The influence of an 11-week resisted swim training program on the inter-arm coordination in front crawl swimmers.

The purpose was to assess the effect of an 11-week resisted swim training program using a water parachute on the inter-arm coordination in front crawl swimming. Fourteen female swimmers were divided into a control and an experimental group, and followed the same training program, except for the use of a water parachute by the experimental group in specific sprint sets. Before and after the intervention, the underwater motion of the swimmers was recorded using four camcorders and the digitisation process was undertaken manually. The two-way repeated measures analyses of variance revealed a significant increase of the swimming velocity, due to a significant increased stroke rate, because of the significant reduction of the total stroke duration, only in the experimental group. Moreover, their absolute and relative duration of the propulsive pull and push phases increased significantly, while the absolute and relative duration of their non-propulsive entry & catch and recovery phases decreased significantly. These modifications caused a significant increase in the index of coordination. Thus, this 11-week sprint resisted intervention program seems to improve the propulsion continuity and could be considered as an effective form of training, increasing the stroke rate and consequently the swimming velocity.

Transcranial magnetic stimulation implementation on stroke prognosis.

INTRODUCTION: Stroke represents a major cause of functional disability with increasing prevalence. Thus, it is imperative that stroke prognosis be both timely and valid. Up to today, several biomarkers have been investigated in an attempt to forecast stroke survivors' potential for motor recovery, transcranial magnetic stimulation (TMS) being among them. METHODS: A literature research of two databases (MEDLINE and Scopus) was conducted in order to trace all relevant studies published between 1990 and 2021 that focused on the potential utility of TMS implementation on stroke prognosis. Only full-text articles published in the English language were included. RESULTS: Thirty-nine articles have been traced and included in this review. DISCUSSION: Motor evoked potentials (MEPs) recording is indicative of a favorable prognosis concerning the motor recovery of upper and lower extremities' weakness, swallowing and speech difficulties, and the patient's general functional outcome. On the contrary, MEP absence is usually associated with poor prognosis. Relative correlations have also been made among other TMS variants (motor threshold, MEP amplitude, central motor conduction time) and the expected recovery rate. Overall, TMS represents a non-invasive, fast, safe, and reproducible prognostic tool poststroke that could resolve prognostic uncertainties in cases of stroke.

Enhancing Motor Competence and Physical Activity in Kindergarten.

BACKGROUND: This study aimed at evaluating the effect of the "Walk," an 8-month physical activity (PA) program led by classroom and physical education teachers, on the motor competence (MC) and PA of 5- to 6-year-old children. METHODS: A total of 143 children (mean age = 61.51 [1.85] mo) participated in the study and were randomly assigned to the experimental and control groups. Children's MC was assessed by the Körperkoordination Test für Kinder (KTK), and PA was objectively measured by Omron HJ-720IT-E2 pedometers. Measurements were performed at baseline, midintervention, and postintervention. A 1-sample t test computed at baseline step counts revealed that children presented significantly lower PA than recommended for their age (P < .001). To examine the effect of the intervention on children's MC and PA, several repeated-measures analyses of variance were utilized on (1) KTK item scores and (2) pedometer data. RESULTS: The results revealed that the Walk project led to practically significant changes in the experimental group compared with the control group in both MC (P < .001, η2 > .14 for all KTK items) and PA (P < .001, η2 = .23). CONCLUSIONS: This study highlights the efficacy of a PA project, involving both classroom and physical education teachers, for the enhancement of children's MC and PA.

Effect of an 11-Week In-Water Training Program With Increased Resistance on the Swimming Performance and the Basic Kinematic Characteristics of the Front Crawl Stroke.

