Running Ability Research Articles

Sub-maximal heart rate is associated with changes in high-intensity intermittent running ability in professional rugby league players

ABSTRACTObjectives: We examined: (1) relationships among sub-maximal heart rate (sub-maxHR) following 4 minutes of the Yo-Yo intermittent recovery test level 1 (IR1) and maximal-effort performance (distance covered at volitional exhaustion), (2) test re-test reliability of sub-maxHR, and (3) whether changes in maximal-effort Yo-Yo performance are related with changes in sub-maxHR in professional rugby league players.Methods: Yo-Yo IR1 performances of 32 players were assessed before and after 28.5 ± 6.8 days of pre-season training. Relationships between sub-maxHR and maximal-effort Yo-Yo performance, and changes in maximal-effort performance and sub-maxHR were compared.Results: Maximal-effort Yo-Yo IR1 performance and sub-maxHR correlated negatively (r = −0.73, CI −0.85 to −0.55, very large). Coefficient of variation (CV) of sub-maxHR was 2.4% (CI 2.0−3.3%), worthwhile changes of small (0.7 [CI 0.5−1.0%]), moderate (2.1 [CI 1.6−3.0%]) and large (4.3 [CI 3.3−6.1%]) were identified. Training-induced changes in sub-maxHR and Yo-Yo IR1 performance displayed a negative correlation (r = −0.57, CI −0.74 to −0.33, large).Conclusions: sub-maxHR has a very large negative relationship with maximal-effort Yo-Yo IR1 performance. Training-induced changes in sub-maxHR demonstrated a large negative relationship with changes in Yo-Yo IR1 performance. The CV and worthwhile changes can determine meaningful variations in sub-maxHR in professional rugby league players.

β-Hydroxy β-Methylbutyrate (HMB) Supplementation Effects on Body Mass and Performance in Elite Male Rugby Union Players.

McIntosh, ND, Love, TD, Haszard, J, Osborne, H, and Black, KE. β-hydroxy β-methylbutyrate (HMB) supplementation effects on body mass and performance in elite male rugby union players. J Strength Cond Res 32(1): 19-26, 2018-Preseason is characterized by high training volumes with short recovery periods β-hydroxy β-methylbutyrate (HMB) has been postulated to assist with recovery. β-hydroxy β-methylbutyrate has been shown to improve strength and body composition among untrained groups; the benefits of HMB among trained populations are unclear because of the methodologies employed. This randomized control trail determined the effects of 11 weeks HMB supplementation on body mass and performance measures in 27 elite rugby players. β-hydroxy β-methylbutyrate group (n = 13), mean ± SD age 20.3 ± 1.2 years, body mass 99.6 ± 9.1 kg; placebo group (n = 14), age 21.9 ± 2.8 years body mass 99.4 ± 13.9 kg for placebo. During the supplementation period, body mass increased with HMB 0.57 ± 2.60 kg but decreased with placebo 1.39 ± 2.02 kg (p = 0.029). There were no significant differences in any of the 4 strength variables (p > 0.05). However, on the yo-yo intermittent recovery test (YoYo IR-1), the placebo group improved 4.0 ± 2.8 levels but HMB decreased 2.0 ± 3.0 levels (p = 0.003). The results of this study suggest that HMB could be beneficial for gaining or maintaining body mass during periods of increased training load. However, it appears that HMB may be detrimental to intermittent running ability in this group although further research is required before firm conclusions can be made. Only 6 participants on HMB managed to complete both YoYo IR-1 tests because of injury, a larger sample size is required to fully investigate this potentially negative effect. Further, the mechanisms behind this decrement in performance cannot be fully explained and requires further biochemical and psychological investigation.

