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Carbohydrate (CHO) metabolism is crucial for short-duration, high-intensity exercise performance, but the effects of variations in glycogen availability have not been investigated in field trials of trained athletes. This study was designed to test how 1500 m time trial (TT) performance is affected by the manipulation of pre-race glycogen reserves. Competitive middle-distance runners (n = 11 (4 females)) completed a 1500 m individually paced indoor TT after abundant (high, >5 g/kg/d) or restricted (low, <1.5 g/kg/d) dietary CHO intake for 2 days after a glycogen-depleting session. Stride pattern, heart rate (HR), capillary blood lactate, and glucose and plasma malondialdehyde (MDA) response were determined. The TT was slower in low vs. high condition by 4.5 (4.5) s (~2%; p < 0.01), with a tendency toward shorter stride length. Blood lactate and glucose were lower before the TT in low vs. high condition (1.8 (0.5) vs. 2.2 (0.7) mmol/L and 5.4 (0.7) vs. 5.9 (0.8) mmol/L, p = 0.022 and 0.007, respectively), and peak lactate was higher in high vs. low condition (16.8 (3.1) vs. 14.5 (4.2) mmol/L, p = 0.039). Plasma MDA was the same before the TT, and 15 min after the TT, it increased similarly by 15% in low (p = 0.032) and high (p = 0.005) conditions. The restriction of pre-test CHO intake impaired 1500 m TT performance and reduced baseline and peak blood lactate concentrations but not blood glucose or MDA response.

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PURPOSE: The aims of the present study were to investigate blood lactate kinetics following high intensity exercise and identify the physiological determinants of 800 m running performance. METHODS: Fourteen competitive 800 m runners performed two running tests. First, participants performed a multistage graded exercise test to determine physiological indicators related to endurance performance. Second, participants performed four to six 30-s high intensity running bouts to determine post-exercise blood lactate kinetics. Using a biexponential time function, lactate exchange ability (γ1), lactate removal ability (γ2), and the quantity of lactate accumulated (QLaA) were calculated from individual blood lactate recovery data. RESULTS: 800 m running performance was significantly correlated with peak oxygen consumption (r = -0.794), γ1 and γ2 at 800 m race pace (r = -0.604 and -0.845, respectively), and QLaA at maximal running speed (r = -0.657). V ˙ O2peak and γ2 at 800 m race pace explained 83% of the variance in 800 m running performance. CONCLUSION: Our results indicate that (1) a high capacity to exchange and remove lactate, (2) a high capacity for short-term lactate accumulation and, (3) peak oxygen consumption, are critical elements of 800 m running performance. Accordingly, while lactate has primarily been utilized as a performance indicator for long-distance running, post-exercise lactate kinetics may also prove valuable as a performance determinant in middle-distance running.

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PURPOSE: Monitoring performance athletes' training responses can be efficiently completed at competitive events. This study aimed to explore the changes in swimming, countermovement-jump (CMJ), and pull-up (PU) performance following training across a competitive phase, as well as immediately before and after each race. METHODS: Fourteen well-trained male sprint/middle-distance swimmers (height 179 [7] cm, mass 70 [8] kg, age 18 [2] y), from 3 regional training groups, completed CMJ and PU tests before and after the national competitions in October and May, when race performance was also assessed. RESULTS: Swimming race performance was significantly improved from before the national competitions in October to after the national competitions in May (1.8% [3.2%], P = .044, d = 0.60, moderate effect). Although there were no significant changes in PU velocity, CMJ performance significantly improved from before the national competitions in October to after the national competitions in May (mean difference 2.29 cm, P = .004, d = 3.52) and showed before-to-after race decreases (mean difference -1.64 cm, P = .04, d = 2.28). CONCLUSION: Swimming performance and CMJ performance improved as the season progressed, although these improvements were not directly correlated. PU performance did not appear to be sensitive to training or race-induced fatigue, in contrast to CMJ, in this group of male swimmers.

