Demographic characteristics of elite Kenyan endurance runners

Kenyan athletes have dominated international distance running in recent years. Explanations for their success include favourable physiological characteristics, which could include favourable genetic endowment, and advantageous environmental conditions. The aim of this study was to compare the demographic characteristics of elite Kenyan runners with those of the general Kenyan population. Questionnaires, administered to 404 elite Kenyan runners specializing in distances ranging from the 800 m to the marathon and 87 Kenyan controls, obtained information on place of birth, language, and distance and method of travel to school. Athletes were separated into two groups according to athletic success: those who competed in international competition and those who competed in national competition. The athletes differed from controls in regional distribution, language, and distance and method of travel to school; athletes also differed from each other with the exception of method of travel to school. Most national and international athletes came from the Rift Valley province (controls 20%, national athletes 65%, international athletes 81%), belonged to the Kalenjin ethnic group (controls 8%, national athletes 49%, international athletes 76%) and Nandi sub-tribe (controls 5%, national athletes 25%, international athletes 44%), and spoke languages of Nilotic origin (controls 21%, national athletes 60%, international athletes 79%). A higher proportion of all athletes ran to school each day (controls 22%, national athletes 73%, international athletes 81%) and covered greater distances. In conclusion, Kenyan runners are from a distinctive environmental background in terms of geographical distribution, ethnicity and travelled further to school, mostly by running. These findings highlight the importance of environmental and social factors in the success of Kenyan runners.     

Tapering strategies in elite British endurance runners

Abstract

The aim of the study was to explore pre-competition training practices of elite endurance runners. Training details from elite British middle distance (MD; 800 m and 1500 m), long distance (LD; 3000 m steeplechase to 10,000 m) and marathon (MAR) runners were collected by survey for 7 days in a regular training (RT) phase and throughout a pre-competition taper. Taper duration was [median (interquartile range)] 6 (3) days in MD, 6 (1) days in LD and 14 (8) days in MAR runners. Continuous running volume was reduced to 70 (16)%, 71 (24)% and 53 (12)% of regular levels in MD, LD and MAR runners, respectively (P < 0.05). Interval running volume was reduced compared to regular training (MD; 53 (45)%, LD; 67 (23)%, MAR; 64 (34)%, P < 0.05). During tapering, the peak interval training intensity was above race speed in LD and MAR runners (112 (27)% and 114 (3)%, respectively, P < 0.05), but not different in MD (100 (2)%). Higher weekly continuous running volume and frequency in RT were associated with greater corresponding reductions during the taper (R = ?0.70 and R = ?0.63, respectively, both P < 0.05). Running intensity during RT was positively associated with taper running intensity (continuous intensity; R = 0.97 and interval intensity; R = 0.81, both P < 0.05). Algorithms were generated to predict and potentially prescribe taper content based on the RT of elite runners. In conclusion, training undertaken prior to the taper in elite endurance runners is predictive of the tapering strategy implemented before competition.     

Bone health in elite Kenyan runners

Impact loading in athletes participating in various sports has been positively associated with increased bone mineral density (BMD), but this has not been investigated in elite Kenyan runners. Body composition and site-specific BMD measures quantified with dual x-ray absorptiometry were measured in 15 elite male Kenyan runners and 23 apparently healthy South African males of different ethnicities. Training load and biomechanical variables associated with impact loading, such as joint stiffness, were determined in the elite Kenyan runners. Greater proximal femur (PF) BMD (g · cm^?2) was higher (P = 0.001, ES = 1.24) in the elite Kenyan runners compared with the controls. Six of the 15 (40%) Kenyan runners exhibited lumbar spine (LS) Z-Scores below ?2.0 SD, whereas this was not found in the apparently healthy controls. PFBMD was associated with training load (r = 0.560, P = 0.003) and ankle (r = 0.710, P = 0.004) and knee (r = 0.546, P = 0.043) joint stiffness. Elite Kenyan runners exhibit greater PFBMD than healthy controls, which is associated with higher training load and higher joint stiffness. Our results reaffirm the benefits of impact loading on BMD at a weight-bearing site, while a high prevalence of low LSBMD in the elite Kenyan runners is hypothesised to be the result of a mismatch between energy intake and high training load. Future research investigating energy availability in Kenyan runners and the possible association with musculoskeletal injury should be investigated.     

