Does installation of the backstroke start device reduce 15-m start time in swimming?

The purpose of this study was to determine the installation of the backstroke start device reduces 15-m time. Thirteen college swimmers participated in this study. The aerial start and underwater motions were recorded with two digital video cameras. The center of mass (CM) of the swimmer, angular displacements and velocities of the shoulder, hip and knee joints were calculated. As an indicator of performance, the 5- and 15-m times were measured. The 5- and 15-m times in the backstroke start device condition were significantly shorter than in the non-backstroke start device condition. The vertical velocities of the CM at hand-off and toe-off in the backstroke start device condition were significantly greater than in the non-backstroke start device condition, while there was no significant difference in the CM horizontal velocity at toe-off. As a result, the height of the great trochanter at entry of the fingertips, with the backstroke start device, was 15 cm higher than in the non-backstroke start device condition. In addition, the CM horizontal velocities at 5 m in the backstroke start device condition were significantly greater than those of the non-backstroke start device. Thus, the use of the backstroke start device may reduce the 15-m time by diminution of the entry area.     

Learning relay start strategies in swimming: What feedback is best?

In the past, studies and book recommendations on relay starts in swimming have been predominantly focused on the change-over time (COT) as a performance criterion. Aside from the circular backswing start with parallel foot placement, few studies have analysed differences in the take-off movement including step approaches as well. Although trends could be identified, the results remained still somewhat inconclusive. In contrast, no study has examined as has examined whether a reduction of COT in between wall contact of the income swimmer and the take-off of the outgoing swimmer is an optimal relay start strategy, as advocated by various swimming experts. Therefore, the purpose of this study was to compare two different relay start strategies: offensive strategy minimizing COT and conservative strategy to maximize horizontal peak force (HPF). In this regard, a learning intervention with 24 elite-level swimmers (12 females, 12 male) was conducted to compare both strategies regarding relay start time, HPF and COT. Subjects were randomly assigned to two feedback groups: COT versus HPF at take-off. The results of this study showed a clear advantage for HPF feedback for relay start performance measured by wall contact of the incoming swimmer and head passage at 7.5?m of the outgoing swimmer. In addition, similar reductions in COTs were found in both training groups. In conclusion, swimmers should focus on force production rather than minimizing COT. For the latter, deteriorating consequences for force production must be considered.     

Taxonomy of golf putting: Do different golf putting techniques exist?

Abstract

This study is a preliminary investigation into the use of cluster analysis to determine if different putting techniques existed in a group of club level golfers.

Putting at a hole 4?m away, the performances of 34 experienced golfers (age 55.3?±?17.8 years and handicap 15.3?±?6.9, range 3–27) were analysed using putter head kinematic and centre of pressure data. Two distinct putting techniques were identified (named as Arm putting and Body putting), this being the first time different putting techniques have been reported in the research literature. These techniques were defined by parameters related solely to movement of the centre of pressure along the line of the putt. Some players (17 of 34) moved between techniques when performing their putting trials. Neither technique produced more accurate putt results (P?=?0.783).

Putting technique was further analysed after grouping players according to handicap (similar skill level) or accuracy (similar putting performance). The lack of significant findings when players were re-analysed according to handicap or accuracy highlights the importance of the correct methodological approach to detecting technique differences.     

The effect of β-alanine supplementation on cycling time trials of different length

The varying results reported in response to β-alanine supplementation may be related to the duration and nature of the exercise protocol employed. We investigated the effects of β-alanine supplementation on a wide range of cycling performance tests in order to produce a clear concise set of criteria for its efficacy. Fourteen trained cyclists (Age?=?24.8?±?6.7?years; VO_2max?=?65.4?±?10.2 mL·kg·min^?1) participated in this placebo-controlled, double-blind study. Prior to supplementation, subjects completed two (familiarization and baseline) supramaximal cycling bouts until exhaustion (120% pre-supplementation VO_2max) and two 1-, 4- and 10-km cycling time trial (TT). Subjects then supplemented orally for 4 weeks with 6.4?g/d placebo or β-alanine and repeated the battery of performance tests. Blood lactate was measured pre-exercise, post-exercise and 5 min post-exercise. β-alanine supplementation elicited significant increases in time to exhaustion (TTE) (17.6?±?11.5 s; p?=?0.013, effect compared with placebo) and was likely to be beneficial to 4-km TT performance time (?7.8?±?8.1 s; 94% likelihood), despite not being statistically different (p?=?0.060). Performance times in the 1- and 10-km TT were not affected by treatment. For the highly trained cyclists in the current study, β-alanine supplementation significantly extended supramaximal cycling TTE and may have provided a worthwhile improvement to 4-km TT performance. However, 1- and 10-km cycling TT performance appears to be unaffected by β-alanine supplementation.     

