Analysis of the relation between throwing speed and throwing accuracy in team-handball according to instruction

Abstract

This study examines the differences between expert and novice team-handball players in their sensitivity to instructions that emphasize speed or precision requirements. The effects of instructions on throwing speed and accuracy of a handball over arm throw and the speed–accuracy trade-off in experts and novices is revisited. An expert group (n=18) with a training experience of more than 10 years, and a novice group (n=24) without experience in team-handball, took part in the study. The participants were asked to throw to targets located at different positions following instructions emphasizing accuracy and instructions emphasizing accuracy and speed. Throwing speed was measured with a speed gun radar, and the centre of the ball when the ball entered the goal was digitalized for accuracy. Under these experimental conditions, the novice group was sensitive to instructions for reducing throwing speed and increasing accuracy when instructions emphasized accuracy. The expert group increased throwing speed when the instructions emphasized speed, but was not less accurate. The results indicate that it is advisable for experts’ speed to be close to maximum speed since it does not seem to have a significant effect on accuracy of the throw.     

Stimulus Velocity,Duration and Uncertainty as Determiners of Response Structure and Timing Accuracy

Abstract

The present experiments examined the effects of stimulus velocity, stimulus duration, and stimulus uncertainty on the spatial-temporal structure and timing accuracy of coincident timing responses. The results of Experiment 1 indicated that the response structure for aimed movements differed from that of ballistic movements but response accuracy was comparable for both movement conditions. However, when information concerning the stimulus velocity was provided, the responses to the faster stimuli (i.e., stimuli of shorter duration) appeared to be “speeded up” copies of those to slower stimuli and response accuracy increased as the stimulus velocity increased (i.e., stimulus duration decreased). When the stimulus velocity was not known, subjects initiated a common response for approximately 260 msec and response accuracy appeared to decrease as the stimulus velocity increased (i.e., stimulus duration decreased). Experiment 2 indicated that the stimulus duration rather than the stimulus velocity was the major determiner of both the spatial-temporal structure and timing accuracy and that a very fast and a very slow stimulus will be responded to similarly when the stimulus duration remains constant.     

Division,result and score margin alter the physical and technical performance of elite wheelchair tennis players

ABSTRACT

This study determined the physical and technical demands of elite wheelchair tennis (WT) match-play, how the demands differed between divisions (Men, Women, Quad) and the effect that set result and score margin had on these demands. Seventeen WT players were monitored during a singles competition. Physical measures of performance were analysed using an indoor tracking system and inertial measurement units. Technical measures of performance were examined using video analysis. Physical measures of performance differed by division (Men > Women > Quad) for most parameters. Rallies were longer during Men’s (P = 0.027) and Women’s (P = 0.004) matches compared to Quad’s and fewer shots were hit off 2 bounces in Men’s matches compared to Women’s and Quad’s (P ≤ 0.026). High-speed activity (HSA) increased during losing sets (P = 0.043). Most physical measures of performance increased by moderate to large effects during sets with a small score margin (≤3 games differential). Mean speed and HSA were similar during losing sets, regardless of margin, but decreased (large effects) when winning by a large margin. This study demonstrated the physical and technical demands that elite WT players need to be prepared for and how situational factors can influence these demands.     

Mental Rotation of Tactical Instruction Displays Affects Information Processing Demand and Execution Accuracy in Basketball

Purpose: In sports games, coaches often use tactic boards to present tactical instructions during time-outs (e.g., 20 s to 60 s in basketball). Instructions should be presented in a way that enables fast and errorless information processing for the players. The aim of this study was to test the effect of different orientations of visual tactical displays on observation time and execution performance. High affordances in visual-spatial transformation (e.g., mental rotation processes) might impede information processing and might decrease execution performance with regard to the instructed playing patterns. Method: In a within-subjects design with 1 factor, 10 novice students were instructed with visual tactical instructions of basketball playing patterns with different orientations either showing the playing pattern with low spatial disparity to the players’ on-court perspective (basket on top) or upside down (basket on bottom). Results: The self-chosen time for watching the pattern before execution was significantly shorter and spatial accuracy in pattern execution was significantly higher when the instructional perspective and the real perspective on the basketball court had a congruent orientation. Conclusion: The effects might be explained by interfering mental rotation processes that are necessary to transform the instructional perspective into the players’ actual perspective while standing on the court or imagining themselves standing on the court. According to these results, coaches should align their tactic boards to their players’ on-court viewing perspective.     