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Introduction: Modifications in asymmetry in response to self-paced efforts have not been thoroughly documented, particularly regarding horizontally-derived ground reaction force variables. We determined the magnitude and range of gait asymmetries during 800 m track running. Methods: Eighteen physical education students completed an 800 m self-paced run on a 200 m indoor track. During the run, vertical and horizontal ground reaction forces were measured at a sampling frequency of 500 Hz using a 5 m-long force platform system, with data collected once per lap. The following mechanical variables were determined for two consecutive steps: contact time and duration of braking/push-off phases along with vertical/braking/push-off peak forces and impulses. The group mean asymmetry scores were evaluated using the "symmetry angle" (SA) formula, where scores of 0% and 100% correspond to perfect symmetry and perfect asymmetry, respectively. Results: There was no influence of distance interval on SA scores for any of the nine biomechanical variables (P ≥ 0.095). The SA scores were ∼1%-2% for contact time (1.3 ± 0.5%), peak vertical forces (1.8 ± 0.9%), and vertical impulse (1.7 ± 1.0%). The SA scores were ∼3%-8% for duration of braking (3.6 ± 1.1%) and push-off (3.2 ± 1.4%) phases, peak braking (5.0 ± 2.1%) and push-off (6.9 ± 3.1%) forces as well as braking (7.6 ± 2.3%) and push-off (7.7 ± 3.3%) impulses. The running velocity progressively decreased at 300 m and 500 m compared to that at 100 m but levelled off at 700 m (P < 0.001). Discussion: There were no modifications in gait asymmetries, as measured at 200-m distance intervals during 800-m track running in physical education students. The 800 m self-paced run did not impose greater mechanical constraints on one side of the body. Experimental procedures for characterizing the gait pattern during 800 m track running could be simplified by collecting leg mechanical data from only one side.

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Swimming performance achieved in 50-m, 100-m and 200-m events in each swimming stroke can have an influence on the final performance in individual medley (IM) events. We attempted to quantify the relative contributions of performance in individual stroke events to top-10 world ranked IM competition performance. We examined competition results of top-10 world ranked IM swimmers (90 males and 90 females) between 2012 and 2018. A general linear model was developed to examine association between the 200-m and 400-mIM and predictor variables of competition performance in other 50-m, 100-m, and 200-m events. The main predictor variable for 200-mIM medalist status was having scored more than 900 FINA points in at least one 100-m event. Scoring more than 800 FINA points in at least two 200-mIM events, and more than 900 FINA points in at least one 100-m event, was important for success in the 400-mIM. Top-10 world ranked 200-mIM and 400-mIM swimmers require a world class standard in one or more individual stroke event(s).

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BACKGROUND: Middle-distance running events have special physiological requirements from a training and competition point of view. Therefore, many athletes choose to take sport supplements (SS) for different reasons. To date, few studies have been carried out that review supplementation patterns in middle-distance running. The aim of the present study is to analyze the consumption of SS in these runners with respect to their level of competition, sex and level of scientific evidence. METHODS: In this descriptive cross-sectional study, data was collected from 106 middle-distance runners using a validated questionnaire. RESULTS: Of the total sample, 85.85% responded that they consumed SS; no statistical difference was found regarding the level of competition or sex of the athletes. With respect to the level of competition, differences were observed in the total consumption of SS (p = 0.012), as well as in that of medical supplements (p = 0.005). Differences were observed between sexes in the consumption of medical supplements (p = 0.002) and group C supplements (p = 0.029). CONCLUSIONS: Higher-level athletes consume SS that have greater scientific evidence. On the other hand, although the most commonly consumed SS have evidence for the performance or health of middle-distance runners, runners should improve both their sources of information and their places of purchase.