Core executive functions are selectively related to different facets of motor competence in preadolescent children

Background: Although accumulating evidence suggests that motor and cognitive development is interrelated, only a few studies have investigated links between executive function and motor control. Therefore, the present cross-sectional study examined the relationship between motor competences and core components of executive functioning, including inhibitory control, working memory and cognitive flexibility. Methods: In 89 preadolescent children, motor competences were assessed using the MOBAK-5 test battery. Additionally, all participants completed computer-based versions of the Flanker task, which included standard and switch blocks, and the 2-Back task. Results: Partial correlations (correcting for age, gender and body mass index) revealed that locomotor skills were associated with the adjusted hit-rate on the 2-Back task (r?=?0.34) whereas object control was linked with conflict score on the Flanker task (r?=??0.39). In contrast, there was no correlation between switch costs and motor competences. Conclusion: In preadolescent children, high competences in locomotor skills and object control skills are associated with high performance on specific executive function tasks. This finding supports the current view that motor competences and cognitive control share some common underlying processes.     

Contribution of limbs’ actions to the four competitive swimming strokes: a nonlinear approach

The aim of our study was to assess the effect of the limbs’ actions on the nonlinear properties of the four competitive swimming strokes. Forty-nine swimmers performed all-out sprints at front-crawl, backstroke, breaststroke and butterfly, each one at full stroke (FS), only the arms’ stroke (AS), and only leg kicking (LK), in a total of 12 bouts, 6 per day. A speedo-meter cable was attached to the swimmer’s hip, to collect the speed-time raw data (f = 50Hz). Velocity, speed fluctuation, sample entropy and fractal dimension were derived from the speed-time series. Significant and moderate-strong effects were noted for both stroke and condition in all variables in the study (p ≤ 0.001; 0,560<η² < 0,952). The four competitive strokes and their three conditions exhibited nonlinear properties. The swimming pattern was less complex and more predictable for LK in comparison to AS and FS. Breaststroke and butterfly have more complex but more predictable patterns than backstroke and front-crawl.     

Is starting with the feet out of the water faster in backstroke swimming?

This study aimed to determine if starting with the feet above the water (FAW) in male backstroke swimming resulted in faster start times (15-m time) than when the feet were underwater (FUW). It was hypothesised that setting higher on the wall would generate increased horizontal force and velocity, resulting in quicker starts. Twelve high-level male backstrokers performed three trials of the FAW and FUW techniques. A biomechanical swimming testing system comprising one force plate (1,000 Hz), four lateral-view (100 Hz), and five overhead (50 Hz) video cameras captured the swimmers' performance. Data for each participant's fastest trial for each technique were collated, grouped, and statistically analysed. Analysis included Wilcoxon, Spearman Rho correlation, and regression analysis. Wilcoxon results revealed a significantly faster start time for the FAW technique (p < 0.01). Peak horizontal force was significantly smaller for FAW (p = 0.02), while take-off horizontal velocity was significantly greater (p = 0.01). Regression analysis indicated take-off horizontal velocity to be a good predictor of start time for both techniques, and the horizontal displacement of the centre of mass for the FAW start.     

Force–velocity property of leg muscles in individuals of different level of physical fitness

The present study explored the method of testing muscle mechanical properties through the linear force–velocity (F–V) relationships obtained from loaded vertical jumps. Specifically, we hypothesised that the F–V relationship parameters depicting the force, power, and velocity of the tested muscles will differ among individuals of different physical fitness. Strength trained, physically active, and sedentary male participants (N = 10 + 10 + 10; age 20–29 years) were tested on maximum countermovement and squat jumps where manipulation of external loads provided a range of F and V data. The observed F–V relationships of the tested leg muscles were approximately linear and mainly strong (median correlation coefficients ranged from 0.77 to 0.92; all p < 0.05), independently of either the tested group or the jump type. The maximum power revealed higher values in the strength trained than in the physically active and sedentary participants. This difference originated from the differences in F-intercepts, rather than from the V-intercepts. We conclude that the observed parameters could be sensitive enough to detect the differences among both the individuals of different physical fitness and various jump types. The present findings support using loaded vertical jumps and, possibly, other maximum performance multi-joint movements for the assessment of mechanical properties of active muscles.     

Logics of practice in movement culture: Lars-Magnus Engström’s contribution to understanding participation in movement cultures

In this article, we present a framework for exploring participation in and social stratification of movement culture based on Pierre Bourdieu’s concept logic of practice. The background to our approach is Lars-Magnus Engström’s struggle to understand the impact of social stratification on participation in movement culture in a now nearly fifty-year follow-up study. The aim of the article is to elaborate further a framework, which Engström drafted in one of his last publications. Here, we assume that participation in movement cultures is guided by a number of logics of practice that are historically, culturally and socially constituted, and which relate to people’s tastes in particular ways that lead to social stratification. These logics are grouped into three overarching kinds of practices: performing, improving and experiencing, which engender both practice and social stratification. Further, the different logics of practice are linked to a principle of uncertainty, which means that quantitative empirical data must be interpreted rather than measured in a strict sense. The here outlined framework suggests that future research about participation in movement culture needs to take into account information about the structure, rhythm and tempo of the practice, as well as of the directionality of the actions. Information about these issues can hopefully contribute to a more elaborated understanding of the impact of social stratification on participation in movement culture, and in what forms movements are pursued.     

