exercise training increases the maximum workload in ACHD patients. However, the lack of a standardized protocol among exercise interventions in this population may have contributed to the absence of a significant change in peak VO2 and quality of life observed in the conducted studies. The heterogeneity of exercise programs could be a contributing factor to the inconsistency of the results. In this context, the implementation of standardized exercise protocols in future research, particularly with larger sample sizes, is crucial to enhance the comparability of outcomes. Well-designed randomized controlled trials studying structured exercise training in ACHD patients will provide clearer insights.
... Adopting an inactive lifestyle [2] results in inactivity-related health problems among persons with MS (PwMS), such as osteoporosis, cardiovascular disease, fatigue, and depression [3]. Aerobic capacity is a crucial health [4] and performance marker [5] [6], and PwMS exhibit lower values of maximal aerobic power when compared to age and sex-matched healthy adults [7]. Importantly, lower risk of cardiovascular disease [6], better walking performance [8], faster cognitive processing speed [9], and enhanced neuroprotection and brain health [10], have all been associated with greater aerobic capacity in MS [6]. ...
Objective: Cardiopulmonary Exercise Testing (CPET) is challenging among persons with mobility disability. We sought the optimal adapted device to achieve a maximal CPET.
Design: Randomized crossover trial, within-subjects, repeated measures design
Setting: Primary Care and Referral Center
Participants: Clinic-referred persons with multiple sclerosis (PwMS) (n=10) with three-month stability, no exercise obstruction, MoCa>24, ability to walk with or without assistance, and sex- and age-matched (+-3 years) Controls (n=7) recruited by convenience sampling
Interventions: CPET on body weight-supported treadmill (BWST) and total body recumbent stepper (TBRS)
Main Outcome Measures: Standard aerobic metrics (V ̇O2max, % normative values for V ̇O2max [%V ̇O2max], heart rate maximum [HRmax], age-predicted HRmax, and Respiratory Exchange Ratio)
Results: PwMS achieved similar V ̇O2max (mL.min-1.kg-1) on the TBRS and BWST (26.53+-8.7 vs. 24.24+-7.8) while Controls obtained higher values on BWST than TBRS (40.27+-7.6 vs. 34.32+-7.1, p<0.001). PwMS more consistently achieved criteria for maximum CPET using TBRS. During the preliminary investigation of the MS subgroup with a higher mobility disability, CPET using BWST exaggerated already low CPET metrics.
Conclusions: Although Controls achieved higher CPET values on BWST, V ̇O2max between devices were similar among PwMS. Only when using BWST, PwMS V ̇O2max and %V ̇O2max were lower than Controls, likely because of leg fatigue and weakness. Using TBRS permits persons with mobility disability to achieve more criteria for a maximum CPET. Our results suggest that CPET using BWST, being reliant on the lower body, likely disadvantages PwMS, especially those with mobility disability.
... Interestingly, there is a substantial positive association (r = 0.997) between maximum heart rate and movement time, which is in line with other research showing that lengthy endurance sports increase cardiovascular stress [10] . The fact that aerobic exercise is linked to average speed (r = 0.956) backs up research that shows how aerobic capacity can improve endurance performance [11] . These kinds of studies show that having more aerobic fitness makes you more efficient at moderate speeds. ...
p>This case study examines the use of wearable technology to monitor physiological and performance metrics during a 100+ km pilgrimage on the Camino de Santiago. The subject, a 34-year-old female amateur triathlete recovering from an ankle injury, used a Garmin Enduro device to track key data over five days. The study focuses on heart rate, speed, cadence, caloric expenditure, and environmental factors, shedding light on how wearable devices can provide valuable insights into endurance performance. Correlation analysis highlights significant relationships between physical performance and physiological markers, offering a deeper understanding of how such technology can enhance both athletic performance and the overall pilgrimage experience.</p
... Maximum oxygen uptake (VO 2 max), defined as the highest rate at which oxygen can be absorbed and utilized by the body during intense exercise, is one of the key variables in exercise physiology and the best indicator of aerobic capacity [91][92][93][94]. Physiological variables such as VO 2 max are highly correlated with endurance exercise performance and are considered the golden standard for assessing cardiorespiratory fitness [3,95,96]. ...
Objective: This study aimed to perform an umbrella review of existing systematic reviews on the effects of saddle position on cycling. Material and methods: We conducted a systematic search across the electronic databases EBSCO, PubMed, Scopus, Web of Science, and B-On for systematic reviews investigating the effects of saddle position on cycling, following the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. To prevent the risk of bias, two researchers independently performed the search. To evaluate the methodological quality of the included reviews, the Assessing the Methodological Quality of Systematic Reviews 2 (AMSTAR 2) checklist was used. Results: A total of seven systematic reviews that met the eligible criteria were included. The systematic reviews showed high heterogeneity among themselves (e.g., type of included studies, participants' characteristics, or evaluated outcomes) and low to critically low methodological quality. Relationships have been found between the rider's saddle position and health issues (such as low back pain (four studies), knee injury or pain (three studies), lumbar kyphosis (one study), and impact on perineum (two studies)), and on performance alterations (such as, muscle activation, oxygen uptake, load and intensity, efficiency (one study), and comfort (one study)). The results showed that some research provided conflicting evidence in regard to the studied relations (e.g., knee injury or pain, impact on perineum, and efficiency). Conclusions: Cyclists' saddle position impacts various issues related to health and performance. More research is needed, and future studies should focus on the clarification of the conflicting evidence observed in this review.
High-intensity interval training (HIIT) has shown to improve exercise capacity, symptom burden, and quality of life in COPD patients, but it remains to be investigated if HIIT can counteract limb muscle dysfunction. Therefore, we examined the impact of a 12-week supervised HIIT protocol on muscle oxygen conductance.
Eight patients with mild to moderate COPD and eight age-, sex- and BMI-matched controls underwent a 12-week HIIT intervention. Leg blood flow (Q̇ leg ) and arterio-venous blood samples were collected at rest and during active single-leg knee extensions (KEE) at unloaded (0 watts) and 20% of peak workload (W Lpeak ) to estimate leg muscle oxygen conductance pre- and post-HIIT. Pre-HIIT, Q̇ leg was similar between groups during unloaded KEE (p=0.108) but lower at 20% W Lpeak in the COPD group, compared to control group. Q̇ leg responses were higher during unloaded KEE (28%, p=0.012) and 20% W Lpeak (40%, p<0.001) post-HIIT in the COPD group, whereas no change occurred in the control group. Flow adjusted skeletal muscle O2 conductance was higher in the COPD pre-HIIT but only increased in the control group. Thus, there was no difference in diffusive or convective capacity between groups post- HIIT at submaximal KEE. COPD assessment score decreased by 2.8[1;4] (p=0.003) in the COPD group and V̇O 2peak increased in both groups (COPD 192 mL O2/min, p=0.032, control 257 mL O2/min, p=0.004) with no time/group interaction.
A 12-week HIIT intervention may improve peripheral exercise capacity in COPD by increasing the vasodilatory function in working muscle, while concurrently improving whole-body exercise capacity and symptom burden.
Purpose:
The aim of the present study was to compare performance and physiological effects, and inter-individual response variation in performance and its physiological determinants between heart rate-based (HR), race pace-based (RP) and heart rate variability-based (HRV) training prescription approaches in recreational distance runners.
Methods:
Twenty-eight participants completed a 6-week endurance training intervention after being randomly assigned to three groups: HR (n = 9), RP (n = 9), and HRV (n = 10) training prescription approaches.
