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1.
ObjectivesWe examined whether mild heat exposure alters performance, perceptual responses and neural drive to the quadriceps during two sets of repeated sprints matched for initial mechanical output.DesignRepeated measures.MethodsTwelve males performed 10 × 6-s sprints (recovery = 30 s), followed 6 min later by 5 × 6-s sprints (recovery = 30 s) in either COOL (24 °C/30% rH) or HOT (35 °C/40% rH) conditions. Subsequently, two sets of five consecutive sprints matched for initial mechanical output were compared.ResultsOn the basis of peak power, performance in sprint 2 was not significantly different to sprint 11 in both conditions (p ≥ 0.32). Average peak power across the five sprints compared (i.e., sprints 2–6 and 11–15, respectively) was 2.6 ± 3.4% higher in HOT compared to COOL (p = 0.025). Electromyographic activity (root mean square value) of the vastus lateralis muscle remained unchanged. Core (sprints 2–6: 37.85 ± 0.21 vs. 37.53 ± 0.19 °C, sprints 11–15: 38.26 ± 0.33 vs. 37.89 ± 0.24 °C; p < 0.001) and skin (sprints 2–6: 36.21 ± 0.29 vs. 30.72 ± 0.52 °C, sprints 11–15: 36.37 ± 0.28 vs. 30.99 ± 0.55 °C; p < 0.001) temperatures were overall higher in HOT compared to COOL. Heart rate, thermal sensation and comfort were significantly elevated in HOT compared to COOL (p ≤ 0.02), irrespective of sprint number.ConclusionsWhen two sets of repeated sprints were matched for initial mechanical output, performance was enhanced with mild heat exposure. This occurred despite higher thermal, cardiovascular, and perceptual strain, and without alterations in quadriceps neural drive.  相似文献   

2.
The aim of the present study was to investigate the effects of age and recovery duration on the time course of cycling peak power and blood lactate concentration ([La]) during repeated bouts of short-term high-intensity exercise. Eleven prepubescent boys (9.6 +/- 0.7 yr), nine pubescent boys (15.0 +/- 0.7 yr) and ten men (20.4 +/- 0.8 yr) performed ten consecutive 10 s cycling sprints separated by either 30 s (R30), 1 min (R1), or 5 min (R5) passive recovery intervals against a friction load corresponding to 50 % of their optimal force (50 % Ffopt). Peak power produced at 50 % Ffopt (PP50) was calculated at each sprint including the flywheel inertia of the bicycle. Arterialized capillary blood samples were collected at rest and during the sprint exercises to measure the time course of [La]. In the prepubescent boys, whatever recovery intervals, PP50 remained unchanged during the ten 10 s sprint exercises. In the pubescent boys, PP50 decreased significantly by 18.5 % (p < 0.001) with R30 and by 15.3 % (p < 0.01) with R1 from the first to the tenth sprint but remained unchanged with R5. In the men, PP50 decreased respectively by 28.5 % (p < 0.001) and 11.3 % (p < 0.01) with R30 and R1 and slightly diminished with R5. For each recovery interval, the increase in blood [La] over the ten sprints was significantly lower in the prepubescent boys compared with the pubescent boys and the men. To conclude, the prepubescent boys sustained their PP50 during the ten 10 s sprint exercises with only 30 s recovery intervals. In contrast, the pubescent boys and the men needed 5 min recovery intervals. It was suggested that the faster recovery of PP50 in the prepubescent boys was due to their lower muscle glycolytic activity and their higher muscle oxidative capacity allowing a faster resynthesis in phosphocreatine.  相似文献   

