Analysis of physiological and biomechanical factors affecting running economy / 中国组织工程研究

BACKGROUND: Running economy is considered as an important indicator of the performance of endurance athletes, especially long-distance runners. It is usually defined as the energy demand of running at a given speed, and expressed as the oxygen intake at a given speed. OBJECTIVE: To review the existing physiological and biomechanical factors affecting the running economy of runners. METHODS: With “running economy, physiological factors, biomechanical and neuromuscular characteristics, spatiotemporal factors, lower limb kinematic factors, kinetic factors, nutritional interventions” as search terms, PubMed database (1960-2018) was searched to include literatures related to running performance, acute or chronic interventions, and other influencing factors. RESULTS AND CONCLUSION: A total of 113 literatures were obtained. According to the inclusion and exclusion criteria, 58 literatures were analyzed. Current evidence shows that cardiopulmonary function, muscle fiber type, muscle strength, leg stiffness and other physiological factors are related to the improvement of running economy. However, there is no unified conclusion on the relationship between the temperature change of runners and the elastic potential energy and running economy. The biomechanical factors that are beneficial to improve running economy include stride frequency or length, vertical oscillation, lower limb moment of inertia, leg extension when toes are off the ground, and arm swing. However, the contact time between the feet and the ground, trunk inclination and other factors are inconsistent with running economy. Among other influencing factors, high-altitude adaptation can improve running economy; the relationship between extensibility and flexibility and running economy remains to be determined. Some nutritional interventions are also of concern, most notably dietary nitrates. Although most of the factors affecting running economy have been summarized in this paper, future studies can focus on individual runners in order to determine how the athlete’s structure and functional abilities affect running economy, as well as subsequent performance and athletic injuries.

A comparison of aerobic capacity in long-distance runners and triathletes with the same level of running performance / 体力科学

The purpose of this study was to clarify the aerobic fitness of triathletes comparing with long-distance runners with the same level of running performance. Thirteen male university endurance athletes were divided into two groups ; long-distance runners and triathletes. The subjects performed maximal and submaximal treadmill running test to assess their maximal oxygen uptake (VO2max) and running economy (RE). The VO2max (ml/kg/min) in triathletes was lower than that in the runners (p = 0.08, d = 1.18). The RE (ml/kg/km) in triathletes was higher than that in the runners (p = 0.05, d = 1.34). This study suggests that the difference of aerobic fitness between two homogeneous groups is caused by running form and the training with preceding exercise.

Effects of a 4-week high-intensity interval training on pacing during 5-km running trial

This study analyzed the influence of a 4-week high-intensity interval training on the pacing strategy adopted by runners during a 5-km running trial. Sixteen male recreational long-distance runners were randomly assigned to a control group (CON, n=8) or a high-intensity interval training group (HIIT, n=8). The HIIT group performed high-intensity interval-training twice per week, while the CON group maintained their regular training program. Before and after the training period, the runners performed an incremental exercise test to exhaustion to measure the onset of blood lactate accumulation, maximal oxygen uptake (VO2max), and peak treadmill speed (PTS). A submaximal constant-speed test to measure the running economy (RE) and a 5-km running trial on an outdoor track to establish pacing strategy and performance were also done. During the 5-km running trial, the rating of perceived exertion (RPE) and time to cover the 5-km trial (T5) were registered. After the training period, there were significant improvements in the HIIT group of ∼7 and 5% for RE (P=0.012) and PTS (P=0.019), respectively. There was no significant difference between the groups for VO2max (P=0.495) or onset of blood lactate accumulation (P=0.101). No difference was found in the parameters measured during the 5-km trial before the training period between HIIT and CON (P>0.05). These findings suggest that 4 weeks of HIIT can improve some traditional physiological variables related to endurance performance (RE and PTS), but it does not alter the perception of effort, pacing strategy, or overall performance during a 5-km running trial.