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We purpose to determine the nationality of the European middle-distance athletes under 18 years (U18) and under 20 years (U20) during the last decade, to verify the participation trend for each country, and to assess whether the place of competition can be associated with the athletes ranking position. The sample comprised 902 European male runners, ranked among the best finishers from 2009 to 2020. The athletes were divided into two categories (nU18 â€‹= â€‹266; and nU20 â€‹= â€‹636) of two distances (n1 500 â€‹m â€‹= â€‹397; n3 000 â€‹m â€‹= â€‹505). The Mantel test was used for participation trend and the Chi-square test (χ2) was used to verify differences between the ranking position and the place of competition. For both distances, the highest number of athletes were from Spain (n = 127), followed by Turkey (n = 62) and Great Britain (n = 50). No significant trends were shown for most of the countries, in both distances. A positive trend was shown for Slovenia (i.e., 3000 â€‹m) over the years. A non-significant association was verified between the countries and the ranking position, as non-significant differences were proved for the place of competition. This information may be useful to guide athlete development programs in each country.

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Several studies have investigated biomechanical and energetic parameters in competitive swimming. Among these studies, it is possible to identify the 400-m front crawl as a useful test to assess these parameters. The present study provided a meta-analysis assessing representative variables for the kinematic, arm-stroke efficiency, coordination, and energetic parameters of the 400-m front crawl test. PubMed, Embase, Web of Science, and SPORTDiscus were the databases used to select the studies published between January 1970 and December 2022. Forty studies (n = 651 swimmers) were selected according to the eligibility and inclusion criteria. The variables chosen to represent each parameter were: clean swim speed (kinematics); index of coordination (coordination); arm-stroke efficiency (efficiency); and oxygen consumption (energetic). Swimming speed was moderate (1.34 m s-1) compared to the world's records performers. Thus, this speed contributed for the swimmers in remaining at high efficiency (35%), imposing a capture coordination model (index of coordination: -11%) with high oxygen consumption (58.8 ml·kg-1 min-1). High heterogeneity (>75%) was found among the outcome parameters in the studies. The different average speeds that represented the kinematic parameters seem to be the most responsible and influential in the arm-stroke efficiency, coordination, and energetic parameters for high 400-m freestyle (front crawl) performance. This meta-analysis can help researchers, coaches, and swimmers improving competitive performance, and developing further research in the sports sciences area, specifically in the swimming.

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The torso muscles play important roles in longitudinal rotation between the upper and lower torso on land but demands on these muscles at different swimming speeds and their role in torso twist in front crawl remains unclear. We aimed to compare torso muscle activity at different front crawl speeds and to assess the relationships between torso muscle activity and torso twist. Three-dimensional kinematics and torso muscle EMG data were collected from 15 male swimmers during middle-distance and sprint front crawl. Internal oblique, external oblique, and rectus abdominis, but not erector spinae, activities were greater at sprint than middle-distance pace. Sprint swimmers are likely to benefit from focusing training on the abdominal muscles. Cross-correlation peak coefficients between muscle activity and torso twist occurred with 517-775 and 400-600 ms lag at middle-distance and sprint paces (respectively). These lags are beyond the torso muscle electromechanical delay (~220 ms) and are too long for these muscles to produce movement changes. Further, peak coefficients coincided with both positive and negative shifts, indicating that muscle activity did not always precede kinematic changes. The torso muscles are therefore likely to play a greater role in maintaining stability and controlling posture in front crawl than producing torso twist.