优秀散打运动员专项耐力及训练研究

加强优秀散打运动员专项耐力训练方面的研究是进一步提高散打竞技水平的重要途径之一。通过对部分优秀散打运动员专项耐力调查分析、根据散打运动专项耐力特点,提出散打运动专项耐力训练方法的几点建议,即针对不同队员制订不同的训练方法、合理安排运动负荷、遵循专项训练深化原则和训练形式多样化。     

Resting MAPK expression in chronically trained endurance runners

Purpose: There is a paucity of research investigating the expression of mitogen-activated protein kinases (MAPK) in chronically trained (CT) athletes. Thus, it is unclear how MAPK may contribute to performance and muscle adaptation in CT subjects. The purpose of this study was to determine MAPK total protein, and phosphorylated expression of extracellular signal-regulated kinases 1 and 2 (ERK1/2), c-Jun N-terminal kinase (JNK), and p38-MAPK (p38) between untrained, and chronically trained runners. Methods: Tissue samples were analysed from sedentary (SED; n?=?5) controls and chronically trained runners (CT; n?=?5). Resting muscle biopsy samples were analysed for total-MAPK – and ratio of phosphorylated/total (p-MAPK) – ERK1/2, JNK, and p38-MAPK via western blotting. Mann–Whitney U tests and effect sizes were utilized to determine differences in total MAPK protein content and phosphorylation status between SED and CT subjects. Results: There was no difference in total-MAPK expression between SED and CT (p?>?.05). p-p38-MAPK tended to be greater for CT compared to SED (p?=?.07). There were moderate effect sizes of decreased pERK/total-ERK (d?=??0.69) and increased pJNK/total-JNK (d?=?0.54) in CT compared to SED. There was a positive correlation between p-p38-MAPK/total-MAPK and the percentage of type I fibres (r?=?0.73, p?=?.016). Conclusion: Contrary to previous studies, chronic endurance training does not greatly influence total MAPK protein expression in chronically trained runners. However, resting phosphorylation of p38-MAPK may contribute to enhanced oxidative metabolism at chronically trained levels. These alterations are likely involved in the different physiological adaptations that occur following long-term training or at highly competitive levels.     

Dissociation between running economy and running performance in elite Kenyan distance runners

The purpose of this study was to investigate the relationship between running economy (RE) and performance in a homogenous group of competitive Kenyan distance runners. Maximal aerobic capacity (VO_2max) (68.8 ± 3.8 ml?kg^?1?min^?1) was determined on a motorised treadmill in 32 Kenyan (25.3 ± 5.0 years; IAAF performance score: 993 ± 77 p) distance runners. Leg anthropometry was assessed and moment arm of the Achilles tendon determined. While Achilles moment arm was associated with better RE (r² = 0.30, P = 0.003) and upper leg length, total leg length and total leg length to body height ratio were correlated with running performance (r = 0.42, P = 0.025; r = 0.40, P = 0.030 and r = 0.38, P = 0.043, respectively), RE and maximal time on treadmill (t_max) were not associated with running performance (r = ?0.01, P = 0.965; r = 0.27; P = 0.189, respectively) in competitive Kenyan distance runners. The dissociation between RE and running performance in this homogenous group of runners would suggest that RE can be compensated by other factors to maintain high performance levels and is in line with the idea that RE is only one of many factors explaining elite running performance.     

