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Introduction: The recoverability of athletes at different performance levels may be dissimilar. This study aimed to compare differences in fatigue level and recovery ability between champions and those who did not make it to the top three in the taekwondo category of the National High School Games. Methods: Nine champions were assigned to the excellent group (EXG) and 15 athletes who did not make it to the top three were assigned to the general group (GEG). Before and after the match, countermovement jump (CMJ) and maximum voluntary isometric contraction were evaluated. The selected parameters were jump height, 50ms, 100ms and maximal rate of force development (50ms, 100ms and maximal RFD). The differences in fatigue and recoverability between groups were examined with paired sample t-tests; independent sample t-tests were used to compare differences in percentage change in fatigue and recoverability between groups. Results: The 50ms RFD, 100ms RFD, and maximal RFD after the first match of the GEG were significantly lower than their levels before the first match (p < .05), while the group did not show significant fatigue (p >.05). The jump height of both the GEG and the EXG was significantly lower than that at pre-match (p < .05). The GEG showed significantly higher percentage reductions in 50ms RFD and 100ms RFD than the EXG (p < .05). However, the percentage change in recoverability did not differ significantly between the groups (p >.05). Conclusions: The 50ms RFD, 100ms RFD, and max RFD of the GEG were significantly reduced after the first match, indicating the group's evident fatigue level. Percentage reductions in 50ms RFD and 100ms RFD after the first match were significantly higher in the GEG than in the EXG. Both groups' CMJ height before the second match did not return to the same level as that before the first match. This study suggests that 50ms RFD and 100ms RFD can be used as an evaluation index for taekwondo athletes to determine their degree of fatigue and whether they have a competitive advantage. CMJ height may be an indicator of recoverability of taekwondo athletes. [ABSTRACT FROM AUTHOR]

This study aimed to systematically review the literature and perform a meta-regression to determine the level of agreement between maximal lactate steady state (MLSS) and critical power (CP). Considered eligible to include were peer-reviewed and "gray literature" studies in English, Spanish, and Portuguese languages in cyclical exercises. The last search was made on March 24, 2022, on PubMed, ScienceDirect, SciELO, and Google Scholar. The study's quality was evaluated using 4 criteria adapted from the COSMIN tool. The level of agreement was examined by 2 separate meta-regressions modeled under Bayesian's methods, the first for the mean differences and the second for the SD of differences. The searches yielded 455 studies, of which 36 studies were included. Quality scale revealed detailed methods and small samples used and that some studies lacked inclusion/exclusion criteria reporting. For MLSS and CP comparison, likely (i.e., coefficients with high probabilities) covariates that change the mean difference were the MLSS time frame and delta criteria of blood lactate concentration, MLSS number and duration of pauses, CP longest predictive trial duration, CP type of predictive trials, CP model fitting parameters, and exercise modality. Covariates for SD of the differences were the subject's maximal oxygen uptake, CP's longest predictive trial duration, and exercise modality. Traditional MLSS protocol and CP from 2- to 15-minute trials do not reflect equivalent exercise intensity levels; the proximity between MLSS and CP measures can differ depending on test design, and both MLSS and CP have inherent limitations. Therefore, comparisons between them should always consider these aspects. [ABSTRACT FROM AUTHOR]

The purpose of this study was to assess the effects of a child-specific school-based high-intensity interval training (HIIT) implemented into physical education (PE) classes on various hemodynamic parameters and heart rate variability indices. Forty-six students (age 11 ± 1 year) were randomized into an intervention (INT n = 22) and a control group (CON n = 24). During a 12-week period, the INT and CON groups participated in regular PE twice weekly (45-90 minutes). The INT group received HIIT during the first 20 minutes of the 2 PE classes. Systolic and diastolic blood pressure, total peripheral resistance, aortic pulse wave velocity (aPWV), heart rate, SD of normal to normal heartbeat intervals, the root mean square of successive differences between normal heartbeats (RMSSD), the proportion of differences between adjacent normal to normal heartbeat intervals of more than 50 ms, low-frequency power, high-frequency power, and the LF/HF ratio were assessed before and after the experimental period. A p value ≤0.05 was considered statistically significant. Forty students (20 INT; 20 CON) were included in the analysis. A significant time x group interaction was detected for aPWV(p = 0.05, η² = 0.099), RMSSD (p = 0.010, η² = 0.161), low-frequency power (p = 0.009, η² = 0.165), high-frequency power (p < 0.001, η² = 0.272), and the LF/HF ratio (p < 0.001, η² = 0.354). The INT group revealed significant improvements for the respective parameters. School-based HIIT can induce improvements in cardiovascular parameters. These results highlight the potential of embedding HIIT within the school setting, offering a time-efficient exercise intervention. [ABSTRACT FROM AUTHOR]

The aim of this study was twofold: (a) to examine the differences on physical indexes between players of different playing positions and (b) to reveal the correlations between their physical parameters and the running profile within the weekly microcycles. The subjects (n = 44) were separated into five positions: central defenders (n = 7), wide defenders (n = 9), midfielders (n = 13), wingers (n = 8) and strikers (n = 7), and all of them belonged to a professional 1st division European team during the 2020–21 and 2021–22 seasons. An incremental treadmill protocol was used to assess the VO2max, vVO2max and the vRER in the last week before the regular season. Then, during the first semesters, external load data were collected for two consecutive seasons to analyze the running profiles of the different positions. There were no differences on physical parameters between the players of various positions, but interestingly there were different correlations with the external load during the microcycles. Central defenders did not show any correlation. For the other positions, correlations were found between respiratory exchange ratio (vRER) and metabolic power efforts (MPWEF) (p = 0.028, r = 0.721) for wide defenders, between vRER and medium intensity accelerations (ACC2) (p = 0.004, r = 0.741) for midfielders, medium intensity decelerations (DEC2) (p = 0.01, r = 0.685), metabolic power zone 5 (MPW5) (p = 0.016, r = 0.652), MPWEF (p = 0.005, r = 0.725), and also between maximal rate of oxygen consumption (VO2max) and high intensity decelerations (DEC3) (p = 0.045, r = 0.564), metabolic power zone 4 (MPW4) (p = 0.026, r = 0.614), MPW5 (p = 0.017, r = 0.646), MPWEF (p = 0.01, r = 0.685). A correlation between velocity on VO2max (vVO2max) and ACC2 (p = 0.038, r = 0.733), MPW5 (p = 0.005, r = 0.873), and MPWEF (p = 0.009, r = 0.84) was found for the wingers. Finally, there was a correlation between vRER and MPWEF (p = 0.026, r = 0.866), and between vVO2max and high intensity accelerations (ACC3) (p = 0.03, r = 0.801) for the strikers. Our study supports that the external load of players in different positions during the training sessions is correlated with their physical indexes. These correlations are determined mostly by their tactical role, but not from their physical level, as there were no differences. [ABSTRACT FROM AUTHOR]