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RESUMEN Introducción: La composición corporal es un indicador fundamental para definir el estado nutricional del corredor. Objetivo: El estudio tuvo como objetivo evaluar los efectos de la intervención de periodización nutricional en la composición corporal de corredores juveniles djiboutianos de élite en distancia media. Materiales y métodos: La muestra fue de 22 corredores masculinos, en edades comprendidas entre 16 y 18 años. Para la valoración, se diseñó un experimento constituido por 11 sujetos en el grupo control y 11 en el experimental. Como mediciones antropométricas se tomaron el peso, estatura y seis panículos adiposos para evaluar el porcentaje de grasa, índices de adiposidad, índice de masa corporal y el de sustancia corporal activa pues, para llevar el seguimiento de la intervención propuesta, se realizó una entrevista de recordatorio 24 horas de siete días. Resultados: Se diseñó una dieta periodizada, con la manipulación de los carbohidratos. La periodización nutricional con alta y baja ingesta de carbohidratos durante 12 semanas disminuyó significativamente (p< 0,05) el porcentaje de grasa, sin alterar el peso corporal ni el índice de sustancia corporal activa en los corredores djiboutianos de media distancia juveniles del grupo experimental. Conclusiones: Los resultados expuestos contribuyen a mejorar el control biomédico del entrenamiento en los corredores de élite juveniles de distancia media en Djibouti, ya que existían limitaciones de datos sobre su composición corporal y el efecto que pudiera tener la nutrición periodizada sobre esos indicadores

SÍNTESE Introdução: A composição corporal é um indicador chave na definição do estado nutricional do corredor. Objetivo: O estudo visava avaliar os efeitos da intervenção de periodização nutricional sobre a composição corporal em corredores de elite júnior djibutianos de meia distância. Materiais e métodos: A amostra consistiu de 22 corredores masculinos, de 16-18 anos de idade. Para a avaliação, foi projetado um experimento com 11 sujeitos no grupo de controle e 11 no grupo experimental. Como medidas antropométricas, foram tomadas medidas de peso, altura e seis panniculi adiposos para avaliar a porcentagem de gordura, índices de adiposidade, índice de massa corporal e índice de substância corporal ativa. Para acompanhar a intervenção proposta, foi realizada uma entrevista de lembrete de sete dias, 24 horas por dia. Resultados: Foi projetada uma dieta periódica, com a manipulação de carboidratos. A periodização nutricional com alta e baixa ingestão de carboidratos por 12 semanas diminuiu significativamente (p<0,05) o percentual de gordura, sem alterar o peso corporal ou o índice de substância corporal ativa em corredores djibutianos juvenis de meia distância no grupo experimental. Conclusões: Os resultados acima contribuem para melhorar o monitoramento biomédico do treinamento em corredores de elite de distância média júnior em Djibuti, já que havia limitações de dados sobre sua composição corporal e o efeito que a nutrição periodizada poderia ter sobre esses indicadores.

ABSTRACT Introduction: Body composition is a fundamental indicator to define the nutritional status of the runner. Objective: The study aimed to evaluate the effects of the nutritional periodization intervention on the body composition of elite junior Djiboutian runners in middle distance. Materials and methods: The sample consisted of 22 male runners, aged between 16 and 18 years. For the assessment, an experiment consisting of 11 subjects in the control group and 11 in the experimental roup was designed. As anthropometric measurements, weight, height and six adipose tissue were taken to evaluate the percentage of fat, adiposity index, body mass index and active body substance index, since, in order to monitor the proposed intervention, an interview of reminder 24 hours seven days. Results: A periodized diet was designed, with the manipulation of carbohydrates. Nutritional periodization with high and low carbohydrate intake for 12 weeks significantly (p<0.05) decreased percentage fat without altering body weight or active body substance index in juvenile middle-distance Djiboutian runners from the experimental group. Conclusions: The exposed results contribute to improve the biomedical control of training in elite junior middle-distance runners in Djibouti, since there were data limitations on their body composition and the effect that periodized nutrition could have on these indicators.

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When will women run a sub-4-minute mile? The answer seems to be a distant future given how women's progress has plateaued in the mile, or its better studied metric placeholder, the 1500 m. When commonly accepted energetics principles of running, along with useful field validation equations of the same, are applied to probe the physiology underpinning the 10 all-time best women's mile performances, insights gained may help explain the present 12.34-second shortfall. Insights also afford estimates of how realistic improvements in the metabolic cost of running could shrink the difference and bring the women's world record closer to the fabled 4-minute mark. As with men in the early 1950s, this might stir greater interest, excitement, participation, and depth in the women's mile, the present absence of which likely contributes to more pessimistic mathematical modeling forecasts. The purpose of this invited commentary is to provide a succinct, theoretical, but intuitive explanation for how women might get closer to their own watershed moment in the mile.