Gourgoulis, V, Valkoumas, I, Boli, A, Aggeloussis, N, and Antoniou, P. Effect of an 11-week in-water training program with increased resistance on the swimming performance and the basic kinematic characteristics of the front crawl stroke. J Strength Cond Res 33(1): 95-103, 2019-The purpose of the study was to assess the effect of an 11-week in-water training program with increased resistance on the swimming performance and the basic kinematic characteristics of the front crawl stroke in young female swimmers. Twelve swimmers were matched in pairs according to their best performance in 50-m front crawl swimming and then were randomly assigned to an experimental or to a control group. Both groups followed exactly the same swimming training program. The only exception was that the experimental group performed a sprint training section with increased resistance pulling a water parachute, whereas the control group performed the same section without parachute. Before and after the intervention program, the best performance of both groups in 50-, 100-, and 200-m front crawl swimming were assessed. Moreover, the basic kinematic characteristics of the stroke were calculated during 50-m front crawl swimming with maximal intensity. Two-way repeated measures analyses of variance revealed significant improvement in the best performance in all swimming distances only in the experimental group (3.22-7.26%). As far as the basic kinematic characteristics of the stroke are concerned, significant modifications were found only in the mean swimming velocity in the experimental group (2.18%), whereas no significant changes were observed in the stroke length, the stroke rate, and the duration of the propulsive, and nonpropulsive phases in both groups. Thus, the findings of the current study revealed a positive effect of the in-water resistance training program in the swimming performance of young female swimmers of moderate performance level, without any negative influence in the basic kinematic characteristics of the stroke.

Reproducibility of gait kinematics and kinetics in chronic stroke patients.

BACKGROUND: The search for reliable techniques to assess gait in stroke patients is crucial for the design and follow-up of rehabilitation programs. OBJECTIVE: To assess the reproducibility of kinematic and kinetic gait parameters in chronic stroke patients using a three-dimensional gait analysis system. METHODS: Ten chronic stroke patients were assessed while walking along a 20 m walkway at their natural speed, using a gait analysis system of six infrared cameras and two force plates. Each patient performed 10 gait trials on 2 separate days. Inter-measurement agreement was assessed with the Coefficient of Multiple Correlation, while Root Mean Square Differences were used to quantify the variability of the trials. RESULTS: The majority of kinetics and kinematics showed excellent reproducibility in all patients. Joints' power seemed to be more reliable compared with joints' angle and moment. Most parameters presented greater variability in non-paretic than the paretic leg, while they were less variable in the sagittal compared with the non-sagittal planes. Less than 10 trials were sufficient to obtain excellent reproducibility for most kinematic and kinetic parameters. CONCLUSIONS: The reproducibility of movement assessment through three-dimensional gait analysis appears excellent in chronic stroke patients.

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.

The effect of leg kick on sprint front crawl swimming.

The aim of this study was to examine the influence of leg kick on the pattern, the orientation and the propulsive forces produced by the hand, the efficiency of the arm stroke, the trunk inclination, the inter-arm coordination and the intra-cyclic horizontal velocity variation of the hip in sprint front crawl swimming. Nine female swimmers swam two maximal trials of 25 m front crawl, with and without leg kick. Four camcorders were used to record the underwater movements. Using the legs, the mean swimming velocity increased significantly. On the contrary, the velocity and the orientation of the hand, the magnitude and the direction of the propulsive forces, as well as the Froude efficiency of the arm stroke were not modified. The hip intra-cyclic horizontal velocity variation was also not changed, while the index of coordination decreased significantly. A significant decrease (13%) was also observed in the inclination of the trunk. Thus, the positive effect of leg kick on the swimming speed, besides the obvious direct generation of propulsive forces from the legs, could probably be attributed to the reduction of the body's inclination, while the generation of the propulsive forces and the efficiency of the arm stroke seem not to be significantly affected.

Acute effect of front crawl sprint resisted swimming on the propulsive forces of the hand.

The purpose of the current study was to investigate the acute effect of sprint resisted front crawl swimming on the propulsive forces of the hand. Eight female swimmers swam 25 m with maximal intensity, with and without added resistance. A bowl with a capacity of 2.2, 4 and 6 L was used as low, moderate and high added resistance, respectively. The underwater motion of the swimmer's right hand was recorded using 4 cameras (60 Hz) and the digitization was undertaken using the Ariel Performance Analysis System. Repeated-measures ANOVA revealed that the velocity of the hand, the pitch and the sweepback angles of the hand, as well as the magnitude and the relative contribution of the drag and lift forces were not significantly modified and thus the magnitude of the resultant force did not change. Moreover, the magnitude of the effective force, as well as the angle formed between the resultant force and the axis of the swimming propulsion were not significantly affected. Thus, it could be concluded that resistance added as in this study did not alter the pattern of the propulsive hand forces associated with front crawl sprinting.