Results:
No interaction effects between groups were observed. Main time effects were found for absolute and relative V̇O2max, running economy (RE), speeds associated to the first (sVT1) and second ventilatory thresholds (sVT2) and 7 km time trial performance (TT) (p < 0.001, 0.88 ≤ d ≤ 2.67). The RP group improved TT (p < 0.05, ES = 1.07), showing greater effectiveness in enhancing maximal aerobic speed and fat mass reduction, but did not consistently improve physiological parameters like sVT2 or RE. The HRV method increased sVT2 (p < 0.01, ES = 1.34) and was more successful in boosting sVT1 and V̇O2max, although it resulted in an increase in fat mass. Training load was similar between groups (p > 0.05), and a pyramidal training intensity distribution model was found in all groups. The lowest inter-individual response variation in TT was found in the RP group (coefficient of variation [CV] = 0.82), whereas the HRV group demonstrated a lower variation in relative V̇O2max (CV = 0.75) and sVT2 (CV = 0.79).
Conclusions:
The RP approach is an effective and useful training prescription method for optimising performance in recreational runners, while the HRV method proves valuable for enhancing key physiological markers.
Background
Cardiopulmonary exercise testing (CPET) is usually considered the gold standard for assessing maximal oxygen consumption (V̇O 2max ), a health and performance marker in patients with chronic obstructive pulmonary disease (COPD). Despite the widespread application of CPET, the absolute and relative test‐retest reliability of CPET‐derived metrics remains unexamined.
Objective
To examine and compare test‐retest reliability of CPET derived metrics in individuals with COPD and healthy matched controls.
Methods
12 individuals with COPD and 12 healthy age‐ and sex‐matched controls were included in this case‐control study. Each participant completed two CPET on a bicycle ergometer on two different days. Absolute reliability was reported as smallest real difference (SRD) and relative reliability as coefficient of variance (CV) and intraclass correlation coefficients (ICC).
Main Results
SRD for peak oxygen uptake was 451.6 (267.4;1006.4) mL/min and CV was 7.8 (4.7;11.0)% in patients with COPD, whereas SRD was 244.2 (151.4;491.5) mL/min and CV was 3.0 (1.8;4.2)% in healthy controls but with no significant between group difference for SRD. CV values for all CPET derived metrics were found to be below 10%. Apart from peak workload achieved and peak minute ventilation, SRD and CV were significantly higher in COPD than in controls for all other CPET‐derived metrics.
Conclusion
This study provides test‐retest reliability estimates of the most widely used CPET derived metrics in individuals with COPD and healthy matched controls. Test‐retest reliability for most metrics derived from CPET were found to be lower in individuals with COPD when compared to healthy controls.
Background
Maximum oxygen consumption is a measure of an individual’s cardiorespiratory fitness which is a singular predictor of an array of diseases. Several exercise and non-exercise assessments are frequently compared to know which method(s) provide the most accurate estimation of aerobic capacity due to difficulties in using the direct method. There is a need to know if an estimation method is the right fit for a population without huge overestimation or underestimation due to ethnical variation. This study was undertaken to assess the estimations of the cardiorespiratory fitness of healthy African males by the submaximal exercise-based and the non-exercise-based equations in undergraduate students of the University of Ibadan, Nigeria.
Results
VO2 was significantly higher in the undergraduate students of the University of Ibadan in all the equations used (44.38 ± 39.07, 62.46 ± 27.61, 44.38 ± 39.07, 62.46 ± 27.61, 46.37 ± 3.31, 46.16 ± 3.64, 47.08 ± 3.19). The two submaximal exercises compared using the Bland–Altman Plot showed a high degree of agreement, further linear regression performed showed no proportional bias on the distribution of data around the mean difference line (p > 0.05). Cross-validation using the Bland–Altman plot and linear regression for the five non–exercise predicted equations with the YMCA submaximal exercise test and Bruce submaximal exercise test all showed a significance difference of (P < 0.05) showed that data from all the methods provided proportional bias on the distribution of data around the mean difference line.
Conclusion
This study asserts that caution should be taken when using a non-exercise equation to predict VO2 in the African population. It is therefore recommended to carry out various assessment methods of VO2 estimation in a wider population using various protocols, and also develop a predictive equation for VO2 specific to the African population.
Position Statement: The International Society of Sports Nutrition (ISSN) presents this position based on a critical examination of the literature surrounding the effects of long-chain omega-3 polyunsaturated fatty acid (ω-3 PUFA) supplementation on exercise performance, recovery, and brain health. This position stand is intended to provide a scientific foundation for athletes, dietitians, trainers, and other practitioners regarding the effects of supplemental ω-3 PUFA in healthy and athletic populations. The following conclusions represent the official position of the ISSN: Athletes may be at a higher risk for ω-3 PUFA insufficiency.
Diets rich in ω-3 PUFA, including supplements, are effective strategies for increasing ω-3 PUFA levels.
ω-3 PUFA supplementation, particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), has been shown to enhance endurance capacity and cardiovascular function during aerobic-type exercise.
ω-3 PUFA supplementation may not confer a muscle hypertrophic benefit in young adults.
ω-3 PUFA supplementation in combination with resistance training may improve strength in a dose- and duration-dependent manner.
ω-3 PUFA supplementation may decrease subjective measures of muscle soreness following intense exercise.
ω-3 PUFA supplementation can positively affect various immune cell responses in athletic populations.
Prophylactic ω-3 PUFA supplementation may offer neuroprotective benefits in athletes exposed to repeated head impacts.
ω-3 PUFA supplementation is associated with improved sleep quality.
ω-3 PUFA are classified as prebiotics; however, studies on the gut microbiome and gut health in athletes are currently lacking.
Soccer is a team sport characterized by repeated high-intensity sprints followed by brief periods of recovery. Repeated sprints with (RCOD) and without (RSA) change-of-direction has therefore been recognized as an important fitness component. The purpose of the present study was to examine the differences in physiological responses between RSA and RCOD, and the relationship with Yo-Yo intermittent recovery test (YYIR1), as an estimate of aerobic capacity, in female soccer players. Thirteen female soccer players (age: 20.8 ± 2.6 years) participated. All players performed an RSA and RCOD test, as well as a YYIR1 test. Total time, fatigue (dec%), lactate ([La]b), rating of perceived exertion (RPE) and heart rate were recorded for each sprint test along with total distance covered in the YYIR1. RSA induced significant higher dec% (8.0 ± 3.0% vs. 5.0 ± 2.4%, p = 0.008, ES = 0.89), [La]b (13.5 ± 3.1mml/L vs. 9.9 ± 3.0mml/L, p = <0.001, ES = 2,25) and RPE (8 vs. 7, p = 0.003, ES = 1.0) compared to RCOD. The heart rate recovery was significantly faster for RCOD compared to RSA (173 ± 11 bpm vs. 178 ± 8 bpm, p = 0.02, ES = 0.89). No significant correlation could be found between aerobic capacity and RSA and RCOD variables. RSA was a more physiological taxing test compared to RCOD when the protocols were matched for sprint duration. This information can help athletes and coaches that are involved in women’s soccer to design and adapt training strategies in the future.
The comparison of core training programme that is carried out for 8 weeks to the young footbal- lers and volleyball players, with the physichal conditions and parameters of performance
The aim of this study was to plan the physical condition and performance parameters of the core training program for young male footballers and volleyballers for 8 weeks. Twenty male soccer players (the mean age 15,40±0,82, mean leght 1,70±0,06 m, mean body weight 59,85±5,00 kg) who play football at Pursaklar Municipality Sports Club with 14 male volleyball players (the mean age 15±00, mean leght 1,86±0,06 m, mean body weight 73,57±7,24 kg) who play volleyball at Halk- bank Volleyball Clup were included in study on a voluntary basis. Before the trainings, pre-test sco- res ( speed 10-20m, sit-up 30 sn, 20 m shuttle run, vertical jump, core stabilization and prone bridge ) were recorded. İn addition to the normal training of both groups, the core training was applied for 8 weeks including the first 6 weeks (3 days / week) and the last 2 weeks (2 days / week). At the end of the training, the final test measurements of the groups were taken in accordance with the proto- col. The data obtained were evaluated using the IBM SPSS Statistics 22.0 statistical program. Ac- cording to statistical process result, there was a significant increase in performance tests of football and volleyball players. There was a significant difference in anaerobic power performance values only for football players. While there was a significant increase in the final measurement values of prone bridge, trunk flexion and trunk extensions of both groups, there was no significant difference in letheral flexion test in volleyballs. When performance and core stabilization tests of football and volleyball players were compared, the performance values showed a significant difference, but this difference was not observed in trunk flexion test (p<0.05).