In recent years, there has been a surge in research examining the correlation between training load and injury risk among professional football players. One prominent model proposed for this purpose is the acute-to-chronic workload ratio (ACWR). This review aimed to compile studies focusing on professional footballers that explored the association between the ACWR and injury risk, offering specific usage guidelines. The findings revealed that the relationship between the ACWR and injury risk in professional football remains inconclusive. Among studies supporting this relationship, many utilized a coupled ACWR derived from GPS data. Interestingly, the duration of the ACWR (1:2, 1:3, 1:4) did not seem to significantly impact this association. In conclusion, the pool of relevant studies is limited, warranting further research for more definitive conclusions. While the ratio shows promise in its connection with injury risk, establishing precise thresholds (e.g., reduced injury likelihood) remains challenging given the current research landscape. [ABSTRACT FROM AUTHOR]

Objective: Exercise and physical activity as an essential factor and an integral part in the prevention of standard management of diabetes, however, most people with diabetes are not active enough. The objective of this research was to identify the obstacles hindering the participation of diabetic patients in sports activities in Khuzestan province. Materials and Methods: The study followed an exploratory-applicative approach, utilizing a mixed qualitative-quantitative methodology. The qualitative section involved 18 knowledgeable experts, while the quantitative section included all diabetes patients in Khuzestan province. The sample size for the quantitative section was determined to be 384 patients, based on Morgan's table. Data collection in the qualitative part was conducted through semi-structured interviews, resulting in the extraction of 46 concepts, 19 sub-categories, and 8 main categories over three stages. In the quantitative part, a researcher-designed questionnaire was used, based on the interview findings. The reliability of the questionnaire was assessed using Cronbach's alpha coefficient, which yielded a value of 0.90. Data analysis was performed using SPSS and Smart PLS software. Results: The findings indicated that various factors act as barriers to the participation of diabetic patients in sports activities, including self-actualization (7.79), environmental (6.10), educational and research (5.83), managerial (5.72), cultural (2.85), physical and supportive (2.8), time (2.62), and economic (2.15) factors. Conclusion: Therefore, it is recommended that sports and health officials in the province take measures to alleviate these obstacles and improve the quality of life for diabetic patients. [ABSTRACT FROM AUTHOR]

This systematic review aimed to evaluate the effectiveness of the independent or combined use of nutritional ergogenic aids belonging to Group A of the ABCD classification by the Australian Institute of Sport (AIS) in the context of cycling (caffeine, creatine, sodium bicarbonate, beta-alanine, nitrates, and glycerol). A comprehensive search was carried out using three databases: PubMed, Scopus, and Web of Science. All the databases were searched for Randomized Controlled Trials or crossover design studies assessing the effects of supplementation on cycling performance in comparison with placebos in healthy adults. The methodological quality of each study was evaluated using the Physiotherapy Evidence Database scale. Thirty-six articles involving 701 participants were included in this review, examining supplementation with caffeine (n = 5), creatine (n = 2), sodium bicarbonate (n = 6), beta-alanine (n = 3), and nitrates (n = 8). Additionally, supplemental combinations of caffeine and creatine (n = 3), caffeine and sodium bicarbonate (n = 3), caffeine and nitrates (n = 1), creatine and sodium bicarbonate (n = 1), and sodium bicarbonate and beta-alanine (n = 4) were analyzed. A benefit for cyclists' athletic performnce was found when consuming a caffeine supplement, and a potential positive effect was noted after the consumption of sodium bicarbonate, as well as after the combination of caffeine and creatine. However, no statistically significant effects were identified for the remaining supplements, whether administered individually or in combination. [ABSTRACT FROM AUTHOR]

This document contains a collection of studies on various topics related to sports and fitness. The first study focuses on the validity of wearable sensors in measuring respiratory frequency in soccer players. The second study explores the effects of aerobic and sprint endurance training on adolescent women soccer players. The third study examines the differences in motor competence between children practicing open skills sports and closed skills sports. The fourth study investigates the role of preparticipation screening in detecting silent coronary artery disease in master athletes. The fifth study looks at the correlation between mild traumatic brain injuries in boxers and the release of cell free mitochondrial DNA. Lastly, the document includes a study comparing the proportionality of young water polo and soccer players based on maturity offset. [Extracted from the article]

Background: Mobile Applications (App) have reshaped approaches to the intervention and monitoring of physical training. The Safe Runner App is an example. However, evidence of the reliability of the Safe Runner App to obtain aerobic parameters still needs to be investigated. Aims: The present study aimed to analyze the accuracy and reproducibility of power parameters and aerobic capacity derived from incremental testing on a treadmill using an application for mobile devices. Methods: Twenty participants performed a maximum incremental test and retest. Maximum oxygen consumption (VO2MAX), maximum heart rate (HRMAX), maximum velocity (VMAX), anaerobic threshold heart rate (HRAT), and anaerobic threshold velocity (VAT) were estimated. A two-way ANOVA was used for dependent samples or the Friedman test for non-parametric data, and effect size (Cohens-d), intraclass correlation coefficient (ICC), and Bland–Altman were used to verify reliability. Results: No differences between the test and retest (p > 0.05) were observed for all variables assessed. The variables VO2MAX (d = 0.05), HRMAX (d = 0.01), and VMAX (d = 0.05) showed a trivial effect size, while HRAT (d = 0.11) and VAT (d = 0.16) showed to be trivial/low. The ICC values for VO2MAX (0.996), HRMAX (0.955), HRAT (0.939), VMAX (0.996), and VAT (0.913) demonstrated reliability. The Bland–Altman plots demonstrated an agreement of the variables. The variables VO2MAX, HRAT, and VAT were identical when comparing the Safe Runner App and Excel software. Conclusion: The Safe Runner App is reliable in identifying aerobic training parameters. [ABSTRACT FROM AUTHOR]

Purpose: Given the controversial use of the Acute:Chronic Workload Ratio (ACWR) in determining the availability of soccer players for training and matches, this study aimed at verifying how many professional soccer players had an ACWR above 1.5 (considered a 'danger zone') immediately before the exposure (training or match) in which they sustained a hamstring muscle injury. Methods: Forty-eight male soccer players of a professional team were monitored through global positioning system (GPS) in this 2-season retrospective study (10 participated in both seasons and 38 in a single season). The ACWR of total distance, high-speed running distance, very high-speed running distance, and the number of actions performed >19 km/h were calculated before all hamstring injuries and included in the analysis. Results: Twenty players sustained hamstring injuries. There was no time effect on the group's daily workload or the average workload over the 4 weeks before the injury (p > 0.05). Fifteen players (i.e., 75%) had ACWR below 1.5 for the four GPS metrics immediately before the training or match in which they sustained a hamstring injury. Five players (25%) were classified in the 'danger zone' (i.e., ACWR > 1.5) for the very high-speed running distance; 3 of these players were also in the 'danger zone' for high-speed running distance and the number of actions >19 km/h, and 2 players for the total distance. Conclusion: Since three-quarters of the hamstring injuries affecting professional soccer players were preceded by ACWR values below 1.5 in all GPS metrics, it is prudent for medical/coaching staff exercise caution when considering the ACWR 'danger zone' as the primary metric for determining player availability for training or matches. [ABSTRACT FROM AUTHOR]

