Boosting physical performance in SD rats through brain-targeted delivery of caffeine-loaded transferrin liposomes.

This study aimed to explore the impact of caffeine (CAF) encapsulated in transferrin-modified, sterically-stabilized liposomes (Tf-SSL) on the physical performance of rats, specifically forelimb grip strength, running, and swimming. The brain-targeted drug delivery system, Tf-SSL, was used for the administration of caffeine. 168 male Sprague-Dawley (SD) rats were randomly assigned to different groups, including swimming, running, running wheel, and strength groups. Each group was further subdivided into high, medium, and low dose free caffeine (HCAF, MCAF, LCAF) and Tf-SSL CAF groups, along with a control group (CON). The strength, swimming, and running groups underwent training for four weeks, three times per week. The running wheel group was placed in rearing cages for a one-week adaptation period. After the final training session, the resistance, swimming, running, and running wheel exercise capacities of the rats were tested. The rats were administered treatment via tail vein injection, while the blank CON group received 0.9 % saline solution without treatment throughout the entire process. The results demonstrated a Tf-SSL CAF group encapsulation rate of 70.58 ± 5.14 %. Increasing the concentration of supplemented caffeine led to enhanced forelimb grip strength in rats, with significant differences observed in HCAF alone group, medium-dose Tf-SSL CAF (MTf-SSL CAF), and high-dose Tf-SSL CAF (HTf-SSL CAF) groups compared to the CON group. In the running and swimming experiments, higher caffeine supplementation concentrations correlated with increased running and swimming time to exhaustion, and the MTf-SSL CAF group showed longer running and swimming time compared to the HCAF alone group. The results of rat striatal dopamine levels indicated that increased caffeine supplementation concentrations led to higher dopamine secretion, with significantly different striatal concentrations in the HCAF group, MTf-SSL CAF group, and HTf-SSL CAF group compared to the CON group. The running wheel experiment revealed that rats in the medium- and high-dose Tf-SSL CAF groups exhibited greater 6-h running distances than the HCAF group and CON group. In conclusion, caffeine supplementation improved the physical performance of rats, with the high concentration CAF group outperforming the low and medium concentration groups. Furthermore, Tf-SSL CAF demonstrated superior physical enhancement compared to caffeine supplementation alone.

Sex differences in human performance.

Sex as a biological variable is an underappreciated aspect of biomedical research, with its importance emerging in more recent years. This review assesses the current understanding of sex differences in human physical performance. Males outperform females in many physical capacities because they are faster, stronger and more powerful, particularly after male puberty. This review highlights key sex differences in physiological and anatomical systems (generally conferred via sex steroids and puberty) that contribute to these sex differences in human physical performance. Specifically, we address the effects of the primary sex steroids that affect human physical development, discuss insight gained from an observational study of 'real-world data' and elite athletes, and highlight the key physiological mechanisms that contribute to sex differences in several aspects of physical performance. Physiological mechanisms discussed include those for the varying magnitude of the sex differences in performance involving: (1) absolute muscular strength and power; (2) fatigability of limb muscles as a measure of relative performance; and (3) maximal aerobic power and endurance. The profound sex-based differences in human performance involving strength, power, speed and endurance, and that are largely attributable to the direct and indirect effects of sex-steroid hormones, sex chromosomes and epigenetics, provide a scientific rationale and framework for policy decisions on sex-based categories in sports during puberty and adulthood. Finally, we highlight the sex bias and problem in human performance research of insufficient studies and information on females across many areas of biology and physiology, creating knowledge gaps and opportunities for high-impact studies.

Effects of Baduanjin Exercise on lung function and 6 min walk in COPD patients: a systematic review and meta-analysis.