Investigation of the physical function factor related to femoral prosthetic running ability

Investigation of the physical function factor related to femoral prosthetic running ability

NAc Ascorbic Acid Infusion Modulates Treadmill Running Ability of Rats

Nucleus accumbens (NAc) and medial prefrontal cortex have a close relationship in the brain. Previous study has shown that infusing the ascorbic acid into the mPFC can enhance the exercise ability of rats. But whether the regulation of ascorbic acid in NAc can control exercise ability is not clear. The purpose of this research is to explore the effect of ascorbic acid infusion in NAc on treadmill running ability of rats. Eighteen adult male Sprague Dawley (SD) rats were divided into the following three groups, ascorbic acid (AA+), artificial cerebrospinal fluid (C) and ascorbic acid oxidase (AA-) groups. All rats accepted a stereotactic brain surgery to implant two micro cannulaes in the NAc. After the rest for a week, ascorbic acid, artificial cerebrospinal fluid or ascorbic acid oxidase was infused into nucleus accumbens in the three groups of rats, respectively. All rats were placed on treadmill to test their running ability. The results showed that compared with C group and AA- group, AA+ group showed longer time and distance of running in treadmill. So we concluded that ascorbic acid infusion in NAc can improve the treadmill running ability of rats.

Nuclear factor (erythroid derived 2)-like 2 activation increases exercise endurance capacity via redox modulation in skeletal muscles

Sulforaphane (SFN) plays an important role in preventing oxidative stress by activating the nuclear factor (erythroid derived 2)-like 2 (Nrf2) signalling pathway. SFN may improve exercise endurance capacity by counteracting oxidative stress-induced damage during exercise. We assessed running ability based on an exhaustive treadmill test (progressive-continuous all-out) and examined the expression of markers for oxidative stress and muscle damage. Twelve- to 13-week-old Male wild-type mice (Nrf2+/+) and Nrf2-null mice (Nrf2−/−) on C57BL/6J background were intraperitoneally injected with SFN or vehicle prior to the test. The running distance of SFN-injected Nrf2+/+ mice was significantly greater compared with that of uninjected mice. Enhanced running capacity was accompanied by upregulation of Nrf2 signalling and downstream genes. Marker of oxidative stress in SFN-injected Nrf2+/+ mice were lower than those in uninjected mice following the test. SFN produced greater protection against muscle damage during exhaustive exercise conditions in Nrf2+/+ mice than in Nrf2−/− mice. SFN-induced Nrf2 upregulation, and its antioxidative effects, might play critical roles in attenuating muscle fatigue via reduction of oxidative stress caused by exhaustive exercise. This in turn leads to enhanced exercise endurance capacity. These results provide new insights into SFN-induced upregulation of Nrf2 and its role in improving exercise performance.

The Influence of Rotations on Match Running Performance in Female Australian Football Midfielders.

With female Australian football (AF) gaining popularity, understanding match demands is becoming increasingly important. The aim of this study was to compare running performances of rotated and whole-quarter state-level female AF players during match quarters. Twenty-two state-level female AF midfielders wore Global Positioning System units during 14 games to evaluate activity profiles. The Yo-Yo Intermittent Recovery Test Level 1 (Yo-Yo IR1) was used as a measure of high-intensity running ability. Data were categorized into whole quarter, rotation bout 1, and rotation bout 2 before being further divided into quartiles. Players were separated into high- or low-Yo-Yo IR1 groups using a median split based on their Yo-Yo IR1 performance. Short (4-6 min), moderate (6-12 min), and long (12-18 min) on-field bout activity profiles were compared with whole-quarter players. High Yo-Yo IR1 performance allowed players to cover greater relative distances (ES = 0.57-0.88) and high-speed distances (ES = 0.57-0.86) during rotations. No differences were reported between Yo-Yo IR1 groups when players were required to play whole quarters (ES ≤ 0.26, likelihood ≤64%). Players who were on field for short to moderate durations exhibited greater activity profiles than whole-quarter players. Superior high-speed running ability results in a greater activity profile than for players who possess lower high-speed running ability. The findings also highlight the importance of short to moderate (4-12 min) rotation periods and may be used to increase high-intensity running performance within quarters in female AF players.

