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Purpose: To gain knowledge on the beliefs and practices of football practitioners applying high-speed and sprint running exposure programming strategies. Methods: One hundred two football practitioners from 22 different countries participated in a study consisting of a survey including 5 domains: demographic and professional characteristics (Who); importance of high-speed and sprint running exposure for physical-capability development, preparation for competition, and injury-prevention strategies (Why); exposure timing (When); methodological procedures for exposure monitoring and training scheduling (What); and effectiveness of common training practices (How). Data were analyzed using a combination of descriptive statistics, generalized mixed effects, and multinomial logistic regression models. Results: Data revealed 5 main findings: (1) overall agreement on the importance of exposure for physical-capability development, preparation for competition, and injury-prevention strategies; (2) different exposure timing and selective training scheduling for starting and nonstarting players across typical and congested weeks; (3) lack of consensus on the conceptual constructs defining high-speed and sprint running metrics and the methodological procedures used for monitoring; (4) a probable association between match-related outcomes and exposure strategies used in training; and (5) a broad range of training methods considered effective to elicit exposure. Conclusions: This study provides actionable insights into the planning, implementing, and monitoring strategies for high-speed and sprint running exposure in football. While some conform with the evidence on high-speed and sprint running training in football, further research and professional debate are warranted to develop empirical knowledge and provide pragmatic recommendations to help practitioners in adopting evidence-informed decisions.

Purpose: This study examined the interday reliability of a predetermined and a self-determined isometric-squat test among youth soccer players. Familiarization effects were evaluated to determine the minimum number of trials necessary to obtain consistent outputs. Finally, differences between protocols were evaluated. Methods: Thirty-one youth soccer players (mean [SD] age: 13.2 [1.0] y; body mass: 54.1 [3.4] kg; stature: 166.3 [11.2] cm; percentage of estimated adult height: 92.6% [3.6%]) from a top-tier professional academy completed 4 experimental sessions for each protocol: familiarization 1, familiarization 2, test, and retest sessions. Peak force; relative peak force; impulse from 0 to 50 milliseconds, 0 to 100 milliseconds, 0 to 150 milliseconds, and 0 to 200 milliseconds; and rate of force development from 0 to 50 milliseconds, 0 to 100 milliseconds, 0 to 150 milliseconds, and 0 to 200 milliseconds were measured. Results: Both protocols displayed acceptable (intraclass correlation coefficient ≥.75 and coefficient of variation ≤10%) reliability statistics for all metrics apart from rate of force development of any time epoch. Differences were found between familiarization 2 and both test and retest sessions for peak force (P = .034 and .021, respectively) and relative peak force (P = .035 and .005, respectively) across both protocols. Conclusions: The isometric-squat test is a reliable test among youth soccer players. Two familiarization sessions seem to be sufficient to ensure data stabilization. Outputs between the self-determined and predetermined are comparable; however, the latter seems preferable due to improved testing time efficiency.

Background Sided games (i.e., small sided, medium sided, large sided) involve tactical, technical, physical, and psychological elements and are commonly implemented in soccer training. Although soccer sided-games research is plentiful, a meta-analytical synthesis of external load exposure during sided games is lacking. Objective The objective of this systematic review and meta-analysis was to: (1) synthesize the evidence on high-speed and sprint running exposure induced by sided games in adult soccer players, (2) establish pooled estimates and intra-individual reliability for high-speed and sprint running exposure, and (3) explore the moderating effects of game format and playing constraints. Methods A literature search was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 guidelines. Four databases (PubMed/MEDLINE, Scopus, SPORTDiscus, Web of Science Core Collection) were systematically searched up to 25 January, 2022. Eligibility criteria were adult soccer players (population); training programs incorporating sided games (intervention); game manipulations including number of players, pitch dimension, and game orientation (comparator); and high-speed, very high-speed, and sprint relative (m$$\cdot$$ · min−1) running distances and associated intra-individual reliability (outcome). Eligible study risk of bias was evaluated using RoBANS. Pooled estimates for high-speed and sprint running exposure, and their intra-individual reliability, along with the moderating effect of tracking device running velocity thresholds, pitch dimension (i.e., area per player), and game orientation (i.e. score or possession), were determined via a multi-level mixed-effects meta-analysis. Estimate uncertainty is presented as 95% compatibility intervals (CIs) with the likely range of relative distances in similar future studies determined via 95% prediction intervals. Results A total of 104 and 7 studies met our eligibility criteria for the main and reliability analyses, respectively. The range of relative distances covered across small-sided games, medium-sided games, and large-sided games was 14.8 m$$\cdot$$ · min−1 (95% CI 12.3–17.4) to 17.2 m$$\cdot$$ · min−1 (95% CI 13.5–20.8) for high-speed running, 2.7 m$$\cdot$$ · min−1 (95% CI 1.8–3.5) to 3.6 m$$\cdot$$ · min−1 (95% CI 2.3–4.8) for very high-speed running, and 0.2 m$$\cdot$$ · min−1 (95% CI 0.1–0.4) to 0.7 m$$\cdot$$ · min−1 (95% CI 0.5–0.9) for sprinting. Across different game formats, 95% prediction intervals showed future exposure for high-speed, very high-speed running, and sprinting to be 0–46.5 m$$\cdot$$ · min−1, 0–14.2 m$$\cdot$$ · min−1, and 0–2.6 m$$\cdot$$ · min−1, respectively. High-speed, very high-speed running, and sprinting showed poor reliability with a pooled coefficient of variation of 22.8% with distances being moderated by device speed thresholds, pitch dimension, and game orientation. Conclusions This review is the first to provide a detailed synthesis of exposure and intra-individual reliability of high-speed and sprint running during soccer sided games. Our estimates, along with the moderating influence of common programming variables such as velocity thresholds, area per player, and game orientation should be considered for informed planning of small-sided games, medium-sided games, and large-sided games soccer training. Clinical Trial Registration Open Science Framework available through https://osf.io/a4xr2/.

The aim of this study was to compare internal and external load profiles of different game profile-based training (GPBT) formats among elite young football players. Twenty-one participants (age: 18.7 ± 0.6 years) performed three sessions of three GPBT formats, which were matched for training volume but structured with different high-speed running and sprint demands: i) performed along linear paths (GPBT-L); ii) performed as repetitive actions of short distance including many multi-directional changes of direction (GPBT-S) and, iii) a combination of the other two protocols, that is linear high-speed runs and sprint efforts with a single change of direction (GPBT-M). External load outputs were collected using GPS units, physiological and perceptual responses were monitored with heart rate (HR) monitors, and ratings of perceived exertion (RPE), respectively. While no differences were found between formats for HR and RPE, distinct external load profiles were observed for high-speed running (HSD) and sprint distances (SD), (GPBT-LGPBT-MGBPT-S, all p0.05), and high-intensity acceleration and deceleration efforts (HIE), (GPBT-SGPBT-MGPBT-L, all p0.05). Moreover, the GPBT-S format was characterized by greater intra-session variability for HSD, SD, and HIE (CV% = 24.2%, 16.5% and 20.4%, respectively) and inter-session variability for HSD and SD (CV% = 10% and 15.7%, respectively) compared to the other two formats. Considering their load profiles and the associated reliability scores, football practitioners can implement GPBT formats interchangeably to elicit necessary internal load responses and selectively to prioritize specific external load outputs.

