Changes in force production and stroke parameters of trained able-bodied and unilateral arm-amputee female swimmers during a 30 s tethered front-crawl swim

Abstract

This study examined changes in the propulsive force and stroke parameters of arm-amputee and able-bodied swimmers during tethered swimming. Eighteen well-trained female swimmers (nine unilateral arm amputees and nine able-bodied) were videotaped performing maximal-effort 30 s front-crawl swims, while attached to a load cell mounted on a pool wall. Tether force, stroke rate, stroke phase durations and inter-arm angle were quantified. The able-bodied group produced significantly higher mean and maximum tether forces than the amputee group. The mean of the intra-cyclic force peaks was very similar for both groups. Mean and maximum tether force had significant negative associations with 100 m swim time, for both groups. Both groups exhibited a similar fatigue index (relative decrease in tether force) during the test, but the amputees had a significantly greater stroke rate decline. A significant positive association between stroke rate decline and fatigue index was obtained for the able-bodied group only. Inter-arm angle and relative phase durations did not change significantly during the test for either group, except the recovery phase duration of the arm amputees, which decreased significantly. This study’s results can contribute to the development of a more evidence-based classification system for swimmers with a disability.     

How does buoyancy affect performance during a 200m maximum front crawl swim?

We investigated the rotational effect of buoyant force around the body’s transverse axis, termed buoyant torque, during a 200m front crawl maximal swim. Eleven male swimmers of national or international level participated. One stroke cycle (SC) for each 50m was recorded with two above and four below water cameras. The following variables were analysed: swimming velocity; absolute and normalised buoyant force; minimum, average and maximum buoyant torque; SC and arm recovery times. The average value of buoyant torque was higher in the first 50m (14.2 ± 4.5Nm) than in the following 150m (9.3 ± 4.1Nm~10.9 ± 4.5Nm) and was directed to raise the legs and lower the head throughout the race. The change in its magnitude seemed to be linked to the shorter time spent proportionally in arm recovery (first 50m: 27.6% of SC time; next 150m: 23.3–24.4% of SC time). Most swimmers had periods of the SC where buoyant torque was directed to sink the legs, which accounted to 10% of SC time in the first 50m and about twice this duration in the next 150m. These periods were observed exclusively at some instances when the recovering arm had entered the water while the opposite arm was still underwater.     

Changes in biomechanics and muscle activation in injured ballet dancers during a jump-land task with turnout (Sissonne Fermée)

Large impact loading with abnormal muscle activity and motion patterns may contribute to lower extremity injuries in ballet dancers. Yet, few studies investigated the influence of injury on the ballet movement. The purpose of this study was to find the neuromuscular and biomechanical characteristics in dancers with and without ankle injury during a jump-landing Sissonne Fermée task. Twenty-two ballet dancers were recruited and divided into the injured group (n = 11) and the uninjured group (n = 11). They performed a ballet movement called "Sissonne Fermée" with reflective markers and electrodes attached to their lower extremities. Ground reaction force, joint kinematics, and muscle activity were measured. The injured dancers had greater peak ankle eversion but smaller hindfoot-to-tibial eversion angles. Also, the injured dancers had greater activity of the hamstring of the dominant leg and tibialis anterior of the non-dominant leg during the pre-landing phase. The injured dancers had greater tibialis anterior activity of the dominant leg but less muscle activity in the medial gastrocnemius of the non-dominant leg during the post-landing phase. The injured dancers had a greater co-contraction index in the non-dominant ankle and a lower loading rate. The higher co-contraction indices showed that the injured dancers required more muscle effort to control ankle stability. Furthermore, the injured dancers used a "load avoidance strategy" to protect themselves from re-injury. Neuromuscular control training of the ankle joint for ballet dancers to prevent injury is necessary.     

Increased dietary carbohydrate and endurance during single‐leg cycling using a limb with normal muscle glycogen concentration

The purpose of this study was to test the hypothesis that increased availability of blood‐borne glucose would improve endurance after carbohydrate loading. A single‐leg exercise model was employed, taking advantage of the fact that supercompensation of muscle glycogen occurs only in a previously exercised limb. Endurance time to exhaustion at 70% of maximal oxygen uptake (VO₂max) was determined for 11 males and three females who were then allocated to a control group or a high‐carbohydrate (CHO) group. For 3 days following Test 1 the control group maintained a prescribed normal diet whilst the CHO group increased the proportion of energy derived from carbohydrate (62.1 ± 4.3% cf. 43.9 ± 2.0%, P < 0.01). The endurance test was then repeated using the leg that was inactive during Test 1. Endurance time was increased on Test 2 (123.7 ± 43.2 min cf. 98.5 ± 21.9 min, P <0.05 one‐tailed test) for the CHO group but not for the control group (101.8 ± 21.7 min cf. 107.5 ± 9.1 min, NS). There was no indication of enhanced carbohydrate metabolism during Test 2 for the CHO group but mean heart rate was lower during Test 2 than during Test 1 (145 ± 14 beat min ^‐1 cf. 152 ± 12 beat min ^‐1, P<0.05). These results suggest that the prior consumption of a high‐carbohydrate diet improves endurance during high‐intensity cycling with a limb with normal muscle glycogen concentration.     