The effect of flutamide on the physical working capacity and activity of some of the key enzymes for the energy supply in adult rats / 亚洲男科学杂志(英文版)

The aim of the study was to assess the effects of androgen receptor antagonists on the physical working capacity and activity of some of the key muscle enzymes for the energy supply in rats. Young adult male Wistar rats were divided into two groups. One group received 15 mg kg-1 of flutamide daily for 6 days a week and the other group served as control for 8 weeks. At the beginning and at the end of the experiment, all rats were subjected to submaximal running endurance (SRE), maximum time to exhaustion (MTE), and maximal sprinting speed (MSS) tests. At the end of the trial, maximum oxygen consumption (VO2max) test was performed and the levels of testosterone, erythrocytes, hemoglobin as well as enzyme activity of succinate dehydrogenase (SDH), lactate dehydrogenase (LDH), and NAD.H2-cytochrome-c reductase (NAD.H2) of the gastrocnemius muscle were measured. Serum testosterone of the flutamide-treated rats was higher than that of the controls, which verifies the effectiveness of the dose chosen. MTE and SRE of the anti-androgen-treated group were lower compared with the initial values. Flutamide treatment decreased the activity of SDH and NAD.H2 compared with the controls. We found no effect of the anti-androgen treatment on MSS, VO2max, running economy, LDH activity, and hematological variables. Our findings indicate that the maintenance of the submaximal and maximal running endurance as well as the activity of some of the key enzymes associated with muscle oxidative capacity is connected with androgen effects mediated by androgen receptors.

Relationships between running performance and the cross–sectional area of the psoas major, and peak oxygen uptake in elite junior long–distance runners / 体力科学

The purpose of this study was to examine the relationships between running performance and the cross–sectional area of the psoas major, peak oxygen uptake, and running economy in male junior long–distance runners. The subjects were 37 male junior athletes who achieved good records in interscholastic athletic competition during 5 years (2011–2015). Their seasonal best times in a 5,000 m race (5,000m–SB) were 14:04.11 ± 0:07.25 (13:53.64–14:16.15). In a multiple regression analysis, 5,000m–SB was statistical significantly correlated with the cross–sectional area of psoas major (16.0 ± 1.7 cm²) measured on magnetic resonance imaging and peak oxygen uptake (4.25 ± 0.36 l min^-1 [76.9 ± 5.8 ml min^-1 kg^-1]) during a lactate curve test comprising five stages. However, 5,000m–SB was not related to oxygen uptake at the work–load which was less than the load at the lactate threshold estimated by using the lactate curve test results. These results suggest that a high volume of the psoas major, the largest hip–flexor muscle, and peak oxygen uptake are among the important factors for junior long–distance runner performance.

Estratégia de corrida em média e longa distância: como ocorrem os ajustes de velocidade ao longo da prova? / La estratégia de la carrera del media y larga distancia: como se producen los ajustes de velocidad a lo largo de la carrera? / Pacing strategy in middle and long distance running: how are velocities adjusted during the race?

A estratégia de corrida tem sido apontada como um fator decisivo para o sucesso do atleta. Durante corridas de média e longa duração, a melhor estratégia será aquela capaz de poupar as "reservas fisiológicas", permitindo ao atleta terminar a prova no menor tempo possível. O controle da estratégia de corrida parece ser influenciado por fatores fisiológicos e psicológicos, que são ajustados constantemente durante a corrida, permitindo ao atleta determinar a intensidade do esforço. Diversas variáveis fisiológicas têm sido relacionadas aos ajustes da estratégia de corrida, no entanto, os resultados observados são controversos e foco de grandes discussões. Assim, a presente revisão tem como objetivo propiciar aos profissionais do esporte um melhor entendimento de questões como: 1) quais as melhores estratégias adotadas para determinado tipo de prova?; 2) como os ajustes da estratégia de corrida são realizados?; e 3) quais variáveis fisiológicas influenciam no controle da estratégia de corrida?.

The pacing strategy has been shown as an important factor for athletes' performance. During middle and long distance races, the best pacing strategy will be able to maintain a "physiological reserve" and to allow the athlete to run in his/her best time. It should be mentioned that the pacing strategy can be altered by physiological and psychological factors. These factors are frequently adjusted throughout the race and they will be used to control runner's pace. Several physiological variables have been suggested to have an important role in pacing strategy control. However, there is still controversial findings among the studies. Thus, the aim of this review was provide a better understanding about some questions such as: 1) what is the best pacing strategy for a specific race?; 2) how pacing strategy is controlled by the runner?; and 3) how physiological variables can induce changes on pacing strategy?.