We quantified on pitch external loading of English Premier League (EPL) academy soccer players (n=76; U12-U18 age groups) over an entire competitive season. Mean accumulative weekly duration and total distance, respectively, was similar in the U12 (329±29 min; 19.9±2.2 km), U13 (323±29 min; 20.0±2.0 km) and U14 (339±25 min; 21.7±2.0 km; P>0.05 for all comparisons) age-groups, though all teams were less than U15 (421±15 min; 26.2±2.1 km), U16 (427±20 min; 25.9±2.5 km) and U18 (398±30 min; 26.1±2.6 km) players (P0.05 for all pairwise comparisons) though all squads were less than U15 (657±242 m and 49±98 m), U16 (749±152 m and 95±55 m) and U18 (979±254 m and 123±56 m) age-groups (P

Purpose This study explored the validity and reliability of the physiological and perceptual responses elicited during a novel treadmill-based Soccer Referee Simulation (SRS). Methods Following the collection of baseline measures and habituation procedures, eight sub-elite soccer referees completed a single trial of the SRS whereby measures of heart rate (HR), oxygen uptake (V̇O2), blood lactate concentrations ([La−]b), and differential ratings of perceived exertion (RPE) were obtained. Referees’ HR responses were also monitored during a series of competitive matches (5 match observations per referee). For the reliability aspect of the investigation, eight well-trained males with soccer playing experience and a comparable physiological profile were initially habituated, and thereafter completed three separate trials of the SRS during which the reliability of the selected outcome variables were ascertained. Trials were separated by 3–7 days and performed under standardised conditions. Results No differences were evidenced between the SRS and match play in relation to measures of mean HR (P = 0.444; ES = 0.29), peak HR (P = 0.074; ES = 0.74), or HR-based training impulse (P = 0.498; ES = 0.25). Additionally, no systematic differences were detected between reliability trials for any of the measured outcome variables (P ≥ 0.293), whilst good levels of reliability were observed for measures of mean HR (ICC = 0.94; CV = 3.1%), peak HR (ICC = 0.93; CV = 2.2%), HR-based training impulse (ICC = 0.95; CV = 10.0%), mean V̇O2 (ICC = 0.95; CV = 2.6%); [La−]b (ICC ≥ 0.89; CV ≤ 11.5%), and differential RPE (ICC ≥ 0.94; CV ≤ 15.1%). Conclusion The SRS represents a valid and reliable protocol that closely replicates the physiological and decision-making demands of soccer refereeing.

The SARS-CoV-2 agent initiated a global pandemic. The initial response to the pandemic was severe disruption to the public and private sector including sports. The resultant was that soccer clubs had to prescribe that the players trained in isolation for a prolonged period of time in an attempt to maintain fitness. The aim of the present study was to evaluate the impact of a 10-week period of training in isolation on aerobic fitness, body composition and injury incidence on the return to preseason team-training in a group of elite, male soccer players.Twenty-two professional soccer players (age: 25.2±4.4 years) who played for an English Championship first team participated in this study. A weekly training program was sent to each player at the start of each week. Prior to the start of the isolated training period, all players underwent a maximal aerobic speed test (MAS), and Body Mass Index data (BMI) were obtained. These measurements were repeated on the return to team training.There was a significant (P0.05) increase in MAS pre-post isolated training (pre: 4.71±0.15 vs. post: 4.92±0.17 m/s), no change in BMI (pre: 24.3±1.3 vs. post: 24.1±1.1 kg/mThe evidence from this study suggests that a more prolonged preseason schedule can enhance aerobic conditioning and mitigate the injury risk on the return to competitive match-play in elite soccer players.

The goal of professional soccer academies is to develop players who can progress and represent their first team or that can be sold for financial gain. As an academy player transitions through the academy pathway (i.e. from under, U9 to U23), they undergo distinct phases of growth and maturation that result in anatomical (e.g. an increase in stature and body mass), physiological (e.g. an increase in growth hormone, insulin-like growth factor 1, testosterone and thyroid hormones) and metabolic changes (e.g. increased glycolytic capabilities). The collective result of such changes are likely to influence such daily energy requirements. However, unlike professional adult players, the body composition, physical loading patterns and associated daily energy expenditure have not yet been quantified in academy soccer players. A detailed understanding of such parameters is fundamental in order to promote growth and maturation whilst also maximising each players physical and technical development. With this in mind, the aim of this thesis was to determine the energy requirements of male academy soccer players from the English Premier League of different chronological and biological ages. The aim of Study 1 (Chapter 4) was to assess body composition and resting metabolic rate in a cohort of academy soccer players. In a cross-sectional design, ninety-nine males from a Category One English Premier League academy (U12-U23 age-groups) underwent assessments of body composition (dual-energy X-ray absorptiometry, DXA) and resting metabolic rate (indirect calorimetry). Fat-free mass increased between the U12 (31.6 ± 4.2 kg) and U16 (56.3 ± 5.3 kg) age-groups after which no further increases occurred. Resting metabolic rate in the U12 (1655 ± 195 kcalday-1), U13 (1720 ± 205 kcalday-1) and U14 (1846 ± 218 kcalday-1) age-groups was significantly lower than the U15 (1957 ± 128 kcalday-1), U16 (2042 ± 155 kcalday-1), U18 (1875 ± 180 kcalday-1) and U23 (1941 ± 197 kcalday-1) age-groups. These data provide the first report of differences in body composition and resting metabolic rate in academy soccer players (as assessed via DXA and indirect calorimetry, respectively) and demonstrate that the growth and maturation occurring between U12-U16 significantly increases resting energy requirements. Having quantified body composition and resting metabolic rate in Study 1 (Chapter 4), the aim of Study 2 (Chapter 5) was to determine the typical weekly training and match loading patterns of academy soccer players. Over the course of an entire competitive season, weekly training and match load was quantified using global positioning system technology in 76 soccer players from a Category One English Premier League academy (U12-U18 age-groups). Weekly training and match volume (i.e. duration and total distance) was similar in the U12 (329 ± 29 min; 19.9 ± 2.2 km), U13 (323 ± 29 min; 20.0 ± 2.0 km) and U14 (339 ± 25 min; 21.7 ± 2.0 km) age-groups, but was lower than the U15 (421 ± 15 min; 26.2 ± 2.1 km), U16 (427 ± 20 min; 25.9 ± 2.5 km) and U18 (398 ± 30 min; 26.1 ± 2.6 km) age-groups. Weekly high-speed running and sprint distance (i.e. intensity) were comparable in the U12 (220 ± 95 m and 6 ± 9 m respectively), U13 (331 ± 212 m and 6 ± 27 m) and U14 (448 ± 193 m and 21 ± 29 m) age-groups was similar, but less than the U15 (657 ± 242 m and 49 ± 98 m), U16 (749 ± 152 m and 95 ± 55 m) and U18 (979 ± 254 m and 123 ± 56 m) age-groups. These data provide the first 4 report to objectively assess accumulative training and match loads in academy soccer players and demonstrate that the absolute loads are progressive in nature throughout the academy pathway. Given the progressive changes in body composition (Study 1, Chapter 4), resting metabolic rate (Study 1, Chapter 4) and physical loading patterns (Study 2, Chapter 5), the aim of Study 3 (Chapter 6) was to quantify the total daily energy expenditure of academy soccer players with different chronological and biological ages. Energy expenditure (doubly labelled water) and energy intake (remote food photographic method) was assessed over a 14-day in-season period in 24 soccer players from a Category One English Premier League academy (U12/13, n=8; U15, n=8; U18, n=8). U18 players presented with greater total energy expenditure (3586 ± 487 kcalday-1) than both the U15 (3029 ± 262 kcalday-1) and U12/13 players (2859 ± 265 kcalday-1), though no differences were evident between the U12/13 and U15 age-groups. Within age-groups, no differences were apparent between energy intake and total energy expenditure, whilst U18 players (3180 ± 279 kcalday-1) reported a higher energy intake than both the U15 (2821 ± 338 kcalday-1) and U12/13 (2659 ± 187 kcalday-1) players. In some individuals (evident in all age-groups) total energy expenditure was greater than that previously observed in adult English Premier League soccer players (3566 ± 585 kcalday-1). In summary, the data presented in this thesis provides the first report to simultaneously quantify body composition, resting metabolic rate, physical loading patterns and total daily energy expenditure of academy soccer players. Importantly, these data demonstrate that players’ absolute daily energy expenditure progressively increase as they become more biologically mature, likely a reflection of increased fat-free mass and physical loading patterns. From a practical perspective, these data will assist in developing population specific sport nutrition guidelines.