3.
ObjectivesThe purpose of this study was to investigate the acute vascular and oxygenation responses to repeated sprint exercise during arm cycling with either blood flow restriction (BFR) or systemic hypoxia alone or in combination.DesignThe study design was a single-blinded repeated-measures assessment of four conditions with two levels of normobaric hypoxia (400 m and 3800 m) and two levels of BFR (0% and 45% of total occlusion).MethodsSixteen active participants (eleven men and five women; mean ± SD; 26.4 ± 4.0 years old; 73.8 ± 9.8 kg; 1.79 ± 0.07 m) completed 5 sessions (1 familiarization, 4 conditions). During each test visit, participants performed a repeated sprint arm cycling test to exhaustion (10 s maximal sprints with 20 s recovery until exhaustion) to measure power output, metabolic equivalents, blood flow, as well as oxygenation (near-infrared spectroscopy) of the biceps brachii muscle tissue.ResultsRepeated sprint performance was decreased with both BFR and systemic hypoxia conditions. Greater changes between minimum-maximum of sprints in total hemoglobin concentration (Δ[tHb]) were demonstrated with BFR (400 m, 45% and 3800 m, 45%) than without (400 m, 0% and 3800 m, 0%) (p < 0.001 for both). Additionally, delta tissue saturation index (ΔTSI) decreased more with both BFR conditions than without (p < 0.001 for both). The absolute maximum TSI was progressively reduced with both BFR and systemic hypoxia (p < 0.001).ConclusionsBy combining high-intensity, repeated sprint exercise with BFR and/or systemic hypoxia, there is a robust stimulus detected by increased changes in blood perfusion placed on specific vascular mechanisms, which were more prominent in BFR conditions.  相似文献   

4.
The effect of recovery duration on performance and fatigue pattern during short exercises was studied including and excluding the flywheel inertia. Subjects (11 males and 11 females) performed a force-velocity test to determine their optimal force (f (opt)). On the following day, subjects performed randomly 4 series of two 8-s sprints against f (opt), with 15 s (R (15)), 30 s (R (30)), 60 s (R (60)), and 120 s (R (120)) recovery between sprints. The cycle (Monark 824 E, Stockholm, Sweden) was equipped with an optical sensor to calculate the revolution velocity of the pedal. For each sprint, peak power (P (peak)), mechanical work (W) and time to reach P (peak) (t (Ppeak)) were calculated including (I) and excluding (NI) the acceleration of the flywheel. For a given sprint, P (peak) and W were greater and t (Ppeak) was lower in I compared to NI condition (p < 0.05). Differences averaged 13 % for P (peak), 20 % for W, 34 % for t (Ppeak), and remained constant between sprints 1 and 2. In sprint 2, P (peak) and W were significantly reduced compared to sprint 1 only after R (15) and R (30) in I and NI (p < 0.05), and no gender differences occurred. In each sprint, P (peak) and W were higher (p < 0.001) and t (Ppeak) was shorter (p < 0.05) in males than in females, and gender differences were the same including or excluding the flywheel inertia. In conclusion, values excluding inertia underestimated mechanical performance and consequently the total energy supply. However, the pattern of fatigue and gender differences in performance and fatigue remained unchanged whatever the condition (I or NI). This result may have practical implications when the flywheel inertia can not be taken into account in the calculation of mechanical work and power output.  相似文献   

5.
PURPOSE: To compare active versus passive recovery on performance and metabolism during a test of repeated-sprint ability. METHODS: Nine males performed four repeated-sprint cycle tests (six 4-s sprints, every 25 s) in a randomized, counterbalanced order: two tests with active recovery (approximately 32% VO2max) and two with passive recovery. Muscle biopsies were taken during the four tests from the vastus lateralis pretest, immediately posttest, and following 21 s of recovery to determine phosphocreatine ([PCr]), creatine, and muscle lactate concentration ([MLa]). RESULTS: Active recovery resulted in a greater power decrement than passive recovery (7.4 +/- 2.2 vs 5.6 +/- 1.8%, P = 0.01) and lower final peak power (14.9 +/- 1.5 vs 15.3 +/- 1.5 W.kg(-1), P = 0.02). However, there was no significant difference in work decrement or total work. The percent of resting [PCr] was lower and approached significance posttest (32.6 +/- 10.6 vs 45.3 +/- 18.6%; P = 0.06; effect size (ES) = 0.8) and following 21 s of recovery (54.6 +/- 9.6 vs 71.7 +/- 14.1%; P = 0.06; ES = 1.2) during active recovery. The [MLa] was significantly higher posttest during active recovery (71.7 +/- 12.3 vs 55.2 +/- 15.7 mmol.kg(-1)dm; P = 0.048; ES = 1.2); however, no significant differences were evident following 21 s of recovery (55.0 +/- 11.3 vs 48.4 +/- 16.7 mmol.kg(-1)dm, P = 0.07; ES = 0.5). CONCLUSIONS: Despite no differences in the majority of performance measures, active recovery resulted in a significantly lower final peak power, a greater peak power decrement, a higher [MLa], and a strong trend towards lower [PCr], suggesting a potential suboptimal effect of active recovery during repeated-sprint exercise.  相似文献   