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[This corrects the article DOI: 10.3389/fspor.2021.634258.].

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We examined the degree to which 200-m and 400-m Individual Medley (IM) performance was related to sprint-, middle- and long-distance events before a swimmer reached a Top-20 world ranking. A retrospective longitudinal modelling study was conducted. Data on Top-20 swimmers between 2010 and 2018 were obtained from publicly available websites. A general linear model was used to examine associations between 200-m and 400-mIM performance (FINA ranking points) and performance in sprint, middle-distance and distance events in the previous two years. In the 200-mIM, there were significant associations (p < 0.001) between prior competition results obtained for both the 200-mIM (r = 0.80; ß = 0.543) and 400-m IM (r = 0.70; ß = 0.317) events before the Top-20 performance in 200-mIM in the year of the Top-20. Sprint distance events were associated (p < 0.006; r = 0.39; ß = 0.088) with 200-mIM (t). Each additional 10 FINA points in the 200-mIM in each of the two years preceding the Top-20 performance. were associated with an increase of 5 FINA points in 200-mIM in in the year of the Top-20 (goodness of fit R 2 = 0.70). There were similar associations (p < 0.001) for a Top 20-FINA 400-mIM performance with both 200-mIM (r = 0.72; ß = 0.385) and 400-m IM (r = 0.79; ß = 0.492) events in the two years before a swimmer reached the Top-20. Middle-distance events were associated with 400-mIM performance (p < 0.001; r = 0.53; ß = 0.163). Each additional 10 FINA points in 400-mIM in in each of the two years preceding the Top-20 performance were associated with an increase of 5 FINA points in in the year that a swimmer reached the Top-20 (goodness of fit R 2 = 0.75). The specificity and complexity of the IM require a thorough preparation in this event for world-class performances. The 200-mIM is more closely related to sprint distance events, whereas middle-distance events support preparations for the 400-mIM.

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This study aimed to compare sprint, jump performance, and sprint mechanical variables between endurance-adapted milers (EAM, specialized in 1500-3000-m) and speed-adapted milers (SAM, specialized in 800-1500 m) and to examine the relationships between maximal sprint speed (MSS), anaerobic speed reserve (ASR), sprint, jump performance, and sprint mechanical characteristics of elite middle-distance runners. Fifteen participants (8 EAM; 7 SAM) were evaluated to obtain their maximal aerobic speed, sprint mechanical characteristics (force-velocity profile and kinematic variables), jump, and sprint performance. SAM displayed greater MSS, ASR, horizontal jump, sprint performance, and mechanical ability than EAM (p < 0.05). SAM also showed higher stiffness in the 40-m sprint (p = 0.026) and a higher ratio of horizontal-to-resultant force (RF) at 10 m (p = 0.003) and RFpeak (p = 0.024). MSS and ASR correlated with horizontal (r = 0.76) and vertical (r = 0.64) jumps, all sprint split times (r ≤ -0.85), stiffness (r = 0.86), and mechanical characteristics (r ≥ 0.56) during the 100-m sprint, and physical qualities during acceleration (r ≥ 0.66) and sprint mechanical effectiveness from the force-velocity profile (r ≥ 0.69). Season-best times in the 800 m were significantly correlated with MSS (r = -0.86). Sprint ability has a crucial relevance in middle-distance runners' performance, especially for SAM.