Hand–arm strength and endurance as predictors of climbing performance

Abstract

The aims of this study were to examine training characteristics, body composition, muscular strength, and endurance in sport climbers, and to demonstrate the relationship among these components by means of structural equation modelling. Altogether, 205 sport climbers (136 males, 69 females), with a performance RP (red point) of grade 4 to 11 on the Union Internationale des Association d'Alpinisme (UIAA) scale, took part in the study. The proposed structural model, with latent variable hand–arm strength and endurance (developed from reference values for simple tests), indicated by three manifest variables (grip strength, bent-arm hang, and finger hang) and three exogenous variables (body fat, volume of climbing, and climbing experience), explained 97% of the variance in climbing performance. The relationship between body fat and climbing experience/volume with climbing performance was not direct, but was better explained using the mediator hand–arm strength and endurance. We conclude that these simple tests, together with percent body fat, volume of climbing, and climbing experience, can satisfactorily predict climbing performance.     

Skeletal maturation,fundamental motor skills and motor coordination in children 7–10 years

Relationships between skeletal maturation and fundamental motor skills and gross motor coordination were evaluated in 429 children (213 boys and 216 girls) 7–10 years. Skeletal age was assessed (Tanner-Whitehouse 2 method), and stature, body mass, motor coordination (Körperkoordinations Test für Kinder, KTK) and fundamental motor skills (Test of Gross Motor Development, TGMD-2) were measured. Relationships among chronological age, skeletal age (expressed as the standardised residual of skeletal age on chronological age) and body size and fundamental motor skills and motor coordination were analysed with hierarchical multiple regression. Standardised residual of skeletal age on chronological age interacting with stature and body mass explained a maximum of 7.0% of the variance in fundamental motor skills and motor coordination over that attributed to body size per se. Standardised residual of skeletal age on chronological age alone accounted for a maximum of 9.0% of variance in fundamental motor skills, and motor coordination over that attributed to body size per se and interactions between standardised residual of skeletal age on chronological age and body size. In conclusion, skeletal age alone or interacting with body size has a negligible influence on fundamental motor skills and motor coordination in children 7–10 years.     

Sport as a medium of national resistance: Politics and baseball in Taiwan during Japanese colonialism, 1895–1945

This paper examines the manner in which the Japanese colonial government influenced the development of baseball in Taiwan during the period from 1895 to 1945. The paper seeks to explain the role that baseball played in the divided society of this period. It argues that baseball was a political vehicle used by the Japanese colonial government to promote social integration and it evaluates the responses of the Taiwanese to baseball utilized for this purpose.     

Sports participation and health during periods of educational transition: a study of 30–35-year-olds in north-west England

In view of the persistence of health inequalities and declines in leisure-sport participation over the life course, several quantitative investigations have explored the links between participation and other leisure activities, which have their foundations in childhood and youth, as a means of understanding adults’ health behaviours. This paper presents new qualitative evidence to examine the largely under-explored relationship between leisure-sport participation and health within the context of educational transitions among a sample of 30–35-year-olds in north-west England. Drawing on semi-structured interviews conducted with 19 participants between July and August 2009, the paper illuminates the differential impact that gender and social class had on sports participation, and other health-related behaviours (e.g. drinking and smoking), among different groups of adults during the inherently transitional life-stage of youth. The findings suggest that while significant, the length of time spent in education and the differential educational experiences recalled by adults cannot adequately explain the observed differences in health and leisure-sport participation. The major sources of difference, while associated with educational transitions, appeared to lie instead in the broader inequalities that characterized adults’ lives and it is argued that simply enhancing leisure-sport participation and individual lifestyle change, as a means of health promotion, is a futile endeavour that does little to tackle the socio-economic structural determinants of health. We conclude by suggesting that until this is recognized by government and those both inside and outside of the health and sport policy communities, stubborn differences in leisure-sport participation rates and health inequalities—that have their foundations in childhood and youth, but extend over the life course—are likely to remain intact, and the unequal lives people currently lead are likely to become even more unequal in the future.     