The effect of a running intervention on running ability and participation in children with cerebral palsy: a randomized controlled trial

Purpose: The purpose of this study is to evaluate effects of a running intervention on running ability and participation in children with cerebral palsy.Materials and method: Children with cerebral palsy (9–18 years) with Gross Motor Function Classification System levels I-III were randomly assigned to a 12-week running intervention or usual care. Primary outcomes included improvement in running ability (assessed by Goal Attainment Scaling, high level mobility (assessed by the High-Level Mobility Assessment Tool) and participation (assessed by the Participation and Environment Measure for Children and Youth). Secondary outcomes were aerobic and anaerobic fitness and agility. Blinded assessments took place at baseline and 12 weeks. Regression analysis adjusting for baseline differences was used to determine between group differences.Results: Forty-two participants (mean age 12.5 years, SD 2.8 years; 15 female) completed the study. Statistically significant group differences at 12-weeks were found for improvements in running ability (86% treatment group versus 0% control group achieved or exceeded their running goals, p < 0.001), and participation in the school environment (Participation and Environment Measure mean difference 1.18: 95%CI 1.00–1.39, p = 0.045).Conclusion: A 12-week individualized running training skills intervention results in achievement of running ability goals and participation in the school environment in children with cerebral palsy.Implications for RehabilitationChildren with cerebral palsy who can walk unaided demonstrate impairments in higher level mobility such as running.Running is a motor skill that can be trained in children with cerebral palsy.Individually tailored running skills intervention, delivered in a group context can improve goal-identified running ability and translate into a higher frequency of participation in school activities.

Investigating the running abilities of Tyrannosaurus rex using stress-constrained multibody dynamic analysis.

The running ability of Tyrannosaurus rex has been intensively studied due to its relevance to interpretations of feeding behaviour and the biomechanics of scaling in giant predatory dinosaurs. Different studies using differing methodologies have produced a very wide range of top speed estimates and there is therefore a need to develop techniques that can improve these predictions. Here we present a new approach that combines two separate biomechanical techniques (multibody dynamic analysis and skeletal stress analysis) to demonstrate that true running gaits would probably lead to unacceptably high skeletal loads in T. rex. Combining these two approaches reduces the high-level of uncertainty in previous predictions associated with unknown soft tissue parameters in dinosaurs, and demonstrates that the relatively long limb segments of T. rex—long argued to indicate competent running ability—would actually have mechanically limited this species to walking gaits. Being limited to walking speeds contradicts arguments of high-speed pursuit predation for the largest bipedal dinosaurs like T. rex, and demonstrates the power of multiphysics approaches for locomotor reconstructions of extinct animals.

Downhill Running Followed by Foam Rolling Has No Effect on the Cost of Running

PURPOSE: Downhill running (DHR) causes muscle soreness that may affect running performance. Foam rolling (FR) is a potential recovery tool for reducing soreness and attenuating performance decrements. Running economy (RE), which quantifies the efficiency of running, is a key factor in distance running ability. It is unclear whether DHR affects RE in trained runners and whether FR is an effective recovery method for DHR-induced soreness. Furthermore, RE may be assessed in several ways, including O2 cost (VO2) and energy cost (EC, kcal*kg-1*min-1). These measures may be more accurate with allometric scaling of body weight (alloVO2 and alloEC; body weight in kg0.66). Thus, our purpose was to evaluate changes in RE with DHR and FR or placebo using 4 definitions of RE. METHODS: Subjects did submaximal running to assess RE 2-4 days before (SUBMAX1) and 48 hours after (SUBMAX2) DHR. Immediately after DHR, they performed FR or placebo (sham compression tights [T]). In a randomized crossover design, subjects repeated these tests 2-4 weeks later. RE during SUBMAX was calculated as VO2, alloVO2, EC, and alloEC. Muscle soreness was measured on a 0-10 verbal scale before DHR and SUBMAX2. RESULTS: Eight trained runners completed the study (VO2max 57±7 ml*kg-1*min-1, age 30.6±7 years, 4 females). Soreness at SUBMAX2 was greater than at SUBMAX1, showing that DHR induced soreness in all subjects (p = 0.012). Subjects had lower soreness at SUBMAX2 with FR than T (p = 0.025). However, there were no significant effects of time or treatment on VO2, alloVO2, EC, or alloEC (p > 0.05 for all comparisons). CONCLUSION: Downhill running causes muscle soreness but does not affect running performance as evaluated through RE. FR reduces DHR-induced soreness compared to a placebo. While allometric scaling and energy cost definitions of RE may be better indicators of running performance than the traditional VO2, none of the measures of RE are affected by DHR-induced muscle soreness.