Isokinetic strength screening is utilized in professional soccer. However, there has been little research on the interaction between seasonal changes in players' peak torque (PT) and injury incidence. Twenty-five (age 16.5

Female soccer has seen a substantial rise in participation, as well as increased financial support from governing bodies over the last decade. Thus, there is an onus on researchers and medical departments to develop a better understanding of the physical characteristics and demands, and the health and performance needs of female soccer players. In this review, we discuss the current research, as well as the knowledge gaps, of six major topics: physical demands, talent identification, body composition, injury risk and prevention, health and nutrition. Data on female talent identification are scarce, and future studies need to elucidate the influence of relative age and maturation selection across age groups. Regarding the physical demands, more research is needed on the pattern of high-intensity sprinting during matches and the contribution of soccer-specific movements. Injuries are not uncommon in female soccer players, but targeting intrinsically modifiable factors with injury prevention programmes can reduce injury rates. The anthropometric and physical characteristics of female players are heterogeneous and setting specific targets should be discouraged in youth and sub-elite players. Menstrual cycle phase may influence performance and injury risk; however, there are few studies in soccer players. Nutrition plays a critical role in health and performance and ensuring adequate energy intake remains a priority. Despite recent progress, there is considerably less research in female than male soccer players. Many gaps in our understanding of how best to develop and manage the health and performance of female soccer players remain.

This study sought to: (1) document the multifaceted training practices of soccer officials in relation to their role and officiating category; and (2) explore the association between the officials’ training practices and perceptions of the attributes pertinent to optimal performance. Field referees and assistant referees at officiating categories 1–3 ( n = 173) with the Scottish Football Association were invited to participate in this national cross-sectional study. Using the Referee Training Activity Questionnaire (RTAQ), officials reported the volume and type of training engaged in during a 2-week in-season period. Respondents’ perceptions of the skills pertinent to performance were also explored using a 7-point Likert scale ( 1 = not at all important; 7 = extremely important), with the frequency in which they trained these skills assessed using a 5-point Likert Scale ( 1 = less than once a month; 5 = more than once a week). Ninety-one responses were received, representing a 52.6% response rate. Irrespective of their role or level of professional attainment, the officials’ training was focused mostly on physical conditioning, with significantly less time apportioned to decision-making ( P

Cardiac modifications to training are a product of the genetic pre-disposition for adaptation and the repetitive haemodynamic loads that are placed on the myocardium. Elite pre-adolescent athletes are exposed to high-intensity training at a young age with little understanding of the physiological and clinical consequences. It is unclear how right ventricular (RV) structure and function may respond to this type of stimulus. The aim of this study was to compare RV structure and strain across the cardiac cycle and within individual segments in elite soccer players (SP) and controls (CON). Methods: Twenty-two highly trained, male pre-adolescent SP and 22 age-and sex-matched recreationally active individuals CON were investigated using 2D echocardiography, including myocardial speckle tracking to assess basal, mid-wall, apical and global longitudinal strain and strain rate during systole (SRS) and diastole (SRE and SRA). Results: greater RV cavity size was identified in the SP compared to CON (RVD1 SP: 32.3 ± 3.1 vs. CON: 29.6 ± 2.8 (mm/m2)0.5; p = 0.005). No inter-group differences were noted for peak global RV strain (SP: − 28.6 ± 4.9 vs CON: − 30.3 ± 4.0%, p = 0.11). Lower mid-wall strain was demonstrated in the SP compared to CON (SP: − 27.9 ± 5.8 vs. CON: − 32.2 ± 4.4%, p = 0.007). Conclusion: Soccer training has the potential to increase RV size in pre-adolescent players. The unique segmental analyses used in this study have identified inter-group differences that were masked by global strain evaluations. The clinical and physiological implications of these findings warrant further investigation.

Purpose: To examine the impact of environmental heat stress conditions on physical and technical football match-play characteristics.Method: Data from 42 matches of 9 outfields, professiona...

Purpose: To examine the reliability of HR measures obtained during the 6 min Yo-Yo Intermittent Recovery Test Level 1 (Yo-Yo IR1), and following a 3 min passive recovery, within a group of highly trained youth soccer players.\ud Methods: Eight players, completed three separate 6 min Yo-Yo IR1 tests, with a passive recovery, over a two week period. Measures of absolute heart rate (bpm) and relative HR (%HRmax) were obtained at the 3rd and 6th min of the test, with measures relative to the end HR (%HRend) 10, 20, 30, 60, 90 and 180 seconds, during the 3 min passive recovery. Variability in HR measures were assessed across successive trials (trial 1 vs. 2 and trial 2 vs. 3) and across all 3 trials, using the intraclass correlation coefficient (ICC), coefficient of variation (CV) and typical error (TE). Results: HR measures obtained during the 6 min Yo-Yo IR1 test displayed good levels of reliability (ICC: 0.95-0.98, CV: 1.1-1.3% and TE: 0.96-2.44).\ud Results, display a potential learning effect, with lower levels of variability between trial 2 vs. trial 3. Examination of %HRend obtained during the passive 3 min recovery demonstrated an increased variance, as the passive recovery period progressed.\ud Conclusion: The 6 min Yo-Yo IR1 test presents a novel and potentially practical approach to regularly assessing youth soccer players’ physical response to intermittent exercise. Practitioners and researchers should however, consider the need for appropriate familiarisation when undertaking this test.

Purpose: The purpose of the study was to examine differences in measures of cardiorespiratory fitness and determinants of running economy with respect to maturity status in a group of highly trained youth soccer players. Methods: A total of 21 highly trained youth soccer players participated in this study. On separate visits, players’ peak oxygen uptake (VO2peak), running economy at 3 different speeds [8 km·h−1, 80% gaseous exchange threshold (GET), and 95% GET], and pulmonary oxygen uptake (VO2) kinetics were determined. Players also performed a Yo-Yo intermittent recovery test level 1 (Yo-Yo IR1). Players were categorized as either “pre-PHV” (peak height velocity) or “mid-PHV” group using the measure of maturity offset. Independent t tests and Cohen’s d effect sizes were then used to assess differences between groups. Results: The mid-PHV group was significantly taller, heavier, and advanced in maturity status. Absolute measures of VO2peak were greater in the mid-PHV group; however, when expressed relative to body mass, fat-free mass, and theoretically derived exponents, VO2peak values were similar between groups. Pre-PHV group presented a significantly reduced VO2 response, during relative submaximal running speeds, when theoretically derived exponents were used, or expressed as %VO2peak. VO2 kinetics (tau) were faster during a low (standing) to moderate (95% GET) transition in the pre-PHV group. Yo-Yo IR1 performance was similar between groups. Conclusion: Although measures of VO2peak and Yo-Yo IR1 performance are shown to be similar between groups, those categorized as pre-PHV group display a superior running economy at relative submaximal running speeds and faster taus during a low to moderate exercise transition than their more mature counterparts.

BACKGROUND: The objective of this study was to investigate left ventricular (LV) circumferential strain responses to incremental cycling and isometric knee extension exercises.\ud METHODS: Twenty-six healthy male participants (age = 30 ± 6 years) were used to study LV global (GCS) and regional circumferential strain at the apex (ACS) and base (BCS) during incremental cycling at 30% and 60% work rate maximum (Wmax ) and short-duration (15 seconds contractions) isometric knee extensions at 40% and 75% maximum voluntary contraction (MVC) using two-dimensional speckle tracking echocardiography.\ud RESULTS: During cycling (n = 22), GCS increased progressively from rest to 60% Wmax (-22.85 ± 3.26% to -29.87 ± 2.59%, P < .01). ACS increased from rest to 30% Wmax (-26.29 ± 4.84% to -36.84 ± 6.94%, P < .01) and then remained unchanged to 60% Wmax (-40.72 ± 4.06%, P = .068). BCS decreased from rest to 30% Wmax (-19.41 ± 2.79 to -17.51 ± 4.66%, P = .05) and then remained unchanged to 60% Wmax . During isometric knee extension (n = 23), GCS decreased from rest to 40% MVC (-22.63 ± 3.46 to -20.10 ± 2.78%, P < .05) and then remained unchanged to 75% MVC. Similarly, BCS decreased from rest to 40% MVC (-19.21 ± 2.58% to -13.55 ± 3.45%, P < .01) and then remained unchanged, whereas ACS did not change with exercise intensity (rest, -26.05 ± 5.34%; 40% MVC, -26.64 ± 4.53% and 75% MVC -27.22 ± 5.34%, all P > .05).\ud CONCLUSION: Global circumferential strain increased stepwise during incremental cycling, mediated by the apex with trivial changes at the base. In contrast, GCS decreased during the isometric knee extension to 40% MVC and then plateaued, due to decreased BCS as ACS was maintained. A novel finding is that the GCS response appears to be exercise modality dependant and is the consequence of region-specific changes.