6.
PURPOSE: To determine how factors are related to change in cardiorespiratory fitness (CRF) across time in middle school girls followed through high school. METHODS: Adolescent girls (N = 274, 59% African American, baseline age = 13.6 +/- 0.6 yr) performed a submaximal fitness test (PWC170) in 8th, 9th, and 12th grades. Height, weight, sports participation, and physical activity were also measured. Moderate-to-vigorous physical activity (MVPA) and vigorous physical activity (VPA) were determined by the number of blocks reported on the 3-Day Physical Activity Recall (3DPAR). Individual differences and developmental change in CRF were assessed simultaneously by calculating individual growth curves for each participant, using growth curve modeling. RESULTS: Both weight-relative and absolute CRF increased from 8th to 9th grade and decreased from 9th to 12th grade. On average, girls lost 0.16 kg.m.min.kg.yr in weight-relative PWC170 scores (P < 0.01) and gained 10.3 kg.m.min.yr in absolute PWC170 scores. Girls reporting two or more blocks of MVPA or one or more blocks of VPA at baseline showed an average increase in PWC170 scores of 0.40-0.52 kg.m.min.kg.yr (weight relative) and 22-28 kg.m.min.yr (absolute) in CRF. In weight-relative models, girls with higher BMI showed lower CRF (approximately 0.37 g.m.min.kg.yr), but this was not shown in absolute models. In absolute models, white girls (approximately 40 kg.m.min.yr) and sport participants (approximately 28 kg.m.min.yr) showed an increase in CRF over time. CONCLUSION: Although there were fluctuations in PWC170 scores across time, average scores decreased during 4 yr. Physical activity was related to change in CRF over time; BMI, race, and sport participation were also important factors related to change over time in CRF (depending on expression of CRF-weight-relative vs absolute). Subsequent research should focus on explaining the complex longitudinal interactions between CRF, physical activity, race, BMI, and sports participation.  相似文献   

7.
Physical fitness, cognitive performance, and aging   总被引:2,自引:0,他引:2  
The relationship between physical fitness and cognitive performance in old age is examined in the light of contemporary capacity theories of attention. It is suggested that a model of cognition based upon the notion of a declining attentional capacity with advancing age provides a valuable conceptual framework for examining the influence of physical fitness on cognitive performance in old age. A direct prediction of the model is that cognitive tasks which require effortful processing should be more sensitive to the effects of fitness than tasks which can be performed without or with minimal attention. It is suggested that future research in the area of exercise and cognition systematically manipulate the attentional requirements of the tasks selected for the evaluation of cognitive performance. The implications of such a task-dependent association between physical fitness and cognitive performance for future research are discussed.  相似文献   

8.
9.
The aim of this study was to investigate the effects of age and recovery duration on performance during multiple treadmill sprints. Twelve boys (11.7 +/- 0.5 y) and thirteen men (22.1 +/- 2.9 y) performed ten consecutive 10-s sprints on a non-motorised treadmill separated by 15-s (R15) and 180-s (R180) passive recovery intervals. Mean power output (MPO), mean force output (MFO), running velocity, step length, and step rate were calculated for each sprint. Capillary blood samples were drawn from the fingertip at rest and 3 min after the tenth sprint to measure the lactate accumulation (Delta [La]). With R15, all mechanical parameters decreased significantly less in the boys than in the men over the ten sprints (MPO: - 28.9 vs. - 47.0 %, MFO: - 13.1 vs. - 25.6 %, running velocity: - 18.8 vs. - 29.4 %, p < 0.001, respectively). With R180, all mechanical values remained unchanged in the boys. In the men, MPO and MFO significantly decreased over the ten sprints (- 7.8 % and - 4.6 %, p < 0.05, respectively). The running velocity, however, did not decrease because the decrease in step rate (p < 0.001) was compensated by an increase in step length. For either recovery interval, Delta [La] values were higher in the men compared to the boys (R15: 12.7 vs. 7.7 mmol . L (-1), p < 0.001, R180: 10.7 vs. 7.7 mmol . L (-1), p < 0.05). To conclude, the boys maintained more easily their running performance than the men during repeated treadmill sprints with R15. Three-minute recovery periods were sufficient in the boys to repeat short running sprints without substantial fatigue. Despite the decrease in power and force outputs with R180, the young men were able to maintain their running velocity during the test.  相似文献   