The influence of the hand’s acceleration and the relative contribution of drag and lift forces in front crawl swimming

The aim of this study was to assess the effect of the hand’s acceleration on the propulsive forces and the relative contribution of the drag and lift on their resultant force in the separate phases of the front crawl underwater arm stroke. Ten female swimmers swam one trial of all-out 25-m front crawl. The underwater motion of each swimmer’s right hand was recorded using four camcorders and four periscope systems. Anatomical landmarks were digitised, and the propulsive forces generated by the swimmer’s hand were estimated from the kinematic data in conjunction with hydrodynamic coefficients. When the hand’s acceleration was taken into account, the magnitude of the propulsive forces was greater, with the exception of the mean drag force during the final part of the underwater arm stroke. The mean drag force was greater than the mean lift force in the middle part, while the mean lift force was greater than the mean drag force in the final part of the underwater arm stroke. Thus, swimmers should accelerate their hands from the beginning of their backward motion, press the water with large pitch angles during the middle part and sweep with small pitch angles during the final part of their underwater arm stroke.     

Comparison of different regression models to fit the force–velocity relationship of a knee extension exercise

The aims of this study were to compare the goodness of fit and the concurrent validity of three regression models of the force–velocity relationship in a unilateral knee extension exercise. The force–velocity relationship and the one-repetition-maximum load in the dominant and non-dominant leg were obtained in 24 male sports sciences students by a progressive protocol. Additionally, the maximum voluntary contraction (MVC) of the knee extensor muscles was recorded. Individual force–velocity relationships were obtained by the linear, quadratic polynomial and exponential regression models. Although the adjusted coefficients of determination of all three models were high, the polynomial model’s coefficient was slightly but significantly higher than the rest of the models (p < 0.05), while the standard error of estimate was slightly higher for the linear than for polynomial model (p = 0.001). MVC was underestimated by F ₀ calculated from the linear and polynomial models, while the maximum power was accurately estimated by the linear model. In summary, while the polynomial model revealed somewhat better fit, the linear model more accurately estimates the maximum power and provides the parameters of apparent physiological meaning. Therefore, we recommend using the linear model in research and routine testing of mechanical capacities of knee extensors.     

Jason Lezak again and again - linear mixed modelling analysis of change–over times in relay swimming races

The aim of this study was to examine the importance of the change-over time in swimming relay races. Top-class international 4 x 100 m freestyle races were analysed across a 10-year period including three Olympic Games and five European and World Championships. A total of 220 swimmers (116 female, 104 male) were included in this study with an average participation of 1.7 ± 1.2 races. To consider such repeated measurements and other factors (e.g., ranking in the relay race, position in the relay team) linear mixed models for longitudinal data were used for the statistical evaluation. Our results showed significantly longer change-over times for male medallists (0.23 ± 0.08 s) than non-medallists (0.20 ± 0.09 s) which reflects a very likely effect (94.2%). Furthermore, there were significant differences in change-over times between female and male swimmers depending on the current race positions. In total, the influence of change-over time on the final performance in 4 x 100-m freestyle relay appears to be overrated in previous studies.     

Weekday–weekend variations in mother-/father–child physical activity and screen time relationship: A cross-sectional study in a random sample of Czech families with 5- to 12-year-old children

This study assessed the associations between these factors in a random sample of Czech families with preschool and school-aged children. A nationally representative sample comprised 185 families with preschool children and 649 families with school-aged children (dyads; both parents and child n?=?365, mother and child n?=?730, and father and child n?=?469). The participants wore Yamax Digiwalker SW-200 pedometers at least four weekdays and both weekend days and completed family logbooks (anthropometric parameters, daily step counts (SC), and screen time (ST)). When a parent (fathers at weekends and mothers both on weekdays and at weekends) achieved 10,000 SC per day, their children were also significantly (OR?=?2.93–6.06, 95% CI?=?2.02–9.26) more likely to meet the daily SC recommendation. On the contrary, the involvement of fathers in organized leisure-time PA reduced their children's odds of meeting the SC recommendation on weekdays (OR?=?0.53, 95% CI?=?0.31–0.89) and at weekends (OR?=?0.41, 95% CI?=?0.24–0.72). The excessive ST of parents at weekends reduced the odds of their children meeting the SC recommendation (mother–child dyads: OR?=?0.44, 95% CI?=?0.26–0.72; father–child dyads: OR?=?0.63, 95% CI?=?0.37–1.06). High levels of parents’ PA contribute to the achievement of the recommended daily PA in children on weekdays and at weekends. Excessive weekend ST of parents reduces their odds of their children achieving the recommended daily PA; however, the influence of parents’ PA on their children’s achieving the recommended daily PA is stronger than the inhibitory effect of ST.     