COPD is a public health problem of global concern, which seriously affects the quality of life of patients and is also the third leading cause of death from non-communicable diseases. To investigate the effect of Ba duan jin exercise on lung function and the results of a 6-min walking trial in patients with stable COPD. Literature databases such as Web of Science, Embase, PubMed, Cochrane Library, Chinese Biomedical Literature (CBM), CNKI, Wanfang Data and VIP were searched by computer, the search period is up to January 2024. Literature screening, quality evaluation and data extraction were carried out independently by two researchers. And use RevMan 5.3 software and StataMP 18 (64-bit) software to process the relevant outcome indicators. A total of 16 RCT studies with 1184 patients were included. The meta-analysis results showed that compared with the control group, Ba Duan Jin exercise could improve FEV1 (MD = 0.29, 95% CI (0.20, 0.37), P < 0.0001), FEV1/FVC (%) (MD = 3.86, 95% CI (2.24, 5.47), P < 0.00001), and 6-min walking distance (MD = 45.41, 95% CI (33.93, 56.89), P < 0.00001) in stable COPD patients. The results of subgroup analysis based on the duration of the intervention cycle, research quality, and intervention frequency showed that periodic Ba Duan Jin exercise can significantly improve the relevant lung function levels to varying degrees. At the same time, the intervention effect of Ba Duan Jin exercise during the implementation process is also affected by the duration of the exercise cycle, exercise frequency, and the completion of the exercise plan. Ba Duan Jin exercise has a positive improvement effect on lung function and 6-min walking distance in stable COPD patients. In the process of exercise implementation, attention should be paid to cultivating exercise habits, stabilizing and improving attendance rates, and strictly implementing training techniques to achieve the best clinical outcomes for these patients.

Long-Term Incidence of Bradycardia and Pacemaker Implantations Among Cross-Country Skiers: A Cohort Study.

BACKGROUND: Bradycardia is more common among well-trained athletes than in the general population, but the association with pacemaker implantations is less known. We investigated associations of endurance training with incidence of bradycardia and pacemaker implantations, including sex differences and long-term outcome, in a cohort of endurance trained individuals. METHODS: All Swedish skiers who completed >1 race in the cross-country skiing event Vasaloppet between 1989 and 2011 (n=209 108) and a sample of 532 290 nonskiers were followed until first event of bradycardia, pacemaker implantation, or death, depending on end point. The Swedish National Patient Register was used to obtain diagnoses. Cox regression was used to investigate associations of number of completed races and finishing time in Vasaloppet with incidence of bradycardia and pacemaker implantations. In addition, Cox regression was used to investigate associations of pacemaker implantations with death in skiers and nonskiers. RESULTS: Male skiers had a higher incidence of bradycardia (adjusted hazard ratio [aHR], 1.19 [95% CI, 1.05-1.34]) and pacemaker implantations (aHR, 1.17 [95% CI, 1.04-1.31]) compared with male nonskiers. Those who completed the most races and had the best performances exhibited the highest incidence. For female skiers in Vasaloppet, the incidence of bradycardia (aHR, 0.98 [95% CI, 0.75-1.30]) and pacemaker implantations (aHR, 0.98 [95% CI, 0.75-1.29]) was not different from that of female nonskiers. The indication for pacemaker differed between skiers and nonskiers, with sick sinus syndrome more common in the former and third-degree atrioventricular block in the latter. Skiers had lower overall mortality rates than nonskiers (aHR, 0.16 [95% CI, 0.15-0.17]). There were no differences in mortality rates by pacemaker status among skiers. CONCLUSIONS: In this study, male endurance skiers had a higher incidence of bradycardia and pacemaker implantations compared with nonskiers, a pattern not seen in women. Among male skiers, those who completed the most races and had the fastest finishing times had the highest incidence of bradycardia and pacemaker implantations. Within each group, mortality rates did not differ in relation to pacemaker status. These findings suggest that bradycardia associated with training leads to a higher risk for pacemaker implantation without a detrimental effect on mortality risk.

Lactate threshold evaluation in swimming using a sweat lactate sensor: A prospective study.

Since assessing aerobic capacity is key to enhancing swimming performance, a simple and widely applicable technology should be developed. Therefore, we aimed to noninvasively visualize real-time changes in sweat lactate (sLA) levels during swimming and investigate the relationship between lactate thresholds in sweat (sLT) and blood (bLT). This prospective study included 24 university swimmers (age: 20.7 s ± 1.8 years, 58% male) who underwent exercise tests at incremental speeds with or without breaks in a swimming flume to measure heart rate (HR), bLT, and sLT based on sLA levels using a waterproof wearable lactate sensor attached to the dorsal upper arm on two different days. The correlation coefficient and Bland-Altman methods were used to verify the similarities of the sLT with bLT and personal performance. In all tests, dynamic changes in sLA levels were continuously measured and projected onto the wearable device without delay, artifacts, or contamination. Following an initial minimal current response, with increasing speed the sLA levels increased substantially, coinciding with a continuous rise in HR. The speed at sLT strongly correlated with that at bLT (p < 0.01 and r = 0.824). The Bland-Altman plot showed a strong agreement (mean difference: 0.08 ± 0.1 m/s). This prospective study achieved real-time sLA monitoring during swimming, even with vigorous movement. The sLT closely approximated bLT; both were subsequently validated for their relevance to performance.