10.
PURPOSE: To characterize the impact of prolonged work, underfeeding, and sleep deprivation (i.e., sustained operations; SUSOPS) on physical and occupational related performance during military operational stress. METHODS: Ten male soldiers were tested on days 1 (D1), 3 (D3), and 4 (D4) of a control and an experimental week that included prolonged physical work (total daily energy expenditure approximately 4,500 kcal x d(-1)), underfeeding (approximately 1,600 kcal x d(-1)), and sleep deprivation (approximately 2 h x d(-1)). Body composition was measured with dual-energy x-ray absorptiometry (DEXA). Ballistic power was assessed by 30 repetitive squat jumps and bench-press throws. Military-relevant occupational performance was evaluated with a 10-min box lift, obstacle course, grenade throw, rifle marksmanship, and a 25-min wall-build task. RESULTS: Fat-free mass (-2.3%) and fat mass (-7.3%) declined (P 相似文献   

11.
12.
Seven high school boys (16.4 +/- 0.5 y, mean +/- SD) and 7 girls (16.4 +/- 0.5 y), who specialized in track and field events, performed ten 5-s maximal sprint runs with an interval of 10s between each sprint on a non-motorized running ergometer. In each sprint, the mean mechanical power (MP) from the start until the belt velocity of the ergometer (i. e., running velocity) peaked was calculated. The boys showed significantly higher MP than the girls in all sprints. However, when MP was expressed as the ratio to the total volume of muscles located in the right lower limb (MP x MV(-1)), estimated using a bioelectrical impedance analysis, significant gender effect was limited to the values at the 1 st and 2 nd sprints. The decline of MP over the ten sprints, expressed as a relative value to that at the 1 st sprint, was greater in boys (46.2 +/- 7.6 %) than in girls (33.9 +/- 8.6 %), and significantly correlated with MP x MV(-1) at the 1st sprint (r = 0.568, p < 0.05). However, no significant difference between the boys and girls was found in the relative difference between MP values at the 3rd and 10th sprints, where the gender difference in MP x MV(-1) at every sprint was insignificant. The findings here indicate that, for trained teenage boys and girls, (1) significant gender difference in mechanical power developed during repeated bouts of maximal running exists only in the initial phase of the task, when the difference in the volume of the lower limb muscles is normalized, and (2) it may be a reason for a greater decline of mechanical power developed during the bout in boys compared to girls.  相似文献   

13.
ObjectiveInvestigate the acute effects of repeated combat sports matches on vertical jump and handgrip strength performance in grappling and striking modalities.DesignSystematic review.MethodsPubMed, Scopus, and Web of Science databases were searched. The following eligibility criteria for selecting studies were adopted: Population: Combat sports athletes; Intervention: Official or simulated matches; Comparator: Baseline versus after-matches performance; Outcome: Vertical jump and/or handgrip strength performance. PROSPERO: CRD42019129264ResultsThe systematic search resulted in 13 studies, including Brazilian jiu-jitsu, Greco-Roman, judo, taekwondo, and wrestling (freestyle and Greco-Roman) modalities, and a diverse number of repeated matches (i.e. 1–5). None of the studies adopted a randomized and controlled design and, consequently, none of them was classified as high quality. Brazilian jiu-jitsu and freestyle wrestling athletes presented an earlier onset of fatigue in upper and lower limbs, while judo and Greco Roman wrestling presented a later onset, from the third match. In taekwondo athletes, no fatigue was observed in the lower limbs, while handgrip strength decreased. However, studies have reported unclear data regarding the time-course of lower and upper limbs’ fatigue following repeated matches in taekwondo.ConclusionBoth upper and lower limbs performance were affected after repeated matches in grappling combat sports when assessed by handgrip strength and vertical jump performance. In taekwondo, the studies have shown unclear results concerning the effects of repeated matches on upper and lower limb performance. There is a lack of studies classified as high-quality and investigations into the neuromuscular mechanisms underpinning fatigue after the repeated matches.  相似文献   