Brain oxygenation declines in elite Kenyan runners during a maximal interval training session.

The purpose of this study was to characterise the cerebral oxygenation (Cox) response during a high-intensity interval training session in Kenyan runners, and to examine any relationship with running performance. 15 Kenyan runners completed a 5-km time trial (TT) and a Fatigue Training Test on a treadmill (repeated running bouts of 1-km at a pace 5% faster than their mean 5-km TT pace with a 30-s recovery until exhaustion). Changes in Cox were monitored via near-infrared spectroscopy through concentration changes in oxy- and deoxy-haemoglobin (Δ[O2Hb] and Δ[HHb]), tissue oxygenation index (TOI), and total hemoglobin index (nTHI). The number of 1-km repetitions achieved by the participants was 5.5 ± 1.2 repetitions at a mean pace of 20.5 ± 0.7kmh-1. Δ[O2Hb] measured at the end of each running repetition declined progressively over the course of the trial (p = 0.01, ES = 4.59). Δ[HHb] increased during each running bout until the end of the Fatigue Training Test (p < 0.001; ES = 6.0). TOI decreased significantly from the beginning of the test (p = 0.013, ES = 1.83), whereas nTHI remained stable (ES = 0.08). The Cox decline in the Fatigue Training Test was negatively correlated with the speed at which the test was completed (p = 0.017; r = -0.61), suggesting that the best performers were able to defend their Cox better than those of lower running ability. In conclusion, this study suggests that elite Kenyan runners cannot defend cerebral oxygenation when forced to exercise to their physiological limits. This emphasises the critical importance of pacing in their racing success.

Analysis of Player Statistics in Major League Baseball Players Before and After Achilles Tendon Repair.

No currently available literature evaluates the effect of Achilles tendon repair on professional baseball players in the Major League Baseball (MLB). The purpose of this study was to determine the impact of Achilles tendon rupture and repair on MLB players in terms of return to play and batting/fielding performance metrics. Achilles tendon rupture data were retrospectively collected using information from the MLB disabled list, injury reports, MLB game summaries, player profiles, and publicly available news articles. Four pair-matched control MLB position players were selected for each of the players who underwent advanced analysis. Baseline characteristics were compared between injured players and controls using Fisher's exact or Student's t test. Overall, the incidence of Achilles tendon rupture reported in MLB has increased substantially since 1996. Rate of return to play in MLB after Achilles tendon rupture and repair is 62% for position players (non-pitchers) who suffer the injury. There was no association of injury with any player metric. Compared with injury to the non-power side, injury to the power side was associated with fewer plate appearances, fewer triples, an increase in percentage of at-bats with strikeouts, and decreased speed score. The incidence of Achilles tendon rupture in MLB has increased substantially since 1996. While comparison suggests that overall Achilles tendon injury does not have an effect on MLB player statistics in the years following surgical repair, subset analysis of injury to the rear (power-generating) leg may lead to a decline in those statistics which denote a player's speed and running ability.

