Outsourcing Swimming Education-Experiences and Challenges.

In Norway, swimming and lifesaving education (swimming education) is an obligatory part of physical education, with explicit learning aims after grade four. After recent reports of Norwegian pupils achieving low scores in swimming abilities, the Government has outlined strategies for improving swimming education. There is a notable trend toward using external providers in delivering swimming education. This article examines the outsourcing of swimming education in Norwegian primary schools. Eighteen semi-structured interviews were conducted with school leaders, physical education teachers and swimming instructors involved in outsourcing arrangements. The outsourcing was organized through private providers, municipalities, or local swimming clubs. Data were analyzed thematically and separated into highlighted areas of outsourcing practices. The results showed that outsourcing may be a solution for schools that lack staff with swimming experience and knowledge. It also indicates that teacher courses, professional development through collaboration, and strategies for measuring quality would improve swimming education.

Perceived Versus Real Swimming Skills of Adolescents Under Standard and Challenging Conditions: Exploring Water Competencies as an Approach to Drowning Prevention.

In this study, we compared adolescents' actual (expert assessed) front crawl swimming skills to their self-assessment in two conditions: in standard swimming (wearing a swimsuit and goggles) and in a simulated risk scenario (swimming in plain clothes without goggles). We postulated that education focused on water competencies is fundamental in preventing drownings. Experts evaluated the skills of 21 female and 21 male adolescents in both standard and challenging conditions. All were low-skilled swimmers aged 14-15 years. Participants were asked to self-assess their skills before and after each trial. Boys and girls covered the same distance in both trials. Their self-assessment did not change regardless of the difficulty of the conditions. Girls assessed themselves more accurately than boys. However, boys who underestimated their skills showed greater ability to utilise the experience gained from performing the task for a more accurate self-assessment. In conclusion, adolescents should be educated in total water competencies, and not merely in swimming skills. For girls, "water readiness" is thought to broaden their ability to adapt their swimming skills to nonstandard conditions. Aquatic education for boys should focus on developing self-reflection in order to create a long-lasting responsibility using their own swimming skills.

Muscle Activation in World-Champion, World-Class, and National Breaststroke Swimmers.

PURPOSE: To investigate the muscle-activation patterns and coactivation with the support of kinematics in some of the world's best breaststrokers and identify performance discriminants related to national elites at maximal effort. METHODS: Surface electromyography was collected in 8 muscles from 4 world-class (including 2 world champions) and 4 national elite breaststroke swimmers during a 25-m breaststroke at maximal effort. RESULTS: World-class spent less time during the leg recovery (P = .043), began this phase with a smaller knee angle (154.6° vs 161.8°), and had a higher median velocity of 0.18 m/s during the leg glide than national elites. Compared with national elites, world-class swimmers showed a difference in the muscle-activation patterns for all 8 muscles. In the leg-propulsion phase, there was less triceps brachii activation (1 swimmer 6% vs median 23.0% [8.8]). In the leg-glide phase, there was activation in rectus femoris and gastrocnemius during the beginning of this phase (all world-class vs only 1 national elite) and a longer activation in pectoralis major (world champions 71% [0.5] vs 50.0 [4.3]) (propulsive phase of the arms). In the leg-recovery phase, there was more activation in biceps femoris (50.0% [15.0] vs 20.0% [14.0]) and a later and quicker activation in tibialis anterior (40.0% [7.8] vs 52.0% [6.0]). In the stroke cycle, there was no coactivation in tibialis anterior and gastrocnemius for world champions. CONCLUSION: These components are important performance discriminants. They can be used to improve muscle-activation patterns and kinematics through the different breaststroke phases. Furthermore, they can be used as focus points for teaching breaststroke to beginners.

Muscle coordination, activation and kinematics of world-class and elite breaststroke swimmers during submaximal and maximal efforts.

The aims of this study were to describe muscular activation patterns and kinematic variables during the complete stroke cycle (SC) and the different phases of breaststroke swimming at submaximal and maximal efforts. Surface electromyography (sEMG) was collected from eight muscles in nine elite swimmers; five females (age 20.3 ± 5.4 years; Fédération Internationale de Natation [FINA] points 815 ± 160) and four males (27.7 ± 7.1 years; FINA points 879 ± 151). Underwater cameras were used for 3D kinematic analysis with automatic motion tracking. The participants swam 25 m of breaststroke at 60%, 80% and 100% effort and each SC was divided into three phases: knee extension, knee extended and knee flexion. With increasing effort, the swimmers decreased their SC distance and increased their velocity and stroke rate. A decrease during the different phases was found for duration during knee extended and knee flexion, distance during knee extended and knee angle at the beginning of knee extension with increasing effort. Velocity increased for all phases. The mean activation pattern remained similar across the different effort levels, but the muscles showed longer activation periods relative to the SC and increased integrated sEMG (except trapezius) with increasing effort. The muscle activation patterns, muscular participation and kinematics assessed in this study with elite breaststroke swimmers contribute to a better understanding of the stroke and what occurs at different effort levels. This could be used as a reference for optimising breaststroke training to improve performance.