As a result, it was observed that the 8 week core training sessions that will be applied in addition to football and volleyball training have contributed to the performance improvement of young pla- yers and volleyball players such as strength, speed and endurance. It is considered that the inclusion to training of the young players will improve the performance of the athleticks positively.
Background
Elbow injuries are likely to generate a decreased range of motion (ROM), which might negatively affect athletic performance. To date, the effect of elbow stiffness on endurance running performance has never been studied. We conducted an observational, prospective, cross-over study to examine the impact of elbow stiffness on running economy.
Methods
Twenty trained athletes performed running economy tests at 12 km·h ⁻¹ , with and without a limited elbow ROM (flexion: 90°, extension: 45°), imposed by a dynamic brace mimicking a severe elbow stiffness. Relative intensity and performance indexes were measured during a subsequent maximal incremental exercise test.
Results
Running economy was measured at 180 ± 10.6 mlO 2 ·km ⁻¹ ·kg ⁻¹ with a full ROM, and 180.2 ± 12.3 mlO 2 ·km ⁻¹ ·kg ⁻¹ with the limited ROM showing a non-significant 0.1% difference ( p = 0.871).
Discussion
Athletes experiencing post-traumatic elbow stiffness can find reassurance in knowing that it does not seem to impact a crucial metric of endurance running performance, namely running economy. Further research could explore elbow movement at different intensities of running, from higher aerobic speeds to sprinting.
This article lays out the determinants of maximal O2 consumption (VO2max) achieved during high intensity endurance exercise. It is not a traditional topical review but rather an educational essay that intertwines chance observations made during an unrelated research project with a subsequent program of stepwise thought, analysis and experimentation to reveal how O2 is delivered to and used by the mitochondria. The centerpiece is the recognition that O2 is delivered by an inter-dependent system of transport components functioning as a “bucket brigade”, made up of the lungs, heart, blood and circulation, and the muscles themselves, each of which affects O2 transport by similar amounts as they change. There is thus no single “limiting factor” to VO2max. Moreover, each component is shown to quantitatively affect the performance of the others. Mitochondrial respiration is integrated into the O2 transport system analysis to reveal its separate contribution to VO2max, and to show that mitochondrial PO2 at VO2max must be extremely low. Clinical application of the O2 transport systems analysis is described to separate central cardiopulmonary from peripheral tissue contributions to exercise limitation, illustrated by a study of patients with COPD. Finally, a short discussion of why muscles operating maximally must endure an almost anoxic state is offered. The hope is that in sum, both the increased understanding of O2 transport and the scientific approach to achieving that understanding described in the review can serve as a model for solving other complex problems going forward.
The oxidative capacity of cat skeletal muscles (soleus, gracilis, and gracilis chronically stimulated for 28 days) was derived from the total mitochondrial content in the muscle, the surface area of mitochondrial inner membranes, and respiratory activities of isolated mitochondria. Mitochondrial content was estimated by standard morphometry. The surface area of mitochondrial inner membranes per unit volume of mitochondria was estimated by a stereological method. The respiratory activities of isolated mitochondria were measured biochemically, using pyruvate/malate, glutamate/malate, succinate, or cytochrome c as substrate. Structurally and functionally, mitochondria from the three muscle types showed nearly identical characteristics. Oxidative activity was dependent on substrate; with succinate, 5.8 ml of O2 per min per ml of mitochondria was the rate most likely to represent physiological conditions. Oxidative activities of 3.1 ml.min-1.ml-1 with pyruvate/malate and 14.5 ml.min-1.ml-1 with cytochrome c as substrates were theoretical lower and upper bounds. The oxidative capacity of each of the three muscles was thus in direct proportion to the total volume of mitochondria in the muscle. The respiratory capacity of isolated mitochondria was very near to the maximal oxygen uptake rate of mitochondria that is commonly estimated in intact muscles of a wide variety of animals.
The influence of supplemental oxygen on exercise performance was assessed in 17 patients with severe airflow obstruction. Exercise capacity was measured by the six minute walking distance, by an endurance walking test, and by an endurance cycling test and comparison was made with performance when the patient was breathing air. In addition, the relation between the flow rate of supplemental oxygen and cycling endurance time was studied. Portable oxygen (41 min-1) carried by the patient increased the mean endurance walking time by 59% and the six minute walking distance by 17%. The endurance time for cycling at a constant work load was increased by 51% with oxygen at a flow rate of 21 min-1, by 88% at 41 min-1, and by 80% at 61 min-1. Supplemental oxygen prolonged the length of time that the patients were able to walk at a fixed speed. It also increased the mean speed achieved during a six minute walk but this was variable and did not occur in all the subjects. The benefit from supplemental oxygen was not cancelled by the effort of carrying the portable cylinder.
This study has attempted to describe the fiber composition and respiratory potential in the leg (gastrocnemius) muscle of highly trained, elite female distance runners. As noted, many of these women were competing successfully in middle-distance (1500-3000 m) rather than long distance (10 km and marathon) events. This fact appears to explain many of the differences observed between these "elite female runners" and the "elite male runners" studied in the 1975 Dallas study (6). With the exception of differences in muscle fiber areas, the female runners appear to show the same enzyme adaptations to endurance training that have been reported for male runners. The most notable finding of this study was the remarkable similarity of muscle fiber composition and enzyme activity for male and female runners when matched according to their preferred competitive distance.
The effects of graded induced erythrocythemia on cardiovascular and metabolic responses to intense treadmill running were studied in four highly trained endurance runners. Three autologous infusions of 1 unit (U) whole blood (450 ml/U) were administered sequentially 2-7 days apart. Maximal O2 consumption (VO2max) increased from 5.04 l/min at control (C) to 5.24 l/min after 2 U (R2) and 5.38 l/min after 3 U (R3). Cardiac output during treadmill running at 91% control VO2max was 28.2 l/min at C, 29.8 l/min at R2, and 33.1 l/min at R3. Corresponding heart rates were unchanged, and stroke volume was increased at R3. Peak lactate concentration was reduced, and arterial acid-base status improved at R2 and R3 after standardized bouts of intense exercise. Arterial blood pressures and electrocardiograms during exercise were not affected by erythrocythemia. We conclude that the reinfusion of up to 3 U of autologous blood into highly trained endurance runners who have normal hematology does not adversely affect their cardiovascular response to maximal exercise. In addition, the increases in VO2max following reinfusion of 2 U, and again after 3 U, suggest that the aerobic power of the working muscles was not surpassed at these levels of erythrocythemia.
The concentration of lactate in the blood is the result of (1) those processes which produce lactate and contribute to its appearance in the blood and (2) those processes which catabolize lactate after its removal from the blood. Consequently, the concentration of lactate in the blood provides minimal information about the rate of lactate production in muscle. The accumulation of lactate beyond the lactate threshold [T(lact)] does provide an indication that the mechanisms of lactate removal fail to keep pace with lactate production. Lactate is produced in skeletal muscle as a direct result of increased metabolic rate and glycolytic carbon flow. Factors which influence lactate production in muscle include: the Vmax of lactic dehydrogenase (LDH), which is several times greater than the combined activities of enzymes which provide alternative pathways of pyruvate metabolism; the kM of LDH for pyruvate, which is sufficiently low to assure maximal stimulation of LDH in the conversion of pyruvate to lactate; and the K'eq of pyruvate to lactate conversion, which exceeds 1000. Recent studies on dog gracilis muscle in situ clearly indicate that lactate production occurs in contracting pure red muscle for reasons other than an O2 limitation on mitochondrial ATP production. In addition to failure of the essential assumption of the anaerobic threshold [T(an)] hypothesis that there exist limitations on O2 availability in muscles of healthy individuals during submaximal exercise, several groups of investigators have produced results which indicate that parameters associated with changes in pulmonary minute ventilation [i.e., the ventilatory threshold, T(vent)] do not always track changes in blood lactate concentration. Therefore, the T(an) hypothesis fails on the bases of theory and prediction. A series of kinetic tracer experiments to better understand lactate kinetics during exercise is proposed.
