Row Players Research Articles

Revisiting the Asymmetric Matching Pennies Contradiction in China.

The asymmetric matching pennies contradiction posits that contrary to the prediction of mixed-strategy Nash equilibrium, experimental subjects' choices are, in practice, based heavily on the magnitudes of their own payoffs. Own-payoff effects are robustly confirmed in the literature. Closely following the experimental setups in the literature which support the contradiction, we conduct a series of asymmetric matching pennies games in China, hypothesizing play which is closer to equilibrium frequencies than previously found. Contrary to previous experiments which were conducted in the United States, we find that there are essentially no own-payoff effects among Row players who face large payoff asymmetry. In a Quantal Response Equilibrium framework allowing for altruism or spite, the behavior of our subjects corresponded to a positive spite parameter, whereas the results of previous studies corresponded to altruism. Our results may be consistent with recent psychology literature that finds people from collectivist cultures are substantially more adept at taking the perspective of others compared with people from individualist cultures, a feature of the reasoning needed to obtain mixed-strategy equilibrium.

DETERMINATION OF A PROMOTIONAL STRATEGY FOR E-COMMERCE COMPETITION IN INDONESIA USING GAME THEORY

This research aims to determine the expected value of strategy (expected payoff) from the promotional strategies carried out by two Indonesian e-commerce companies, Tokopedia and Shopee. It is intended to generate maximum profit or minimal loss caused by the competition between the two companies through game theory simulation. The research design uses quantitative data with an applied research design. The analytical method used in this research is the Game Theory approach. The data was processed using the POM-QM application for Windows V5.2. The results show that completing the competitive payoff matrix in both e-commerce companies uses a pure strategy. The calculations and data processing results show that the maximum value is the same as the minimum value, which means that the saddle point has been reached and is the Optimal Strategy for the game value of -24.11. Because the game value from the payoff matrix is negative, the game is won by the column player, namely Shopee, using a promotional strategy in the form of free shipping. Meanwhile, to minimize the loss of row players, Tokopedia can use a promotional strategy in the form of cashback

Loss aversion in asymmetric anti‐coordination games

AbstractThis paper studies theoretically and experimentally how the possibility of a negative payoff to one player in 2‐by‐2 hawk‐dove games affects the strategic behavior of both players. Exposing column players to a possibility of negative payoff allows us to examine if row players can anticipate the column players' loss aversion. A level‐k model with loss averse agents predicts treatment effects across two versions of hawk‐dove games with and without losses. Our data support a direct effect of loss aversion and fail to support the anticipation of loss aversion. Specifically, the column players in the treatment group are more likely to play Dove when they face losses; while, only few untreated participants acting as row players seem to anticipate such increased propensity of choosing Dove by their opponents. Further, a time effect is documented and found to be explained by increases in participants' depths of strategic reasoning over time.

Macrophages in Atherosclerosis, First or Second Row Players?

Macrophages represent a cell type that has been widely described in the context of atherosclerosis since the earliest studies in the 17th century. Their role has long been considered to be preponderant in the onset and aggravation of atherosclerosis, in particular by participating in the establishment of a chronic inflammatory state by the release of pro-inflammatory cytokines and by uncontrolled engorgement of lipids resulting in the formation of foam cells and later of the necrotic core. However, recent evidence from mouse models using an elegant technique of tracing vascular smooth muscle cells (VSMCs) during plaque development revealed that resident VSMCs display impressive plastic properties in response to an arterial injury, allowing them to switch into different cell types within the plaque, including mesenchymal-like cells, macrophage-like cells and osteochondrogenic-like cells. In this review, we oppose the arguments in favor or against the influence of macrophages versus VSMCs in all stages of atherosclerosis including pre-atherosclerosis, formation of lipid-rich foam cells, development of the necrotic core and the fibrous cap as well as calcification and rupture of the plaque. We also analyze the relevance of animal models for the investigation of the pathophysiological mechanisms of atherosclerosis in humans, and discuss potential therapeutic strategies targeting either VSMCs or macrophage to prevent the development of cardiovascular events. Overall, although major findings have been made from animal models, efforts are still needed to better understand and therefore prevent the development of atherosclerotic plaques in humans.