Muscle coordination during breaststroke swimming: Comparison between elite swimmers and beginners.

The present study aimed to compare muscle coordination strategies of the upper and lower limb muscles between beginners and elite breaststroke swimmers. Surface electromyography (EMG) of eight muscles was recorded in 16 swimmers (8 elite, 8 beginners) during a 25 m swimming breaststroke at 100% of maximal effort. A decomposition algorithm was used to identify the muscle synergies that represent the temporal and spatial organisation of muscle coordination. Between-groups indices of similarity and lag times were calculated. Individual muscle patterns were moderately to highly similar between groups (between-group indices range: 0.61 to 0.84). Significant differences were found in terms of lag time for pectoralis major (P < 0.05), biceps brachii, rectus femoris and tibialis anterior (P < 0.01), indicating an earlier activation for these muscles in beginners compared to elites (range: -13.2 to -3.8% of the swimming cycle). Three muscle synergies were identified for both beginners and elites. Although their composition was similar between populations, the third synergy exhibited a high within-group variability. Moderate to high indices of similarity were found for the shape of synergy activation coefficients (range: 0.63 to 0.88) but there was a significant backward shift (-8.4% of the swimming cycle) in synergy #2 for beginners compared to elites. This time shift suggested differences in the global arm-to-leg coordination. These results indicate that the synergistic organisation of muscle coordination during breaststroke swimming is not profoundly affected by expertise. However, specific timing adjustments were observed between lower and upper limbs.

Breaststroke swimmers moderate internal work increases toward the highest stroke frequencies.

A model to predict the mechanical internal work of breaststroke swimming was designed. It allowed us to explore the frequency-internal work relationship in aquatic locomotion. Its accuracy was checked against internal work values calculated from kinematic sequences of eight participants swimming at three different self-chosen paces. Model predictions closely matched experimental data (0.58 ± 0.07 vs 0.59 ± 0.05 J kg(-1)m(-1); t(23)=-0.30, P=0.77), which was reflected in a slope of the major axis regression between measured and predicted total internal work whose 95% confidence intervals included the value of 1 (ß=0.84, [0.61, 1.07], N=24). The model shed light on swimmers ability to moderate the increase in internal work at high stroke frequencies. This strategy of energy minimization has never been observed before in humans, but is present in quadrupedal and octopedal animal locomotion. This was achieved through a reduced angular excursion of the heaviest segments (7.2 ± 2.9° and 3.6 ± 1.5° for the thighs and trunk, respectively, P<0.05) in favor of the lightest ones (8.8 ± 2.3° and 7.4 ± 1.0° for the shanks and forearms, respectively, P<0.05). A deeper understanding of the energy flow between the body segments and the environment is required to ascertain the possible dependency between internal and external work. This will prove essential to better understand swimming mechanical cost determinants and power generation in aquatic movements.

Different Muscle-Recruitment Strategies Among Elite Breaststrokers.

PURPOSE: To investigate electromyographical (EMG) profiles characterizing the lower-limb flexion-extension in an aquatic environment in high-level breaststrokers. METHODS: The 2-dimensional breaststroke kick of 1 international- and 2 national-level female swimmers was analyzed during 2 maximal 25-m swims. The activities of biceps femoris, rectus femoris, gastrocnemius, and tibialis anterior were recorded. RESULTS: The breaststroke kick was divided in 3 phases, according to the movements performed in the sagittal plane: push phase (PP) covering 27% of the total kick duration, glide phase (GP) 41%, and recovery phase (RP) 32%. Intrasubject reproducibility of the EMG and kinematics was observed from 1 stroke cycle to another. In addition, important intersubject kinematic reproducibility was noted, whereas muscle activities discriminated the subjects: The explosive PP was characterized by important muscle-activation peaks. During the recovery, muscles were likewise solicited for swimmers 1 (S1) and 2 (S2), while the lowest activities were observed during GP for S2 and swimmer 3 (S3), but not for S1, who maintained major muscle solicitations. CONCLUSIONS: The main muscle activities were observed during PP to perform powerful lower-limb extension. The most-skilled swimmer (S1) was the only 1 to solicit her muscles during GP to actively reach better streamlining. Important activation peaks during RP correspond to the limbs acting against water drag. Such differences in EMG strategies among an elite group highlight the importance of considering the muscle parameters used to effectively control the intensity of activation among the phases for a more efficient breaststroke kick.