Effect of Overload Training Procedures upon Velocity and Accuracy of the Overarm Throw

Abstract

The study had two aspects: To determine the effect of warm-up throwing drills (employing “systematic overload”) upon subsequent speed and accuracy of the overarm throw in subjects with widely differing maximum velocities, and to determine the effect of a 6-week overload training (in which the speed and accuracy emphases were systematically varied) upon the speed and accuracy of the overarm throw.

The 60 subjects in the short-range phase of the study, examining the immediate effect of overload warm-up, received experimental treatments consisting of 10-oz., 15-oz., and regulation ball warm-up. The 48 subjects who participated in the long-range or training phase of the study received progressive overload in conjunction with various speed and/or accuracy emphases.

Computer services for this study were granted by the University of Wisconsin Research Committee through funds provided by the National Science Foundation and the Wisconsin Alumni Research Foundation.

The results of the study indicated that performance differences in throwing speed and accuracy, of high and low velocity performers that take place immediately following overload warm-up were statistically not significant. The initial speed and/or accuracy emphasis that was given appeared to have little effect on subsequent performance. The results provided no evidence that the use of a weighted ball resulted in immediate or long-range improvements in throwing speed or in throwing accuracy.     

Accuracy of Pedometer in Walking and Running

Abstract

Two experiments were conducted to examine the accuracy of mechanical pedometers in walking and running. Groups of 20 volunteer subjects were used in each experiment. In experiment 1, subjects wore 4 identical pedometers on the waist during six 1-mile walks on a motor driven treadmill, two at each of 3 speeds: 2, 3, and 4 mph. Experiment 2 required subjects wearing 5 pedometers to perform two 1-mile walks at their own pace under each of two different conditions: (1) on a 400 meter track and (2) along a jogging path over a measured mile. These subjects also completed two 1-mile runs at their own pace over the same measured mile course. In both experiments, a two-way ANOVA with replicates showed significant effects of subjects, condition (speed), and subjects-condition interaction. Test-retest reliability coefficients ranged from ?0.13 to 0.81. Results of these studies indicate that the ability of the mechanical pedometer to measure distance is inconsistent. The findings indicate that pedometers are more accurate for some individuals than others. Also their accuracy varies with the speed of walking and is different for walking compared to running.     

The effects of perceived and received support on self-confidence

Abstract

A sample of 222 university athletes (mean age 19.8 years, s = 2.0), ranging in standard from university second team to international competitor, completed a measure of perceived support 2 weeks before an important competition or match. On the day before the competition or match, the athletes completed measures of stressors, stress, received support, and self-confidence. Moderated hierarchical regression analyses revealed the following key findings: (i) main effects for both perceived (ΔR ² = 0.11) and received support (ΔR ² = 0.14) upon self-confidence; (ii) stress-buffering effects for both perceived (ΔR ² = 0.02) and received (ΔR ² = 0.07) support upon self-confidence; (iii) when both aspects of support were considered simultaneously, stress-buffering effects were primarily attributable to the influence of received support. These results demonstrate the beneficial impact of social support on self-confidence, both directly and by reducing the negative effect of stress on self-confidence. Our findings emphasize the need to recognize the distinction between perceived and received support, both in terms of theory and the design of social support interventions with athletes.     