Effects of 60 versus 30 Minutes of Pilates Exercise on Cervicothoracic Alignment, Muscle Strength, and Endurance in University Students with Upper Crossed Syndrome.

Background/Objectives: This study determined the effects of 60 min or 30 min Pilates program on cervicothoracic alignment, muscular strength, and endurance in university students with upper-crossed syndrome (UCS). Methods: Twenty-six university students with UCS were randomly allocated into 60 min Pilates (60 PG, n = 9), 30 min Pilates (30 PG, n = 9), and control (CG, n = 8) groups. The 60 and 30 PG students participated in the Pilates program, focusing on relaxation, stability, mobility, and strengthening of the cervical, thoracic, and scapular muscles for 60 or 30 min per session, twice a week, for 12 weeks. Cervicothoracic alignment was measured using BodyStyle to determine craniovertebral angle (CVA), forward shoulder angle (FSA), head position angle (HPA), head tilt angle (HTA), and kyphosis angle (KA). We measured the muscular strength and endurance of the shoulder on the dominant side. Results: After the intervention, CVA, HPA, HTA, and KA significantly improved in the 60 and 30 PG (all p < 0.01) but not in the CG (p > 0.05). There were no significant differences between the 60 and 30 PG at 4, 8, and 12 weeks. Shoulder strength differed between shoulder flexion and horizontal abduction (p < 0.01). Shoulder endurance differed between extension, flexion, and horizontal abduction (p < 0.05, p < 0.01, and p < 0.001, respectively). Conclusions: This study confirmed the effectiveness of the Pilates program in improving cervicothoracic sagittal alignment and shoulder muscular function in university students with UCS. Additionally, the effects of participating in 60 and 30 min Pilates programs were found to be equivalent. Therefore, encouraging busy university students to participate in at least 30 min of the Pilates program is important.

Myocardial Fibrosis in Young and Veteran Athletes: Evidence from a Systematic Review of the Current Literature.

Background: Exercise is associated with several cardiac adaptations that can enhance one's cardiac output and allow one to sustain a higher level of oxygen demand for prolonged periods. However, adverse cardiac remodelling, such as myocardial fibrosis, has been identified in athletes engaging in long-term endurance exercise. Cardiac magnetic resonance (CMR) imaging is considered the noninvasive gold standard for its detection and quantification. This review seeks to highlight factors that contribute to the development of myocardial fibrosis in athletes and provide insights into the assessment and interpretation of myocardial fibrosis in athletes. Methods: A literature search was performed using the PubMed/Medline database and Google Scholar for publications that assessed myocardial fibrosis in athletes using CMR. Results: A total of 21 studies involving 1642 endurance athletes were included in the analysis, and myocardial fibrosis was found in 378 of 1595 athletes. A higher prevalence was seen in athletes with cardiac remodelling compared to control subjects (23.7 vs. 3.3%, p < 0.001). Similarly, we found that young endurance athletes had a significantly higher prevalence than veteran athletes (27.7 vs. 19.9%, p < 0.001), while male and female athletes were similar (19.7 vs. 16.4%, p = 0.207). Major myocardial fibrosis (nonischaemic and ischaemic patterns) was predominately observed in veteran athletes, particularly in males and infrequently in young athletes. The right ventricular insertion point was the most common fibrosis location, occurring in the majority of female (96%) and young athletes (84%). Myocardial native T1 values were significantly lower in athletes at 1.5 T (p < 0.001) and 3 T (p = 0.004), although they had similar extracellular volume values to those of control groups. Conclusions: The development of myocardial fibrosis in athletes appears to be a multifactorial process, with genetics, hormones, the exercise dose, and an adverse cardiovascular risk profile playing key roles. Major myocardial fibrosis is not a benign finding and warrants a comprehensive evaluation and follow-up regarding potential cardiac disease.

Cardiac function and autonomic cardiac function during a multi-stage cycling event: a brief report.