Surface electromyographic measurements on land prior to and after 90 min of submersion (swimming) are highly reliable.

The purpose of this study was to investigate the reliability of surface electromyography (sEMG) measurements after submersion (swimming) for 90min. Isometric maximal voluntary contractions (MVC) on land and in water were collected from eight muscles on the right side of the body in 12 healthy participants (6 women and 6 men). Repeated measures analyses of variance (general linear model ANOVA) showed no significant differences in the peak amplitude MVC scores between land pre and post measurements for all muscles, p>.05. The mean of the Intraclass correlation coefficient (1,1) for land pre and land post was .985 with (95% Cl=.978-.990), for land pre and water pre .976 (95% Cl=.964-.984) and for land pre and post, water pre and post .981 (95% Cl=.974-.987). Measuring sEMG on land before and after a prolonged submersion is highly reliable without additional waterproofing when using electrodes with 57mm diameter.

Critical evaluation of oxygen-uptake assessment in swimming.

Swimming has become an important area of sport science research since the 1970s, with the bioenergetic factors assuming a fundamental performance-influencing role. The purpose of this study was to conduct a critical evaluation of the literature concerning oxygen-uptake (VO2) assessment in swimming, by describing the equipment and methods used and emphasizing the recent works conducted in ecological conditions. Particularly in swimming, due to the inherent technical constraints imposed by swimming in a water environment, assessment of VO2max was not accomplished until the 1960s. Later, the development of automated portable measurement devices allowed VO2max to be assessed more easily, even in ecological swimming conditions, but few studies have been conducted in swimming-pool conditions with portable breath-by-breath telemetric systems. An inverse relationship exists between the velocity corresponding to VO2max and the time a swimmer can sustain it at this velocity. The energy cost of swimming varies according to its association with velocity variability. As, in the end, the supply of oxygen (whose limitation may be due to central-O2 delivery and transportation to the working muscles-or peripheral factors-O2 diffusion and utilization in the muscles) is one of the critical factors that determine swimming performance, VO2 kinetics and its maximal values are critical in understanding swimmers' behavior in competition and to develop efficient training programs.

High-intensity interval training improves VO(2peak), maximal lactate accumulation, time trial and competition performance in 9-11-year-old swimmers.

Training volume in swimming is usually very high when compared to the relatively short competition time. High-intensity interval training (HIIT) has been demonstrated to improve performance in a relatively short training period. The main purpose of the present study was to examine the effects of a 5-week HIIT versus high-volume training (HVT) in 9-11-year-old swimmers on competition performance, 100 and 2,000 m time (T(100 m) and T(2,000 m)), VO(2peak) and rate of maximal lactate accumulation (Lac(max)). In a 5-week crossover study, 26 competitive swimmers with a mean (SD) age of 11.5 ± 1.4 years performed a training period of HIIT and HVT. Competition (P < 0.01; effect size = 0.48) and T(2,000 m) (P = 0.04; effect size = 0.21) performance increased following HIIT. No changes were found in T(100 m) (P = 0.20). Lac(max) increased following HIIT (P < 0.01; effect size = 0.43) and decreased after HVT (P < 0.01; effect size = 0.51). VO(2peak) increased following both interventions (P < 0.05; effect sizes = 0.46-0.57). The increases in competition performance, T(2,000 m), Lac(max) and VO(2peak) following HIIT were achieved in significantly less training time (~2 h/week).

Added mass in human swimmers: age and gender differences.

In unstationary swimming (changing velocity), some of the water around the swimmer is set in motion. This can be thought of as an added mass (M(a)) of water. The purpose of this study was to find added mass on human swimmers and investigate the effect of shape and body size. Thirty subjects were connected to a 2.8m long bar with handles, attached with springs (stiffness k = 318 N/m) and a force cell. By oscillating this system vertically and registering the period of oscillations it was possible to find the added mass of the swimmer, given the known masses of the bar and swimmer. Relative added mass (M(a)%) for boys, women and men were, respectively, 26.8 +/- 2.9%, 23.6 +/- 1.6% and 26.8 +/- 2.3% of the subjects total mass. This study reported significantly lower added mass (p < 0.001) and relative added mass (p < 0.002) for women compared to men, which indicate that the possible body shape differences between genders may be an important factor for determining added mass. Boys had significantly lower (p < 0.001) added mass than men. When added mass was scaled for body size there were no significant differences (p = 0.996) between boys and men, which indicated that body size is an important factor that influences added mass. The added mass in this study seems to be lower and within a smaller range than previously reported (Klauck, 1999; Eik et al., 2008). It is concluded that the added mass in human swimmers, in extended gliding position, is approximately 1/4 of the subjects' body mass.