Oxygen uptake and carbon dioxide output were measured in 32 untrained subjects during exercise on the bicycle ergometer. It was shown that the work respiratory quotient (RQ) under standardized conditions can be used as a measure of physical fitness. ΔRQ (work RQ minus 0.75) increases logarithmically with the work load and maximal O 2 uptake is reached at a ΔRQ value of 0.40. This observation offered the possibility of predicting the maximal O 2 uptake of a person, based on the measurement of RQ during a single bicycle ergometer test at a submaximal load. For each work RQ between 0.95 and 1.15 a factor was presented, together with the aid of a simple equation, which gave a good approximation (generally better than ±10%) of the maximal O 2 uptake.
Muscle biopsies were obtained from the gastrocnemius of 14 elite distance runners, 18 middle distance runners, and 19 untrained men. The middle distance runners were all highly trained, but had significantly slower performance times than the elite runners at distances greater than 3 miles. Fiber composition and mean cross sectional areas were determined from muscle sections incubated for histochemical activity. A portion of the specimen was used to determine succinate dehydrogenase (SDH), lactate dehydrogenase (LDH) and phosphorylase activities. All subjects were tested for maximal oxygen uptake on a treadmill. As previously demonstrated by others, the elite runners' muscles were characterized by a high percentage (79%) of slow twitch (ST) fibers. On the average, the cross sectional area of their ST fibers was found to be 22% larger than the FT fibers (P<0.05). SDH activity of whole muscle homogenates from elite and middle distance runners was 3.4 and 2.8 fold greater, respectively, than that measured in the untrained men. Since the LDH and phosphorylase activities were similar for the runners and untrained men, it appears that training for distance running has little influence on the enzymes of glycogenolysis.
A. V. Hill was born in Bristol, the son of Jonathan Hill (1857-1924) and Ada Priscilla ( née Rumney ) (1861-1943). The father was the second of nine children; the mother one of four sisters. They were married in 1880, and had a son and a daughter, Muriel, who was born in February 1889. She became a biochemist and married Dr T. S. Hele, a colleague who worked in the same field and was later elected Master of Emmanuel College,Cambridge. Muriel died in 1941. A. V. (as he became known to his family and all his colleagues) traced his ancestry to the middle of the eighteenth century. To judge by the family tree which he himself drew, the name ‘Archibald Vivian' must have been a new departure. There were successions of Jameses and Jonathans, several Johns, an occasional Charles, George, Samuel, etc. among them, but apparently no precedent for Archibald or Vivian. A. V.’s forebears all lived in the West Country, mostly in Devonshire and Somerset. On the paternal side he was preceded by five generations of timber merchants at Bristol, carrying on the business which had been founded by James Hill in 1750. James had come from Ireland and later returned there to join a volunteer regiment. He is believed to have been killed during the Irish troubles.
The basis of the scientific method is the development of intellectual models, the predictions of which are then subjected to scientific evaluation. The more robust test of any such model is one that aims to refute or falsify its predictions. Successful refutation forces revision of the model; the revised model persists as the 'truth' until its predictions are, in turn, refuted. Thus, any scientific model should persist only as long as it resists refutation. An unusual feature of the exercise sciences is that certain core beliefs are based on an historical physiological model that, it will be argued, has somehow escaped modern, disinterested intellectual scrutiny. This particular model holds that the cardiovascular system has a limited capacity to supply oxygen to the active muscles, especially during maximal exercise. As a result, skeletal muscle oxygen demand outstrips supply causing the development of skeletal muscle hypoxia or even anaerobiosis during vigorous exercise. This hypoxia stimulates the onset of lactate production at the 'anaerobic,' 'lactate,' or ventilation thresholds and initiates biochemical processes that terminate maximal exercise. The model further predicts that the important effect of training is to increase oxygen delivery to and oxygen utilization by the active muscles during exercise. Thus, adaptations that reduce skeletal muscle anaerobiosis during exercise explain all the physiological, biochemical, and functional changes that develop with training. The historical basis for this model is the original research of Nobel Laureate A. V. Hill which was interpreted as evidence that oxygen consumption 'plateaus' during progressive exercise to exhaustion, indicating the development of skeletal muscle anaerobiosis. This review confirms that Hill's research failed to establish the existence of the 'plateau phenomenon' during exercise and argues that this core component of the historical model remains unproven. Furthermore, definitive evidence that skeletal muscle anaerobiosis develops during submaximal exercise at the anaerobic threshold initiating lactate production by muscle and its accumulation in blood is not currently available. The finding that exercise performance can improve and metabolism alter before there are measurable skeletal muscle mitochondrial adaptations could indicate that variables unrelated to oxygen use by muscle might explain some, if not all, training-induced changes. To accommodate these uncertainties, an alternate physiological model is proposed in which skeletal muscle contractile activity is regulated by a series of central, predominantly neural, and peripheral, predominantly chemical, regulators that act to prevent the development of organ damage or even death during exercise in both health and disease and under demanding environmental conditions. During maximal exercise, the peripheral regulation of skeletal muscle function and hence of oxygen use by skeletal muscle, perhaps by variables related to blood flow, would prevent the development of muscle rigor, especially in persons with an impaired capacity to produce ATP by mitochondrial or glycolytic pathways. Regulation of skeletal muscle contractile function by central mechanisms would prevent the development of hypotension and myocardial ischemia during exercise in persons with heart failure, of hyperthermia during exercise in the heat, and of cerebral hypoxia during exercise at extreme altitude. The challenge for future generations of exercise physiologists is to identify how the body anticipates the possibility of organ damage and evokes the appropriate control mechanism(s) at the appropriate instant.
β-Adrenoceptor blockers (β-blockers) are common first-choice drugs in the treatment of various cardiovascular disorders. Physical exercise performed during single-dose administration of β-blockers, however, is associated with an increased rate of perceived exertion; an effect which appears to be partly reduced with long term treatment. Although clinical doses of β-blockade may reduce heart rate by 30 to 35%, during maximal exercise cardiac output is not equally reduced. Accordingly, most studies have demonstrated increased stroke volume after β-blockade. This reduction in heart rate is typically accompanied by a decreased VO2max (5 to 15%) in both patients and healthy, trained subjects. This smaller reduction in VO2 max, as compared with the decrease in cardiac output, is the result of a partly compensating increased arteriovenous O2 difference. Work capacity as reflected by the ability to perform intense short term or more prolonged steady-state exercise is also impaired following β-blockade. β-Adrenoceptors can be subdivided into types β1- and β2. Blockers which are specific for either β1-receptors (β-selective blockers) or both β1- and β2 receptors (non-selective blockers) differ with regard to their effect on exercise performance. Exercise performance ability, irrespective of exercise intensity and duration, is impaired to a greater extent following non-selective than β-selective blockade at equal reductions in heart rate. This response stems from a decreased energy flux through glycogenolysis during non-selective blockade treatment. Individuals receiving β-blockade medication therefore show greater adaptive response to physical conditioning during treatment with β1-selective than non-selective blockade probably because of greater training intensity with the former therapy. Neither psychomotor performance nor muscular strength and power is negatively affected by β-blockade. Nevertheless, the ability to perform athletic events requiring high levels of motor control under emotional stress but not high levels of aerobic or anaerobic energy release, is probably increased during β-blockade.