14.
PURPOSE: This paper attempts to develop production functions (PF) between aerobic exercise inputs and long-run health outputs. Future studies could use such PF for estimating the benefits and costs (broadly defined) of different exercise programs to help develop optimal (utility maximizing) ones. METHODS: To develop the PF, the paper reviewed the biomedical literature for the major dose-response relations between health, physical fitness, and exercise. Where relevant, the paper converted the dose-response relationships from relative risks to absolute probabilities and standardized terminology and units of measures. RESULTS: The paper develops a clear set of biological PF that illustrate, quantitatively, how increases in peak cardiorespiratory (CR) fitness as measured by a short stress test reduce the probability of all-cause mortality; how increasing intensities of short (approximately 30 min, three to five times a week) exercise sessions increase peak CR fitness or retard its age-related decline; and how consistent exercise reduces the risk of myocardial infarctions (MI). CONCLUSIONS: The exercise-long-run health PF developed in this paper should provide a useful framework for other studies to estimate the broadly defined costs and benefits of different exercise programs and to help develop optimal ones.  相似文献   

15.
Physical fitness, injuries, and team performance in soccer   总被引:6,自引:0,他引:6  
PURPOSE: To investigate the relationship between physical fitness and team success in soccer, and to test for differences in physical fitness between different player positions. METHODS: Participants were 306 male soccer players from 17 teams in the two highest divisions in Iceland. Just before the start of the 1999 soccer season, the following variables were tested: height and weight, body composition, flexibility, leg extension power, jump height, and peak O2 uptake. Injuries and player participation in matches and training were recorded through the 4-month competitive season. Team average physical fitness was compared with team success (final league standing) using a linear regression model. Physical fitness was also compared between players in different playing positions. RESULTS: A significant relationship was found between team average jump height (countermovement jump and standing jump) and team success (P = 0.009 and P = 0.012, respectively). The same trend was also found for leg extension power (P = 0.097), body composition (% body fat, P = 0.07), and the total number of injury days per team (P = 0.09). Goalkeepers demonstrated different fitness characteristics from outfield players. They were taller and heavier, more flexible in hip extension and knee flexion, and had higher leg extension power and a lower peak O2 uptake. However, only minor differences were observed between defenders, midfield players, and attackers. CONCLUSION: Coaches and medical support teams should pay more attention to jump and power training, as well as preventive measures and adequate rehabilitation of previous injuries to increase team success.  相似文献   

16.
OBJECTIVE: Evaluate the physical fitness and training of Norwegian infantry soldiers during 10 months of compulsory military service. METHODS: Maximal oxygen uptake (VO2max) and maximal numbers of sit-ups, push-ups, and chin-ups and 3-km running time were tested in 107 male infantry soldiers at the beginning and end of basic training (BT), and again at demobilization. The amount of physical training was registered throughout the military service. RESULTS: During BT, major improvements in sit-ups and push-ups were found. VO2max increased in soldiers with the lowest initial VO2max, but decreased to pre-BT level at demobilization. The amount of obligatory physical training was 8.5 hours x week(-1) during BT and 35% lower after BT, and was usually performed in uniform at low to moderate intensity. CONCLUSION: The amount of high-intensity endurance and strength training during compulsory military service is to low to improve the soldiers' endurance and muscular strength.  相似文献   

17.
Stretch-shortening cycle (SSC), which is a normal contraction behavior of muscle, was used as a model to investigate muscular fatigue. Nine male volunteers were subjected to 100 repeated and exhaustive SSC contractions of the forearm extensors using a special sledge apparatus incorporating a force plate system. The fatigue contractions were performed on submaximal levels but the before-after comparison also included maximal drop-jump condition on the sledge as well as falls on to the floor. The results indicated that in the 100 submaximal SSCs the fatigue was characterized by increases in the contact times for both the eccentric and concentric phases of SSC, but the influence was more pronounced on the concentric part. The force-time curves during contact on the platform were influenced by fatigue so that the initial force peak became higher and the subsequent initial drop of force more pronounced. During submaximal and maximal drops, the angular velocities changed in the two phases of SSC. With progressing fatigue, the eccentric maximal angular velocity increased and the corresponding concentric velocities decreased. These changes were accompanied by slight changes in the elbow joint mechanism with respect to the contact, release, and maximal flexion angles. The results suggest that repeated SSC induces fatigue and the fatigue effects on the mechanical behavior of the muscle are very much similar to those induced by either isometric or concentric fatigue contractions. However, the transfer of the energy between eccentric and concentric phases was drastically reduced and this implies that SSCs can be used effectively to examine the fatiguability of the system regulating muscle stiffness during exercise.  相似文献   