Introduction: Prolonged and repeated exercise performed during an ultra-endurance event can induce general and cardiac fatigue known as exercise-induced cardiac fatigue. Our objective was to find a possible correlation between the cardiac function and the autonomic cardiac function. Methods: During a multistage ultra-endurance event, a female well-trained cyclist underwent daily rest echocardiography and heart rate variability measurements to assess the cardiac function and the cardiac autonomic function. Results: The athlete completed 3,345 km at 65% of her maximum heart rate and 39% of her maximum aerobic power. A progressive improvement of the systolic function for both the left ventricle and the right ventricle was observed during the event. Discussion: Alterations were observed on the cardiac autonomic function with an imbalance between sympathetic and parasympathetic, but there was no sign of a significant correlation between the cardiac function and the autonomic cardiac function and no signs of cardiac fatigue either. Further analysis should be performed on a larger sample to confirm the obtained results.

Sex differences in the associations between right heart structure and peak exercise capacity parameters in amateur cyclists.

Introduction: Right heart changes and their association with exercise capacity, including sex differences, are still being investigated. We analysed right heart structure and its relationship with exercise capacity parameters in amateur cyclists. Materials and methods: A cross-sectional study involving 215 consecutive adult amateur cyclists, who underwent resting transthoracic echocardiography and a cardiopulmonary exercise test (CPET) to exhaustion was performed. Results: The median age of participants was 29 years (IQR 24-37), 71% of them were men. The mean training time was 6 h/week, and 90% participated in vigorous or moderate physical activity. Men had larger right ventricular diameters (basal - RVD1, mid-cavity - RVD2 and longitudinal - RVD3) compared to women (40.9 vs. 37.6 mm, p = 0.0005, 28.7 vs. 26.3 mm, p = 0.03, 92.2 vs. 81.9 mm, p < 0.0001). Indexing for body surface area revealed comparable right atrial volume (RAVI) between sexes (24.1 vs. 22.7 mL/m2). Men achieved higher peak exercise capacity parameters [O2 pulse, oxygen consumption (VO2) and workload] in CPET. Multivariate linear regression models revealed a positive association between peak VO2, workload and O2 pulse with RAVI in women but not with RVD1 or RVD3. Conversely, these parameters showed a positive association with RVD3 and RVD1 but not with RAVI in men. Conclusion: Sex differences exist in the relationship between right heart structural parameters and peak exercise capacity descriptors in amateur cyclists. Better exercise capacity during CPET to exhaustion is associated with greater RAVI in women but a greater RVD1 and RVD3 in men. These findings suggest different mechanisms of right heart adaptation to training in men and women.

Recipe for fatigue: sleep, work patterns, and well-being of galley workers on surface ships of the US Navy.

Study Objectives: The purpose of the study was to compare the fatigue levels, work/rest patterns, health-related behaviors, and well-being of galley workers with other sailors on US Navy ships while underway. Methods: Analysis was based on a retrospective comparison of data from 3 fit-for-duty groups of sailors: 67 galley workers, 192 non-watchstanders, and 466 watchstanders. Participants completed questionnaires (Epworth Sleepiness Scale [ESS], Insomnia Severity Index [ISI], Pittsburgh Sleep Quality Index [PSQI], and Profile of Mood States [POMS]) and activity logs, and wore actigraphs. Results: Galley workers slept MD = 6.57 (IQR = 1.42) h/d and worked MD = 12.8 (IQR = 2.42) h/d. Approximately 84% of the galley workers were classified as poor sleepers, ~57% reported having excessive daytime sleepiness (EDS), and ~38% reported elevated insomnia symptoms. Compared to non-watchstanders, galley workers had worse scores on POMS (total mood disturbance, tension-anxiety, depression, anger-hostility, fatigue, and confusion-bewilderment), ESS, ISI, and PSQI. Compared to non-watchstanders, galley workers had a higher risk for symptoms of EDS (75%), symptoms of clinically relevant insomnia (126%), and for being classified as poor sleepers (27%). Galley workers slept less and worked on average 2 h/d more than non-watchstanders. Compared to watchstanders, galley workers had worse ESS, ISI, and anger-hostility scores. More watchstanders napped compared to galley workers. Conclusions: Although they are considered day workers, the sleep patterns, fatigue levels, and mood of galley workers are comparable to, or worse than, watchstanders or other non-watchstanders. To ameliorate the effects of long work hours on sailor well-being, ship leadership should consider adopting strategies to improve galley workers' well-being.

Plasticity of the heart in response to changes in physical activity.