Combined strength and endurance training in competitive swimmers.

A combined intervention of strength and endurance training is common practice in elite swimming training, but the scientific evidence is scarce. The influences between strength and endurance training have been investigated in other sports but the findings are scattered. Some state the interventions are negative to each other, some state there is no negative relationship and some find bisected and supplementary benefits from the combination when training is applied appropriately. The aim of this study was to investigate the impact of a combined intervention among competitive swimmers. 20 subjects assigned to a training intervention group (n = 11) or a control group (n = 9) from two different teams completed the study. Anthropometrical data, tethered swimming force, land strength, performance in 50m, 100m and 400m, work economy, peak oxygen uptake, stroke length and stroke rate were investigated in all subjects at pre- and post-test. A combined intervention of maximal strength and high aerobic intensity interval endurance training 2 sessions per week over 11 weeks in addition to regular training were used, while the control group continued regular practice with their respective teams. The intervention group improved land strength, tethered swimming force and 400m freestyle performance more than the control group. The improvement of the 400m was correlated with the improvement of tethered swimming force in the female part of the intervention group. No change occurred in stroke length, stroke rate, performance in 50m or 100m, swimming economy or peak oxygen uptake during swimming. Two weekly dry-land strength training sessions for 11 weeks increase tethered swimming force in competitive swimmers. This increment further improves middle distance swimming performance. 2 weekly sessions of high- intensity interval training does not improve peak oxygen uptake compared with other competitive swimmers. Key pointsTwo weekly sessions of dry land strength training improves the swimming force.Two weekly sessions of high-intensity endurance training did not cause improved endurance capacity.It may seem that dry land strength training can improve middle distance performance.

Drag characteristics of competitive swimming children and adults.

The aims of this study were to compare drag in swimming children and adults, quantify technique using the technique drag index (TDI), and use the Froude number (Fr) to study whether children or adults reach hull speed at maximal velocity (vmax). Active and passive drag was measured by the perturbation method and a velocity decay method, respectively, including 9 children aged 11.7+/-0.8 and 13 adults aged 21.4+/-3.7. The children had significantly lower active (kAD) and passive drag factor (kPD) compared with the adults. TDI (kAD/kPD) could not detect any differences in swimming technique between the two groups, owing to the adults swimming maximally at a higher Fr, increasing the wave drag component, and masking the effect of better technique. The children were found not to reach hull speed at vmax, and their Fr were 0.37+/-0.01 vs. the adults 0.42+/-0.01, indicating adults' larger wave-making component of resistance at vmax compared with children. Fr is proposed as an evaluation tool for competitive swimmers.

Factors affecting swimming economy in children and adults.

The aim of this study was to examine the influence of several explanatory factors: anthropometry, buoyancy, passive underwater torque, drag and swimming technique on the energy cost of swimming front crawl in children and adults. Submaximal V(.)O(2) was measured in ten children (age 12) and 13 adults (age 21), as well as body length (BL), body mass, arm length, propelling size, active drag, hydrostatic lift, passive torque, intracyclic velocity fluctuation, hand slip, stroke length and body angle. The results show that body length ( r=0.74), body mass ( r=0.86) propelling size ( r=0.61), arm length ( r=0.66), distance between the center of mass and the center of volume (Delta d, r=0.74) and body angle during swimming ( r=-0.56) all showed significant linear relationships with the cost of swimming at 1.0 m x s(-1) (CS(1.0)). When normalizing the cost of swimming to body size (CS(1.0) x BL(-1)) there were no differences between the two groups. The conclusions of this study are that the combination of BL, body mass, active drag factor, passive torque, drag efficiency and hydrostatic lift were able to explain 97% of the variation in the cost of swimming for the whole group of swimmers. The size-independent factors of torque and floating abilities (density and Delta d in % of BL), together with swimming technique and active drag were found to explain 75% of the variations in CS(1.0) x BL(-1). The identical values for CS(1.0) x BL(-1) for children and adults are explained through the opposing effects of a better swimming technique in the adults, and a better passive torque in the children.