This paper introduces a series of reports on the structure and function of the respiratory system of mammals. We propose and justify the hypothesis that structural design is a limiting factor for O2 flow at each level of the respiratory system. The background, the reasons, and the plan for the studies are described. The main approach is to compare the size of respiratory structures with maximal O2 consumption in a series of mammals spanning several orders or magnitude in body size. The papers that follow present the methods and results for maximal O2 consumption, pulmonary diffusing capacity, mitochondrial volume, and capillary density in muscles.
1. The effects of decreasing pH from 7.40 to 6.20 on the tension developed by direct activation of the myofilaments and by Ca2+ release from the sarcoplasmic reticulum were studied comparatively in segments of single cells of skeletal muscle (frog semitendinosus) and cardiac muscle (rat ventricle) from which the sarcolemma had been removed by micro-dissection (skinned muscle cells). 2. The concentration of free Ca2+ in the solutions was buffered with ethylene glycol-bis (beta-aminoethylether N,N'-tetraacetic acid (EGTA). The change of the buffer capacity of a given [total EGTA] caused by varying pH and the uncertainty about the value of the equilibrium constant for Ca-EGTA have been taken into account in the interpretation of the results. 3. Decreasing pH from 7.40 to 6.20 produced an increase in the [free Ca2+] required for the myofilaments to develop 50% of the maximum tension by a factor of about 5 in skinned cardiac cells but of only 3 in skeletal muscle fibres. In addition, acidosis depressed the maximum tension developed in the presence of a saturating [free Ca2+] by approximately the same amount in the two tissues. 4. The pH optimum for loading the sarcoplasmic reticulum of skinned fibres from skeletal muscle decreased when the pCa (-log [free Ca2+]) in the loading solution decreased. The optimum was pH 7.40-7.00 for a loading at pCa 7.75, pH 7.00-6.60 at pCa 7.00 and pH 6.60-6.20 at pCa 6.00. 5. The pH optimum for loading the sarcoplasmic reticulum of skinned cardiac cells with a solution at pCa 7.75 was about pH 7.40 as in skeletal muscle fibres. But the cardiac sarcoplasmic reticulum could not be loaded with a [free Ca2+] much higher than pCa 7.75 because a higher [free Ca2+] triggered a Ca2+-induced release of Ca2+ from the sarcoplasmic reticulum. 6. The pH optimum of about 7.40 for the loading of the cardiac sarcoplasmic reticulum was also optimum for the Ca2+-induced release of Ca2+ from it. 7. It was concluded that the effects of acidosis on the cardiac sarcoplasmic reticulum accentuate the depressive action of decreasing pH on the myofilaments. This may explain the pronounced depression of contractility observed during acidosis in cardiac muscle. In contrast, a moderate acidosis causes an effect on skeletal muscle sarcoplasmic reticulum that could compensate for the depressive action on the myofilaments, which is, in addition, less pronounced than in cardiac muscle.
This description of some of the present knowledge on skeletal muscle fibers, their metabolic potentials, and their interplay with the degree of physical activity has revealed that skeletal muscle of man has a very large capacity for adaptation. Moreover, this adaptability appears to be of utmost importance for the metabolic response as well as for performance. Although all this is true, it should not distract us from the fact that we are lacking the most important information. The questions that need to be answered are: What triggers the changes to take place? Which are the regulatory mechanisms?
13 male subjects were studied and placed in 3 groups. Each group exercised one leg with sprint (S), or endurance (E) training and the other leg oppositely or not at all (NT). Oxygen uptake (Vo 2 ), heart rate and blood lactate were measured for each leg separately and for both legs together during submaximal and maximal bicycle work before and after 4 weeks of training with 4–5 sessions per week. Muscle samples were obtained from the quadriceps muscle and assayed for succinate dehydrogenase (SDH) activity, and stained for myofibrillar AT Pase. In addition eight of the subjects performed after the training two‐legged exercise at 70% Vo 2 max for one hour. The measurements included muscle glycogen and lactate concentrations of the two legs as well as the blood flow and the a‐v difference for O 2 , glucose and lactate.
The improvement in Vo 2 max, the lowered heart rate and blood lactate response at submaximal work levels were only found when exercising with a trained leg (E or S). Part of the variables studied were markedly more changed with E as compared with S‐training. Although muscle fibre composition did not change a pronounced muscle adaptation took place with the training with enhancement of the SDH activity of the S and E legs while the NT‐leg did not change. Blood flow and oxygen uptake were similar in NT and S–E legs while femoral vein oxygen content was slightly lower in the trained as compared to the NT‐leg. Glycogen utilization was lowest in the trained leg with similar glucose uptake in all legs regardless of training status. Moreover, lactate was only continuously released from the NT‐leg. It is concluded that training induces marked local adaptations which not only affects the metabolic response to exercise but also are of importance eliciting an improved cardiovascular function.
Succinate dehydrogenase (SDH) and cytochrome oxidase activities in the lateral vastus of the human quadriceps femoris muscle together with total body VO2 max were followed during an 8-10 week period of endurance training (n = 13) and a successive 6 week period without training (n = 8). During the training period there was a gradual increase in both VO2 max and muscle oxidative enzyme activities, all being significantly different from the pre-training levels after 3 weeks of training. After 8 weeks of training VO2 max was 19%, vastus lateralis SDH 32%, and cytochrome oxidase activity 35% above the pre-training levels respectively. 6 weeks post training VO2 max was still 16% above the pre-training level, and not significantly different from the level at the end of training (p greater than 0.2). In contrast vastus lateralis SDH activity had returned to the pre-training level. Cytochrome oxidase activity had returned to the pre-training level within two weeks post-training. The significantly faster post-training decline in skeletal muscle oxidative enzyme activities in contrast to that of the VO2 max indicates that an enhancement of the oxidative potential in skeletal muscle is not a necessity for a high VO2 max. Moreover, the fast return to the pre-training level of both SDH and cytochrome oxidase activities indicate a high turnover rate of enzymes in the TCA cycle as well as the respiratory chain.
1. Five subjects trained for 8 weeks on a bicycle ergometer for an average of 40 min/day, four times a week at a work load requiring 80% of the maximal oxygen uptake ( V̇ O 2 max. ). V̇ O 2 max. determinations were performed, and muscle biopsies from the quadriceps femoris muscle (vastus lateralis) were taken before, as well as repeatedly during, the training period. The muscle biopsies were histochemically stained for fibre‐types (myofibrillar ATPase) and capillaries (amylase‐PAS method), and analysed biochemically for succinate dehydrogenase and cytochrome oxidase activities.
2. The training programme resulted in a 16% increase in V̇ O 2 max. , a 20% increase in capillary density, a 20% increase in mean fibre area, and an approximately 40% increase in the activities of succinate dehydrogenase and cytochrome oxidase.
3. The capillary supply to type I, IIA and IIB fibres, expressed as the mean number of capillaries in contact with each fibre‐type, relative to fibre‐type area, increased equally.
4. The present study shows that endurance training constitutes a powerful stimulus for capillary proliferation in human skeletal muscle.
The effects of a low intensity training regimen, consisting of two 7-week periods with an interspersed 8-week inactivity period were investigated in 16 sedentary men. A follow-up was made on 7 subjects after 38 additional weeks' training. Systemic as well as local effects were studied using exercise tests and leg muscle biopsies. The two 7-week training periods both resulted in a 6% increase in Vo2 max and a lowered heart rate during submaximal work. No persisting training effects were detected by exercise tests after inactivity. In skeletal muscle, however, striking differences in enzyme activity pattern and ultrastructure were observed between the two periods, indicating that some training effect of importance for muscle metabolic adaptation might have persisted during inactivity. It is suggested that such an effect might be associated with the local oxygen supply. During the 38-week training period there was a large increase in muscle metabolic capacity, but no change in maximal oxygen uptake. This separation of systemic and local training effects indicates a lack of a direct causal relationship between muscle metabolic potential and max imal oxygen uptake. It is suggested that the elevated muscle oxidative capacity is of importance for an increased endurance capacity.