浅谈400米运动员的速度耐力训练

运用文献资料法和数据统计分析法,对我国部分优秀运动员400米的速度耐力训练进行研究。研究认为,在400米跑这一径赛项目中,发展速度与发展速度耐力是提高该项目成绩的两大关键,也是训练实践中要解决的核心问题。本文以运动生理学、运动生物化学为依据,结合运动训练理论与方法,对发展速度耐力这一问题进行分析,并提出了400米跑中发展速度耐力的有效方法和手段。     

Comment on Dissociation between running economy and running performance in elite Kenyan distance runners

Mooses and colleagues suggest that running economy alone does not explain superior distance running performance in elite Kenyan runners. Whilst we agree with the multi-factorial hypothesis for Kenyan running success, we do not believe that running economy can be overlooked to the extent that it was based on this particular study. Based on the methods used and the range of athletes tested, in this response letter we question whether this study provides any basis for downplaying the influence of running economy or suggesting that other factors compensate for it to enable superior performance.     

Effects of resistance training on performance in previously trained endurance runners: A systematic review

The aim of this work was to identify, synthesize and evaluate the results of randomized controlled trials examining the effects of resistance training on performance indicators in previously trained endurance runners. A database search was carried out in PubMed, Science Direct, OvidSPMedLine, Wiley, Web of Science, ProQuest and Google Scholar. In accordance with the PRISMA checklist, 18 published articles dated prior to May 2016 involving 321 endurance runners were reviewed using the PEDro scale. Resistance training led to general improvements in muscular strength, running economy, muscle power factors, and direct performance in distances between 1,500 and 10,000 m. Such improvements were not accompanied by a significant increase in body mass or signs of overtraining. However, improvements did not occur in all cases, suggesting that they might depend on the specific characteristics of the resistance training applied. Although current evidence supports the effectiveness of resistance training to improve performance in already trained endurance runners, the methodological inconsistencies identified suggest that the results should be interpreted with caution. Future studies ought to investigate the benefits of resistance training in endurance runners while considering the existence of possible differentiated effects based on the specific characteristics of the resistance training carried out.     

Different psychophysiological responses to a high-intensity repetition session performed alone or in a group by elite middle-distance runners

Abstract

Internal training load refers to the degree of disturbance in psychophysiological homeostasis provoked by a training session and has been traditionally measured through session-RPE, which is the product of the session Rate of Perceived Exertion (RPE) and the duration. External training load refers to the actual physical work completed, and depends on session volume, intensity, frequency and density. Drafting, which is achieved by running closely behind another runner has been demonstrated to reduce the energy cost of running at a fixed speed and to improve performance. Therefore, it is hypothesised that psychophysiological responses might reflect different levels of internal load if training is performed individually or collectively. 16 elite middle-distance runners performed two high-intensity training sessions consisting of 4 repetitions of 500?m separated by 3?min of passive recovery. Sessions were performed individually and collectively. Times for each repetition, RPE, core affect (valence and felt arousal) and blood lactate concentrations [BLa] were measured after each repetition. Main time effect was significant and increased across repetitions for [BLa] and RPE (p?<?0.001), and decreased for valence (p?=?0.001). Main group effect was significant and values were higher when training individually for [BLa] (p?=?0.003) and RPE (p?=?0.001), and lower for valence (p?=?0.001). No differential responses were found between conditions in terms of repeat time or felt arousal. Findings demonstrate that elite middle-distance athletes running collectively display lower levels of internal training load compared to running alone, despite external training load being similar.     