Differences in ball speed and accuracy of tennis groundstrokes between elite and high-performance players

Abstract

The main aim of this study was to identify and compare ball speed and hitting accuracy of forehand and backhand groundstrokes between ATP professionals (elite) and high-performance youth players when shots were played cross-court and down the line to a target square. Six elite and seven high-performance tennis players volunteered to participate in the study. A Doppler-radar device and a digital video camera, operating at 120 frames per second, were used to measure ball speed and accuracy of forehand and backhand groundstrokes in the respective situation (cross-court and down the line). The results of 1040 measured groundstrokes indicate that the ball speed of the forehand and the backhand ground stroke was higher in the elite group when analysing (1) all valid shots, (2) the six fastest shots, and (3) the six most accurate shots (all P < 0.05). In addition, all players achieved a higher forehand speed compared with their backhand when balls were directed cross-court (P < 0.01). The participants demonstrated similar ability when considering accuracy of their groundstrokes (P > 0.05). However, a group difference for accuracy was identified when considering the six fastest forehand shots (P<0.05), and the forehand cross-court stroke was played more accurately than the backhand cross-court stroke by both groups (valid shots and six most accurate shots, P<0.05). Moreover, there was no evidence that players who impacted the ball faster were any less accurate than those who impacted the ball more slowly. Analyses for participants actually revealed a negative correlation between ball speed and mean radial error (accuracy) for the backhand down the line (r= ? 0.77, P<0.01). According to the results of this study, ball speed seems to be the determining factor that separates elite from sub-elite tennis players.     

Mental fatigue alters the speed and the accuracy of the ball in table tennis

ABSTRACT

This study aimed at evaluating the effects of mental and muscle fatigue on table tennis performance. Mental fatigue (MF) was induced by completion of 90 minutes of the AX-CPT; muscle fatigue was induced by completion of an eccentric exercise performed with the elbow flexors (biceps fatigue, BF) or the knee extensors (quadriceps fatigue, QF). The control condition consisted of watching a movie. Stroke parameters (speed and accuracy of the ball), as well as feelings of fatigue and force production capacity of the elbow flexors (BF, MF and control conditions) and knee extensors (QF condition), were assessed pre and post fatigue protocols. Feelings of fatigue increased post fatigue protocols. Force production capacity decreased only in the BF and QF conditions. BF and MF induced a decrease in accuracy. This decrease in accuracy was associated with an increased ball speed in the BF condition, and a decreased ball speed in the MF condition. QF had a negligible effect on stroke performance. Our results suggest that both mental fatigue, and muscle fatigue, significantly impair table tennis performance and therefore coaches should take into account both the physical and mental state of table tennis players to optimize performance.     

Effects of Instructional Physical Activity Courses on Overall Physical Activity and Mood in University Students

Purpose: The aim of this research was to assess the association between university-based instructional physical activity (PA) courses and changes in overall PA levels and negative mood and their interrelations. The study also sought to determine the amount of change in PA required to significantly improve mood in course enrollees. Method: Participants were university students initially completing PA below the level recommended for health who were either presently enrolled in an elective instructional PA course (treatment group, n = 52, 69% female) or not presently enrolled in such a course (comparison group, n = 32, 69% female). Validated surveys assessed volumes of PA completed per week and overall negative mood from baseline to course end. Mediation analyses assessed group effects on mood through PA changes and reciprocal relations between PA and mood changes. Results: There was a significantly greater increase in PA and significantly more reduction in negative mood in the treatment group. Change in PA completely mediated the relationship between group and change in negative mood, and change in mood completely mediated the relationship between group and PA. These findings indicated a reciprocal, mutually reinforcing relationship between changes in PA and mood. An increase in PA of at least 2 days/week was associated with a significant reduction in negative mood, with no greater effect for more increase. Conclusions: Results provided an improved understanding of the effects of university-based instructional PA courses and how they might be leveraged to improve students’ mental health and possibly contribute to their academic success.     