Background: Diabetes mellitus (DM) requires patients to take on a high level of responsibility for their daily care. Thus, care for people with diabetes is moving toward patients taking an active role in their own health care. Objective: To evaluate the impact of self‑management care on glycemic control in individuals with DM and determine the correlation between glycated hemoglobin (A1C) levels and self‑management practices. Material and Methods: A cross‑sectional descriptive study was conducted among diabetes patients at a diabetic center in Armed Forces Military hospitals, Southern region. A questionnaire of demographic and clinical information and self‑management measured with the Diabetes Self‑Management Questionnaire was used. Glycemic control was assessed using HbA1c levels. Results: The study involved 255 patients with diabetes, of which 61.2% were females and 81.6% aged ≥41 years. The average diabetic self‑management score was 6.49 on a scale of 10. The mean glucose self‑management subscale score was 7.83 points, while the mean dietary control (DC) subscale score was 4.89. The patients had a mean physical activity (PA) subscale score of 6.31 and 8.75 for healthcare usage. Patients with higher education were significantly less likely to have poor glycemic control. Diabetes duration was significantly and positively correlated with poorer glycemic control. Mean perceived PA and DC scores were significantly associated with glycemic control. Conclusion: Type 2 diabetes patients had satisfactory self‑care practices. Many did not achieve the target glycemic control for diabetes. [ABSTRACT FROM AUTHOR]

Cold water immersion (CWI) and percussive massage therapy (PMT) are commonly used recovery techniques in team sports. In particular, despite its wide use, PMT has been scarcely investigated in the literature, especially regarding neuromuscular measures and in comparison with other techniques. This study aimed to evaluate and compare the acute and short-term effects (24 h) of CWI and PMT on muscle strength, contractile properties, and soreness after exercise. A randomized crossover study was performed on sixteen male soccer players (22 years, 20–27) who participated in three experimental sessions involving a fatiguing protocol consisting of a Yo-Yo Intermittent Endurance Test followed by 3 × 10 squat jumps and a wall sit for 30 s, and 12 min of recovery including CWI (10 °C water), bilateral PMT on the anterior and posterior thigh, or passive resting. Outcomes were assessed immediately after the exercise protocol, after the recovery intervention, and at 24 h. Isometric knee extension (IKE) and flexion (IKF) and tensiomyography (TMG) were assessed. Muscle soreness and fatigue were scored from 0 to 10. PMT increased strength after the treatment (p = 0.004) and at 24 h (p = 0.007), whereas no significant differences were found for the other two recovery modalities. At post-recovery, compared to CON, CWI resulted in a longer TMG contraction time (p = 0.027). No significant differences were found at 24 h. Finally, PMT and CWI enhanced muscle soreness recovery compared to passive rest (F4,60 = 3.095, p = 0.022, pη2 = 0.171). Preliminary results from this study suggest that PMT might improve isometric strength after strenuous exercise, and both PMT and CWI reduce muscle soreness perception, while the effects on TMG parameters remain controversial. [ABSTRACT FROM AUTHOR]

The current study investigated the associations between female football players' training loads and their sleep variations. The sample included 21 female elite football players from a Norwegian top-league club with a mean age of 24 years (±2.8). Sleep duration, sleep quality, and training load were monitored every day over 273 consecutive days with a Somnofy sleep monitor based on ultra-wideband (IR-UWB) pulse radar and Doppler technology, and a FIFA-approved STATSports APEX 10 Hz GPS tracking system monitoring players' training loads. A multivariate analysis of variance (MANOVA) was conducted to investigate the relationships between the players' training loads and sleep. It was revealed that very high training loads were associated with reduced time in bed (p = 0.005), total sleep time (p = 0.044)), and rapid eye movement (p < 0.001). The present findings show that the female football players' sleep was disrupted when the training load, based on total distance (TDI), was very high. It appears to be a point where their sleep is somewhat consistent through low, medium, and high training loads, but with disrupted sleep when the training load reaches a very high level. Considering the reduced TIB after a very high training load, there should be suggested strategies to improve their sleep, such as extended TIB, to aid in longer TST and improved recovery. [ABSTRACT FROM AUTHOR]

A variable pacing profile is common in different endurance events. In these races, several factors, such as changes in elevation or race dynamics, lead participants to perform numerous surges in intensity. These surges are so frequent that certain events, such as cross-country (XC) skiing, mountain biking (MTB), triathlon, and road cycling, have been termed "intermittent endurance events". The characteristics of these surges vary depending on the sport: MTB and triathlon require athletes to perform numerous short (<10 s) bouts; XC skiing require periods of short- and moderate-(30 s to 2 min) duration efforts, while road cycling is comprised of a mix of short-, moderate-, and long-duration (>2 min) bouts. These bouts occur at intensities above the maximal metabolic steady state (MMSS), with many efforts performed at intensities above the athletes' maximal aerobic power or speed (MAP/MAS) (i.e., supramaximal intensities). Given the factors that influence the requirement to perform surges in these events, athletes must be prepared to always engage in a race with a highly stochastic pace. The aim of this review is to characterize the variable pacing profile seen in endurance events and to discuss how the performance of multiple maximal and supramaximal surges in intensity can affect how athletes fatigue during a race and influence training strategies that can lead to success in these races. [ABSTRACT FROM AUTHOR]

Aim: The aim of this study was to analyze changes in cardiorespiratory fitness of athletes who had surgery following a lesion of the anterior cruciate ligament of the knee., Methods: Two groups of 12 athletes at the regional level underwent surgical repair to rebuild the external anterior crossed ligament of the knee (central third bone patellar tendon bone autograft and doubled semitendinosus/doubled gracilis autograft techniques). All subjects were evaluated before and after surgery within 7 days: the first group underwent maximal incremental tests with the upper limbs, and the second group measurement of resting cardiac volumes., Results: Surgery followed by a few days of confinement generated a quick and significant reduction in the maximal oxygen consumption (-7%, P<0.05) and peak aerobic power (-8%, P<0.05). End diastolic volume and stroke volume were reduced, by 23% and 27% respectively (P<0.05). A significant reduction of ejection fraction was also observed (P<0.05). The mean left ventricular ejection fraction was 65% before the surgery 60% after 7 days' of hospitalization., Conclusion: In sportsmen, 7 days of hospitalization due to surgery of the knee led to resting cardiac unsuitability characterized by a significant reduction in the stroke volume. These elements could involve decreased aerobic fitness and should encourage the hospital practitioner to propose a program of aerobic training in addition to conventional rehabilitation.