Changes in selected cardiorespiratory responses to exercise and in body composition following a 12‐week aerobic dance programme

Cardiorespiratory and body composition changes were evaluated in 25 sedentary females, aged 18 to 30 years, following 12 weeks of aerobic dance training (3 days a week, 45 min a session). Fifteen subjects, from the same population, comprised a control group: they maintained their normal activity and dietary habits over the course of the study. Analysis of variance of the values for selected cardiorespiratory responses revealed that the aerobic dance programme produced training effects in the experimental group. These training effects were indicated by significant improvements in O₂ pulse, V _E, heart rate and perceived exertion during submaximal exercise. Significant improvements were also noted in VO₂ max, maximal O₂pulse, V _E max, maximal heart rate and maximal running time on the treadmill. Additionally, increases in lean body mass and body density, together with decreases in percentage body fat and the sum of four skinfold thicknesses were found to be significant for the experimental group. No significant improvements in any of these variables were found for the control group. It was concluded that this 12‐week aerobic dance programme was successful in promoting beneficial changes in cardiorespiratory fitness and body composition.     

Foot strike pattern in preschool children during running: sex and shod–unshod differences

Purpose: This study aims to determine the foot strike patterns (FSPs) and neutral support (no inversion [INV]/eversion [EVE] and no foot rotation) in preschool children, as well as to determine the influence of shod/unshod conditions and sex. Methods: A total of 1356 children aged 3–6 years (673 boys and 683 girls) participated in this study. A sagittal and frontal-plane video (240?Hz) was recorded using a high-speed camcorder to record the following variables: rearfoot strike (RFS), midfoot strike (MFS), forefoot strike (FFS), inversion/ eversion (INV/EVE) and foot rotation on initial contact. Results: There were no between-sex significant differences in both shod and unshod conditions in RFS. In the unshod condition, there was a significant reduction (p?Conclusion: In preschool children, no between-sex differences were found in relation to prevalence of RFS and neutral support (no INV/EVE). Shod running alters FSP of running barefoot, producing a significant increase of RFS prevalence.     

Dominant–non-dominant asymmetry of kicking a stationary and rolling ball in a futsal context

The aim of this study was to analyse the characteristics of the asymmetries in the dominant and non-dominant limbs when kicking stationary and rolling balls. Ten experienced Brazilian amateur futsal players participated in this study. Each participant performed kicks under two conditions (stationary ball vs. rolling ball) with the dominant and non-dominant limbs (five kicks per condition per limb). We analysed the kicking accuracy, ball and foot velocities, angular joint displacement and velocity. The asymmetry between the dominant and non-dominant limbs was analysed by symmetry index and two-way repeated measures ANOVA. The results did not reveal any interaction between the condition and limb for ball velocity, foot velocity and accuracy. However, kicking with the dominant limb in both kicks showed higher ball velocity (stationary ball: dominant – 24.27 ± 2.21 m · s^?1 and non-dominant – 21.62 ± 2.26 m · s^?1; rolling ball: dominant – 23.88 ± 2.71 m · s^?1 and non-dominant – 21.42 ± 2.25 m · s^?1), foot velocity (stationary ball: dominant – 17.61 ± 1.87 m · s^?1 and non-dominant – 15.58 ± 2.69 m · s^?1; rolling ball: dominant – 17.25 ± 2.26 m · s^?1 and non-dominant – 14.77 ± 2.35 m · s^?1) and accuracy (stationary ball: dominant – 1.17 ± 0.84 m and non-dominant – 1.56 ± 1.30 m; rolling ball: dominant – 1.31 ± 0.91 m and non-dominant – 1.97 ± 1.44 m). In addition, the angular joint adjustments were dependent on the limb in both kicks (the kicks with non-dominant limb showed lower hip external rotation than the kicks with the dominant limb), indicating that the hip joint is important in kick performance. In conclusion, the kicks with the non-dominant limb showed different angular adjustments in comparison to kicks with the dominant limb. In addition, kicking a rolling ball with the non-dominant limb showed higher asymmetry for accuracy, indicating that complex kicks are more asymmetric.     