Purpose: The purpose of the study was to assess the validity, objectivity, and reliability of a Soccer-Specific Behaviour Measurement Tool (S-SBMT) in relation to the soccer philosophy of a Category One Premier League soccer academy. Methods: A 30 minute, 8 vs. 8 small-sided game (SSG), played by the U12 squad of the participating academy was used for analyses. Validity was ensured through formulating the S-SBMT definitions with experienced soccer coaches from the same soccer academy. Percentage agreement with a reference value of ±1, 95% Confidence Intervals, median sign and Yule’s Q were used to assess objectivity and reliability. Results: High levels of objectivity were found for the number of passes (98.8% agreement), runs with the ball (97.5% agreement), and goal attempts (100%). Reduced objectivity was apparent for forward zonal transitions (75.3%), along with tackles (70.4%), interceptions, (63%), and loose balls (48.1%). Reliability was tested after 1- and 4-weeks, with levels of percentage agreement found to be above the 85% acceptable threshold for most behaviours (passing = 95.1%, runs with the ball = 92.6%, goal attempts = 100%, tackles = 100%). Conclusions: The study demonstrated acceptable objectivity and reliability for S-SBMT behaviours and these findings demonstrate the potential utility of the S-SBMT in monitoring technical actions in a Category One Premier League soccer academy, and a methodological process for other academies to follow in ensuring the quality of performance data.

Aims This study aimed to evaluate left ventricular structure, function and mechanics, in highly-trained, pre-adolescent soccer players compared with age- and sex-matched controls. Design The study design was a prospective, cross-sectional comparison of left ventricular structure, function and mechanics. Methods Twenty-two male soccer players from two professional youth soccer academies (age: 12.0 ± 0.3 years) and 22 recreationally active controls (age: 11.7 ± 0.3 years) were recruited. Two-dimensional conventional and speckle tracking echocardiography were used to quantify left ventricular structure, function and peak/temporal values for left ventricular strain and twist, respectively. Results End-diastolic volume index was larger in soccer players (51 ± 8 mm/(m2)1.5 vs. 45 ± 6 mm/(m2)1.5; p = 0.007) and concentricity was lower in soccer players (4.3 ± 0.7 g/(mL)0.667 vs. 4.9 ± 1.0 g/(mL)0.667; p = 0.017), without differences in mean wall thickness between groups (6.0 ± 0.4 mm vs. 6.1 ± 0.5 mm; p = 0.754). Peak circumferential strain at the base (–22.2% ± 2.5% vs. –20.5% ± 2.5%; p = 0.029) and papillary muscle levels (–20.1% ± 1.5% vs. –18.3% ± 2.5%; p = 0.007) were greater in soccer players. Peak left ventricular twist was larger in soccer players (16.92° ± 7.55° vs. 12.34° ± 4.99°; p = 0.035) and longitudinal early diastolic strain rate was greater in soccer players (2.22 ± 0.40 s–1 vs. 2.02 ± 0.46 s–1; p = 0.025). Conclusions Highly-trained soccer players demonstrated augmented cardiac mechanics with greater circumferential strains, twist and faster diastolic lengthening in the absence of differences in wall thickness between soccer players and controls.

Purpose The interaction of ageing and exercise training status on left-ventricular (LV) peak strain is unclear. Additionally, strain analysis across the entire cardiac cycle facilitates a more detailed assessment of deformation, yet this has not been implemented to characterize the ageing LV and in association with training status. This study investigated healthy ageing and training status on LV systolic and diastolic strain utilizing novel echocardiographic applications. Methods Forty healthy males were included and allocated into four groups; young recreationally active (YRA, n = 9; 28 ± 5 years), old recreationally active (ORA, n = 10; 68 ± 6), young trained (YT, n = 10; 27 ± 6 years), and old trained (OT, n = 11, 64 ± 4 years) groups. Two-dimensional speckle-tracking echocardiography was performed to ascertain peak LV longitudinal and circumferential strain (base and apex) strain within each myocardial layer and at 5% increments across the cardiac cycle. Results Older groups had lower diastolic longitudinal lengthening and circumferential expansion between 40–85% mid-diastole, regardless of training status (P 0.05). Longitudinal and circumferential (base and apex) peak and layer-specific strain did not differ between groups (P > 0.05). Conclusion Novel applications of diastolic strain revealed lower age-associated LV longitudinal lengthening and circumferential expansion in older age. Yet, diastolic strain profiles did not differ based on chronic habits of exercise training and, thus, older trained men did not demonstrate an attenuation of age-associated differences in mid-diastolic LV strain. Electronic supplementary material The online version of this article (10.1007/s00421-020-04418-1) contains supplementary material, which is available to authorized users.

Dello Iacono, A, Beato, M, and Unnithan, V. Comparative effects of game profile-based training and small-sided games on physical performance of elite young soccer players. J Strength Cond Res 35(10): 2810-2817, 2021-This study was designed to investigate and compare the effects of game profile-based training (GPBT) and small-sided game (SSG) training on physical performances of elite youth soccer players during the in-season period. Twenty young soccer players (18.6 ± 0.6) were randomly assigned to either GPBT or SSG protocols performed twice a week for 8 weeks. The GPBT consisted of 2 sets of 6-10 minutes of intermittent soccer-specific circuits. The SSG training consisted of 3-5 sets of 5 vs. 5 SSGs played on a 42 × 30-m pitch. Before and after the training program, the following physical performances were assessed: repeated sprint ability, change of direction (COD), linear sprinting on 10 m and 20 m, countermovement jump, and intermittent running (YYIRL1). Significant improvements were found in all the assessed variables after both training interventions (p0.05). The GPBT group improved more than the SSG group in the 10-m and 20-m sprint tests by 2.4% (g = 0.4; small effect) and 4% (g = 0.9; large effect), respectively. Conversely, the SSG group jumped 4% higher (g = 0.4; small effect) and resulted 6.7% quicker than the GPBT (g = 1.5; large effect) in completing the COD task. These results suggest both GPBT and SSGs to be effective for fitness development among elite young soccer players during the competitive season. More importantly, these 2 conditioning methodologies may be considered in terms of specificity for selectively improving or maintaining specific soccer fitness-related performances in the latter phase of the season.

There were two aims of this study: first, to investigate physical fitness and match performance differences between under-16 (U16) and under-18 (U18) female basketball players, and second, to evaluate the relationship between physical fitness and game-related performances. Twenty-three young, female, elite Spanish basketball players (16.2 1.2 years) participated in the study. The sample was divided into two groups: U16 and U18 players. The average scores from pre- and post-season physical fitness measurements were used for subsequent analyses. Anthropometric variables were also measured. To evaluate game performance, game-related statistics, including the number of games and minutes played, points, rebounds, assists, steals and blocks per game, were recorded for every competitive match in one season. When anthropometric and physical performance variables were compared between groups, the U18 group demonstrated significantly (p

Purpose: To examine the relationship between oxygen uptake kinetics (VO2 kinetics) and physical measures associated with soccer match-play, within a group of highly trained youth soccer players.\ud Methods: Seventeen highly trained youth soccer players (age: 13.3 ± 0.4 yr, self-assessed Tanner Stage: 3 ± 1) volunteered for the study. Players initially completed an incremental treadmill protocol to exhaustion, to establish gaseous exchange threshold (GET) and VO2max (59.1 ± 5.4 mL.kg-1.min-1). On subsequent visits players completed a step transition protocol from, rest–moderate intensity exercise, followed by an immediate transition from moderate–severe intensity exercise (moderate: 95%GET, severe: 60%∆), during which VO2 kinetics were determined. Physical soccer-based performance was assessed using a maximal Yo-Yo Intermittent Recovery test level 1 (Yo-Yo IR1) and via GPS derived measures of physical soccer performance during soccer match-play, 3 2 x 20min, 11 v 11 matches, to gain measures of physical performance during soccer match-play. \ud Results: Partial correlations revealed significant inverse relationships between the unloaded to moderate transition time constant (tau) and: Yo-Yo IR1 performance (r = -0.58, P = 0.02) and GPS variables (Total distance (TD): r = - 0.64, P = 0.007, High speed running (HSR): r = - 0.64, P = 0.008, High speed running efforts (HSReff): r = - 0.66, P = 0.005). \ud Conclusion: Measures of VO2 kinetics are related to physical measures associated with soccer match-play and could potentially be used to distinguish between those of superior physical performance, within a group of highly-trained youth soccer players.