Kinematic characteristics of the stroke and orientation of the hand during front crawl resisted swimming.

The aim of this study was to examine the acute effect of front crawl sprint resisted swimming with different added resistances on the kinematic characteristics of the stroke and the orientation of the hand. Ten female swimmers swam four maximal trials (25 m) with small, moderate, large, and no added resistance respectively. Four camcorders were used to record the underwater motion of the right hand and digitizing was undertaken using the Ariel Performance Analysis System. Stroke rate, the stroke length, and mean swimming velocity were significantly decreased, whereas the total duration of the stroke and the relative duration of the pull and push phases were significantly increased during resisted swimming. The increase in the total duration of the stroke was accompanied by an increase in absolute pull length, while no alterations were observed in relative pull length or medial-lateral displacements of the hand. Moreover, the mean resultant velocity of the hand, as well as the pitch and the sweepback angles of the hand were not modified. In conclusion, resisted swimming appears to be a specific form of training, at least regarding its acute effect, although long-term effects should be investigated further.

The influence of hand paddles on the arm coordination in female front crawl swimmers.

The purpose of the research was to determine the influence of hand paddles on the arm coordination in female front crawl swimmers. Ten female swimmers swam at a maximal intensity 25 m without, with small hand paddles (116 cm), and with large hand paddles (286 cm). Four S-VHS cameras were used to record the underwater motion of both arms, and the digitizing of selected points onto the subject's body was undertaken using the Ariel Performance Analysis System. The mean swimming velocity, the stroke length, the stroke rate, the relative duration of the separate phases of the stroke, and the index of coordination were then calculated. The index of coordination was defined as the time interval between the propulsive phases of the 2 arms expressed as a percentage of the mean duration of the stroke cycle. The results showed that when the hand paddles were worn, the mean swimming velocity (p < 0.05) and the stroke length (p < 0.05) were significantly increased, whereas the stroke rate was significantly decreased (p < 0.05). When large paddles were worn, the relative duration of the whole propulsive phase was significantly decreased (p < 0.05), and the relative duration of the nonpropulsive phase was significantly increased (p < 0.05). However, the index of coordination was remained unchanged under the 3 measurement conditions (p = 0.895). It was concluded that in front crawl hand-paddled swimming, significant increases of the swimming velocity was not caused by modifications in the pattern of arm coordination. Thus, hand-paddled swimming should not be used as a tool to alter the time sequence of the application of propulsive forces generated from the 2 arms.

Unsuccessful vs. successful performance in snatch lifts: a kinematic approach.

The purpose of the present study was to determine the kinematic characteristics of snatch movements that result in an unsuccessful performance, involving the barbell's drop in front of the weightlifter. The sample comprised 7 high-level men weightlifters competing at the international level. Their successful and unsuccessful snatch lifts with the same load were recorded with 2 S-VHS camcorders (60 Hz), and selected points onto the body and the barbell were digitized manually using the Ariel Performance Analysis System. The statistical treatment of the data showed no significant differences (p > 0.05) between successful and unsuccessful lifts in the angular displacement and velocity data of the lower-limb joints, the trajectory and vertical linear velocity of the barbell, or the generated work and power output during the first and second pulls of the lift. Consequently, the general movement pattern of the limbs and the barbell was not modified in unsuccessful lifts in relation to the successful ones. However, significant differences (p < 0.05) were found in the direction of the barbell's resultant acceleration vector, suggesting that proper direction of force application onto the barbell is crucial for a successful performance in snatch lifts. Thus, coaches should pay particular attention to the applied force onto the barbell from the first pull.

Reconstruction accuracy in underwater three-dimensional kinematic analysis.

Accuracy of kinematic data is of decisive importance in motion analysis particularly when they are to be used for the calculation of kinetic parameters, like the propulsive forces in swimming. The present study investigated the accuracy of underwater three-dimensional (3-D) kinematic analysis using periscope systems and calibration volumes with different size. Two analogue cameras (60Hz) were used to record the images, along with two stationary periscope systems for the underwater recordings. The calibration of the recording space was performed using two different-sized calibration frames. The reconstruction accuracy was determined in static and dynamic conditions, both under water and out of the water. In static conditions, the reconstruction accuracy was determined by calculating the root mean square (RMS) error for the reconstruction of eight validation points on the calibration frames, and in dynamic conditions it was determined by the percentage of RMS error of the reconstructed length of a moving rod. The results revealed that in static conditions the RMS error was greater during underwater analysis, due to refraction, and it was increased particularly in the longitudinal axis as the dimensions of the calibration volume were increased. The reconstruction errors observed during underwater recordings with both calibration volumes (transverse axis, 1.61-2.35mm; longitudinal, 2.99-4.64mm; vertical, 2.83-2.59mm) may be considered suitable for three-dimensional kinematic analysis of swimming.