The peripheral perception and its relation with backline and front row players for Sulaimani handball adolescent

Perception is one of the mental processes, which plays an important role in the sport aspects. Therefore, it is one of the basic requirements for improving performance in various sports. The importance of this study is that, handball players should be attempt in such peripheral perception test in order to develop player’s performance and achieve a high altitude.As a researcher I thought that in the training session here is a lack of using scientific laboratories to evaluate the elevation of the player that would be guidance for coaches to maintain their training plan.Aim of the study:-To determine the amount of perception of the players, also the comparison of perception between the players of the back and front lines of the players of the participants.Method of the study:-Used descriptive method in the survey method appropriate to the research problem.
 the results of the perceptual assessment, through which the research objectives and hypotheses were achieved, and the researcher concluded that the research sample has (a field of vision, focus power, divided attention, reaction time, and emotional maturity) were approved, as there are Moral correlation relationship between the different playing positions and the perceptual variables (field of vision, concentration force, divided attention, reaction time, and emotional maturity).

Head Impact Characteristics Based on Player Position in Collegiate Soccer Athletes

The study objective was to determine the magnitude and frequency of head impacts in NCAA Division III soccer athletes based on player position and type of play (offense, defense, transition). Across player position, male and female soccer defenders sustained the most head impacts (males IR = 18.89, 95% CI = 16.89–20.89; females IR = 8.45, 95% CI = 7.25–9.64; IRR = 2.23, 95% CI = 1.87–2.67). The study revealed a nonstatistically significant interaction between sex, player position, and type of play for both linear (p = .42) and rotational accelerations (p = .16). Defenders sustained the majority of the head impacts in the study sample, suggesting preventative initiatives should be focused on back row players.

Positional Body Composition of Female Division I Collegiate Volleyball Players.

Bisch, KL, Bosch, TA, Carbuhn, A, Stanforth, PR, Oliver, JM, Bach, CW, and Dengel, DR. Positional body composition of female division I collegiate volleyball players. J Strength Cond Res 34(11): 3055-3061, 2020-The primary study objective was to measure positional differences in total and regional body composition among female NCAA Division I collegiate volleyball players using dual X-ray absorptiometry (DXA). The secondary objective was to examine normative age curves for fat and lean mass (LM) variables. Ninety female volleyball players from 5 universities received a DXA scan. Athletes were categorized by position: middle blocker (MB = 31), outside hitter (OH = 32), setter (ST = 9), and Libero (LB = 18). Height, body mass, total and regional fat mass (FM), LM, bone mineral density (BMD), and abdominal visceral adipose tissue were measured by DXA. Body mass distribution ratios were calculated. The secondary age analysis included a subset of 153 DXA scans (n = 83, ages 18-21 years). Front row players (i.e., MB and OH) had significantly greater total and regional LM and BMD measures (p < 0.05, all), compared with non-front row players (i.e., LB and ST). Differences in total LM (p < 0.001) were significantly influenced by height. Front row players had consistently lower mass distribution ratios compared with non-front row players (p < 0.05, all). Lean mass index (LMI, p = 0.752) and FM index (FMI, p = 0.392) were not significantly different across ages. Back row players have greater relative upper body mass, whereas mass in front row players is more evenly distributed between the upper and lower body. Bone mineral density differences may be influenced by repeated impact of jumping during the attacking and blocking actions of front row players. Minimal changes in LMI and fluctuations in FMI can be expected across an athlete's career.