The purpose of this study was to apply the "critical velocity" concept to short intermittent high-intensity running exercises in prepubescent girls and boys and to compare the running performances obtained either by intermittent or continuous exercise runs. Eleven 8 to 11-year-old children underwent a maximal graded field test to determine peak oxygen uptake (peakVO2) and maximal aerobic velocity (MAV). During the six following sessions, they randomly performed three continuous runs (90, 100, and 110% of MAV) and three intermittent runs (120, 130, and 140% of MAV) until exhaustion. Intermittent exercises consisted of repeated 15 s runs each one separated by a 15 s passive recovery interval. For continuous as well as intermittent exercises, distance versus time to exhaustion (TTE) relationships were calculated to determine continuous (CVc) and intermittent (CVi) critical velocities. Values for peakVO2 and MAV were 45.8 +/- 5.3 ml x kg(-1) x min(-1) and 10.5 +/- 1.0 km h(-1), respectively. For the whole population, a significant relationship was found between the distance to exhaustion (DTE) and TTE for continuous (r2= 0.99, P < 0.05) and intermittent exercises (r2 = 0.99, P < 0.05). Significant relationships were found between peakVO2 and both CVc (r2= 0.60, P < 0.01) and CVi (r2= 0.47, P < 0.05). In conclusion, as for continuous exercises, a linear relationship was found between DTE and TTE for short high-intensity intermittent exercises. CVc was significantly related to peakVO2, while a significant lower relationship was found between peakVO2 and CVi.

We assessed expiratory airflow limitation (exp FL) in 18 healthy prepubescent children (6 girls and 12 boys, 10.1 +/- 0.3 years old), and examined how it might modulate regulation of tidal volume (V(T)) during exercise. The children performed a maximal incremental exercise on a cycle ergometer, preceded and followed by pulmonary function tests. Throughout exercise, breathing flow-volume loops were plotted into the maximal flow-volume loop (MFVL) measured at rest. End-expiratory and end-inspiratory lung volumes were estimated by measuring expiratory reserve volume relative to forced vital capacity (ERV/FVC), and inspiratory reserve volume relative to forced vital capacity (IRV/FVC), respectively. The exp FL, expressed as a percentage of V(T), was defined as the part of the tidal breath meeting the boundary of the MFVL. Ten children (FL) presented an exp FL at peak exercise (range, 16-78% of V(T)), and the remaining 8 constituted a non-flow-limited group (NFL). At peak exercise, FL presented a higher IRV/FVC and lower ERV/FVC (P < 0.01) than NFL children, demonstrating two different exercise breathing patterns. These results suggest that the NFL regulated V(T) at high lung volume, avoiding exp FL, while the FL breathed at low lung volume, leading to exp FL. At peak exercise, FL presented lower values of minute ventilation (P<0.05) and oxygen uptake (P<0.05) than NFL. Nevertheless, oxygen arterial saturation and dyspnea were similar in the two groups. In conclusion, ventilatory constraints may occur in healthy prepubescent children and result in relative dynamic hyperinflation or expiratory flow limitation., ((c) 2005 Wiley-Liss, Inc.)

We studied mechanical ventilatory constraints in 13 aerobically trained (Tr) and 11 untrained (UT) prepubescent children by plotting the exercise flow-volume (F-V) loops within the maximal F-V loop (MFVL) measured at rest. The MFVL allowed to determine forced vital capacity (FVC) and maximal expiratory flows. Expiratory and inspiratory reserve volumes relative to FVC (ERV/FVC and IRV/FVC, respectively) were measured during a progressive exercise test until exhaustion. Breathing reserve (BR) and expiratory flow limitation (expFL), expressed in percentage of tidal volume (V(T)) and defined as the part of the tidal breath meeting the boundary of the MFVL, were measured. Higher FVC and maximal expiratory flows were found in Tr than UT (P < 0.05) at rest. Our results have shown that during exercise, excepting one subject, all Tr regulated their V(T) within FVC similarly during exercise, by breathing at low lung volume at the beginning of exercise followed breathing at high lung volume at strenuous exercise. In UT, ERV/FVC and IRV/FVC were regulated during exercise in many ways. The proportion of children who presented an expFL was nearly the same in both groups (approximately 70% with a range of 14 to 65% of V(T)), and no significant difference was found during exercise concerning expFL. However, higher ventilation (V(E)), ERV/FVC, and dyspnea associated with lower BR, IRV/FVC, and SaO2 were reported at peak power in Tr than UT (P < 0.05). These results suggest that, because of their higher Ve level, trained children presented higher ventilatory constraints than untrained. These may influence negatively the SaO2 level and dyspnea during strenuous exercise.

The purpose of this study was to test the hypothesis that subjects having a shorter time constant for the fast component of VO2 kinetics in a transition from rest to constant exercise would maintain their speed for a longer time during repeated sprint exercise (RSE). Eleven male soccer players completed a graded test, two constant exercises at 60% maximal aerobic speed and RSE, consisting of fifteen 40-m sprints alternated with 25 s of active recovery. All the tests were performed on the field (200 m indoor track). The parameters of the VO2 kinetics (time delay, time constant, and amplitude of the primary phase) during the two constant exercises were modeled. All subjects elicited VO2 during the RSE. A significant correlation was found between VO2 and the relative decrease in speed during the 15 sprints (r=0.71; p < 0.05), but not between VO2 and the cumulated time for the 15 sprints (r=0.48; p > 0.05). There were significant correlations between the time constant of the primary phase and the relative decrease in speed during the 15 sprints (r=0.80; p < 0.01) and the cumulated time for the 15 sprints (r=0.80; p < 0.01). These results suggest that individuals with faster VO2 kinetics during constant load exercise might also have a faster adjustment of VO2 during RSE leading to a shorter cumulated time and a lower relative decrease in speed during the 15 sprints.

We investigated the effects of short duration running training on resting and exercise lung function in healthy prepubescent children. One trained group (TrG) (n = 9; three girls and six boys; age = 9.7 +/- 0.9 year) participated in 8 weeks of high-intensity intermittent running training and was compared to a control group (ContG) (n = 9; four girls and five boys; age = 10.3 +/- 0.7 year). Before and after the 8-week period, the children performed pulmonary function tests and an incremental exercise test on a cycle ergometer. After the 8-week period, no change was found in pulmonary function in ContG. Conversely, an increase in forced vital capacity (FVC) (+7 +/- 4% ; P = 0.026), forced expiratory volume in one second (+11 +/- 6% ; P = 0.025), peak expiratory flows (+17 +/- 4% ; P = 0.005), maximal expiratory flows at 50% (+16 +/- 10% ; P = 0.019) and 75% (+15 +/- 8% ; P = 0.006) of FVC were reported in TrG. At peak exercise, TrG displayed higher values of peak oxygen consumption (+15 +/- 4% ; P < 0.001), minute ventilation (+16 +/- 5% ; P = 0.033) and tidal volume (+15 +/- 5% ; P = 0.019) after training. At sub-maximal exercise, ventilatory response to exercise DeltaV(E)/DeltaV(CO(2)) was lower (P = 0.017) in TrG after training, associated with reduced end-tidal partial oxygen pressure (P < 0.05) and higher end-tidal partial carbon dioxide pressure (P = 0.026). Lower deadspace volume relative to tidal volume was found at each stage of exercise in TrG after training (P < 0.05). Eight weeks of high-intensity intermittent running training enhanced resting pulmonary function and led to deeper exercise ventilation reflecting a better effectiveness in prepubescent children.