A Golf Knowledge Test

Abstract

Gymnastics coaches typically place their gymnasts in a rank order from poorest to best for competition in each event. The purpose of this investigation was to determine if the scores of nationally certified gymnastics judges were influenced by this expected placement of gymnasts within a team order of competition. The Team Optional Session of the 1973 Big Eight Gymnastics Meet was videotaped. Twelve nationally certified gymnastics judges, randomly selected from within three geographical locations of the United States, scored gymnastics routines on each of two sets of videotapes, edited from the original tapes, in two sessions separated by 48 hr. The videotapes were so edited that within-team orders of competition were reversed in one or the other of the two sets of videotapes for selected teams in each event. In this manner, scores were collected for 40 routines, each of which appeared both first and fourth in the withinteam orders of competition. A 2 × 12 × 2 ANOVA revealed that (1) a gymnast performing the same routine is at a significant (p < .05) scoring advantage if he is judged as the fourth competitor for his team rather than the first competitor, and (2) regional differences existed among the scores awarded by gymnastics judges.     

Task Classification and Strategy Utilization in Motor Skills

Abstract

A task classification scheme was developed in accordance with a conceptual model of motor behavior. The scheme suggests that motor skills be categorized as to the processing demands placed on a learner, feedback availability, and pacing conditions. Additionally, potential learner strategies were identified and defined in relation to both the model and the classification scheme. Consideration was given to the fact that strategies should be taught in addition to movement skills. Ultimately, appropriate strategies should be self-generated. Recommendations were provided for the consideration of task-learner-strategy interactions in the design of instructional material and development of instructional programs.     

Visual Search and Biological Motion Perception in Tennis

Purpose

The purposes of this study were to: (a) examine the effect of experience and goal constraints (speed, accuracy) on kicking patterns; (b) determine if effective striking mass was independent of ankle velocity at impact; and (c) determine the accuracy of kicks relative to independent factors.

Method

Twenty participants were recruited to kick at 3 different velocities with and without an accuracy requirement. Multivariate analysis of variance determined if relative timing of joint angular velocities changed during the kick. Chi-square analysis determined if calculated effective mass was independent of ankle velocity at impact. Analysis of variance (ANOVA) was used to examine differences in absolute constant error and variable error according to independent factors.

Results

Results indicated that experience and speed affect absolute timing of joint velocities with no changes in the relative timing of peak joint velocity across independent factors. Chi-square analysis indicated that calculated effective mass is not independent of ankle velocity. ANOVA indicated that experienced performers displayed less variability error than did inexperienced performers.

Conclusion

It was concluded that: (a) Experience, velocity, and accuracy do not affect the relative timing of kicks; (b) kickers trade ankle velocity at impact for greater effective striking mass and ball velocity; and (c) variability in ball placement is affected by experience.     

Influence of free surface,unsteadiness and viscous effects on oar blade hydrodynamic loads

Abstract

Flow around a rowing blade is a very complex phenomenon, involving unsteady three-dimensional flow with violent motion of the free surface. However, in the literature, forces acting on blades are modelled using extreme and dubious simplifications. The aim of the present study was to evaluate the influence of free surface and unsteadiness (two physical characteristics that are commonly neglected when modelling loads on blades) as well as viscous effects. In fact, quasi-static approaches are often used, with no influence of the free surface effects. To conduct this study, computational fluid dynamics is used, supported by experimental results performed with a dedicated device reproducing a simplified rowing stroke in the towing tank. Comparisons show that both free surface flow and unsteadiness must be considered to capture the whole physics of the phenomenon accurately. In contrast, the viscous effects have a very limited influence.     

Errata

Abstract

One hundred and eighteen national collegiate fencers engaged in the first round competition in the 28th annual NCAA Fencing Championships held at the University of Illinois, Chicago Circle Campus. After the first day of competition, the field size was reduced to 72 fencers or 24 fencers per weapon. Through the use of a unique scoring device, response times and accuracy measurements were recorded for each fencer. The fencers then engaged in their respective round robin tournament according to class of weapon; epee, sabre, or foil. Two criterion measures of fencing success were then correlated with response times and accuracies. Correlation coefficients for sabre fencemen were slightly better than 0. Criterion measures for epee fencers showed a low relationship with response time and accuracies while those of foil showed a slight to fair relationship.     