Muscle co-activation and its influence on running performance and risk of injury in elite Kenyan runners

The relationship between muscle co-activation and energy cost of transport and risk of injury (initial loading rate and joint stiffness) has not been jointly studied. Fourteen elite Kenyan male runners were tested at two speeds (12 and 20 km · h^?1), where oxygen consumption, kinematic, kinetic and electromyography were recorded. Electromyography of seven lower limb muscles was recorded. Pre-activation and ground contact of agonist:antagonist co-activation was determined. All muscles displayed higher activity during pre-activation except rectus femoris (RF). Conversely, no differences were found during ground contact except for higher biceps femoris (BF) at 20 km · h^?1. Knee stiffness was correlated to RF–BF co-activation during both pre-activation and ground contact at both running speeds. However, energy cost of transport was only positively correlated to the above-mentioned muscle pairs at 20 km · h^?1 (r = 0620, P = 0.032; r = 0.682, P = 0.015, respectively). These findings emphasise the influence of neuromuscular control and performance and its support to musculoskeletal system to optimise function and modulate risk of injury. Further, neuromuscular activity during terminal swing is also important and necessary to execute and maintain performance.     

Effect of resistance training regimens on treadmill running and neuromuscular performance in recreational endurance runners

Abstract

The purpose of this study was to assess the effects of heavy resistance, explosive resistance, and muscle endurance training on neuromuscular, endurance, and high-intensity running performance in recreational endurance runners. Twenty-seven male runners were divided into one of three groups: heavy resistance, explosive resistance or muscle endurance training. After 6 weeks of preparatory training, the groups underwent an 8-week resistance training programme as a supplement to endurance training. Before and after the 8-week training period, maximal strength (one-repetition maximum), electromyographic activity of the leg extensors, countermovement jump height, maximal speed in the maximal anaerobic running test, maximal endurance performance, maximal oxygen uptake ([Vdot]O_2max), and running economy were assessed. Maximal strength improved in the heavy (P = 0.034, effect size ES = 0.38) and explosive resistance training groups (P = 0.003, ES = 0.67) with increases in leg muscle activation (heavy: P = 0.032, ES = 0.38; explosive: P = 0.002, ES = 0.77). Only the heavy resistance training group improved maximal running speed in the maximal anaerobic running test (P = 0.012, ES = 0.52) and jump height (P = 0.006, ES = 0.59). Maximal endurance running performance was improved in all groups (heavy: P = 0.005, ES = 0.56; explosive: P = 0.034, ES = 0.39; muscle endurance: P = 0.001, ES = 0.94), with small though not statistically significant improvements in [Vdot]O_2max (heavy: ES = 0.08; explosive: ES = 0.29; muscle endurance: ES = 0.65) and running economy (ES in all groups < 0.08). All three modes of strength training used concurrently with endurance training were effective in improving treadmill running endurance performance. However, both heavy and explosive strength training were beneficial in improving neuromuscular characteristics, and heavy resistance training in particular contributed to improvements in high-intensity running characteristics. Thus, endurance runners should include heavy resistance training in their training programmes to enhance endurance performance, such as improving sprinting ability at the end of a race.     

Adolescent elite Kenyan runners are at risk for energy deficiency,menstrual dysfunction and disordered eating

Limited data are available on the female athlete triad (Triad) in athletes from minority groups. We explored subclinical and clinical Triad components amongst adolescent elite Kenyan athletes (n = 61) and non-athletes (n = 49). Participants completed demographic, health, sport and menstrual history questionnaires as well as a 5-day weighed dietary record and exercise log to calculate energy availability (EA). Ultrasound assessed calcaneus bone mineral density (BMD). Eating Disorder Inventory subscales and the Three-Factor Eating Questionnaire’s cognitive dietary restraint subscale measured disordered eating (DE). EA was lower in athletes than non-athletes (36.5 ± 4.5 vs. 39.5 ± 5.7 kcal ? kg FFM^?1 ? d^?1, P = 0.003). More athletes were identified with clinical low EA (17.9% vs. 2.2%, OR = 9.5, 95% CI 1.17–77, P = 0.021) and clinical menstrual dysfunction (32.7% vs. 18.3%, χ² = 7.1, P = 0.02). Subclinical (75.4% vs. 71.4%) and clinical DE (4.9% vs. 10.2%, P = 0.56) as well as BMD were similar between athletes and non-athletes. More athletes had two Triad components than non-athletes (8.9% vs. 0%, OR = 0.6, 95% CI 0.5–6.9, P = 0.05). Kenyan adolescent participants presented with one or more subclinical and/or clinical Triad component. It is essential that athletes and their entourage be educated on their energy needs including health and performance consequences of an energy deficiency.     