Assessing the whole-match and worst-case scenario locomotor demands of international women’s rugby union match-play

ObjectivesTo profile the distances covered during international women’s rugby union match-play and assess the duration-specific worst-case scenario locomotor demands over 60-s to 600-s epochs, whilst comparing the values determined by fixed epoch (FIXED) versus rolling average (ROLL) methods of worst-case scenario estimation and assessing positional influences. DesignDescriptive, observational. MethodsTwenty-nine international women’s rugby union players wore 10Hz microelectromechanical systems during eight international matches (110 observations). Total, and per-half, distances were recorded, whilst relative total and high-speed (>4.4ms−1) distances were averaged using FIXED and ROLL methods over 60–600-s. Linear mixed models compared distances covered between match halves, assessed FIXED versus ROLL, and examined the influence of playing position. ResultsPlayers covered ∼5.8kmmatch−1, with reduced distances in the second- versus first-half (p<0.001). For worst-case scenario total (∼8–25%) and high-speed (∼10–26%) distance, FIXED underestimated ROLL. In ROLL, worst-case scenario relative total and high-speed distances reduced from ∼144−161mmin−1 and ∼30−69mmin−1 over 60-s, to ∼8089mmin−1 and ∼516mmin−1 in the 600-s epoch, respectively. Forwards performed less high-speed running over all epochs and covered less total distance during epochs of 60-s, 180-s, 420-s and 480-s, compared with backs. Front row players typically returned the lowest locomotor demands. ConclusionsThis is the first study reporting the positional and worst-case scenario demands of international women’s rugby union, and indicates an underestimation in FIXED versus ROLL over 60-s to 600-s epochs. Knowledge of the most demanding periods of women’s rugby union match-play facilitates training specificity by enabling sessions to be tailored to such demands.

Cervical spine kinematics during machine-based and live scrummaging

ABSTRACTThe aim of this study was to compare cervical spine kinematics in rugby union front row players during machine-based and “live” scrummaging. Cervical spine kinematics was measured via electromagnetic tracking of sensors attached to the head and thorax. Joint angles were extracted from each trial at two time points (“bind” prior to engagement and instant of impact) for comparison between scrummaging conditions. The effect of scrummaging condition on kinematics was evaluated using a mixed effects model and estimations were based on a Bayesian framework. With differences ranging from 38° to 50°, the results show that the cervical spine is consistently more flexed when scrummaging against opponents than against a scrum machine. In contrast, there are little differences in the excursion of lateral-flexion (range 5–8°) and axial rotation (7°) between the two conditions. The findings from this study provide clear information on motion patterns in different scrum formations, and suggest that the current design of scrum machines may not promote the same pattern of movement that occurs in live scrums. The results highlight that findings from previous studies that have investigated kinematics during machine-based scrummaging may not be generalisable to a competitive scrummaging context.

Inconsistent anticipatory postural adjustments (APAs) in rugby players: a source of injuries?

BackgroundWe are developing since 2010 with Thales and the Fédération Française de Rugby (FFR) M-Rex, a new kind of rugby scrum simulator. The study questioned whether it could improve safety...

Positional Body Composition of Division I Volleyball Players, Consortium of College Athlete Research (C-CAR) Study