Maximizing recovery time between knock-out races improves sprint cross-country skiing performance

Background:In a sprint cross-country(XC)ski competition,the difference in recovery times separating the first and the second semi-final(SF)heats from the final(F)may affect performance.The aim of the current study was to compare the effects of longer vs.shorter recovery periods prescribed between the 3 knock-out races of a simulated sprint XC ski competition involving a prologue(P),quarter-final(QF),SF,and F.Methods:Eleven well-trained XC ski athletes completed 2 simulated sprint XC ski competitions on a treadmill involving 4×883-m roller-ski bouts at a 4°incline using the gear 3 ski-skating sub-technique.The first 3 bouts were completed at a fixed speed(PFIX,QFFIX,and SFFIX)corresponding to~96%of each individual’s previously determined maximal effort.The final bout was performed as a self-paced sprint time trial(FSTT).Test conditions differed by the time durations prescribed between the QFFIX,SFFIX,and FSTT,which simulated real-world XC ski competition conditions using maximum(MAX-REC)or minimum(MIN-REC)recovery periods.Results:The FSTT was completed 5.4±5.5 s faster(p=0.009)during MAX-REC(179.2±18.1 s)compared to MIN-REC(184.6±20.0 s),and this was linked to a significantly higher power output(p=0.010)and total metabolic rate(p=0.009).The pre FSTT blood lactate(BLa)concentration was significantly lower during MAX-REC compared to MIN-REC(2.5±0.8 mmol/L vs.3.6±1.6 mmol/L,respectively;p=0.027),and the pre-to-post FSTT increase in BLa was greater(8.8±2.1 mmol/L vs.7.1±2.3 mmol/L,respectively;p=0.024).No other differences for MAX-REC vs.MIN-REC reached significance(p>0.05).Conclusion:Performance in a group of well-trained XC skiers is negatively affected when recovery times between sprint heats are minimized which,in competition conditions,would occur when selecting the last QF heat.This result is combined with a higher pre-race BLa concentration and a reduced rise in BLa concentration under shorter recovery conditions.These findings may help inform decision making when XC skiers are faced with selecting a QF heat within a sprint competition.     

Environmental and venue-related factors affecting the performance of elite male track athletes

Abstract

The effects of environmental and other venue-related factors need to be taken into account when tracking an individual athlete's competitive performance. We report the effects of such factors on the performances of elite male track athletes. Performance times throughout the athletic careers of male track athletes placed in the top 16 of their event in at least one Olympic Games or World Championship between 2000 and 2009 were downloaded from the athletics results database at tilastopaja.org. In the 10 running events (100 m through 10,000 m, including hurdles and steeplechase), there were 619 athletes with 43,999 performances, all with enviromental and venue-related information. Times for a given event were log-transformed to estimate percent effects in a mixed linear model with fixed effects for the environmental and venue-related factors and random effects for within-athlete race-to-race variability and individual athlete performance progression. After adjustment for quadratic trends for year of competition and each athlete's age, the model provided estimates of effects of standard of competition (Olympics and World Championships vs other competitions), altitude (sea level vs ≥ 1000 m), timing method (electronic vs stopwatch), wind speed (greater than vs less than 2 m · s^–1), and venue (outdoors vs indoors). Uncertainty in estimates of environmental effects expressed as 99% confidence limits was sufficiently small (at most ±0.9%) for almost all outcomes to be clear when interpreted in relation to smallest important changes (0.3–0.5%). Olympics and World Championships produced substantially faster times for events up to 400 m (0.7–0.8%) but slower times for the 1500 m, 5000 m, and 10,000 m events (0.6%, 1.2%, and 0.2% respectively), presumably reflecting differences in preparation or pacing. Altitude produced substantially faster times in some 100 m, 200 m, 400 m, and hurdle events (0.1–0.5%) but substantially slower times in longer races (1.1–2.4%), reflecting opposing effects of altitude on air resistance and aerobic power. Stopwatch times were faster for sprints (0.3–0.5%) but slower for 1500 m and longer events (0.6–2.1%), possibly because of bias in reaction time and confounding by standard of competition. A typical trailing wind of 2 m · s^–1 conferred small benefits (0.5–0.8%) on the three sprint events where wind speed was recorded. Indoor events were consistently slower (1.6–2.3%), a likely consequence of tight bends. In conclusion, use of these environmental and venue-related effects to adjust performances of male track athletes will make comparative assessment of all their performances more meaningful.     