The human heart is very adaptable, with chamber size, wall thickness and ventricular stiffness all modified by periods of inactivity or exercise training. Herein, we summarize the cardiac adaptations induced by changes in physical activity, ranging from bed rest and spaceflight to endurance exercise training, while also highlighting how the ageing process (a long-term model of inactivity) affects cardiac plasticity. Severe inactivity during bed rest or spaceflight leads to cardiac atrophy and ventriculo-vascular stiffening. Conversely, endurance training induces eccentric hypertrophy and enhances ventricular compliance, and can be used as an effective countermeasure to prevent adverse cardiac changes during prolonged periods of bed rest or spaceflight. With sedentary ageing, the heart undergoes concentric remodelling and irreversibly stiffens at advanced age. Specifically, older adults who initiate endurance training later in life are unable to improve ventricular compliance and diastolic function, suggesting reduced cardiac plasticity with advanced age; however, lifelong exercise training prevents age-associated cardiac remodelling and maintains cardiac compliance of older adults at a level similar to those of younger healthy individuals. Nevertheless, there are still many knowledge gaps related to cardiac remodelling and changes in cardiac function induced by bed rest, exercise training and spaceflight, as well as how these different stimuli may interact with advancing age. Future studies should focus on understanding what factors (sex, age, heritability, etc.) may influence the heart's responsiveness to training or deconditioning, as well as understanding the long-term cardiac consequences of spaceflight beyond low-Earth orbit with the added stimulus of galactic cosmic radiation.

Effect of a multi-component exercise intervention on recovery of walking ability in stroke survivors: A Systematic Review with Meta-Analysis.

OBJECTIVE: To evaluate whether Multi-component exercise (MCE) is more effective than single exercise in improving walking ability in stroke patients. DESIGN: Systematic review and meta-analysis. DATA SOURCES: A systematic search of PubMed, Embase, Web of Science, Cochrane Library, and CINAHL from the establishment of each database to February 2024 was performed. A combination of medical subject headings and free-text terms relating to stroke, exercise were searched. STUDY SELECTION: Randomized controlled trials treating stroke survivors with multi-component exercise were included. The control groups received conventional treatments such as conventional treatment or no intervention or sham training; the experimental groups received multi-component exercise. The outcome measures were walking endurance, gait speed and balance ability. DATA EXTRACTION: The data extraction form was completed by two independent reviewers.The risk of bias was assessed using the Cochrane Risk of Bias tool for randomized Controlled Trials.Review Manager 5.4 software was used for data analysis.Subgroup analysis and sensitivity analysis were used to supplement the results with higher heterogeneity.The Preferred Reporting Project for Systematic Reviews and Meta-analyses 2020 guidelines were followed. DATA SYNTHESIS: 12 studies were included. Meta-analyses found that compared with the control group,MCE significantly affected gait speed (MD = 0.11; 95%CI 0.06, 0.16, I2 = 0%), but the effect on balance ability was not statistically significant.Subgroup analysis showed that MCE (≥60 min) was effective in improving walking endurance. These results suggest that multi-component exercise improves walking endurance and walking speed in stroke patients. CONCLUSION: Multi-component exercise helps improve the gait speed of stroke survivors. Prolonging the multi-component exercise time may have a better effect on improving the walking endurance of stroke patients.

Mechanical Deviations in Stride Characteristics During Running in the Severe Intensity Domain Are Associated With a Decline in Muscle Oxygenation.

We explored the impact of running in the severe intensity domain on running mechanics and muscle oxygenation in competitive runners by investigating the relationship between mechanical deviations from typical stride characteristics and muscle oxygen saturation (SmO2) in the quadriceps muscle. Sixteen youth competitive runners performed an 8-min exhaustive running test on an outdoor track. Running mechanics were continuously monitored using inertial measurement units. Rectus femoris SmO2 and total hemoglobin (a measure of blood volume) were continuously monitored by near-infrared spectroscopy. One-class support vector machine (OCSVM) modeling was employed for subject-specific analysis of the kinematic data. Statistical analysis included principal component analysis, ANOVA, and correlation analysis. Mechanical deviations from typical stride characteristics increased as the running test progressed. Specifically, the percentage of outliers in the OCSVM model rose gradually from 2.2 ± 0.8% at the start to 43.6 ± 28.2% at the end (p < 0.001, mean ± SD throughout). SmO2 dropped from 74.3 ± 8.4% at baseline to 10.1 ± 6.8% at the end (p < 0.001). A moderate negative correlation (r = -0.61, p = 0.013) was found between the average SmO2 and the percentage of outlier strides during the last 15% of the run. During high-intensity running, alterations in running biomechanics may occur, linked to decreased quadriceps muscle oxygenation. These parameters highlight the potential of using running kinematics and muscle oxygenation in training to optimize performance and reduce injury risks. Our research contributes to understanding biomechanical and physiological responses to endurance running and emphasizes the importance of individualized monitoring.