18.
Physical fitness (PF) is a construct of health‐ and skill‐related attributes which have been associated with academic performance (AP) in youth. This study aimed to review the scientific evidence on the association among components of PF and AP in children and adolescents. A systematic review of articles using databases PubMed/Medline, ERIC, LILACS, SciELO, and Web of Science was undertaken. Cross‐sectional and longitudinal studies examining the association between at least one component of PF and AP in children and adolescents, published between 1990 and June 2016, were included. Independent extraction of articles was carried out by the two authors using predefined data fields. From a total of 45 studies included, 25 report a positive association between components of PF with AP and 20 describe a single association between cardiorespiratory fitness (CRF) and AP. According to the Strengthening the Reporting of Observational Studies in Epidemiology guidelines: 12 were classified as low, 32 as medium risk, and 1 as high risk of bias. Thirty‐one studies reported a positive association between AP and CRF, six studies with muscular strength, three studies with flexibility, and seven studies reported a positive association between clustered of PF components and AP. The magnitude of the associations is weak to moderate (β = 0.10–0.42 and odds = 1.01–4.14). There is strong evidence for a positive association between CRF and cluster of PF with AP in cross‐sectional studies; and evidence from longitudinal studies for a positive association between cluster of PF and AP; the relationship between muscular strength and flexibility with AP remains uncertain.  相似文献   

19.
Anthropometric and fitness observations were made on 32 members of a top level Gaelic football squad that reached the All Ireland final in the year in which these measurements were taken. The subjects were found to be large and well muscled with a mean somatotype of 2.6:5.6:3.1 (endomorphy:mesomorphy:ectomorphy). Body fat content of the whole squad averaged 15.0% but the most successful group of players averaged 12.4%. The body mass index (BMI) of the group was high and averaged 24.7 km.m-2. This group of Gaelic footballers was found to be taller and heavier than top level soccer players but smaller than Australian rules and American footballers. At 58.6 ml.min-1.kg-1 maximum oxygen uptake (VO2max) was higher than that reported for rugby players and American footballers and is probably similar to that of professional soccer players. Scores on three lung function tests: (1) forced vital capacity (FVC), (2) forced expiratory volume during 1 s (FEV1), and (3) peak expiratory flow rate (PEFR) were between 112% and 115% of the values predicted from height and age. There were wide variations in flexibility among the members of the group, the best individuals being as flexible as elite track and field athletes while the worst were less flexible than untrained subjects. Vertical jump scores were high and averaged 503 mm. The fitness observations made on this group of elite Gaelic footballers showed that they were not only fitter but more homogeneously fit than rugby players and American footballers and their fitness was generally similar to that reported for professional soccer players.  相似文献   

20.
Physical demands and physiological responses during elite field hockey   总被引:1,自引:0,他引:1  
The aim of this study was to determine the physical demands of elite men's field hockey using modern time-motion analysis techniques. 18 elite male players (age: 24.4 ± 4.5 yrs) participated in 5 matches, during which physical outputs of players were quantified using GPS units and heart rate monitors. The mean total distance covered by each individual player was 6798 ± 2009 m. Mean total distance covered per position for 70 min (position (70)) was 8160 ± 428 m. Distance covered per position (70) decreased by 4.8% between the 1 (st )and 2 (nd) halves ( P < 0.05). Fullbacks covered significantly less total distance than all other positions ( P < 0.05). High-intensity running (>19 km.h (-1)) comprised 6.1% (479 ± 108 m) of the total distance covered and involved 34 ± 12 sprints per player, with an average duration of 3.3 s. Average HR was higher in the 1 (st) half (86.7% HR (max)) than the 2 (nd) half, (84.4% HR (max)), though this was not significant ( P = 0.06). The results suggest that modern day elite field hockey is a physically demanding team sport. Quantification of the demands and outputs of players at this level provides a useful framework on which to develop conditioning practices. The difference in physical outputs observed for some positions suggests position-specific conditioning is required at the elite level.  相似文献   

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