Pretask Speed Training and Movement Complexity

Abstract

The purpose of the study was to determine the effects of pretask speed training and movement complexity on skill acquisition using the rotary pursuit. The study was a two-part investigation utilizing subjects from two different schools. The data from each school were analyzed separately with slight procedural differences made in the second investigation. The first study included 72 third graders; 90 third and fourth graders were in the second investigation. Both studies used a pretask training period of three days and a testing period of three additional days. A criterion speed of 50 rpm was used in the first study; 40 rpm was used in the second study. Three pretask training groups were used: one trained at the criterion speed and the other two using a gradual build-up of speeds with one being closer to the criterion than the other. The complexity dimension was studied by using a circle, square, or triangle top plate on the rotary pursuit. Both investigations used a 3 × 3 × 3 factorial ANOVA with repeated measures on the last factor (days). Although differences were found in performance over the test days according to the type of pretask training, the days × speed interaction indicated that by the fourth and fifth day the only group performing significantly poorer (p < .05) was the group trained at a very slow speed in relationship to the criterion speed. The complexity × speed interaction was not significant (p > .05) indicating no differential effects for these two factors.     

Optimal sampling frequency in recording of resistance training exercises

The purpose of this study was to analyse the raw lifting speed collected during four different resistance training exercises to assess the optimal sampling frequency. Eight physically active participants performed sets of Squat Jumps, Countermovement Jumps, Squats and Bench Presses at a maximal lifting speed. A linear encoder was used to measure the instantaneous speed at a 200 Hz sampling rate. Subsequently, the power spectrum of the signal was computed by evaluating its Discrete Fourier Transform. The sampling frequency needed to reconstruct the signals with an error of less than 0.1% was f_99.9 = 11.615 ± 2.680 Hz for the exercise exhibiting the largest bandwidth, with the absolute highest individual value being 17.467 Hz. There was no difference between sets in any of the exercises. Using the closest integer sampling frequency value (25 Hz) yielded a reconstruction of the signal up to 99.975 ± 0.025% of its total in the worst case. In conclusion, a sampling rate of 25 Hz or above is more than adequate to record raw speed data and compute power during resistance training exercises, even under the most extreme circumstances during explosive exercises. Higher sampling frequencies provide no increase in the recording precision and may instead have adverse effects on the overall data quality.     

Peak movement and collision demands of professional rugby league competition

ABSTRACT

To quantify the peak movement and contact demands of National Rugby League (NRL) and European Super League (ESL) competition players were tracked during 10 NRL (166 files) and 10 ESL (143 files) matches using microtechnology devices. The peak 1- to 5-min periods were then calculated for average match speed (m·min^?1), and acceleration (m·s^?2) when 0, 1, 2, and ≥3 collisions per min occurred. Linear mixed effect models and Cohen’s effect size statistic (± 90%CI) were used to determine the differences in movement profiles when collisions occurred. Compared to no collision periods, as frequency of collisions per minute increased, there were progressive reductions in running speed for most positional groups. The addition of 1 or more collisions per min resulted in average effect size reductions in match speed of ?0.14 for NRL forwards, ?0.89 for NRL backs, ?0.48 for ESL forwards, and ?2.41 for ESL backs. ESL forwards had the highest frequency of peak periods involving 3 or more collisions per min, 22% of all periods, followed by NRL forwards (14%), NRL backs (10%) and ESL backs (8%). This study highlights the peak movement and collision demands of professional rugby league competition and allows practitioners to develop training drills that reflect worst case scenarios.