La estrategia de la carrera ha sido identificada como un factor decisivo para el éxito del atleta. Durante las carreras de médio y largo plazo, la mejor estrategia es aquella que puede salvar a la "reserva fisiológica" que permite al atleta terminar la carrera en el menor tiempo posible. El control de la estrategia de carrera parece estar influenciada por algunos factores fisiológicos y psicológicos, que se ajustan com frecuencia durante la carrera, lo que permite al atleta determinar la intensidad del esfuerzo. Muchas de las variables fisiológicas se han relacionadas con los ajustes de la estrategia de carrera, sin embargo, los resultados observados son controvertidos y foco de muchos debates. Por lo tanto, esta revisión tiene como objetivo proporcionar a los profesionales del deporte una mejor comprensión de temas tales como: 1) cuáles son las mejores estrategias adoptadas para un tipo particular de prubea?; 2) cómo los ajustes de estrategia de prubea se hacen?; y 3) las variables fisiológicas que influyen en el control de la estrategia de carrera?.

THE RELATIONSHIP BETWEEN THE RUNNING ECONOMY AND THE HOPPING ECONOMY IN THE LONG DISTANCE RUNNER / 体力科学

Running economy is an important factor in determining a performance of a long distance running. The purpose of this study was to examine the relationship between the running economy and the submaximal hopping economy. Twelve long-distance runners performed a submaximal repeated hopping exercise on a force platform at a frequency of 2.2Hz and the maximum five-repeated rebound jumping (5RJ). Jumping height, contact time, maximum ground reaction force and oxygen intake were recorded during submaximal repeated hopping exercise. In addition, they performed the submaximal running for a distance of 3200m on an outdoor 400m track. Oxygen intake was recorded during the submaximal running. Then running economy (RE = V/VO₂) was calculated by using oxygen intake (VO₂) and running speeds (V). Hopping economy (HE = h/VO₂) was calculated by using oxygen intake (VO₂) and average jumping height (h). As a result of this study, we confirmed that a submaximal repeated hopping exercise performed for a ten-minute period was an aerobic exercise and a steady-state exercise. There was a significant positive correlation between RE and HE (r = 0.805, p＜0.01). These results suggest that hopping economy is an important factor in running economy. On the other hand, we did not find a significant correlation between HE and 5RJ. Furthermore, between RE and RJ index of the submaximal hopping exercise, a significant positive correlation was found (r = 0.735, p＜0.01). Therefore, RE seems to be connected with the Stretch-shortening cycle (SSC) function of the legs. We conclude that the SSC ability of a long distance runner can be evaluated appropriately by using the submaximal repeated hopping exercise of this study.

INFLUENCE OF DIFFERENT STRETCHING ON RANGE OF MOTION AND RUNNING ECONOMY IN LONG DISTANCE RUNNERS / 体力科学

The purpose of this study was to examine the influence of autostretching and static stretching on range of motion (ROM) and running economy (RE) in long-distance runners. Twenty-two male distance runners were randomly assigned to an autostretching group (n=8), a static stretching group (n=7) and non-intervention control group (n=7). The experimental protocol was composed of interventions between treadmill runnings for RE. The interventions were either autostretching or static stretching, after the first treadmill running. The oxygen consumption (VO₂) as RE was measured at three steady-state running speeds (240m/min, 268m/min, and 295m/min). Goniometric measurements of hip flexion and ankle dorsiflexion ROM were taken immediately before and after each treadmill running for RE. The results showed that the autostoretching group had a significant decrease in VO₂ at 240m/min (p＜0.05), and at 268m/min (p＜0.05). On the other hand, the control group had a significant increase in VO₂ only at 295m/min (p＜0.05). At the same time, the autostretching group had significant improvements in ROM for hip flexion (p＜0.05) and ankle dorsiflexion (p＜0.05). The static stretching group had no significant changes in RE or ROM. The results of this experiment suggest that autostretching had a positive effect in improving RE in subjects of this study, and indicate the possibility that improved RE leads to the improvement of long-distance runners' performance.