Differences in trunk and thigh muscle strength,endurance and thickness between elite sailors and non-sailors

Dinghy sailors lean their upper body over the windward side of the boat (‘hiking’) to keep the boat’s balance and maximise its speed. Sustaining the hiking position is essential for competitive performance and this study examined sport-specific differences of muscles relevant for hiking in elite sailors. Knee extensor muscle strength as well as trunk muscle strength, muscle endurance and muscle thickness were assessed in elite dinghy sailors (n = 15) and compared to matched, non-sailing controls (n = 15). Isometric extensor strength was significantly higher in sailors at 60° (+14%) but not at 20° knee flexion. Sailors showed significantly higher trunk flexor (but not extensor) strength under isometric (+18%) and eccentric (+11%) conditions, which was associated to greater muscle thickness (rectus abdominis +40%; external oblique +26%) and higher endurance for ventral (+66%) and lateral (+61%) muscle chains compared to non-sailors. Greater muscles thickness and the particular biomechanical requirements to maintain the hiking position may drive the increases in isometric and eccentric muscle strength as well as ventral and lateral trunk endurance. The current findings identified sport-specific muscle function differences and provide performance benchmarks for muscle strength and endurance in elite sailors.     

对奥运会田径耐力性项群成绩演变的研究

对历届奥运会田径耐力性项群比赛前三名成绩进行整理、统计,对其成绩发展过程及成绩的递进状况进行定量分析和描述,揭示了耐力性项群成绩发展变化特征.各单项成绩演变与训练法的出现是同步进行的,不同的训练方法给田径耐力性项群带来了不同的发展时期.男女各单项速度发展变化有各自特点,发展空间各有不同.     

论提升优秀游泳运动员运动寿命的策略

随着体育全球化的推进,各种体育赛事层出不穷。游泳是奥运会的重要比赛项目,奖牌多,影响力大。新形势下,世界泳坛百花争艳,各国选手都极具竞争力,而我国游冰运动员的运动寿命短暂,平均年龄低于国外选手,忽视了许多大器晚成的优秀运动员。因此,本文通过介绍“运动寿命”的定义,分析我国优秀游泳运动员的培养现状,讨论造成优秀游泳运动员运动寿命短暂的因素,寻找延长优秀游泳运动员运动寿命的策略。     