The purpose of this study was to compare the oxygen cost of running as it relates to speed of running among the following four groups: trained male distance runners, trained female distance runners, untrained but active men and women. Each subject was given a series of treadmill tests during which Vo2 was measured at submaximal work loads. The linear regression equation was utilized to compute the relationship between Vo2 and running speed for each groups. The results indicated that the rate of increase in Vo2 for a given increase in running speed could be represented as a straight line and was the same for all groups (P greater than .05). The trained male runners had a significantly lower Vo2 (P less than .05) than those of the other three groups at any measured speed. The trained females and untrained males had significantly lower Vo2s than the untrained females (P less than .05) at any of the given range of speeds. No significant differences were observed between the untrained mean and trained women (P greater than .05). It was concluded that there were differences in the oxygen cost of running not only between the trained and untrained groups but also between males and females.
To study central circulation at different levels of hemoglobin (Hb) concentration, five subjects performed submaximal and maximal exercise in three different situations: 1) control, 2) after venesection of 800 ml of whole blood, and 3) after reinfusion of the red blood cells about 30-35 days after venesection. Maximal oxygen uptake (VO2 max) decreased from 4.27 l-min-1) at control to 4.03 l-min-1 after venesection (P less than 0.05) and increased to 4.61 l-min-1 after reinfusion (P less than 0.05). Maximal values on cardiac output (Q), heart rate (HR), and stroke volume (SV) were the same in the three situations. Thus, there was no compensatory increase in Qmax due to the lowered arterial oxygen content (Cao2) after venesection. An increase of the Cao2 (Hb concentration) and a lowering of the Cvo2 contributed equally to the increased VO2 max after reinfusion. At a given submaximal VO2, HR and blood lactates were increased at lowered Hb concentration and decreased at increased Hb concentration over control levels. Correlation coefficient for the change in Q in relation to the acute change in Hb concentration at a given submaximal VO2 was -0.49 (P less than 0.05).
In an effort to assess the effects of environmental heat stress on muscle metabolism during exercise, 6 men performed work in the heat (T
db = 41° C, RH = 15%) and cold (T
db = 9° C, RH = 55%). Exercise consisted of three 15-min cycling bouts at 70 to 85%, with 10-min rest between each. Muscle biopsies obtained from the vastus lateralis before and after each work bout were analyzed for glycogen and triglyceride content. Venous blood samples drawn before and after exercise were assayed for lactate, glucose, free fatty acids, hemoglobin, and hematocrit. Oxygen uptake, heart rates and rectal temperatures were all significantly higher during exercise in the heat. Blood lactate concentration was roughly twice as great during the heat experiments as that measured in the 9° C environment. Muscle glycogen utilization per 60 min was significantly greater in the heat (−74 m moles/kg-wet muscle) as compared to the cold exercise (−42 m moles/kg-wet muscle.) On the average, muscle triglyceride declined 23% during exercise in the cold and 11% in the heat. The findings of an enhanced glycolysis during exercise in the heat is compatible with earlier studies which demonstrate a decreased availability of oxygen due to a reduction in muscle blood flow.
Just what determines maximum O2 uptake (VO2max) has been the subject of much study and discussion over the years, with agreement among investigators still beyond reach. However, the evidence that in normal man VO2max is limited generally by the supply of O2 is substantial. Turning to the well-known steps of the pathway for O2 from atmosphere to mitochondria, the question then becomes how these steps in fact set the limit to VO2max. This presentation will stress two related hypotheses on how VO2max is set: 1) all steps in the O2 pathway interact in a manner that determines VO2max, such that an increase (decrease) in the transport capacity for any one step predictably increases (decreases) VO2max, and 2) a major component of this process is the rate at which O2 can move by diffusion from Hb in the red cell to the muscle mitochondria. A graphical analysis of this integrative hypothesis is presented with supporting data to show how all transport steps contribute to VO2max. This analysis ties together the ideas and data presented by the other speakers in this symposium, and also leads to predictions that are testable by feasible experiments.
This commentary demonstrates that VO2max depends, in part, on diffusive O2 transport; exercise hyperemia is necessary but not sufficient. Experiments and new mathematical models place the principal site of resistance to O2 diffusion between the surface of a red cell and the sarcolemma. The large drop in PO2 over this short distance is caused by high flux density and absence of heme protein O2 carrier in this region. PO2 gradients within red myocytes are shallow at high VO2 because myoglobin acts as O2 carrier and PO2 buffer. At high VO2 cell PO2 is less than 5 torr, the myoglobin P50. Low cell PO2 relative to blood PO2 is essential to a) maintain the driving force on diffusion as capillary PO2 falls, and b) to increase myoglobin-facilitated diffusion and the overall O2 conductance. O2 per se does not limit mitochondrial ATP production under normal circumstances because the low O2 drive on electron transport is compensated by greater phosphorylation and redox drives. These metabolic adaptations support transcapillary diffusion by defending VO2 at the low cell PO2 required to extract O2 from blood. Thus aerobic capacity is a distributed property, dependent on the interaction of transport and metabolism as a system.
The research performed over the last 100 yr in regard to oxygen transport during exercise is reviewed. Special focus is on major shifts in views held on which link may limit maximal oxygen uptake of an individual exercising with a large fraction of the muscle mass. Initially the pump capacity of the heart was proposed as the critical factor, a view basically unchallenged until results on the plasticity of muscle came about in the 1960-70s. The capillary bed of the muscle and its mitochondrial volumes can be enhanced with training. These adaptations were then suggested to be prerequisites for maximal oxygen uptake to become elevated. The pendulum is slowly swinging back again toward heart and lungs setting the upper limit for the oxygen transport. It appears to be in the range of 80-90 ml.kg-1.min-1 or 150-200 ml.kg-1 muscle.min-1, which can easily be consumed by a fraction of the muscle mass intensely contracting.
Twenty female and 45 male middle and long-distance runners, in training for the U.S. Olympic Trials, served as subjects. Ninety percent of both men and women subjects reached the Trials; eight women and 12 men qualified for the Olympic Games and five won medals. Each subject completed a VO2max and a series of submax treadmill runs, for the purpose of comparing heart rate (HR), VO2, and blood lactate (HLa) among men and women and among runners of various event specialties. Results showed the men to be taller, heavier, to have a lower six-site skinfold sum and a higher VO2max, than the women (P less than 0.05); there was no difference in age. When compared in running economy, men used less oxygen (ml.min-1.kg-1) at common absolute velocities, but VO2 (ml.km-1.kg-1) was not different between men and women at equal relative intensities (%VO2max). When men and women of equal VO2max were compared, the men were significantly more economical, using any method of comparison. Also, when comparisons of men and women of equal economy were made, it was found that the men had an even greater advantage over the "matched" women subjects than the mean VO2max comparison using all subjects. In looking at the SD (800-/1500-m runners), MD (3-K/5-K/10-K runners) and LD (marathon runners), it was found that the SD runners used the least oxygen (ml.min-1.kg-1) at speeds of marathon race pace and faster, but not at slower speeds. Men and women responded similarly in this regard. Running economy data for speeds slower than typical race paces, tended to show the LD runners to be most economical, suggesting that the speeds over which runners are tested plays an important part in determining which subjects are the most economical. It was concluded that at absolute running velocities, men are more economical than women, but when expressed in ml.km-1.kg-1 there are no gender differences at similar relative intensities of running. Also, when men and women of equal VO2max or equal economy are matched, the men show a better aerobic profile. It is recommended that economy data be collected up to speeds equal to over 90% VO2max.