PURPOSE: To identify normative values for total and regional body composition by position for female NCAA Division I collegiate volleyball players using dual X-ray absorptiometry (DXA). METHODS: Eighty-nine female volleyball players (ages 17-23) from multiple universities received a DXA scan. Athletes were categorized by position: Middle Blocker (MB=30), Outside Hitter (OH=32), Setter (ST=9), and Libero (LB=18). Total fat mass (FM) and lean masses (LM) were measured by DXA, as well as abdominal visceral adipose tissue (VAT) and total and regional measures of bone mineral density (BMD). An ANOVA assessed the effect of position on body composition and BMD measurements. Tukey’s HSD post-hoc analysis test identified significance between positions. RESULTS: As expected, height was statistically significant (p<0.01) between all positions: MB (185.8 ± 4.6 cm) > OH (181.7 ± 4.1 cm) > ST (174.7 ± 3.7 cm) > LB (167.8 ± 8.0 cm). Weight was significantly greater in MB and OH (80.1 ± 9.3 kg, 76.6 ± 7.8 kg) compared to LB (64.5 ± 7.6 kg, p<0.001), and MB compared to ST (69.7 ± 5.7 kg, p=0.006). Body percent fat was not statistically significant by position (mean = 25.3%). Total LM was greater in MB and OH (55.7 ± 4.6 kg, 54.1 ± 4.7 kg) compared to LB and ST (45.9 ± 4.9 kg, 48.3 ± 3.2 kg, p<0.01). Total FM was significantly greater in MB than LB (21.0 ± 6.9 kg, 16.1 ± 4.0 kg, p=0.016). VAT mass was not significantly (p>0.05) different between positions. After adjusting for weight, total BMD was significantly greater in MB (1.39 ± 0.1 g/cm3, p<0.001) and OH (1.41 ± 0.09 g/cm3, p=0.002) compared to LB (1.30 ± 0.08 g/cm3), but not ST (1.31 ± 0.07 g/cm3, p>0.05). Leg BMD was higher in MB and OH (1.54 ± 0.11 g/cm3, 1.53 ± 0.11 g/cm3) compared to LB and ST (1.39 ± 0.09 g/cm3, 1.4 ± 0.06 g/cm3, p=0.001-0.008). Spine BMD was higher in MB and OH (1.32 ± 0.15 g/cm3, 1.33 ± 0.12 g/cm3) compared to LB (1.22 ± 0.09 g/cm3, p=0.03). CONCLUSIONS: Total body composition measures vary significantly by position; however, the similarities in percent body fat imply differences may be influenced primarily by height. Future studies should examine the distribution of mass. BMD differences may be influenced by repeated impacts of jumping during the attacking and blocking actions of front row players. These data provide some normative DXA data for collegiate volleyball players.

Maximum running intensities during English academy rugby union match-play

ABSTRACTTo quantify and compare the maximum running intensities during rugby union match-play.Running intensity was quantified using micro-technology devices (S5 Optimeye, Catapult) from 202 players during 24 matches (472 observations). Instantaneous speed was used to calculate relative distance (m·min−1) using a 0.1 s rolling mean for different time durations (15 and 30 s and 1, 2, 2.5, 3, 4, 5, and 10 min). Data were analysed using a linear mixed-model and assessed with magnitude-based inferences and effect sizes (ES).Running intensity for consecutive durations (e.g., 15 s vs. 30 s, 30 s vs. 1 min, etc.) decreased as time increased (ES = 0.48–2.80). Running intensity was lower in forwards than backs during all durations (−0.74 ±0.21 to −1.19 ±0.21). Running intensity for the second row and back row positions was greater than the front row players at all durations (−0.58 ±0.38 to −1.18 ±0.29). Running intensity for scrum halves was greater (0.46 ±0.43 to 0.86 ±0.39) than inside and outside backs for all durations besides 15 and 30 s.Front rowers and scrum halves were markedly different from other sub-positional groups and should be conditioned appropriately. Coaches working in academy rugby can use this information to appropriately overload the intensity of running, specific to time durations and positions.