The aim of this study was to analyze the effects of a 7-week interval-training program on different aspects of physical fitness in children who were 8-11 years old. Forty-six boys and 54 girls (9.7 +/- 0.8 years) were divided into an experimental group and a control group. The 2 groups performed selected tests from the European physical fitness test battery before and after training. Training consisted of 2 specific 30-minute sessions per week of short high-intensity, intermittent-running aerobic exercises at velocities ranging from 100-130% of maximal aerobic speed. After training, the experimental group demonstrated a significant improvement in the standing broad jump (9.6%, p < 0.001, F = 12.9) and 20-meter shuttle run (5.4%, p < 0.001, F = 14.4), whereas for the control group, no significant changes were observed. It was concluded that a high-intensity, intermittent-running program improved children's aerobic performance and explosive strength.

In comparison to continuous aerobic type activity, little is known about high-intensity intermittent physical activity in children. Repeated short-term high-intensity activities (> maximal aerobic speed and <10 s) are more characteristic of the spontaneous physical activity of children. Recent studies have shown during repetitive bouts of sprints separated by short recovery intervals, that prepubescent children compared with adults are more able to maintain their performance without substantial fatigue. Moreover, repetitive runs at high velocities (near and higher than the maximal aerobic speed) separated by short recovery periods may elicit a high oxygen consumption in children. Several studies using interval training programmes for 7 weeks, twice a week for 30 min in physical education lessons showed that children's aerobic performance (maximal O2 uptake, maximal aerobic speed) could be enhanced. Training based on these repeated short-term high-intensity exercises could also improve children's anaerobic performance (short-term muscle power, strength and speed). Current evidence suggests that recovery from high-intensity exercises is faster in children than in adults and that repeated runs at high velocities separated by short recovery intervals can improve both aerobic and anaerobic performance. Although continuous aerobic type activity is more scientifically established as a training mode, repeated short-term high-intensity exercises in physical education programmes should be considered to enhance aerobic, as well as, anaerobic fitness in children.

The effects of in-season, high-intensity interval training on professional male soccer players' running performances were investigated. Twenty-two subjects participated in 2 consecutive training periods of 10 weeks. The first period was considered a control period and was compared with a period where 2 high-intensity interval training exercises were included in the usual training program. Intermittent runs consisted of 12-15 runs lasting 15 seconds at 120% of maximal aerobic speed alternated with 15 seconds of rest. Sprint repetitions consisted of 12-15 all-out 40-m runs alternated with 30 seconds of rest. Results from the high-intensity interval training have shown that maximal aerobic speed was improved (+8.1 +/- 3.1%; p < 0.001) and that the time of the 40-m sprint was decreased (-3.5 +/- 1.5%; p < 0.001), whereas no change in either parameters were observed during the control period. This study shows that improvements in physical qualities can be made during the in-season period.

Exercise-induced arterial hypoxemia (EIAH) is a recognized phenomenon in highly trained adults. Like adult athletes, prepubescent trained children may develop high-level metabolic demand but with a limited lung capacity in comparison with adults. The purpose of this investigation was to search for evidence of EIAH in prepubescent trained children. Twenty-four prepubescent (age: 10.3 +/- 0.2 y) trained children (10.0 +/- 0.7 h of weekly physical activity) performed pulmonary function tests and a graded maximal exercise test on a cycle ergometer. EIAH was defined as a drop of at least 4% from resting level arterial oxygen saturation (Sao(2)) measured by pulse oximetry. EIAH was observed in seven children. Forced vital capacity (FVC), ventilatory response to exercise (Delta(E)/Deltaco(2)), and breathing reserve at maximal exercise were significantly lower, whereas tidal volume relative to FVC was higher in hypoxemic children than in nonhypoxemic children; weekly physical activity and maximal oxygen uptake were similar. Moreover, positive relationships were found between Sao(2) at maximal exercise and breathing reserve (r = 0.56; p < 0.05) or volume relative to FVC (r = 0.70; p < 0.01). EIAH may occur in prepubescent trained children with a relatively low maximal oxygen uptake (42 mL. min(-1). kg(-1)); however, the mechanisms remain unclear and need to be investigated more accurately.

The aim of this study was to evaluate the effect of a 15% increase in preferred pedal rate (PPR) on both time to exhaustion and pulmonary O(2) uptake (VO(2)) response during heavy exercise. Seven competitive cyclists underwent two constant-power tests (CPT) at a power output that theoretically requires 50% of the difference in VO(2) between the second ventilatory threshold and VO(2)max (Pdelta50). Each cyclist cycled a CPT at PPR (CPTPPR) and a CPT at +15% of PPR (CPT+15%) in a randomized order. The average PPR value was 94 +/- 4 rpm, and time to exhaustion was significantly longer in CPTPPR compared with CPT+15% (465 +/- 139 vs. 303+/- 42 s, respectively; p = 0.01). A significant decrease in VO(2) values in the first minutes of exercise and a significant increase in VO(2) slow component was reported in CPT+15% compared with CPT(PPR). These data indicate that the increase of 15% PPR was associated with a decrease in exercise tolerance and a specific VO(2) response, presumably due to an increase of negative muscular work, internal work, and an altering of motor unit recruitment patterns.

The purpose of this study was to compare the effects of recovery type (active vs. passive) on the time spent at VO(2)max and above 90 % of VO(2)max during short intermittent runs (15 s) at 120 % of maximal aerobic speed. Twelve male subjects performed a graded test and intermittent runs (15 s) alternated with 15 s of active recovery (50 % of maximal aerobic speed) or with 15 s of passive recovery to exhaustion. The time to exhaustion during the intermittent runs with active recovery (445 +/- 79 s) was significantly shorter (p < 0.001) compared with passive recovery (745 +/- 171 s). No significant difference was found between time spent at VO(2)max and above 90 % of VO(2)max for intermittent runs alternated with active recovery (180 +/- 121 s and 282 +/- 117 s, respectively ) and intermittent runs alternated with passive recovery (191 +/- 135 s and 317 +/- 132 s, respectively ). The times spent at VO(2)max (p < 0.05) and above 90 % of VO(2)max (p < 0.001), expressed in percentage of time to exhaustion, were significantly longer for intermittent runs alternated with active recovery (41 +/- 27 % and 64 +/- 24 %, respectively) than with passive recovery (25 +/- 16 % and 43 +/- 16%, respectively). In conclusion, the present study has shown that the time to exhaustion during repeated high-intensity exercise was significantly greater for passive compared with active recovery, despite no difference in absolute time spent at a high percentage of VO(2)max. However, the time spent at a high percentage of VO(2)max, expressed as a percentage of time to exhaustion, was significantly higher for active compared with passive recovery.