Estimation of hand forces and propelling efficiency during front crawl swimming with hand paddles.

The aim of the study was to investigate possible modifications caused by hand paddles in the relative contribution of the lift and drag forces of the hand and in the propelling efficiency, during front crawl swimming. Eight female swimmers swam 25 m with maximal intensity without paddles, with small (116 cm(2)) and with large paddles (268 cm(2)). Four cameras operating at 60 Hz were used to record the images and the Ariel Performance Analysis System was used for the digitisation. The results showed that, although during swimming with hand paddles the hand's velocity decreased, the greater propulsive area of the hand paddle caused an increase in the drag, lift, resultant and effective forces of the hand. However, the relative contribution of lift and drag forces on swimming propulsion was not modified, nor was the direction of the resultant force. Hand paddles also increased the propelling efficiency, the stroke length and the swimming velocity, mainly because of the larger propulsive areas of the hand in comparison with free swimming. However, the significant decrease of the stroke rate, might argue the effectiveness of hand paddle training, particularly when large paddles are used in front crawl swimming.

Validity and reliability of physical activity measures in greek high school age children.

The aim of this study was to determine the validity and reliability of 3 physical activity questionnaires in Greek high school children. Forty children participated in the study aged M = 13.73 (SD 0.8 years). The validation study was conducted by comparing an accelerometer (MTI/CSA Model 7164) to 3 questionnaires: a) Three-day Physical Activity Record (3DPAR), b) Four by One-Day Recall Physical Activity Questionnaire (4BY1RPAQ) and c) Physical Activity and Life Style Questionnaire (PALQ). Validity of the 3 self-report questionnaires was assessed against the MTI/CSA accelerometer by comparing the scores obtained by each instrument on the first week of measurement. Reliability was assessed with two consecutive measurements performed two weeks apart. The measures of reliability were assessed by Intra Class Correlation, Typical Error and Limits of Agreement. A two-way ANOVA for repeated measures was performed. Repeated measures were week and day; in order to determine differences between the two scores obtained with the two measurements for MTI/CSA, 3DPAR and 4BY1RPAQ. A paired Student's t-test was performed for the two scores obtained with the PALQ. Post-hoc multiple comparisons were performed using the Bonferroni test. Significance for all parts of the analysis was determined at an alpha level of p < 0.05. A paired Student's t-test was performed for the two scores obtained with the PALQ. Results of this study indicated that reliability measured by intra class correlations (ICC) were for MTI/CSA (ICC = 0.52, p < 0.05), 3DPAR (ICC = 0.97, p < 0.01), 4BY1RPAQ (ICC = 0.70, p < 0.01), and PALQ (ICC = 0.52, p < 0.01). Significant Pearson product moment correlation coefficients (r) were observed between MTI/CSA and the other instruments, as a measure of validity: 3DPAR (r = 0.63, p < 0.01), 4BY1RPAQ (r = 0.62, p < 0.01), and PALQ (r = 0.53, p < 0.01). The reliability of the four instruments used in this study was acceptable. Validity correlations were also significant for the three self-report instruments used in this study. Key PointsThe PALQ demonstrated a moderate reliability (0.52) and validity (0.53) in recording physical activity.A relatively high correlation was observed between the MTI/CSA and 3DPAR and a moderate correlation was observed between MTI/CSA and the 4BY1RPAQ tested in this study.Only a combination of the available instruments would be able to respond to the interpersonal and intrapersonal variability when assessing physical activity in children and adolescents. Self-report instruments and accelerometers are probably able to quantify only gross fluctuations in physical activity.All 4 instruments used in this study were valid and reliable in recording physical activity when used with children, since the instruments were able to detect changes in physical activity and the respective energy cost.