‘Power in the arm,steel in the will and courage in the breast’ – a historical approach to ideal norms and men’s dominance in Swedish club sports

From both a quantitative and qualitative perspective, research shows that men and masculinities have dominated the Swedish sports movement for a long time and that sport as a so-called ‘democratic people’s movement’ has been criticised for being a male movement. Given the self-made claims of the Swedish Sports Confederation’s fostering of inclusivity and democratisation, this study encompasses a critical and historical perspective on the inclusive and exclusive dimensions of sport. The study object is a Swedish sports club and the specific aim is to analyse the prevailing norms and ideals and how they eventually helped to reproduce men’s domination in a local sports club. Chronologically, the paper uses a historical comparative approach studying the club’s 1910s–1920s and 1970s–1980s. The research questions put are: What characterised the norms of the ideal member and collective membership in terms of gender and did these change over time? Is it possible to find specific examples of inclusion and exclusion techniques by studying the club’s photographs and stories? The main result shows subtle and explicit power techniques that reproduced (some) men’s superior position at the club level.     

Changes in joint range of motion and muscle–tendon unit stiffness after varying amounts of dynamic stretching

The purpose of this study was to examine the effects of varying amounts of dynamic stretching (DS) on joint range of motion (ROM) and stiffness of the muscle–tendon unit (MTU). Fifteen healthy participants participated in four randomly ordered experimental trials, which involved one (DS1), four (DS4) and seven (DS7) sets of DS, or control conditions/seated at rest (CON). Each DS set consisted of 15 repetitions of an ankle dorsiflexion–plantarflexion movement. The displacement of the muscle–tendon junction (MTJ) was measured using ultrasonography while the ankle was passively dorsiflexed at 0.0174 rad · s^?1 to its maximal dorsiflexion angle. Passive torque was also measured using an isokinetic dynamometer. Ankle ROM was significantly increased after DS4 and DS7 compared with the pre-intervention values (P < 0.05), but there were no significant differences in ankle ROM between DS4 and DS7. No differences were observed in ankle ROM after DS1 and CON. In addition, the stiffness of the MTU, passive torque and displacement of the MTJ at submaximal dorsiflexion angles did not change in any of the experimental conditions. These results indicate that DS4 increased ankle ROM without changing the mechanical properties of the MTU, and that this increase in ankle ROM plateaued after DS4.     

Do oarsmen have asymmetries in the strength of their back and leg muscles?

The aim of this study was to establish whether asymmetry of the strength of the leg and trunk musculature is more prominent in rowers than in controls. Nineteen oarsmen and 20 male controls matched for age, height and body mass performed a series of isokinetic and isometric strength tests on an isokinetic dynamometer. These strength tests focused on the trunk and leg muscles. Comparisons of strength were made between and within groups for right and left symmetry patterns, hamstring :quadriceps ratios, and trunk flexor and extensor ratios. The results revealed no left and right asymmetries in either the knee extensor or flexor strength parameters (including both isometric and isokinetic measures). Knee extensor strength was significantly greater in the rowing population, but knee flexor strength was similar between the two groups. No difference was seen between the groups for the hamstring:quadriceps strength ratio. In the rowing population, stroke side had no influence on leg strength. No differences were observed in the isometric strength of the trunk flexors and extensors between groups, although EMG activity was significantly higher in the rowing population. Patterns of asymmetry of muscle activity were observed between the left and right erector spinae muscles during extension, which was significantly related to rowing side ( P < 0.01). These observations could be related to the high incidence of low back pain in oarsmen.     

Does whole body vibration training affect knee kinematics and neuromuscular control in healthy people?

Abstract

This study aimed to investigate the effect of whole body vibration (WBV) training on the knee kinematics and neuromuscular control after single-legged drop landings. Surface electromyographic (EMG) activity of the rectus femoris and hamstring muscles and knee and ankle accelerometry signals were acquired from 42 healthy volunteers. Participants performed three pre-test landings and after a recovery period of three minutes, they completed one set of six bouts of WBV each of one minute duration (30 Hz – 4 mm), followed by a single-leg drop landing. After the WBV intervention no significant changes were observed in the kinematic outcomes measured, although the time to stabilise the lower-limb was significantly lower after the vibration training (F(8,41) = 6.55; P < 0.01). EMG analysis showed no significant differences in the amplitude of rectus femoris or hamstring muscles after WBV training, however, significant differences in EMG frequency of the rectus femoris were found before (F(8,41) = 7.595; P < 0.01) and after toe-down (F(8,41) = 4.440; P < 0.001). Finally, no significant changes were observed in knee or ankle acceleration after WBV. Results suggest that WBV can help to acutely enhance knee neuromuscular control, which may have clinical significance and help in the design of rehabilitation programmes.     

Does performance level affect initial ball flight kinematics in finger and wrist-spin cricket bowlers?