The aim of this study was to investigate the development of exercise-induced hypoxemia (EIH defined as an exercise decrease > 4 % in oxygen arterial saturation, i. e. SaO (2) measured with a portable pulse oximeter) in twelve sportsmen and ten sportswomen (18.5 +/- 0.5 years) who were non-elite and not initially engaged in endurance sport or training. They followed a high-intensity interval-training program to improve V.O (2)max for eight weeks. The training running speeds were set at approximately 140 % V.O (2)max running speed up to 100 % 20-m maximal running speed. Pre- and post-training pulmonary gas exchanges and SaO (2) were measured during an incremental running field-test. After the training period, men and women increased their V.O (2)max (p < 0.001) by 10.0 % and 7.8 %, respectively. Nine subjects (seven men and two women) developed EIH. This phenomenon appeared even in sportsmen with low V.O (2)max from 45 ml x min (-1) x kg (-1) and seemed to be associated with inadequate hyperventilation induced by training: because only this hypoxemic group showed 1) a decrease in maximal ventilatory equivalent in O (2) (V.E/V.O (2), p < 0.01) although maximal ventilation increased (p < 0.01) with training, i. e. in EIH-subjects the ventilatory response increased less than the metabolic demand after the training program; 2) a significant relationship between SaO (2) at maximal workload and the matched V.E/V.O (2) (p < 0.05, r = 0.67) which strengthened a relative hypoventilation implication in EIH. In conclusion, in this field investigation the significant decrease in the minimum SaO (2) inducing the development of EIH after high-intensity interval-training indicates that changes in training conditions could be accompanied in approximately 40 % non-endurance sportive subjects by alterations in the degree of arterial oxyhemoglobin desaturation developing during exercise.

The purpose of this study was to compare the effects of active vs. passive recovery on the time to exhaustion for intermittent runs (15 s) at supramaximal velocity (120% of maximal aerobic speed). Twelve male subjects performed a graded test, an intermittent run to exhaustion with active recovery (50% of maximal aerobic speed) and an intermittent run to exhaustion with passive recovery. Results showed that intermittent runs to exhaustion with passive recovery [745 (171) s] allowed subjects to run for a significantly longer (p<0.001) time than intermittent runs to exhaustion with active recovery [445 (79) s]. These results could be explained by a significantly higher (p<0.001) energy requirement for intermittent runs with active recovery [59.9 (9.6) ml.kg(-1).min(-1)] than for intermittent runs with passive recovery [48.9 (6.9) ml.kg(-1).min(-1)]. It could be also hypothesized that the energy required to run during short active recovery would result in less oxygen being available to reload myoglobin and haemoglobin, to remove lactate concentrations and to resynthesize the phosphocreatine. Consequently, for intermittent runs with short recovery periods, passive recovery will induce a longer time to exhaustion than active recovery.

This study was designed to calculate the critical velocity (vcrit) and anaerobic distance capacity (ADC) of prepubescent children for running events. Thirty-four prepubertal children underwent a graded field test to exhaustion in order to determine peak oxygen uptake (peak VO2) and maximal aerobic velocity (MAV). Then, in random order, they performed five runs to exhaustion (tlim) at relative velocities corresponding to 90, 95, 100, 105, and 110% of MAV. The linear relationships between distance limit (dlim) and tlim were calculated in order to determine vcrit (slope of the relationship) and ADC (intercept). Very high individual coefficients of determination were found between dlim and tlim (0.98 < r2 < 0.99; p < 0.001). The vcrit was significantly correlated with peak VO2 (r = 0.73; p < 0.001). However, no relationship was found between ADC and the maximal accumulated oxygen deficit. In conclusion, our results indicated that, for children, the relationship between dlim and tlim could be calculated with tlim ranging from 2 to 10 min, and that vcrit is a good indicator of the aerobic fitness of children. Nevertheless, further studies will have to be conducted to validate the use of ADC as an indicator of children's anaerobic capacity.

Training-induced adaptations in aerobic fitness have been extensively studied in adults, and some exercise scientists have recommended similar training programmes for young people. However, the subject of the response to aerobic training of children and adolescents is controversial. The effects of exercise training on prepubertal children are particularly debatable. The latter may be partly explained by different training designs, which make comparisons between studies very problematic. We have analysed the procedures applied to protocol design and training methods to highlight the real impact of aerobic training on the peak oxygen uptake (V-dotO2) of healthy children and adolescents. In accordance with previously published reviews on trainability in youngsters, research papers were rejected from the final analysis according to criteria such as the lack of a control group, an unclear training protocol, inappropriate statistical procedures, small sample size, studies with trained or special populations, or with no peak V-dotO2 data. Factors such as maturity, group constitution, consistency between training and testing procedures, drop out rates, or attendance were considered, and possible associations with changes in peak V-dotO2 with training are discussed. From 51 studies reviewed, 22 were finally retained. In most of the studies, there was a considerable lack of research regarding circumpubertal individuals in general, and particularly in girls. The results suggest that methodologically listed parameters will exert a potential influence on the magnitude of peak V-dotO2 improvement. Even if little difference is reported for each parameter, it is suggested that the sum of errors will result in a significant bias in the assessment of training effects. The characteristics of each training protocol were also analysed to establish their respective potential influence on peak V-dotO2 changes. In general, aerobic training leads to a mean improvement of 5-6% in the peak V-dotO2 of children or adolescents. When only studies that reported significant training effect were taken into account, the mean improvement in peak V-dotO2 rose to 8-10%. Results suggested that intensities higher than 80% of maximal heart rate are necessary to expect a significant improvement in peak V-dotO2. There is clearly a need for longitudinal or cross-sectional studies that investigate the relationship between maturity and training with carefully monitored programmes. Further research is also needed to compare interval training and continuous training.

The purpose of this study was to determine the effects of intensified physical education sessions on adolescents ages 11-16 years. They were divided into two experimental groups--high-intensity running group (HIRG) and high-intensity jumping group (HlJG)--and a control group (C). During the sessions, heart rate (HR) was monitored. There was no significant difference between mean HR for HIRG and HIJG, while the mean HR was significantly lower for C (p < .001). For both HIRG and HIJG, the mean HR was significantly higher for girls than for boys (p < .001). Our results suggested that these intensified physical education lessons require a high percentage of maximal HR in adolescents and can be used to improve aerobic fitness.