Pacing profiles and tactical behaviors of elite runners

The pacing behaviors used by elite athletes differ among individual sports, necessitating the study of sport-specific pacing profiles. Additionally, pacing behaviors adopted by elite runners differ depending on race distance. An “all-out” strategy, characterized by initial rapid acceleration and reduction in speed in the later stages, is observed during 100 m and 200 m events; 400 m runners also display positive pacing patterns, which is characterized by a reduction in speed throughout the race. Similarly, 800 m runners typically adopt a positive pacing strategy during paced “meet” races. However, during championship races, depending on the tactical approaches used by dominant athletes, pacing can be either positive or negative (characterized by an increase in speed throughout). A U-shaped pacing strategy (characterized by a faster start and end than during the middle part of the race) is evident during world record performances at meet races in 1500 m, 5000 m, and 10,000 m events. Although a parabolic J-shaped pacing profile (in which the start is faster than the middle part of the race but is slower than the endspurt) can be observed during championship 1500 m races, a negative pacing strategy with microvariations of pace is adopted by 5000 m and 10,000 m runners in championship races. Major cross country and marathon championship races are characterized by a positive pacing strategy; whereas a U-shaped pacing strategy, which is the result of a fast endspurt, is adopted by 3000 m steeplechasers and half marathoners. In contrast, recent world record marathon performances have been characterized by even pacing, which emphasizes the differences between championship and meet races at distances longer than 800 m. Studies reviewed suggest further recommendations for athletes. Throughout the whole race, 800 m runners should avoid running wide on the bends. In turn, during major championship events, 1500 m, 5000 m, and 10,000 m runners should try to run close to the inside of the track as much as possible during the decisive stages of the race when the speed is high. Staying within the leading positions during the last lap is recommended to optimize finishing position during 1500 m and 5000 m major championship races. Athletes with more modest aims than winning a medal at major championships are advised to adopt a realistic pace during the initial stages of long-distance races and stay within a pack of runners. Coaches of elite athletes should take into account the observed difference in pacing profiles adopted in meet races vs. those used in championship races: fast times achieved during races with the help of one or more pacemakers are not necessarily replicated in winner-takes-all championship races, where pace varies substantially. Although existing studies examining pacing characteristics in elite runners through an observational approach provide highly ecologically valid performance data, they provide little information regarding the underpinning mechanisms that explain the behaviors shown. Therefore, further research is needed in order to make a meaningful impact on the discipline. Researchers should design and conduct interventions that enable athletes to carefully choose strategies that are not influenced by poor decisions made by other competitors, allowing these athletes to develop more optimal and successful behaviors.     

补服乳清蛋白对人体有氧耐力的影响

目的:观察运动前补服不同量的乳清蛋白对人体有氧耐力成绩的影响.方法:在单盲设计中,12名健康的体育系男生作为受试者,每次于运动前半小时补服不同补剂(79、14g乳清蛋白,安慰剂),然后进行12min跑的耐力运动,记录每名受试者的成绩.本实验按照补剂的不同分为三组,在三周内完成.结果:补服79、149乳清蛋白与补服安慰剂相比,机体有氧耐力水平出现显著性差异(P＜0.05).结论:在运动前补服乳清蛋白饮料可能会提高人体的有氧耐力.     

有氧耐力与分子遗传学的研究进展

人体的运动能力有许多外部表现，根据这些外部表现及其生理、生化基础人们制定了许多标准和指标用以选材。但在实际工作中不易操作。人体的运动能力都受基因的控制，在基因上都有特定的遗传标志和特征，根据这些基因特征进行选材不但准确、而且简单。随着分子生物学技术的发展和突破，研究者正把这一方法用于实践。     

Acute and residual effects of vibratory stimulation on explosive strength in elite and amateur athletes

Fourteen elite and 14 amateur athletes were subjected to vibratory stimulation during bilateral biceps curl exercises of explosive strength exertion. The athletes performed two separate series of three sets of exercises in random order. The second set of one series was administered with superimposed vibration of 44 Hz and an acceleration of about 30 m .s-2 transmitted through the two-arms handle to the arm muscles. The mechanical power of each repetition was measured by the ‘Power Teach’ instrument. The maximal and mean power values for each set were automatically recorded and shown on the screen. The acute effect was evaluated as the difference between the mean and peak power output in the second (with vibratory stimulation) and first (without vibratory stimulation) sets. Similarly, the residual effect was taken to be the difference between the power values of the third (after vibratory stimulation) and the first (before vibratory stimulation) sets. The results were subjected to a repeated-measures analysis of variance with group as a between-participants factor. The results showed that exercise mode (with vs without vibratory stimulation) resulted in a significant immediate effect for mean power and for maximal power. The factor group (elite vs amateurs) resulted in a significant effect for maximal power only. The increase in explosive strength exertion attributed to vibratory stimulation was 30.1 and 29.8 W (10.4% and 10.2%) for maximal and mean power respectively in the elite group, and 20.0 and 25.9 W (7.9% and 10.7%) respectively in the amateur athletes. Vibratory stimulation resulted in an insignificant residual effect.