Passive and active floating torque during swimming.

The purpose of this study was to examine the effect of passive underwater torque on active body angle with the horizontal during front crawl swimming and to assess the effect of body size on passive torque and active body angle. Additionally, the effects of passive torque, body angle and hydrostatic lift on maximal sprinting performance were addressed. Ten boys [aged 11.7 (0.8) years] and 12 male adult [aged 21.4 (3.7) years] swimmers volunteered to participate. Their body angle with the horizontal was measured at maximal velocity, and at two submaximal velocities using an underwater video camera system. Passive torque and hydrostatic lift were measured during an underwater weighing procedure, and the center of mass and center of volume were determined. The results showed that passive torque correlated significantly with the body angle at a velocity 63% of v(max) ( alpha(63) r=-0.57), and that size-normalized passive torque correlated significantly with the alpha(63) and alpha(77) (77% of v(max)) with r=-0.59 and r=-0.54 respectively. Hydrostatic lift correlated with alpha(63) with r=-0.45. The negative correlation coefficients are suggested to be due to the adults having learned to overcome passive torque when swimming at submaximal velocities by correcting their body angle. It is concluded that at higher velocities the passive torque and hydrostatic lift do not influence body angle during swimming. At a velocity of 63% of v(max), hydrostatic lift and passive torque influences body angle. Passive torque and size-normalized passive torque increases with body size. When corrected for body size, hydrostatic lift and passive torque did not influence the maximal sprinting velocity.

Adults have lower stroke rate during submaximal front crawl swimming than children.

The aim of this study was to examine the effects of body size and propelling surface size on stroke rate (SR) and stroke length (SL) during front crawl swimming. Eleven children [11.7 (0.8) years] and 13 adults [21.4 (3.7) years] were compared. A third group of swimmers (n=5) had their propelling surface altered experimentally, swimming with hands only and using small- and large-sized paddles. Underwater videography was used to analyze four 25-m submaximal and four 25-m maximal swims for SR, SL, velocity (v) and hand slip. The results showed that adults have a lower SR at any submaximal v and a lower slope of the relationship between SR and workload (v(3)) compared to children. At 1.0 m s(-1) the SR values were 0.38 (0.04) and 0.58 (0.06) cycles s(-1) for adults and children respectively ( P<0.01). Adjusting for body size did not change this relationship [0.46 (0.05) and 0.67 (0.08) cycles s(-1) at a v of 1.0 bodylength s(-1) for adults and children respectively, P<0.001]. SL, adjusted for potential anatomical SL, was found to be longer in adults at submaximal velocities but not at maximal v. Hand slip was found to be lower for adults [-0.19 (0.14) and -0.36 (0.18) m for adults and children respectively, P<0.05]. Thirty per cent of the variations in slip could be attributed to propelling size. Increased propelling surface reduces SR and increases SL. It was concluded that adults have a lower SR both at absolute and size relative velocities compared to children; the causes could not be attributed to differences in body size, but probably the propelling size and swimming technique make the adults more effective swimmers.

Differences in the energy cost between children and adults during front crawl swimming.

There is little information available about the swimming economy of children. The aim of this study was to examine any possible differences in swimming economy in children and adults, swimming front crawl submaximally. Swimming economy was compared in adults [ n=13, aged 21.4 (3.7) years] and children [n=10, aged 11.8 (0.8) years] tested at four submaximal 6-min workloads. Oxygen consumption (VO2) was measured with Douglas bags in a 25-m pool and pacer lights were used to control the velocities. Swimming economy was scaled to body size using mass (BM), body surface area (BSA) and body length (BL). Children had lower VO2 (litres per minute) at a given velocity than the adults, with 1.86 (0.28) and 2.39 (0.20) l min(-1) respectively (at 1.00 m s(-1)). When scaling for size, children had higher VO2 measured in litres per square metre per minute and millilitres per kilogram per minute (divided by BSA and BM) than adults. The VO2 divided by BL was found not to differ between the two groups. The O2 cost of swimming 1 m at a velocity of 1.00 m s(-1) was lower in the children [31.0 (4.6) ml m(-1)] than in the adults [39.9 (3.3) ml m(-1) P<0.01], probably due to a lower total drag in the children. The results also showed that for children a relationship between swimming velocity cubed and VO2 exists as shown earlier for adults. It is concluded that, when scaling for BSA and BM, children are less economical than adults, when scaling for BL, children are equally economical, and when considering energy cost per metre and absolute VO2, children are more economical than the adults.