Improving Running Capacity to Ensure Chinese Men’s Football Ascending Top in Asia and Qualifying for the Word Cup

The aim of this study is to collect historical and objective data to analyze and demonstrate the necessity of improving the running capacity and kicking technique for Chinese Men’s Football based on the reality. Many methods were applied in this paper such as the Method of Comparison and Graphic Data for a scientific research. And it is suggested that Chinese men’s football must improve running capacity and kicking technique with running to ascend the top in Asia and qualify for the Word Cup because players need to run approximately 13000-170000 meters which requires their super strong running ability.

Yo-Yo Intermittent Recovery Test Performance in Subelite Gaelic Football Players From Under Thirteen to Senior Age Groups.

Roe, M and Malone, S. Yo-Yo intermittent recovery test performance in subelite Gaelic football players from under thirteen to senior age groups. J Strength Cond Res 30 (11): 3187-3193, 2016-Gaelic football is indigenous to Ireland and has similar locomotion profiles to soccer and Australian Football. Given the increasing attention on long-term player development, investigations on age-related variation in Yo-Yo intermittent recovery test level 1 (Yo-YoIR1) performance may provide useful information in talent identification, program design, and player monitoring. Therefore, the aim of this study was to evaluate Yo-YoIR1 performance across Gaelic football age groups. Male participants (n = 355) were recruited from division one, Gaelic football teams. Participants were allocated to one of the 7 groups according to respective age groups from under 13 (U13), under 14, under 15 (U15), under 16 (U16), minor, under 21 (U21), to senior age groups. Total Yo-YoIR1 distance (m) increased progressively from U13 (885 ± 347 m) to U16 (1,595 ± 380 m) equating to a rate of change of 180.2%. In comparison to U13, total distance at minor (1,206 ± 327 m) increased by 136.4%. Subsequent increases were observed in U21 (1,585 ± 445 m) and senior players (2,365 ± 489). Minimum (800-880 m) and maximum (2,240-2,280 m) total distances were comparable for U15, U16, and U21 players. Differences in total distance (m) for all age groups were statistically significant when compared to U13 players (p < 0.002). In comparison to U13 players, the magnitude of differences between age groups for total distance was deemed to be large (effect size > 0.8). Similar trends were observed for maximum velocity and estimated V[Combining Dot Above]O2max. The evolution of Yo-YoIR1 performance in Gaelic football players from adolescents to adulthood highlights how maturation may influence sport-related running ability. Changes in Yo-YoIR1 performance should be closely monitored to optimize interventions for individuals transitioning across age groups.

Factors That Influence Running Intensity in Interchange Players in Professional Rugby League.

Rugby league coaches adopt replacement strategies for their interchange players to maximize running intensity; however, it is important to understand the factors that may influence match performance. To assess the independent factors affecting running intensity sustained by interchange players during professional rugby league. Global positioning system (GPS) data were collected from all interchanged players (starters and nonstarters) in a professional rugby league squad across 24 matches of a National Rugby League season. A multilevel mixed-model approach was employed to establish the effect of various technical (attacking and defensive involvements), temporal (bout duration, time in possession, etc), and situational (season phase, recovery cycle, etc) factors on the relative distance covered and average metabolic power (Pmet) during competition. Significant effects were standardized using correlation coefficients, and the likelihood of the effect was described using magnitude-based inferences. Superior intermittent running ability resulted in very likely large increases in both relative distance and Pmet. As the length of a bout increased, both measures of running intensity exhibited a small decrease. There were at least likely small increases in running intensity for matches played after short recovery cycles and against strong opposition. During a bout, the number of collision-based involvements increased running intensity, whereas time in possession and ball time out of play decreased demands. These data demonstrate a complex interaction of individual- and match-based factors that require consideration when developing interchange strategies, and the manipulation of training loads during shorter recovery periods and against stronger opponents may be beneficial.

The Effect of Contextual Factors on Physiological and Activity Profiles in International Women's Rugby Sevens.