Return to sport activity following ultrasonographic diagnosis and conservative management of spontaneous injuries of the serratus cervicis ventralis and serratus thoracis ventralis muscles in 11 endurance horses.

OBJECTIVE: To describe the clinical diagnosis, ultrasound findings, and outcome of 11 endurance horses with injuries to the serratus ventralis thoracis (SVT) or serratus ventralis cervicis (SVC) muscle. ANIMALS: 11 endurance horses competing in medium- to high-level competitions and presenting with lameness caused by injuries to the SVT or SVC muscle, as confirmed by ultrasonography. CLINICAL PRESENTATION: Physical examinations revealed swelling caudal to the shoulder region associated with dorsocranial displacement of the scapula and edema of the ventral thorax for horses with SVT injuries. Swelling cranial to the scapula and edema of the pectoral area were identified among horses with injuries to the SVC. RESULTS: Dynamic examinations revealed moderate-to-severe reduction of the cranial phase of the stride at the walk; at the trot, a lameness score of 2 to 3/5 was assigned (modified American Association of Equine Practitioners Lameness Scale). Ultrasonography revealed moderate-to-severe increases in size of the muscle body, heterogeneous echogenicity, loss of the striated muscle pattern, and varying degrees of perimuscular edema. All horses were able to resume full training and competition in an average of 216 days (range, 74 to 362 days) and 148 days (range, 112 to 309 days) for injuries of the SVT and SVC, respectively. CLINICAL RELEVANCE: This case series is the first to describe the clinical and ultrasonographic features of spontaneous injuries to the SVT or SVC. Ultrasonography for diagnosis was simple and well tolerated by the horses.

Training for Elite Team-Pursuit Track Cyclists-Part II: A Comparison of Preparation Phases in Consecutive World-Record-Breaking Seasons.

PURPOSE: To compare the training characteristics of an elite team pursuit cycling squad in the 3-month preparation phases prior to 2 successive world-record (WR) performances. METHODS: Training data of 5 male track endurance cyclists (mean [SD]; age 23.4 [3.46] y; body mass 80.2 [2.74] kg; 4.5 [0.17] W·kg-1 at LT2; maximal aerobic power 6.2 [0.27] W·kg-1; maximal oxygen uptake 65.9 [2.89] mL·kg-1·min-1) were analyzed with weekly total training volume by training type and heart rate, power output, and torque intensity distributions calculated with reference to the respective WRs' performance requirements. RESULTS: Athletes completed 805 (82.81) and 725 (68.40) min·wk-1 of training, respectively, in each season. In the second season, there was a 32% increase in total track volume, although track sessions were shorter (ie, greater frequency) in the second season. A pyramidal intensity distribution was consistent across both seasons, with 81% of training, on average, performed below LT1 power output each week, whereas 6% of training was performed above LT2. Athletes accumulated greater volume above WR team pursuit lead power (2.4% vs 0.9%) and torque (6.2% vs 3.2%) in 2019. In one athlete, mean single-leg-press peak rate of force development was 71% and 46% higher at mid- and late-phases, respectively, during the preparation period. CONCLUSIONS: These findings provide novel insights into the common and contrasting methods contributing to successive WR team pursuit performances. Greater accumulation of volume above race-specific power and torque (eg, team pursuit lead), as well as improved neuromuscular force-generating capacities, may be worthy of investigation for implementation in training programs.

Training for Elite Team-Pursuit Track Cyclists-Part I: A Profile of General Training Characteristics.