Effects of unsteady conditions on propulsion generated by the hand’s motion in swimming: a systematic review

The understanding of swimming propulsion is a key factor in the improvement of performance in this sport. Propulsive forces have been quantified under steady conditions since the 1970s, but actual swimming involves unsteady conditions. Thus, the purpose of the present article was to review the effects of unsteady conditions on swimming propulsion based on studies that have compared steady and unsteady conditions while exploring their methods, their limitations and their results, as well as encouraging new studies based on the findings of this systematic review. A multiple database search was performed, and only those studies that met all eligibility criteria were included. Six studies that compared steady and unsteady conditions using physical experiments or numerical simulations were selected. The selected studies verified the effects of one or more factors that characterise a condition as unsteady on the propulsive forces. Consequently, much research is necessary to understand the effect of each individual variable that characterises a condition as unsteady on swimming propulsion, as well as the effects of these variables as a whole on swimming propulsion.     

“I’m a completely different person now”: Extraordinary experiences and personal transformations in sport

Many sport programs aim to positively impact participants’ lives, but there is little understanding of how sport leads to those changes. The purpose of this study was to examine an extraordinary experience and the participants’ interpretations of that experience as well as their feelings of personal transformation through the experience. In doing so, the authors developed an understanding of how sport can be used to create meaningful life changes at the individual level. Semi-structured interviews were conducted with 32 past participants of a long distance cycling ride that raised money and awareness for cancer research. Data analysis included three rounds of coding. Participants reported that the unusualness and sense of newness of the ride, the high levels of emotional intensity experienced, and the deep interpersonal connections developed led to a sense of empowerment and new meaning and purpose in life. Results indicate that extraordinary experiences contribute to lasting personal transformations, beyond intended behavior changes, within sport and out of sport. The characteristics of extraordinary experiences that contribute to personal transformation are discussed, as are suggestions for sport managers to leverage extraordinary experiences to create positive personal transformations.     

Physiological responses in different intensities of resistance exercise – Critical load and the effects of aging process

Aim was to identify critical load (CL) in young and elderly apparently healthy male cohorts. To contrast the metabolic, cardiovascular and perceptual responses on CL according to age. We evaluated 12 young (23 ± 3 years) and 10 elderly (70 ± 2 years) apparently healthy active males, who underwent: (1) 1 repetition maximum (1RM) test on a 45° Leg Press; (2) on different days, three high-intensity resistance exercise constant load tests (60%, 75% and 90% 1RM) until fatigue (Tlim). Absolute values of both the CL asymptote and curvature constant (kg) were significantly lower in elderly subjects (P < 0.05). In contrast, elderly subjects demonstrated a significantly higher number of repetitions at CL when compared with young subjects (P < 0.05). As expected, oxygen uptake (VO₂) and heart rate (HR) during maximal aerobic exercise testing were significantly reduced in older subjects. However, percent-predicted aerobic capacity were higher in older subjects (P < 0.05). In addition, blood lactate ([La^?]) corrected to Tlim and rating of perceived exertion values were greater in younger subjects at all intensities (P < 0.05). These findings, despite reduced force production in older subjects, endurance-related parameters are well preserved according to age-adjusted percent-predicted values in apparently healthy males.     

Test–retest reliability of second lactate turnpoint using two different criteria in competitive cyclists

Abstract

The aim of this study was to determine the relative and absolute reliability of second lactate turnpoint using fixed and individual blood lactate method in competitive cyclists. Twenty-eight male, well-trained cyclists (30.2 ± 10.1 years, 72.0 ± 7.4 kg, 177.3 ± 4.7 cm) were recruited to participate in this study. Cyclists completed two incremental cycling tests to exhaustion over a period of 7 days to determine their peak power output, maximal oxygen uptake, maximal heart rate, maximal blood lactate concentration and two lactate turnpoint criteria. The fixed blood concentration criterion (3.5 mM) and an individual criterion were assessed by a lactate-power curve, considering power output, heart rate and oxygen uptake. The main finding of this study was that both lactate turnpoint criteria showed identical low within-subject variation for power output (2.8% coefficient of variation). High values for test–retest correlations ranging from r = 0.70 to r = 0.94 were found for all variables in both threshold criteria. In conclusion, the individual and fixed method to determine the second lactate turnpoint showed similar high absolute and relative reliability in competitive cyclists.