To evaluate the effects of contextual game factors on activity and physiological profiles of international-level women's rugby sevens players. Twenty international-level female rugby sevens players from the same national team participated in this study. Global positioning system and heart-rate data were collected at 5 World Rugby Women's Sevens Series events (2013-14 season). Total, moderate-speed (0.2-3.5 m/s), and high-speed running (3.5-5.0 m/s) distances were significantly greater in the first half (20.1% ± 4.1%, 17.6% ± 6.9%, 24.5% ± 7.8%), during losses (11.4% ± 6.1%, 6.1% ± 6.4%, 26.9% ± 9.8%), during losses of large magnitudes (≥2 tries) (12.9% ± 8.8%, 6.8% ± 10.0%, 31.2% ± 14.9%), and against top-4 opponents (12.6% ± 8.7%, 11.3% ± 8.5%, 15.5% ± 13.9%). In addition, total distance increased (5.0% ± 5.5%) significantly from day 1 to day 2 of tournaments, and very-high-speed (5.0-6.5 m/s) running distance increased significantly (26.0% ± 14.2%) during losses. Time spent between 90% and 100% of maximum heart rate (16.4% ± 14.5%) and player load (19.0% ± 5.1%) were significantly greater in the second half. No significant differences in physiological or activity profiles were observed between forwards and backs. Game half, game outcome, tournament day, opponent rank, and margin of outcome all affected activity profiles, whereas game half affected physiological profiles. No differences in activity or physiological profiles were found between playing positions. Practitioners are advised to develop high-speed running ability in women's rugby sevens players to prepare them to tolerate the varying factors that affect activity profiles.

The specificity of the Loughborough Intermittent Shuttle Test for recreational soccer players is independent of their intermittent running ability

ABSTRACTThe aim of the present study was to evaluate whether or not recreational soccer players (SP) and non-soccer players (non-SP) with similar intermittent-running ability had similar physiological responses to a soccer match-simulation protocol. Twenty-two recreational SP and 19 fitness-matched non-SP participated. Yo-Yo level 1 assessed intermittent-running ability, while the Loughborough Intermittent Shuttle Test served as soccer match-simulation protocol. Heart rate (HR), blood lactate concentration [La−] and rating of perceived exertion (RPE) were recorded after each bout (1–5, plus an exhaustive task). SP had lower HR after the third, fourth and fifth bout, compared to non-SP. Similarly, SP had lower [La−] after the third, fourth and the fifth bout. SP also had lower RPE after the third, fourth and fifth bout. The appropriateness of intermittent-running ability as the main determinant of physical performance in SP was questioned.

The Degree of Tracking of Physical Fitness during The Growth and Development Period

PURPOSE:The purpose of this study was to ascertain the degree tracking of physical fitness during the growth and development period, by examining the relationship of physical fitness at 3–5 years of age, with that at 12 years, using longitudinal data. METHODS:Subjects included 61 children (23 boys and 38 girls) who performed the physical fitness test at ages 3, 4, 5, and 12 years. The first principal component score was used as an indicator of overall physical fitness. The measured values of running, jumping, and throwing were added to this value and used as an indicator of motor ability. To determine the amount of tracking, we calculated the Pearson correlation coefficient between the assessments at 3–5 years and 12 years. RESULTS:In boys, the assessment at 12 years showed a significant correlation with that at 3, 4, and 5 years, in terms of overall physical fitness (with 3 years: r=0.498, with 4 years: r=0.590, with 5 years: r=0.671), throwing ability, and jumping ability. On the other hand, in girls, the assessment at 12 years showed a significant correlation with that at 3, 4, and 5 years, in terms of overall physical fitness (with 3 years: r=0.445, with 4 years: r=0.521, with 5 years: r=0.559), jumping ability, and running ability; and with throwing ability at 5 years. CONCLUSIONS:The characteristics of physical fitness at the age of 12 years strongly influenced by the overall physical fitness during the ages of 3–5 years, in both boys and girls. Therefore, the lifestyle during childhood, especially related to exercise play habits, are important for the improvement of subsequent healthy development and motor function.Supported by Grant-in-Aid for Scientific Research (C) (No.25350840) from Ministry of Education, Culture, Sports, Science and Technology in Japan.