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The aims of the current study were to compare the pacing patterns of all-time 800 m, 1500 m and mile running world records (WRs) and to determine whether differences exist between sexes, and if 800 m and 1500 m WRs were broken during championship or meet races. Overall and lap times for men and women's 800 m, 1500 m, and mile WRs from World Athletics were collected when available and subsequently compared. A fast initial 200 m segment and a decrease in speed throughout was found during 800 m WRs. Accordingly, the first 200 m and 400 m were faster than the last 200 m and 400 m, respectively (p < 0.001, 0.77 ≤ ES ≤ 1.86). The first 400 m and 409 m for 1500 m and mile WRs, respectively, were faster than the second lap (p < 0.001, 0.74 ≤ ES ≤ 1.46). The third 400 m lap was slower than the last 300 m lap and 400 m lap for 1500 m and mile WRs, respectively (p < 0.001, 0.48 ≤ ES ≤ 1.09). No relevant sex-based differences in pacing strategy were found in any event. However, the first 409 m lap was faster than the last 400 m lap for men but not for women during mile WRs. Women achieved a greater % of WRs than men during championships (80% vs. 45.83% in the 800 m, and 63.63% vs. 31.58% in the 1500 m, respectively). In conclusion, positive, reverse J-shaped and U-shaped pacing profiles were used to break 800 m, men's mile and 1500 m, and women's mile WRs, respectively. WRs are more prone to be broken during championships by women than men.

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The main aim was to investigate the impact of maximal aerobic speed (MAS), maximal anaerobic speed (MANS), and time to exhaustion (TTE) at 130% MAS, on 800-m running time performance (800TT). A second aim was to investigate the impact of anaerobic speed reserve (ASR), i.e., the relative difference between MAS and MANS, on TTE. A total of 22 healthy students classified as recreational runners participated in a cross-sectional study. They were tested for maximal oxygen consumption (VO2max), oxygen cost of running (CR), time performance at 100 m (100TT), time performance at 800 m (800TT), and TTE. MAS was calculated as VO2max × CR -1, and MANS was calculated as 100TT velocity. Both MAS and MANS correlated individually with 800TT (r = -0.74 and -0.67, respectively, p < 0.01), and the product of MAS and MANS correlated strongly (r = -0.82, p < 0.01) with 800TT. TTE did not correlate with 800TT. Both ASR and % MANS correlated strongly with TTE (r = 0.90 and -0.90, respectively, p < 0.01). These results showed that 800TT was first and foremost dependent on MAS and MANS, and with no impact from TTE. It seemed that TTE was merely a product of each runner's individual ASR. We suggest a simplified model of testing and training for 800TT, namely, by focusing on VO2max, CR, and short sprint velocity, i.e., MAS and MANS.

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PURPOSE: The present study aimed to compare the physiological responses of high-intensity race-pace continuous vs. interval workouts commonly used in middle-distance athletics, by means of analyzing post-exercise cardiac autonomic regulation and lactate. METHODS: Nineteen highly-trained 800-m male runners were asked to run a 600-m race-pace continuous workout and a 2 × 4 × 200-m interval training, counterbalanced and randomized within one week of difference. Blood lactate jointly with linear and nonlinear heart rate dynamics were assessed during the immediate 15-min recovery. Age-category (Under23-Senior vs. Juvenile-Junior) was considered as an inter-subject factor. RESULTS: Peak lactate was higher following the interval training (15.51 ± 0.99 vs 13.83 ± 1.77 mmol L-1; P < 0.05) whereas lactate removal was almost nonexistent 15 min after both workouts (between 0 and 16%). Vagal modulation (ln RMSSD and lnRMSSD to RR ratio) remained significantly depressed at the end of recovery following both workouts, although the alteration was larger following the interval training. Detrended Fluctuation Analysis evidenced a more random HR behavior (DFA1 closer to 0.5) during the first 9 min of recovery after the interval training, whereas no significant change was observed in heart rate complexity (SampEn). Neither were differences found in post-exercise lactate and HR dynamics as a function of age-category. CONCLUSIONS: High-intensity workouts commonly used in middle-distance athletics, both race-pace continuous and intervallic approaches, induce a large depression of vagal modulation in highly trained runners, although interval trainings appear to induce even a greater alteration of both linear and nonlinear HR dynamics and a higher post-exercise peak lactate.