The aim of this study was to evaluate physiological and technical attributes of prepubertal soccer players during multiple small-sided games (SSGs), and determine if SSGs can act as a talent identification tool. Sixteen highly trained U10 soccer players participated and separated into two groups of eight. Each group played six small-sided (4 vs. 4) matches of 5-min duration. Each player was awarded total points for the match result and goals scored. A game technical scoring chart was used to rate each player's performance during each game. Time-motion characteristics were measured using micromechanical devices. Total points had a very large significant relationship with game technical scoring chart (r = 0.758, P 0.001). High-speed running distance had a significantly large correlation with game technical scoring chart (r = 0.547, P 0.05). Total distance covered had a significant and moderate correlation with game technical scoring chart (r = 0.545, P 0.05) and total points (r = 0.438, P 0.05). The results demonstrated a large agreement between the highest-rated players and success in multiple SSGs, possibly due to higher-rated players covering larger distances in total and at high speed. Consequently, multiple SSG could be used to identify the more talented prepubertal soccer players.

The purpose of this study was to assess the relationship between: Peak oxygen uptake (VO2max) and running economy (RE) with physical measures associated with elite youth soccer performance obtained during soccer match-play. Seventeen highly trained youth soccer players (age: 13.3±0.4y) volunteered to participate. Initially player’s ventilatory threshold (VT) and VO2max was established using a treadmill protocol. On the subsequent visit, players ran for 4 min, at three different speeds (8km/h, 80%VT and 95%VT). Physical soccer-based performance was assessed using a maximal Yo-Yo IR1 and via Global positioning systems (GPS) derived variables obtained during three, 2x20min, 11 v 11 soccer matches. Partial correlations revealed significant relationships between relative VO2max and measures of physical soccer performance (r = 0.54–0.88). Moreover, measures of ventilatory equivalent (VEVO2), a determinant of RE, at all sub-maximal exercise intensities were inversely related to the volume (m) and percentage (%) of very high intensity activities. Current findings emphasise the need for high levels of cardio-respiratory fitness in high level youth soccer players, with superior levels of fitness being associated with a greater amount of high and very high intensity activity during soccer match-play.

Doncaster, G and Unnithan, V. Between-game variation of physical soccer performance measures in highly trained youth soccer players. J Strength Cond Res 33(7): 1912-1920, 2019-To assess the between-game variation in measures of physical performance during 11 vs. 11 soccer match play, over a short period, in highly trained youth soccer players. A single-cohort, observational, study design was used. Physical match performance data were collected from 17, male, highly trained, youth soccer players (age, 13.3 ± 0.4 years) over 3, 2 × 20 minutes, 11 vs. 11 matches. Using 10-Hz global positioning systems, the variables selected for analyses were total distance (TD), high-speed running (HSR), very high-speed running (VHSR), number of high-speed running efforts (HSReff), and number of very high-speed running efforts (VHSReff). Match data were also separated into cumulative 5-minute epochs, to identify the peak 5-minute epoch and the mean of the cumulative 5-minute epochs for each match. Variability was quantified using the coefficient of variation (CV), standard error of measurement, and intraclass correlation coefficient. Between- and within-player smallest worthwhile changes (SWC) were also calculated for each variable to aid in the interpretation of the data. Analysis of the variance between games reported a low CV for TD (3.8%) but larger CVs for HSR (33.3%), HSReff (35.4%), and VHSR and VHSReff (59.6 and 57.4%, respectively). Analysis of 5-minute epochs (peak and average) found an increase in the CVs beyond that of the values reported for the whole match. Between-player SWC in high-intensity physical performance data ranged from 24.7 to 42.4%, whereas within-player SWC ranged from 1.2 to 79.9%. The between-game variability of high-intensity and very high-intensity activities in youth soccer players, across 3 soccer matches over a short period (2 weeks), is relatively "large" and specific to the individual, thus highlighting the need for caution when interpreting physical performance data between games and players.

Physical frailty has been regarded as a precursor state to disability and dependence on others for daily activities. Frail individuals are considered to be the group of patients that presents the most complex and challenging problems to health care professionals. The purpose of this study was to evaluate whether a 12-week functional circuit training program (FCT) could reduce self-reported fear of falling and improve health status in a group of physically frail community-dwelling older individuals. Fifty-one individuals (31 F, 20 M), mean age (SD) 84 (2.9) years old, were considered frail and tested at week 0 and randomly assigned into two groups (intervention group, FCT = 26; control group, CG = 25). FCT underwent a structured 12-week FCT program, which focused on a combination of functional balance and lower-body strength-based exercises. CG met once a week for health education meetings. Measures of self-reported fear of falling (Activities-specific Balance Confidence scale) and health status (SF-12) were assessed at week 0, 12 and 36. All longitudinal analyses for continuous variables that were measured at the three time points (week 0, 12 and 36) were performed using linear mixed modeling. FCT participants had greater improvements than those in the CG in fear of falling and self-reported physical function, physical composite score and mental composite score; these improvements were maintained in the week 36 follow-up, with significant group-by-time interactions by the end of the study. These data indicate that a FCT program is effective in improving self-reported measures of fear of falling and health status in a group of physically frail individuals.

The purpose of this review article was firstly to evaluate the traditional approach to talent identification in youth soccer and secondly present pilot data on a more holistic method for talent identification. Research evidence exists to suggest that talent identification mechanisms that are predicated upon the physical (anthropometric) attributes of the early maturing individual only serve to identify current performance levels. Greater body mass and stature have both been related to faster ball shooting speed and vertical jump capacity respectively in elite youth soccer players. This approach, however, may prematurely exclude those late maturing individuals. Multiple physiological measures have also been used in an effort to determine key predictors of performance; with agility and sprint times, being identified as variables that could discriminate between elite and sub-elite groups of adolescent soccer players. Successful soccer performance is the product of multiple systems interacting with one another. Consequently, a more holistic approach to talent identification should be considered. Recent work, with elite youth soccer players, has considered whether multiple small-sided games could act as a talent identification tool in this population. The results demonstrated that there was a moderate agreement between the more technically gifted soccer player and success during multiple small-sided games.