PURPOSE: To profile the training characteristics of an elite team pursuit cycling squad and assess variations in training intensity and load accumulation across the 36-week period prior to a world-record performance at the 2018 Commonwealth Games. METHODS: Training data of 5 male track endurance cyclists (mean [SD]; age 21.9 [3.52] y; 4.4 [0.16] W·kg-1 at anaerobic threshold; 6.2 [0.28] W·kg-1 maximal oxygen uptake 68.7 [2.99] mL kg·min-1) were analyzed with weekly total training volume and heart rate, power output, and torque intensity distributions calculated with reference to their 3:49.804 min:s.ms performance requirements for a 4-km team pursuit. RESULTS: Athletes completed 543 (37) h-1 of training across 436 (16) sessions. On-bike activities accounted for 69.9% of all training sessions, with participants cycling 11,246 (1139) km-1 in the training period of interest, whereas 12.7% of sessions involved gym/strength training. A pyramidal intensity distribution was evident with over 65% and 70% of training, respectively, performed at low-intensity zone heart rate and power output, whereas 5.3% and 7.7% of training was performed above anaerobic threshold. The athletes accumulated 4.4% of total training volume at, or above, their world-record team pursuit lead position torque (55 N·m). CONCLUSIONS: These data provide updated and novel insight to the power and torque demands and load accumulation contributing to world-record team pursuit performance. Although the observed pyramidal intensity distribution is common in endurance sports, the lack of shift toward a polarized intensity distribution during taper and competition peaking differs from previous research.

Estimation of minimal clinically important difference for 6-minute walking distance in patients with acute stroke using anchor-based methods and credibility instruments.

BACKGROUND AND PURPOSE: Stroke impairs a patient's ability to walk. In patients with acute stroke, a 6-min walking distance (6MWD) is recommended to assess walking function. Minimal clinically important difference (MCID) is used to determine the effectiveness of rehabilitation; however, the MCID for 6MWD has not been adequately validated. This study aimed to estimate the MCID of 6MWD, a measure of walking endurance, in patients with acute stroke using anchor-based methods. METHODS: Based on the change in 6MWD from baseline to the follow-up measurement 2 weeks later, the MCID was estimated using anchor-based methods (receiver operator operating characteristic curves, predictive and adjustment models) with a patient- and therapist-rated global rating of change scale (p-GRC, t-GRC) as external anchors. The accuracy of "meaningful change" was estimated from the area under the curve. Using MCID's credibility instruments, the credibility of each anchor was evaluated. Using the credibility instrument, high credibility was defined as satisfying 3/5 of the Core criteria and 6/9 of all criteria. RESULTS: The analysis included 58 patients. The MCID for each anchor was 78.7-100.0 m for p-GRC, and 95.2-99.5 m for t-GRC. The p-GRC demonstrated excellent accuracy (area under the curve >0.8). With p-GRC as anchors, over 50% of patients showed improvement. The p-GRC satisfied the core criterion of 3/5 and all criteria of 6/9 on the reliability instrument. The t-GRC demonstrated low reliability and satisfied the core criterion of 2/5 and all criteria of 3/9. DISCUSSION: Since the percentage of improved groups exceeded 50%, the adjusted model was useful in the anchor-based method. Therapists may not accurately capture patient fatigue and subjective symptoms, potentially affecting the correlation between the 6MWD change score and the t-GRC and, consequently, the reliability instrument. The p-GRC showed high accuracy and reliability; therefore, the MCID was estimated to be 78.7 m.

Difference in expiratory flow limitations development in normoxia and hypoxia in healthy individuals.

The present study investigated the maintenance/repeatability of expiratory flow limitation (EFL) between normoxia and hypoxia. Fifty-one healthy active individuals (27 men and 24 women) performed a lung function test and a maximal incremental cycling test in both normoxia and hypoxia (inspired oxygen fraction = 0.14) on two separate visits. During exercise in normoxia, 28 participants exhibited EFL (55%). In hypoxia, another cohort of 28 participants exhibited EFL. The two groups only partly overlapped. Individuals with EFL only in normoxia reported lower maximal ventilation values in hypoxia than in normoxia (n=5; -13.5 ± 7.8%) compared to their counterparts with EFL only in hypoxia (n=5; +6.7 ± 6.3%) or without EFL (n=18; +5.1 ± 10.3%) (p=0.004 and p<0.001, respectively). EFL development may be induced by different mechanisms in hypoxia vs. normoxia since the individuals who exhibited flow limitation were not the same between the two environmental conditions. This change seems influenced by the magnitude of the maximal ventilation change.

Comparison of acute physiological responses between one long and two short sessions of moderate-intensity training in endurance athletes.