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Fatigue with its underlying mechanisms and effects is a broadly discussed topic and an important phenomenon, particularly in endurance sports. Although several studies have already shown a variety of changes in running kinematics with fatigue, few of them have analyzed competitive runners and even fewer have focused on middle-distance running. Furthermore, the studies investigating fatigue-related changes have mostly reported the results in terms of discrete parameters [e.g., range of motion (RoM)] in the frontal or sagittal plane, and therefore potentially overlooked effects occurring in subphases of the gait cycle or in the transverse plane. On this basis, the goal of the present study was to analyze the effects of exhaustive middle-distance running on expert runners by means of both discrete parameters and time series analysis in 3D. In this study, 13 runners ran on a treadmill to voluntary exhaustion at their individually determined fatigue speeds which was held constant during the measurements. Kinematic data were collected by means of a 3D motion capture system. Spatiotemporal and stiffness parameters as well as the RoM of joints and of center of mass (CoM) within the stance and flight phases were calculated. Independent t-tests were performed to investigate any changes in means and coefficients of variation (CV) of these parameters between the rested (PRE) and fatigued (POST) state. Statistical parametric mapping method was applied on the time series data of the joints and the CoM. Results from this exploratory study revealed that during a middle-distance run, expert runners change their stance time, rather than their step frequency or step length in order to maintain the constant running speed as long as possible. Increased upper body movements occurred to counteract the increased angular moment of the lower body possibly due to longer stance times. These findings provide insights into adaptation strategies of expert runners during a fatiguing middle-distance run and may serve a valuable information particularly for comparisons with other group of runners (e.g., females or non-athletes) as well with other conditions (e.g., non-constant speed or interval training), and might be useful for the definition of training goals (e.g., functional core training).

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PURPOSE: To analyze the relationships between the evolution of training-load values and countermovement jump (CMJ) as an indicator of stress and fatigue in a high-level 800-m runner during a whole season, including indoor (ID) and outdoor season (OD). METHODS: Over 42 weeks, daily training load was quantified as the result of the product of the intensity and volume, and it was termed load index (LI). CMJ was measured in every running session after warm-up and immediately after the last effort of the session. Other jump-related variables such as CMJ height loss, average weekly CMJ, initial CMJ of the next consecutive session, and initial CMJ of the following week were studied. RESULTS: A significant negative relationship was observed between LI and weekly CMJ (ID: r = -.68, P < .001, common variance [CV] = 46%; OD: r = -.73, P < .001, CV = 53%), initial CMJ of the following week (OD: r = -.71, P < .01, CV = 50%), and CMJ height loss (ID: r = -.58, P < .01, CV = 34%; OD: r = -.52, P < .01, CV = 27%). A significant positive relationship was observed between LI and initial CMJ of the next consecutive session when LI values were <8 (OD: r = .72; P < .01, CV = 52%). However, from values ≥8, the relationship turned into a significant negative one (ID: r = -.74; P < .01, CV = 55%; OD: r = -64, P < .01, CV = 41%). CONCLUSIONS: CMJ may be a valid indicator of the degree of stress or fatigue generated by specific training sessions of a competitive athlete within a single session, a week, or even the following week. There could be an individual limit LI value from which the training volume does not allow a positive effect on high-speed actions such as a CMJ in the next consecutive session.

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The aim was to determine the pacing strategies used to achieve male 1500 m running world record performances. Lap times (three first laps and the last 300 m) for the last 37 male 1500 m world record performances achieved since 1917 until 1998 were collected. An analysis of variance with repeated measures and a Bonferroni post hoc test were conducted to determine differences between the percentages of race average speed at each lap. Lap 1 and last 300 m differed from lap 2 and 3, being the latter slower (P < 0.001, 1.44 ≤ ES ≤ 1.95), and displaying a U-shaped pacing profile. Whereas the pacing strategies observed differed from those previously determined for major championship races, a fast endspurt was always present and therefore athletes aiming for a world standard performance should train for developing their anaerobic capacity in addition to a high aerobic power.

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