To compare the phase II oxygen uptake time constant (τV'O(2)) and V'O(2) mean response time (V'O(2)MRT) in overweight (OW) and non-OW (NO) children during moderate intensity exercise.Between subjects where participants completed a maximal ramp exercise test on an electromagnetically braked cycle ergometer to determine peak V'O(2) (V'O(2peak)) and gas exchange threshold (GET). Gas exchange was measured breath-by-breath using a mass spectrometer. On subsequent visits, 6 square-wave transitions (2 per day) from 0 W to 90% GET were completed. Individual phase II τV'O(2) and V'O(2)MRTs were estimated from time aligned average V'O(2) traces.Eleven OW (11.8±0.4 years) and 12 NO (11.9±0.4 years) children were recruited to the study. The OW group was significantly heavier (62.9±9.7 vs 39.4±5.8 kg, P0.001), taller (1.58±0.05 vs 1.47±0.07 m, P0.001) and had a higher body mass index (25.8±3.4 vs 18.3±1.8 kg m(-2), P0.001).Both τV'O(2) (30.2±9.6 vs 22.8±7.1 s, P0.05) and V'O(2)MRT (43.5±10.7 vs 36.3±5.3 s, P0.05) were significantly slower in OW compared with NO children; absolute V'O(2peak) was higher in the OW compared with NO group (2.23±0.04 vs 1.74±0.04 l min(-1), P0.05); mass relative V'O(2peak) was lower in OW compared with NO children (35.9±8.3 vs 43.8±6.2 ml kg(-1) min(-1), P0.05); allometrically scaled V'O(2peak) was similar between OW and NO groups whether relative to body mass(0.67) (139.8±29.1 vs 147.2±23.9 ml kg(-67) min(-1)) or stature(3) (576.0±87.2 vs 544.9±84.9 ml m(-3) min(-1)) (P0.05); absolute V'O(2) at GET was similar between OW and NO groups (0.94±0.24 vs 0.78±0.27 l min(-1), P0.05); GET expressed as percentage of V'O(2peak) was similar between the groups (42.0±0.1 vs 44.8±0.1%, P0.05).These findings demonstrate impairment in the factors determining V'O(2) kinetics in OW children at a relatively young age. Furthermore, assessment of cardiorespiratory fitness using peak exercise values is likely to be misleading and not useful when designing exercise programmes for OW children.

Orthostatic-induced alterations in Doppler echocardiographic measures of ventricular function have not been well-defined. Identifying such changes may provide useful insights regarding the responses of these measures to variations in ventricular loading conditions. Standard assessment of mitral inflow velocity and tissue Doppler imaging (TDI) of left ventricular longitudinal myocardial velocities was performed on 14 young males (mean age 17.9 ± 0.7 years) in the supine position and then 5 minutes after assuming a sitting position with legs dependent. Upon sitting, average values of stroke volume and cardiac output fell by 28% and 18%, respectively, while heart rate increased from 64 ± 10 to 73 ± 12 beats/min (+14%) and calculated systemic vascular resistance rose from 12.9 ± 2.2 to 16.4 ± 3.1 units (+27%). Mitral E peak velocity declined from 87 ± 16 to 64 ± 16 cm/sec, and average TDI-E' and TDI-S both decreased (by -44% and -20%, respectively). When adjusted for orthostatic decreases in left ventricular end-diastolic volume, the mean decrease in TDI-E' was reduced to -29 (P < 0.01), but no significant decline was observed in adjusted TDI-S. Average E/E' rose with sitting by 40% (P = 0.02). These findings suggest that (a) decreases in TDI measures when assuming the upright position reflect the reduction of left ventricular size; (b) orthostatic fall in TDI-E' is also related to smaller ventricular size but, in addition, to a nonspecified reduction in ventricular relaxation; and (c) values of E/E' do not reflect alterations in ventricular preload, which occur during an orthostatic challenge.

Background. Inspiratory muscle training (IMT) has been shown to improve inspiratory muscle function, lung volumes (vital capacity [VC] and total lung capacity [TLC]), work capacity, and power output in people who are healthy; however, no data exist that demonstrate the effect of varying intensities of IMT to produce these outcomes. Objectives. The purpose of this study was to evaluate the impact of IMT at varying intensities on inspiratory muscle function, VC, TLC, work capacity, and power output in people who are healthy. Design. This was a randomized controlled trial. Setting. The study was conducted in a clinical laboratory. Participants. Forty people who were healthy (mean age=21.7 years) were randomly assigned to 4 groups of 10 individuals. Interventions. Three of the groups completed an 8-week program of IMT set at 80%, 60%, and 40% of sustained maximum inspiratory effort. Training was performed 3 days per week, with 24 hours separating training sessions. A control group did not participate in any form of training. Measurements. Baseline and posttraining measurements of body composition, VC, TLC, inspiratory muscle function (including maximum inspiratory pressure [MIP] and sustained maximum inspiratory pressure [SMIP]), work capacity (minutes of exercise), and power output were obtained. Results. The participants in the 80%, 60%, and 40% training groups demonstrated significant increases in MIP and SMIP, whereas those in the 80% and 60% training groups had increased work capacity and power output. Only the 80% group improved their VC and TLC. The control group demonstrated no change in any outcome measures. Limitations. This study may have been underpowered to demonstrate improved work capacity and power output in individuals who trained at 40% of sustained maximum inspiratory effort. Conclusion. High-intensity IMT set at 80% of maximal effort resulted in increased MIP and SMIP, lung volumes, work capacity, and power output in individuals who were healthy, whereas IMT at 60% of maximal effort increased work capacity and power output only. Inspiratory muscle training intensities lower than 40% of maximal effort do not translate into quantitative functional outcomes.

Previous studies have demonstrated faster pulmonary oxygen uptake ( $$ \dot{V}{\text{O}}_{2} $$ ) kinetics in the trained state during the transition to and from moderate-intensity exercise in adults. Whilst a similar effect of training status has previously been observed during the on-transition in adolescents, whether this is also observed during recovery from exercise is presently unknown. The aim of the present study was therefore to examine $$ \dot{V}{\text{O}}_{2} $$ kinetics in trained and untrained male adolescents during recovery from moderate-intensity exercise. 15 trained (15 ± 0.8 years, $$ \dot{V}{\text{O}}_{2\max}$$ 54.9 ± 6.4 mL kg−1 min−1) and 8 untrained (15 ± 0.5 years, $$ \dot{V}{\text{O}}_{2\max }$$ 44.0 ± 4.6 mL kg−1 min−1) male adolescents performed two 6-min exercise off-transitions to 10 W from a preceding “baseline” of exercise at a workload equivalent to 80% lactate threshold; $$ \dot{V}{\text{O}}_{2} $$ (breath-by-breath) and muscle deoxyhaemoglobin (near-infrared spectroscopy) were measured continuously. The time constant of the fundamental phase of $$ \dot{V}{\text{O}}_{2} $$ off-kinetics was not different between trained and untrained (trained 27.8 ± 5.9 s vs. untrained 28.9 ± 7.6 s, P = 0.71). However, the time constant (trained 17.0 ± 7.5 s vs. untrained 32 ± 11 s, P

1 Centre of Excellence,RehabilitationCentre'De Hoogstraat', Utrecht,the Netherlands. 2 Partner ofNetChild, NetworkforChildhood DisabilityResearch,Utrecht, theNetherlands. 3 Department ofRehabilitation, Nursing Science and Sports, University Medical Center, Rudolf Magnus Institute ofNeuroscience,Utrecht, theNetherlands.4 Department ofWellness andSport Sciences, Millersville University, Millersville,PA, USA. 5 Holland Bloorview Kids Rehabilitation Hospital, Child Development Program,Toronto, ON, Canada. 6 Department of Physical Therapy, Universityof Toronto,Toronto, ON, Canada.7 Faculty ofHealth Sciences, TheUniversity ofSydney, Sydney, NSW,Australia.8 Health and Use ofTime Research Group, School ofHealthSciences, University ofSouth Australia, Adelaide,SA, Australia.9 School ofSport Science,Exercise andHealth, University ofWesternAustralia, Perth,WA, Australia.10 McMaster University, Hamilton,ON, Canada. 11Clinical Outcomes, Glenrose Rehabilitation Hospital, Edmonton,AB, Canada. 12Department of Physical Therapy, Facultyof RehabilitationMedicine,University ofAlberta,Edmonton,AB, Canada.13Department of Orthopaedic Surgery,UCLA⁄Orthopaedic HospitalCentre for CerebralPalsy, Universityof California,LosAngeles, CA,USA. 14 Centre forSport, Health andExercise Research, Staffordshire University,Stoke-on-Trent, Staffordshire, UK. 15Department of Rehabilitation, Laval University, QuebecCity, QC, Canada. 16Department of RehabilitationMedicineand PhysicalTherapy,ErasmusMedicalCenter, Rotterdam, theNetherlands. 17 ChildDevelopmentand Exercise Center, Wilhelmina Children'sHospital, UMC Utrecht, Utrecht, theNetherlands.