ULTRASONOGRAPHIC ASSESSMENT OF NECK MUSCULAR SIZE AND RANGE OF MOTION IN RUGBY PLAYERS

World Rugby Union laws are constantly evolving towards stringent injury-prevention, particularly for contested scrums, since front row players are most at risk of cervical spine injuries. Recently, some countries have also introduced tailored training programs and minimum performance requirements for playing in the front row. Nevertheless, these approaches lack an objective assessment of each cervical muscle that would provide protective support. Since front row players are the most at risk for cervical spine injuries due to the specific type of contact during scrums, the purpose of this study was to ascertain whether significant differences exist in neck muscle size and range of motion between front row players and players of other positions, across playing categories. Cross-sectional controlled laboratory study. 129 sub-elite male subjects from various first-team squads of Belgian Rugby clubs were recruited. Subjects were grouped according to age: Junior (J) < 19 years old, Senior (S) 19 to 35 years old and Veteran (V) > 35 years old; as well as playing position: Front row players (J = 10, S = 12, V = 11 subjects), (Rest of the) pack (J = 12, S = 12, V = 10), backs (J = 10, S = 11, V = 11). An age-matched control group of non-rugby players was also recruited (J = 10, S = 10, V = 10).For each subject, the total neck circumference (NC) and the cervical range of motion (CROM) were measured. In addition, the thickness of the trapezius (T), splenius capitis (SCa), semispinalis capitis (SCb), semispinalis cervicis (SPC), sternocleidomastoid muscles (SCOM), and the total thickness of all four structures (TT), were measured using ultrasonography. In each age category, compared to controls, rugby players were found to have decreased CROM, an increase in neck circumference (NC), and increased total thickness (TT), trapezius (T), semispinalis capitis (SCb) and sternocleidomastoid muscles (SCOM) sizes. For junior players, the thickness of the semispinalis cervicis (SPC) was also increased compared to controls. The CROM was decreased in front row players compared to pack and back players for all age categories; Front row seniors also showed an increase in trapezius (T), splenius capitis (SCa), semispinalis capitis (SCb) and total thickness (TT), compared to back players. In regard of the differences in cervical values found between player positions, the implementation of both range of motion and echography muscle thickness assessments could serve to create an additional measurement for all front row players, that could complement current pre-participation screening used by rugby federations by objectively monitoring muscular size and motion amplitude around the cervical spine.

The influence of nationality and playing position on relative age effects in rugby union: A cross-cultural comparison.

Background: Recent research in a French context suggested that relative age effects (RAEs) in rugby union may be influenced by playing position; specifically, that RAEs may be more pronounced in back row players who do not have as extreme an anthropomorphic profile as other forward positions. Methods: In the present study, dates of birth of 6 663 players from four nations (Australia, England, New Zealand, South Africa) were analysed for relative age effects. Results: The hypothesis that RAEs would be more pronounced in back row players was not supported. South African rugby was an obvious outlier due to the finding that RAEs were present across all playing units. These results suggest that late maturing players have been disproportionately lost to the South African system across all positions. Conclusion: Nation-specific youth sport culture appears to be more important than playing position for determining who is at risk of RAEs in rugby union.

The influence of nationality and playing position on relative age effects in rugby union: A cross-cultural comparison.

Background: Recent research in a French context suggested that relative age effects (RAEs) in rugby union may be influenced by playing position; specifically, that RAEs may be more pronounced in back row players who do not have as extreme an anthropomorphic profile as other forward positions. Methods: In the present study, dates of birth of 6 663 players from four nations (Australia, England, New Zealand, South Africa) were analysed for relative age effects. Results: The hypothesis that RAEs would be more pronounced in back row players was not supported. South African rugby was an obvious outlier due to the finding that RAEs were present across all playing units. These results suggest that late maturing players have been disproportionately lost to the South African system across all positions. Conclusion: Nation-specific youth sport culture appears to be more important than playing position for determining who is at risk of RAEs in rugby union.

Shoulder Injuries in English Community Rugby Union.

The aim of this study was to describe the incidence, severity and type of shoulder injuries resulting from match play in adult community rugby union between 2009-2013. A total of 254 time-loss shoulder injuries were reported, an overall incidence of 2.2 per 1 000 h (95% CI: 1.9 to 2.4), and a mean injury severity of 9.5 weeks missed (95% CI: 8.2 to 10.8). The semi-professional group had an incidence of 2.8 injuries per 1 000 h (95% CI: 2.2 to 3.5), which was higher than the recreational group at 1.8 injuries per 1 000 h (95% CI: 1.4 to 2.2, p=0.004). The incidence of acromioclavicular joint injury for semi-professional players was 1.2 per 1 000 h (95% CI: 0.8 to 1.6); which was significantly higher than the incidence of this injury type in recreational players (0.5 per 1 000 h 95% CI: 0.3 to 0.7, p=0.002). Overall, back row players sustained the highest incidence of all shoulder injuries for a given playing position, 2.9 injuries per 1 000 h (95% CI: 2.2 to 3.6). The tackle was the main event associated with injury. Injury prevention programs and coaching strategies that consider tackle technique and physical conditioning of the shoulder region are therefore considered important.