Spin bowling plays a fundamental role within the game of cricket yet little is known about the initial ball kinematics in elite and pathway spin bowlers or their relationship to performance. Therefore, the purpose of this study was to record three-dimensional ball kinematics in a large and truly high level cohort of elite and pathway finger-spin (FS) and wrist-spin (WS) bowlers, identifying potential performance measures that can be subsequently used in future research. A 22-camera Vicon motion analysis system captured retro-reflective markers placed on the seam (static) and ball (dynamic) to quantify ball kinematics in 36 FS (12 elite and 24 pathway) and 20 WS (eight elite and 12 pathway) bowlers. Results indicated that FS bowlers delivered the ball with an increased axis of rotation elevation, while wrist-spin bowlers placed greater amounts of revolutions on the ball. It also highlighted that ball release (BR) velocity, revolutions and velocity/revolution index scores for both groups and seam stability for FS bowlers, and seam azimuth angle and spin axis elevation angle for WS bowlers, were discriminators of playing level. As such these variables could be used as indicators of performance (i.e. performance measures) in future research.     

Do expert swimmers have expert technique? Comment on "Arm coordination and performance level in the 400-m front crawl" by Schnitzler, Seifert, and Chollet (2011)

In a recent article by Schnitzler, Seifert, and Chollet (2011), they used an index of coordination (IdC) to quantify arm synchronization in swimming, which has become a practical standard to measure gaps (negative IdC) and overlaps (positive IdC) in arm propulsion. Their previous work supported an increase in IdC as swimming velocity and performance level increase, consistent with mechanics and physiology. Their recent study showed a lower IdC for expert swimmers than for recreational swimmers and concluded "catch-up coordination can be an efficient coordination mode. "In the hopes of preventing coaches and swimmers from using this finding to justify "catch-up stroke", other explanations are suggested.     

Vertical jumping and leg power normative data for English school children aged 10–15 years

Abstract

Although vertical jumping is often incorporated into physical activity tests for both adults and children, normative data for children and adolescents are lacking in the literature. The objectives of this study were to provide normative data of jump height and predicted peak leg power for males and females aged 10.0–15.9 years. Altogether, 1845 children from 12 state primary and secondary schools in the East of England participated in the study. Each child performed two countermovement jumps, and jump height was calculated using a NewTest jump mat. The highest jump was used for analysis and in the calculation of predicted peak power. Jump height and predicted peak leg power were significantly higher for males than females from the age of 11 years. Jump height and peak power increased significantly year on year for males. For females, jump height and predicted peak leg power reached a plateau after age 12 and 13 years respectively. This study provides normative data that can be used as a tool to classify jumping performance in children aged 10–15 years.     

Eccentric torque–velocity and power–velocity relationships in men and women

Abstract

The purpose of this study was to investigate the eccentric torque–velocity and power–velocity relationships of the elbow flexors. Forty recreationally trained individuals (20 men, 20 women) performed maximal eccentric actions at each of five different velocities (1.04 rad · s^?1, 2.09 rad · s^?1, 3.14 rad · s^?1, 4.18 rad · s^?1, and 5.23 rad · s^?1, in random order) and maximal isometric actions on a Biodex isokinetic dynamometer. A 2×6 (sex×velocity) mixed-factor repeated-measures analysis of variance (ANOVA) was used to assess peak elbow flexor torque during the eccentric and isometric actions. There was no interaction, but there were significant main effects for sex and velocity. Pairwise comparisons demonstrated that values for men were significantly (P<0.05) higher than those for women at all speeds. Furthermore, torques for both sexes were significantly less at 3.14 rad · s^?1 (men: 103.94±28.28 N · m; women: 49.24±11.69 N · m) than at 4.18 rad · s^?1 (men: 106.39±30.23 N · m; women: 52.77±11.31 N · m) and 5.23 rad · s^?1 (men: 108.75±28.59 N · m; women: 53.3±11.67 N · m), while isometric torque was significantly less than at all other speeds (men: 98.66±28.0 N · m; women: 45.25±11.15 N · m). A 2×5 (sex×velocity) mixed-factor repeated-measures ANOVA was used to assess peak eccentric elbow flexor power. There were significant main effects for sex and velocity. Pairwise comparisons demonstrated that values for men were significantly higher than those for women at all speeds. Pairwise comparisons for velocity indicated that peak eccentric power increased across all speeds from 1.04 rad · s^?1 (men: 110.44±32.56 W; women 54.36±13.05 W) to 5.23 rad · s^?1 (men: 569.46±149.73 W; women: 279.10±61.10 W). These results demonstrate that an increase in velocity had little or no effect on eccentric elbow flexor torque, while eccentric elbow flexor power increased significantly with increases in velocity.