A recent report indicated that variations in myocardial functional (systolic and diastolic) responses to exercise do not contribute to inter-individual differences in aerobic fitness (peak VO(2)) among young males. This study was designed to investigate the same question among adolescent females. Thirteen highly fit adolescent football (soccer) players (peak VO(2) 43.5 ± 3.4 ml kg(-1) min(-1)) and nine untrained girls (peak VO(2) 36.0 ± 5.1 ml kg(-1) min(-1)) matched for age underwent a progressive cycle exercise test to exhaustion. Cardiac variables were measured by standard echocardiographic techniques. Maximal stroke index was greater in the high-fit group (50 ± 5 vs. 41 ± 4 ml m(-2)), but no significant group differences were observed in maximal heart rate or arterial venous oxygen difference. Increases in markers of both systolic (ejection rate, tissue Doppler S') and diastolic (tissue Doppler E', mitral E velocity) myocardial functions at rest and during the acute bout of exercise were similar in the two groups. This study suggests that among healthy adolescent females, like young males, myocardial systolic and diastolic functional capacities do not contribute to inter-individual variability in physiologic aerobic fitness.

The purpose of this study was to evaluate whether a 12-wk functional circuit-training program (FCT) could alter markers of physical frailty in a group of frail community-dwelling adults. Fifty-one individuals (31 women, 20 men), mean age (± SD) 84 (± 2.9) yr, met frailty criteria and were randomly assigned into groups (FCT = 26, control group [CG] = 25). FCT underwent a 12-wk exercise program. CG met once a week for health education meetings. Measures of physical frailty, function, strength, balance, and gait speed were assessed at Weeks 0, 12, and 36. Physical-frailty measures in FCT showed significant (p < .05) improvements relative to those in CG (Barthel Index at Weeks 0 and 36: 73.41 (± 2.35) and 77.0 (± 2.38) for the FCT and 70.79 (± 2.53) and 66.73 (± 2.73) for the CG. These data indicate that an FCT program is effective in improving measures of function and reducing physical frailty among frail older adults.

Exercise training results in a speeding of pulmonary oxygen uptake (V˙ O2) kinetics at the onset of exercise in adults; however, only limited research has been conducted with children and adolescents. Purpose: The aim of the present study was to examine V˙ O2 and muscle deoxygenation kinetics in trained and untrained male adolescents. Methods: Sixteen trained (15 T 0.8 yr, V˙ O2peak = 54.7 T 6.2 mLIkgj1Iminj1, selfassessed Tanner stage range 2–4) and nine untrained (15 T 0.6 yr, V˙ O2peak = 43.1 T 5.2 mLIkgj1Iminj1, Tanner stage range 2–4) male adolescents performed two 6-min exercise transitions from a 3-min baseline of 10 W to a workload equivalent to 80% lactate threshold separated by a minimum of 1 h of passive rest. Oxygen uptake (breath-by-breath) and muscle deoxygenation (deoxyhemoglobin signal from near-infrared spectroscopy) were measured continuously throughout baseline and exercise transition. Results: The time constant of the fundamental phase of V˙ O2 kinetics was significantly faster in trained versus untrained subjects (trained: 22.3 T 7.2 s vs untrained:29.8 T 8.4 s, P = 0.03). In contrast, neither the time constant (trained: 9.7 T 2.9 s vs untrained: 10.1 T 3.4 s, P = 0.78) nor the mean response time (trained: 17.4 T 2.5 s vs untrained: 18.3 T 2.3 s, P = 0.39) of muscle deoxygenation kinetics differed with training status. Conclusions: The present data suggest that exercise training results in faster V˙ O2 kinetics in male adolescents, although inherent capabilities cannot be ruled out. Because muscle deoxygenation kinetics were unchanged, it is likely that faster V˙ O2 kinetics were due to adaptations to both the cardiovascular system and the peripheral musculature.

Aim: This cross-sectional study examined factors related to children's physical fitness and activity levels in Taiwan. Methods: A total of 331 Taiwanese children, aged 7 and 8, and their mothers participated in the study. Children performed physical fitness tests, recorded their physical activities during two weekdays and completed self-esteem questionnaires. Research assistants measured the children's body mass and stature. Mothers completed demographic, parenting style and physical activity questionnaires. Results: Attending urban school, lower body mass index (BMI), older age and better muscular endurance contributed to the variance in better aerobic capacity, and attending rural school and better aerobic capacity contributed to the variance in better muscular endurance in boys. Attending urban school, lower BMI and better athletic competence contributed to the variance in better aerobic capacity, and younger age, rural school and higher household income contributed to the variance in better flexibility in girls. Conclusion: Despite the limitations of the study, with many countries and regions, including Taiwan, now emphasizing the importance of improving physical fitness and activity in children, an intervention that is gender-, geographically, and developmentally appropriate can improve the likelihood of successful physical fitness and activity programmes.

Objective: Obesity has been proposed to negatively impact cardiac function in overweight (OW) individuals. The relationship between diastolic dysfunction and oxygen uptake (Vo2) kinetics is equivocal. This exploratory investigation evaluated the relationship between resting left ventricular function and Vo2 kinetics during cycle ergometry in OW and non-overweight (NO) children and adolescents. Research Methods and Procedures: Fourteen OW (>85 percentile for BMI for age and gender) children, 10 boys and 4 girls (age, 11.7 ± 1.9 years; body mass, 80.6 ± 45.5 kg) and 10 NO children (4 boys, 6 girls) volunteered to participate in the study (age, 12.5 ± 2.1 years; body mass, 45.8 ± 13.8 kg). Resting cardiovascular structure and function were assessed using spectral Doppler echocardiography. All subjects underwent two sub-maximal exercise stages on a cycle ergometer (3 minutes unloaded and 5 minutes at 50 W, both at a cadence of 50 rpm). Respiratory data were measured on a breath-by-breath basis at both workloads and the mean response time (MRT) was calculated. Results: Analysis of the MRT data demonstrated that there were no significant differences between OW and NO (OW, 52.6 ± 11.7 seconds vs. NO, 45.6 ± 7.4 seconds). Significant correlations (p < 0.05) were obtained between MRT Vo2 and echocardiographic-derived mitral valve inflow pressure half-time (r = 0.55) and between MRT Vo2, and mitral valve inflow deceleration time (r = 0.55). Discussion: The evidence from this research suggests a possible link between left ventricular diastolic function at rest and oxygen uptake kinetics during sub-maximal exercise in OW and NO children and adolescents.

A longitudinal study design was used to examine factors related to change of body mass index (BMI) over a 1-year period in 307 Chinese children, aged 7 and 8 years, in Taiwan. Standardized instruments were used to measure the children's food intake, physical activity/inactivity, and physical fitness, as well as maternal BMI. Results suggested that a high baseline BMI, poor aerobic capacity, and a high maternal BMI were significantly correlated with increased BMI at 12 months' follow-up. A higher baseline BMI, an overweight mother, increased television viewing and computer time, and poorer aerobic capacity were identified as predictors for weight gain in children (F=207.67; P

Low-back pain;measurement error;random error;spinal mobility;systematic bias Aim: Evidence of the reliability of measurements in children is scarce, particularly in children with low-back pain. The aim of this investigation was to evaluate the measurement error associated with repeated measures of spinal mobility measures in children with and without low-back pain by establishing 95% limits of agreement. Methods: A repeated measures study was performed involving 119 children aged 11–16 y. Of this sample 30 subjects reported recurrent low-back pain and were classified as symptomatic, the remaining 89 subjects were asymptomatic. Standardized measures were taken, including the sit-and-reach test, hip range of motion (Leighton flexometer), lumbar flexibility (modified Schober test) and lateral flexion of the spine. The same experimenter performed all testing, with 1 wk between the repeated measures. Results: Correlation coefficients suggested that all measures exhibited good reliability in both the symptomatic (r= 0.80–0.95) and asymptomatic groups (r= 0.88–0.99). In contrast, the limits of agreement showed that all measures exhibited random error. The magnitude of random error was typically greater in the symptomatic subjects, suggesting that low-back pain may influence the reliability of typical measures used in this population. Conclusion: The magnitude of error must be interpreted in relation to analytical goals and the expected magnitude of change. In the authors' opinion the error presented appears acceptable for the serial monitoring of patients, although this will depend on the differences in mobility typically found.