The neuromuscular fatigue induced by repeated scrums generates instability that can be limited by appropriate recovery.

The aim of this study was to evaluate the influence of the fatigue on the machine scrum pushing sagittal forces during repeated scrums and to determine the origin of the knee extensor fatigue. Twelve elite U23 rugby union front row players performed six 6-s scrums every 30s against a dynamic scrum machine with passive or active recovery. The peak, average, and the standard deviation of the force were measured. A neuromuscular testing procedure of the knee extensors was carried out before and immediately after the repeated scrum protocol including maximal voluntary force, evoked force, and voluntary activation. The average and peak forces did not decrease after sixscrums with passive recovery. The standard deviation of the force increased by 70.2±42.7% (P<0.001). Maximal voluntary/evoked force and voluntary activation decreased (respectively 25.1±7.0%, 14.6±5.5%, and24±9.9%; P<0.001). The standard deviation of theforce did not increase with active recovery and was associated with lower decrease of maximal voluntary/evoked force and voluntary activation (respectively 12.8±7.9%, 4.9±6.5%, and 7.6±4.1%; all P<0.01). As a conclusion repeated scrummaging induced an increased machine scrum pushing instability associated with central and peripheral fatigue of the knee extensors. Active recovery seems to limit all these manifestations of fatigue.

Positional tackle and collision rates in Super Rugby

The aim of this study was to evaluate differences between playing positions regarding tackle and collision rates in a rugby game, and to determine the collision rates of individual playing positions in professional rugby union. Data from 30 matches (both teams involved) during the 2013 Super Rugby Season were captured and supplied by the Cheetahs Super Rugby Franchise, using the Verusco TryMaker Pro. Significant differences were found between positional groups regarding tackle rates. However, the front row players and second row players did not differ significantly (positions 1, 2, or 3 vs positions 4, or 5; p=0.0715 to p=0.6324). Within a positional group, only the difference between the inside centre and the other inside backs was significant (9 vs 12, p=0.0029; 10 vs 12, p=0.0045; 12 vs 13, p=0.0100). No significant differences were observed between second row players and the eighthman (4 vs 8, p=0.4183 and 5 vs 8, p=0.6863), although significant differences were found between second row players and the rest of the loose forwards (6 and 7). A significant difference (p≤0.05) occurred between all forwards and backs when collision rates were compared. The findings revealed significant inter-positional differences in tackling and collision rates within the same positional group.

An EMG assessment of Front Row Rugby Union Scrummaging

The rugby union scrum comprises of two distinct phases; the engagement and second shove. The engagement phase is achieved through the interlocking of opposition forward packs through front row players of each team. The current study analysed professional and amateur front row forwards for horizontal force production. EMG patterns and muscular activation were compared between groups during two distinct time points of the engagement phase, pre engagement to first contact and first contact to maximum horizontal force to determine their effects, if any on horizontal force production. Isokinetic strength data was collected from all players to investigate any relationship this had to horizontal force production during the engagement phase. Body mass was found to be significantly different between playing groups. Maximum horizontal force during the engagement phase was significantly different between groups, with professional players generating more than both amateur groups. EMG analysis presented no significant differences between groups for muscular activation patterns. Peak muscular activation for all recorded muscles was achieved prior to first contact. A significant correlation was found between muscular activation and max horizontal force for professional players only. Junior players were found to have a significant negative correlation between isokinetic strength and max horizontal force production.

THE EFFECT OF A PRE-BIND ENGAGEMENT TECHNIQUE ON THE BIOMECHANICAL CHARACTERISTICS OF RUGBY SCRUMMAGING ACROSS MULTIPLE PLAYING LEVELS

BackgroundThe Rugby Union scrum has evolved into a highly dynamic activity, particularly during engagement. Although catastrophic spinal injuries in rugby are extremely rare, approximately 40% of these are associated with...