Anthropometric, Sprint, and High-Intensity Running Profiles of English Academy Rugby Union Players by Position.

The purpose of this study was to evaluate the anthropometric, sprint, and high-intensity running profiles of English academy rugby union players by playing positions, and to investigate the relationships between anthropometric, sprint, and high-intensity running characteristics. Data were collected from 67 academy players after the off-season period and consisted of anthropometric (height, body mass, sum of 8 skinfolds [∑SF]), 40-m linear sprint (5-, 10-, 20-, and 40-m splits), the Yo-Yo intermittent recovery test level 1 (Yo-Yo IRTL-1), and the 30-15 intermittent fitness test (30-15 IFT). Forwards displayed greater stature, body mass, and ∑SF; sprint times and sprint momentum, with lower high-intensity running ability and sprint velocities than backs. Comparisons between age categories demonstrated body mass and sprint momentum to have the largest differences at consecutive age categories for forwards and backs; whereas 20-40-m sprint velocity was discriminate for forwards between under 16s, 18s, and 21s. Relationships between anthropometric, sprint velocity, momentum, and high-intensity running ability demonstrated body mass to negatively impact on sprint velocity (10 m; r = -0.34 to -0.46) and positively affect sprint momentum (e.g., 5 m; r = 0.85-0.93), with large to very large negative relationships with the Yo-Yo IRTL-1 (r = -0.65 to -0.74) and 30-15 IFT (r = -0.59 to -0.79). These findings suggest that there are distinct anthropometric, sprint, and high-intensity running ability differences between and within positions in junior rugby union players. The development of sprint and high-intensity running ability may be impacted by continued increases in body mass as there seems to be a trade-off between momentum, velocity, and the ability to complete high-intensity running.

Match demands of professional rugby football codes: A review from 2008 to 2015

Rugby football codes have continually increased in popularity and are played professionally around the world at domestic, national and international level. Coaching professionals can use the findings of this review to guide training practices for the professional rugby football player, particularly those players who may be competing concurrently or transferring between codes. The development of repeated high-intensity exercise ability should be a key emphasis of training programmes especially for players who are aiming to compete at higher competition standards. Importantly, there are considerable differences in repeated high-intensity exercise demands of match-play for different positional groups. For greatest transference to match performance, training programs should replicate the frequency and duration of repeated high-intensity exercise bouts in addition to the relative contribution of high-intensity running, tackling and physical collisions. Training programmes should not neglect developing players’ prolonged high-intensity running ability as high-speed running efforts may occur separately from repeated high-intensity exercise bouts and likely place considerable demands on rugby football players, particularly in rugby sevens competition. Rugby football players have been shown to experience transient fatigue patterns during match-play where teams may be susceptible to conceding points or sustaining injury. Improved physical conditioning strategies may reduce development of match-fatigue; however, research is yet to investigate the influence of fitness levels and team strategies. A better understanding of these factors and how they interact with match-fatigue will assist with the improvement of training practices for professional rugby football players.

ロッカーボギー機構を用いた全方向移動プラットフォームの開発

In connection with the super-aging society, there exists a growing interest in omnidirectional powered-wheelchairs that have superior mobility in a narrow space. An omnidirectional mobile robot composed of active dual-wheel caster assemblies can use general wheels such as rubber tires, so that it is easily applied to a powered wheelchair. This study is aimed at developing an omnidirectional mobile platform using active dualwheel caster assemblies in consideration of the run in a public road. An omnidirectional mobile platform using a rocker-bogie suspension system is proposed to improve the running ability, and several active dual-wheel caster modules are produced so as to be used in such a platform. In this paper, we give an overview of the active dual-wheel caster assemblies and the proposed robot, and describe the process of actual production of such modules and the associated experimental results.