The purpose of this study was to determine if there were any differences in the submaximal energy cost of movement between overweight (OW) and non-overweight (NO) children while playing a dance simulation video game, Dance Dance Revolution (DDR) and to determine if the cardiorespiratory measures obtained while playing the game met the American College of Sports Medicine (ACSM) recommendations for developing and maintaining cardiorespiratory fitness. Twenty-two children and adolescents (10 OW vs. 12 NO) participated in the study. Cardiorespiratory measurements were taken both during a maximal treadmill walking test and during a 12-minute Dance Dance Revolution protocol. The average absolute VO2 (OW: 917.1 +/- 257.1 vs. 590.6 +/- 147.9 mL . min (-1)) sustained over the DDR protocol was significantly higher in the OW group compared to the NO group. There was no significant difference in the average energy cost of movement when VO2 was normalized to fat-free mass (OW: 17.7 +/- 5.1 vs. NO: 17.3 +/- 3.9 mL . kgFFM (-1) . min (-1)). Both groups were above the minimal ACSM recommended heart rate intensity for developing and maintaining cardiorespiratory fitness when participating in the DDR protocol (OW: 64.83 % +/- 7.14 vs. NO: 64.51 % +/- 7.71), VO2 reserve, however, did not meet ACSM standards for developing and maintaining cardiorespiratory fitness.

Background and Purpose. Previous investigations have demonstrated that a regimen of high-intensity inspiratory muscle training (IMT) resulted in changes in ventilatory function and exercise capacity in patients with chronic lung disease, although the effect of high-intensity IMT in subjects who are healthy is yet to be determined. The purpose of this study, therefore, was to examine whether high-intensity IMT resulted in changes in ventilatory function and exercise capacity in subjects who were healthy. Subjects. Twenty subjects were randomly assigned to 2 groups. Methods. The training group completed an 8-week program of IMT set at 80% of maximal effort. The control group did not participate in any form of training. Baseline and posttraining measures of body composition, pulmonary function, inspiratory muscle function (including maximal and sustained maximal inspiratory pressures [MIP and SMIP]), relaxed and contracted diaphragm thickness and thickening ratio (Tdi.rel, Tdi.cont, and TR), and exercise capacity were determined. Results. The training group demonstrated significant increases in MIP, SMIP, Tdi.cont, TR, VC, total lung capacity, and exercise capacity compared with the control group, which demonstrated no change from baseline measurements at 8 weeks. Discussion and Conclusion. The findings of this study suggest that high-intensity IMT results in increased contracted diaphragm thickness and increased lung volumes and exercise capacity in people who are healthy. [Enright SJ, Unnithan VB, Heward C, et al. Effect of high-intensity inspiratory muscle training on lung volumes, diaphragm thickness, and exercise capacity in subjects who are healthy.

Treadmill training in claudication is often based on walking exercise to a pain threshold or longer to the maximum muscle pain of the lower limbs. This kind of exercise may cause an inflammatory response. The purpose of this study was to determine whether pain-free treadmill training using walking exercise to 85% of the distance to onset of claudication pain can significantly improve pain-free walking distance in patients with intermittent claudication and to evaluate whether this kind of program may induce an inflammatory response leading to the progression of atherosclerosis.A total of 98 patients aged 50-70 yrs with stable intermittent claudication were randomized into a supervised treadmill training program or a comparison group. Patients in the treatment group participated in 12 wks of supervised treadmill training. We examined the effects of 12 wks of pain-free treadmill training on pain-free walking distance, total leukocyte count, neutrophil count, and microalbuminuria in patients with claudication.A total of 80 participants completed the program. Exercise rehabilitation increased the time to onset of claudication pain by 119.2%, from 87.4 +/- 38 m to 191.6 +/- 94.8 m (P0.001). There was no increase in total leukocyte count, neutrophil count, or microalbuminuria after 12 wks of treadmill exercise (P0.05)A pain-free training program can be used in the treatment of claudication as a low-risk program, increasing walking ability without potential harmful effects of ischemia-reperfusion injury.

The aim of this study was to examine the effect of upper-limb dominance on the forearm sweating pattern in cerebral palsy (CP). Eight boys with CP (13.1 ± 3.1 years) performed three 10-min bouts of an arm-cranking exercise at 35°C, 50% relative humidity. After the third bout, the sweat drops on both forearms were photographed. Sweat gland density (PD) and the average sweat drop area (DA) were determined. PD was significantly higher (p < .05), whereas DA was significantly lower (p < .05) on the nondominant compared with the dominant forearm. The sweating pattern in spastic CP is influenced by upper-limb dominance.

PURPOSE When metabolic rate during arm-cranking in the heat is equated between children and adolescents with cerebral palsy (CP) and matched controls (CON), there are no relevant intergroup differences in heat strain. The metabolic rate, however, is known to be higher in CP during treadmill walking. The purpose of this study was to determine if during treadmill walking in the heat, the higher oxygen uptake (VO2), and thus greater metabolic heat production in those with CP would result in greater heat strain compared with able-bodied, matched CON. METHODS Ten boys and girls (10.3-16.3 yr) with spastic CP and 10 individually matched (age, body size, biological maturity, gender, race) healthy CON performed 3 x 10-min treadmill walking bouts in 35 degrees C, 50% RH. Body mass, metabolic variables, heart rate (HR), body temperatures, and rating of perceived exertion (RPE) were periodically measured. Individuals within each CP-CON pair walked at the same speed and slope (0.9 +/- 0.4 m x s(-1), 3.3 +/- 0.6%). RESULTS Steady-state VO2 during walking, body temperatures, and HR were all higher in the CP group compared with CON. VO2 was on average 40% higher, rectal temperature was 0.4 degrees C (99% CI = 0.1-0.6 degrees C) higher and HR (during the final minute of each exercise bout) was 37 beats x min(-1) (99% CI = 19-56 beats x min(-1)) higher. There were no differences between the groups in sweating rate (as inferred from body mass changes corrected for fluid intake and output) or in RPE. CONCLUSION The subjects with CP demonstrated greater thermal strain than CON during treadmill walking where they require more metabolic energy and thus produce more metabolic heat than CON.

Study objectives: To investigate the effects of high-intensity inspiratory muscle training (IMT) on inspiratory muscle function (IMF), diaphragm thickness, lung function, physical work capacity (PWC), and psychosocial status in patients with cystic fibrosis (CF). Design: Twenty-nine adult patients with CF were randomly assigned to three groups. Two groups were required to complete an 8-week program of IMT in which the training intensity was set at either 80% of maximal effort (group 1; 9 patients) or 20% of maximal effort (group 2; 10 patients). A third group of patients did not participate in any form of training and acted as a control group (group 3; 10 patients). Interventions: In all patients, baseline and postintervention measures of IMF were determined by maximal inspiratory pressure (PImax), and sustained PImax (SPImax); pulmonary function, body composition, and physical activity status were also determined. In addition, diaphragm thickness was measured at functional residual capacity (FRC) and total lung capacity (TLC) [TDIcont], and the diaphragm thickening ratio (TR) was calculated (TR thickness during PImax at FRC/mean thickness at FRC). Subjects also completed an incremental cycle ergometer test to exhaustion and two symptom-related questionnaires, prior to and following training. Results: Following training, significant increases in PImax and SPImax (p < 0.05), TDIcont (p < 0.05), TR (p < 0.05), vital capacity (p < 0.05), TLC (p < 0.05), and PWC (p < 0.05) were identified, and decreases in anxiety scores (p < 0.05) and depression scores (p < 0.01) were noted in group 1 patients compared to group 3 patients. Group 2 patients significantly improved PImax and SPImax (both p < 0.05) only with respect to group 3 patients. No significant differences were observed in group 3 patients. Conclusion: An 8-week program of high-intensity IMT resulted in significant benefits for CF patients, which included increased IMF and thickness of the diaphragm (during contraction), improved lung volumes, increased PWC, and improved psychosocial status. (CHEST 2004; 126:405– 411)