Background: To compare plasma lactate concentrations and plasma lactate kinetics during recovery, for measured and corrected values for changes in plasma volume, after a maximal aerobic exercise., Methods: Sixteen male subjects performed an incremental and maximal exercise in order to reach maximal aerobic power. Prior to the exercise, at the end and during recovery (2, 5, 12 and 30 min), blood samples were collected through an antecubital catheter. Samples were analysed for lactate, hematocrit and hemoglobin in order to calculate changes in plasma volume. Plasma lactate concentrations ([La]p) were corrected for changes in plasma volume. Plasma lactate kinetics was estimated through the ratio between [La]p after 5 min recovery minus [La]p after 30 min to time (25 min) and expressed in percentage per minute., Results: Maximal changes in plasma volume (-19.7 +/- 3.8%) were correlated to maximal measured [La]p (r=0.66, p<0.01). Maximal measured [La]p values (14.9 +/- 2.6 mmol x l-1) were 17.3% higher (p<0.001) than corrected values (12.7 +/-2.0 mmol x l-1). The kinetics of [La]p decrease was significantly higher (p<0.001) for measured values (2.38 +/- 0.29 % x min-1) than for corrected values (2.22 +/- 0.33 % x min-1)., Conclusions: These results suggested that changes in plasma volume must be taken into account when peak postexercise plasma lactate concentration or lactate recovery curves are analysed.

The relations among kinematic parameters measured during the first 10 seconds of 100-m sprint and anaerobic tests were studied in 22 male physical education students. During the first 10 seconds of the sprint, the position of the runners was "continuously" measured with a laser telemeter. Maximal acceleration (Amax), maximal velocity (Vmax), and time to reach Vmax (tVmax) were derived from position data. In addition, the subjects performed anaerobic tests: squat jump (SJ), countermovement jump (CMJ), and force-velocity test to measure maximal power, maximal theoretical cranking velocity (VO), maximal theoretical isometric force, and the Wingate anaerobic test (30 seconds). The mean 100-m run time of the subjects was 12.6 +/- 0.9 seconds. The highest correlations were calculated between Amax and V0 (r = 0.55, p < 0.01) and CMJ (r = 0.48, p < 0.05) and Vmax and SJ (r = 0.63, p < 0.01) and CMJ (r = 0.56, p < 0.05). The tVmax was uncorrelated to other tests. Because the CMJ was the anaerobic performance best correlated to the different kinematic parameters of the run, our results fail to identify one anaerobic test that specifically explains one sprint kinematic parameter.

Purpose: Muscle power is a component of muscular fitness and is proportional to its volume. Reduced muscular fitness in children is linked to negative health outcomes. Associations between muscle volume (MV) and power have not been examined in young children and could reveal important insights into early neuromuscular development. Method: Forty-four children (2-8 y) completed 3 tests of short-term muscular power: repeated anaerobic sprint test, vertical jump, and horizontal jump. MV was assessed using 3D ultrasound for 3 lower limb muscles (rectus femoris, medial gastrocnemius, and tibialis anterior) and summed for across legs. Associations between muscular power and summed MV were assessed using Pearson correlation (r). Sex-based differences in muscular power and MV were assessed using 1-way analysis of covariance. Results: Moderate-strong associations (r =.57 - .87) were found between muscular power and summed MV. No differences were found between boys and girls for height, weight, MV, or muscular power. Conclusions: Young children who have larger lower limb muscles perform better at tasks dependent on short-term muscular power, such as running and jumping, compared with children with smaller muscles. Sex-based differences in short-term muscular power do not exist in young children and reflect similar anthropometry, including lower limb MV. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to examine the responsiveness of commonly used measurement instruments to a short training camp by examining the time course of psychophysiological responses in high-level youth soccer players. Methods: Monitoring was carried out in 14 U15 male soccer players of 1 professional youth academy. Players provided data 3 days prior to (D − 3), during (D2−D4), and 1 (D + 1) and 4 days (D + 4) after the camp: 4 items for the Short Recovery and Stress Scale (SRSS), a countermovement jump (CMJ), and a submaximal run to assess exercise heart rate and heart-rate recovery. Training load during the camp followed an alternating low–high pattern, with lower training loads on D1 and D3 and higher training loads on D2 and D4. Results: Changes in SRSS physical performance capability, emotional balance, overall recovery, muscular stress, and overall stress were small to moderate on D3 and moderate to large on D + 1, while changes were trivial on D + 4. Some CMJ parameters related to the eccentric phase were slightly improved on D3, and these parameters were slightly impaired on D4. Changes in CMJ parameters were trivial on D + 1 and D + 4. After a moderate decrease in exercise heart rate on D3, there was a small decrease on D + 4 and a moderate increase in heart-rate recovery. Conclusion: Measurement instruments such as the SRSS and submaximal runs can be used to monitor acute psychophysiological responses to load, while the CMJ may provide little insight during periods of intensified training load. [ABSTRACT FROM AUTHOR]

Purpose: To compare the effects of 2 small-sided games (SSGs), shuttle running within the bout (SSG-S) versus possession play only (SSG-P) on acute physiological and metabolic responses, perception of effort, and performance. Methods: Ten young elite male soccer players (age 18.6 [1.9] y) performed two 5vs5 SSG formats (SSG-S and SSG-P) consisting of 4 × 4 minutes with 1 minute of passive recovery between bouts, 2 times each, once a week, and in a randomized order. Heart rate, blood lactate concentration, and rating of perceived exertion were assessed as indices of internal workload. Total and relative distances, distance at moderate and high speed, distances traveled in accelerations (≥2 m·s−2) and decelerations (≤−2 m·s−2; DDEC), and average metabolic power were chosen as indices of external workload and collected with a 10-Hz portable global positioning system device. Results: Total distance, distances traveled in acceleration, distances traveled in deceleration, average metabolic power (always P <.01 and g > 1.62—large effect), and distance at moderate speed (P =.03 and g = 0.84—large effect) were significantly higher in SSG-S than in SSG-P. Moreover, the SSG-S showed higher blood lactate concentration (P =.0001, g = 12.58—large effect) and rating of perceived exertion (P =.03, g = 1.14—large effect) values than SSG-P. No significant differences in peak heart rate, relative distance, and distance at high speed were found. Conclusions: Our study showed, in young competitive male soccer players, the effectiveness of an SSG format that includes shuttle running within each bout in the development of more relevant internal and external workloads. These experimental data should encourage coaches to use this new SSG regimen within the traditional weekly training program. [ABSTRACT FROM AUTHOR]

Purpose: To examine the general perspectives of elite soccer players on the time course of perceived postmatch fatigue and the influence of away matches on subjective perceptions. Methods: Adopting a cross-sectional study design, we invited 371 subjects from 14 top-division European clubs competing in the Belgian First Division A, English Premier League, French Ligue 1, Italian Serie A, Portuguese Primeira Liga, Russian Premier League, and Swiss Premier League to take part in a short survey on general issues relating to postmatch fatigue measurement and tracking in professional soccer. Results: Three hundred male professional soccer players completed the short questionnaire. For perceptions relevant to the time course of postmatch fatigue, two-thirds of respondents (67%) indicated higher postmatch fatigue perceived 2 days (48 h) after an official competition. Among these respondents, a higher proportion of answers was observed in wide midfielders (74%), attackers (74%), and central midfielders (68%). Approximately two-thirds of respondents (63%) indicated more than usual and much more than usual perceived postmatch fatigue following away matches. Conclusions: For the first time, our investigation addressed practical aspects that remained unexplored and fundamental to the definition of an optimal player management process following a competition. From a practical standpoint, perspectives of individual elite soccer players substantiated the notion of implementing processes with dedicated recovery protocols within 48 hours postmatch and highlighted the need for differential strategies addressing the additional burden of away matches and travel. [ABSTRACT FROM AUTHOR]