It is well recognized that energy from CHO oxidation is required to perform prolonged strenuous (greater than 60% VO2 max) exercise. During the past 25 years, the concept has developed that muscle glycogen is the predominant source of CHO energy for strenuous exercise; as a result, the potential energy contribution of blood glucose has been somewhat overlooked. Although during the first hour of exercise at 70-75% VO2max, most of the CHO energy is derived from muscle glycogen, it is clear that the contribution of muscle glycogen decreases over time as muscle glycogen stores become depleted, and that blood glucose uptake and oxidation increase progressively to maintain CHO oxidation (Fig. 1.7). We theorize that over the course of several hours of strenuous exercise (i.e., 3-4 h), blood glucose and muscle glycogen contribute equal amounts of CHO energy, making blood glucose at least as important as muscle glycogen as a CHO source. During the latter stages of exercise, blood glucose can potentially provide all of the CHO energy needed to support exercise at 70-75% VO2max if blood glucose availability is maintained. During prolonged exercise in the fasted state, however, blood glucose concentration often decreases owing to depletion of liver glycogen stores. This relative hypoglycemia, although only occasionally severe enough to result in fatigue from neuroglucopenia, causes fatigue by limiting blood glucose (and therefore total CHO) oxidation. The primary purpose of CHO ingestion during continuous strenuous exercise is to maintain blood glucose concentration and thus CHO oxidation and exercise tolerance during the latter stages of prolonged exercise. CHO feeding throughout continuous exercise does not alter muscle glycogen use. It appears that blood glucose must be supplemented at a rate of approximately 1 g/min late in exercise. Feeding sufficient amounts of CHO 30 minutes before fatigue is as effective as ingesting CHO throughout exercise in maintaining blood glucose availability and CHO oxidation late in exercise. Most persons should not wait, however, until they are fatigued before ingesting CHO, because it appears that glucose entry into the blood does not occur rapidly enough at this time. It also may be advantageous to ingest CHO throughout intermittent or low-intensity exercise rather than toward the end of exercise because of the potential for glycogen synthesis in resting muscle fibers. Finally, CHO ingestion during prolonged strenuous exercise delays by approximately 45 minutes but does not prevent fatigue, suggesting that factors other than CHO availability eventually cause fatigue.
The study of skeletal muscle disorders is providing potentially important insights into regulatory mechanisms in human exercise and fatigue and information useful for diagnostic and treatment purposes. This review primarily concerned the general metabolic and physiological factors which set upper limits to performance of various types of exercise in patients with a variety of muscle disorders. From the standpoint of exercise performance, skeletal muscle diseases can be classified into three major groups. One group consists of primary disorders of muscle energy metabolism, including defects in muscle carbohydrate and lipid metabolism, disorders of mitochondrial electron transport, and abnormalities of purine nucleotide metabolism. Exercise performance largely reflects the capacity for ATP resynthesis. Oxidative phosphorylation is the dominant quantitative source of energy for ATP resynthesis under most exercise conditions. Consequently, patients with disordered oxidative metabolism (i.e., patients with defects in the availability or utilization of oxidizable substrate, such as those with phosphorylase or PFK deficiency or those with defects in mitochondrial electron transport) typically demonstrate severely impaired exercise performance. Intolerance to sustained exercise and premature fatigability are salient features of muscle oxidative disorders. Maximal oxygen uptake and maximal a-v O2 difference are markedly subnormal related to an attenuated muscle oxygen extraction. Muscle weakness and atrophy are less common. Anaerobic muscle performance is dramatically limited in patients with virtually complete defects of glycogenolysis/glycolysis but appears relatively normal in those with electron transport defects. A second major group of disorders includes patients with decreased muscle mass due to muscle necrosis, atrophy, and replacement of muscle by fat and connective tissue. These disorders are exemplified by the various muscular dystrophies (Duchenne's dystrophy, Becker's dystrophy, LG dystrophy, FSH dystrophy, and myotonic dystrophy) in which exercise performance is severely impaired due to muscle wasting and weakness in spite of largely normal pathways for muscle ATP resynthesis. In muscular dystrophy patients, the degree to which maximal oxygen uptake and anaerobic muscle performance are impaired appears to be a function of the severity of muscle weakness and atrophy. A third group of disorders includes patients with impaired activation of muscle contraction or relaxation. These disorders may be considered in two subcategories. In the first, impaired activation or relaxation of contractile activity is due to intrinsic muscle dysfunction (e.g., diseases associated with myotonia or periodic paralysis). In the second subcategory, there is impaired muscle activation due to a primary abnormality in the central nervous system, motor nerves, or neuromuscular junction.(ABSTRACT TRUNCATED AT 400 WORDS)
Recent evidence suggests that heavy exercise may lower the percentage of O2 bound to hemoglobin (%SaO2) by greater than or equal to 5% below resting values in some highly trained endurance athletes. We tested the hypothesis that pulmonary gas exchange limitations may restrict VO2max in highly trained athletes who exhibit exercise-induced hypoxemia. Twenty healthy male volunteers were divided into two groups according to their physical fitness status and the demonstration of exercise-induced reductions in %SaO2 less than or equal to 92%: 1) trained (T), mean VO2max = 56.5 ml.kg-1.min-1 (n = 13) and 2) highly trained (HT) with maximal exercise %SaO2 less than or equal to 92%, mean VO2max = 70.1 ml.kg-1.min-1 (n = 7). Subjects performed two incremental cycle ergometer exercise tests to determine VO2max at sea level under normoxic (21% O2) and mild hyperoxic conditions (26% O2). Mean %SaO2 during maximal exercise was significantly higher (P less than 0.05) during hyperoxia compared with normoxia in both the T group (94.1 vs. 96.1%) and the HT group (90.6 vs. 95.9%). Mean VO2max was significantly elevated (P less than 0.05) during hyperoxia compared with normoxia in the HT group (74.7 vs. 70.1 ml.kg-1.min-1). In contrast, in the T group, no mean difference (P less than 0.05) existed between treatments in VO2max (56.5 vs. 57.1 ml.kg-1.min-1). These data suggest that pulmonary gas exchange may contribute significantly to the limitation of VO2max in highly trained athletes who exhibit exercise-induced reductions in %SaO2 at sea level.(ABSTRACT TRUNCATED AT 250 WORDS)
This study investigated mechanisms used by horses and steers to increase O2 uptake and delivery (VO2) from resting to maximal rates and identified the mechanisms that enable horses to achieve higher maximal rates of O2 consumption (VO2max) than steers. VO2 and circulatory variables were measured while Standardbred trotting horses and steers (450-kg body mass) stood quietly and ran on a treadmill at speeds up to those eliciting VO2max. As VO2 increased in both species, heart rate and circulating hemoglobin (Hb) concentration increased, thereby increasing O2 delivery by the circulation, while cardiac stroke volume remained unchanged. At VO2max arterial PCO2 increased from its resting value in horses but was unchanged in steers, and arterial PO2 decreased in both species. Although the horses hypoventilated and were hypoxemic at VO2max, no significant decrease in arterial Hb saturation occurred. VO2max of the horses was 2.6 times higher than that of the steers and was associated with a 100% larger cardiac output, 100% larger stroke volume, and 40% higher Hb concentration, whereas heart rates at VO2max were identical in the two species. The higher cardiac output of the horses at VO2max resulted from a 1.2-fold higher mean arterial pressure and 1.6-fold lower peripheral tissue resistance (associated with a larger skeletal muscle capillary bed). Both the magnitude of the difference in VO2max between horses and steers and the mechanisms used to achieve it are the same as observed in smaller pairs of mammalian species with large variation in aerobic capacity.
One of the most fundamental beliefs in exercise physiology is that performance during maximum exercise of short duration is limited by the inability of the heart and lungs to provide oxygen at a rate sufficiently fast to fuel energy production by the active muscle mass. This belief originates from work undertaken in the 1920's by Hill and Lupton. A result is that most, if not all, of the studies explaining the effects of exercise training or detraining or other interventions on human physiology explain these changes in terms either of central adaptations increasing oxygen delivery to muscle or of peripheral adaptations that modify the rates of oxygen or fuel utilization by the active muscles. Yet a critical review of Hill and Lupton's results shows that they inferred but certainly did not prove that oxygen limitation develops during maximal exercise. Furthermore, more modern studies suggest that, if such an oxygen limitation does indeed occur during maximal exercise, it develops in about 50% of test subjects. Thus, an alternative mechanism may need to be evoked to explain exhaustion during maximal exercise in a rather large group of subjects. This review proposes that the factors limiting maximal exercise performance might be better explained in terms of a failure of muscle contractility ("muscle power"), which may be independent of tissue oxygen deficiency. The implications for exercise testing and the prediction of athletic performance are discussed.