Purpose: To compare acute physiological responses and perceived training stress between one long and two short time- and intensity-matched sessions of moderate-intensity training in endurance athletes. Methods: Fourteen male endurance athletes (VO2max: 69.2 ± 4.2 mL·min-1·kg-1) performed one 6 × 10-min interval session (SINGLE) and two 3 × 10-min interval sessions interspersed with 6.5 h recovery (DOUBLE) of moderate-intensity training on two separate days, while running in the laboratory, using a counterbalanced cross-over trial. The two training days were separated into a first part/session (interval stage 1-3) and second part/session (interval stage 4-6). Respiratory variables, heart rate (HR), blood lactate concentrations (BLa), and rating of perceived exertion (RPE) were collected during sessions, whereas supine heart rate (HR) was assessed in a 60-min recovery period following sessions. Measures of perceived training stress (1-10) were assessed in the morning of the subsequent day. Results: HR, Bla, and RPE increased in the second compared to first part of SINGLE (168 ± 7 vs. 173 ± 7 bpm, 2.60 ± 0.75 vs. 3.01 ± 0.81 mmol·L-1, and 13.4 ± 1.0 vs. 14.8 ± 1.1-point, respectively, all p < 0.05). HR and Bla decreased in the second compared to first session of DOUBLE (171 ± 9 vs. 166 ± 9 bpm and 2.72 ± 0.96 vs. 2.14 ± 0.65 mmol·L-1, respectively, both p < 0.05). SINGLE revealed higher supine HR in the recovery period following sessions (65.4 ± 2.5 vs. 60.7 ± 2.5 bpm p < 0.05), session RPE (sRPE, 7.0 ± 1.0 vs. 6.0 ± 1.3-point, p = .001) and sRPE training load (929 ± 112 vs. 743 ± 98, p < 0.001) compared to DOUBLE. In the subsequent morning, increased levels of perceived fatigue and muscle soreness were observed following SINGLE compared to DOUBLE (7.0 ± 2.5 vs. 8.0 ± 1.0-point, p = .049 and 6.0 ± 2.5 vs. 7.0 ± 2.5-point, p = .002, respectively). Conclusion: One long moderate-intensity training session was associated with a duration-dependent "drift" in physiological responses compared to two short time- and intensity-matched sessions, thereby suggesting a higher overall training stimulus. Simultaneously, the lower cost of the two shorter sessions indicates that such organization could allow more accumulated time at this intensity. Overall, these findings serve as a starting point to better understand the pros and cons of organizing moderate-intensity training as one long versus shorter sessions performed more frequently (e.g., as "double threshold training") in endurance athletes.

The Method but Not the Protocol Affects Lactate-Threshold Determination in Competitive Swimmers.

PURPOSE: The study validated variables corresponding to lactate threshold (LT) in swimming. Speed (sLT), blood lactate concentration (BLLT), oxygen uptake (VO2LT), and heart rate (HRLT) corresponding to LT were calculated by 2 different incremental protocols and validated in comparison with maximal lactate steady state (MLSS). METHODS: Ten competitive swimmers performed a 7 × 200-m front-crawl incremental "step test" with 2 protocols: (1) with 30-second rests between repetitions (short-rest incremental protocols) and (2) on a 5-minute cycle (swim + rest time, long-rest incremental protocols). Five methods were used for the assessment of sLT and corresponding BLLT, VO2LT, and HRLT: intersection of 2 lines, Dmax, modified Dmax, visual inspection, and intersection of combined linear and exponential regression lines. Subsequently, swimmers performed two to three 30-minute continuous efforts to identify speed (sMLSS) and physiological parameters corresponding to MLSS. RESULTS: Both protocols resulted in similar sLT and corresponding physiological variables (P > .05). Bland-Altman plots showed agreement between protocols (sLT, bias: -0.017 [0.002] m·s-1; BLLT, bias: 0.0 [0.5] mmol·L-1; VO2LT, bias: -0.1 [2.2] mL·kg-1·min-1; HRLT. bias: -2 [8] beats·min-1). However, sLT calculated by modified Dmax using short rest was higher compared with speed at MLSS (1.346 [0.076] vs 1.300 [0.101] m·s-1; P < .05). CONCLUSIONS: Calculated sLT, BLLT, VO2LT, and HRLT using all other methods in short-rest and long-rest incremental protocols were no different compared with MLSS (P > .05). Both 7 × 200-m protocols are valid for determination of sLT and corresponding physiological parameters, but the modified Dmax method may overestimate sLT.