Background: We aim to systematically review the literature on measurement properties of self- and proxy-reported questionnaires measuring 24-hour movement behaviors in children and adolescents. Methods: PubMed, PsycINFO, SPORTDiscus, and EMBASE were searched until June 2021. Studies were included if the sample size for validity studies had 50 participants (minimum) and included, at least, both validity and test–retest reliability results of questionnaires. The review followed an adaptation of the Consensus-based Standards for the selection of health Measurement INstruments guidelines, to evaluate the quality of measurements properties of the questionnaires (content, convergent and criterion validity, reliability, measurement error, and responsiveness), as well as the risk of bias of each measurement property. Results: This review included 29 studies, describing 37 questionnaires. Sixty-eight percent showed "adequate" content validity. None of the questionnaires showed overall "adequate" criterion validity, and the risk of bias was "very low" for 92%. One questionnaire showed "adequate" convergent validity, and 73% of the studies were classified with a "high risk of bias." Seven questionnaires showed "adequate" reliability, and 27.3% of the studies were rated with a "very low risk of bias." None of the questionnaires showed "adequate" criterion validity and reliability, simultaneously. Conclusions: Existing questionnaires have insufficient measurement properties, and none considered the 24-hour movement behavior paradigm. These results highlight the need for better questionnaires of movement behavior combinations, to improve the monitoring and surveillance systems of 24-hour movement behaviors in this population. [ABSTRACT FROM AUTHOR]

Because physical demands are surging in football (soccer, USA), clubs are more and more seeking players who have a high capacity to perform repeated intense exercise. High-intensity interval training (HIIT), comprising exercise performed at intensities near or exceeding the capacity of aerobic energy systems, effectively enhances the physical conditioning of players. But given that HIIT imposes high loads, it increases the risk of overload-associated match performance decline and injury. This makes some coaches inclined to conduct HIIT in the weeks leading up to the season and during the season. Therefore, the challenge is how to optimize and dose HIIT during these phases, as they can be decisive. Studies have highlighted the utility of conducting periods of intensified training to overcome the risk of overload while at the same time enhancing performance. During intensified training periods of typically a few weeks, intensity is increased by enlarging the amount of HIIT, for example, aerobic high-intensity training or speed endurance training, while volume at low-to-moderate intensity is significantly reduced. The outcome depends on training composition and prescription-most notably, intensity and duration of bouts and recovery. When work intervals are prescribed for a few minutes at intensities > 90% heart rate max (i.e., aerobic high-intensity training), then beneficial adaptations pertaining to aerobic power and capacity are apparent. But when work intervals are conducted at much higher intensities, as all-out efforts or sprinting of typically 10- to 40-s duration with longer recovery periods (i.e., speed endurance training), beneficial adaptations pertaining to anaerobic energy systems, ion handling, and fatigue resilience are commonly observed. In this review, we discuss the utility of conducting intensified training periods to enhance performance in elite football players during the late preparation phase and competitive season., (© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

The purpose of this study was to characterise the relationship between running velocity and the time for which a subject can run at maximal oxygen uptake (VO2max), (tlimVO2max). Seven physical education students ran in an incremental test (3-min stages) to determine VO2max and the minimal velocity at which it was elicited (vVO2max). They then performed four all-out running tests on a 200-m indoor track every 2 days in random order. The mean times to exhaustion tlim at 90%, 100%, 120% and 140% vVO2max were 13 min 22 s (SD 4 min 30 s), 5 min 47 s (SD 1 min 50 s), 2 min 11 s (SD 38 s) and 1 min 12 s (SD 18 s), respectively. Five subjects did not reach VO2max in the 90% vVO2max test. All the subjects reached VO2max in the runs at 100% vVO2max. All the subjects, except one, reached VO2max in the runs at 120% vVO2max. Four subjects did not reach VO2max in the 140% vVO2max test. Time to achieve VO2max was always about 50% of the time to exhaustion irrespective of the intensity. The time to exhaustion-velocity relationship was better fitted by a 3- than by a 2-parameter critical power model for running at 90%, 100%, 120%, 140% vVO2max as determined in the previous incremental test. In conclusion, tlimVO2max depended on a balance between the time to attain VO2max and the time to exhaustion tlim. The time to reach VO2max decreased as velocity increased. The tlimVO2max was a bi-phasic function of velocity, with a peak at 100% vVO2max.

The so-called velocity associated with V˙O2max, defined as the minimal velocity which elicits V˙O2max in an incremental exercise protocol ( v V˙ O2max), is currently used for training to improve V˙O2max. However, it is well known that it is not the sole velocity which elicits V˙O2max and it is possible to achieve V˙O2max at velocities lower and higher than v V˙ O2max. The goal of this study was to determine the velocity which allows exercise to be maintained the longest time at V˙O2max. Using the relationship between time to exhaustion at V˙O2max in the all-out runs at 90%, 100%, 120% and 140% of v V˙ O2max and distance run at V˙O2max, the velocity which elicits the longest time to exhaustion at V˙O2max (CV′) was determined. For the six subjects tested (physical education students), this velocity was not significantly different from v V˙ O2max (16.96 ± 0.92 km · h−1 vs 17.22 ± 1.12 km · h−1, P = 0.2 for CV′ and v V˙ O2max, respectively) and these two velocities were correlated ( r = 0.88, P = 0.05). [ABSTRACT FROM AUTHOR]

Background: The purpose of the study was to test the ability to determine the velocity associated with peak oxygen uptake for adolescents by means of a simple field test, the Université de Montréal Track Test (UMTT)., Methods: Fifteen adolescents, 13.4 +/- 1.0 years, performed two maximal field tests where oxygen uptake and heart rate were continuously monitored. The first test (graded field test, first stage 8 km.h-1, increment 1.5 km.h-1, duration 3 min) allowed the subjects to reach a steady-state oxygen uptake. Then, the velocity associated with peak oxygen uptake was calculated from the ratio between peak oxygen uptake above resting level to energy cost of running. The calculated velocity was kept as the criterion velocity. For the second test (UMTT, first stage 8 km.h-1; increment 1 km.h-1; duration 2 min), the velocity measured at the last completed stage was retained., Results: The measured peak oxygen uptake for the graded field test (51.8 +/- 6.5 ml.kg-1.min-1) and for the UMTT (51.0 +/- 7.9 ml.kg-1.min-1) were not significantly different. The calculated velocity (12.9 +/- 1.0 km.h-1) and the measured velocity (12.7 +/- 0.9 km.h-1) were not significantly different and were significantly correlated (r = 0.80, p < 0.001)., Conclusions: It was concluded that, for adolescents, the velocity measured at the last completed stage of the UMTT allows a valid estimation of the velocity associated with peak oxygen uptake.