Lactic acid accumulates in contracting muscle and blood beginning at approximately 50-70% of the maximal O2 uptake, well before the aerobic capacity is fully utilized. The classical explanation has been that part of the muscle is O2 deficient and therefore lactate production is increased to provide supplementary anaerobically derived energy. Currently, however, the predominant view is that lactate production during submaximal dynamic exercise is not O2 dependent. In the present review, data and arguments in support of and against the hypothesis of O2 dependency have been scrutinized. Data underlying the conclusion that lactate production during exercise is not O2 dependent were found to be 1) questionable, or 2) interpretable in an alternative manner. Experiments in human and animal muscles under various conditions demonstrated that the redox state of the muscle is reduced (i.e., NADH is increased) either before or in parallel with increases in muscle lactate. Based on experimental data and theoretical considerations, it is concluded that lactate production during submaximal exercise is O2 dependent. The amount of energy provided through the anaerobic processes during steady-state submaximal exercise is, however, low, and the role of lactate formation as an energy source is of minor importance. It is proposed that the achievement of increased aerobic energy formation under conditions of limiting O2 availability requires increases of ADP, Pi, and NADH and that the increases in ADP (and therefore AMP via the adenylate kinase equilibrium) and Pi will stimulate glycolysis, and the resulting increase in cytosolic NADH will shift the lactate dehydrogenase equilibrium toward increased lactate production.
Previous studies on skinned muscle fibers have demonstrated a direct effect of elevated levels of H+ ion to depress force production; however, the molecular basis for this effect is presently unknown. Here, whole troponin complexes were removed from skinned single fiber preparations of rat slow-twitch and fast-twitch muscles, and the effect of H+ ions on the resultant Ca2+-insensitive force was examined. The effect of H+ ions to depress force was found to be virtually identical in untreated control fibers activated in the presence of Ca2+ and in fibers activated in the absence of Ca2+ by troponin removal. Thus, the effect of H+ ions to depress force occurs at a step in activation beyond the disinhibition of the thin filament by Ca2+, probably involving reductions in the number of attached cross-bridges or in the force per attachment.
Fourteen competitive cyclists who possessed a similar maximum O2 consumption (VO2 max; range, 4.6-5.0 l/min) were compared regarding blood lactate responses, glycogen usage, and endurance during submaximal exercise. Seven subjects reached their blood lactate threshold (LT) during exercise of a relatively low intensity (group L) (i.e., 65.8 +/- 1.7% VO2 max), whereas exercise of a relatively high intensity was required to elicit LT in the other seven men (group H) (i.e., 81.5 +/- 1.8% VO2 max; P less than 0.001). Time to fatigue during exercise at 88% of VO2 max was more than twofold longer in group H compared with group L (60.8 +/- 3.1 vs. 29.1 +/- 5.0 min; P less than 0.001). Over 92% of the variance in performance was related to the % VO2 max at LT and muscle capillary density. The vastus lateralis muscle of group L was stressed more than that of group H during submaximal cycling (i.e., 79% VO2 max), as reflected by more than a twofold greater (P less than 0.001) rate of glycogen utilization and blood lactate concentration. The quality of the vastus lateralis in groups H and L was similar regarding mitochondrial enzyme activity, whereas group H possessed a greater percentage of type I muscle fibers (66.7 +/- 5.2 vs. 46.9 +/- 3.8; P less than 0.01). The differing metabolic responses to submaximal exercise observed between the two groups appeared to be specific to the leg extension phase of cycling, since the blood lactate responses of the two groups were comparable during uphill running. These data indicate that endurance can vary greatly among individuals with an equal VO2 max.(ABSTRACT TRUNCATED AT 250 WORDS)
1. The effects of variations in pH between 7.00 and 6.20 on Ca2+ -activated tension development and maximum velocity of shortening (Vmax) were examined in skinned single skeletal fibres from rat slow-twitch soleus and fast-twitch superficial (s.v.l.) and deep (d.v.l.) regions of the vastus lateralis muscle. 2. At pH 6.50, Vmax was depressed to a similar degree in each of the soleus, d.v.l., and s.v.l. fibres. Lowering pH to 6.20 resulted in a further decline in Vmax in all fibres; however, differences between the slow fibres, identified by SDS-polyacrylamide gel electrophoresis, and fast fibres were apparent, with soleus retaining a significantly greater proportion of its control Vmax (0.83 +/- 0.03 in soleus vs. 0.69 +/- 0.03 in s.v.l.; mean +/- S.E.M.). 3. Maximum force production decreased significantly as pH was reduced. Peak force at pH 6.50, relative to that at pH 7.00, was significantly greater in soleus (0.80 +/- 0.01) than in the s.v.l. (0.75 +/- 0.01) fibres. At pH 6.20 these differences between slow and fast fibres were still greater, in that soleus fibres generated significantly greater relative forces (0.73 +/- 0.01) than did d.v.l. (0.67 +/- 0.02) or s.v.l. (0.63 +/- 0.02) fibres. 4. As pH was lowered the tension-pCa relationship shifted to the right (i.e. to higher [Ca2+]), indicating a reduction in the Ca2+ sensitivity of tension development. The [Ca2+] necessary to achieve half-maximal tension in both the slow- and fast-twitch fibres increased approximately 5-fold when pH was lowered from 7.00 to 6.20. Furthermore, in the case of the soleus, the Ca2+ threshold for tension development was 45 times greater at pH 6.20 than at pH 7.00, while in the fast-twitch fibres, this increase was 4-fold. 5. Increased [H+] differentially affected the steepness of the tension-pCa relationship between slow and fast fibres. As pH was lowered, the steepness of the lower portion of the tension-pCa curve increased in the soleus and decreased in d.v.l. and s.v.l., suggesting that apparent positive co-operativity of tension development had increased in soleus and decreased in d.v.l. and s.v.l. fibres. 6. These results (1) demonstrate an increased resistance to H+ ion-mediated contractile dysfunction in slow- compared to fast-twitch single fibres, and (2) support the hypothesis that muscular fatigue resulting from short-term, intense muscular contraction may in part be related to elevated H+ ion concentration.
In summary, we have shown that the design of the pulmonary system from the architectural capacities of the lung parenchyma and respiratory muscles to the remarkable, multi-level neural integration of breathing pattern and respiratory muscle recruitment is clearly intended for the exercising state. Furthermore, the system shows remarkable capability for true adaptation, both phylogenetically and even within only a few generations within a species, when preservation of the organism's ability to survive and function is at stake. At the same time there are limits to the system's homeostatic capabilities, and these appear in instances other than the "usual" ones, where the capabilities for gas transport and utilization beyond the lung (i.e., by the cardiovascular and musculo-skeletal systems) surpass those of the lung and chest wall, such as during exercise in certain pulmonary disease states or in alien environments or in the highly trained. Exercise-induced hypoxemia in the thoroughbred horse is a different type of dominance of the superior locomotor control system, because their extraordinary capability to produce and sustain a very high limb velocity dictates requirements for airway flow rates which may surpass the mechanical capabilities of the lung and perhaps even the chest wall. So this hypothesis does indeed suggest that the healthy pulmonary system may become a so-called "limiting" factor to oxygen transport and utilization and to CO2 transport and elimination, at least during short-term maximum exercise in the highly trained. On the one hand, the idea is especially appealing in a philosophical sense because of its conceptual tidiness and its confirmation of the premise that no organ system has limitless functional capacity; on the other hand, given the long list of our still untested speculations, we could use a bit more data.